MALROTATION OF THE HUMERAL COMPONENT OF THE CAPITELLOCONDYLAR TOTAL ELBOW REPLACEMENT IS NOT THE SOLE CAUSE OF DISLOCATION

Malrotation of the humeral component of the capitellocondylar total el bow replacement is thought but not proved to be one of the major cause s of postoperative dislocation. The purpose of this study was to quant itate the effect of malrotation of the humeral component on the kinema tics and laxity of the capitellocondylar total elbow prosthesis. Eleve n fresh previously frozen elbows were used. With the humeral component in optimal position, external rotation, or internal rotation, movemen ts of the elbow with neutral, valgus, and varus loading were monitored with an electromagnetic tracking device. When the humeral component w as positioned in external rotation, the ulna was more valgus and supin ated than when the component was in optimal position, and when the com ponent was in internal rotation the ulna was more valgus in extension and more supinated in flexion. Malrotation in external rotation decrea sed valgus-varus laxity, and malrotation in internal rotation increase d rotational laxity. Only one elbow became dislocated, despite constan t severe maltracking between the components in all of the specimens. W e concluded that although malrotation of the humeral component influen ces the laxity and causes maltracking, it is not the primary cause of postoperative dislocation. The contribution of other factors should be investigated.