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A Biomechanical Study of Tuberosity-Based Locked Plate Fixation Compared to Standard Proximal Humeral Locking Plate Fixation for Three Part Proximal Humeral Fractures.

BACKGROUND
One of the main shortcomings of current proximal humeral plate designs is their inability to reliably secure the greater (GT) or lesser (LT) tuberosities, leading to fixation failure, nonunion, and rotator cuff dysfunction. Traditional proximal humeral locking plates rely on isolated screw fixation or suture repair to maintain reduction of the greater and/or lesser tuberosities. This study evaluates a tuberosity-based plate specifically designed to improve tuberosity fixation, which may decrease tuberosity displacement and related clinical sequelae.


METHODS
Five cadaveric specimens (ten shoulders) were randomized to receive either standard proximal humeral locking plate (PHLP) or tuberosity-based plate fixation (TBP). The specimens were skeletonized except for the rotator cuff insertion on the greater tuberosity. A reproducible 3-part osteotomy was performed for each cadaver, creating head, shaft, and GT segments. Anatomic reduction and plate fixation were performed according to the surgical technique guide for each plate system, with an equal number of screws placed in each plate both proximally and distally. GT fixation was enhanced with standardized suture augmentation through the rotator cuff in every specimen in both groups. In each trial, fracture displacement, load to failure, number of cycles endured, and mechanism of failure were noted.


RESULTS
The mean load to tuberosity fixation failure for the PHLP and TBP groups was 220N and 502N (p=0.005), respectively.


CONCLUSIONS
The TBP had a significantly higher load to failure and significantly lower mean fracture displacement compared to the PHLP.


LEVEL OF EVIDENCE
N/A.