Postoperative total hip prosthetic femoral head dislocations. Incidence, etiologic factors, and management.

Twenty-five dislocations occurred after 561 total hip arthroplasties performed by the author from 1971 to 1992. Acetabular shell and liner loosening must be differentiated from true dislocations. The dislocation rate of 5.49% in female patients was higher than the 2.8% rate in male patients. The 4.76% rate after 84 total hip revisions was slightly higher than the 3.98% rate after 477 primary replacements. No dislocations occurred using the anterolateral approach for 53 patients. Dislocation rates varied using different prosthetic systems for 508 patients who had the posterolateral approach used. Femoral prostheses with larger neck diameters were more prone to dislocation. These differences were not statistically significant with the sample sizes used, according to the chi square test for equality of proportions. Fluoroscopy aided reduction of one multiplanar recurrent case. Single hip spica abduction casts with and without knee hinges used for three to four months, along with abduction isometric exercises, led to stability in six recurrent cases.