Background: This study evaluated the biomechanics of the proximal femoral nail antirotation-II (PFNA-II) in AO/OTA 31A2.2 intertrochanteric fractures based on the fracture reduction quality.
Methods: Unstable intertrochanteric fractures were created according to the AO classification and repaired by proximal femoral nail antirotation-II (PFNA-II) using one of three medial cortical support groups. The specimens were tested using cyclic axial loading. The following parameters were recorded: force and stiffness at failure, maximum vertical and horizontal displacement, neck-shaft angle, and location and patten of failure.
Results: In the cyclic loading test, the force at failure in the anatomical reduction (AR) group was greater than that of the positive medial cortical support (PMCS) group (984.22 ± 12.63 vs. 936.95 ± 16.78) N (P < 0.05) and negative medial cortical support (NMCS) group (918.04 ± 28.86) N (P < 0.05). The stiffness in the AR group was 4.77 and 31.9% higher than that in the PMCS group (P > 0.05) and NMCS group (P < 0.05). The maximum vertical displacement was the largest in the NMCS group. The maximum horizontal displacement in the NMCS group was 28.6 and 19.1% larger than that in the AR group (P > 0.05) and PMCS group (P < 0.05). The neck-shaft angle in the NMCS group was smaller than that in the anatomic reduction group (P < 0.05) and positive support group (P < 0.05).
Conclusion: For the unstable AO/OTA 31A2.2 intertrochanteric fracture, there were significant differences in their mechanical stability among AR, PMCS and NMCS. The NMCS is not recommended during the intraoperative reduction.
Keywords: Biomechanics; Intertrochanteric fracture; Negative medial cortex support; Positive medial cortex support.
© Indian Orthopaedics Association 2021.