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Partial Discectomy Helps Prevent Reherniation

Sometimes back surgery is like Pandora's box. It would be better left unopened. Once a person has had any kind of lumbar surgery, the risk of further surgery goes way up. Studies show almost a 10 per cent increase in rates of reoperation after lumbar surgery.

And it doesn't seem to matter what the patient's characteristics are or what the surgery was for -- the rates still apply. In this study, surgeons take a look over 25 years' worth of patients who had lumbar surgery. They wanted to single out one particular diagnosis and take a closer look.

Of the 1,100 charts reviewed, 259 had single-level lumbar discectomy (disc removal). The diagnosis was herniated nucleus pulposis (HNP). All patients included in the study had X-ray and MRI evidence of HNP. Back and leg pain (sciatica) were both present.

The procedure performed on each patient was a subtotal discectomy. A piece of bone was removed from the lamina. The lamina forms a roof-like structure over the back of the spinal canal. In this procedure, a thumbnail-sized piece of the lamina is removed (laminectomy). Sometimes a hole is drilled in the lamina (laminotomy to extract the protruding disc.

After the lamina is removed, the surgeon cut a box-shaped hole in the outer covering of the disc (anulus. Any loose disc material was removed without taking any of the anulus or the endplates. Endplates are tough, fibrous material sandwiched between the anulus of the disc and the vertebral bone.

Two independent reviewers classified each disc. They read the surgeon's notes and reviewed X-ray reports and any other available records. A four-part system called the Carragee classification was used to label each disc as type 1, 2, 3, or 4.

Type 1
was a small fragment of disc or fissure (crack) in the disc covering. Type 2 was described as a disc fragment with annular defect. Type 3 was a fragment contained. Type 4 was no fragment/contained. Any cases of disc hardening or calcification were put in the Type 4 subgroup.

The Carragee system basically groups disc herniations based on whether or not disc material has protruded and how far out of the annular covering it has moved. Surgery can then be directed to remove any disc fragments and repair the defect in the annulus.

This study used the Carragee classification scheme to determine the success of a subtotal discectomy. The results showed a lower rate of failure and reoperation for HNP using partial or subtotal discectomy. The success rate was most noticeable with type 2 herniations. There was a 3.4 per cent reoperation rate using subtotal discectomy versus a 21.2 per cent for fragment excision.

The authors attribute their success to a difference in surgical technique. They used an aggressive method of disc removal. A special Loupe magnification made it possible to cut off or shave the spinous processes and interspinous processes. Then a laminotomy was done. The disc was removed from within the annular covering. Their discectomy patients had a lower rate of reoperation but more back pain and lower function compared with those who had just removal of loose disc fragments.

Many questions still remain after this study. First, Why is the reoperation rate lower with subtotal discectomy? Was it really the surgical technique that made a difference in outcomes? Second why does back pain occur more often after subtotal discectomy compared with fragment excision?

For now, it appears that subtotal discectomy works well and reduces reherniation rates. More study is needed to ensure low reherniation and reoperation rates. The authors also proposed making a Type 5 Carragee subgroup. Calcified or hard disc protrusion is not included in the current four subtypes. This study showed that calcified discs can reherniate and should be included in the classification.

Glenn S. Wera, MD, et al. Reherniation and Failure After Lumbar Discectomy: A Comparison of Fragment Excision Alone Versus Subtotal Discectomy. In Journal of Spinal Disorders & Techniques. July 2008. Vol. 21. No. 5. Pp. 316-319.


*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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