Abstract
Aim
To assess the relationship between mRNA expression of genetic markers of inflammation (tumour necrosis factor-alpha (TNFα)) and interleukin-6 (IL-6) in the vastus lateralis (VL) of the operated leg, and the strength of the operated leg quadriceps, in patients following THR.
Methods
Following ethical approval, 10 patients were recruited prospectively. Distal VL (5cm proximal to lateral supra-patellar pouch) biopsies were obtained intraoperatively and at 6 weeks post-operatively, with maximal voluntary contraction of the operated leg quadriceps (MVCOLQ) in Newtons(N), assessed preoperatively and at 6 weeks post-op. mRNA expression in the biopsies was assessed using the reverse transcriptase polymerase chain reaction (RT-PCR). Relationships were assessed using Spearman's correlation coefficient (data not normally distributed).
Results
mRNA RQ (comparison of 6 week VL samples to intraoperative samples) was (mean (SD)) 6.23(12.85) for TNFα and 17.10(47.46) for IL-6. Preoperatively mean MVCOLQ was 188.90(76.84) N and at 6 weeks it was 217.00(53.91) N. There was no significant relationship between TNFα or IL-6 RQ and absolute MVCOLQ at 6 weeks. A trend to significance was noted between TNFα and the improvement (%) in MVCOLQ at 6 weeks (R = −0.552, p=0.098) with no such relationship observed for IL-6 (R = 0.127, p=0.726).
Conclusions
In patients with hip osteoarthritis, reduced strength (MVCOLQ) appears to be mediated by muscle inflammation. The trend to correlation that exists for improvement in MVCOLQ with TNFα indicates that muscle inflammation may be one of the causes of pain in patients with severe osteoarthritis.
