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Technical failures in spinal surgery

Failed surgery in the management of vertebral pain is one of the calamities of surgical science. There is seldom an opportunity to beneficially repeat spinal surgery. If repeated, surgery is likely to multiply and perpetuate the condition.

Spinal surgery fails for a number of reasons. The first is an incorrect diagnosis.  Paraxial (lower limb) pain can come from many sources. Limb pain is far from diagnostic of discogentic neuropathy, and will be addressed in another page.

Even when the diagnosis of discogenic entrapment neuropathy is correctly made, things can go wrong. This page considers failure of surgical technique as a cause of failed spinal surgery

The following seem to lessen the incidence of failed spinal surgery, and yet are often not practiced:

1. Meticulous preservation of the inter/supraspinous ligament. It is common practice to destroy this important structure entirely. This is comparable to destroying the cruciates ligament to perform a discectomy. Part of the reason is that preserving this ligament is time consuming and requires patience and technical skill. A desirable approach is to carefully divide the ligament in the midline, extending the division to the dorsum of the spinous processes, and separating the left and right halves of the inter-spinous ligament down to the ligamentum flavum. The ligament is then carefully separated from the spinous processes by sub-periosteal dissection to the base of the spines, and then retracted laterally. The reason for this care is that the ligament is the one structure capable of controlling the spinous processes under tension. It is almost certainly an important proprioceptive sensor and is intimately related to the paravertebral muscles. Therefore the relationship of the ligament to the muscles should be retained [It is common, but undesirable, practice to separate the muscle from the ligament, before destroying the ligament in approaching the dura]

2. No or minimal resection of bone.

3. Careful and sound reattachment of the supraspinous ligament to the spinous processes. If this is done the original functional and mechanical anatomy is returned to its original state, and function.

4. Meticulous preservation of the ligamentum flavum, which should be detached from the laminar edges cranially and caudally, and then detached laterally. This allows a flap of ligamentum to be raised as a “window” This window can later be flapped closed over the dura after the discectomy. The ligamentum flavum is the only structure designed to clothe the epidural tissues. If it is removed then a continuum of scar from dura to para-vertebral muscle is inevitable – and as muscle is subsequently contracted, so the dura will be repeatedly pulled, causing pain.

5. The epidural fat must be handled like the precious matter which it is. It offers the dura protection and allows the normal freedom of the dural sheath to move. Too often it is bruised, or sucked away. When this protective fat is lost adherence of the dura to its surrounds is likely.

6. Only the surgeon should retract the nerve root. Only he has the feel for the least exposure necessary, and can judge an acceptable degree of force in this retraction. Only the surgeon can know whether further dissection of the root is necessary to give the exposure needed minimal.

7. To attempt discectomy without magnification is not acceptable

8. The wound, including the disc space, should be copiously lavaged throughout, but especially before closure. This removes tissue which will necrotise, like disc fragments, or pieces of sub-cutaneous fat and muscle (which in any event should never have been damaged, and should not be there). Most important is to lavage away cotton and other fibres originating from swabs and patties, which have been shown to be highly inflammogenic.

9. An appropriate spinal table, for example a “butt board”, such as that made by Codman. This will reduce para-vertebral vein bleeding to the negligible.

10. Never use diathermy within the vertebral canal. [See the page on pain-less surgery about diathermy use in general].

11. Never use “absorbable”, would-be haemostatic, sponge, or foreign organic substances such as “bone wax”. These promote inflammatory reactions, and ultimately the noxious fibrosis which bedevils recovery from spinal. Rather leave any ooze – it will always stop – and place small vacuum drains.

 

http://www.bmj.com/cgi/eletters/327/7421/985

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