Effect of asymmetric anterior and posterior wedge openings on medial and lateral posterior tibial slope in medial open wedge high tibial osteotomy: An in vitro study on sheep tibias

Objective: This study aimed to evaluate the effects of different anterior and posterior wedge opening distances on medial and lateral pos terior tibial slope (PTS) angles during medial open wedge high tibial osteotomy (MOWHTO) using an in vitro sheep tibia model.

Methods: This in vitro study was conducted on 24 tibial bones from 2-year-old female domestic sheep. The samples were divided into 2 groups (n = 12 each) based on wedge configuration. Group 1 underwent osteotomy with a posterior opening of 6 mm and an anterior of 2 mm to reduce slope, while Group 2 received a 2 mm posterior and 6 mm anterior gap to increase slope. The medial and lateral PTS angles were measured separately using true lateral radiographs before and after osteotomy. Rotational changes were evaluated on computed tomography. Nine tibiae were excluded due to lateral hinge fractures; thus, the final analysis included 7 samples in Group 1 and 8 in Group 2.

Results: In Group 1, the lateral PTS decreased significantly more than the medial PTS (6.28° ± 2.5 vs. 1.49° ± 1.9, P = .03). In Group 2, medial and lateral PTS changes were similar (5.28° ± 2.8 vs. 5.76° ± 2.9, P = .79). Computed tomography images revealed that the hinge was intact in the anterolateral cortex in Group 1 (Fig 5a) and in the lateral cortex in Group 2. Rotational assessment showed external rotation of the proximal fragment in Group 1 (2.05° ± 1.38) and internal rotation in Group 2 (Fig 5b) (2.88° ± 1.62), with no significant difference between groups (P = .33).

Conclusion: In MOWHTO, applying a larger posterior opening than anterior results in greater lateral PTS reduction compared to the medial side, particularly when the hinge is located in the anterolateral cortex. These findings highlight the importance of wedge configura tion and hinge integrity in controlling sagittal plane alignment.

Cite this article as: Yahyaoğlu A, Ergün S, Eceviz E. Effect of asymmetric anterior and posterior wedge openings on medial and lateral posterior tibial slope in medial open wedge high tibial osteotomy: An in vitro study on sheep tibias. Acta Orthop Traumatol Turc., 2025;59(6):421-427.