Slope-reducing high tibial osteotomy (SR-HTO) is used to decrease excessive posterior tibial slope in patients with anterior knee instability, often in the setting of ACL deficiency or failure. This comparative study examines which technique best preserves frontal-plane alignment when reducing posterior tibial slope — infra-tubercle versus retro-tubercle — a key consideration to avoid unintended varus/valgus changes.
Study at a glance: design, patients, comparators
This retrospective matched cohort study involved 62 patients undergoing SR-HTO with ACL revision surgery (2020–2023). Two groups were compared: infra-tubercle (n=29) and retro-tubercle (n=33). Radiographic outcomes assessed included posterior tibial slope (PTS), hip-knee-ankle (HKA) angle, mechanical medial proximal tibial angle (mMPTA), and patellar height indices. Functional outcomes used the Simple Knee Value (SKV) score, and complications were recorded.
Primary aim: Reduce slope while maintaining the mechanical axis
Both techniques successfully achieved the planned reduction in PTS from ~14° to ~9°. However, infra-tubercle osteotomy demonstrated significantly greater accuracy in achieving the intended correction (mean deviation 1.2° vs 1.8°, p=0.02). Importantly, retro-tubercle osteotomy led to more coronal alignment changes, with greater alterations in HKA (1.4° vs 0.8°, p=0.05) and mMPTA (1.6° vs 0.9°, p=0.03). The infra-tubercle technique therefore better preserved frontal-plane alignment.
Patellar height & function: comparable PH, superior SKV with infra-tubercle
Patellar height remained stable in both groups, with no significant inter-group differences across Caton-Deschamps or Schöttle/Schröter indices. Functional outcome improvements (SKV) were significantly greater with infra-tubercle SR-HTO (+28.7 vs +20.7, p=0.008). These findings support infra-tubercle SR-HTO as a technique that maintains knee biomechanics and enhances patient-reported outcomes.
Safety profile & reoperations
Both approaches showed a similar and acceptable complication profile with no recorded hinge fractures. ACL re-rupture occurred in 3.4% of patients in each group. Hardware removal was more common after infra-tubercle osteotomy (24.1% vs 9.1%), though this difference was not statistically significant (p=0.2). The infra-tubercle technique’s precision and better functional scores may outweigh this minor trade-off.
Practical takeaways for surgeons
- Infra-tubercle SR-HTO offers superior precision in slope correction while minimising unintended coronal-plane changes.
- Patellar height is preserved with both techniques, enabling choice based on alignment and fixation strategy.
- For ACL-deficient knees requiring slope reduction, infra-tubercle SR-HTO provides a reliable approach for joint preservation while supporting improved functional outcomes.
Link to full paper: Higher precision and preservation of frontal plane alignment in slope-reducing infra-tubercle compared to retro-tubercle high tibial osteotomy
Sources used in report overview:
