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Preserving the ligamenta flava as much as possible is beneficial in lumbar microdiscectomy
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April 2014
Preserving the ligamenta flava as much as possible is beneficial in lumbar microdiscectomy
Study Type:Randomized Trial
OE Level Evidence:2
Journal Level of Evidence:N/A
Clinical assessment of reformed lumbar microdiscectomy
Eur J Orthop Surg Traumatol. 2014 Jan;24(1):23-7. doi: 10.1007/s00590-012-1123-8. Epub 2012 Nov 24Did you know you're eligible to earn 0.5 CME credits for reading this report? Click Here
Synopsis
97 patients with unilateral lumbar disc herniation were randomized to undergo lumbar microdiscectomy using either a traditional (control) or revised (test) technique, which focused on preserving as much of the ligamentum flavum as possible. The purpose of this study was to compare these two surgical approaches with respect to operative time, blood loss, pain and function. Results indicated that, although there were no significant differences between groups with respect to leg pain, operative time or blood loss, the test group yielded significantly better Oswestry scores at 12 weeks and 1 year post-operation. The revised procedure also resulted in significantly lower back pain scores at 3 days and 12 weeks postoperatively, however this significance was not maintained at 1 year. Both procedures were demonstrated to be safe, with no reports of reherniation, re-operation or infection.
Publication Funding Details
+
Funding:
Not Reported
Conflicts:
None disclosed
Was the allocation sequence adequately generated?
Was allocation adequately concealed?
Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?
Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?
Blinding Patients: Was knowledge of the allocated interventions adequately prevented?
Was loss to follow-up (missing outcome data) infrequent?
Are reports of the study free of suggestion of selective outcome reporting?
Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?
Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?
Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?
Yes = 1
Uncertain = 0.5
Not Relevant = 0
No = 0
The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.
1/4
Randomization
2/4
Outcome Measurements
1/4
Inclusion / Exclusion
4/4
Therapy Description
3/4
Statistics
Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.
Why was this study needed now?
Lumbar microdiscectomy was first introduced for the surgical treatment of herniated discs, due to its ability to result in a shorter incision and less trauma, bleeding and postoperative pain compared to classic surgical procedures. Today, this less-invasive technique is considered to be standard for patients with this condition and for whom conservative treatment is unsuccessful. This procedure, however, is continuously being revised in hopes of sparing the ligamentum flavum, as well as to address any drawbacks with current techniques of ligamentum flavum preservation. This study was needed to evaluate the clinical outcomes associated with a revised lumbar microdiscectomy procedure, where only the ligamentum flavum that affected surgical exposure (or that may cause disease later on) was removed.
What was the principal research question?
Is a reformed lumbar mircodiscectomy procedure - where only the ligamentum flavum that affected surgical exposure (or that may cause disease later on) was removed - clinically efficacious when compared to traditional lumbar microdiscectomy and assessed over 1 year postoperatively?
Study Characteristics
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Population:
97 patients with unilateral lumbar disc herniation (85 of which were included in the analysis) scheduled to undergo first-time lumbar surgery. All procedures were performed without the use of drainage.
Intervention:
Reformed lumbar microdiscectomy (test group): Patients in this group (n=44) underwent a similar surgical procedure as those in the control group, however with the following modifications: (1) the lumbodorsal fascia was dissected via a curved incision and turned towards the healthy side, and (2) only the lateral portion of the ligamentum flavum was removed (leaving at least 1/2 of the original ligamentum flavum). Furthermore, although the ligamentum flavum in front of the facet was removed as much as possible, emphasis was placed on preserving the parts that did not affect the visual field of the operation. (Age range: 22-58 years; 29 males, 15 females).
Comparison:
Traditional lumbar microdiscectomy (control group): Patients in this group (n=41) underwent standard lumbar microdiscectomy. Following dissection of the fascia along the supraspinous ligament, the paraspinal muscles were cut, and 2-4 mm of the L4 lamina (the caudal portion) was removed, leaving pure parenchyma tissue at the L5-S1 level. All of the ligamenta flava was removed for optimal exposure. Then, the nucleus pulposus on the affected side was extracted until the nerve root could be moved freely more than 0.5-1.0 cm. (Age range: 24-59 years; 25 males, 16 females)
Outcomes:
Outcomes included postoperative pain on a Visual Analog Scale (VAS) and lumbar function on the Oswestry scale.
Methods:
RCT; Single Centre
Time:
Assessments were conducted for both outcomes at 12 weeks and 1 year postoperatively. In addition, pain was assessed 3 days post-operation.
What were the important findings?
- Surgical time was 46 +/- 25 minutes in the test group and 42 +/- 20 minutes in the control group, and blood loss was 50 mL in both groups.
- Although significant improvements were observed in both groups, patients in the test group displayed significantly better VAS low back pain scores compared to the control group at 3 days (1.8 vs 3.8) and 12 weeks post-operation (1.3 vs 3.5) (both p<0.05). The difference between groups at 1 year was not statistically significant (test group: 1.9 points; control group: 2.8 points; p>0.05).
- There was no significant difference in VAS leg pain between groups at either 3 days (test group: 2.3; control group: 2.1), 12 weeks (test group: 1.9; control group: 2.0), or 1 year (test group: 1.8; control group: 1.7) post-operation (all p>0.05).
- Although significant improvements were observed in both groups, Oswestry scores were significantly better in the test group versus the control group at 12 weeks (18.2 vs. 34.4) and 1 year (12.0 vs. 22.6) post-operation (both p<0.05).
- There was no incidence of recurrent disc herniation, re-operation, wound infection, or intervertebral gap infection in either group.
What should I remember most?
Although there was no significant difference between groups with respect to leg pain, operative time or blood loss, the revised lumbar microdiscectomy procedure yielded significantly better Oswestry scores at 12 weeks and 1 year post-operation compared to the traditional lumbar microdiscectomy for patients with disc herniation. The revised procedure also resulted in significantly lower back pain scores at 3 days and 12 weeks postoperatively. Both procedures proved to be safe, with no reports of recurring disc herniation, re-operation or infection.
How will this affect the care of my patients?
Results from this study suggest that a revised lumbar microdiscectomy procedure, where the ligamenta flava is preserved as much as possible, may be more beneficial than the traditional procedure, especially with respect to lumbar function and back pain. Future studies should compare these two procedures using larger sample sizes, longer follow-up periods, and more rigorous assessment of outcome.
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