Capsular neuronal elements and their relation to pain reduction and functional improvement following total hip replacement.

We studied changes of pain intensity and functional impairment in 22 patients with osteoarthrosis undergoing total hip replacement. Using a visual analogue scale, the mean scores for pain and disability before surgery were 71.7 and 70.9 respectively. Both scores showed gradual improvement during a 1-year follow-up period, with more than 90% of the total improvement occurring within the first 3 months. After 1 year, the scores for pain and disability were 11.9 and 4.1 respectively. The hip joint capsule was studied using immunohistochemistry to detect neurofilaments. Neurofilament immunoreactivity was observed in 16/22 cases and was correlated with pain and disability scores. However, there were no correlations between pre- and postoperative pain scores, the score changes, and the quantity of capsular neurofilaments. Thus, other factors than capsular neurofilaments influence the scores of pain and disability in osteoarthritis.