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ORIGINAL ARTICLE
Surgical Management of Lumbar Disc Prolapse By Fenestration Technique
*Manohara Babu. K V

*Associate Consultant, R.R orthopaedic centre, 2nd Cross, Shankarapuram, Bangalore, Karnataka, India.

Address for Correspondence
Manohara Babu. K V
Associate Consultant, R.R orthopaedic centre,
2nd Cross, Shankarapuram, Bangalore, Karnataka, India.
Phone:+919886060043
Email: manu_babukv@yahoo.com

Abstract

The aim of this study was to assess the clinical outcome of interlaminar discectomy by fenestration technique.  Since there is no significant difference between standard extensive laminectomy or limited fenestration and discectomy, it is preferable to opt for limited laminotomy or fenestration because extensive laminectomy may cause destabilization of spine later. We made a prospective study of 32 consecutive patients who underwent limited lumbar discectomy by fenestration technique in Victoria Hospital and Bowring and Lady Curzon Hospital, Bangalore from Jan 2003 to June 2005. The clinicoradiological parameters, appropriate indications for surgery, state of intervertebral disc at the time of surgery, and the post-op follow up were assessed.
We found that 20 patients had disc herniation at L4-L5 and 07 patients had disc prolapse at L5-S1 and remaining 5 patients had two level disc prolapse at L4-L5 and L5-S1.The last group underwent fenestration at two levels simultaneously. The results were evaluated using the criteria similar to those of MacNab and PROLO functional and Economic outcome criteria.The postoperative results were good in 29 (90%) patients, fair in 2 (6.2%) patients and poor in 1 (3.1%) case.
The results of this study show that enough space is available in interlaminar area to perform fenestration and disc excision without removing much of lamina. The results are comparable to microdiscectomy in standard references.
In conclusion, interlaminar lumbar discectomy by fenestration method without extensive laminectomy is effective and reliable surgical technique for treating properly selected patients with herniated lumbar disc at L4-L5 and L5-S1 levels.
Key words: Fenestration, Limited disc excision, Lumbar spine, Laminectomy.

J.Orthopaedics 2006;3(4)e6

Introduction:

Low back pain due to lumbar disc prolapse is the major cause of morbidity throughout the world affecting mainly the young adults. Lifetime incidence of low back pain is 50-70 % with incidence of sciatica more than 40 %. However clinically significant sciatica due to lumbar disc prolapse occurs in 4-6 % of the population. The degeneration of the disc results from many factors and can lead to prolapse into the intervertebral foramen, particularly at L4-L5 & L5-S1 level. The L3-L4 & L2-L3 account for the majority of remaining herniations1, 2. Detailed history, clinical examination supplemented by relevant radiological investigations can differentiate herniated lumbar disc prolapse from other causes of low back pain and sciatica. The outcome of surgery depends on many factors, such as careful selection of patients.

The success rate after lumbar discectomy reported in the literature varies considerably from 46% to 90%1. In the past various authors have attributed this variability to the surgical technique. It is apparent, however, that a more common reason is faulty patient selection criteria1.

The technique of lumbar discectomy has undergone significant modifications. Originally, a wide laminectomy was performed in an attempt to remove as much disc material as possible. This more radical surgery is no longer common as because extensive laminectomy may cause destabilization of spine later 1, 3. In 1982, Spengler described limited disc excision, only the ligamentum flavum and if necessary small portion of lamina inferiorly is removed to expose the prolapsed disc space and the extruded disc were removed1. Machemson advocated removal of only sequestrated and extruded loose disc fragments, with the minimal removal of tissue fragments from the intervertibral space2, 5. The advantage of limited lumbar disc excision by fenestration technique is a decrease in the incidence of postoperative spinal instability, decreased manipulation of the neural elements and subsequent perineural fibrosis1, 3, 5. In addition limited disc excision lessens the likelihood of penetration of the anterior annulus with potential injury to the viscera. This study was performed to assess the results of limited lumbar disc excision through interlaminar fenestration in patients fulfilling specific criteria.

Materials & Methods

We made a prospective study of 25 consecutive patients who underwent limited lumbar discectomy by fenestration technique in Victoria Hospital and Bowring and Lady Curzon Hospital Bangalore from Jan 2003 to June 2005. 18 patients were men and 14 patients were women. The average age at surgery was 34 years (range, 22 - 48 years). Objective neurological deficits were observed in 14 patients (43.7%) with one patient with bowel and bladder deficits (cauda equina syndrome). Method of collection of data is by patient’s evaluation through proper history taking regarding the low back pain as assessed by Back pain function scale, 6 thorough clinical examination, The clinical diagnosis was confirmed by CT scan or MRI. The criteria for selecting the patients were disc prolapse with bowel & bladder symptoms (cauda equina syndrome), with sensory or motor deficits, and with severe sciatica (unilateral or bilateral sciatica), which decreased by conservative measures (rest, anti-inflammatory medication, physiotherapy or even epidural steroids) but returned to the initial levels after a minimum of 6-8 weeks of above-mentioned conservative measures. And a Wadell nonorganic signs of less than 3 4.

Patients with disc prolapse other than L4-L5 and L5-S1, spinal canal stenosis, far lateral foraminal stenosis, and penetration of disc into the dura were excluded from the study1, 2, 5, 7. We obtained preoperative marker films in all cases to identify the proper level. Surgery was performed with the patient in knee chest position or prone position over bolsters. General anaesthesia was employed in all cases. The skin and Para spinal muscles were infiltered with 1 in 100000 diluted adrenaline to decrease the bleeding. Spine was approached through a two to three inch midline incision depending on the subcutaneous fat.

We did a standard interlaminar fenestration by cutting through ligamentum flavum and if necessary only inferior lamina using Kerrison`s rongeurs. The sequestrated and extruded loose disc fragments were removed, with the minimal removal of tissue fragments from the intervertibral space. The exiting nerve roots were cleared of compression in all cases. The residual interlaminar defect was closed by free fat graft in few cases.

Post operatively patient is made to stand up and ambulate on the next day and discharged within a week from the hospital. Sutures were removed after two weeks. Back strengthening exercises were advised from second week. Patient is advised to return to original occupation after 6 weeks2.

Results

20 patients (62.5%) had disc herniation at L4-L5 and 7 patients (21.8%) had disc prolapse at L5-S1 and remaining 5 patients (15.6%) had two level disc prolapse at L4-L5 and L5-S1.18 patients were men and 14 patients were women. The average age at surgery was 34 years (range, 22 - 48 years). All 7 patients with disc prolapse at L5-S1 were managed by interlaminar fenestration. Of the 20 patients with disc prolapse at L4-L5, 15 patients underwent only interlaminar fenestration and remaining 5 needed small inferior laminotomy to access the dura and disc. Patients who had disc prolapse at L4-L5 and L5-S1 levels underwent fenestration at two levels simultaneously. 10 patients (32%) had no Wadells nonorganic signs, 6 patients (10%) had one sign, 15 patients (46.8%) had two signs and 1 patient had 3 signs. Neurological deficits (either motor or sensory) were observed in 15 patients (60%) with one patient with bowel and bladder deficits (cauda equina syndrome). Of the 20 men 12 patients (40.6%) were active smokers. Co morbid conditions like diabetes and hypertension were present in 15 patients (48%). The average duration of hospital stay prior to surgery was 2 days. The average operating time for fenestration surgery was 65 min; with a range of 40-130 min. The average blood loss was 180ml. Only 2 patients (all women) required blood transfusion. These two patients had preoperative low hemoglobin levels. The average postoperative hospital stay was 3 days with a range of 2 to 5 days. Among immediate complications 2 patients (6.2%) had superficial infection, which required antibiotics for one week and two dressings, and one had dural tear. 2 patients (6.2%) had postoperative urinary retention which required catheterization for 1 day and both of them were males. Fortunately none of the complications permanently affected the outcome.

All patients were assessed after 3 weeks and at 6 weeks postoperatively and there after once 3 months. The average follow-up is 8 months, with a range of 6 weeks to 19 months. Follow up of the patients was done on regular OPD basis with history taking and assessing the back pain function scale, clinical examination and relevant radiological investigations in certain patients. The results were evaluated using Mac Nab`s criteria.

Mac Nab`s criteria1 of outcome

  1. Excellent is dropped.
  2. Good:
    1. Resumed preoperative function
    2. Occasional backache or leg pain.
    3. No dependency inducing medication intake
    4. Appropriate activity
    5. No objective sign of nerve root irritation.
  3. Fair
    1. Intermittent episodes of mild radicular or low back pain.
    2. No dependency inducing medication intake
    3. Appropriate activity
    4. No objective sign of nerve root irritation.
  4. Poor
    1. Inactive
    2. No productive occupation
    3. Continuing or worsening symptoms
    4. Abuse of drugs
    5. Objective sign of nerve root irritation.

The results were classified as good in 29 (90%) patients, fair in 2 (6.2%) patients and poor in 1 (3.8%) case. The patient poor recovery had Cauda Equina syndrome.. The functional recovery of neurological deficits occurred 4-8 months after the surgery.

Discussion :

A review of literature reveals success rates for lumbar disc surgery ranging from 46-96%1. The outcome of the lumbar discectomy depends more on the patient selection than on the surgical technique. Good results were obtained in 90% of the cases in our series. The fair results were related to subjective factors rather than to any objective impairment of function of the musculoskeletal system. All the four patients who had fair results had co morbid condition like diabetes mellitus or hypertension. And all of them had Wadells nonorganic signs as well.

Spengler described the technique of limited disc excsion through fenestration in 19821. The advantages of this technique are decrease in the incidence of postoperative spinal instability, decreased manipulation of the neural elements and subsequent perineural fibrosis and less likelihood of penetration of the anterior annulus with potential injury to the viscera. In the present study, interlaminar discectomy was adequate in 27 cases (84%). No laminotomy was required in these patients. Remaining 5 patients (16%) required inferior laminotomy. Most of these patients had disc prolapse at L4-L5 or double level disc prolapses. And laminotomy was done mostly during the early phases of learning curve. Thus interlaminar fenestration without laminotomy gives adequate space for disc excision at L4-L5 and L5-S1 levels in majority of patients. The role of autogenous fat graft is still debated2, we have used in few patients. No case of perineural fibrosis noted in our series till the last follow up.

A few authors have reported higher rates of success, a shorter hospital stay, and quicker return to work after microdiscectomy, but that has not been established in well-controlled studies3. In our series the operating time, in patient stay and success rates were comparable to the results of microdiscectomy reported in various studies. This might be due to close similarity of the two techniques. However microdiscectomy offers a better visual comfort and facilitates surgery.

Conclusion

The results of this study show that enough space is available in interlaminar area to perform fenestration and disc excision without removing much of lamina. The results are comparable to microdiscectomy in standard references.

In conclusion, interlaminar lumbar discectomy by fenestration method without extensive laminectomy is effective and reliable surgical technique for treating properly selected patients with herniated lumbar disc at L4-L5 and L5-S1 levels. The results are comparable to microdiscectomy, and this may be due to close similarity of the two conditions.

Reference :

  1. Dan M. Spengler, M D, Results with limited disc excision: Spine 7:604- 607, 1982.

  2. Michael H. Newman M D, out patient conventional laminotomy and disc excision. Spine 1995 Vol 20, no 3, pp 353-355

  3. Dietmar Stolke, MD, Wolf peter Sollman, Intra and postoperative complications in lumbar disc surgery MD.Spine, Vol 14, Number 1, 1989.page-56.

  4. Tania Larequi-Labuer, MD John-Paul Vader, MD, MPH. Appropriate indications for surgery of lumbar disc hernia and spinal stenosis. Spine vol, 22, nov-1997, page-203-209.

  5. Manish Garg and Sudhip Kumar. Interlaminar discectomy and selective foraminotomy in lumbar disc herniation. Journal of orthopaedics 2001, 9 (2): 15-18.

  6. Stafford et al, Back pain function scale, Appendix A. Spine, vol 25, Number 16, 2000.

  7. Toshihico Maruta, MD, Sherwin Goldman, MD. Waddell’s nonorganic signs and Minnesota Multiphasic Personality Inventory Profiles in patients with chronic low back pain. Spine, Vol 22, Number 1, 1997, page72-76.

  8. Tycho Tullberg, MD, Johan Isacson, Does Microscopic Removal of Lumbar Disc Herniation Lead To Better Results Than The Standard Procedure, Spine, Vol 18, number 1, 1993.

 

This is a peer reviewed paper 

Please cite as : Manohara Babu. K V: Surgical management of Lumbar disc prolapse by Fenestration technique

J.Orthopaedics 2006;3(4)e6

URL: http://www.jortho.org/2006/3/4/e
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