LUMBAR MICRO-DECOMPRESSION: INTERMEDIATE TERM OUTCOME

Abstract

Decompression of the lumbar spine for spinal stenosis is the most commonly performed spinal surgical procedure in patients over 60 years old. The aims of surgery are to relieve compression of the spinal nerves and retain integrity of the structural elements of the spinal column and its function as a supportive structure.

In trying to avoid excessive removal of the posterior supportive structures of the spinal column without compromising full and safe decompression of the spinal nerves, techniques are being developed to reduce bone removal but also allow access to the spinal canal. One such micro-decompression involves a hemi-lami-nectomy and lateral recess decompression on the more symptomatic side followed by undercutting the spinous process and facet joints and decompressing the opposite side from within the canal aided by the use the operating microscope, a high speed burr and a metal guard to protect the dura and nerves.

Although previous reports exist, as yet, there is no long-term evidence that the theoretical benefits of this “micro-decompression” translate into real clinical improvement in outcome with a reduction in the incidence of post-operative instability in comparison with the bilateral “fir-tree” type of decompression.

We have reviewed our first 100 consecutive patients who have had a spinal micro-decompression carried out by a single spinal surgeon over a period of 5 years. Patients with central or lateral recess stenosis with unilateral or bilateral symptoms were considered for this procedure with 58 female and 42 male patients included in the follow-up series. Mean age was 65 years. Patients were assessed by a combination of clinical review and self-assessment questionnaires. After a follow-up period of up to 5 years (mean 3 years) we have seen symptomatic late instability develop in 4 patients requiring a further surgical procedure in 2 of these. Symptoms typically developed 2 years after the original operation following an initial improvement in radicular symptoms and back pain. This compares favourably with published results for wide decompression where re-operation rates of 18% are reported. We have analysed the cases of delayed instability in more detail to evaluate whether the late deterioration could have been predicted. This has allowed us to clarify the specific indications and contra-indications to the micro-decompression procedure.

Lumbar micro-decompression has proved to be safe with few complications. It would appear that this technique has advantages over wide decompression without compromising safety but it will be important to continue with longer term follow-up of these cases.