Session VII - Pelvis
Results of Posterior Fixation for Vertically Unstable Sacroiliac (SI) Dislocation: Does Anatomic Reduction Matter?
Purpose: Our objective was to determine if the quality of SI joint reduction after pure dislocation correlates with functional outcome.
Methods: A retrospective review of posterior pelvic ring injuries treated between January 1995 and December 2004 at two trauma centers identified 196 operative cases. Of these, there were 38 vertically unstable SI joint dislocations without an associated posterior fracture. All pure dislocations were treated operatively with either percutaneous or open attempts at an anatomic reduction followed by posterior cannulated lag screw fixation. All patients had standard anteroposterior (AP) pelvis, inlet, and outlet films and computed tomography (CT) performed at injury. Follow-up was at a minimum of 1 year (range, 13-120 months) after injury. All patients underwent radiographic examination including plain films and CT scan postoperatively. An anatomic reduction was defined as <0.5 cm AP or vertical displacement with no sagittal rotation. Clinical examinations were performed by an independent observer. Patients completed the following outcomes tests: SF-36, musculoskeletal function assessment (MFA), Majeed, and Iowa scores.
Results: Follow-up was possible in 23/38 patients (61%). There were no statistical differences in outcomes with respect to: sex, presence of an associated extremity injury, anterior fixation, open vs. percutaneous posterior fixation, secondary procedures, fixation failure, ankylosis of the joint, or presence of a neurologic deficit. An anatomic reduction (AR) was possible in 13/23 (57%) dislocations, while a nonanatomic reduction (NAR) occurred in 10/23 (43%). One patient lost an anatomic reduction at the time of follow-up (AR!íNAR). Functional outcome scores revealed that patients who had an anatomic reduction and maintained it, had significantly better results than those who did not [Majeed AR = 77 vs. NAR = 57 (P = 0.023), Iowa AR = 83 vs. NAR = 62 (P = 0.015), SF-36 AR = 93 vs. NAR = 90 (P = 0.7), MFA AR = 208 vs. NAR = 114 (P = 0.063)].
Conclusion: Anatomic reduction (within 0.5 cm) of vertically unstable SI dislocations treated with posterior fixation was the only variable found to be associated with a better functional outcome. Neither ankylosis nor removal of implants appear to have an effect on clinical results.
Significance: Patients with malreductions or loss of initial anatomic reduction should be counseled that their clinical outcome may be poor.