Archives of Orthopaedic and Trauma Surgery - 2026-04-09 - Journal Article
Different sagittal cutting plane orientations do not affect posterior tibial slope in open wedge high tibial osteotomy: a Sawbone model study.
Gurbanov E, Cochard B, Bauer D, Miozzari H, Tscholl P
Topics
Key Takeaway
In a Sawbone model of biplanar MOWHTO, three sagittal cutting plane orientations (parallel, 10° anterior-inclined, 10° posterior-inclined) produced ΔPTS differences that never exceeded the 2.5° MCID threshold, with Bayesian equivalence assurance >86% across all comparisons.
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Summary
This study tested whether sagittal osteotomy plane orientation (parallel, 10° anterior-inclined, or 10° posterior-inclined) in biplanar MOWHTO affects PTS change, using 60 Sawbone models with cuts performed both proximal and distal to the tibial tuberosity. Navigation-measured ΔPTS and pairwise ΔPTS differences remained below the 2.5° MCID in all six groups, with Bayesian equivalence assurance exceeding 86% in every comparison. Valgus correction was achieved consistently across orientations, and ATT level (proximal vs. distal to tuberosity) did not modify the slope response.
Key Limitation
Sawbone models do not replicate the viscoelastic and anisotropic bone behavior that influences gap opening mechanics and slope change in vivo, limiting direct translation of these geometric findings to clinical practice.
Original Abstract
PURPOSE
Control of the posterior tibial slope (PTS) is crucial in high tibial osteotomy (HTO), since unintended changes can alter the normal knee kinematics and ligament loading. This study investigated the influence of sagittal cutting plane orientations on PTS in bi-planar medial open wedge HTO (MOWHTO) on a Sawbone model.
METHODS
Sixty Sawbone ® left-tibia models (A Pacific Research Company, USA) were used to perform biplanar MOWHTO with three sagittal orientations: (1) parallel to the medial tibial plateau (PO); (2) 10° anterior-inclined osteotomy (AIO); (3) 10° posterior-inclined osteotomy (PIO). The biplanar cut was performed distal to the tibial tuberosity in half the specimens and proximal in the remainder. Customized 3D-printed cutting guides ensured reproducibility. PTS and valgus correction were measured pre- and post-osteotomy using a navigation system. Group- and subgroup-specific ΔPTS were analyzed using a Bayesian multilevel model. Minimal clinically important difference (MCID) was set at 2.5°. Bayesian “power” analysis (assurance) was used to assess the sensitivity of ΔPTS and pairwise differences relative to the MCID.
RESULTS
Across the three sagittal orientation and their distal/proximal subgroups, ΔPTS and pairwise ΔPTS did not exceed the predefined MCID of 2.5°. Bayesian assurance of equivalence exceeded 86% in every unit and pairwise comparison, indicating a high confidence that the evaluated HTO configurations are clinically equivalent with respect to ΔPTS.
CONCLUSION
In this experimental study, different sagittal osteotomy inclinations in MOWHTO showed no clinically relevant changes in posterior tibial slope. No significant differences were observed across sagittal cut orientations or ATT levels.
LEVEL OF EVIDENCE
In vitro biomechanical study.