A biomechanical comparison of fibular strut and femoral head allograft for augmented locking plate fixation in three-part proximal humerus fractures

TL;DR

This study compares two bone graft types for stabilizing complex shoulder fractures and finds both are equally effective biomechanically.

Contribution

The study provides a direct biomechanical comparison of fibular and femoral allografts for proximal humerus fracture fixation.

Findings

Fibular and femoral allografts showed no significant difference in loss of humeral head height during cyclic loading.

Both graft types had similar failure rates and stiffness during load-to-failure testing.

Femoral allografts may offer practical advantages like lower cost and better availability.

Abstract

It is not clear whether cortical fibular allografts or cancellous femoral allografts provide similar stability for augmentation of locking plate fixation of proximal humerus fractures. Therefore, this study aimed to assess and compare biomechanical properties of augmented locking plate fixation with 1) a cortical fibular allograft and 2) a cancellous femoral allograft.

Twenty-two fresh frozen humeri were randomly allocated to undergo unstable three-part fracture creation, locking plate fixation, and augmentation with cortical fibular or cancellous femoral allografts. All constructs were tested with cyclic loading (5 N to 532.5 N) for 1000 cycles at 1 Hz. Subsequently, constructs were loaded to 1700 N. Loss of humeral head height (HHH), ultimate failure loads, mode of failure, and stiffness were assessed.

Twenty humeri were included in the analysis. No failure occurred during cyclic loading. During load-to-failure testing, four (40.0%) fibula-augmented constructs and six (60.0%) femoral-augmented constructs failed. During cyclic loading, median loss of HHH was 2.00 (interquartile range [IQR], 1.12-3.50) for fibular grafts and 2.75 (IQR, 2.00-3.00) femoral grafts (P = .40). Median loss of HHH during failure tests was 9.50 (IQR, 7.88-15.50) for fibular grafts and 9.50 (IQR, 8.50-10.90) for femoral grafts (P = .68). The stiffness for fibular grafts was 174 (IQR, 106-186) and 157 for femoral grafts (IQR, 134-192) (P = .97).

There is no significant difference in biomechanical stability between cortical fibular allograft augmentation and cancellous hip allograft augmentation for locking plate fixation in proximal humerus fractures. Both techniques may equally prevent loss of reduction and early screw protrusion. Cancellous femoral allografts may yield advantages considering costs, availability, and future revision surgery with arthroplasty when compared to cortical fibular allografts.

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