PAIN REFERRAL PATTERNS IN PATIENTS UNDERGOING TOTAL HIP ARTHOPLASTY – DO THEY DETERMINE PATIENT OUTCOME?

Pathological conditions of the hip joint may present with variable patterns of pain referral in the lower limb. Literature reports suggest that up to 35% of total hip arthroplasties are performed on patients whose primary compliant is obturator nerve referred “knee pain”. However the effect of varied pain patterns on patient outcome and satisfaction has not previously been examined. This prospective study was undertaken to determine the most common referral patterns of hip pain in patients scheduled to undergo primary total hip replacement and to examine whether initial pain referral pattern predicted ultimate patient outcome. Patients were assessed using the Harris Hip score, SF 36 and WOMAC scoring systems measured preoperatively, at 6 months, 1 and 2 years post operatively. 236 patients were identified with isolated single hip joint disease. Patients who demonstrated multi joint disease, and particularly ipsilateral knee pathology were excluded. Forty-five percent of patients with primary hip disease had pain primarily at or about the knee. There was no difference in preoperative demographics, physical function, social function, perceived general health, Harris Hip score (p=0.74), SF 36 (p=0.66) or WOMAC scores (p=0.81) between the pain pattern groups. Operator status and operative techniques were comparable. At 1 and 2 years postoperatively the groin and thigh pain groups were similar in all respects. However at 6 months, 12 months and 2 years, Harris hip scores (p=0.04, p=0.037, p=0.021) and SF 36 scores (p=0.035, p=0.027, p=0.01) were significantly lower in those patients presenting initially with knee pain. Multivariate regression analysis confirmed that no other confounding variables could account for the observed differences between the groups. These results indicate that, using current outcome measures, patients with “knee pain” who undergo total hip arthroplasty, and in whom ipsilateral knee disease has been excluded, have poorer long-term physical and social function and perceived general health. We believe this is the first report of its kind and suggest that patient and surgeon expectations of the results of total hip arthroplasty should be tailored according to the individual initial pain referral pattern.