Use of pelvic incidence as a guide to reduction of H-type spino-pelvic dissociation injuries

OBJECTIVE: Describe the use of a radiographic parameter (pelvic incidence) to assess the sagittal plane reduction of H-type sacral fractures associated with spinopelvic dissociation, and assess the relationship between standing lumbar lordosis to pelvic incidence after spinopelvic dissociation. DESIGN: Retrospective radiographic and clinical review of treatment outcomes for patients with spinopelvic dissociation injuries secondary to H-type sacral fractures. SETTING: Level I Trauma Center. INTERVENTION: Pelvic incidence (PI), a radiographic parameter that measures the orientation of the lumbar spine relative to the pelvis, has been shown to have a correlation with the adequacy of surgical reduction as well as the risk of progression of high-grade spondylolisthesis. We used this parameter as a measure of sagittal plane reduction of spinopelvic dissociation injuries. PATIENTS/PARTICIPANTS: The clinical records and radiographs of five patients with spinopelvic dissociation injuries were reviewed. MAIN OUTCOME MEASUREMENTS: Radiographic measurements included standing PI and lumbar lordosis (LL). The relationship of lumbar lordosis on pelvic incidence was tested by a regression analysis. Clinical outcome was assessed by the self-reported ability of the patient to comfortably maintain an upright stance. RESULTS: The average follow-up period was 32 (range: 12-53) months. The average final PI was 82 (60-115) degrees. The average final lumbar lordosis was 58.2 (42-77) degrees. LL was found to be significantly related to PI (P < 0.05). One patient with an abnormally high PI had lumbar fatigue with persistent stance. CONCLUSIONS: Pelvic incidence is a potentially useful radiographic parameter that can be used to assess the adequacy of sagittal plane reduction in patients with spinopelvic dissociation injuries.