Biomechanical CT may identify patients at risk for reoperation, vertebral fracture
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Key takeaways:
- No patient younger than the age of 50 years tested positive for osteoporosis.
- Patients with osteoporosis had an almost fivefold higher risk for vertebral fracture.
Published results showed biomechanical CT analysis may identify patients aged 50 years or older with primary spinal fusion and osteoporosis who had elevated risks for reoperation and vertebral fracture.
“To date, physicians have been lacking a reliable test for osteoporosis and bone quality for their spinal fusion patients,” Tony M. Keaveny, PhD, professor of the departments of mechanical engineering and bioengineering and co-director of the Berkeley BioMechanics Laboratory at the University of California, Berkeley, told Healio. “These results indicate that preoperative [biomechanical CT] BCT, which utilizes a spinal CT scan that is typically ordered up anyway for presurgical evaluation of the patient, can provide a reliable means of identifying osteoporosis and poor bone quality.”
Using available coded information and CT scans from the medical records, Keaveny and colleagues extracted study data of a randomly sampled subset of 469 patients who had any type of primary thoracic or lumbar fusion between 2005 and 2018. Researchers had BCT analysis performed at a centralized lab blinded to clinical outcomes, and patients could test positive for osteoporosis based on either low values of bone strength and/or bone mineral density (BMD). Researchers considered reoperation for any reason as the primary outcome and newly documented vertebral fracture as the secondary outcome, both occurring up to 5 years after the primary surgery. They used Cox proportional hazard ratios adjusted by age, presence of obesity and whether the fusion was long or short, and compared Kaplan-Meier survival by the log rank test.
Results showed 11.1% of patients had a reoperation and 7.7% of patients had a vertebral fracture. Researchers found 25.8% of patients tested positive for osteoporosis by BCT, with no patients younger than the age of 50 years testing positive. Patients who tested positive for osteoporosis had an almost fivefold higher risk for vertebral fracture compared with patients without osteoporosis, according to results. While the 12.6% of patients who tested positive concurrently for low values of both bone strength and BMD had an almost fourfold higher risk for reoperation, researchers noted patients who tested positive for low values of either bone strength or BMD but not both were not at a significantly higher risk for reoperation. However, they were at higher risk for vertebral fractures. Researchers found patients who underwent short or long fusion had a high risk for reoperation and vertebral fractures.
“Incorporating BCT into the overall surgical planning process should reduce bone-related complications and revisions since surgeons will be better able to recognize high-risk patients and take mitigating steps they otherwise might forgo,” Keaveny said.
Perspective
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Tony M. Keaveny, PhD, and colleagues conducted an observational cohort study looking at the use of BCT to help identify patients at risk for a new fracture adjacent to spinal fusion. They used preoperative CT scans of these patients to measure bone strength and bone density. Investigators were able to adjust for age, obesity and whether greater or equal to four levels were fused with mean follow-up of 44 months.
In this cohort, 11.1% had a reoperation (14.5 months) and 7.7% developed a vertebral fracture (2 months). In addition, 25.8% of patients tested positive for osteoporosis and that created a fivefold increased risk for fracture. The patients who had both low bone strength and low bone density had four times the risk for reoperation. The risks remained high with both short and long fusions.
Many studies have shown higher rates of complications in spinal fusion patients who have osteoporosis including nonunion, screw loosening, proximal junctional kyphosis, cage subsidence and vertebral fracture. This study utilized a new validated technique offering information on bone density and bone strength. This study was able to effectively identify fusion patients at risk for fracture and reoperation. This study has shown that BCT can be utilized preoperatively to help identify “at-risk” patients for both fracture and reoperation so corrective strategies can be undertaken. This technique may surpass DXA or quantitative CT in its ability to identify at-risk patients. This represents an exciting new imaging tool that may become part of the standard of care to minimize complications in this challenging group of patients.
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