Background: Dysfunction and weakness due to atrophy of the paraspinal muscles is a major issue after posterior spinal fusion (PSF) surgery, resulting in pain and disability. Considering the role of protein in muscle regeneration, it seems that protein supplements after surgery may prevent muscle atrophy. To date, to our knowledge, no intervention study has investigated the effect of protein supplementation on the volume of paraspinal muscles, pain, or disability after PSF.Methods: In this randomized, double-blind, placebo-controlled clinical trial, patients were randomly assigned to a control (placebo þ diet with 1.2 g/kg body weight of protein, n ¼ 40) or a protein supplementation (36 g/day þ a diet with 1.2 g/kg body weight of protein, n ¼ 40) group, which received intervention from 48 hours before to 1 month after surgery. The cross-sectional area (CSA) of the paraspinal muscles was measured by thin-slice computed tomography, and pain and disability were assessed using the visual analog scale and Oswestry Disability Index.Results: After 4 weeks of protein supplementation, the CSAs of multifidus and psoas muscles on both sides were significantly higher in the supplementation group than the placebo group (P ,.001). Less atrophy was seen in the right erector spinae and quadratus lumborum muscles in the group receiving protein supplements than the placebo group (P , .001). In addition, protein supplementation was significantly negatively correlated with both pain (P , .001) and disability (P , .001).Conclusions: In conclusion, we demonstrated that 36 g/day protein supplementation significantly increased the CSA of muscles and reduced the atrophy, pain, and disability after PSF surgery.

Objectives: Vitamin D plays a major role in bone metabolism, regulating calcium and phosphorus homeostasis, along with bone growth and remodeling processes. The objective of the present study was to assess the effect of vitamin D deficiency on clinical outcomes following elective spinal fusion surgery by conducting a meta-analysis on the relevant literature.Methods: Studies included in this analysis involved patients older than 18 years who underwent elective spinal fusion surgery. The number of patients as well as visual analog scale (VAS) and Oswestry Disability Index (ODI) in groups with and without vitamin D deficiency were required to be reported in eligible studies. Of the 179 articles identified, 7 met the inclusion criteria and were included in the analysis.Results: Seven studies, including 1188 patients, reported the relationship between vitamin D deficiency and clinical outcomes in patients undergoing elective spinal fusion surgery. Five studies reported VAS as a primary outcome. The combined results using a random-effects model showed reduction in VAS after elective spinal fusion surgery in group with vitamin D deficiency, but no statistically significant association was identified between vitamin D deficiency and VAS. ODI was assessed and reported as an outcome measure in 5 of the included studies. The combined results showed an increase in ODI following elective spinal fusion surgery in the vitamin D-deficient group compared to the group with normal levels of vitamin D. In addition, a significant association was observed between ODI and vitamin D deficiency.Conclusions: Vitamin D deficiency may negatively affect the postoperative outcomes in elective spinal fusion surgery. Preoperative optimization of vitamin D levels would seem appropriate. Future high-quality studies are highly warranted to evaluate this.Clinical Relevance: This meta-analysis demonstrated a significant association between vitamin D deficiency and postoperative ODI scores in patients undergoing elective spinal fusion surgery.