Abstract
This study compares patient-reported outcomes following lumbar microdiskectomy among patients at least 65 years of age vs younger patients.
For most patients, the natural course of a herniated lumbar disk is favorable, and the consensus is that surgical treatment is offered if the pain in the lower back and radiating down the legs persists despite a period of conservative treatment. Lumbar microdiskectomy is the most common surgical treatment, but data on surgical outcomes among elderly patients are limited. The aim of this study was to compare patient-reported outcomes following lumbar microdiskectomy among patients at least 65 years of age vs younger patients.
Methods
Data were collected through the Norwegian Registry for Spine Surgery (NORspine), a comprehensive registry for quality control and research. Approximately 65% of all patients who undergo lumbar spine surgery in Norway are included in NORspine. The regional committee for medical research approved this study, and all participants provided written informed consent. Patients were eligible if they had a primary diagnosis of lumbar disk herniation and underwent a nonemergency single-level lumbar microdiskectomy between 2007 and 2013. Patients who had undergone previous lumbar spine surgery or had a coexisting spinal deformity were excluded.
On admission, the patients completed the baseline questionnaire, including patient-reported outcomes, demographics, and lifestyle issues. The primary outcome was change in disease-specific functional outcome between baseline and 12 months’ follow-up measured with the Oswestry Disability Index (ODI) version 2.0. The ODI is scored using a scale from 0 to 100, with increasing values reflecting more disability. A minimal clinically important change for the ODI is approximately 10 points. Secondary outcome measures were changes in health-related quality of life, measured with the EQ-5D, a standardized instrument for use as a measure of health outcome from the EuroQol Research Foundation; changes in low back pain and leg pain measured with numeric rating scales; complications; and length of hospital stays.
Missing data were handled with mixed linear models. This strategy was in line with a study showing that multiple imputations are not necessary before performing a mixed-model analysis on longitudinal data. Surgeons recorded comorbidity and perioperative complications. Microdiskectomy was performed by ipsilateral paravertebral muscle retraction and removal of the disk herniation by a unilateral transflaval approach. Patient questionnaires for 3- and 12-month follow-up were distributed and collected by NORspine. Patients reported complications within 3 months of hospital discharge. For statistical comparison tests, we defined the significance level as P ≤ .05.
Results
There were 5195 patients younger than 65 years of age and 381 patients 65 years of age or older. Baseline characteristics are presented in Table 1. Sixty-three of 381 patients 65 years of age or older (16.5%) and 1658 of 5195 patients younger than 65 years of age (31.9%) were lost to follow-up (P < .001). For all patients, there was a significant improvement in the ODI (−31.04 points [95% CI, −30.34 to −31.74 points]; P < .001). Surgical outcomes are presented in Table 2. There were no differences between age cohorts in mean changes of the ODI, the EQ-5D, or leg pain, but elderly patients experienced more improvement in low back pain.
Table 1. Demographic Characteristics, Coexisting Illnesses, and Measures of Health Status for Both Groups of Patients.
| Variable | Patients, No. (%) | P Value | |
|---|---|---|---|
| <65 y | ≥65 y | ||
| Total No. (%) | 5195 (93.2) | 381 (6.8) | |
| Age, median (range), y | 42.1 (18-64) | 70.9 (65-89) | <.001 |
| Female sex | 2097 (40.4) | 176 (46.2) | .03 |
| Married or partner | 3906 (75.2) | 286 (75.1) | .94 |
| Attended college | 2014 (38.8) | 126 (33.1) | .02 |
| Body mass index, mean | 26.6 | 25.7 | <.001 |
| Current smoker | 1530 (29.5) | 77 (20.2) | <.001 |
| Coexisting spinal stenosis in operated level | 541 (10.4) | 128 (33.6) | <.001 |
| Comorbidity | 959 (18.5) | 201 (52.8) | <.001 |
| Cardiovascular disease | 121 (2.3) | 78 (20.5) | |
| Cerebrovascular disease | 10 (0.2) | 11 (2.9) | |
| Vascular claudication | 3 (0.1) | 2 (0.5) | |
| Diabetes mellitus | 103 (2.0) | 31 (8.1) | |
| Chronic lung disease | 86 (1.7) | 22 (5.8) | |
| Hypertension | 194 (3.7) | 72 (18.9) | |
| Osteoporosis | 4 (0.1) | 4 (1.0) | |
| Knee and/or hip osteoarthritis | 22 (0.4) | 25 (6.6) | |
| Chronic neurologic disease | 29 (0.6) | 1 (0.3) | |
| Chronic musculoskeletal pain | 79 (1.5) | 10 (2.6) | |
| Cancer | 24 (0.5) | 8 (2.1) | |
| Rheumatoid arthritis | 15 (0.3) | 6 (1.6) | |
| Ankylosing spondylitis | 8 (0.2) | 0 (0) | |
| Other rheumatic diseases | 41 (0.8) | 9 (2.4) | |
| ASA grade >2 | 144 (2.8) | 80 (21.0) | <.001 |
| Preoperative mean ODI | 45 | 49.8 | <.001 |
| Preoperative mean EQ-5D | 0.28 | 0.24 | .02 |
| Preoperative diagnostic imaging | |||
| MRI | 5053 (97.3) | 365 (95.8) | .10 |
| CT | 244 (4.7) | 24 (6.3) | .16 |
Abbreviations: ASA, American Society of Anesthesiologists; CT, computed tomography; MRI, magnetic resonance imaging; ODI, Oswestry Disability Index.
Table 2. Outcomes at 1 Year for Patients Who Underwent Surgery for a Single-Level Herniated Lumbar Disk.
| Variable | Mean Value | Difference in Mean Change (95% CI) |
P Value | |||||
|---|---|---|---|---|---|---|---|---|
| Age <65 y (n = 3537) |
Age ≥65 y (n = 318) |
|||||||
| Baseline | 1 y | Mean Change | Baseline | 1 y | Mean Change | |||
| Complete case analyses (n = 3855) | ||||||||
| ODI | 45.3 | 14.3 | −30.9 | 50 | 17.8 | −32.1 | −1.2 (−3.7 to 1.4) |
.37 |
| EQ-5D | 0.28 | 0.77 | 0.48 | 0.25 | 0.73 | 0.48 | −0.002 (−0.06 to 0.05) |
.93 |
| Numeric rating scale | ||||||||
| Back pain | 6.1 | 2.6 | −3.4 | 6.7 | 2.9 | −3.8 | −0.4 (−0.8 to −0.03) |
.04 |
| Leg pain | 6.8 | 2.1 | −4.8 | 7.3 | 2.8 | −4.5 | 0.3 (−0.7 to 0.1) | .16 |
| Variable |
Age <65 y (n = 5195) |
Age ≥65 y (n = 381) |
Difference in Mean Change (95% CI) |
P Value | ||||
| Baseline | 1 y | Mean Change | Baseline | 1 y | Mean Change | |||
| Mixed linear model analyses (n = 5572) | ||||||||
| ODI | 45 | 14.5 | −30.5 | 49.8 | 18.3 | −31.5 | −0.96 (−3.2 to 1.3) |
.40 |
| EQ-5D | 0.28 | 0.76 | 0.48 | 0.24 | 0.72 | 0.49 | 0.01 (−0.04 to 0.05) |
.71 |
| Numeric rating scale | ||||||||
| Back pain | 6.1 | 2.7 | −3.4 | 6.7 | 2.9 | −3.9 | −0.4 (−0.8 to −0.1) |
.01 |
| Leg pain | 6.8 | 2.1 | −4.7 | 7.2 | 2.7 | −4.5 | −0.3 (−0.6 to 0.1) |
.11 |
| Variable | Patients, No./Total No. (%) |
Difference (95% CI) |
P Value | |||||
| Age <65 y | Age ≥65 y | |||||||
| Surgical treatments, complications, and events | ||||||||
| Mean operation time, min | 57.0 | 70.8 | −13.8 (−16.8 to −10.9) |
<.001 | ||||
| Hospital stay, mean, d | 1.8 | 2.7 | −0.9 (−1.1 to −0.7) |
<.001 | ||||
| Patients with complications | 306/5195 (5.9) | 51/381 (13.4) | <.001 | |||||
| Perioperative complications | 119/5195 (2.3) | 16/381 (4.2) | .02 | |||||
| Unintentional durotomy | 70/5195 (1.3) | 11/381 (2.9) | .02 | |||||
| Nerve injury | 11/5195 (0.2) | 2/381 (0.5) | .22 | |||||
| Blood replacement or postoperative hematoma | 17/5195 (0.3) | 1/381 (0.3) | .83 | |||||
| Cardiovascular | 4/5195 (0.1) | 1/381 (0.3) | .24 | |||||
| Respiratory | 2/5195 (<0.1) | 0/381 (0.0) | .70 | |||||
| Anaphylactic reaction | 6/5195 (0.1) | 0/381 (0.0) | .51 | |||||
| Wrong level of surgery | 9/5195 (0.2) | 0/381 (0.0) | .42 | |||||
| Patient-reported complications within 3 mo | 193/3551 (5.4) | 38/306 (12.4) | <.001 | |||||
| Wound infection | 96/3551 (2.7) | 11/306 (3.6) | .36 | |||||
| UTI | 46/3551 (1.3) | 13/306 (4.2) | <.001 | |||||
| Pneumonia | 12/3551 (0.3) | 4/306 (1.3) | .01 | |||||
| PE | 0/3551 (0.0) | 1/306 (0.3) | .001 | |||||
| DVT | 2/3551 (0.1) | 0/306 (0.0) | .68 | |||||
| Micturition problems | 50/3551 (1.4) | 13/306 (4.2) | <.001 | |||||
Abbreviations: DVT, deep vein thrombosis; ODI, Oswestry Disability Index; PE, pulmonary embolism; UTI, urinary tract infection.
Mixed linear model analyses showed similar results for all patient-reported outcomes. Among patients with complete 12-month follow-up, 268 of 318 patients 65 years of age or older (84.3%) and 2964 of 3537 patients younger than 65 years of age (83.8%) had achieved a minimal clinically important change in the ODI (P = .83). Compared with the patients younger than 65 years of age, the patients 65 years of age or older experienced more perioperative complications (16 of 381 [4.2%] vs 119 of 5195 [2.3%]; P = .02) and more complications occurring within 3 months of hospital discharge (38 of 306 [12.4%] vs 193 of 3551 [5.4%]; P < .001), mainly because they had more urinary tract infections, micturition problems, and unintentional durotomies. The patients younger than 65 years of age had shorter hospital stays than did the patients 65 years of age or older (2.7 vs 1.8 days; P < .001).
Discussion
Although the patients 65 years of age or older had more minor complications and longer hospital stays, they experienced improvements in their conditions after a lumbar microdiskectomy that were similar to those of the patients younger than 65 years of age. 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 2 cohorts of patients were not balanced for all baseline and treatment factors because spinal degeneration and comorbidity increase with age. Loss to follow-up at 1 year is a concern, but at a rate of only 16.5% in the patients 65 years of age or older, we demonstrate that older age should not be an exclusion criterion in surgical outcomes research. A previous study from NORspine showed no difference in outcomes between responders and nonresponders.
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