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Year : 1999  |  Volume : 47  |  Issue : 4  |  Page : 286--9

Interlaminar decompression in lumbar canal stenosis.

KR Patond, SC Kakodia 
 Department of Orthopaedic Surgery, M.G. Institute of Medical Sciences, Sevagram, Distt. Wardha, Maharashtra, 442102, India., India

Correspondence Address:
K R Patond
Department of Orthopaedic Surgery, M.G. Institute of Medical Sciences, Sevagram, Distt. Wardha, Maharashtra, 442102, India.


Opinion is still divided over a standard surgical procedure to decompress lumbar canal stenosis. Both, laminectomy with or without facetectomy and foraminotomy and interlaminar fenestration have been advocated. In the present communication interlaminar decompression in lumbar canal stenosis has been discussed. Sixteen consecutive patients (7 males and 9 females) with clinical, neurological and radiological features of lumbar canal stenosis were treated by interlaminar (fenestration) decompression. The age of onset of symptoms ranged between 22-57 years. Adjoining lamina around interlaminar space of involved segment along with ligamentum flavum and part of facet joint (undercutting facetectomy), extending laterally (foraminotomy) were removed at single or multiple levels. Follow-up response (93.7%) over a period of two and half years showed the results as good in 73.3% and fair in 26.7% of cases, with uniformly uneventful post-operative period.

How to cite this article:
Patond K R, Kakodia S C. Interlaminar decompression in lumbar canal stenosis. Neurol India 1999;47:286-9

How to cite this URL:
Patond K R, Kakodia S C. Interlaminar decompression in lumbar canal stenosis. Neurol India [serial online] 1999 [cited 2023 Sep 29 ];47:286-9
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  ::   IntroductionTop

Verbiest is credited with highlighting the developmental narrowing of lumbar canal as a distinct clinical entity responsible for causing compression of cauda equina.[1],[2] International conference of back surgeons defined this disorder as a condition involving any type of narrowing of spinal canal, nerve root canals or of the intervertebral foramina.[3] Kirkardly-Willis et al in a review article had drawn attention to the association of nucleus pulposus with degenerative and developmental stenosis.[4] Kirkdly-Willis and Young postulated the theory of spinal degeneration on the basis of clinical and anatomical data.[5]

Surgical treatment of canal stenosis is aimed to relieve pressure on neural tissues in the central and nerve root canals.[6] Verbiest suggested that narrowing is due to encroachment by articular processes on the spinal canal and the laminectomy alone may not suffice without removal of medial part of articular facets.[1] Hence total laminectomy with medial facetectomy was a common treatment of lumbar canal stenosis. Shenkin and Hash[7] used foraminotomy (unroofing the foramina) to relieve nerve root compression. Getty et al[8] advocated selective decompression of nerve roots by partial undercutting facetectomy with fenestration. Nakai et al showed good result in 70.6% of cases, with fenestration for central canal stenosis of lumbar spine in 34 patients.[9] Thus, standard procedures used to decompress the narrow canal are laminectomy with or without facetectomy, foraminotomy and interlaminar fenestration.[6],[8],[9],[10] Excision of lumbar disc through fenestration is well reported. However, in spinal stenosis this has not been thoroughly studied.

  ::   Material and methodsTop

The study included sixteen patients - (7 males and 9 females). The age of onset of symptoms of lumbar canal stenosis ranged between 22-57 years. They were treated by interlaminar fenestration to decompress nerve roots at single or multiple level in the department of Orthopaedic surgery at MG Institute of Medical Sciences in 30 month period. Details of symptoms especially low back pain, radicular pain, neurological claudication, motor weakness and sphincter disturbances were recorded. Family history for similar complaints was enquired to exclude disorders like achondroplasia and familial idiopathic canal stenosis. Clinical examination included recording of spinal abnormalities and neurological deficit. Patients with profound subjective symptoms and minimal or absent neurological findings at rest, were re-examined after making the patient walk till the symptoms appeared. All patients were subjected to plain x-rays and omnipaque myelographic evaluation prior to surgery. Jones and Thompson index was calculated as a ratio between the areas of spinal canal and vertebral body.[11]

The patients were operated in prone position under general anaesthesia. During interlaminar fenestration, bone around interlaminar space of involved segment, (a level indicated by abnormal clinical and myelographic findings) was trimmed along with ligamentum flavum and part of facet joint (partial undercutting facetectomy), whereas adjoining laminae, spinal process with interspinous ligament and zygaphophyseal joints were preserved [Figure. 1]. Fenestration extended laterally (foraminotomy) to decompress swollen and oedematous nerve roots. Operative finding recorded correlated with the clinicoradiological impression. Adequacy of decompression was assessed during surgery by free mobility of roots and probing the root canal. Negative suction drain was used in all patients, and was removed within seventy two hours.

At discharge, mostly by the end of second week after surgery, patients were evaluated for subjective relief of symptoms and improvement in objective neurological deficit.

  ::   ResultsTop

Neurogenic claudication was the commonest symptom observed. This symptom was relieved by various maneuvers that flex lumbar spine. In four patients extension of spine was limited and painful. Motor deficit was less common than sensory. In three patients both motor and sensory deficit was noted. Spinal index was positive in 14(87.5%) patients with clinical features of stenosis seen in 16. The canal body ratio in sixteen patients at different levels [Figure. 2] suggested stenosis at L5, L4, L3, L2 and Ll in 9, 11, 9, 6 and 5 patients respectively. Stenosis at multiple levels was seen in five patients. There was gradual increase in average canal body ratio at subsequent vertebral level. Myelogram confirmed the diagnosis in almost all patients, and helped in locating the exact site and level of compression. Surgical time ranged from one hour to two and half hours depending upon the number of levels explored. Fenestration was done at two levels in twelve, three levels in two and four and five levels in one patient each.[9] Nerve roots were compressed in almost all cases in the particular involved segment and these cases required partial undercutting facetectomy. Five patients (16.6%) with swollen and oedematous roots needed foraminotomy. Spinal fusion was done in one patient where preoperative radiogram showed vertebral slip. At operation we found ligamentum flavum hypertrophy in all the sixteen (100%) patients, of which three had classical hour glass constriction. Facet joint hypertrophy was seen in 14 (87.5%) and concomitant bulging disc in six (37.5%) patients. An average of 106 ml of haematoma was drained by negative suction within 72 hours. One patient had contused right L5 root postoperatively, which recovered in due course of time with steroids. Otherwise postoperative period was uniformly uneventful.

Follow-up response was 93.7%. Fifteen patients were available for follow-up at variable intervals and were assessed as shown in [Table I] at the 8 years follow up.

  ::   DiscussionTop

Capacity of spinal and root canals is compromised in extension as bucking of ligamentum flavum and approximation of articular facets encroaches the canal posterolaterally. Backache, when present, usually preceds the leg pain[12] and probably reflects the natural history of degenerative changes in lumbar spine.[8] Eisenstein reported many subjects with stenosis by this index but they had obvious adequate canals for accommodating cord or cauda equina, as they were asymptomatic. Thus spinal index cannot be considered as valuable indicator of stenosis and it helps only indirectly in the diagnosis of stenosis. Nakai[9] reported 82.3% and 70.5% good results early after surgery and at the 8 years follow-up in 34 patients of central canal stenosis. This change in percentage of improvement with time was due to recurrent stenosis at operatively segments in three and segmental instability in five patients as indicated by disc resorption and horizontal slip on roentgenogram. We did not observe the vertebral instability or new bone formation at operative segments on follow-up roentgenogram. The follow-up however, is not long enough.

Even after adequate decompression, the degenerative changes are known to continue, giving rise to low backache. Therefore it is important to inform the patients before surgery that they are likely to have some pains afterwards so that they are prepared psychologically and do have more balanced approach to their situation. In our study consistently good results are attributed to proper selection of patients by clinical examination, precise and early diagnosis on omnipaque myelogram, meticulous surgical protocol consisting of proper surgical position, adequate decompression and negative suction for draining the haematoma.

It was noted that interlaminar fenestration offered sufficient although minimal decompression, relieved the pain of root origin (symptoms in the leg). Any reduction of backache was a bonus. The procedure is not recommended unless symptoms and signs in the leg are predominant features.[8] Interlaminar fenestration provides early mobility and return to work with minimum hospital stay, preserves spinal stability even if done at multiple levels on both sides for bilateral symptoms and signs and can be extended to hemilaminectomy if required.


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