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Keywords
Sciatica
Lumbar Microdiscectomy
Lumbar Microendoscopic Discectomy
Lumbar Discectomy
Lumbar Laminectomy
Herniated Lumbar Disc

Definition
A lumbar herniated disc involves displacement of the nucleus (inner part of the disc) through the annulus (outer boundary of the disc) into the spinal canal.

Indications
The operations for herniated disc are indicated for the relief of leg pain, leg numbness, and/or leg weakness from pressure on a single lumbar nerve root or multiple lumbar nerve roots. Occasionally, lumbar disc herniations place pressure on the nerves to the bowel and bladder requiring urgent surgery.

The table below illustrates the findings associated with a single nerve root in the lumbar spine.

Technical Considerations
The goal of disc surgery is the removal of the mechanical pressure on the lumbar spinal nerve. Different surgical options are available to the patient.

Literature Review
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Natural History
The natural history of the lumbar herniated disc is listed in the table below. The natural history is the percentage patients of resolving symptoms from the herniated disc measured against the time from the onset of those symptoms. (reference #9)

Timing of Surgery
The best results in lumbar disc surgery occur when surgery is performed within 2 to 3 months of the onset of symptoms. (reference #6, #7) The exception would be patients with cauda equina syndrome (loss of control of bowel and bladder) and those patients with progressive weakness in the leg or legs.

Crossover: Natural History and Surgical Timing
Since most people improve in the first three months and surgical results are optimized at 3 months, the decision regarding surgery is best determined by this time.

Levels of Herniation and Symptoms
The most common levels in the lumbar spine for the herniated disc are shown in the table below from a large surgical series. Because most herniated discs occur at the two lowest levels in the lumbar spine, the most common symptoms involve the nerves forming the sciatic nerve. Sciatica is the most common symptom presentation of the lumbar herniated disc.

Degree of Herniation and Surgical Success
Although there is no accurate measurement of the size of the herniated disc and the result of surgery by MRI scan, intra-operative measurements have been related to the results of surgery. Sprangfort concluded "The degree of herniation was the single most important factor in surgical relief of sciatica and the incidence of persistent back pain." (reference #8) The table below lists his intra-operative observations and results of surgery. (reference #8)

It should be noted that small herniations in association with less space available in the spinal canal (lateral recess stenosis, foraminal stenosis, central stenosis) may have the same effect of significant mechanical pressure on the nerve and surgical intervention with this group is often successful. Sprangfort related the relief of leg pain, which is the goal of surgery, to persistent low back pain. (reference #8)

Sprangfort refuted the concept that a bulging disc was the precursor to the future disc herniation. (reference #8)

Clinical Correlation and Surgery
Clinical correlation is taking the attributes of the patient and the tests and seeing if there is a fit for a particular diagnosis. More than one factor determines the outcome of surgery, not just the finding of an MRI scan. One study examined four factors: neurologic signs, sciatic signs, personality factors, and imaging studies. None of the factors by itself predicted HNP but when all 4 were combined, there was a 96% accuracy for predicitng compression of the lumbar spinal nerve. (reference #5)

What does Surgery Effect
A long term study with 10 year follow-up revealed that surgery was optimal for leg pain. (reference # 7) Muscle weakness (significant weakness was operated on so no control group truly existed) but there was no difference between surgery and nature for numbness, reflex changes, minor weakness, straight leg raising test (raising the leg producing nerve pain in the leg) and range of motion (the ability to bend the spine). Essentially, this study confirmed that those patients who underwent surgery were not at a disadvantage compared to those who were able to reslove their symptoms with non-operative treatment when reviewed at the 10 year follow-up. If the 26% of patients who were initially randomized to the conservative care group (subsequently operated on for pain) were included in the statistics related to conservative care at 10 years and 4 years, then the results of surgery would be superior at the 4 and 10 year review. (reference # 3, #7) The percentage of patients improved were greater in the surgery group compared to the conservative group at 1 year. (reference #3, #7)


Surgery versus Degree of Symptoms
An excellent study related the degree of symptoms (severe, moderate, mild) to the choice of surgery for herniated lumbar disc.(reference # 1) Severe symptoms were almost always operated on and mild symptoms rarely operated on. 50% of patients with moderate symptoms chose surgery and 50% chose not to have surgery. At the conclusion of the study at 1 year, 71% of patients with surgery were definitely improved, compared to 43% in the non-operative group. (reference # 2) More recently, this group was evaluated at 5 years with the following results:
"Surgically treated patients had more severe symptoms and worse functional status at baseline and better outcomes at 5-year follow-up compared with nonsurgically treated patients." (reference #1)

Complications
The risks of lumbar disc surgery are death, paralysis, infection, wound problems, nerve root injury, spinal fluid leak, failure to improve, future instability.

Author’s Comment
The best indications for surgery for the lumbar herniated disc are loss of control of the bowel and bladder (rare), weakness in an important muscle in the leg, and leg pain due to nerve pressure. In the final analysis, the choice for surgery is related to the degree of patient disability from the symptoms of herniated disc matched to the anatomy causing the symptoms. Once this principle is established, the choice of operative technique is made.

References
1. Atlas, S.J., "Surgical and Nonsurgical Management of Sciatica Secondary to a Lumbar Disc Herniation. Spine, 2001. 26(10): p. 1179-1187.
2. Atlas, S.J., et al., The Main Lumbar Spine Study, Part II. 1-year outcomes of surgical and nonsurgical management of sciatica. Spine, 1996. 21(15): p. 1777-86.
3. Weber, H., Spine Update: The Natural History of Disc Herniation and the Influence of Intervention. Spine, 1994. 19(19): p. 2234-2238.
4. Hurme, M.A., H et al:, A prospective study of patients with sciatica. A comparison between conservatively treated patients and patients who have undergone operation, Part I: Patient characteristics and differences between groups. Spine, 1990. 15(2): p. 1340-1344.
5. Spengler, D.O., EA Battie et al., Elective discectomy for herniation of a lumbar disc. Additional experience with an objective method. JBJS, 1990. 72(2): p. 230-237.
6. Hurme M, A.H., et al:, Factors predicting the result of surgery for lumbar intervertebral disc herniations. Spine, 1987. 12: p. 933-938.
7. Weber, H., Lumbar disc herniation: A controlled prospective study with ten years of observation. Spine, 1983. 8: p. 131-140.
8. Sprangfort, E., The lumbar disc herniation: A computer-aided analysis of 2504 operations. Acta Orthop Scand (suppl), 1972: p. 142.
9. Hakelius, A., Progress in sciatica. ACTA Orthop Scand, 1970(129): p. 6-76.