Treatment for sacral insufficiency fractures: A systematic review

Is Osteoporosis an Independent Risk Factor for Sacral Fracture after Lumbosacral Spinal Fusion in Adults? A Retrospective Cohort Study

BACKGROUND CONTEXT

Sacral fracture is a rare complication following lumbosacral fusion in adults linked to post-surgical biomechanical changes. There are mixed research results suggesting that osteoporosis may or may not be a contributing factor.

PURPOSE

To determine if osteoporosis is an independent risk factor for sacral fracture after lumbosacral fusion.

STUDY DESIGN

A propensity-matched retrospective cohort study that was pre-registered on Open Science Framework PATIENT SAMPLE: After matching, patients (n=14,302; 82% female) who underwent lumbosacral fusion had a mean age of 64 years and were divided into the osteoporosis cohort (n=7,151) or the no osteoporosis cohort (n=7,151).

OUTCOME MEASURES

The primary outcome measure was the risk ratio (RR) of sacral fracture through two years after lumbosacral fusion. We secondarily explored the RR for pelvic fixation with instrumentation. We assessed negative control outcomes such as further imaging and major trauma, targeting near-null point estimates.

METHODS

We included adults (≥18 years old) in the TriNetX database from 2005-2023 who underwent primary lumbosacral fusion, divided into two cohorts depending on the presence or absence of osteoporosis (i.e., osteoporosis and no osteoporosis cohorts) and propensity matched via key risk factors.

RESULTS

There were 261 (1.8%) sacral fractures in the entire patient population (n=14,302). Comparing the osteoporosis cohort to no osteoporosis cohort, there was a statistically significant increase in risk of sacral fracture (RR: 1.75 [1.36, 2.24]; p<0.001; 166 [2.3%] versus 95 [1.3%] cases), with a median time to event of 154 and 181 days in each cohort, respectively. There was also a statistically significant increase in risk of pelvic fixation with instrumentation (RR: 1.87 [1.25, 2.78]; p=0.002). The likelihood of polytrauma (RR=0.98), subdural hemorrhage (RR=1.24), and diagnostic imaging (RR: 930) approximated the null between cohorts, suggesting findings would not be explained by differences in these variables.

CONCLUSION

Osteoporosis appears to be independently associated with a statistically and clinically significant risk of sacral fracture through two years after lumbosacral fusion. Further research may be warranted for corroboration.

Change in pelvic incidence due to sacral stress fracture following multilevel instrumented fusion

Multilevel-instrumented fusion is a common surgical technique used to treat adult spinal deformity (ASD), but it can occasionally lead to rare complications such as sacral insufficiency fractures. The impact of sacral fractures on spinopelvic parameters, particularly pelvic incidence (PI), has not been thoroughly investigated even though they have been documented in the literature. Here, we present a case of a patient who underwent a Th11-sacrum instrumented fusion for ASD. She underwent a revision surgery 18 months after the first procedure to treat proximal junctional pain brought on by a localised kyphosis of the rods. An asymptomatic sacral fracture was discovered during the radiological evaluation: the PI had increased from 71° to 103° between the 2 surgical procedures.