According to a recently published study in the Archives of Orthopaedic and Trauma Surgery, patients who treated with HTO, found to have an exact residual varus was left inside the joint. As both extra- and intra-articular pathologies create varus deformity of the knee, therefore the medial open-wedge high tibial osteotomy (HTO), an extra-articular procedure may correct the intra-articular deformities or not, was identified.

In this study, investigators enrolled 66 participants who had undergone high tibial osteotomy for medial knee osteoarthritis. Mechanical lateral distal femoral angle (mLDFA), the percentage of mechanical axis (%MA), joint line convergence angle (JLCA), and mechanical medial proximal tibial angle (mMPTA) were assessed on radiographs of the full-length legs before and six months after the treatment. The association within changes in the alignment correction and JLCA was evaluated. To investigate JLCA correlation with pre- or intra-operative factors, postoperative residual JLCA was classified as the unacceptable (postoperative JLCA > 5°), acceptable (2° < postoperative JLCA ≤ 5°), and optimal (postoperative JLCA ≤ 2°).

Improvement in average mFTA, mMPTA, JLCA and %MA was noticed from 190.2°, 80.3°, 4.2° and 5.5% to 176.4°, 91.8°, 2.7° and 60%, respectively. No change was seen in mLDFA. The variables that dependently correlated with variations in JLCAs postoperatively were postoperative changes in mechanical alignment and preoperative JLCA. Although, no strong association was seen between JLCAs and preoperative JLCAs as compared to the changes in mechanical alignment following the treatment. A higher percentage of patients were found who obtained satisfactory postoperative JLCAs in the preoperative JLCA ≤ 6° group than preoperative JLCA > 6° group (6.1%). Hence, 6° of JLCA has proposed as a tipping point, and a higher value showed more than 5° residual JLCA following the treatment.