Sacral fracture after instrumented lumbosacral fusion: analysis of risk factors from spinopelvic parameters.

Study Design: Retrospective comparative study.

Objective: To examine the incidence and characteristics of key spinopelvic parameters that are correlated with sacral fracture development after lumbosacral fusion.

Summary Of Background Data: Sacral fracture is a possible complication of instrumented lumbosacral fusion and this has recently been documented in the literature. Preoperative awareness of risk factors concerning spinopelvic parameters and sacral fracture may aid in surgical planning to prevent its occurrence.

Methods: All patients who underwent instrumented lumbosacral fusion from L2 or above, between 2010 and 2011 at Gakkentoshi Hospital, were included.

Results: A total of 116 patients (47 men and 69 women) were evaluated in this study. Average age at surgery was 71 years, and the average follow-up period was 19 months. The average number of fixed segments was 5, and the average time interval between index surgery and sacral fracture development was 42 days. Notably, sacral fractures were identified in 5 patients (4.3%), all of whom were women. We, therefore, compared the 2 groups of female patients (fracture group, n = 5 vs. nonfracture group, n = 64). The fracture group had a substantially higher mean pelvic incidence (PI) than the nonfracture group (72° ± 8° vs. 51° ± 12°, respectively, P < 0.01). The fracture group also had a larger postoperative lumbar lordosis (LL)-PI mismatch than the nonfracture group (-26° ± 7° vs. -7° ± 18°, respectively, P < 0.01).

Conclusion: The current review of our patients informs appropriate preoperative planning in cases involving lumbosacral fusion for postmenopausal women with a high PI. Surgeons should plan to achieve large increases in LL to restore not only spinopelvic harmony but also to avoid postoperative sacral fracture. For such patients, because it is difficult to consistently achieve a sufficiently large LL, we recommend prophylactic iliosacral fixation to protect the sacrum.

Level Of Evidence: 4.