BEWARE THE FIBULAR HEAD AVULSION FRACTURE- THE ANATOMICAL PATTERN OF POSTEROLATERAL CORNER INJURY AND ITS RELATION TO THE COMMON PERONEAL NERVE

Abstract

Purpose: The relationship of pattern of injury to this region of the knee to the intraoperative finding of abnormal common peroneal nerve position and associated nerve palsy was studied.

Methods: 54 consecutive patients with posterolateral corner disruption requiring surgery were assessed prospectively by MRI, arthroscopic examination, and by operative display. The pattern of disruption, the status of the biceps tendon and any displacement of the common peroneal nerve were recorded.

Results: Of the 54 cases, there were 9 with CPN palsy, 18 were seen to have distal injuries (13 suffering a fibular head avulsion fracture and 5 biceps tendon avulsion with no fracture). There was a strong relationship (p< 0.001) between such distal posterolateral corner injury and abnormal position of the common peroneal nerve, as 16 of the 18 (90%) patients were seen to have abnormal nerve position. No proximal injury resulted in abnormal nerve position and only 1 was associated with CPN palsy. 7 of the 13 cases of fibular head fracture had CPN palsy, and 1 of the 5 distal soft tissue avulsions.

Conclusion: There is a strong association of distal soft tissue avulsion and fibular head fracture and CPN palsy in these injuries. Whenever such a distal injury is suspected, the surgeon operating in this region should expect an abnormal position of the common peroneal nerve and appreciate the increased risk of iatrogenic damage. Presumably since the CPN is intimately bound to the biceps tendon by deep fascia, proximal retraction of the biceps tendon results in displacement of the CPN to an abnormal position and accounts for the high incidence of nerve palsy.