Purpose: This study was designed to assess the rate of displacement in nondisplaced sacral fractures and to determine if certain fracture patterns are more prone to future displacement.
Setting: Two Level I trauma centers.
Patients: Patients consisted of those sustaining a lateral compression pelvic fracture whose age was 17 years or older, had less than 5 mm of initial sacral displacement, were the result of a high-energy mechanism, and had radiographs documenting bony union.
Intervention: By protocol, patients meeting these criteria were mobilized and maintenance of alignment was documented by serial radiographs.
Results: All fractures were classified according to the Orthopaedic Trauma Association classification system, the Young and Burgess mechanistic classification system, and to the location of the sacral fracture as described by Denis. In addition, sacral fractures were classified as complete or incomplete. Additionally, the number and location of rami fractures were recorded. Of the initial 117 fractures, 23 were determined to displace and largely consisted of a single fracture pattern. Fractures consisting of a complete sacral fracture combined with bilateral rami fractures displaced at a rate of 68% (15 of 22). In contrast, incomplete sacral fractures with an ipsilateral rami injury had no displaced unions.
Conclusion: Incomplete lateral compression sacral fractures that are associated with ipsilateral rami fractures can be treated nonoperatively and are unlikely to displace. In contrast, those with a complete sacral fracture and bilateral rami fractures displace at a significantly greater rate.