gms | German Medical Science

Objective: Lumbar disc herniation (LDH) is a common cause of lower back and radiating leg pain.1 In most patients the natural course is favorable, and the international consensus is that surgical treatment is offered if the radiating pain persists despite a period of conservative treatment.2 Still, the condition is a major contributor to the global burden of disease and the most frequent indication for spinal surgery. Lumbar microdiskectomy is currently the most common surgical treatment for LDH,3 but data on surgical outcomes in the elderly are limited. The aim of this study was to compare patient-reported outcomes (PROM) following lumbar microdiskectomy in patients at least sixty-five years of age with younger patients.

Methods: Data were collected through the Norwegian Registry for Spine Surgery (NORspine), a comprehensive registry for quality control and research.4 Patients were eligible if they had a primary diagnosis of LDH and underwent non-emergency single-level lumbar microdiscectomy between 2007 and 2013. Patients were excluded who had undergone previous lumbar spine surgery or had coexisting spondylolisthesis or scoliosis. The primary outcome was change in disease specific functional outcome between baseline and 12 months’ follow-up measured with the Oswestry disability index version 2.0 (ODI).5 ODI is scored from 0–100, where zero means no disability and 100 reflects maximum disability. Secondary outcome measures were changes in health related quality of life, measured with the Euro-Qol-5D (EQ-5D), changes in low back pain and leg pain measured with numeric rating scales (NRS), surgical complications, and length of hospital stays. Patients completed the questionnaires on admission for surgery and after three and 12 months.

Results: There were 5195 patients <65 years and 381 patients ≥65 years. Baseline characteristics are presented in Table 1 [Tab. 1]. Loss to follow-up at one-year was 30.9% for the whole population, and 16.5% (n=63) in patients ≥65 years and 31.9% (n=1658) in patients <65 years (p<0.001). For all patients there was a significant improvement in ODI (difference 31.04 points, 95% CI 30.34, 31.74, p<0.001). Surgical outcomes are presented in Table 2 [Tab. 2]. There were no differences between age cohorts in mean changes of ODI (p=0.372), EQ-5D (p=0.929), or leg pain NRS (p=0.162), but elderly patients experienced more improvement in back pain NRS at 12 months (p=0.035). To manage missing data at 12 months, we used mixed linear model analyses and found similar results for all PROMs. At 12 months 84.2% of patients ≥65 years had achieved a minimal clinically important difference (≥10 points improvement in ODI), compared to 83.8% of younger patients (p=0.835). Patients ≥65 years experienced both more perioperative complications (4.2% vs 2.3%, p=0.019) and complications occurring within 3 months of hospital discharge (12.4% vs 5.4%, p<0.001), mainly due to more unintentional durotomies (2.9% vs 1.3%, p=0.015) and urinary tract infections (4.2% vs 1.3%, p<0.001). Younger patients had shorter hospital stays than patients ≥65 years (2.7 vs 1.8 days, p<0.001).

Discussion: Although they had minor complications and longer hospital stays, individuals aged 65 and older experienced improvement after lumbar microdiskectomy that was similar to that of younger individuals. Age alone should not be a contraindication to surgery, as long as the individual is fit for surgery.

The strengths of this study were the use of prospective registry data with high external validity and the large sample size. Still, the two age cohorts are not balanced for all baseline and treatment factors as spinal degeneration and comorbidity increase with age. The main limitation was the loss to follow-up of 30.9% at one year. A previous study on a similar population from NORspine showed no difference in outcomes between responders and non-responders.

Acknowledgements: We thank the Norwegian Registry for Spine Surgery (NORspine). The registry receives funding from the University of Northern Norway and Norwegian health authorities. We thank all patients and spine surgeons who participate in NORspine registration.

Author Contributions: Dr Gulati had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Gulati, Madsbu

Acquisition, analysis, or interpretation of data: Madsbu, Solberg, Salvesen, Nygaard, Gulati

Drafting of the manuscript: Madsbu, Gulati

Critical revision of the manuscript for important intellectual content: Solberg, Salvesen, Nygaard

Statistical analysis: Madsbu, Salvesen, Gulati

Obtaining funding: Gulati

Administrative, technical, or material support: Solberg

Study supervision: Gulati