Flanigan, Patrick

OBJECTIVE Glucagon-like peptide-1 (GLP-1) agonists are established therapeutics for weight loss that are increasingly used for BMI optimization prior to spine surgery. However, emerging evidence has suggested that GLP-1 agonists might reduce bone mineral density (BMD), increasing the risk of postoperative biomechanical complications. CT-based Hounsfield units (HUs) have gained popularity as a method for measuring spinal BMD. The aim of this study was to evaluate the effects of GLP-1 agonist–induced weight loss on spinal BMD as measured by opportunistic CT-based HUs. METHODS Patients who were treated with any GLP-1 agonist (2017–2022) for > 3 months were retrospectively identified. Patient body weight (BW), BMI, and HU measurements in the L1 vertebral body were measured before and after GLP-1 therapy. Patients were grouped according to the percentage of weight loss during GLP-1 therapy. One-way ANOVA was used to compare the mean changes in spinal HUs across the groups. RESULTS Among the 102 included patients, the mean ± standard error of the mean BW reduction was 14.5 ± 2.5 kg over 15.9 ± 1.2 months of GLP-1 agonist therapy. Of these, 7 patients (6.9%) lost > 20% BW (mean decrease of 31.9 ± 7.0 HU, p = 0.011), 14 (13.7%) lost 15%–20% BW (mean decrease of 19.1 ± 8.3 HU, p = 0.038), 14 (13.7%) lost 10%–15% BW (mean decrease of 12.2 ± 5.1 HU, p = 0.036), 24 (23.5%) lost 5%–10% BW (mean decrease of 15.7 ± 3.3 HU, p < 0.0001), 26 (25.5%) lost < 5% BW (mean decrease of 14.7 ± 6.0 HU, p = 0.022), and 17 (16.7%) gained BW during GLP-1 therapy (mean decrease of 6.3 ± 5.0 HU, p = 0.229). One-way ANOVA testing did not show a significant difference in HU reduction across the weight loss groups (F = 1.12, p = 0.355). In addition, there was a significant correlation between the decrease in L1 HUs and the duration of GLP-1 therapy (r = −0.38, p = 0.0001) but not the amount of weight loss (r = −0.18, p = 0.070). In the multivariate analysis, the duration of GLP-1 therapy (p = 0.032) was a significant independent predictor of vertebral HU reduction, but the amount of weight loss (p = 0.664) was not. CONCLUSIONS Despite similar pretreatment BW and HU measurements, all weight loss groups had significant decreases in vertebral HUs following GLP-1 agonist therapy, with a significant correlation observed between HU reduction and treatment duration. This suggests that long-term GLP-1 agonist therapy can significantly diminish spinal BMD regardless of the amount of weight loss achieved.

OBJECTIVE The authors sought to determine how the temporal proximity of lumbar epidural spinal injection prior to surgery impacts clinical outcomes (e.g., 30-day readmission, postoperative complications, CSF leak) in patients undergoing lumbar decompression without fusion. METHODS The authors queried their institutional registry to identify patients who underwent elective lumbar decompression for spondylotic pathology between January 2019 and March 2022 at multiple centers within the same hospital network. Patients were divided into groups based on the time between their surgical date and the most recent preoperative spinal injection: group 1, patients with duration < 1 month; group 2, 1–3 months; and group 3, no spinal injection within 3 months. Primary outcomes of interest were the length of hospital stay, postoperative complications, rate of intraoperative CSF leak, and rates of reoperation and hospital readmission. For patients in groups 1 and 2, the authors also recorded the number of injections within 12 months prior to surgery to better understand the effect of multiple recent injections. The independent Student t-test and Pearson’s chi-square test were mainly performed for univariate analyses of the continuous and categorical variables, respectively. RESULTS A total of 121 and 283 patients received a spinal injection at < 1 month and 1–3 months prior to surgery, respectively, and were separately matched in a 3:1 ratio with 2562 patients with no history of preoperative spinal injection within 3 months before surgery. Among the matched cohorts, patients who received spinal injections < 1 month before lumbar decompression had significantly higher risks of 30-day complication (7.4% vs 0.8%, OR 9.6, p < 0.001), 30-day readmission (5.8% vs 2.2%, OR 3.5, p = 0.049), and 90-day readmission (9.1% vs 2.8%, OR 3.5, p = 0.003) than patients with no history of spinal injection. However, compared with patients with no history of spinal injection, the patients who received spinal injections 1–3 months before surgery were not at higher risk for postoperative complications or readmission. The CSF leak rates were significantly different between the three patient cohorts (10.7% vs 6.7% vs 4.9% for the < 1 month, 1–3 months, and no injection cohorts, respectively; p = 0.02). CONCLUSIONS Lumbar decompression within 1 month of preoperative spinal injection was associated with higher risks of readmission and postoperative complications, including CSF leak. However, with the exception of CSF leak, these risks were no longer observed when spinal injection occurred 1–3 months prior to lumbar decompression.