Neural Decompression by Laminectomy with Spinoplasty for Lumbar Spinal Stenosis

BACKGROUND Lumbar spinal stenosis is one of the common morbid conditions of adult population. Surgical intervention is recommended if conservative treatment is not effective. Aim of the surgery is to decompress neural tissues and it may vary from simple unilateral foraminotomy or laminotomy to multilevel bilateral laminectomy. Conventional laminectomy violates posterior stability and foraminotomy limits access to the neural tissues. Different techniques have been developed for adequate decompression with preservation of posterior stabilizing structures. METHODS Degenerative lumbar spinal stenosis in 22 cases was treated by laminectomy with spinous process osteotomy and re-positioning during October 2007 to August 2009. All cases had back pain with radicular pain and intermittent neurogenic claudication. Average age of the cases was 49.5 years and the average duration of symptom was 7 months. Conservative treatment was tried for 4 months. Average follow up period was 2.5 months. RESULTS Post operatively 82% of the cases were satisÞ ed. There was no radicular pain and intermittent claudication in all cases. Persistence of back pain and numbness in lower limbs was common complaints of majority of the cases. CONCLUSION “Laminectomy with spinous process osteotomy and re-positioning” technique easily decompresses lumbar spinal stenosis with preservation of posterior osteo-ligamentous structure.


INTRODUCTION
Lumbar spinal stenosis (LSS) is abnormal narrowing of the central canal or the lateral recess or inter-vertebral foramina (root canal), or its combination.It may be local, segmental or generalized.Stenosis can be due to hypertrophy of soft tissues or bone, and the narrowing can involve the bony canal or the dural sac or both.(Þg. 1) Etiology can be congenital (e.g. in achondroplasia) or acquired. 1,2,3Acquired causes can be degenerative facet joints, hypertrophied ligamentum ß avum, chronic disc protrusion with Þ brosis, spondylolisthesis or thickening of bone due to Paget's disease. 4Size and shape of the canal can be evaluated by the help of plain X-ray, CT scan or MRI.
LSS is a common cause of disability in middle-aged and elderly patients.Its typical clinical symptoms are chronic low back pain, sciatica pain in the back of the thigh and calve, and intermittent neurogenic claudication. 4,5,6The natural history of spinal stenosis is unclear. 7 the symptoms are less severe these cases can be treated conservatively with spinal posture and back muscle strengthening exercises. 6,7Epidural injection of steroid has mixed and temporary effect on the symptoms.Patients with serious or progressive pain or neurological dysfunction need surgical decompression with or without concomitant fusion of the spinal segment.Depending on the pathology it can be done at single level or multiple levels.Decompression procedure may vary from simple unilateral foraminotomy or laminotomy to multilevel bilateral laminectomy. 8Laminectomy has been the established surgical procedure for lumbar canal stenosis. 9The conventional laminectomy provides easy access to decompression but, may cause secondary instability. 10,11 structure but limits access and might increase the risk of neural tissue injury. 8,9,12,13To address the short comings of laminectomy and laminotomy procedures "laminectomy with restorative spinoplasty" procedures have been developed. 14,15,16,17,24Since 2007 we have treated 22 cases of LSS using this technique.Cases that had indication of fusion were excluded from the study.Out come of the surgical procedure is reported in average of 2.5 months follow-up.The cases were subjected for surgical decompression by laminectomy with restorative spinoplasty (osteotomy of base of spinous process and rerepositioning).Intervertebral disc was not removed, but sequestrated disc was removed in two cases.In two cases there was minor dural tear which sealed itself after applying Abgel.Peri-operative period was uneventful.Symptomatic and neurological improvement was accessed on 5 th (day of wound inspection) and 14 th (day of suture removal) post operative day.Patients were asked to come for follow up after 4 weeks of discharge from hospital (Þ rst follow-up), after 3 months, after every 6 months.Outcome of surgery was evaluated on every visit.

Surgical technique
Under general anaesthesia, patients were put on a spinal frame in prone position.Level/s to be decompressed was reconÞ rmed under image intensiÞ er.A mid line skin incision is given just enough to exposed the targeted level/s.The posterior surface of the vertebral arc (spinous process, lamina and facet joint with intact capsule) is exposed sub-periosteally from one side.With a 20mm curved osteotome, concave surface up, the bases of spinous process of the targeted vertebrae and one vertebra proximal and one distal is osteotomised.With the help of a Cobb elevator opposite side laminae are cleared from soft tissue attachments till the facet joints.The facet joint capsules are kept intact.The whole osteoligamentous complex containing spinous processes, supra and interspinous ligaments with paravetebral muscles of opposite side is retracted laterally with self-retaining Gelpi retractors.Center of the posterior arc of the vertebrae with lamina and facet joints can easily be exposed.Excess of the bone in the bases of osteotomised spinous process is nibbled out with bone nibbler.Thinned out laminae and ligamentum ß avum is excised with Kerrison rongeurs to expose the vertebral canal.The lateral recesses and neural foramen can be easily accessed and decompressed from opposite side.(Fig 2 ) After adequate decompression the laterally retracted osteo-ligamentous complex is repositioned and sutured with ipsilateral thoraco-lumbar fascia after putting a suction drain.Average operating time was about 2 hours.
Post-operatively, patient was allowed to sit up and walk on second or third day with a lumbar corset that was continued for at least 3 months.Isometric back and abdominal muscle exercise were taught and encouraged as tolerated.

RESULTS
Out come of the surgery was evaluated on the basis of symptomatic relief and neurological improvement.Follow-up of the cases was very poor.Five cases lost in follow up after discharge could not be contacted.Seven patients attended the Þ rst follow up (6 weeks post operation) and then were lost.Second follow of up at 3 months were attended by 8 cases and rest of the All cases had signiÞ cant improvement in radicular pain and neurogenic claudication.However, they had persistent back pain.Eighteen patients (82%) were satisÞ ed, 3 were slightly satisÞ ed at their last follow up and one patient was not satisÞ ed.Persistence of back pain and some numbness in lower limbs was the reason for their dissatisfaction.
Radiological evaluation at 3 and 6 months follow up (10 cases) showed healing of osteotomised bases of spinous processes of proximal and distal vertebrae.There was no progression of listhesis and segmental instability.

DISCUSSION
Degenerative lumbar spinal stenosis (LSS) is a common cause of disability in middle-aged and elderly patients. 5,6We surgically treated 22 cases of LSS who did not respond to conservative treatment.The decompression procedure was done with spinous process osteotomy and laminectomy as initially recommended by Sano S et al, 15 in his preliminary report in 1983.The aim of this technique is to preserve the posterior stabilizing structures as much as possible.The spinous process is osteotomised from one side so that the opposite side paraspinal muscles are kept intact with its bony and ligamental attachments.Though the follow up period of the studied cases is short the results are quite encouraging in 2.5 months average follow-up.There was signiÞ cant improvement in symptoms and neurological impairment in majority of the cases after the decompression.Persistence of back pain and some numbness in the lower limbs was present postoperatively.This is not an uncommon symptom as described by various authors. 22,23ny surgical techniques are recommended for decompression of a stenosed lumbar canal.Laminectomy has been a standard procedure 9 but it violates the posterior stabilizing osteo-ligamentous structures. 8,10,11And thus, might cause secondary segmental instability.Laminotomy or fenestration is a relatively conservative or limited type of surgery that limits access to the neural structures.There is always a problem of incomplete decompression and risk of neural tissue injury. 8,9,13,19For adequate access to the neural tissue and preservation of the posterior structures of the vertebrae different techniques; laminectomy with spinous process osteotomy, 14,15,16,24 microendoscopic laminotomies, 18,19,20 spinoplasty 17 method have been recommended.Bresnahan L et al compared the biomechanical changes between conventional laminectomy and posterior element preserving surgeries, and recommended that preservation of the posterior spinal elements could minimize the risk of developing de novo postoperative changes in spinal alignment and/ or acceleration of facet and disc degeneration. 21no S et al introduced the laminectomy with spinous process re-attachment surgical technique in 1983. 15atanabe K et al recommended the lumbar spinous process splitting laminectomy for LSS. 16In recent years also, there are reports on effectiveness of different techniques by Japanese clinicians with good postoperative results.Matsudaira K et al introduced a new technique, modiÞ ed fenestration with restorative spinoplasty (MFRS) for the treatment of lumbar spinal stenosis.In their series 74% of cases had full satisfaction after surgery. 17Sasai K had reported good satisfaction with the result of their technique, microsurgical bilateral decompression via a unilateral approach, applied in 48 Japanese patients with LSS at 2 years of follow -up. 18Pao JL et al did microendoscopic decompressive laminotomy (MEDL) in 53 Taiwanese LSS patients.About 85% of cases were satisÞ ed with the surgery. 20Yagi M et al developed a novel, median-approach microendoscopic laminectomy for LSS decompression and 90% of cases were satisÞ ed with the treatment. 19me out come was observed by S M Tuli et al in their 610 Indian patients in 10 years duration treated by a new technique of spinoplasty. 24Our results in terms of patient's satisfaction is comparable to other series, 82% cases are fully satisÞ ed and 17% had partial satisfaction in 2.5 months follow up period.In this technique we osteotomise spinous process of one vertebra above and one below the targeted segments for better exposure.There was good union of these spinous processes in 3 months follow up.More extensive study with measurements of canal diameter, symptomatic scoring system and adequate follow up is recommended in future.

Figure 1 .
Figure 1.Lumbar spinal stenosis at multiple levels.A. Diagrammatic representation of lumbar stenosis at L3-4 and L4-5.B. Plain X-ray of lumbar spine showing severe degenerative changes at multiple levels.Grade I spondylolisthesis is noted at L4-5 level.C. MRI Þ ndings of lumbar spinal stenosis at multiple levels.

Figure 2 :
Figure 2: A. Subperiosteal dissection of paravertebral muscles from one side.B. Spinous process osteotomy to expose the laminae and ligamentum ß avum.C. neural decompression by Laminectomy.

Decompression by Laminectomy with Spinoplasty for Lumbar Spinal Stenosis
Foraminotomy or laminotomy preserves the posterior stabilizing Twenty two cases of LSS due to degenerative spondylosis with or without intervertebral disc prolapse and grade I spondylolisthesis was included in this study.The average age of the cases was 49.5 years, ranging from 38 to 68 years.16 cases were male and 6 were females.Low back pain with radicular pain and intermittent neurogenic claudication were the symptoms in all cases.Bilateral symptoms with unilateral predominance were present in majority of the cases.The average duration of symptom was 7 months.Neurological deÞ cit in the form of motor and sensory deÞ cit was observed in 14 cases.None of the patients had bowel and bladder involvement.