The Frail Factor: Can Muscle Loss Predict Overreliance on Opioids After Spinal Surgery?

Introduction: According to the CDC, in the US, approximately 81,000 deaths were attributed to opioid overdose in 2023. Despite the dangers of addiction and overdose associated with their use, they continue to be standard of care for pain management after spine surgery. Recently, studies have suggested that central sarcopenia, which is measured using the psoas muscles, detriments success of lumbar fusion surgeries. We hypothesize that decreased muscular density surrounding spinal fusions contributes to further post-operative pain.

Methods: We aimed to determine how muscle integrity impacted post-operative opioid use. We conducted a retrospective review of all spinal deformity surgeries at our tertiary care center from 2016-2023. Looking at axial MRI images, we used ImageJ to calculate the psoas and L4 vertebral index (PL4VI) as a measure of central sarcopenia. We also collected these measurements at the psoas upper instrumented vertebral index (PUIVI) if that level was flanked by the psoas muscles (i.e. L1-L4). To determine the length of opioid use, we collected the last mention of opioid use after surgery. Regression models and Pearson correlation coefficients were calculated using SPSS.

Results: PL4VI was calculated for 178 patients and PUIVI for 74 patients. Among those who had an instrumented level at L1-L3, there was no significant association between PUIVI central sarcopenia and length of postop opioid use (p=0.272) nor significant correlation with length of postop opioid use (p=0.136, Pearson correlation = -0.129). For those with a UIV above L1, there was similarly no association between PL4VI central sarcopenia and length of postop opioid use (p=0.586) nor significant correlation with length of postop opioid use (p=0.293, Pearson correlation = 0.41).

Conclusion : Central sarcopenia was not found to be significantly associated with or correlated to postoperative opioid use; this may be secondary to the multiple etiologies and mechanisms of pain, which include tissue trauma, neural structures manipulation, inflammation, etc. Our study suggests that muscle quality does not substantially contribute to post-operative pain and opioid consumption.