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SPINE Table of Contents   
Year : 2005  |  Volume : 39  |  Issue : 3  |  Page : 148-150
Interlaminar fenestration in lumbar canal stenosis- a retrospective study


Department Of Orthopaedics, Himalayan Institute of Medical Sciences, Dehradun, India

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   Abstract 

Background: Degenerative lumbar canal stenosis is a multifaceted problem presenting as backache and neurological claudication.
Methods: In fifteen patients of acquired degenerative lumbar canal stenosis multi level interlaminar fenestration with discectomy, if required, was carried out. Retrospective analysis was done to assess the out come by assessing the relief in backache and neurological claudication.
Results: The mean age of patients was 50.4 years and average duration of neurological claudication was nine months. Diagnosis of the degenerative lumbar canal stenosis was made by clinical examination and confirmed by radiological and MRI measurement of cross section area of neural canal. Interlaminar fenestration was done at four levels and three levels in six patients each while it was done at two levels in remaining three patients. None of the patients reported immediate or late onset of backache or restriction of spinal movements, indicating spinal in stability. None of the patients had neurological claudication in the postoperative period.
Conclusion: Retrospective analysis suggests that multiple interlaminar fenestrations done in moderate spinal stenosis provides adequate neurological decompression besides maintaining spinal stability.

Keywords: Degenerative lumbar canal stenosis, Interlaminar fenestration.

How to cite this article:
Gupta P, Sharma S, Chauhan V, Maheshwari R, Juyal A, Agarwal A. Interlaminar fenestration in lumbar canal stenosis- a retrospective study. Indian J Orthop 2005;39:148-50

How to cite this URL:
Gupta P, Sharma S, Chauhan V, Maheshwari R, Juyal A, Agarwal A. Interlaminar fenestration in lumbar canal stenosis- a retrospective study. Indian J Orthop [serial online] 2005 [cited 2020 Jan 21];39:148-50. Available from: http://www.ijoonline.com/text.asp?2005/39/3/148/36700

   Introduction Top


The term stenosis describes a narrowing or a constriction of a tubular structure [1] . Spinal stenosis describes a clinical syndrome of back, buttock or leg pain with characteristic provocative and palliative features [2] . Spinal stenosis can be classified as congenital or developmental, acquired degenerative, iatrogenic, post traumatic and metabolic types. Out of these types acquired degenerative spinal stenosis is most common. This is further subdivided into central, peripheral and degenerative spondylolysthesis types.

Spinal stenosis refers to morphology not the symptoms. Neurologic claudication also known as pseudoclaudication is diagnostic of spinal canal stenosis. It is a clinical syndrome with symptoms of leg pain, parasthesia and weakness that are associated with walking or standing. Pain is the predominant feature, which is either unilateral radicular pain or has diffuse nondermatomal symptoms beginning in the buttocks and extending a variable distance into the legs. Sitting or bending forwards relieve symptoms.

Surgical treatment of lumbar canal stenosis is aimed to relieve pressure on neural tissues in the central and nerve root canals [3] . The gold standard surgical procedure for lumbar canal stenosis is decompressive total laminectomy. Verbiest suggested that narrowing is due to encroachment by the articular process on the spinal cord and the laminectomy alone may not suffice without removal of the medial part of the articular facets [4] .

However multiple level total laminectomies along with medial facetectomy can increase spinal instability leading to backache and restriction of movements in long term. To maintain stability of spine, alternatives to total laminectomy in the form of hemilaminectomy, laminoplasty and interlaminar fenestration have been advocated. Nakai et al showed good results in 70.6 % of cases with interlaminar fenestration for central canal stenosis of lumbar spine in 34 patients [5] .

This retrospective analysis has been done to study the outcome of interlaminar fenestration in cases of degenerating lumbar canal stenosis.


   Material and methods Top


Between April 2002 and March 2003, fifteen patients of acquired degenerative lumbar canal stenosis were operated for interlaminar fenestration. There were nine male and six female patients. Minimum age was forty-two years and maximum age was seventy-five years with an average of 50.4 years [Table 1]

The diagnosis of acquired lumbar canal stenosis was made on the basis of the presence of neurological claudication and by exclusion of congenital, traumatic or other forms of lumbar canal stenosis. Diagnosis was confirmed by the radiological measurement of ratio of vertebral body diameter and vertebral canal diameter in AP and lateral views which should be less than one [Figure - 1] and by MRI assessment of cross section area of lumbar spine [Fiure 2]. The canal cross sectional area of 180 + 50 mm 2 is the normal range, while 100­70 mm 2 is considered as moderate stenosis. Canal cross section area less than 70 mm 2 is indicative of severe stenosis [1]

Multiple level interlaminar fenestrations with discectomy, if required, were carried out in all the patients. Bone around interlaminar spaces of involved segments was trimmed along with ligamentum flavum and a part of facet joint. The adjoining laminae, spinous process with interspinous ligament and facet joint were preserved. Fenestration extended laterally to decompress swollen and edematous nerve roots [Figure - 3]. Adequacy of decompression was assessed during surgery by the free mobility of nerve roots and probing the root canal. Decision of discectomy was taken on the basis of clinico radiological evidence of disc prolapse. Patients were followed up at six weeks interval and then every three months and evaluated at the end of follow up (maximum three years and minimum two years).


   Results Top


The average duration of onset of neurological claudication was nine months indicating acquired degenerative nature of lumbar canal stenosis. None of the patients had sensory or motor deficit except for bilateral absence of ankle jerk in six patients that may be insignificant in older age patients. Vertebral diameter and canal diameter ratio was less than one in all patients [Table 1].

Retrospective analysis of canal cross section area measurement by MRI revealed maximum canal cross section area 107 mm 2 while minimum cross section area was 77 mm 2 [Table 1], indicating that all the cases belonged to category of moderate canal stenosis. In six patients, canal narrowing was seen at four levels, while in another six patients, it was seen at three levels. Remaining three cases had canal narrowing at two levels. Two level disc prolapse was seen in five patients and single level disc prolapse in three patients. Remaining seven patients had no disc prolapse.

Interlaminar fenestration was done at four levels and three levels in six patients each while it was done at two levels in remaining three patients. On the basis of MRI findings disc excision was done at two levels in five patients and one level in three patients. Nerve roots were compressed in almost all cases in the particular involved segments and these cases required partial medial facetectomy.

On retrospective analysis of outcome of the six patients in whom four levels interlaminar fenestration was done, it was seen that all of them belonged to older age group. Four patients had no complaints of backache, numbness or heaviness in lower limbs or neurological claudication while two patients had occasional heaviness on prolonged walking.

Four out of six patients, in whom interlaminar fenestration was done at three levels, had subjective numbness only upto six months of postoperative period. Remaining two patients of three level interlaminar fenestration were completely asymptomatic till last follow up. Three patients of two level interlaminar fenestration were also asymptomatic till last follow up.

Eight patients with swollen and edematous roots needed foraminotomy. All of them had postoperative subjective numbness or heaviness in lower limbs that gradually disappeared. Maximum duration upto which subjective numbness persisted was six months, which was seen in four patients. Ligament hypertrophy was seen in all patients, which was excised. None of the complications in the form of dural tear, root avulsion, superficial or deep infection were observed.

Patients were allowed to walk and sit as soon as surgical pain subsided. None of the patients in this retrospective study, reported immediate or late onset of backache or restriction of spinal movements, indicating spinal stability. None of the patients had neurological claudication in the postoperative period. All the patients reported an increase in comfortable walking distance.


   Discussion Top


Postacchani defined lumbar canal stenosis as a "narrowing of osteoligamentous vertebral canal and/ or the intervertebral foramina causing compression of the thecal sac and/ or the caudal nerve roots, at a single vertebral level, narrowing may affect the whole canal or part of it [6] .

The anatomical changes in the degenerating stenosis include hypertrophy of articular processes, thickening of ligamentum flavum and disc degeneration, sometimes associated with posterior osteophytosis of the vertebral body [1] . Hypertrophy of superior articular process contributes to the deformation of central portion of the canal and narrows the intervertebral portion of the nerve root canal, while hypertrophy of the inferior articular process may cause narrowing of the central portion of the spinal canal [1] .

The ligamentum flavum are usually shortened in the vertical and transverse planes and thickened. The shortening is due to loss of disc height and hypertrophy of the articular process, the thickening results from the shortening and from degenerative changes in the ligamentum tissue [6] .

Surgery in lumbar canal stenosis aims to decompress the nervous structure particularly the nerve root in their extra thecal course, without compromising vertebral stability [7] . Preservation of the stable spine is of paramount importance because the relief of symptoms in the leg may not satisfy the patient if back pain develops or is made worse [8] .

Lumbar stenosis in the elderly is due mainly to a combination of facet hypertrophy and soft tissue buckling. It is therefore logical to limit the resection to a causative structure, thus limiting damage and instability. Interlaminar fenestration allows spinal stability to be maintained since tissue disruption is minimized, and decompression is carried out without violating the integrity of the laminae, facet joints and interspinous ligaments [9] .

In the last few years the technique of interlaminar fenestration has been reported, since it preserves vertebral stability better than total laminectomy. Aryan and Ducker [10] and Nakai et at [5] reported that greatest advantage of multiple wide fenestration is that it preserves vertebral stability. Literature suggests that multiple interlaminar fenestrations is treatment of choice in developmental stenosis and it is a preferred surgical option for degenerating stenosis when narrowing is mild to moderate since it preserves spinal stability [7]. Retrospective analysis also suggests that multiple interlaminar fenestrations done in moderate spinal stenosis provides adequate neurological decompression besides maintaining spinal stability.

 
   References Top

1.Chapman MW. Spinal stenosis. In: Chapman's Orthopaedic Surgery, Vol-4 3rd edition. Lippincott Williams & Wilkins: 2001, 3817-3843.  Back to cited text no. 1    
2.Rothman-Simeone. Spinal Stenosis. In: The spine Vol-1, 4th edition, WB Saunders Company.1992; 779-806T.  Back to cited text no. 2    
3.Grabian S. Current concept review, the treatment of spinal stenosis. J Bone Joint Surg (Am). 1980; 62: 308-313.  Back to cited text no. 3    
4.Verbiest H. A redicular syndrome from developmental narrowing of its lumbar vertebral canal. J Bone Joint Surg (Br).1954; 36: 230-234.  Back to cited text no. 4    
5.Nakai O, Okawa A, Yamura T. Long term roentgenographic and func­tional changes in patients who were treated with wide fenestration for central lumbar stenosis. J Bone Joint Surg (Am). 1991; 73: 1184-1191.  Back to cited text no. 5    
6.Postacchini F. Management of lumbar canal stenosis: J Bone Joint Surg (Br).1996; 78: 154-164.  Back to cited text no. 6    
7.Postacchini F, Cinoit G, Perugia D, Gumina S. The Surgical treat­ment of central lumbar stenosis; J Bone Joint Surg (Br).1993; 75: 386­392.  Back to cited text no. 7    
8.Patond KR, Kakodia SC. Interlaminar decompression in lumbar canal stenosis; Neurology India. 1999; 47: 286-289.  Back to cited text no. 8    
9.R Gunzberg, M Szpalski. The Conservative surgical treatment of lumbar spinal stenosis in the elderly. Eur Spine J. 2003; 12: 176-180.  Back to cited text no. 9    
10.Aryanpur J, Ducker T. Multilevel lumbar laminotomies, an alternative to laminectomy in treatment of lumbar stenosis. Neurosurgery. 1990; 26: 429-433  Back to cited text no. 10    

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Correspondence Address:
Puneet Gupta
Department Of Orthopaedics, Himalayan Institute of Medical Sciences, Swami Rama Nagar, Doiwala, Dehradun - 248140
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5413.36700

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    Figures

  [Figure - 1], [Figure - 2], [Figure - 3]



 

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    Abstract
    Introduction
    Material and methods
    Results
    Discussion
    References
    Article Figures
 

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