Arthrography for the diagnosis of abductor avulsion after total hip arthroplasty: a comparison of arthrographic and surgical findings in 33 patients.

Background: Weakness of the abductor muscles--or even their avulsion--is a potential risk when total hip arthroplasty (THA) is performed using the anterolateral approach. Avulsion of the re-attached gluteus medius leads to a limp, but can also provide an open canal for joint fluid to escape to the trochanteric region. Thus, our hypothesis was that arthrography can be used to diagnose such detachment.

Methods: We compared THA arthrographies with peroperative findings retrospectively in 33 patients who had undergone surgical exploration for a muscle reattachment because of a strong suspicion of abductor avulsion at physical examination.

Results: After a mean follow-up time of 22 (2-57) months after THA, 14/33 patients had a positive (pathological) arthrogram whereas 19 had a negative (normal) result. All 14 patients with a positive arthrogram were verified to have an avulsion of the abductor muscle at the operation. 10 of the 19 patients with a negative arthrogram had an intact abductor insertion, but 9 had an avulsion. All of these 9 patients with the peroperatively disclosed avulsion had a fibrous capsule, which obstructed the fistula leading from the joint cavity to the trochanteric bursa region.

Interpretation: Arthrography is a valuable diagnostic aid in the evaluation of patients with abductor weakness and with Trendelenburg's gait appearing after a THA performed using the anterolateral approach. A positive finding helps in the operative decision making, but a negative arthrogram is not a reliable predictor.