Characteristics and natural history of transient postoperative pseudosubluxation after total hip arthroplasty

A series of 13 total hip arthroplasties (THAs) in which immediate postoperative radiographs revealed axial subluxation were reviewed, and the timing, incidence, and subsequent natural history of this phenomenon were determined. Each patient had received perioperative epidural anesthesia and was placed in an abduction splint before transfer to the postoperative care unit. All initial radiographs were taken while the patient was still under the effect of the epidural anesthetic agent (average, 54 minutes; range, 37-80 minutes) postoperatively. In each case, radiographs taken after anesthetic recovery and without limb manipulation revealed reduced components. The balance of the postoperative care and rehabilitation was uncomplicated; patients were followed at least 36 months postoperatively, and in only 1 patient did a subsequent hip dislocation occur. Over a 6-month period, the postoperative films of all THAs were studied, and postoperative subluxation was identified in about 3% of the cases. Postoperative subluxation is likely to be noted when the radiograph is obtained within 1 hour of transfer to the postoperative care unit. It does not appear to have a dramatic effect on the rate of postoperative dislocation, however. This radiographic finding probably is due to the continued effects of regional anesthesia, and reduction occurs as muscle tone returns. If transient subluxation is identified, no change in postoperative care is necessary.