Timing Discectomy for Disc Herniation Sciatica
Most sciatica from a lumbar disc herniation improves without an operation, so the timing of discectomy decides how long a patient lives with leg pain and whether they undergo surgery they may never have needed.
Key terminology
- Nucleus pulposus
- This gel core sits in the center of each intervertebral disc, held in by the tough outer annulus fibrosus. A herniation is nucleus escaping through a tear in the annulus.
- Sequestration
- This herniated fragment has broken free of the parent disc. An extrusion is still attached through a narrow neck, and a protrusion has a broad base.
- Traversing nerve root
- This nerve root crosses a disc on its way to exit one level lower, so the L4-5 disc touches the L5 root. A posterolateral herniation compresses it.
- Straight leg raise (SLR)
- This exam lifts the straight leg of a supine patient to stretch the L5 and S1 roots. A crossed SLR is positive when lifting the painless leg reproduces pain in the affected leg.
- Microdiscectomy
- This operation removes the herniated fragment through a small incision under a microscope. It decompresses the nerve root and leaves most of the disc in place.
- Crossover
- Patients switch from their assigned treatment to the other arm of a trial. Heavy crossover shrinks the measured difference between arms.
- Intention-to-treat analysis
- This analysis compares patients by the arm they were randomized to, whatever treatment they received. An as-treated analysis groups them by what they received and loses the protection of randomization.
Takeaways
- Sequestered disc fragments regress on their own in 96% of cases and extrusions in 70%. Protrusions regress in 41% and bulges in only 13%. The more nucleus pulposus that escapes the annulus, the more likely it is to resorb, with complete resolution in 43% of sequestrations. A large herniation on MRI can still shrink without surgery. (Chiu et al, Clin Rehabil 2015;29:184-195, PMID 25009200).
- Disc protrusions appear on MRI in 29% of pain-free 20 year olds and 43% of pain-free 80 year olds. Disc bulges rise from 30% to 84% over the same ages. An MRI finding is read against the exam, and the compressed traversing nerve root should fit the patient's dermatome, weakness and reflex changes. (Brinjikji et al, AJNR Am J Neuroradiol 2015;36:811-816, PMID 25430861).
- The straight leg raise has a pooled sensitivity of 0.92 and specificity of 0.28 for disc herniation. The crossed straight leg raise flips that profile, with specificity 0.90 and sensitivity 0.28. A negative SLR makes a herniation less likely, and a positive crossed SLR makes it more likely. Most of these data come from surgical populations and may not apply to primary care. (van der Windt et al, Cochrane Database Syst Rev 2010;CD007431, PMID 20166095).
- Early microdiscectomy at 6 to 12 weeks of sciatica relieved leg pain faster, and 1-year recovery was 95% in both arms. The Leiden-Hague trial randomized 283 patients, and 39% of the conservative arm had surgery at a mean of 18.7 weeks. Disability scores did not differ over the first year. A systematic review found the same pattern of faster relief and no difference at 1 and 2 years. (Peul et al, N Engl J Med 2007;356:2245-2256, PMID 17538084; Jacobs et al, Eur Spine J 2011;20:513-522, PMID 20949289).
- At 5 years the Leiden-Hague arms still did not differ, and 46% of the conservative arm had needed surgery. Weber's 1983 randomized trial showed the same curve, with surgery better at 1 year and no significant difference at 4 years. Waiting spares about half of patients an operation, at the cost of more weeks of leg pain for those who have it anyway. (Lequin et al, BMJ Open 2013;3:e002534, PMID 23793663; Weber, Spine 1983;8:131-140, PMID 6857385).
- In SPORT only 50% of patients randomized to surgery had it within 3 months, and 30% randomized to nonoperative care had surgery. The intention-to-treat analysis showed small, nonsignificant differences favoring surgery, and the authors called the trial inconclusive. The 8-year as-treated analysis favored surgery (Oswestry change -36.2 vs -24.8), though as-treated groups are no longer randomized. (Weinstein et al, JAMA 2006;296:2441-2450, PMID 17119140; Lurie et al, Spine 2014;39:3-16, PMID 24153171).
- For sciatica lasting 4 to 12 months, microdiscectomy lowered 6-month leg pain to 2.8 of 10 vs 5.2 of 10 with continued nonoperative care. The single-center trial randomized 128 patients, and 34% of the nonoperative arm crossed over at a median of 11 months. It supports offering surgery once sciatica has persisted for months, though no multicenter trial has yet confirmed it. (Bailey et al, N Engl J Med 2020;382:1093-1102, PMID 32187469).