72.5 Posteriorly displaced supracondylar fractures in children

This a particularly important children’s fracture—the wrong treatment can easily make it worse. Supracondylar fractures are common between the ages of 3 and 11, and are rare after the age of 20.

A child falls on his outstretched arm, and breaks the lower end of the shaft of his humerus just above the epiphyseal line in one of four ways: (1) In a third of cases there is no displacement, or the fracture is incomplete, so that the child needs no treatment except for a collar and cuff. (2) In the remaining two thirds of cases the distal fragment is displaced posteriorly. The child is tender just above his elbow, which swells rapidly and obscures the bones round the fracture. (3) Occasionally, the lower fragment is displaced anteriorly (72.7). (4) Occasionally, separation takes place at the epiphyseal line and displaces the epiphysis. Treat these epiphyseal displacements exactly as if they were supracondylar fractures. Reduce them immediately. Like all epiphyseal injuries, they unite rapidly.

There is one rare immediate danger and two common later ones.

The rare immediate danger, both with this fracture and with posterior dislocations of the elbow, is that they can impair the blood supply to a child’s lower arm, and so cause the compartment syndrome followed by ischaemic fibrosis of his forearm muscles (Volkmann’s ischaemic contracture), or gangrene requiring amputation (70.4). Contracture from a supracondylar fracture is much rarer than Contracture as the result of failing to split a circular cast on a fracture of the forearm.

The force causing the injury pushes the distal fragment posteriorly and proximally, and the proximal fragment anteriorly and distally. The sharp proximal fragment pierces the periosteum, and comes to lie under brachialis. If the force continues the proximal fragment goes straight through brachialis into the child’s antecubital fossa, and may even penetrate his skin. As it moves forwards it may tear his brachial artery, or make the artery go into spasm, or it may injure his median or occasionally his radial nerve. The artery and the nerve may also come to lie between the proximal and distal fragments, and so prevent reduction. Worse, the antecubital fossa fills with blood. This: (1) obstructs the collateral vessels which might otherwise bypass the injured artery, and (2) impairs the venous return from his arm. The ischaemic forearm muscles swell and the compartment syndrome develops (73.7). Bending such an acutely swollen elbow is like trying to bend a balloon.

Figure 72.8: UNCORRECTED ANGULATION IN A SUPRACONDYLAR FRACTURE. Varus angulation is common and results in a loss of carrying angle in mild cases, or in an ugly varus deformity is more severe ones, like this child. It does not affect flexion and extension, so that disability is mild, but it does not look good. After perkins with kind permission.

The most common later disability is a very stiff, or fixed elbow. This is caused by the post– traumatic ossification that may follow repeated manipulation. So try to reduce the fracture with the minimum of manipulation. One attempt at manipulation followed by one more is the most you should try. Your first attempt is the most likely to succeed, and later ones will become more and more difficult.

The other common late disability is a deformed elbow. Some displacements remodel and others do not.

The displacements which remodel are: (1) Moderate angulation of the lower fragment in the plane of the elbow. (2) Posterior displacement of the lower fragment; growth of the epiphysis corrects this.

The displacements which do not remodel are: (1) Severe angulation of the lower fragment in the plane of the elbow. If you leave this unreduced, or reduce it badly, the child will be left with permanent hyperextension and severe loss of flexion. (2) Valgus or varus angulation. This does does not remodel, however mild it is or however young the child. Varus angulation is common and is usually accompanied by internal rotation and medial displacement. The result is a loss of the normal carrying angle in mild cases, or an ugly varus deformity in more severe ones, like the child in Fig. 72-8. This is common, and although it does not affect flexion or extension, so that disability is mild, it does not look good, and makes it difficult for the patient to carry a basket.

The principles of reduction are: (1) To exert traction on the child’s elbow, and while doing this to correct the sideways displacement of the distal fragment. Then, (2) to flex his arm while still exerting traction, so as to use his triceps tendon to hold the lower fragment in place. A common error is to try to correct sideways displacement after you have flexed his arm.

Never treat these fractures with a circular cast. The risk of Volkmann’s ischaemic Contracture is great. If you do apply plaster, it must be a backslab.