Qualitative Evaluation of Paraspinal Musculature after Minimally Invasive Lumbar Decompression: A Prospective Study

BACKGROUND:To quantify fatty infiltration and degree of paraspinal muscle degeneration in patients submitted to tubular microdiscectomy and conventional open microdiscectomy. METHODS:A prospective cohort of patients was submitted to microdiscectomy for lumbar disc herniation after failure of conservative treatment. Selection of the technique was based on the surgeon's preference. Analysis of the multifidus muscle was performed using the Goutallier system and the percentage of fat in the muscle. Preoperative and 1-year postoperative T2-weighted magnetic resonance imaging was used, and statistical analysis was carried out using the Wilcoxon test and Spearman correlation test using a significance level of 5%. RESULTS:Thirty-two patients were included in the study. The percentage of fatty infiltration in the muscle increased on both sides of the spine 1 year after surgery, although only the ipsilateral side presented statistical significance in patients submitted to conventional microdiscectomy (43.3% preoperative and 57.8% postoperative). Muscular degeneration increased significantly ipsilateral to the disc herniation according to the Goutallier classification (grades 1-2) for both interventions. No statistically significant difference was found for fatty infiltration scores or for the degree of muscular degeneration of the multifidus in the comparative analysis of the methods. CONCLUSIONS:Muscular damage resulting from surgery of lumbar disc herniation significantly increases fatty infiltration and degeneration of the multifidus. Muscular degeneration was associated with worsening back pain. CLINICAL RELEVANCE:While no significant difference was found between the techniques, the tubular minimally invasive approach shows a tendency for less muscle damage. These findings highlight the importance of minimizing muscle injury during surgery to improve postoperative recovery and long-term outcomes. LEVEL OF EVIDENCE: 4: