Weightbearing after combined medial and lateral plate fixation of AO/OTA 41-C2 bicondylar tibial plateau fractures: a biomechanical study

Abstract

Background Combined medial and lateral plate fixation is recommended for complex tibial plateau fractures with medial fragments or no cortical bone contact. Although such fixation is adequate to resist forces during range of motion, it may be insufficient to support immediate postoperative weightbearing. Here, we analyzed displacement, stiffness, and fixation failure during simulated full weightbearing of bicondylar tibial plateau fractures treated with combined medial and lateral locking plate fixation. Methods We used 10 fresh-frozen adult human cadaveric tibias and mated femurs. Osteotomies were performed with an oscillating saw and cutting template to simulate an AO Foundation and Orthopaedic Trauma Association (AO/OTA) 41-C2 fracture (simple articular, multifragmentary metaphyseal fracture). Specimens were anatomically reduced and stabilized with combined medial and lateral locking plates (AxSOS, Stryker, Mahwah, NJ). Specimens were loaded axially to simulate 4 weeks of walking in a person weighing 70 kg. The specimens were cyclically loaded from 200 N to a maximum of 2800 N. Then, if no failure, loading continued for 200,000 cycles. We measured displacement of each bone fragment and defined fixation failure as ≥5 mm of displacement. Construct stiffness and load at failure were calculated. Categorical and continuous data were analyzed using Chi-squared and unpaired t-tests, respectively. Results Mean total displacement values after 10,000 loading cycles were as follows: lateral, 0.4 ± 0.8 mm; proximal medial, 0.3 ± 0.7 mm; distal medial, 0.3 ± 0.6 mm; and central 0.4 ± 0.5 mm. Mean stiffness of the construct was 562 ± 164 N/mm. Fixation failure occurred in 6 of 10 specimens that reached 5 mm of plastic deformation before test completion. In the failure group, the mean load at failure was 2467 ± 532 N, and the mean number of cycles before failure was 53,155. After test completion, the greatest displacement was found at the distal medial fracture site (2.3 ± 1.4 mm) and lateral fracture site (2.2 ± 1.7 mm). Conclusions Although combined medial and lateral plate fixation of complex tibial plateau fractures provides adequate stability to allow early range of motion, immediate full weightbearing is not recommended.

Importance of the Posterior Plate in Three‐Column Tibial Plateau Fractures: A Finite Element Analysis and Clinical Validation

“…Adequate buttressing strength and space can more effectively support the “bare area” of the posterior column 34 . Franulic et al 35 A recent cadaveric biomechanical study on bicondylar fractures highlighted that medial and lateral locking compression plates might delay full weight‐bearing due to insufficient strength when lacking support from bony union, especially in cases where the posterior column fracture is not addressed 36 . These findings partly explain why cases treated with the dual‐plate method in our study showed lower functional outcomes, likely due to inadequate posterior anatomical reduction and early rehabilitation.…”

Plate osteosynthesis combined with bone cement provides the highest stability for tibial head depression fractures under high loading conditions

“…Moreover, recent studies trend to recommend early full weight bearing 4 . But higher loading of the tibial plateau cause complications such as early secondary loss of reduction and valgus/varus deformation of the leg axis 5 , 6 . Therefore, high stability is demanded from the stabilisation technique.…”