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Biomechanical analysis of recently released cephalomedullary nails for trochanteric femoral fracture fixation in a human cadaveric model. Archives of orthopaedic and trauma surgery Pastor, T., Zderic, I., Gehweiler, D., Gardner, M. J., Stoffel, K., Richards, G., Knobe, M., Gueorguiev, B. 2021

Abstract

BACKGROUND: Recently, two novel concepts for intramedullary nailing of trochanteric fractures using a helical blade or interlocking dualscrews have demonstrated advantages as compared to standard single-screw systems. However, these two concepts have not been subjected to a direct biomechanical comparison so far. The aims of this study were to investigate in a human cadaveric model with low bone quality (1) the biomechanical competence of nailing with the use of a helical blade versus interlocking screws, and (2) the effect of cement augmentation on the fixation strength of the helical blade.METHODS: Twelve osteoporotic and osteopenic human cadaveric femoral pairs were assigned for pairwise implantation using either a short TFN-ADVANCED Proximal Femoral Nailing System (TFNA) with a helical blade head element or a short TRIGEN INTERTAN Intertrochanteric Antegrade Nail (InterTAN) with interlocking screws. Six osteoporotic femora, implanted with TFNA, were augmented with bone cement. Four groups were created: group 1 (TFNA) paired with group 2 (InterTAN), both consisting of osteopenic specimens, and group 3 (TFNA augmented) paired with group 4 (InterTAN), both consisting of osteoporotic specimens. An unstable trochanteric AO/OTA 31-A2.2 fracture was simulated and all specimens were tested until failure under progressively increasing cyclic loading.RESULTS: Stiffness in group 3 was significantly higher versus group 4, p=0.03. Varus (°)and femoral head rotation around the femoral neck axis (°) after 10,000 cycles were 1.9±1.0/0.3±0.2 in group 1, 2.2±0.7/0.7±0.4 in group 2, 1.5±1.3/0.3±0.2 in group 3 and 3.5±2.8/0.9±0.6 in group 4, being significantly different between groups 3 and 4, p=0.04. Cycles to failure and failure load (N) at 5° varus or10° femoral head rotation around the neck axisin groups 1-4 were 21,428±6020/1571.4±301.0, 20,611±7453/1530.6±372.7, 21,739±4248/1587.0±212.4 and 18,622±6733/1431.1±336.7, being significantly different between groups 3 and 4, p=0.04.CONCLUSIONS: Nailing of trochanteric femoral fractures with use of helical blades is comparable to interlocking dualscrews fixation in femoral head fragments with low bone quality. Bone cement augmentation of helical blades provides significantly greater fixation strength compared to interlocking screws constructs.

View details for DOI 10.1007/s00402-021-04239-7

View details for PubMedID 34748055