ObjectiveTo investigate the effect of medial 1/3 anatomical orientation of the tibial tubercle on the rotational alignment of Gemini MK-Ⅱ tibial components in total knee arthroplasty (TKA). MethodsBetween March 2011 and December 2012, 61 cases (67 knees) of varus knee osteoarthritis underwent Gemini MK-Ⅱ knee arthroplasty, and the clinical data were retrospectively analyzed. There were 12 males and 49 females, with an average age of 67.6 years (range, 50-82 years). The body mass index ranged from 20.9 to 33.7 kg/m2 (mean, 28.2 kg/m2). Unilateral TKA was performed in 55 cases and bilateral TKA in 6 cases. The duration of knee osteoarthritis ranged from 2 to 30 years (mean, 12.1 years). According to radiographic changes, 56 knees were rated as Kellgren-Lawrence grade Ⅲ and 11 knees as grade IV. During TKA, the tibial rotational alignment was determined by medial 1/3 anatomical orientation of the tibial tubercle. The anteroposterior and lateral X-ray films and CT scan were taken to measure the tibial rotational angle (TRA) at pre-and post-operation and to analyze the relative factors for TRA by Pearson correlation analysis. ResultsAll the patients were followed up 18-41 months (mean, 20.5 months). The range of motion (ROM) significantly increased from (98.806±16.969)° preoperatively to (116.806±11.458)° at last follow-up (t=-11.760, P=0.000). The knee society score (KSS) significantly increased from 111.239±20.344 to 160.522±17.872 at last follow-up (t=-27.271, P=0.000). The anatomical tibiofemoral angle (ATFA), posterior condylar angle (PCA), and TRA were all improved after TKA, showing significant differences when compared with preoperative ones (P<0.05). Rotational malalignment was observed in 11 knees (16.42%) before TKA, and in 14 knees (20.90%) at 1 week after TKA, showing no significant difference (χ2=0.443, P=0.506). There were 8 knees (11.94%) of internal rotation (>8°) and 6 knees (8.96%) of external rotation (>8°). The postoperative tibial prosthesis TRA had no correlation with the preoperative ATFA and tibial plateau TRA, the postoperative PCA and ATFA (r=-0.174, P=0.159; r=0.220, P=0.074; r=0.237, P=0.053; r=-0.095, P=0.442). ConclusionIn patients with varus knee osteoarthritis, medial 1/3 anatomical orientation of the tibial tubercle will contribute to the development of tibial rotational malalignment when TKA is performed by using Gemini MK-Ⅱ tibial components.