Comparable medial proximal tibial angle measurements on full-leg standing radiographs and the Rosenberg view in patients undergoing high tibial osteotomy

Abstract

Introduction/objectives: Medial open wedge high tibial osteotomy (MOW-HTO) is a standard treatment for medial compartment osteoarthritis (OA) of the knee. Its success relies on precise preoperative planning, typically using full-leg standing radiographs (FLSR) for coronal alignment assessment. However, factors like knee flexion and rotation can influence alignment measurements. The Rosenberg view (RB), commonly used for OA assessment, may offer additional value in preoperative planning. This study investigates whether the medial proximal tibial angle (MPTA) measurements differ between RB and FLSR, hypothesizing that both methods yield comparable measurements.

Methods: This retrospective cohort study included 60 patients diagnosed with medial compartment osteoarthritis scheduled for MOW-HTO. MPTA was measured on both RB and FLSR radiographs by two observers. Interrater reliability was assessed using intraclass correlation coefficients, while Pearson correlation and Student's t-test were used to compare MPTA means between the two measurement techniques. The percentage of measurements exceeding a clinically acceptable threshold of 3° was reported. A Bland-Altman plot was generated to evaluate agreement.

Results: The mean MPTA was 86.0° ​± ​1.8° (95% CI: [85.55; 86.46]) on RB and 85.1° ​± ​1.6° (95% CI: [84.70; 85.50]) on FLSR, with a mean difference of 0.9° ​± ​2.41° (95% CI: [0.29; 1.51]), showing a statistically significant difference between the two modalities (p ​< ​0.001; Cohen's d ​= ​0.53). In 51 of 60 cases (85%), the difference remained within the threshold of 3°, while 9 cases (15%) exceeded this threshold. Pearson correlation analysis demonstrated a strong positive correlation between MPTA measurements on RB and FLSR (r ​= ​0.53, p ​< ​0.001). Bland-Altman analysis revealed 95% limits of agreement ranging from -3.61° to +5.41°.

Conclusion: This study found a small, statistically significant difference of <1.0° between MPTA measurements from RB and FLSR, which was not clinically relevant as 85% of cases were within the threshold of 3°. A strong correlation and good agreement on Bland-Altman analysis support the comparability of both methods. RB may therefore serve as a viable alternative for both diagnosis and preoperative planning in MOW-HTO, potentially reducing the need for additional FLSR in resource-limited settings while also minimizing radiation exposure.

Evidence level & study design: Level III, cohort study.

Keywords: Coronal alignment; MPTA; Open wedge high tibial osteotomy; Osteoarthritis; Unicompartmental knee osteoarthritis.