Tissue structure modification in knee osteoarthritis by use of joint distraction: an open 1-year pilot study.

Modification of joint tissue damage is challenging in late-stage osteoarthritis (OA). Few options are available for treating end-stage knee OA other than joint replacement. To examine whether joint distraction can effectively modify knee joint tissue damage and has the potential to delay prosthesis surgery. 20 patients (<60 years) with tibiofemoral OA were treated surgically using joint distraction. Distraction (~5 mm) was applied for 2 months using an external fixation frame. Tissue structure modification at 1 year of follow-up was evaluated radiographically (joint space width (JSW)), by MRI (segmentation of cartilage morphology) and by biochemical markers of collagen type II turnover, with operators blinded to time points. Clinical improvement was evaluated by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Visual Analogue Scale (VAS) pain score. Radiography demonstrated an increase in mean and minimum JSW (2.7 to 3.6 mm and 1.0 to 1.9 mm; p<0.05 and <0.01). MRI revealed an increase in cartilage thickness (2.4 to 3.0 mm; p<0.001) and a decrease of denuded bone areas (22% to 5%; p<0.001). Collagen type II levels showed a trend towards increased synthesis (+103%; p<0.06) and decreased breakdown (-11%; p<0.08). The WOMAC index increased from 45 to 77 points, and VAS pain decreased from 73 to 31 mm (both p<0.001). Joint distraction can induce tissue structure modification in knee OA and could result in clinical benefit. No current treatment is able to induce such changes. Larger, longer and randomised studies on joint distraction are warranted.