Ji Weiping, Luo Congfeng, Zhan Yu, Xie Xuetao, He Qifang, Zhang Binbin
Department of Orthopedic Surgery, Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
Arch Orthop Trauma Surg. 2019 Jun;139(6):743-750. doi: 10.1007/s00402-018-03104-4. Epub 2019 Jan 23.
Varus deformity of knee osteoarthritis was formed by both intra-articular and extra-articular pathologies. Such intra-articular deformities could not be fully corrected by a medial open-wedge high tibial osteotomy (HTO), which was performed as an extra-articular procedure. Therefore, the purpose of this study was to investigate whether any residual varus was left inside the joint after HTO in the patients with knee osteoarthritis, and a correlation of the residual varus could be traced.
This study involved 66 patients (66 knees) undergoing HTO for medial knee osteoarthritis. The percentage of mechanical axis (%MA), mechanical femorotibial angle (mFTA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA) and joint line convergence angle (JLCA) were measured on radiographs of the full-length legs preoperatively and 6 months postoperatively. The relationship between changes in the JLCA and alignment correction was assessed. The postoperative residual JLCA was categorized as the optimal (postoperative JLCA ≤ 2°), the acceptable (2° < postoperative JLCA ≤ 5°), and the unacceptable (postoperative JLCA > 5°) to analyze its correlation with pre- or intra-operative factors.
Average %MA and mFTA were improved from 5.5 to 60% and from 190.2° to 176.4°, respectively. There was no change in mLDFA, whereas mMPTA changed from 80.3° to 91.8°. JLCA changed from 4.2° to 2.7°. The analyses of multiple linear regression showed that the preoperative JLCA and postoperative changes in mechanical alignment (%MA, mFTA and mMPTA) were two important variables dependently associated with differences in JLCAs postoperatively. However, postoperative JLCAs showed a stronger correlation to preoperative JLCAs than to changes in mechanical alignment postoperatively. A Chi-square analysis showed a significantly higher percentage of patients achieved acceptable postoperative JLCAs in the preoperative JLCA ≤ 6° group (78.8%) compared to the preoperative JLCA > 6° group (6.1%). Therefore, 6° of JLCA was suggested to be a tipping point.
The capability of HTO to correct intra-articular varus deformities, which was represented by JLCAs, is limited. Postoperative residual JLCAs were correlated primarily to preoperative JLCA values and total alignment correction, while the former accounted for most. A preoperative JLCA of 6° was suggested to be a tipping point, and a larger value indicated more than 5° residual JLCA after the HTO.
膝关节骨关节炎的内翻畸形是由关节内和关节外病变共同形成的。这种关节内畸形无法通过作为关节外手术的内侧开放楔形高位胫骨截骨术（HTO）得到完全矫正。因此，本研究的目的是调查膝关节骨关节炎患者接受HTO治疗后关节内是否残留内翻畸形，并探寻残留内翻畸形的相关性。
本研究纳入了66例（66膝）因膝关节内侧骨关节炎接受HTO治疗的患者。在术前和术后6个月的全腿X线片上测量机械轴百分比（%MA）、机械股胫角（mFTA）、机械股骨外侧远端角（mLDFA）、机械胫骨内侧近端角（mMPTA）和关节线汇聚角（JLCA）。评估JLCA变化与对线矫正之间的关系。将术后残留JLCA分为最佳（术后JLCA≤2°）、可接受（2°＜术后JLCA≤5°）和不可接受（术后JLCA＞5°）三类，以分析其与术前或术中因素的相关性。
平均%MA和mFTA分别从5.5改善至60%以及从190.2°改善至176.4°。mLDFA无变化，而mMPTA从80.3°变为91.8°。JLCA从4.2°变为2.7°。多元线性回归分析表明，术前JLCA以及术后机械对线的变化（%MA、mFTA和mMPTA）是与术后JLCA差异相关的两个重要变量。然而，术后JLCA与术前JLCA的相关性强于与术后机械对线变化的相关性。卡方分析显示，术前JLCA≤6°组术后JLCA达到可接受水平的患者比例（78.8%）显著高于术前JLCA＞6°组（6.1%）。因此，建议将JLCA 6°作为一个临界点。
HTO矫正以JLCA表示的关节内翻畸形的能力有限。术后残留JLCA主要与术前JLCA值和整体对线矫正相关，其中前者占主导。建议将术前JLCA 6°作为一个临界点，术前JLCA值越大，HTO术后残留JLCA超过5°的可能性越大。
