Constitutional and postoperative joint line obliquity can predict serial alignment change after opening‐wedge high tibial osteotomy: analysis using coronal plane alignment of the knee classification

Abstract

Purpose The purposes of this study were (1) to clarify the distribution of the Coronal Plane Alignment of the Knee (CPAK) phenotype in patients who underwent medial opening-wedge high tibial osteotomy (OWHTO) and ( 2) to identify the predictive factors for postoperative serial alignment changes after OWHTO by analyzing constitutional phenotypes. Methods Patients who underwent OWHTO between March 2014 and December 2019 were retrospectively evaluated. Those who completed a minimum follow-up of 3 years were divided into three groups based on the direction of alignment changes from postoperative 3 months to the final follow-up: Group 1 (varus direction) when the weight-bearing line ratio (WBLR) change was less than − 4%, Group 2 (maintained) when the WBLR change was between − 4% and 4%, and Group 3 (valgus direction) when the WBLR change was greater than 4%. The following parameters were assessed serially and compared between the groups: (1) radiologic parameters of coronal limb alignment such as joint line obliquity (JLO), (2) CPAK phenotypes, and (3) clinical outcomes. Results In total, 163 knees were included, and the average duration of follow-up was 4.8 ± 1.6 years. More apex distal JLO was observed in the order of Group 1, 2, and 3 at all times (all p < 0.05). The most common CPAK type was type (I + II) (constitutional: apex distal JLO) + type (V + VI) (postoperative 3 months: neutral JLO) in Group 1 (29.4%; p = 0.000); otherwise, the most common CPAK type was type (IV + V) (constitutional: neutral JLO) + type (VIII + IX) (postoperative 3 months: apex proximal JLO) in Group 3 (11.7%; p = 0.000). Clinical outcomes did not differ between the groups. Conclusion Constitutional and postoperative JLO were predictive factors of postoperative alignment changes after OWHTO. Constitutional apex distal and postoperative neutral JLO had a tendency for varus alignment progression, whereas constitutional neutral and postoperative apex proximal JLO had a tendency for valgus alignment progression. Level of evidence Retrospective cohort study; Level III.

CPAK classification detect the real knee joint apex position in less than half of the knees

“…In the existing literature, there are very few studies discussing that directly examine the relationship of CPAK JLO value or apex position with clinical outcomes. While the CPAK classification has become widely used in Total knee arthroplasty (TKA), its applicability in OWHTO and UKA remains unclear [2, 19]. One of the indirect findings of our study was that the use of the CPAK classification apex position in osteotomy indication and clinical follow‐up cannot provide real value and will be insufficient to evaluate radiographic findings.…”

“…Precise measurement of KJLO is a key factor, especially in osteotomy surgeries [2,22,25]. OWHTO alone can cause abnormal changes in KJLO, but double-level osteotomy may eliminate this risk [1].…”

“…In total knee arthroplasty, KJLO has a prominent role in assessing both the mechanical and kinematic alignment [3,5,9]. Similarly, it stands as a fundamental alignment target in surgeries such as unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) [2,13,25,28]. In the current literature, the impact of KJLO on clinical outcomes has been well-established [7,14,23].…”

“…However, CPAK can be affected by many parameters such as race, gender, and osteoarthritis severity [4, 27]. Therefore, the application of CPAK to correctly identify the same apex position as KJLO in a clinical setting remains inconclusive [2, 6]. The aim of this study is to determine the mutual concordance of the two measurement techniques.…”

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

“…In addition, complex biomechanics may have contributed to the statistical significance. Many recent studies on JLO associated with HTO have been reported [38–41]; however, most covered the association between postoperative JLO and clinical outcomes. The association between preJLO and ∆JLCA seems to be an area that requires further study.…”