Optimizing fixation in medial distal femur fractures: A biomechanical study

Atahan Durgal; Enver Kilic; Elif Naz Perdeci; Fatma Kubra Erbay Elibol; Taner Karlidag; Burak Kulakoglu; Teyfik Demir; Olgun Bingol; Guzelali Ozdemir

doi:10.52312/jdrs.2026.2543

Atahan Durgal¹, Enver Kilic¹, Elif Naz Perdeci², Fatma Kubra Erbay Elibol², Taner Karlidag³, Burak Kulakoglu⁴, Teyfik Demir⁵, Olgun Bingol¹, Guzelali Ozdemir¹

¹Department of Orthopedics and Traumatology, Ankara Bilkent City Hospital, Ankara, Türkiye
²Department of Biomedical Engineering, TOBB University of Economics and Technology, Ankara, Türkiye
³Department of Orthopedics and Traumatology, Gaziantep City Hospital, Gaziantep, Türkiye
⁴Department of Orthopedics and Traumatology, Antalya City Hospital, Antalya, Türkiye
⁵Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Türkiye

Keywords: AO 33-B2.1, mechanical study, medial femoral condyle fracture, synthetic bone, unicondylar distal femur fractures.

Abstract

Objectives: This study aims to biomechanically compare four fixation methods to identify the most stable construct under axial loading conditions.

Material and methods: A standardized osteotomy model simulating AO/OTA 33-B2.1 fractures was created in 28 synthetic femurs. Four groups (n = 7 each) were tested: (1) three 6.5-mm cannulated screws, (2) the same with an additional centrally placed screw, (3) three screws plus a 3.5-mm buttress plate, and (4) three screws combined with a reversed anatomical proximal tibial locking plate. Constructs were subjected to cyclic and static axial loading. The prespecified primary endpoint was load at 2-mm displacement, with stiffness and maximum load to failure as secondary outcomes.

Results: Group 4 exhibited the highest stiffness (802 ± 70 N/mm), maximum load (2360 ± 389 N), and resistance to 2-mm displacement (1138 ± 87 N). Group 2, with a centrally placed fourth screw, showed significantly improved performance in terms of maximum load compared to the traditional three-screw construct. While Group 3 improved stiffness over screw-only constructs, it did not significantly outperform Group 2 in key load metrics. Group 2, with a centrally placed fourth screw, demonstrated comparable stability to the buttress plate and anatomical locking plate in selected metrics, but remained inferior to the locking plate construct.

Conclusion: Central placement of cannulated screws to the medial femoral condyle enhanced axial stability in this synthetic model and represented a minimally invasive alternative to buttress plating in selected metrics. The highest stability was achieved with the combined use of cannulated screws and a locking plate. These results are restricted to axial loading and the tested endpoints; thus, further biomechanical, cadaveric, and clinical studies are warranted before generalizing to early weight-bearing. Given the anatomical challenges of the medial condyle, the development of anatomically contoured locking plates specifically designed for this region remains an important future direction.

Citation: Durgal A, Kilic E, Perdeci EN, Erbay Elibol FK, Karlidag T, Kulakoglu B, et al. Optimizing fixation in medial distal femur fractures: A biomechanical study. Jt Dis Relat Surg 2026;37(2):489- 500. doi: 10.52312/jdrs.2026.2543.