Effect of varus and valgus alignment on implant loading after proximal femur fracture fixation
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More than 10 % of proximal femur fractures repaired with either a sliding hip screw and side plate (SHS-P) or a sliding hip screw and intramedullary nail (SHS-IMN) demonstrate varus malreduction. The purpose of this study was to compare the effect of varus or valgus loading on comminuted intertrochanteric fractures repaired with SHS-P or SHS-IMN constructs.
Unstable intertrochanteric fractures with segmental comminution were generated in 12 cadaver proximal femurs, six of which were fixed with an SHS-P and six with an SHS-IMN. Both implants had a strain gauge at the lag screw-nail–plate interface to assess implant load bearing. The load on the implants was measured with the specimens in neutral position and at 5°, 10°, and 15° of varus and valgus.
Loads on both SHS-IMN and SHS-P constructs were significantly increased when loading the implants in varus and significantly decreased when loading the implants in valgus. Unlike the SHS-IMN, the SHS-P trended toward increased load bearing at 15° varus (159.1 vs. 118.5 %, P = .065) and trended toward less load bearing at 15° valgus (42.3 vs. 59.8 %, P = .06). Conclusions: Regardless of implant choice, avoiding varus loading on the fixation construct reduces the load on the implant. SHS-P constructs may be more affected by varus or valgus malalignment than SHS-IMN constructs.
KeywordsProximal femur fracture Varus Malreduction Fracture fixation Intramedullary nailing Hip fracture Intertrochanteric fracture Pertrochanteric fracture Biomechanical testing
This study was partially funded by a RAP grant for young investigators from UCSF. No grant number is associated with this study.
Compliance with ethical standards
Conflict of interest
This study was funded by a grant from the UCSF Resource Allocation Program (RAP). None of the authors have conflicts of interest relevant to this study.
This article does not contain any studies with human participants or animals performed by any of the authors.
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