Extra-capsular proximal femoral fractures: a cohort comparison of union and complication rates after ballistic versus blunt trauma.

Purpose: This study seeks to (1) describe the management of civilian ballistic extra-capsular proximal femur fractures (2) assess the rate of nonunion and complications and (3) compare the time to union of ballistic and blunt pertrochanteric femur fractures. Given the enhanced and widened extensive inflammatory response with ballistic trauma, we hypothesized that hip fractures from ballistic mechanisms would have faster times to union.

Methods: Patients were included if they were skeletally mature with extra-capsular pertrochanteric femur fractures and radiographic and clinical follow-up of at least 6 months. Additional exclusion criteria included prior femur fractures and pathologic fractures. Orthopedic Trauma Association classification of all fractures was included. Union rate, time to union and complications were measured. Clinical union was defined as absence of pain with ambulation at the fracture site. Radiographic union was defined as mRUST ≥ 11. mRUST was measured at 6 weeks, 3 months and 6 months. Patients were included if they met study end points of a minimum of 6 months of follow-up, achieved union, or underwent revision surgery for nonunion.

Results: 52 fractures (23 ballistic, 29 blunt fractures) matched by age, BMI, sex, diabetes, and current smoking status were included in the study. 95.7% of the ballistic (22/23) and 100% of the blunt (29/29) fractures united. Average time to union was 90.5 days for the ballistic cohort and 114.9 days for the blunt cohort (p = 0.03). There were six additional complications: three broken interlocks, one varus malalignment, one superficial infection, and one infection requiring an antibiotic spacer.

Conclusion: In our series, we found the average time to union for ballistic pertrochanteric femur fractures was significantly less than that for blunt pertrochanteric femur fractures. There was no significant difference in complications or total nonunion. Overall, our study shows both subgroups achieved union in 3 months, which is less than previously reported. The time to union may be increased in the ballistic fractures by the enhanced and widened extensive inflammatory response or the blast effect may inoculate osteogenic material in to the soft tissues that enhances the healing process. This study demonstrates unique characteristics of ballistic fracture healing.