Preoperative paraspinal muscle fatty infiltration and prognosis after lumbar discectomy for disc herniation: a systematic review and meta-analysis

To examine the association between preoperative paraspinal muscle fat infiltration (FI) and adverse postoperative outcomes in adults with lumbar disc herniation (LDH) undergoing lumbar discectomy. This systematic review and meta-analysis followed PRISMA. Two reviewers independently searched PubMed, Embase, Web of Science Core Collection, and the Cochrane Library. We included observational studies of adults with imaging-confirmed LDH who underwent lumbar discectomy. Eligible studies assessed preoperative paraspinal FI using magnetic resonance imaging (MRI) and reported postoperative outcomes with effect estimates. Risk of bias was assessed using the Quality In Prognosis Studies (QUIPS) tool. For dichotomous outcomes, multivariable-adjusted odds ratios (ORs) were preferentially pooled using a random-effects model. Thirteen studies including 4,371 patients were included. More severe preoperative FI was associated with a higher risk of same-level recurrence or reoperation (6 studies; pooled OR = 2.77, 95% CI 1.65–4.67; I² = 60.0%). More severe FI was also associated with residual or chronic low back pain (6 studies; pooled OR = 3.70, 95% CI 2.72–5.04; I² = 16.7%). For functional outcomes (3 studies), patients with more severe FI had worse functional scores at final follow-up (pooled mean difference = 3.856, 95% CI: 1.015–6.697; I² = 47.8%). In adults with LDH undergoing lumbar discectomy, more severe preoperative paraspinal FI is associated with recurrence or reoperation, residual/chronic low back pain, and poorer functional recovery.