The elbow is a joint in which stability is provided by three elements; the bones, the ligaments and the muscles. The radial head and the coronoid process are important bony stabilisers and act as buffers to prevent the forearm dislocating from the end of the humerus. On the inside (medial side) of the elbow nearest the hip the medial collateral ligaments are important primary stabilisers that act like guy ropes to hold the ulna in place. The medial ligament has three elements the anterior band (which is most important for stability), posterior band and transverse band. On the lateral side the ligament structure consists of interlacing fibres at different angles and is referred to as the lateral ligament complex. The joint capsule adds stability but the muscles around the elbow are very important, contributing dynamic stability to the elbow and holding the forearm bones up against the end of the humerus.
Types of Instability
Acute – a traumatic episode disrupts one or more of the elements contributing to stability (bones, ligaments, muscles) by placing abnormal forces on to a normal elbow
Chronic/Recurrent – as a result of previous injury one or more of the stabilising elements is deficient and normal forces applied to the abnormal elbow can result in repeated dislocation or subluxation of the elbow.
Simple – A dislocation where there are no fractures but the soft tissues (ligaments, capsule and/or muscle origins) are disrupted.
Fracture Dislocation – dislocation of the elbow with a fracture of one or more of the bones of the elbow (humerus, radius or ulna).
As with other fractures and dislocations elbow instability can be either open injuries (with a breach to the skin) or closed.
Considerations for Treatment
The primary aim of management for elbow instability is to restore and maintain normal articular alignment. Surgery may be required to repair anatomical structures to permit active mobilisation of the elbow within a week of the injury if possible. The general principle is to restore at least three of four structures (lateral ligament complex, radial head, coronoid process and medial collateral ligament). If the distal humerus is damaged then restoration of two out of the three following elemements; medial trochlea ridge, capitellum and/or lateral trochlea ridge.
Active elbow mobilisation should commence as soon as possible after a dislocation or fracture dislocation, preferably by day five post injury where possible. Stability is improved by performing exercises while lying the patient on their back with the should flexed (brought forward) to 90 degrees. In this position gravity helps to maintain the congruency of the joint. Ice can help control swelling. Hinged elbow braces are not usually required and should be used only with caution under the supervision of a surgeon and physiotherapist. In some circumstances a surgeon may apply an external fixator (frame) to the elbow to maintain stability. Casts and splints are not usually employed other than for initial immobilisation while awaiting stabilisation, and should not be worn for more than three weeks.