Normalization of widespread pressure pain hypersensitivity after total hip replacement in patients with hip osteoarthritis is associated with clinical and functional improvements.

Objective: To evaluate the relevance of ongoing nociceptive joint inputs to the maintenance of widespread pain hypersensitivity in patients with hip osteoarthritis (OA) and to determine whether a reversal in the widespread pressure hypersensitivity together with an improvement in pain and function occurs after total hip replacement in these patients.

Methods: Forty patients with hip OA participated. Twenty patients underwent total hip replacement, and the other 20 patients were assigned to a waiting list. Pressure-pain thresholds (PPTs) over the second metacarpal bone and the gluteus medius, vastus medialis, vastus lateralis, and tibialis anterior muscles were assessed bilaterally with a pressure algometer before and 3 months after total hip replacement surgery. Assessments of pain intensity (by visual analog scale [VAS]), physical function (by the Western Ontario and McMaster Universities Osteoarthritis Index), and health status (by the Short Form 12 health survey and the EuroQol 5-domain index) were also performed.

Results: Patients who underwent total hip arthroplasty exhibited a reduction in widespread pressure pain hyperalgesia (increases in PPTs) over local and distant pain-free areas, as compared with before surgery and as compared with the patients assigned to the waiting list. PPTs were related to hip pain intensity, and significant correlations were found between higher VAS scores and lower average PPTs over all points assessed (-0.409 < r < -0.306, P < 0.05). Patients who underwent total hip arthroplasty exhibited a greater decrease in pain intensity and greater increases in function and health status than did those who were on the waiting list. Changes in the intensity of hip pain were moderately associated with changes in pressure pain sensitivity in the hip arthroplasty group.

Conclusion: Normalization of widespread pressure pain hyperalgesia was found after successful hip joint replacement in patients with hip OA. Altered pain processing seems to be driven by ongoing peripheral joint pathology, which stresses the importance of reducing pain in OA.