Female gender, DDH, Revision surgery, and extremity lengthening are all risk factor for the development of a post-operative sciatic nerve palsy following total hip arthroplasty. Rheumatoid arthritis is not a risk factor.
Nerve palsy is an uncommon but devastating injury following total hip arthroplasty. Common causes include compression from hematoma or tight dressings, direct injury, and excess heat from polymethylmethacralate polymerization. Initial management in the post-operative period is to place the hip in extension and the knee in flexion to take tension off the sciatic nerve. If a hematoma is thought to be the cause, excavation in the operating room is the preferred treatment.
Schmalzried et al in CORR 1997 found the risk for post-operative palsy increased in females, those with a diagnosis of developmental dysplasia, and patients undergoing revision surgery. Obesity, RA, Perthes, and SCFE were not associated with nerve palsy following THA.
Farrell et al in a retrospective analysis of 27,000 primary THA found a 0.17% incidence of nerve plasy. Risk factors included preoperative diagnosis of DDH or posttraumatic arthritis, the use of a posterior approach, lengthening of the extremity, and cementless femoral fixation. Only 10 of the 28 patients at final follow-up had complete resolution of symptoms.
Illustration A shows an excellent representation of the sciatic nerve as it courses beneath the piriformis.
Schmalzried TP, Noordin S, Amstutz HC. Update on nerve palsy associated with total hip replacement. Clin Orthop Relat Res. 1997 Nov;(344):188-206.
PMID:9372771 (Link to Abstract)
Farrell CM, Springer BD, Haidukewych GJ, Morrey BF. Motor nerve palsy following primary total hip arthroplasty. J Bone Joint Surg Am. 2005 Dec;87(12):2619-25.
PMID:16322610 (Link to Abstract)