Preoperative joint line convergence angle correction is a key factor in optimising accuracy in varus knee correction osteotomy

Abstract

Purpose This study aimed to identify and prevent preoperative factors that can be influenced in preoperative planning to reduce postoperative malcorrections. Methods The method used in this study was a retrospective two-centre analysis of 78 pre and postoperative fully weight-bearing radiographs of patients who underwent valgus osteotomy correction due to symptomatic medial compartment osteoarthritis. A computer software (TraumaCad®) was used to aim for an intersection point of the mechanical tibiofemoral axis (mTFA) with the tibia plateau at 55–60% (medial = 0%, lateral = 100%). Postoperative divergence ± 5% of this point was defined as over- and undercorrection. Preoperative joint geometry factors were correlated with postoperative malcorrection. Planning was conducted using the established method described by Miniaci (Group A) and with additional correction of the joint line convergence angle (JLCA) using the formula JLCA-2/2 (Group B). Additionally, in a small clinical case series, planning was conducted with JLCA correction. Statistical analysis was performed using (multiple) linear regression analysis and analysis of variance (ANOVA) with p < 0.05 considered significant. Results In 78 analysed cases, postoperative malcorrection was detected in 37.2% (5.1% undercorrection, 32.1% overcorrection). Linear regression analysis revealed preoperative body mass index (BMI, p = 0.04), JLCA (p = 0.0001), and osteotomy level divergence (p = 0.0005) as factors correlated with overcorrection. In a multiple regression analysis, JLCA and osteotomy level divergence remained significant factors. Preoperative JLCA correction reduced the planned osteotomy gap (A 9.7 ± 2.8 mm vs B 8.3 ± 2.4 mm; p > 0.05) and postoperative medial proximal tibial angle (MPTA: A 94.3 ± 2.1° vs B 92.3 ± 1.5°; p < .05) in patients with preoperative JLCA ≥ 4°. The results were validated using a virtual postoperative correction of cases with overcorrection. A case series (n = 8) with a preoperative JLCA > 4 revealed a postoperative accuracy using the JLCA correction of 3.4 ± 1.9%. Conclusion Preoperative JLCA ≥ 4° and tibial osteotomy level divergence were identified as risk factors for postoperative overcorrection. Preoperative JLCA correction using the formula JLCA-2/2 is proposed to better control ideal postoperative correction and reduce MPTA. The intraoperatively realised osteotomy level should be precisely in accordance with preoperative planning. Level of evidence III, cross-sectional study.

Preoperative joint line obliquity, a newly identified factor for overcorrection, can be incorporated into a novel preoperative planning method to optimise alignment in high tibial osteotomy

“…The overcorrection rate in this study was relatively high compared with that in other studies [11,42], where 42.9% was categorised as overcorrection when the acceptable range was set as 62.5 ± 6.25. Our analysis was conducted only on patients with well-performed bony corrections, and we therefore considered two possibilities.…”

“…Moreover, we identified a significant correlation between preJLO and ∆JLCA. Consequently, we obtained a model with higher explanatory power in the multiple regression analysis than that used in previous studies [11, 12, 35, 36].…”

“…'Latent medial laxity', defined as the difference between the preoperative JLCA in the standing position and the JLCA in the valgus stress radiographs, has been reported to be a significant factor [12,15]. Prediction models have been applied to predict changes in JLCA [11,12]; however, the explanatory power of these models is insufficient for clinical use. The possibility of other unidentified factors remains and the inaccuracy of bony correction may also act as a confounding factor.…”

A systematic approach to managing complications after proximal tibial osteotomies of the knee

“…A recent study by Behrendt et al [39] provided the first evidence that this additional planning step improves the accuracy of varus correction osteotomies and yields reduced postoperative medial proximal tibial angle (MPTA) values.…”

“…Clinical and experimental studies have shown that the JLCA has a normal range between 0° to 2°, which increases in magnitude depending on the severity and stage of osteoarthritis in the knee [1, 2, 10, 37, 39]. A positive value may be caused by an intra‐articular varus deformity with a medial apex [40].…”