A press release by the Hospital for Special Surgery (HSS), claims that the microscopic structure of bone appears to predict which patients will experience poor outcomes after spinal fusion, according to a new study published in Bone.
The press release states the most widely used technology to evaluate patients’ bones before spine fusion surgery is called dual x-ray absorptiometry, or DXA. DXA imaging gives physicians a rough sense of the strength of a person’s bone.
In this study researchers hypothesised that a more sensitive measure of bone quality could identify abnormalities in the skeleton that DXA does not detect, and that these defects would be linked to postoperative complications.
The study, led by Emily Stein (HSS, New York, USA) et al, used a cutting-edge technique for assessing bone called high-resolution peripheral quantitative computed tomography (HR-pQCT). HR-pQCT can separately measure how much bone is in the outer (cortical) and inner (trabecular) compartments and measure on a microscopic level how the inner trabecular bone network is organised, including the number, thickness and spacing between the parts of that network called trabeculae. These measurements—known broadly as the microarchitecture—may provide a much more robust assessment of skeletal health than DXA, particularly in this population of patients who frequently have changes in the area of the fusion which undermine the utility of DXA.
“DXA provides a two-dimensional measure of bone density, or the amount of bone present, whereas HR-pQCT provides a true three-dimensional measurement of the bone density,” Stein said. “This provides additional information about the structural features of bone that can be leading to weakness or fragility.”
The study included 54 men and women scheduled for spinal fusion at HSS between December 2017 and December 2019. Patients underwent conventional DXA scans, as well as HR-pQCT scans of the radius and tibia.
Of the 54 patients in the study, 14 experienced complications within the first six months of surgery, including broken rods, loosened bone screws, fractures and abnormal bending of the spine. Although the number of people in the study was small, the researchers found that those with abnormalities on HR-pQCT were significantly more likely to experience complications than those without such defects, these abnormalities were not evident on DXA imaging. Abnormalities involved lower bone mineral density in the trabeculae, fewer and thinner trabeculae, as well as thinner cortices.
Stein further, “We used HR-pQCT to show for the first time that abnormalities in the microscopic structure of bone are directly related to the development of complications after fusion. Our study identified several abnormalities in patients who had complications.”
Stein further added, “I think that it does provide a lot of additional information that we’re not getting from DXA. On DXA, the spine is almost always going to look fine, which can be misleading.”
Stein’s group is expanding their study to include more patients. “Spinal fusion surgeries are so invasive, the potential for complications is high,” she explained. “We want to have the most optimal strategies for lowering complications in our patients, and that begins with understanding who is at risk and why. In our future work with additional patients, we hope to be able to define which features, or group of features of the bone structure is most important in contributing to surgical success. This will help us to devise the most targeted treatment strategies for our patients.”
Findings were published in the journal Bone, and made available online first on November 4, 2020.