The New Epidemic of Hip Instability: Why Spinal Fusion is the Hidden Culprit

A comprehensive review outlines the critical role of lumbopelvic alignment and prior spinal fusion in recurrent total hip arthroplasty instability.

There are multiple causes of recurrent dislocation after total hip arthroplasty (THA), including component malposition, extraprosthetic impingement, polyethylene wear, abductor muscle incompetence, altered neurologic or proprioception about the hip from neurologic disease or spinal disease, and, less commonly, adverse local tissue reaction from metal hypersensitivity or infection. Successful treatment of recurrent instability after THA requires an adequate assessment of the potential causal factors, an identification of the etiology, and a treatment approach targeting the specific etiology of the instability.

A detailed workup of the THA patient with recurrent instability is mandatory. As with all medical and surgical evaluations, a detailed history and physical examination are essential and must include the nature and direction of the instability. If the dislocation is an isolated event in the early postoperative period, within 3 months of surgery, with implants that are well-positioned, the patient can expect a reasonable chance of closed reduction, rendering the hip stable without further surgical intervention. Studies show a success rate of 67-81% for closed reduction of an early dislocation after a THA. Conversely, if more than once dislocation has occurred remote from the original surgery, the chance of closed reduction rendering the hip stable without further surgery is less likely.