Quadriceps muscle wasting persists 5 months after total hip arthroplasty for osteoarthritis of the hip: a pilot study

Aims: To determine whether additional muscle fibre wasting of the ipsilater al vastus lateralis muscle occurs in the early postoperative period after t otal hip arthroplasty for osteoarthritis of the hip and whether there is an improvement in preoperative measures of quadriceps muscle thickness, stren gth, pain and function over a 5-month postoperative period. Methods: Twelve patients had ipsilateral needle quadriceps biopsy for muscl e morphology and bilateral quadriceps muscle thickness ultrasound preoperat ively, 5 days and 4 weeks postoperatively and a further muscle thickness me asurement at 5 months. Seven additional patients and five age-matched contr ol subjects had bilateral quadriceps muscle ultrasound thickness preoperati vely, 6 weeks and 5 months postoperatively, with assessment of quadriceps m uscle dynamometry, pain scores and Timed Up and Go (TUG) test. Results: Preoperatively, all 19 patients demonstrated significant atrophy o f the ipsilateral compared with the contralateral quadriceps muscle (P = 1. 8 x 10(-7)) on muscle ultrasound, which persisted at 5 months follow up (P = 0.009). Muscle morphology preoperatively showed type 2A and 2B muscle fib re atrophy on needle muscle biopsy, with further atrophy of all three fibre types (P = 0.029) at 5 days postoperatively associated with a fibre type s hift from type I to 2A fibres (P = 0.0011) at 1 month. There was improvemen t in hip pain postoperatively and a significant improvement in the TUG test (P = 0.007). However, there was no improvement in muscle strength on dynam ometry. Conclusions: There is significant ipsilateral quadriceps atrophy and weakne ss with 2A and 2B fibre atrophy preoperatively in patients with osteoarthri tis of the hip with exacerbation and further atrophy of all three fibre typ es 5 days postoperatively. Postoperative follow up showed that the reductio n in ipsilateral quadriceps muscle thickness persisted at 5 months despite physical rehabilitation. Patients did note significant improvement in pain postoperatively and improvement on functional assessment with the TUG test. Other therapeutic strategies may have to be developed to reverse disuse mu scle atrophy.