THE POST-LAMINECTOMY SYNDROME

Pre-operative patterns of pain and altered function have been found to persist post-operatively following disc surgery. This article explores theoretical concepts which may provide a rationale for successful post-operative treatment.


INTRODUCTION
The post-lam inectom y syndrom e is defined as a term encom passing all persistent severe sym ptom s follow ing operation on a lumbar disc1. It is thought to be due both to instability of the m otion segm ent and adhesions in the spinal canal.
Spangfort^ reviewed the results of 2504 laminectomies, se lected for the study because they had clear-cut signs of nerve root entrapm ent. He found that com plete relief of both leg and back pain post-operatively occurred in only 60% of cases. Failure to relieve pain in these cases of nerve root entrapm ent w as attributed to one or m ore of the following: • The exploration having been carried out at the wrong level • A second disc prolapse having been overlooked • The nerve root continuing to be com pressed by the posterior intervertebra 1 joints • Spinal stenosis causing pressure on the nerve root • Rarely, because of an extraforam inal lateral disc herniation^.
Wilkinson^ prefers the term "failed back syndrom e" because the syndrom e is not always preceded by an incorrectly performed operative procedure but can also occur follow ing correctly per formed surgery.
Should we, therefore, look beyond surgery for other perpetu ating causes of the residual pain? W hy does pain continue postoperatively? Is this pain neurogenic or m usculoskeletal? Can we treat this condition effectively?

Theoretical assumptions
As far back as 1983 Travell and Sim ons suggested that m yo fascial trigger points which have becom e activated pre-operatively are likely to remain active post-operatively, and are there fore likely to continue to cause pain long after the nerve root has been decompressed satisfactorily. To test this assumption 1 have assessed the presence of trigger points and the patterns of pain pre-and post-operatively in patients treated in a surgical spinal unit. Pre-operatively, trigger points producing pain were identi fied but deactivation of these trigger points did not have a lasting effect. Post-operatively the trigger points were found to be situ ated in the same distribution and deactivation over several treat ment sessions provided lasting relief of pain.
The purpose o f this article is not to discuss the research as such, but to exam ine theoretical assumptions regarding the m echa nisms of pre-and post-operative pain which m ay explain the results of the study.

Pre-operative back pain
The developm ent of disc herniation at the level of the lower lumbar segments is assumed to set the pain process in operation.
Altered segmental function provokes protective spasm in the muscles surrounding the joints, resulting in segmental imbalance locally. This results in com pensatory reaction and adaptation in other segm ents so that finally the whole spinal system is reflexly involved in the activation of trigger points*'. A cycle of strain and resultant pain is set up which magnifies and reinforces this mechanism as the local pathology progresses. Secondary muscle and fascial shortening occurs which is responsible for generalised muscle stiffness and restriction of joint movement and, in turn,^S

UMMARY P
re-operative patterns of pain and altered function have been found to persist post-operatively following disc surgery. This article explores theoretical concepts which may provide a rationale for successful post-operative treat ment.
V______________________________ J restrictive involvement of joint structures. It is this low back stiffness, in addition to pain, w hich causes the patient to develop abnormal patterns of posture and gait.

Pre-operative leg pain
Simultaneous with the mechanisms described above, entrap ment of the emerging nerve root by the disc prolapse gives rise to radicular pain in segmental distribution in the leg. The muscles supplied by this nerve root respond by going into spasm. As in the case of local back pain, prolonged spasm leads to shortening and to the development of trigger points w hich in turn generate their own patterns of referred pain.

Post-operative pain
The two causes of the post-lam inectom y syndrom e have been stated to be motion segm ent instability and the presence of adhe sions in the spinal canal.
It is possible that motion segm ent instability is not only due to expulsion or operative removal of the intervertebra 1 disc, but also to imbalances in the intrinsic musculature due to the pre-operative development of the cycle of altered segmental function as Adverse neural tension can also be generated by restrictions at mechanical interfaces occurring as a result of the altered segm en tal function and subsequent muscle spasm and myofascial short ening. Even minimal pressure com prom ises the blood supply to the nerve and affects the function of the nervi nervorum supply ing the nerve itself. Increasing pressure affects axonal flow and nerve conduction.

Conservative measures
Drugs, a corset and bed-rest are appropriate in the early stages and are beneficial in restricting the inflam m atory process and thereby relieving im m ediate post-operative pain.

The joints
Passive

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