Minimum 1-year follow-up for patients with vertical shear sacroiliac joint dislocations treated with iliosacral screws: does joint ankylosis or anatomic reduction contribute to functional outcome?

OBJECTIVE: To prospectively analyze a homogenous group of trauma patients with pure sacroiliac (SI) joint dislocations treated with iliosacral screws (ISS), with specific attention to functional outcome and its correlation with the presence or absence of SI joint ankylosis and quality of reduction. DESIGN: Retrospective chart and radiographic review of initial injury and treatment, with prospective long-term evaluation of radiographs, computed tomography (CT) scans, and functional assessments. SETTING: Level One Regional Trauma Center. PATIENTS: Twenty-three patients who were skeletally mature with traumatic vertical shear pelvic injuries associated with a pure SI joint dislocation. INTERVENTION: Treatment consisted of closed or open reduction in the supine or prone position and insertion of a single ISS placed percutaneously for the fixation of the posterior ring injury. MAIN OUTCOME MEASUREMENT: Each patient was evaluated for functional outcome using version 2 of the Short-Form 36 (SF-36v2), the short version of the Musculoskeletal Functional Assessment (sMFA), the Iowa Pelvic Scoring System, and the Majeed Pelvic Scoring System. Additionally, at the follow-up visit, each patient received plain radiographs of the pelvis and CT scanning of the pelvis. RESULTS: Minimum follow-up was 1 year postindex procedure (13-120 months). In this subset of patients with pure SI dislocations treated with ISS alone, anatomic reduction was the only predictor of a more favorable functional outcome (P = 0.04). Specifically, SI joint ankylosis did not affect functional outcome in these patients. CONCLUSIONS: Based on the results of this study, in the treatment of vertically displaced, pure SI joint dislocations, an anatomic reduction (whether closed or open), followed by ISS fixation should be the goal because this appears to be the only predictor of a more favorable functional outcome in patients with this injury. Complete SI joint ankylosis appears to have no effect, either positive or negative, on functional outcome in these patients.