Quantifying Distal Deltoid Disruption with Linear vs Curvilinear Plating of Proximal Humerus Fractures: A Cadaveric Study

Plate fixation of proximal humeral fractures is usually associated with some degree of distal deltoid dissection. The purpose of this study was to quantify deltoid release with standard linear vs. curvilinear plates utilized in the repair of proximal humeral fractures. Seven nonpaired, fresh-frozen clavicle-to-fingertip cadaveric shoulders met the inclusion criteria for the study. Four different proximal humerus implants were tested. One of these plates was curvilinear (89mm), and the other three were linear (85mm, 98mm, 109mm in length). Plates were compared based on the amount of deltoid insertion released for proper plate positioning. An ANOVA with post hoc Tukey tests was conducted to compare mean deltoid disruption across the three shortest plate types from each manufacturer. A linear regression analysis was conducted to analyze the effect of plate length on mean deltoid release. The mean deltoid insertion length was 39.6 ± 8.6mm (n=7). The curvilinear plate (89mm) required the least amount of average deltoid release at 4.1 ± 4.5mm, or 12.1% of the deltoid insertion. Independent ANOVA analysis including the three shortest plates from each manufacturer, found a significant effect of which plate was used on the amount of deltoid disruption that resulted (F(2, 18) = 18.0, p < .001, ω = .6). A linear regression including all four plates demonstrated a statistically significant direct relationship plate length and the mean deltoid released (y=.6x-43.8, r2=4). The current study demonstrates that proximal humerus plate length has a direct relationship with the amount of deltoid released during plating. Although deltoid disruption is length dependent, plate shape (curvilinear vs linear) could also be contributory. When comparing a curvilinear and a linear plate of similar lengths, the curvilinear plate resulted in less mean deltoid release.