Pathology and healing of fractures

Chapter 1 Pathology and healing of fractures

1 Initial definitions: Fracture: A fracture is present when there is loss of continuity in the substance of a bone. The term covers all bony disruptions, ranging from one end of the scale when (1) a bone is broken into many fragments (multifragmentary or comminuted fracture) to (2) hair-line and even microscopic fractures at the other. To the layman the word ‘fracture’ implies a more severe injury than a simple break in the bone, but in the strict medical sense there is no difference between these terms.

2 Open fractures: All fractures are either closed or open. In an open fracture there is a wound in continuity with the fracture, and the potential exists for organisms to enter the fracture site from outside. All open fractures therefore carry the risk of becoming infected. In addition, blood loss from external haemorrhage may be significant. (Note: the term ‘compound’ is still frequently used to describe a fracture which is open; the term ‘simple’, to describe a closed fracture, may lead to confusion, and is now largely abandoned.)

3 Closed fracture: In a closed fracture the skin is either intact, or if there are any wounds these are superficial or unrelated to the fracture. So long as the skin is intact, there is no risk of infection from outside. (Blood-borne infection of closed fractures is extremely rare.) Any haemorrhage is internal.

4 Dislocation: In a dislocation there is complete loss of congruity between the articulating surfaces of a joint. The bones taking part in the articulation are displaced relative to one another; e.g. in a dislocated shoulder the head of the humerus loses all contact with the glenoid. In the common anterior dislocation the head of the humerus is displaced anteriorly.

5 Subluxation: In a subluxation, the articulating surfaces of a joint are no longer congruous, but loss of contact is incomplete. The term is often used to describe the early stages in a condition which may proceed to complete dislocation (e.g. in a joint infection or in rheumatoid arthritis).

6 Sprain: A sprain is an incomplete tear of a ligament or complex of ligaments responsible for the stability of a joint; e.g. a sprain of the ankle is a partial tear of the lateral ligament and is not associated with instability (as distinct from a complete tear). The term sprain is also applied to incomplete tears of muscles and tendons.

7 Causes of fracture: Direct violence (a): Fractures are caused by the application of stresses which exceed the limits of strength of a bone. Violence is the commonest cause. In the case of direct violence, a bone may be fractured by being struck by a moving or falling object, e.g. a fracture of the terminal phalanx of a finger by a hammer blow.

8 Direct violence (b): A bone may also be fractured if it forcibly strikes a resistant object. For example, a fall on the point of the elbow may fracture the olecranon.

9 Indirect violence: Very frequently fractures result from indirect violence.

A twisting or bending stress is applied to a bone, and this results in its fracture at some distance from the application of the causal force. For example, a rotational stress applied to the foot may cause a spiral fracture of the tibia. Indirect violence is also the commonest cause of dislocation.

10 Fatigue fractures: Stresses, repeated with excessive frequency to a bone, may result in fracture. This mechanism is often compared with fatigue in metals which break after repeated bending beyond their elastic limit. The commonest of these fractures involves the second metatarsal – the march fracture (so called because of its frequency in army recruits).

11 Pathological fractures (a): A pathological fracture is one which occurs in an abnormal or diseased bone. If the osseous abnormality reduces the strength of the bone then the force required to produce fracture is reduced, and may even become trivial. For example a secondary tumour deposit may lead to a pathological fracture of the subtrochanteric region of the femur – a common site.

12 Pathological fractures (b): Pathological fractures may also occur at the site of simple tumours, e.g. a fracture of the humerus (a) in a child with a simple bone cyst (b). The commonest causes of pathological fracture are osteoporosis and osteomalacia.

13 Fracture patterns and their significance: Hair-line fractures (a): Hair-line fractures result from minimal trauma, i.e. trauma which is just great enough to produce a fracture but not severe enough to produce any significant displacement of the fragments. Such fractures may be (1) incomplete or (2) complete.

14 Hair-line fractures (b): These fractures may be difficult to detect on the radiographs, and where there are reasonable clinical grounds for suspecting a fracture, the rules are quite clear. 1. Additional oblique radiographic projections of the area may be helpful. 2. Do not accept poor quality films. 3. Films repeated after 7–10 days may show the fracture quite clearly (due to decalcification at the fracture site). 4. A CT scan may also help confirm the diagnosis.

15 Hair-line fractures (c): Stress fractures are generally hair-line in pattern, and are often not diagnosed with certainty until there is a wisp of subperiosteal callus formation, or increased density at the fracture site some 3–6 weeks after the onset of symptoms. Where strongly suspected an MRI or bone scan may be helpful. Hair-line fractures generally heal rapidly requiring only symptomatic treatment: but the scaphoid and femoral neck are notable exceptions.

16 Hair-line fractures (d): Radiograph of upper tibia of an athletic adolescent with a 7-week history of persistent leg pain. Previous radiographs were reported as normal. Note the coned view to obtain optimal detail and the incomplete hair-line fracture revealed by bone sclerosis and subperiosteal callus. A crepe bandage support only was prescribed, and the symptoms settled in a further 6 weeks.

17 Greenstick fractures (a): Greenstick fractures occur in children, but not all children’s fractures are of this type. The less brittle bone of the child tends to buckle on the side opposite the causal force. Tearing of the periosteum and of the surrounding soft tissues is often minimal.

18 Greenstick fractures (b): This radiograph illustrates a more severe greenstick fracture of the distal radius and ulna. Note that although there is about 45° of angulation at the fracture site, there is no loss of bony contact in either fracture. The clinical deformity is clearly suggested by the soft-tissue shadow.

19 Greenstick fractures (c): Reduction of a greenstick fracture is facilitated by the absence of displacement and by the intact tissues on the concavity of the fracture. Angulation may be corrected by supporting the fracture and applying pressure over the distal fragment (1 and 2). The elastic spring of the periosteum may however lead to recurrence of angulation (3). Particular attention must therefore be taken over plaster fixation and after care.

20 Greenstick fractures (d): In the forearm in particular, where angulation inevitably leads to restriction of pronation and supination, some surgeons deliberately overcorrect the initial deformity (1). This tears the periosteum on the other side of the fracture (2). This reduces the risks of secondary angulation (3). Healing in all greenstick fractures is rapid.

21 Simple transverse fractures (a): Transverse fractures run either at right angles to the long axis of a bone (1), or with an obliquity of less than 30°. They may be caused by direct violence, when the bone fractures directly beneath the causal force (e.g. the ulna fracturing when warding off a blow (a)). They may also result from indirect violence when the bone is subjected to bending stresses by remotely applied force (e.g. a fracture of the forearm bones resulting from a fall on the outstretched hand (b)).

22 Simple transverse fractures (b): The inherent stability of this type of fracture (illustrated by the model on the right) reduces the risks of shortening and displacement. In the tibia, as a result, weight bearing may be permitted at a comparatively early stage. On the other hand, the area of bony contact is small, requiring very strong union before any external support can be discarded. (NB: The term ‘simple’ used to describe this and the following fractures means that the fracture runs circumferentially round the bone with the formation of only two main fragments.)

23 Simple oblique fractures (a): In an oblique fracture (1) the fracture runs at an oblique angle of 30° or more (O). Such fractures may be caused by (a) direct or (b) indirect violence. In simple spiral fractures (2) the line of the fracture curves round the bone in a spiral. Simple spiral fractures result from indirect violence, applied to the bone by twisting (torsional) forces (t).

24 Simple oblique and spiral fractures (b): In spiral fractures, union can be rapid (1) as there is often a large area of bone in contact. In both oblique and spiral fractures, unopposed muscle contraction or premature weight bearing readily lead to shortening, displacement and sometimes loss of bony contact (2). [Note: In the AO Classification of Fractures (see later) simple spiral, oblique and transverse fractures are classified as Type A fractures.]

25 In multifragmentary (comminuted) fractures there are more than two fragments. The spiral wedge fracture (1) is produced by torsional forces (t), and the bending wedge fracture (2) by direct (a) or indirect (b) violence. The fragment (B) is often called a butterfly fragment (because of its shape). With greater violence a fragmented (comminuted) wedge fracture (3) results. [All these fractures are in Type B in the AO Classification (see later) and their characteristic is that after reduction there is still bony contact between the main fragments (4)].

26 In multifragmentary complex fractures (a further division of comminuted fractures) there is no contact between the main fragments after reduction. In complex spiral fractures (1) there are two or more spiral elements; in complex segmental fractures (sometimes called double fractures) (2) there is at least one quite separate complete bone fragment (S). In complex irregular fractures (3) the bone lying between the main elements is split into many irregular fragments. [All these fractures are classified as Type C in the AO Classification.]

27 Multifragmentary fractures are generally the result of greater violence than is the case with most simple fractures, and consequently there is an increased risk of damage to neighbouring muscle, blood vessels and skin (1). The fractures tend to be unstable, and delayed union and joint stiffness are common. Segmental fractures are often difficult to reduce by closed methods, and direct exposure may threaten the precarious blood supply to the central segment. Non-union at one level is not uncommon in these fractures (2).

28 Impacted fractures: A fracture is impacted when one fragment is driven into the other (1). Cancellous bone is usually involved and union is often rapid. The stability of these fractures varies and is more implied than real. Displacement will occur if the fracture is subjected to deforming forces; e.g. without fixation, impacted femoral neck fractures frequently come adrift (2).

29 Compression (or crush) fractures: Crush fractures occur in cancellous bone which is compressed beyond the limits of tolerance. Common sites are (1) the vertebral bodies (as a result of flexion injuries) and (2) the heels (following falls from a height). If the deformity is accepted, union is invariably rapid. In the spine, if correction is attempted, recurrence is almost invariable.

31 Avulsion fractures (b): Avulsion fractures may also result from traction on a ligamentous or capsular attachment: these are often witness of momentary dislocation; e.g. (1) an abduction force may avulse the ulnar collateral ligament attachment, with spontaneous reduction. Late subluxation (2) is common with this (‘gamekeeper’s thumb’) and other injuries and is especially serious in the case of the spine.

32 Depressed fracture: Depressed fractures occur when a sharply localised blow depresses a segment of cortical bone below the level of the surrounding bone. Although common in skull fractures, this pattern is only rarely found in the limbs. There the tibia in the upper third is probably most frequently affected. Healing is rapid; complications are dependent on the site.

33 Fractures involving the articular surfaces of a joint: In partial articular fractures (1) part of the joint surface is involved, but the remainder is intact and solidly connected to the rest of the bone. (AO Type B fracture.) In complete articular fractures (2) the articular surface is completely disrupted and separated from the shaft. (AO Type C fracture.) When a fracture involves the articular surfaces, any persisting irregularity may cause secondary osteoarthritis (3). Stiffness is a common complication, and this may be minimised by early mobilisation.

34 Fracture close to a joint: When a fracture lies close to a joint, stiffness may also be a problem due to tethering of neighbouring muscles and tendons by spread of callus from the healing fracture; e.g. in fractures of the femur close to the knee, the quadriceps may become bound down by the callus, resulting in difficulty with knee flexion.

35 Fracture–dislocation: A fracture–dislocation is present when a joint has dislocated and there is in addition a fracture of one of the bony components of the joint. Illustrated is a fracture–dislocation of the shoulder, where there is an anterior dislocation with a fracture of the neck of the humerus. Injuries of this kind may be difficult to reduce and may be unstable. Stiffness and avascular necrosis are two common complications.

36 Complicated fractures: A fracture is described as complicated if there is accompanying damage to major neighbouring structures. The diagram is of a complicated supracondylar fracture of the humerus. (Such an injury might also be described as a supracondylar fracture complicated by damage to the brachial artery.)

37 Describing the level of a fracture (a): The anatomical divisions of a long bone include the epiphysis (E), the epiphyseal plate (EP), and the diaphysis or shaft (D). Between the latter two is the metaphysis (M). A fracture may be described as lying within these divisions, or involving a distinct anatomical part; e.g. (A) = fracture of the tibial diaphysis; (B) = fracture of the femoral neck; (C) = fracture of the greater trochanter; (F) = supracondylar fracture of the femur.

38 Describing the level of a fracture (b): For descriptive purposes a bone may be divided arbitrarily into thirds. In this way (A) = fracture of the mid third of the femur; (B) = fracture of the femur in the distal third; (C) = fracture of the femur at the junction of the middle and distal thirds.

The level of a fracture in some cases may be made quite clear by an eponym; e.g. a Colles fracture (D) involves the radius, and occurs within an inch (2.5 cm) of the wrist.

39 Describing the level of a fracture (c): In AO terminology, long bones are divided into three unequal segments: a proximal segment (1), a central diaphyseal segment (2), and a distal segment (3). The boundaries between these segments are obtained by erecting squares (S) which accommodate the widest part of the bone ends; in the special case of the femur the diaphysis is described as commencing at the distal border of the lesser trochanter.

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Tags: Practical Fracture Treatment

Mar 20, 2017 | Posted by admin in ORTHOPEDIC | Comments Off

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