Pain and somatosensory findings in patients 3 years after total hip arthroplasty.

BACKGROUND: Chronic hip pain after total hip arthroplasty (THA) is a significant problem, but the aetiology remains unclear. AIMS: To determine sensory function in patients with chronic hip pain 3 years after THA. Patients without hip pain after THA served as controls.
METHODS: Eighteen patients with chronic hip pain and 18 controls without chronic hip pain were recruited from a previous questionnaire study about hip pain after total hip arthroplasty. All participants answered questions about pain and mental vulnerability and underwent clinical examination followed by quantitative sensory testing (brush-evoked allodynia, pinprick hyperalgesia, mechanical and thermal thresholds).
RESULTS: Brush-evoked allodynia was present in 4 patients with hip pain (P=0.1) and pinprick hyperalgesia (P=0.02) was more frequent in patients with chronic hip pain. Mechanical and thermal thresholds were similar in patients and controls. Patients with chronic hip pain had higher scores on the mental vulnerability scale (P<0.001). Chronic hip pain was significantly associated with low back pain (P=0.002).
CONCLUSIONS: We found signs of hypersensitivity on the operated side, which was more prominent in patients with pain. Pain referred from the back or deeper structures in the hip seems to play a role for the pain in subgroups of patients. In addition, chronic hip pain was associated with mental vulnerability.