Prediction model of knee joint line orientation after medial open wedge high tibial osteotomy

Abstract

Background: A joint line parallel to the floor is an important objective after medial open wedge high tibial osteotomy(MOWHTO). One of the methods to assess the coronal alignment of the knee after MOWHTO is knee joint line orientation relative to the ground (G-KJLO). There are no tools, however, for surgeons that could predict the value of post-operative G-KJLO before the surgery.

Methods: Fourteen radiographic parameters were measured in pre-operative and post-operative full-limb standing anteroposterior radiographs on 50 patients who underwent MOWHTO. The parameters were analyzed using multivariate linear regression to predict the G-KJLO after MOWHTO.

Results: After MOWHTO, G-KJLO increased from a mean value of -0.8° to 2.9°(P < 0.001). G-AJLO decreased after MOWHTO from a mean value of 8.3° to 1.5°(P < 0.001). Based on the multiple regression analysis by backward elimination of parameters influencing post-operative G-KJLO, we have derived an equation that can estimate post-operative G-KJLO after MOWHTO

post-operative G-KJLO (°) = 8.300 + 0.419 ⅹ pre-operative G-KJLO (°) + 0.923 ⅹ pre-operative medial proximal tibial angle(MPTA) (°) ­ 0.095 ⅹ pre-operative tibial width (mm) ­ 0.655 ⅹ pre-operative hip-knee-ankle(HKA) angle (°) + 0.444 ⅹ lateral distal femoral angle(LDFA) (°) + 0.662 ⅹ pre-operative joint space tilt angle(JSTA) (°) + 0.421 ⅹ aimed correction angle (°).

Conclusion: This study analyzed the effects of pre-operative anatomical alignment parameters to the post-operative G-KJLO. We established an equation which predicts post-operative G-KJLO with pre-operative anatomical alignment factors. This equation might help selecting optimal patients and operative plan for MOWHTO.