Posterior Compartment Debridement and Varus Deformity Correction in Total Knee Arthroplasty.

BACKGROUND

Restoration of joint-line position and deformity correction remain important tenets for preserving stability and function after total knee arthroplasty (TKA). We sought to characterize the role of posterior osteophytes in the correction of alignment deformity during TKA.

METHODS

We evaluated 57 patients (57 TKAs) who participated in a trial of robotic-arm assisted TKA outcomes. Weight-bearing and fixed preoperative alignment was measured using long-standing radiographs and tools of the robotic-arm tracking system, respectively. Total volume (cm3) of posterior osteophytes was quantified using preoperative planning computed tomography scans. Joint-line position was evaluated using bone resection thicknesses measured using a caliper.

RESULTS

The mean (minimum to maximum) initial fixed deformity was 4 degrees (range, 0 to 11) of varus. All patients showed asymmetric posterior osteophytes. Mean total osteophyte volume was 3 cm3 (range, 1 to 9). Total osteophyte volume was positively correlated with severity of fixed deformity (r = 0.48, P = .0001). Removal of osteophytes allowed for the correction of functional alignment to within 3 degrees of neutral in all cases (mean 0 degree), with none requiring release of the superficial medial collateral ligament. Tibial joint-line position was restored to within 3 millimeters in all but 2 cases (mean increase of height, 0.6 [range, -4 to +5]).

CONCLUSION

In the end-stage diseased knee, posterior osteophytes typically occupy space in the posterior capsule on the concave side of the deformity. Thorough debridement of posterior osteophytes may help facilitate management of modest varus deformity with decreased need for soft-tissue releases or adjustments to planned bone resection.