Clinical use of quantitative computed tomography to evaluate the effect of less paraspinal muscle damage on bone mineral density changes after lumbar interbody fusion.

Study design: A retrospective cohort study.

Purpose: This study aimed to assess the reliability of quantitative computed tomography (QCT) in measuring bone mineral density (BMD) of instrumented vertebrae and investigate the effect of less paraspinal muscle damage on BMD changes after lumbar interbody fusion.

Overview of literature: Patients always experience a decrease in vertebral BMD after lumbar interbody fusion. However, to the best of our knowledge, no study has analyzed the effect of paraspinal muscles on BMD changes.

Methods: This retrospective analysis included a total of 155 patients who underwent single-level lumbar fusion, with 81 patients in the traditional group and 74 patients in the Wiltse group (less paraspinal muscle damage). QCT was used to measure the volumetric BMD (vBMD), Hounsfield unit value, and cross-sectional area of the paraspinal muscles at the upper instrumented vertebrae (UIV), vertebrae one segment above the UIV (UIV+1), and the vertebrae one segment above the UIV+1 (UIV+2). Statistical analyses were performed.

Results: No significant differences in general data were observed between the two groups (p>0.05). Strong correlations were noted between the preoperative and 1-week postoperative vBMD of each segment (p<0.01), with no significant difference between the two time points in both groups (p>0.05). Vertebral BMD loss was significantly higher in UIV+1 and UIV+2 in the traditional group than in the Wiltse group (-13.6%±19.1% vs. -4.2%±16.5%, -10.8%±20.3% vs. -0.9%±37.0%; p<0.05). However, no statistically significant difference was observed in the percent vBMD changes in the UIV segment between the two groups (37.7%±70.1% vs. 36.1%±78.7%, p>0.05).

Conclusions: QCT can reliably determine BMD in the instrumented spine after lumbar interbody fusion. With QCT, we found that reducing paraspinal muscle destruction through the Wiltse approach during surgery can help preserve the adjacent vertebral BMD; however, it does not help increase the BMD in the instrumented vertebrae.