Extraforaminal versus central lumbar disc herniations: clinical features and surgical outcome comparing data from a national spine registry (NORspine)

BACKGROUND CONTEXT: Previous studies indicate that extraforaminal disc herniations (EDH) tend to have a more acute onset and more pronounced radicular symptoms. Surgical outcomes for lateral disc herniations remain somewhat heterogeneous in the literature when compared with central disc herniations (CDH). PURPOSE: We aim to compare clinical features and surgical outcomes between extraforaminal and central disc herniations. DESIGN: Retrospective analysis of prospectively collected data from the Norwegian Spine Registry (NORspine) PATIENT SAMPLE: 11,341 patients were registered during the study period. We included 10,288 patients: 10,159 with CDH and 229 with EDH. Propensity score matching resulted in two groups of 214 patients each. OUTCOME MEASURES: The primary outcome was the Oswestry Disability Index (ODI) score at three and twelve months postoperatively. Secondary outcomes were success at three and twelve months postoperatively, defined as ODI < 22, a Global Perceived Effect (GPE) rating of "much improved" or "completely recovered", Numeric Rating Scale (NRS) for back and leg pain (0-10), as well as patient satisfaction, perioperative and postoperative complications. METHODS: Patient groups were defined based on reported MRI findings, categorising cases as either CDH or EDH. We used Patient-Reported Outcome Measures (PROMs) derived from NORspine, specifically ODI, NRS back and leg pain and GPE, as well as surgical details, and clinical outcomes at 3 and 12 months, and recorded complications. To adjust for baseline differences between the groups, propensity score matching was used. RESULTS: Patients in the EDH group were older (57.1 vs. 46.7 years), had higher preoperative ODI scores (49.5 vs. 46.6), and reported higher NRS scores for both leg pain (7.4 vs. 7.1) and back pain (7.0 vs. 6.5). At the three-month follow-up, patients with EDH had higher ODI scores (21.9 vs. 17.1; p < 0.001), higher NRS leg pain (3.1 vs. 2.3; p < 0.001), and higher NRS back pain (3.5 vs. 2.9; p < 0.001). At the 12-month follow-up, group differences had narrowed but remained statistically significant for ODI and NRS leg pain. Following propensity score matching, preoperative PROM differences were no longer statistically significant. NRS leg and back pain remained slightly worse in the EDH group at 3-month follow-up (3.0 vs. 2.3; p = 0.011; 3.5 vs 2.6; p < 0.001). At 12- month follow-up, there was no statistically significant difference in PROMs between groups (ODI 18.9 vs 17.4; NRS leg pain 3.0 vs 2.4; NRS back pain 3.0 vs 3.1). Surgical duration was longer for EDH procedures (75.9 vs. 58.0 minutes), although perioperative complications were less common in the EDH group (0.4% vs. 1.4%). The proportions of patients reporting satisfaction at 3 and 12 months were similar across groups and did not differ significantly. CONCLUSIONS: Patients with extraforaminal lumbar disc herniation experience substantial benefits from surgical intervention, including meaningful improvements in PROMs, comparable treatment success and patient satisfaction rates to those with central lumbar disc herniation.