Sacral fractures complicating thoracolumbar fusion to the sacrum

Case series.

To report on the rare complication of sacral fractures after long instrumented thoracolumbar fusions to the sacrum.

Rigid spinal fusion with instrumentation results in redistribution of forces in the spine that can cause the adjacent segments to degenerate and fail. Rarely in long thoraco-lumbosacral fusion, these forces may lead to sacral fractures; only 4 cases are reported in the literature.

Five patients with sacral fractures are presented; one had the fusion performed at a different institution. Patients' characteristics, radiographic findings, and final operative treatment are discussed.

Sagittal imbalance after the index operation (thoraco-lumbosacral fusion), osteoporosis, and obesity were potentially associated factors. Initial nonoperative treatment failed to improve patients' symptoms. Surgery was performed at an average of 3.25 months (range, 2-8 months) in 4 patients, and soon after presentation in the patient operated elsewhere (presented 18 months after the sacral fracture). The signs of failed L5-S1 fusion, present in 3 patients, were considered to be additional surgical indication. At surgery the posterior instrumentation was extended to the pelvis. Both the fracture and the failed anterior interbody fusion were addressed through an anterior approach in 4 cases and in one case with a posterior ascending titanium cage spanning from S2 to L5. Sagittal balance was restored only in the last patient, where at the time of the revision operation a pedicle subtraction osteotomy was performed. Pain resolved in all patients after surgery and to the latest follow-up (range, 6-36 months).

Relapse of low back or buttock pain and leg pain after thoracolumbar fusion to the sacrum may be related to a sacral fracture, difficult to diagnose in conventional radiographs. Surgery should be considered in the presence of a concomitant L5-S1 pseudarthrosis and when symptoms do not improve with the nonoperative treatment.