Research report: Postoperative alignment and patients reported outcome measures improvement after high tibial osteotomy: a significant interaction with osteoarthritis severity

For surgeons performing high tibial osteotomy, one of the most persistent questions has been where exactly to shift a patient’s weight-bearing line after surgery. In patients with early-stage disease, overcorrecting the alignment was associated with significantly smaller improvements in patient-reported outcomes, while in advanced osteoarthritis the degree of correction showed no such association at all.

The study, published in Archives of Orthopaedic and Trauma Surgery, analyzed 181 knees that underwent either open-wedge or closed-wedge high tibial osteotomy at a single center between January 2017 and December 2023, each with a minimum of two years of follow-up. The procedure has long depended on hitting a precise postoperative alignment target, yet the authors note that only 70 to 80 percent of knees in previous reports achieved the alignment surgeons intended.

The research team, led by Junya Itou and colleagues, divided the cohort into two groups based on Kellgren–Lawrence radiographic grading: 112 knees with early osteoarthritis, defined as grade 2 or lower, and 69 knees with advanced disease, grade 3 or higher. The two groups showed comparable baseline characteristics in age, sex, and body mass index, although closed-wedge procedures were performed more frequently in the advanced group. Each knee was treated as an independent observational unit, with 21 patients contributing both knees; the authors acknowledged that more complex modeling of within-patient correlation was not feasible given the limited number of bilateral cases.

Alignment was assessed using the percentage of the weight-bearing line, or %WBL, measured on double-limb standing full-length radiographs. All operations had aimed for the Fujisawa point, a classical target corresponding to a %WBL of 62.5 percent. Patients were then stratified into three postoperative groups: undercorrection below 55 percent, optimal correction between 55 and 69 percent, and overcorrection at 70 percent or above.

The central finding emerged from the early osteoarthritis group. After adjusting for preoperative scores, age, body mass index, and surgical method, overcorrection was significantly associated with smaller improvement in the Forgotten Joint Score, with a regression coefficient of −10.49 and a 95 percent confidence interval spanning −20.46 to −0.53. Overcorrection was also linked to smaller gains in the KOOS Sports subscale, and it reduced the likelihood of achieving both the minimum clinically important difference and the patient acceptable symptom state in early disease. Undercorrection, by contrast, did not show a statistically significant association with postoperative improvement, leaving the Fujisawa target and even somewhat more neutral positions without a demonstrated penalty in this cohort.

In the advanced osteoarthritis group, the picture was entirely different. Postoperative alignment was not associated with patient-reported outcome improvements, nor with achievement of the minimum clinically important difference or the patient acceptable symptom state. To test whether the relationship between alignment and outcomes truly differed by disease severity, the researchers ran formal interaction analyses in the full cohort, adjusted for age, sex, body mass index, surgical method, and preoperative scores. The interaction term reached statistical significance for the change in Forgotten Joint Score, with F = 3.68 and p = 0.03, and for the change in KOOS Sports, with F = 3.03 and p = 0.05, indicating that the effect of alignment on improvement was modified by osteoarthritis severity.

A supplementary analysis using restricted cubic spline modeling added an intriguing layer. Treated as a continuous variable, postoperative %WBL showed a statistically significant nonlinear association with improvement in the Forgotten Joint Score, with F = 2.47 and p = 0.046, and this nonlinearity was most pronounced in the early osteoarthritis cohort. The authors suggest that the commonly referenced threshold near 70 percent may not represent a universal inflection point, and that alignment may influence outcomes in early disease through a more complex relationship than simple categorical cutoffs imply. No meaningful spline effects appeared in the advanced group.

Why might excessive correction hurt outcomes in early disease but not advanced disease? The authors point to the geometry of the procedure itself. Because high tibial osteotomy adjusts only the tibial side, overcorrection produces an excessively large medial proximal tibial angle, and prior work has linked this to increased shear stress in finite element modeling and to significantly poorer clinical outcomes when the angle exceeds 95 degrees. The study also found that even with four experienced knee surgeons all aiming for the Fujisawa point, the resulting %WBL values varied substantially, a variability the authors attribute to surgical error and to the joint line convergence angle, which is influenced by soft-tissue release and therefore cannot be fully controlled. Notably, the observed postoperative %WBL values ranged only from 48 to 79, so outcomes outside that range remain unknown.

The findings partially support the 2022 ESSKA consensus guidelines, which recommend positioning the weight-bearing line closer to neutral in early osteoarthritis and shifting it toward valgus in more advanced disease. The authors note that the guideline’s alignment illustration was based on a simulation rather than patient-reported outcomes, making the present empirical data a meaningful complement. The results also suggest that targeting the Fujisawa point may remain a reasonable strategy overall, given that strict alignment control appears most critical in early disease while advanced disease tolerated the range of corrections studied without measurable differences in reported outcomes.

Several caveats temper the conclusions. The study was retrospective and monocentric, classified as level IV evidence, and conducted in an Asian cohort, so generalization to other populations warrants caution; the minimum clinically important difference and patient acceptable symptom state thresholds applied were derived from predominantly Caucasian cohorts. Follow-up was relatively short at a minimum of two years, the alignment groupings were acknowledged as arbitrary, and small subgroup sizes limited statistical precision, which the authors addressed by reporting effect sizes with 95 percent confidence intervals. Because the models did not adjust for anatomically relevant confounders such as preoperative %WBL, correction magnitude, joint line convergence angle, and the medial proximal tibial and lateral distal femoral angles, owing to collinearity and limited sample sizes, residual confounding may have influenced the associations. With multiple outcomes and subgroup-specific models, the authors themselves flag an elevated risk of type I error and describe findings with p-values near 0.05 as exploratory. A sensitivity analysis restricted to open-wedge cases, however, produced patterns consistent with the main results. Within those limits, the study delivers a clear practical message: when planning a high tibial osteotomy, the severity of the patient’s osteoarthritis should shape how aggressively the surgeon chases valgus correction.

Subject of Research: The interaction between postoperative alignment after high tibial osteotomy and osteoarthritis severity in patient-reported outcomes

Article Title: Postoperative alignment and patients reported outcome measures improvement after high tibial osteotomy: a significant interaction with osteoarthritis severity

Article References: Itou, J., Itoh, M., Kuwashima, U., Oda, T., & Okazaki, K. (2026). Postoperative alignment and patients reported outcome measures improvement after high tibial osteotomy: a significant interaction with osteoarthritis severity. Archives of Orthopaedic and Trauma Surgery, 146(1), Article 376. https://doi.org/10.1007/s00402-026-06540-9

Image Credits: AI Generated

DOI: 10.1007/s00402-026-06540-9

Keywords: high tibial osteotomy, osteoarthritis severity, postoperative alignment, weight-bearing line, Fujisawa point, overcorrection, Forgotten Joint Score, KOOS, patient-reported outcome measures, knee surgery, retrospective study, ESSKA consensus