Injuries to the forearm bones

Chapter 8 Injuries to the forearm bones

1 Anatomical features: The radius and ulna are bound together by (1) the annular (orbicular) ligament, (2) the interosseous membrane, (3) the radio-ulnar ligaments and the triangular fibrocartilage. This gives the radius and ulna some of the features of (4) a bundle of sticks and (5) a linked parallelogram.

2 Direct violence: With direct violence it is possible to fracture either of the forearm bones in isolation. These injuries are comparatively uncommon, but do occur, especially in the ulna when in a fall the shaft strikes a hard edge. They may also occur when the ulna is struck by a weapon as the victim attempts to protect his head with his arms.

3 Indirect violence: More commonly the forearm is injured as the result of indirect violence, such as a fall on the back or the front of the outstretched hand. The force of impact on the hand stresses the forearm bones: the most common occurrence is for both to fracture.

4 Fracture–dislocations (a): If one forearm bone is seen to be fractured and angled, it has inevitably become relatively shorter (1). If its attachments to the wrist and humerus are intact, the other forearm bone must be dislocated. The commonest fracture–dislocation of this type is a fracture of the ulna with a dislocation of the radial head (Monteggia injury) (2).

5 Fracture–dislocation (b): The same pattern of injury occurs in the Galeazzi fracture–dislocation when a dislocation of the distal ulna accompanies a shaft fracture of the radius. Never accept a single forearm bone fracture as an entity until a Monteggia or Galeazzi injury has been eliminated.

6 Axial rotation (a): In any forearm injury, when the ulna fractures it may angulate or displace like any other bone (1). When the radius fractures, however, in addition to angulation one fragment may rotate relative to the other (axial rotation) (2).

7 Axial rotation (b): Axial rotation of the ulna is rare, but always check to see that it is not present. To do so, note that in the lateral projection the olecranon (1), coronoid (2) and styloid process (3) should be clearly visible. This relationship is lost in the presence of axial rotation (4).

8 Axial rotation (c): In the case of the radius, note any discrepancy in the widths of the fragments at fracture level. A difference as illustrated indicates the presence of axial rotation.

9 Axial rotation (d): Note also the normal relationship between the radial tubercle (1) and the styloid process (2) in this AP view of the radius in full supination. In full supination the radial tubercle lies medially (3). In pronation it lies laterally (4). In the mid position it is concealed (5). The position of the radial styloid should always correspond.

10 Axial rotation (e): Forces responsible (i): In all radial shaft fractures, pronator quadratus tends to pronate the distal fragment (1). In all upper (proximal) third fractures, pronator teres helps to pronate the distal fragment (2), assisting pronator quadratus in this movement.

11 Axial rotation (f): Forces responsible (ii): In upper third fractures, the proximal fragment is fully supinated by biceps (3) while the distal fragment is fully pronated by pronators teres and quadratus (1 and 2), (i.e. there is a maximal tendency to axial rotation). In fractures distal to the mid third, biceps is opposed, so the proximal fragment tends to lie in the mid position.

12 Fracture slipping (a): Greenstick fractures: In children’s greenstick fractures any intact periosteum on the original concave surface of the fracture exerts a constant, springy force which may cause recurrence of angulation if the plaster slackens, impairing three-point fixation. Frequent check films may be essential in any conservatively treated fracture.

13 Fracture slipping (b): Another contributory cause of fracture slipping is when muscle wasting occurs in a patient in a full arm plaster wearing a collar and cuff sling. Loss of brachialis and brachioradialis bulk leads to plaster slackening and angulatory deformity. (Note: the soft tissue shadows in Frame 29) Patients with conservatively treated fractures should be given broad arm slings.

14 Fracture of both bones of the forearm in children: Patterns (a): Most fractures are greenstick in pattern as illustrated. The radiograph shows fractures of the radius and ulna in the middle thirds. The distal fragments are tilted anteriorly (posterior angulation) but there is no displacement. An extensive, intact periosteal hinge can be assumed and reduction of such a fracture involves correction of the angulation only.

15 Patterns (b): When there is off-ending of one or both bones there is potential instability. Shortening and angulation are more likely, and axial rotation may occur; reduction and the maintenance of reduction may therefore be more troublesome.

16 Treatment (a): In the undisplaced angulated greenstick fracture, the child should be given a general anaesthetic and the angulation corrected. One hand applies a little traction and the corrective force, while the other acts as a fulcrum, under the fracture.

17 Treatment (b): If the fracture is overcorrected, the periosteum on the initially concave side of the fracture will be felt to snap. This will immediately give the fracture more mobility: this has the advantage of reducing the risks of late angulation, but has the disadvantage of requiring greater care with respect to the initial positioning in plaster.

18 Treatment (c): In the undisplaced greenstick fracture where there is no rotational deformity, the arm should be placed in a stable position while the cast is applied. To prevent re-angulation, fractures with posterior tilting (anterior angulation) (1) are generally most stable in full pronation, while the commonest fractures with anterior tilting (posterior angulation) (2) are best in full supination. If an extreme position is required, the cast should be changed at 4 weeks and the arm put in a more neutral position.

19 Treatment (d): Displaced fractures: These fractures are best dealt with under image intensifier control. When the fracture is displaced, axial rotation of the fragments should be looked for and the appropriate position in the pronation/supination range evaluated. The forearm is then placed in that position, and strong traction is applied for a quarter of a minute or so, with the patient well relaxed under a general anaesthetic. The elbow is flexed at a right angle for counter-traction.

20 Treatment (e): Displaced fractures ctd: Note that without image intensifier control that assessment of reduction is difficult, but often residual displacement may be detected by feeling the subcutaneous surface of the ulna in the region of the fracture. In the difficult case it is sometimes possible to gain bony apposition by applying traction and increasing the deformity before finally correcting it.

21 Treatment (f): Successful stable reduction: plaster fixation: To lessen the risks of ischaemia apply a back shell only, maintaining traction while this is done. Wool (1) is followed by the shell (2), held by cotton bandages. Just before the plaster sets give a final moulding (e.g. 3 – post-angulation fracture). Review the radiographic appearances before withdrawing the anaesthetic. (Note that some proximal third fractures in children are only stable with the elbow in extension.)

22 Radiographic appearances: (1) Persistent displacement without angulation may be readily accepted. (2) Complete off-ending without angulation is not normally acceptable (see later). (3) Slight angulation (10° or less) while undesirable will correct with remodelling in the younger child, and should be accepted. Marked angulation requires remanipulation.

23 Treatment (g): A broad arm sling, keeping the arm well elevated, should be employed, and the fingers exposed. If there is much swelling, or the reduction has been difficult, the patient should be admitted for elevation of the arm and circulatory observation: otherwise the child must be seen within 24 hours of the application of the plaster and the parents given the usual warnings.

24 Treatment (h): On review, the fingers should be checked for swelling, colour and active movements. If there is some doubt, slowly and gently extend the fingers – if this produces excessive pain, it is suggestive of ischaemia. If ischaemia is present, the encircling bandages must be split and the situation carefully re-assessed after a short interval. If the circulation is perfect, the plaster may be completed.

25 Treatment (i): Check the cast and the position of the fracture, preferably at weekly intervals, for 3–4 weeks; if satisfactory, the sling may then be discarded. Plaster fixation is maintained till union (usually after a further 3–4 weeks in a child of 10 years, and a further 1–2 weeks in a child of 4). The arm may be placed in a neutral position at 4 weeks if an extreme position was initially required. Thereafter mobilisation may be commenced from a sling.

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Tags: Practical Fracture Treatment

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

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