Parasymphyseal fracture location in lateral compression pelvic ring injuries: an assessment of reoperation and radiographic displacement in an international multicenter study

PURPOSE: To compare reoperation rates and radiographic outcomes between parasymphyseal fracture location and those in extra-symphyseal zones for lateral compression (LC) pelvic ring injuries. METHODS: This retrospective study included patients with acute, operatively treated LC injuries. Anterior ring fractures were classified based on a modified Nakatani classification as parasymphyseal (zone Ia), extra-symphyseal (zone Ib), zones II or III. Patient, fracture and implant characteristics were collected. The primary outcome was unplanned reoperation; secondary was radiographic loss of reduction. Comparisons were made across zones, with a sub-analysis restricted to LC1 injuries. Multivariable logistic regression was performed. RESULTS: Among 275 LC injuries (mean age 59.8 ± 21.3 years; 56% [n = 155] female; reoperation rates were 6.5% (n = 18) overall and did not differ significantly across zones (Ia 12% [7/60], Ib 5.7% [3/53], II 6.8% [7/103], III 1.7% [1/59]; p = 0.2). Radiographic deformity differed significantly across zones (Ia 27% [16/60], Ib 23% [12/53], II 24% [25/103], III 3.4% [2/59]; p = 0.004), driven by the markedly lower rate in zone III. Multivariable regression confirmed deformity was associated with the low rate in zone III, while older age (OR 1.02 per year, 95% CI 1.00-1.04) and ramus comminution (OR 2.11, 95% CI 1.06-4.20) were independently associated with deformity. Reoperation did not differ by zone. When restricted to 183 LC1 injuries (mean age 64.1 ± 19.5 years; 61% [n = 112] female), findings were similar. CONCLUSION: Parasymphyseal fractures represent a challenging LC cohort. Loss of reduction is common but driven primarily by comminution and patient age rather than fracture location alone.