Comparison of novel anterior fixation method, W-plate, versus superior parasymphyseal plating in anterior posterior compression type III pelvic ring injuries: a biomechanical study

OBJECTIVES: To compare stiffness, displacement, and load to failure (LTF) patterns of a novel anterior pelvic plating technique, W-plating, to superior parasymphyseal plating (SPSP) in anterior posterior compression type III (APC III) pelvic ring injuries in a biomechanical model. METHODS: Twelve fourth generation composite pelves with induced APC III injuries stabilized with posterior screw fixation and either W-plating or SPSP were stressed via the Instron machine under single leg stance (SLS) axial load and external rotation (ER) load. Motion was analyzed at the pubic symphysis (PS) and sacroiliac joints (SIJ). PS and SIJ displacement, rotation, and stiffness were compared between the W-plate and SPSP groups under simulated stressed conditions. T-test was used to compare means and significance was set at p<0.05. Unadjusted p-values were reported alongside effect sizes (Cohen’s d) and 95% confidence intervals (CI) to provide additional context regarding the magnitude and potential biomechanical relevance of the observed differences RESULTS: The W-plate demonstrated less inferior PS displacement than the SPSP under SLS with a large observed effect size (0.5 ± 0.4 mm vs 1.2 ± 0.5 mm, respectively, Cohen’s d = 1.47). Average PS displacement also demonstrated a large effect size favoring the W-plate construct (Cohen’s d = 1.07), though statistical significance was not reached (0.3 ± 0.3 mm vs 0.7 ± 0.3 mm respectively, p = 0.07). There were no significant differences in stiffness in the SLS for the W-plate versus SPSP (98.9 ± 11.2 vs 105 ± 6.6 N/mm, respectively, p = 0.6) or in ER (4.4 ± 2.2 v 3.1 ± 1.6, respectively, p = 0.3). When loaded to failure, the W-plate and the SPSP both failed at the posterior fixation with no significant difference between groups (1411± 221 v 1545 ± 225 N, respectively p = 0.4). CONCLUSIONS: In a biomechanical analysis of induced APC-III pelvic ring injury, W-plating performed similarly to SPSP in stiffness, displacement, and LTF. W-plating for anterior pelvic ring fixation was found to be biomechanically similar to SPSP with potentially increased resistance to anterior ring displacement. LEVEL OF EVIDENCE: V