gms | German Medical Science

Objective: Sarcopenia, the loss of spinal muscle mass with age, is associated with functional decline and increased morbidity in degenerative spinal disorders. As the population ages, the number of lumbar spinal instrumentation surgeries performed in patients with sarcopenia increases. The purpose of this study was to determine the impact of sarcopenia on implant failure (IF) and adjacent level degeneration (ALD) in patients with spinal instrumentation surgeries.

Methods: Data acquisition was conducted as a single-center retrospective analysis. Eighty consecutive patients receiving spinal fusion surgery from January 1st, 2012 to December 31st 2014, for spondylolysis or spondylolisthesis were included in our study. Cross-sectional areas of the psoas and paravertebral muscles at the mid-point of pedicles L3 and L4 were measured using axial CT images. In addition, measurement of Hounsfield unit (HU) values of trabecular bone in the middle axial CT image of vertebral bodies L2 and L3 were performed to assess the bone density.

Results: Eighty patients underwent instrumentation in 89 lumbar segments. The mean patient age was 62.2+-15.5 years, and 45 (56.2%) patients were females. Mean follow-up was 24.30+-19.93 months. Twelve patients necessitated revision surgery for either implant failure (58.4%, 7 cases, mean age 72.86+-12.86 years) or adjacent level degeneration (41.6%, 5 cases, mean age 58.0+-9.56 years). The average psoas muscle thickness was 791.8+-260.6 cm2 on L3 and 1142+-340.3 cm2 on L4. The average erector spinae thickness was 2186+-423.5 cm2 on L3 and 2204+-401.1 cm2 on L4. No significant difference was evident in the average psoas muscle thickness in patients with IF or ALD (832.2+-238.7 cm2) compared to those without (700.5+-215.2 cm2). However, the erector spinae muscle thickness was diminished in patients with (L3: 1695+-427.0 cm2; L4: 2264+-421.3 cm2) compared to those without IF/ALD (L3: 2266+-398.8 cm2; L4: 1747+-358.1 cm2). The detected differences were statistically significant in both levels (p < 0.005). In our cohort, muscle thickness was independent of chronological age (r2=0.03) and sex. Mean bone density in patients without IF/ALD was 125.4+-64.32 HU and 25.98+-20.33 HU (p<0.005).

Conclusion: In this study, patients with sarcopenic paraspinal muscles and reduced bone density had a significantly higher rate of IF and ASD. Therefore, measurement of muscle thickness and bone density using axial CT scans should be considered for a more individualized surgical procedure planning.