Postoperative radiologic outcome comparison between conventional and computer-assisted navigation total knee arthroplasty in extra-articular tibia vara

Abstract

Purpose: Total knee arthroplasty (TKA) is the definite treatment for osteoarthritis. Meanwhile, significant inherent extra-articular varus angulation is associated with abnormal postoperative hip–knee–ankle (HKA) angle. Computer-assisted navigation TKA (CAS-TKA) used in patients who have severe varus deformity. The purpose of this study was to compare postoperative radiologic outcome between CAS-TKA and conventional TKA for extra-articular tibia vara. Methods: A retrospective review of postoperative HKA on standing lower extremity views was conducted in patients who underwent TKA by a single surgeon from 2010 to 2018, including knee with conventional TKA (n = 83) and CAS-TKA (n = 246). Extra-articular tibia vara was assessed by measuring the metaphyseal–diaphyseal angle (MDA) of the tibia in preoperative standing lower extremity view. Postoperative alignment was assessed by measuring the HKA in postoperative standing lower extremity view. Results: There was no significant difference in age (p = 0.063), gender (p = 0.628), body mass index (p = 0.426), preoperative range of motion (p = 0.524), preoperative HKA (p = 0.306), preoperative MDA (p = 0.523), or postoperative HKA (p = 0.416) between the two groups (conventional TKA and CAS-TKA). There was no significant difference in postoperative alignment for cases with MDA ≤4° (p = 0.351) or MDA >4° (p = 0.866) in each group. There was a positive correlation between preoperative HKA and postoperative HKA in the CAS-TKA group (p < 0.001, r = 0.243). However, there was no significant correlation between preoperative HKA and postoperative HKA in the conventional TKA group (p = 0.732). Conclusions: There was no significant difference in postoperative alignment between conventional TKA and CAS-TKA in extra-articular tibial vara even for cases with MDA >4°.