Does muscle inflammation influence recovery of muscle strength and function in patients undergoing total hip replacement?

Genetic markers of muscle inflammation (eg, tumour necrosis factor α [TNFα] and interleukin [IL] 6 are downregulated following repeated transient increases after bouts of exercise. Total hip replacement (THR) typically resolves preoperative pain, although strength deficits of 10–21% persist in the affected hip at 1 year postoperatively. This study assessed whether mRNA expression of TNFα and IL6 in the vastus lateralis (VL) of the operated leg was related to changes in the strength of the operated leg quadriceps in patients following THR.

Ten patients were recruited prospectively after ethical approval. Distal VL (5 cm proximal to lateral suprapatellar pouch) biopsy samples were obtained intraoperatively and at 6 weeks postoperatively, with maximal voluntary contraction of the operated leg quadriceps (MVCOLQ) in Newtons (N), assessed preoperatively and at 6 weeks postoperatively. RT-PCR was used to assess mRNA expression in the biopsy samples and associations evaluated with Spearman’s correlation coefficient.

Mean mRNA relative quotient (RQ) for comparison of 6 week intraoperative VL samples was 6·23 [SD 12·85] for TNFα and 17·10 [47·46] for IL6. Preoperatively, mean MVCOLQ was 188·90 N [76·84] and at 6 weeks it was 217·00 N [53·91]. There was no significant relation between TNFα or IL-6 RQ and absolute MVCOLQ at 6 weeks (r=0·115 [p=0·376] and −0·491 [p=0·075], respectively). No statistically significant relation existed between TNFα mRNA RQ and the improvement in MVCOLQ at 6 weeks (r=–0·498, p=0·071) nor with IL6 and the same measure (r=0·091, p=0·401).

There is a trend to correlation that exists for improvement in MVCOLQ with a reduction in TNFα mRNA expression, as well as between absolute MVCOLQ and reduction in IL-6 mRNA expression at 6 weeks postoperatively. Improvement in muscle strength may be mediated by reduced muscle inflammation and the associated reduction in pain in patients with severe osteoarthritis.

Wales Deanery and Betsi Cadwaladr University Health Board Small Grants Scheme.