Glossary of Standard Medical Terms

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Abduction: Movement of a part away from the midline, e.g. abduction at the shoulder moves the arm away from the trunk and out to the side. At the thumb, it describes movement of the digit forward from the anatomical position, away from the palm. This is because, in evolutionary terms, the thumb of the primitive hand lies in the same plane as the fingers and abduction carries it sideways away from the midline, just like the arm abducts at the shoulder. In man, the thumb has rotated from its atavistic position, through 90°, to allow human grasp.Adduction: Movement of a part towards the midline, e. g. adduction at the hip joint moves the leg toward the midline and adduction of both legs would press the knees together or cross the legs.

Allodynia: pain from stimuli that are not normally painful, or pain that occurs other than in the area stimulatedAlgodystrophy: See Reflex Sympathetic Dystrophy , Complex regional pain syndrome

Allograft: Graft of tissue from another individual of the same species, who is genetically different from the recipient. Bone is generally transplanted without revascularisation. Histocompatibility studies (tissue typing), essential in organ transplantation, are not necessary in bone allografting.

Anaerobic: Those metabolic processes which are not dependent on oxygen. Anaerobic organisms can therefore thrive in tissues which are hypoxic or anoxic.

Anastomosis: A junction between two vessels, or other tubular anatomical structures.Anatomical position: The reference position of the body - standing facing the observer, with the palms of the hands facing forward.

Anatomical reduction: the exact adaptation of fracture fragments (hairline adjustment) in preparation for surgical fixation. It will result in complete restoration of the normal anatomy. While overall stability does not necessarily depend on precise reduction, precise reduction more reliably results in stability and increased strength of fixation. It is more important in articular fractures than in diaphyseal fractures - see also Stability of fixation.

Angular stability: the property of an implant for fracture stabilisation, which is designed in such a way that the discreet parts of the implant, when assembled, are fixed in their angular relationship to each other. Usually applied to plates and screws, when the screw heads, once driven home in the plate hole, bind to the plate – this is achieved by an external thread on the screw head which engages with an internal thread in the plate hole. This principle was first described in 1935 by Rheinhold (France). See Locking Plate

Angulation: The orientation of one body (e.g. bone fragment) to another in such a manner that the two parts meet at an angle other than a straight line. The standard surgical convention is that the angulation is characterized by describing the deviation of the distal part from its anatomical position. For example, at a Colles’ fracture, the distal radial fragment is dorsally (or posteriorly) angulated, even though the apex of the deformity points anteriorly: similarly a tibial fracture whose apex of angulation points backwards, should be referred to as angulated anteriorly, as the distal part is indeed angulated anteriorly from its anatomical position. See Deformity

Ankylosis: Fusion of a joint by bone or a tight fibrous union, occurring as a result of a disease process, e.g. following septic arthritis (pyarthrosis), in ankylosing spondylitis, healed tuberculosis of bone etc.

Antalgic: Literally against pain. Used to describe an alteration of gait, where the stance phase one one side is abruptly shortened to avoid weight-bearing pain in that leg.

Anterior: The front aspect of the body in the anatomical position. If A is in front of B in the anatomical position, then A is said to be anterior to B.

Antibiotic: Any drug, such as penicillin, produced by certain fungi, bacteria, and other organisms, which can inhibit the growth of (bacteriostatic), or destroy (bactericidal), micro-organisms. They are used for the prevention, or treatment, of infections.

Antibody: A substance produced by the host’s immune system, in response to the detection of an antigen (q.v.). The antibody is specifically elaborated to attack and destroy only the antigen which stimulated its production – antigen specific.

Antigen: Component of a foreign biological substance (transplanted tissue, invading virus, etc.), which stimulates the host’s immune system to attack that foreign substance by elaborating an antibody (q.v.) that destroys the antigen and, in so doing, usually results in damage to the “invader”

Arthritis: Literally, an inflammatory condition of a diarthrodial (synovial) joint. It may be septic or aseptic. The former may be blood-borne infection (haematogenous), more common in children, or it may follow penetration of the joint by wounding or surgery. Aseptic arthritides are usually of the rheumatoid type (including Reiter’s syndrome, psoriatic arthropathy, etc.), or due to degenerative change (see Osteoarthritis. Rheumatoid arthritis).

Arthrodesis: Fusion of a joint by bone, as a planned outcome of a surgical procedure.

Articular fracture – partial: These fractures involve only part of the articular surface, while the rest of that surface remains attached to the diaphysis.

There are several varieties: pure split: A fracture, resulting from a shearing force, in which the direction of the split is usually longitudinal. pure depression: An articular fracture in which there is pure depression of the articular surface without a split. The depression may be central or peripheral. split-depression: A combination of a split and a depression, in which the joint fragments are usually separated. multifragmentary depression: A fracture in which part of the joint is depressed and the fragments are completely separated.

Articular Fracture – complete: The articular surface is disrupted and completely separated from the diaphysis. The severity of these fractures depends on whether their articular and metaphyseal components are simple or multifragmentary.

Atrophic nonunion: if a fracture fails to heal because the biological responses leading to bony union are frustrated, usually due to adverse biological status of the fracture locus, the nonunion is categorised as atrophic, with absence of callus, rounding off of the bone ends and finally the formation of a false joint, or pseudarthrosis. See Nonunion.

Autograft: Graft of tissue from one site to another within the same individual (homograft).

Avascular necrosis: Bone which has been deprived of its blood supply dies. In the absence of sepsis, this is called avascular necrosis (aseptic necrosis). The dead bone retains its normal strength until the natural process of revascularisation by “creeping substitution” (see Blood supply) starts to remove the dead bone, in preparation for the laying down of new bone. Loaded areas may then collapse – segmental collapse. This occurs in the femoral head and the talus more frequently than at other skeletal sites.

Avulsion: Pulling off.

Bactericidal: Capable of killing bacteria.

Biocompatibility: The ability to exist in harmony with, and not to injure, associated biological tissues or processes.

Biological (biologically respectful) internal fixation: In any internal fixation there is always a skilful balance to be struck between the degree of surgical stabilization produced and the biological insult caused by the necessary surgical intervention. The benefits of each will be judged by an experienced surgeon. Biological fixation utilizes a surgical exposure technique which favours the preservation of the blood supply, and thereby optimizes the healing potential, of the bone and soft tissues, whilst providing sufficient stability for multifragmentary fractures to heal in correct length and alignment. For the protection of the implants from mechanical failure (fatigue or loosening), it relies on a rapid biological healing reaction (early callus formation).

Biopsy: The surgical removal of a piece of tissue for histological or microbiological examination, usually undertaken to establish a diagnosis.

Blood supply to cortical bone (restoration of): Cortical bone which has been completely deprived of its blood supply for any extended period of time dies. It may become revascularised, either by ingrowth of blood vessels without marked widening of the Haversian canals (Pfister et al. 1979), or by newly formed Haversian canals, which result from the penetration of osteons. Such osteonal remodelling is a process with a marked lag period and a slow speed (0.1 mm/day according to Schenk 1987). When aseptic necrotic bone is revascularised by resorption and replacement with newly formed, vascular bone the term creeping substitution is often applied. See Vascularity and Avascular Necrosis

Bone Graft: Bone removed from one skeletal site and placed at another. Bone grafts are used to stimulate bone union and also to restore skeletal continuity where there has been bone loss – see Allograft, Autograft, Xenograft.

Broad Spectrum: Refers to antibiotics which are active against a wide spectrum of different organisms.

Butterfly fragment: Where there is a fracture complex with a third fragment which does not comprise a full cross section of the bone (i.e. after reduction there is some contact between the two main fragments), the small wedge-shaped fragment, which may be spiral, is occasionally referred to as a butterfly fragment – see Wedge fracture

Buttress: An implant applied in such a manner as to press against a fragment and prevent its axial displacement under compressive physiological load, maintaining its reduction “out to length”, is said to be functioning as a buttress. An example would be a contoured plate applied to the upper end of the tibia to prop up the surgically elevated main articular fragment of a tibial plateau fracture, thereby preventing its redisplacement into a position of depression. A buttress is defined by the Oxford English Dictionary as a structure of wood, stone, or brick, built against a wall to strengthen, or support it. Derived from the Fr. bo(u)terez – a thrusting arch. The flying buttresses of cathedrals are architectural examples.

Callus: Callus formation is the response of living bone to any irritation – chemical (Küntscher 1970), infective, mechanical instability (Hutzschenreuter et al. 1969), etc. Callus is a tissue complex formed at a site of bony repair. Fracture healing tissue makes a gradual and progressive transition through a series of tissue types – haematoma granulation tissue fibrous tissue (or fibro- cartilaginous tissue) remodelling into woven bone, gaining in stiffness as it does so. In internal fixation with anatomical reduction and absolute stability, where direct (callus-free) bone healing is expected, the appearance of callus is a sign of unexpected mechanical instability and should alert the surgeon to a failure of the original mechanical objective (formerly referred to as “irritation” callus). Callus is welcome as a repair tissue in all treatment methods where only relative fracture stability has been the planned goal.

Cancellous bone: Is the spongy trabecular bone (spongiosa)found mostly at the proximal and distal diaphyseal bone ends in contrast with the dense cortical bone of the shafts. Cancellous bone has a much larger surface area per unit volume and is, therefore, more readily available to the blood supply, as well as to osteoclasts for resorption. Its large surface/volume ratio also offers more surfaces for invading blood vessels when attempting to revascularise dead cancellous bone, and this is an advantage when cancellous bone is used for bone grafting.

Caudad: Literally “tailward”. If A is nearer to the “tail”, or coccyx, than B, then A is caudad of B.

Caudal: Pertaining to the tail, or tail region, e.g. caudal epidural injection

Causalgia: see Complex Regional Pain Syndrome

Cephalad: Literally “headward”. If A is nearer to the head than B, then A is cephalad of B.

Chemotherapy: Treatment of malignant lesions with drugs that impair, or stop, their cellular proliferation.

Chondral: Pertaining to cartilage. Consisting of cartilage.

Chondrocytes: The active cells of all cartilage, whether articular cartilage, growth cartilage, fibrocartilage, etc. They produce the chondral matrix, both its collagen and the mucopolysaccharides of the ground substance.

Cis-cortex: see Near cortex

Comminution; Comminuted: Refers to a fracture with multiple fragments, that is more than 2 main fragments. Syn. multifragmentary

Compartment syndrome: see Muscle Compartment

Complex fracture: Fracture in which, after reduction, there is no contact between the main fragments.

Complex Regional Pain Syndrome: Complex Regional Pain Syndrome (CRPS) is a disorder of unknown pathophysiology, which can affect either the upper or lower limbs. This disabling syndrome is not related to a single nerve territory and is disproportionate to the initiating event. The most prominent features include burning pain and functional impairment of the affected limb. Only 1 in 5 patients returns to a normal level of function. Categorised as types I and II; the clinical features of CRPS type I comprise regional pain, sensory change, allodynia, abnormalities of temperature regulation, abnormal sudomotor activity, oedema, and skin discolouration, accompanying noxious events. CRPS type II includes the aforementioned features, but in association with a peripheral nerve lesion. The incidence of CRPS is approximately 1 in 2000 traumatic events. Previously CRPS Type I was known as Reflex Sympathetic Dystrophy and CRPS type II was known as Causalgia. In order to establish a diagnosis of CRPS, 3 of the following 4 criteria must be present: An initiating, noxious event, or cause of immobilisation. Continuing pain, allodynia (pain from stimuli that are not normally painful, or pain that occurs other than in the area stimulated), or excess pain, disproportionate to the irritating event. Oedema, altered skin blood flow, or abnormal sweating in the region of the pain at some time. The diagnosis is excluded by absence of a condition to account for the degree of pain and dysfunction.

Compound fracture: The British school has long referred to fractures with an overlying, communicating wound of the integument as “compound” fractures, the opposite being “simple” fractures. No fracture should be regarded as simple, and the use of the archaic word “compound” does not convey the important clinical distinction. Now largely superseded by Open fracture.

Compression Screw: see Lag screw.

Compression: The act of pressing together. It can result in deformation (as in shortening a spring) and improvement in, or creation of, stability. Compression is used (1) to provide absolute stability of fracture fixation, where indicated, and (2) to protect the fixation implants and to improve their efficiency by reducing the dynamic stresses on them them. Unloading is achieved through restoration of the loadbearing capacity of the bone. Any fixation taking advantage of the loadbearing capacity of fracture fragments can withstand load without mechanical failure, or temporary micromotion, at the fracture. This is the main reason for using careful reduction and the application of compression. If the implant (screw, plate) bridging the fracture is applied under tension, then the fracture locus undergoes an equivalent amount of compression. The compression is used to help stabilize the fracture. Compression does not confer any “magic biological effect” on fracture healing – it merely provides the degree of absolute stability deemed necessary by the decision-making surgeon.

Contact healing: Occurs between two fragment ends of a fractured bone, at places which are maintained in motionless contact. The fracture is then repaired by direct osteonal remodelling. Contact healing may also be observed where the gap is only a few micrometers wide. See Direct healing

Continuous Passive Motion: see C.P.M.

Coronal: This is a vertical plane of the body passing from side to side, so that a coronal bisection of the body would cut it into a front half and a back half. It is so called because at a coronation, the crown (corona in Latin) is held with a hand on either side as it is lowered onto the royal head; the line joining these hands is in the “coronal” plane.

Cortex: see Cortical bone

Cortical bone: The dense bone forming the tubular element of the shaft, or diaphysis (middle part) of a long bone. The term cortex is also applied to the dense, thin shell covering the cancellous bone of the metaphysis. The two terms are generally used interchangeably.

Corticotomy: A special osteotomy where the cortex is surgically divided, but the medullary contents and the periosteum are not.

C.P.M. – Continuous Passive Motion: The use of powered apparatus to move a joint through a controlled range of motion has been shown to enhance articular cartilage healing after joint injury and to promoted soft tissue recovery after surgery. Salter, Mitchell & Sheperd, and others, have demonstrated that the use of passive motion machines for continuous periods is necessary for cartilage repair. The indiscriminate use of CPM machines for prolonged periods for other indications can lead to muscle wasting and should be combined with other techniques of physical therapy.

Creeping substitution: see Blood supply , Avascular necrosis

Cytoplasm: The non-nuclear substance of a cell.

Debricolage: A French term signifying the process of mechanical failure of an internal fixation prior to the onset of solid bone healing.

Débridement: Literally the “unbridling” of a wound. Strictly speaking, it refers to the extension of a wound and the opening up of the planes of the injured tissue, usually in the context of open fractures, as described by Amboise Paré in the 16th century. It has come to be used loosely to encompass the whole process of opening up of a wound, or pathological area (e.g. bone infection), together with the surgical excision of all avascular, contaminated, infected, or other undesirable tissue.

Deformity: Any abnormality of the form of a body part. The standard surgical convention is that the deformity is characterised by describing the deviation of the distal part from its anatomical position. Certain deformities have specific names – see Scoliosis, Recurvatum. etc,

Degenerative joint disease (DJD): see Osteoarthritis

Delayed union: The failure of a fracture to consolidate within the normally expected time, which varies according to age, fracture type and location. Delayed union, like union is a surgical judgment

Diaphysis: The cylindrical, or tubular, part between the ends of a long bone, often referred to as the shaft.

Direct healing: A type of fracture healing observed with absolutely stable (rigid) internal fixation. It is characterized by: Absence of callus formation specific to the fracture site. Absence of bone surface resorption at the fracture site. Direct bone formation, without any intermediate repair tissue.

Direct fracture healing was formerly called “primary” healing, a term avoided today in order not to imply any suggestion of grading of the quality of fracture healing. Two types of direct healing are distinguished, namely contact healing and gap healing.

Distal: Away from the centre of the body; more peripheral. For example, the hand is distal to the elbow, the phalanges are distal to the metacarpals. In certain instances, it means nearer the end than the beginning; for example, in the digestive system the stomach is distal to the oesophagus, or, in the urinary tract, the bladder is distal to the ureter.

Dorsal: Pertaining to the back or dorsum of the body in the anatomical position. An exception is the foot; the top of the foot, even though it faces forward in the anatomical position, is called the dorsum.

Ductility: The ability of a material to develop significant, permanent deformation before it breaks. See plastic deformation.

Dynamisation: The mechanical load transferred across a fracture locus can be increased, at a certain healing stage, in order to enhance bone formation, or to promote “maturation” of the healing tissues. An example would be the reduction in stiffness of an external fixation, either by loosening some clamps, reducing the number of pins, or moving the tubular construct further from the bone. Early dynamisation, i.e. before solid bridging of the bone, can result in stimulation of callus formation. The value of later dynamisation is debatable.

Elastic deformation: see Plastic deformation

Endosteal: The adjective derived from endosteum, which means the interior surface of a bone – i.e. the wall of the medullary cavity.

Energy Transfer: When tissues are traumatised, the damage is due to energy that is transferred to those tissues. This is most commonly due to the transfer of kinetic energy from a moving object (car, missile, falling object, etc.). The greater the amount of energy transferred to the tissue, the more extensive the damage.

Epiphysis: The end of a long bone that bears the articular component (joint). The epiphysis develops embryologically from the cartilaginous element between the joint surface and the growth plate – see Metaphysis.

Extension: The movement of an articulation that causes the relationship between part above the joint and the part below the joint to becomes straighter. An exception is „extension” of the foot at the ankle (so-called dorsiflexion); dorsiflexion is the better term, in this context/

Extensor: Adjective from the noun “extension”. The muscles which cause extension of a part are its extensor muscles; the surface of a part where those muscles are found is sometimes called the extensor surface.

Extra-articular fracture: Does not involve the articular surface, but it may be intracapsular (as in fracture of the femoral neck).

Far cortex (trans-cortex): The cortex more distant from the operator. In plating and tension band wiring, a bony defect has more important consequences in the far cortex than in the near cortex. This difference is due to the inability of a defective far cortex to resist compressive forces.

Fascio-cutaneous: A term describing tissue flaps that include, as a single layer, the skin, the subcutaneous tissues and the associated deep fascia.

Fasciotomy: The surgical division the investing fascial wall of an osseo-fascial muscle compartment, usually to release pathologically high intra-compartmental pressure – see Muscle compartment syndrome.

Fibrocartilage: Tissue consisting of elements of cartilage and of fibrous tissue. This may be a normal anatomical structure, such as certain intra-articular structures (menisci, triangular fibrocartilage at the wrist, or temporo-mandibular joint, or the symphysis pubis), or may constitute the repair tissue after lesions of the articular (hyaline)cartilage.

Fixation, flexible: Traditionally, internal fixation according to AO ASIF method meant absolutely stable (rigid) fixation, using close adaptation and compression of the bony fragments. Latterly, a less stable fixation (flexible fixation using splinting plates, intramedullary nails, or fixators) has been observed to yield very good results under conditions in which the fragments are well vascularized. Given best preservation of the viability of the fragments, flexible fixation induces abundant and rapid callus formation. Recall that the combination of instability and compromise of the biology of the fracture locus is deleterious. See Biological internal fixation

Flexion: The movement of an articulation that causes the relationship between part above the joint and the part below the joint to become more angulated.

Flexor: Adjective from the noun “flexion”. The muscles which cause flexion of a part are flexor muscles; the surface of a part where those rnuscles are found is sometimes called the flexor surface.

Floating Knee: Isolation of the knee joint from the remainder of the skeleton by fractures of the femur and the tibia in the same limb.

Fracture: A loss of continuity (breakage), usually sudden, of any structure resulting when internal stresses produced by load exceed the limits of its strength. The complexity and displacement of the fracture depend largely on the energy build-up in the structure prior to fracture. The shape of the fracture planes (transverse fracture, spiral fracture, avulsion, impaction etc.) is related to the nature of the load compressive, bending, torsional, shear, or any combination of these.

Fracture disease: A condition characterized by inappropriate pain, soft tissue swelling, patchy bone loss and joint stiffness (Lucas- Championnière 1907). Fracture disease can best be avoided by that system of fracture management most likely to produce skeletal integrity, whilst permitting early active motion of the part (early functional rehabilitation) (Allgöwer 1978).

Fracture locus (injury zone): Locus derives from the Latin word for “place”. It is used in yhis context to describe the biological unit comprising the fracture fragments and the immediately associated soft tissues, all of which function together to produce healing of the injury.

Fracture, articular: involves the articular surface. They are subdivided into partial and complete.

Fracture, extra-articular: These do not involve the articular surface, although they may be intracapsular. They include apophyseal and metaphyseal fractures.

Fracture, impacted: A stable, and usually simple, fracture of the metaphysis or epiphysis in which the fragments are driven one into the other, resulting often in inherent fracture stability.

Fracture, multifragmentary: A term used to characterize any fracture with one or more completely separated intermediate fragment(s). In the diaphyseal and metaphyseal segments, it includes the wedge and the complex fractures. The terms wedge and complex are used only for diaphyseal or metaphyseal fractures. Wedge: A fracture with one or more intermediate fragment(s) in which, after reduction, there issome contact between the main fragments. The spiral, or bending, wedge may be intact, or fragmented. Complex: A fracture with one or more intermediate fragment(s) in which, after reduction, there is no contact between the main proximal and distal fragments. The complex fractures are spiral, segmental or irregular. The term comminuted is imprecise and should not be used.

Fracture, simple: A term used to characterize a single circumferential disruption of a diaphysis or metaphysis or a single disruption of an articular surface. Simple fractures of the diaphysis or metaphysis are spiral, oblique or transverse.

Frontal: Pertaining to the front of the body in the anatomical position. That part of the skull forming the forehead is the frontal bone. The frontal plane of the body, parallel to the front, is the same as the coronal plane

Fusion: see Arthrodesis

Galeazzi injury: A fracture of the radial shaft associated with a dislocation of the inferior radio-ulnar joint. Its first description is attributed to Galeazzi (1934). Sometimes referred to as the “reversed Monteggia”

Gap healing: The healing process taking place between two fragment ends kept in stable relative position with a small gap between them. Gap healing progresses in two phases: (1) the filling of the gap with lamellar bone orientated parallel to the plane of the fracture gap, (2) the subsequent osteonal remodelling of the newly formed lamellar bone.

Gliding hole: When a fully threaded screw is used as a lag screw, the cortex under the screw head (near cortex, or cis-cortex) should not engage the screw threads. This can be accomplished by over-drilling the near cortex hole to at least the size of the outer diameter of the screw thread.

Gliding splint: A splint (such as an unlocked intramedullary nail) which allows for axial shortening. Such a splint provides the possibility for the re-establishment of bony coaptation under conditions of fragment end shortening due to bone surface resorption.

Goal of fracture treatment: According to Müller et al. (1963), the goal of fracture treatment is to restore optimal function of the limb in respect to mobility and load-bearing capacity. The goal is furthermore to prevent early complications, such as reflex sympathetic dystrophy, fracture disease, or Sudeck’s atrophy and, in the case of polytrauma, multiple system organ failure, as well as late sequelae, such as post- traumatic arthrosis.

Haematogenous: Blood-borne.

Haversian System: The cortical bone is composed of a system of small channels (osteons) about 0.1 mm in diameter. These channels contain the blood vessels and are remodelled after a disturbance of the blood supply to bone. There is a natural turnover of the Haversian systems by continuous osteonal remodelling; this process is part of the dynamic and metabolic nature of bone. It is also involved in the adaptation of bone to an altered mechanical environment.

Hawkin’s test: A test for subacromial impingement at the shoulder. With the arm in the throwing position and flexed forward about 30 degrees, passively internally rotate the humerus. Pain suggests impingement of the supraspinatus tendon against the coraco-acromial ligament. Crepitus can also often be detected at the subacromial bursa. For shoulder examination, see http: //www.usask.ca/cme/articles/fmse/index.php

Healing: Restoration of original integrity. The healing process after a bone fracture lasts many years, until internal fracture remodelling subsides. For practical purposes, however, healing is considered to be complete when the bone has regained its normal stiffness and strength.

Heterograft : see Allograft and Xenograft.

Homograft: see Allograft and Autograft

Horizontal: Parallel with the horizon: unrelated to the anatomical position.

Hypertrophic nonunion: if a fracture fails to heal, despite good fracture locus biology, due to a mechanical environment which is so unstable as to frustrate the tissue responses, the non-union is categorised as hypertrophic. Abundant new bone formation will often produce the so- called “elephant’s foot” appearance on x-ray. See Nonunion

Hypovolaemia: A state where the circulating blood volume is reduced. This can occur due to haemorrhage, or other loss of fluid, such as dehydration. It can lead to shock.

Hypoxia: A state where the oxygen level in the arterial blood, or in other tissue, is pathologically reduced.

Kinetic energy : see Energy transfer. The energy stored by a body by virtue of the fact that it is in motion. As energy cannot be destroyed, when a moving object is slowed or stopped, its kinetic energy is converted into other energy. If a moving object strikes a slower, or stationary object, it imparts some of its kinetic energy to the body that it strikes. This may accelerate the other body (or parts of it), causing damage, or produce other energy transfer effects such as heat production – the sparks seen when a metal bullet hits a rock, for example. Kinetic energy is calculated according to the formula E=½ mv2, where m is the mass of the moving object and v its velocity.

Kyphosis: Spinal deformity in which there is angulation forwards in the sagittal plane. Sharp angulation may result from abnormality of only one vertebral body, and is called an angular kyphosis, or gibbus (as after a severe wedge fracture, or tuberculous collapse of a vertebral body). A more gentle kyphosis is due to deformity involving several adjacent vertebrae, as in osteoporosis affecting the thoracic spine (“Dowager’s hump”)

Lag screw technique: Produces interfragmentary compression by driving the bone fragment beneath a screw head against another fragment in which the screw threads obtain purchase The compression produced by a screw so inserted acts directly within the fracture surface and is therefore very efficient. A screw designed specifically for this purpose, being only partially threaded is a lag screw, or shaft screw. A full threaded screw used with an over-sized hole in the near cortex to prevent thread purchase in the near fragment (a gliding hole) is strictly speaking not a lag screw but a threaded screw used with a lag technique; it is, nevertheless, often loosely termed a lag screw. Interfragmentary compression will be reduced by engagement of the screw threads with the walls of the gliding hole. Anchorage in the near fragment can be avoided by the use of a shaft screw. This technique is also required to maintain efficient compression when a screw is inserted through the plate and across a fracture plane in an inclined position.

Lateral: Literally, of, or toward, the side. The side of the body in the anatomical position is the lateral aspect or surface. If A is nearer the side of the body than B (further from the midline), then A is lateral to B. The opposite is medial.

Locking plate: A plate with threaded screw holes that allow mechanical coupling to a locking head screw. The AO Less Invasive Stabilisation System (LISS) will accept only this type of screw,. whilst AO Locking Compression Plates (LCP) have a combination hole that will accept normal screw heads or threaded screw heads. See Angular Stability

Locking head screw: Screws with external threads cut onto the head, which provide a mechanical couple to an internal thread in the screw hole of a plate, thus creating a fixed angle device.

Lymphoedema: Accumulation of oedema fluid in the tissues as a result of poor drainage of the lymph, usually due to the incompetence, or obstruction, of the lymphatic vessels.

Malunion: Consolidation of a fracture in a position of deformity.

Matrix: Literally, a place or medium in which something is bred, produced, or developed. In cartilage, it is the substance between the chondrocytes. It comprises a network of collagen fibres interspersed with a “jelly” of waterlogged mucopolysaccharide macromolecules (complex organic chemicals in large molecular chains).

Medial: Literally, of or toward the middle, or median. The inner side of a part with the body in the anatomical position is the medial aspect or surface. If A is nearer the middle, or centre-line, than B, then A is medial to B. The opposite is lateral.

Metaphysis: The segment of a long bone located between the articular end part (epiphysis) and the shaft (diaphysis). It consists mostly of cancellous bone, within a thin cortical shell.

Methylmethacrylate: A chemical substance, the monomer of which can be induced to polymerise, producing a hard plastic. It can be a form of bone cement (polymethylmethacrylate – or PMMA), but in a different polymerised form it produces Perspex.

Microvascular: Pertaining to microscopic blood vessels. Microvascular tissue transfer is related to the technical need for an operating microscope to perform the anastomoses (see Anastomosis).

Midline: The centre line of the body in the anatomical position.

Minimally invasive plate osteosynthesis (MIPO): reduction and plate fixation without direct surgical exposure of the fracture site, using small skin incisions and sub-muscular insertion of the plate.

Monteggia injury: A displaced ulnar fracture associated with a dislocation of the radial head from its articulation with the capitellum of the humerus, at the elbow. First described in the 19th century by the Italian physician Giovanni Battista Monteggia.

Multifragmentary fracture: A term usually reserved for fractures which have one or more dissociated intermediate fragments.

Muscle Compartment: An anatomical space, bounded on all sides by bone and/or deep fascial envelope, which contains one or more muscle bellies. The relative inelasticity of its walls means that if the muscle tissue swells, the pressure in the osseo-fascial envelope can increase to levels which cut off the flow of blood to the muscle tissue, resulting in its severe compromise or death – so-called Muscle Compartment Syndrome.

Muscle Compartment Syndrome.
Diagnosis

“In the conscious patient, the earliest and most important symptom is of a burning, boring pain of acute onset which may be spasmodic in nature and tends to increase with time. Sensory aberrations are also reported in the form of paraesthesiae, hypoaesthesiae, and rapid sensory losses. In co-operative patients, disturbances of muscular function are demonstrable as motor weakness after two to four hours of ischemia. On palpation, the affected muscles are tender and have a firm to stony-hard consistency. Peripheral arterial pulses and capillary perfusion are intact in the early stage, provided there is not concomitant arterial injury”.

They then describe, as do most modern texts, techniques for direct measurement of compartment pressure in cases where there may be some doubt as to the diagnosis.

In “Skeletal Trauma” , edited by Browner, Jupiter, Levine and Trafton (1992) Rorabeck states: “Assuming the patient is conscious and alert, the most important symptom of an impending compartment syndrome is pain disproportionate to what might be expected given the problem the patient is being treated for. Frequently the patient presents with a relatively pain-free interval, perhaps a few hours following reduction of the fracture, and then develops pain out of proportion to the problem. The degree of pain can usually be assessed by the requirements for analgesia, or even stronger analgesia. The pain felt by the patient is unrelenting and seems to be unrelated to the position of the extremity or to immobilization. The patient might also complain of feelings of numbness or tingling in the affected extremity. These symptoms are poorly localized and are not to be relied on. Clinical signs of an impending acute compartment syndrome, irrespective of the underlying cause, include pain on palpation of the swollen compartment, reproduction of symptoms with passive muscle stretch, sensory deficit in the territory of the nerve traversing the compartment and muscle weakness. The earliest sign of an acute compartment syndrome is a tensely swollen compartment, which on palpation reproduces the patient’s pain”.

Treatment by fasciotomy: It is not always possible at fasciotomy to determine exactly which muscle has died and which has not, although this is usually evident when the muscles are reviewed 24 to 48 hours later.

According to Tscherne and Gotzen (1984): “Decompressive fasciotomy is an emergency procedure, and facilities for this operation should be available at all times. Promptness has a critical bearing on the prognosis. According to McQuillen and Nolan (1968) and Matsen and Clawson (1975), disturbances of muscular microcirculation that persist longer than 12 hours produce significant motor and sensory deficits as well as myogenic contractures. Keays (1981) states that, based on his experience, good results are obtained only if decompression is performed within 6 hours of the onset of compartment syndrome. He further states that permanent defects may be expected after 8 hours, and that amputation will very likely be needed if surgery is delayed beyond 12 hours. Of his ten patients treated by fibulectomy, only four had a good end result.

Most findings on the temporal relationship between circulatory impairment and reparative tissue tolerance are based on experimental total ischemia. Nerves showed functional deficits after only 30 minutes ischemia. Irreversible pareses developed after 12 – 24 hours of complete ischemia (Holmes et al. 1944, Malam 1963). Compensatable partial myogenic disturbances were observed after only 2 – 4 hours ischemia, and an irreversible loss of function after 4 – 12 hours (Harman 1948, Whitesides 1971). These findings are consistent with our own clinical observation that permanent functional deficits arise within 4 – 6 hours of the onset of a frank, untreated compartment syndrome” .

This publication also quotes work of Oestern and Echtermeyer (1982), who reviewed 123 compartment syndromes, including late referrals. They reported: “Late sequelae developed in 36 patients, 35 of whom had a compartment syndrome of the lower leg. Twenty-nine displayed weak dorsiflexion of the foot, four had a claw-toe deformity and nine complained of sensory losses.

Analysing the sequelae that occurred after fasciotomy, we find that late changes developed in only three patients who underwent a fasciotomy within the first six hours after their injury. By contrast, late changes occurred in twenty-two patients in whom decompression was delayed beyond twenty-four hours. Ten patients eventually had to undergo an amputation; in none of these cases had a decompressive fasciotomy been performed within the first six hours (1 within the first 12 hours, 2 between 12 and 24 hours and 7 more than 24 hours post-injury)”.

The results of Oestern and Echtermeyer (1982) suggest, decompression of the muscle compartments within six hours of the clinical onset of the compartment syndrome, would be likely to result in no late sequelae.

The dead and disintegrating muscle cells can release the muscle pigment myoglobin into the surrounding tissue fluid and this can then reach the blood circulation, especially after release of the raised intra-compartmental pressure. This may cause the presence of myoglobin in the urine (myoglobinuria), this being an indication of extensive muscle death. Frank myoglobinuria may be expected to start within a few hours of the restoration of the muscle circulation by fasciotomy.

Near cortex: The bony cortex near the operator and on the side of application of an implant. Usually a term used in relation to plating, interfragmentary screw fixation and tension band wiring. In respect to bending, the convex near cortex contributes little to stability of fixation. When – for example, in wave plate application – the distance between the plate and the near cortex is increased, the bone and the repair tissues gain better leverage.

Neutralization: An implant (plate, external fixator, or nail) which functions by virtue of its stiffness. The stiffness is said to “neutralize” the effect of the functional load. The implant carries a major part of the functional load and thus diverts loads away from the fracture locus and may serve to protect a more vulnerable element of a fixation complex. An example is where a spiral fracture has been reduced and fixed with interfragmentary screws, and then a plate is applied to protect the primary screw fixation from functional loads which could disrupt it. The use of such a protection, or “neutralization”, plate will allow earlier function aftercare than had the screw fixation been left unsupported. It does not actually “neutralize”, but does minimize, the effect of the forces (see Protection).

Non-steroidal inflammatory drugs: see NSAIDS

Nonunion (or non-union): (see also Union, Pseudarthrosis, Delayed Union) Nonunion is failure of bone healing. A fracture is judged to be ununited if the signs of nonunion are present when a sufficient time has elapsed since injury, during which the particular fracture would normally be expected to have healed by bony union. That period will vary according to age, fracture location and patho-anatomy. The signs ofnonunion include persisting pain and/or tenderness at the fracture sight, pain and/or mobility on stressing the fracture site, and inability progressively to resume function. Slight warmth may be detected if the fracture site is subcutaneous. Radiographs will be likely to show failure of re-establishment of bony continuity. When a fracture has been fixed internally, loosening and/or breakage of the implant may indicate the instability of a nonunion. If a nonunion has resulted from a mechanical environment at the fracture locus that is not conducive to bone healing, despite good fracture biology and osteogenic response, a hypertrophic nonunion (“elephant’s foot”) occurs – the solution to this is a mechanical one. If a nonunion has resulted from impaired biological response at the fracture locus, an atrophic nonunion occurs – the solution to this is biological enhancement, usually with mechanical support.

NSAIDS: non-steroidal inflammatory drugs. See http: //www.healthline.com/galecontent/nonsteroidal-anti-inflammatory-drugs-1

Open Fracture: Fractures with an overlying, communicating wound of the integument, exposing the fracture site to contamination and the risk of infection. Open fractures are commonly graded according to the severity scale of Gustilo, Mendoza and Williams (J.Trauma 1984) This scale comprises grades 1, 2, 3A, 3B & 3C, from the least to the most severe soft tissue damage.

Opposition (anatomical): The action of opposing one part to another; if the pulp of the thumb is placed in contact with the pulp of a finger, the movement, or action, of the thumb is that of opposition.

ORIF: A widely used abbreviation for open reduction and internal fixation (osteosynthesis).

Osteoarthritis: This is a degenerative condition which affects diarthrodial (synovial) joints and is characterized by loss of articular cartilage, reactive subchondral bone sclerosis (sometimes with subchondral cysts) and the formation of peripheral bony outgrowths - osteophytes. The primary lesion is degeneration of the articular cartilage as a result of infection, trauma, overuse, congenital skeletal anomaly, or as part of the aging process .

Osteoarthritis may be primary, where there is no identifiable prior insult to the articular cartilage (usually associated with the aging process), or secondary, in which case the degeneration of the articular cartilage is initiated by congenital joint abnormality, injury, infection, deformity of the limb, joint instability, identifiable overuse, inflammatory joint disease, such as “burnt out” rheumatoid arthritis, etc.

Osteoarthrosis: see Osteoarthritis

Osteoblast: A cell that forms new bone

Osteoblastic: Producing bone.

Osteoclast: Cell that destroys bone. Osteoclasts rest in the Howship lacunae (small spaces within the bone surface). They are typically found at the tips of the remodelling osteons, but also in all sites where bone is being removed by physiological processes.

Osteolytic: Resorbing, destroying or removing bone.

Osteomyelitis: An acute or chronic inflammatory condition affecting bone and its medullary cavity, usually the result of bacterial (occasionally viral) infection of bone. This may be a blood-borne infection (haematogenous osteomyelitis) – usually in children or in the immunologically compromised – or follow an open fracture (post-traumatic osteomyelitis). The acute form, if diagnosed early and treated vigorously, can heal with no residual effects. If the diagnosis is delayed then the infection and the consequent interference with the local bone blood supply, can result in dead bone (which may separate to form one or more sequestra - see Sequestrum) that remain infected in the long term because the defence mechanisms have no vascular access to it. The treatment of chronic osteomyelitis is surgical and includes wide excision of all dead and infected tissue, the identification of the responsible organism, and the delivery, both locally and systemically, of appropriate anti-bacterial agents.

Osteon (osteone)(cutter cone): This is a normal vascular structure concerned with bone remodelling, either as part of physiological bone turnover, or as part of the healing process after fracture. Anosteon comprises a vascular bud, at the tip of which is a cluster of osteoclasts. Behind the osteoclasts, the vessel is cuffed by osteoblasts. As the osteoclasts removed bone, they advance through the bone and the following cuff of osteoblastslays down concentric cylinders of osteoid, that matures to form the rings of bone seen in the walls of the Haversian systems of bone. The osten effectively drills a new channel through existing bone, then lines this channel with cylinders of new bone.

Osteopaenia (osteopenia): An abnormal reduction in bone mass. This may be generalized, as in some bone diseases, or localized, as a response to inflammation, infection, disuse, etc. See Osteoporosis

Osteoporosis: A reduction in bone mass. It is a natural aging process but may be pathological. It can result in pathological fracture (most fractures of the femoral neck in the elderly are due to osteoporosis plus minimal trauma). See Osteopaenia and Pathological fracture.

Osteosynthesis: A term coined by Albin Lambotte (1907) to describe the “synthesis” (derived from the Greek suntithenai for putting together, or fusing) of a fractured bone by a surgical intervention using implanted material. It differs from “internal fixation” in that it also includes external fixation

Osteotomy: Controlled surgical division of a bone.

Overbending (of plate): See Prebending.

Palmar: Pertaining to the palm of the hand, e. g. the palmar fascia, the palmar aspect of the fingers.

Pathological fracture: A fracture through bone which is abnormal as a result of a pathological process. It may be the result of the application of a force less than that which would be required to produce a fracture in a corresponding normal bone.

Periosteal: Adjective derived from periosteum.

Periosteum: The inelastic membrane bounding the exterior surface of a bone. The periosteum plays an active part in the blood supply to cortical bone, in fracture repair and in bone remodeling. It is continuous with the perichondrium – the membrane that bounds the periphery of the physis.

Pilon: The distal end of the tibia – from the French for a stump, or a pestle. Fractures of the distal tibial metaphysic caused by axial load failure are called “pilon fractures”

Pilot hole: If a fully threaded screw is to function as a lag screw, the screw is anchored near its tip, within a threaded hole in the far bone fragment. The original drill hole which is made prior to tapping of the thread in the bone is called the pilot hole. Within the bone fragment near the head of the screw, the thread should not obtain purchase but should glide (gliding hole). A pilot hole is also prepared when inserting a Schanz screw, or a Steinmann pin.

Pin loosening: The pins of external fixator frames serve to stabilize the fragments of a fracture by linking the bone to the frame. Stability depends, among other things, upon the contact between pin and bone (pin-bone interface). Pin loosening occurs when bone surface resorption at the pin-bone interface takes place due to excessive cyclical loading of the bone. Stability is thereby reduced. However, pin loosening is less important in respect of loss of stability than in respect of its deleterious effect in promoting pin track infection.

Plafond (Fr.): Literally “ceiling”: used to denote the horizontal portion of tge distal tibial articular surface. See Pilon

Plantar: Pertaining to the sole of the foot, i.e., the surface of the foot which is “planted” on the ground. Examples are the plantar fascia, and the plantar surfaces of the toes. Plantar flexion is a movement at the ankle which moves the foot downward, or in a plantar direction.

Plastic Deformation: If an object is deformed within those limits which allow it to regain its original form, once the deforming force is removed, it is said to have undergone elastic deformation. If the force is increased above the upper level for elastic deformation, permanent deformity (known in engineering terms as “set”) is produced – this is plastic deformation. When the deforming force is removed, the object cannot return to its original form.

Plastic deformation, without fracture, can occur in the shape of a young, growing bone following the application of a deforming force. The alteration in shape does not “rebound” to the original as the bone has been stressed beyond its elastic limit, but not to the point of breaking.

Polytrauma: Multiple injuries to one or more body systems. An Injury Severity Score (ISS) of more than 16 is usually taken to indicate polytrauma.

Posterior: The back of the body in the anatomical position is the posterior surface. If A is nearer to the back of the body in the anatomical position than B, then A is posterior to B. Equivalent to dorsal, except in the foot, where the dorsum is anterior in the anatomical position - see Dorsal

Prebending of plate: Exactly contoured plates, when loaded using either the external compression device or the DCP principle, produce asymmetrical compression, i.e. the near cortex is more compressed than the far cortex. Indeed, the latter may not be compressed at all and can be distracted in certain cases. To achieve stabilization against both torque and bending, compression at the far cortex is even more important than that of the near cortex. To provide uniform compression across the whole width of the bone, including the far cortex, the plate is applied after contouring with an additional bend of the plate segment bridging the fracture. The bend is such that the midsection of the plate is slightly elevated from the surface of the reduced fracture, prior to fixation to the bone and the application of compression. Prebending is an important tool to increase stability in small and/or osteoporotic bones – see osteopaenia.

Precise reduction: see Anatomical reduction

Preload: The application of interfragmentary compression keeps the fragments together until a tensile force is applied, exceeding the compression (preload).

Pronation: The movement of rotating the forearm so that the palm of the hand faces backward from the anatomical position. Pronation is also sometimes used to describe a movement of the foot into inclination away from the midline, otherwise called eversion; so that a pronated foot would bear more weight on its medial border than onits lateral border

Prophylactic: Preventive.

Protection: While the term “neutralization” has often been used in plate and screw fixation, the term “protection” should replace it. In reality nothing is neutralized. In plate fixation the plate reduces the load placed upon the interfragmentary screw fixation. It therefore protects the screw fixation from overload – see Neutralization.

Proximal: Nearer to the centre of the body in the anatomical position. The opposite of distal. Thus, the elbow is proximal to the wrist. In certain instances, it means nearer the beginning than the end; for example, in the digestive system the stomach is proximal to the ileum, or in the urinary tract the kidney is proximal to the bladder.

Pseudarthrosis: (see also Delayed Union, Nonunion, Union) literally means “false joint”. When a nonunion is mobile and allowed to persist for long periods, the ununited bone ends become sclerotic and the intervening soft tissues differentiate to form a crude sort of synovial articulation. The term is often loosely and incorrectly used to describe all nonunions. Occasionally, a pseudarthrosis (in the sense of a false articulation) may be deliberately created surgically, as for example, in excision arthroplasty of the hip (Girdlestone, Judet, Robert Jones), or excision of a segment of the distal ulnar shaft, in combination with fusion of the inferior radio-ulnar joint (Kapandji). Excision of the radial head is another example of surgical pseudarthrosis.

Pure depression: An articular fracture in which there is depression alone of the articular surface without split – see Impacted fracture and Pure split.

Pure split: An articular fracture in which there is a longitudinal metaphyseal and articular split, without any additional osteochondral lesion.

Radial preload: To prevent external fixator pin loosening, the contact zone (interface) between the implant and bone can be preloaded, i.e. a static compressive force is applied. Hitherto, preloading was achieved by applying a permanent bending moment to the pins, within their elastic range. Currently, the pins are designed with a thread and shank that automatically generate radial preload, i.e. a tight, compressive fit produced by insertion of a pin slightly larger than the drill hole. The effect of radial preload is to minimize pin loosening and to seal the pin track so that a potential infection cannot reach the medullary cavity from outside. The amount of misfit between the hole diameter and the pin diameter should not exceed 0.050.1 mm. Such a precise geometric discrepancy can only reliably be ensured by using selfcutting tips. See Preload

Radiotherapy: Treatment of pathological conditions, usually malignant, with ionizing radiation. It has been recommended in low dosage to discourage heterotopic bone formation.

Recurvatum: an angular deformity , usually of a long bone, in which the distal part is angulated anteriorly, so that the apex of the angle is posterior.

Reduction: The realignment of a displaced fracture or a dislocated joint.

Reflex Sympathetic Dystrophy (RSD): one of the names given to Algodystrophy. One of the chronic regional pain syndromes. Usually follows an injury, not always a fracture. Characterised by chronic pain that fails to resolve within the time commensurate with the injury, swelling of the part, joint stiffness, alteration in skin colour, texture and/or temperature and associated with demineralization of the local bone, especially in the bone just beneath the articular cartilage (subchondral bone). See Complex Regional Pain Syndrome

Refracture: A fracture occurring at a former fracture site, after the bone has solidly bridged, at a load level otherwise tolerated by normal bone. The resulting fracture line may coincide with the original fracture line, or it may be located remote from the original fracture, but within the area of bone that has undergone changes as a result of the fracture and its treatment.

Relative Stability: see Stability of fixation

Remodelling (of bone): The process of transformation of external bone shape (external remodelling), or of internal bone structure (internal remodelling, or remodelling of the Haversian system).

Resorption (of bone): The process of bone removal includes the dissolution of mineral and matrix and their uptake into the cell (phagocytosis). The cells responsible for this process are osteoclasts.

Rheumatoid arthritis: a crippling, aseptic, synovial inflammatory disease, usually involving many joints (polyarthritis). Results in an intense synovitis that eventually erodes the articular cartilage and the underlying subchondral (beneath the cartilage) bone.

Rigid fixation: A fixation of a fracture which allows little or no deformation under load – see Stability of fixation.

Rigid implants: In general implants are considered to be rigid when they are made of metals. The implant geometry is more important than the physical stiffness of the material. Most implants made of metal are much more flexible (less rigid) than the corresponding bone.

Rigidity: This term is often used synonymously with stiffness. Some (Timoshenko 1941) feel that its use should be confined to considerations of shear (e.g. at the interface of plate and bone).

Rotator cuff: A musculo-tendinous “hood”, or cuff, comprising the muscle bellies and the aponeurotic tendons of the supraspinatus, infraspinatus and subscapularis muscles, passing from their origins from the scapula to their insertions into the tuberosities of the upper humerus. This sheet of tendinous tissue lies between the head of the humerus and the undersurface of the acromio-clavicular arch – in the sub- acromial interval. These muscle play an important role in controlled shoulder movement and in stabilising the shoulder. A rupture of the rotator cuff allows the head of the humerus to migrate upward and come into abnormal articulation with the undersurface of the acromio- clavicular arch, resulting in later degenerative change.

Sagittal: Literally, it means pertaining to an arrow (sagitta is Latin word for arrow). Bisection of the body in the sagittal plane would divide it into left and right halves, so-called because an arrow fired into the body would normally strike from the front and would pass in a sagittal direction.

Scarf test: A test for acromio-clavicular dysfunction: the patient experiences pain in the acromio-clavicular joint when bringing the forward flexed arm across the front of their body, as if to “toss a scarf” over the opposite shoulder (this movement is called horizontal adduction)

Scoliosis: a spinal deformity in which there is one, or more, curvature in the coronal plane – may be postural or structural. The latter is often associated with rotational deformity. See also Kyphosis.

Second look: Surgical inspection of a wound or injury zone, 24 to 72 hours after the initial management of a fracture or wound.

Segmental: If the shaft of a bone is broken at 2 levels, leaving a separate shaft segment between the two fracture sites, it is called a “segmental” fracture complex.

Sequestrum: A piece of dead bone lying alongside, but separated from, the osseous bed whence it came. It is formed when a section of bone is deprived of its blood supply and the natural processes create a cleavage between the dead and the living bone. A sequestrum may be aseptic (sterile), as for example beneath a plate when there has been massive periosteal stripping and then a plate with a high contact “footprint” applied, killing the underlying bone. This is especially seen if a plate has been applied to the cortex at the same time that a reamed intramedullary nail has been inserted. Infected sequestra are formed in chronic osteomyelitis – see Osteomyelitis.

Shear: A shearing force is one which tends to cause one segment of a body to slide upon another, as opposed to tensile forces, which tend to elongate, or shorten, a body.

Shock: A state of reduced tissue perfusion, usually due to a fall in blood pressure secondary to hypovolaemia, overwhelming sepsis (gram negative shock, or “red” shock), or allergic anaphylaxis

Shoulder examination: see http: //www.usask.ca/cme/articles/fmse/index.php

Simple (single) fracture: A disruption of bone with only two main fragments. Formerly used to denote a fracture that was not “compound” (or open)

Splinting: Reducing the mobility at a fracture locus by coupling a stiff body to the main bone fragments. The splint may be external (plaster, external fixators) or internal (plate, intramedullary nail).

Split depression: A combination of split and depression in an articular fracture – see Pure split and Pure depression.

Spondylolisthesis: The forward slip of one vertebral body on the one below it. This may be due to congenital elongation of the pars interarticularis of the vertebra, spondylolysis, degenerative joint disease affecting the intervertebral facet joints, and rarely an acute fracture of the pars interarticularis

Spondylolysis: the presence of a loss of continuity of the pars interarticularis of a vertebral body. This can lead to instability and forward slip of one vertebral body on the one below it – spondylolisthesis

Spondylosis: degenerative change at one or more levels in the spinal column: degenerative intervertebral disc disease

Spontaneous fracture: One that occurs without adequate trauma, usually in abnormal bone – see Pathological fracture.

Spontaneous healing: The healing pattern of a fracture without treatment. Solid healing is observed in most cases, but malunion frequently results. This is how animal fractures normally heal in the wild

Stability of fixation: This is characterized by the degree of residual motion at the fracture site after fixation (i.e., very little or no displacement between the fragments of the fracture). In technical terms, stability describes the tendency to revert to a condition of low energy, but this strict definition is not adhered to in lingua franca of fracture surgery.

Stability, absolute: The compressed surfaces of the fracture do not displace under applied functional load. The definition of absolute stability applies only to a given time and at a given site: some areas of a fracture may displace in relation to each other whilst other areas of the same fracture locus may not; different areas may also exhibit different displacements at different times. Practically, the only method of achieving absolute stability consists in the application of interfragmentary compression (q.v.). The compression results in stability by preloading the fracture interface and by producing friction (Perren 1972).

Stability, relative: An internal fixation construct that allows small amounts of motion in proportion to the load applied. This is the case with a fixation that depends exclusively on the stiffness of the implant (such as a nail, or plate, bridging a multifragmentary fracture segment). The residual deformation or displacement is inversely proportional to the stiffness of the implant. Such motion is always present, but usually harmless, in nail fixation. According to the philosophy of the AO ASIF group, plate fixation is more reliable if motion can be prevented, but never at the expense of the biology of the fracture locus – see Biological fixation.

Stable fixation: A fixation which keeps the fragments of a fracture in motionless adaptation during the application of controlled physiological forces. While a mobile fracture produces pain with any attempt to move the limb, stable fixation allows early painless functional rehabilitation. Thus, stable fixation minimizes irritation, which could eventually lead to fracture disease – see Stability of fixation.

Stiffness: The resistance of a structure to deformation. Under a given load, the higher the stiffness of an implant then the smaller its deformation, the smaller the displacement of the fracture fragments and the lower the strain generated in the repair tissue. Excessive tissue strain can interfere with healing. The stiffness of a structure is expressed as its Young’s modulus of elasticity.

Stiffness and geometrical properties: The thickness of a structure affects deformability by its third power. Changes in geometry are, therefore, much more critical than are changes in material properties – a fact which is often overlooked by non-engineers. Thus, if flexible fixation is a goal, it can be achieved more effectively and in a more controlled manner by small changes of implant dimension than by using a “less rigid” material.

Strain: Relative deformation of a material, for example, repair tissue. Motion at the fracture site in itself is not the important feature, but the resulting relative deformation, which is called strain (dL/L), of the healing tissues. As strain is a ratio (displacement of fragments divided by width of fracture gap), very high levels of strain may be present within small fracture gaps even under conditions where the displacement may not be perceptible.

Strain induction: Tissue deformation – among other things -may result in induction of callus. This would be an example of a mechanically induced biological reaction. For those reactions triggered by strain, such as callus formation and bone surface resorption, the concept of a lower limit of strain, the minimum strain, is to be considered.

Strain tolerance: This determines the tolerance of the repair tissues to mechanical conditions. No tissue can be formed under conditions of strain which exceed the levels of strain which at rupture the tissue by excessive elongation. Above such a critical level, tissues strain will disrupt the tissue once formed, or will prevent its formation.

Strain theory – Perren: With a small fracture gap, any movement will result in a relatively large change in length (i.e. high strain). If this exceeds the strain tolerance of the tissue, healing will not take place. If a larger fracture gap is subject to the same movement, the relative change in length will be smaller (i.e. less strain) and, if the critical strain level is not exceeded, there will be normal tissue function and indirect healing by callus.

Strength: The ability to withstand load without structural failure. The strength of a material can be expressed as ultimate tensile strength, as bending strength or as torsional strength. The local criterion for failure of bone, or of implants, is measured in units of force per unit area: stress, or (equivalent) deformation per unit length (strain), or elongation at rupture.

Stress protection: This term, initially used to describe bone reaction to reduced functional load (Allgöwer et al. 1969) is used today mainly to express the negative aspects of any stress relief of bone. The basic assumption is that bone, deprived of its necessary functional stimulation by reducing its mechanical load, becomes less dense and so less strong (Wolff’s law). Stress protection is often used synonymously with stress shielding, that is in a purely mechanical sense. It is often used to characterize bone loss implying a negative connotation to stress shielding. With regard to the internal fixation of cortical bone, stress protection seems to play no important role, compared with vascular considerations – see Stress shielding.

The early boneloss seen deep to a plate, which has in the past been attributed to stress protection, can better be explained on the basis of a denial of blood supply to the underlying cortex, due to the pressure of the “footprint” of the plate. The resultant necrotic bone is then remodeled by osteons, which originate from the well vascularized, adjacent cortex. This remodeling process is associated with a temporary osteoporosis.

Investigations of late boneloss under clinical conditions of internal fixation in the human, using quantitative computed tomography, show very little residual bone loss at the time of implant removal (Cordey et al. 1985).

In summary, bone may react to unloading but this plays a minor role in internal fixation of cortical bone fractures.

Stress riser: In any body subject to deformation, stress will be generated within its material. If any part of the body is weaker than the rest, there will be a concentration of stress (high mean stress) at this place. If an implant is notched by inappropriate handling, the area of damage will act as a stress riser and produce the risk of fatigue failure with cyclical loading. If a hole is drilled in a bone and then left empty, this too will result in high mean stress and the risk of fracture. With the exception of the LCDCP, with its even strength, most plate holes represent weaker points on the plate than the solid sections between the plate holes: in a fixation with such a plate, where a screw hole has been left unfilled in the fracture zone, the empty hole acts as a stress riser and also produces the risk of fatigue failure, or bending under high functional load.

Stress shielding: When internal fixation relies upon screws and plates, the stability of the construct is achieved mainly by the interfragmentary compression exerted by the lag screws. Lag screw fixation alone is very stable, but generally provides little security under functional load. A plate providing protection (or neutralization) is therefore often added. The function of such a plate is to reduce the levels of peak load passing through the lag screw fixation. Protection is provided by virtue of the stiffness of the plate. The plate shields the fracture’s primary fixation with screws – see Neutralization and Protection.

Subchondral: means beneath the cartilage

Sudeck’s atrophy: One of the names given to Algodystrophy, Complex Regional Pain Syndrome, or Reflex Sympathetic Dystrophy

Superior: Literally above, or better than. In the anatomical position, if A is higher than, or above, B, then A is superior to B. The opposite is inferior.

Supination: The movement of rotating the forearm that causes the palm of the hand to face forward, that is restoring the hand to the anatomical position. Supination is also sometimes used to describe a movement of the foot into inclination toward the midline, otherwise called inversion; a supinated foot would bear more weight on its lateral border than on its medial border

Synovectomy: Excision of the synovial membrane. Synovial joint (diarthrodial joint): the commonest form of joint in the body, where two bone end, each covered with hyaline cartilage, articulate, the one on the other. They are bound together by a joint capsule and ligaments. The interior of the joint, other than the cartilage surfaces, is lined by synovial membrane, which secretes synovial fluid as a lubricant and a nutrient transport fluid.

Synovial membrane: the membrane lining the interior of a synovial (diarthrodial) joint, wherever the interior surface does not bear articular cartilage.

Systemic: Refers to any route for drug, or fluid, administration, other than via the gastro-intestinal tract, and usually by injection.

Tension band: An implant (wire, or plate) functioning according to the tension band principle: when the bone undergoes bending load, the implant, attached to the bone’s convex surface, resists the tensile force. The bone, especially the far cortex, is then dynamically compressed. The plate is able to resist very large amounts of tensile force, while the bone best resists compressive load: this bone-implant composite therefore is ideally suited to resist the bending force.

Threaded hole: Discussed in conjunction with Pilot hole

Tibial intercondylar eminence: The area of the proximal tibia lying between the medial and lateral tibial plateaux, which is non-articular and bears the attachments of the horns of the two menisci, and of the tibial ends of the anterior and posterior cruciate ligaments, to the anterior and posterior tibial spines.

Tibial spine: See Tibial intercondylar eminence

Torus: A geometrical body in the shape of a solid ring that in cross section is circular, or elliptical – such as an inflated tyre inner tube. It is a term used in architecture to described the circumferential bulge seen at the top and bottom of classical columns. It has been applied to the “wrinkle” or “buckle” appearance seen in the compression cortex of angular fractures of young children’s bones (torus fracture).

Toxins: Poisonous chemicals. Some pathogenic organisms release powerful toxins when they multiply, and some when they die.

Trabecula (pl. trabeculae): A solid bony strut of cancellous bone. Literally, a small beam, or bar

Tracheostomy: Surgical opening into the trachea (windpipe), usually to assist ventilatory support

Tract: Literally, a treatise or document (often religious), an anthem, an extent of territory, or an anatomical structure comprising mixed tissues organized to serve a specific physiological function (spino-thalamic tract, urinary tract, gastro-intestinal, etc.). It is commonly misused to describe the path created surgically through tissues by the insertion of an external fixator pin. In that context, the word “track” should be used (in the sense of its meaning the mark, or trail, left by the passage of anything – Oxford English Dictionary).

Trans-cortex: see Far Cortex

Transverse: Meaning across. Transverse bisection of the body in the anatomical position would divide it into upper and lower halves. Not the same as horizontal, which means parallel with the horizon. Thus if the body were lying flat on its back (supine), horizontal would be the same as the coronal plane (see above), but if the body were standing, in the anatomical position, horizontal would be in the transverse plane. In other words, horizontal is always related to the horizon, whereas the anatomical planes (coronal, frontal, sagittal, transverse) always relate to the anatomical position.

Union: Strictly speaking, union means “as one” – as in marital union, a workers’ union, even national groups, e.g. the United States. Equally strictly, if a fracture is fixed so that the bone functions as a single unit, then it has been surgically “united” (osteosynthesis): the bone is not, however, healed. Bone healing is a process initiated by fracture and continuing until the bone is restored to its final state by remodeling – this may take years. We speak loosely of a fracture’s being united, but this is not a discrete event. What we are saying is that a healing fracture has reached the point in the process of union when the experienced surgeon estimates that it can withstand normal functional loads for that patient. Union is, therefore, a judgment, usually based upon a synthesis of temporal, clinical and imaging information. This calls into question the validity of “time to union”, which is reported in so much of the surgical literature as a parameter for the judgment of the comparative efficacy of different treatments.

Valgus: Deviation away from the midline in the anatomical position. Thus, genu valgum is a deformity at the knee where the lower leg is angled away from the midline (knock knee). By convention any deformity, or deviation, is described in terms of the movement of the distal part.

Varus: Deviation toward the midline in the anatomical position. Thus, genu varum is a deformity at the knee where the lower leg is angled toward the midline (bow leg). By convention any deformity, or deviation, is described in terms of the movement of the distal part.

Vascularity: That property of a tissue which reflects the extent to which it has, or does not have, a blood supply. A tissue is said to be vascularised if its intrinsic network of blood vessels is connected to the main circulatory system. Blood vessels may be shut off temporarily from the circulatory system.. If the connection to the main circulation is permanently interrupted, or if the vessels present are not functioning, e.g. obliterated by thrombosis, the tissue is said to be avascular, or devascularized. We consider a tissue to be non-vascular if there are normally no functioning vessels, as in hyaline cartilage

Vertical: Upright. Perpendicular to horizontal. Derives from vertex, meaning the top, as in the vertex of the skull.

Wave plate: If the central section of a plate is contoured to stand off the near cortex over a distance of several holes, it leaves a gap between the plate and the bone, which (a) preserves the biology of the underlying bone, (b) provides a space for the insertion of a bone graft and (c) increases the stability because of the distance of the “waved” portion of the implant from the neutral axis of the shaft. Such plating is useful in non-union treatment

Wedge fracture: Fracture complex of the shaft of a long bone, with a third fragment, in which, after reduction, there is some direct contact between two the main shaft fragments -see Butterfly fragment. Also used to describe a compression fracture of a vertebral body, where the body has been crushed anteriorly and made wedge-shaped.

Working length: The distance between the two points of fixation (on either side of the fracture) between an implant, usually an intramedullary nail, and the bone.

Xenograft: A graft of tissue from an individual of one species (donor) to a recipient (host) of another species.

Zone of injury: The entire volume of bone and soft tissue damaged by energy transfer during trauma.

Adapted with permission from Mr P Brownson.

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