Objective

The aim of this study is to demonstrate that Anterior Lumbar Interbody fusion is effective in treating L5 radiculopathy due to foraminal stenosis. Summary of background data Radiculopathy due to foraminal stenosis as a result of loss of disc height may not respond to traditional foraminotomy/neurolysis due to inability to improve cranio-caudal stenosis. Interbody techniques have been advocated to increase disc space height and hence relieve root compression.

Methods

Prospectively collected outcomes data for 27 consecutive patients undergoing single or double ALIF to treat L5 radiculopathy due to foraminal stensosis was reviewed. VAS, Oswestry and Roland Morris scores pre-operatively, at 3 and 6 months were complete for 24 of 27 patients (17 degenerative disc disease, 7 spondylolisthesis). A statistical package ( STATA) was used to calculate descriptive data and The Wilcoxin Signed Rank Test used to determine statistical significance.

Results

There was significant improvement noted in all the measured parameters including VAS which improved from a mean pre-op of 6.5 ( 95 % CI 5.9 - 7.1) to 1.3 ( 95% CI 0.8 - 1.8) at 3 months and 0.9 ( 95%CI 0.5 - 1.3) at six months ( p< 0.0000)

Conclusion

In conclusion our study has shown that ALIF is an excellent option for the treatment of L5 radiculopathy due to foraminal stenosis as results are consistent with a significant improvement in disability and pain.

J.Orthopaedics 2012;9(2)e3

Keywords:

Anterior lumbar interbody fusion; Foraminal stenosis; Degenerative disc; Spondylolisthesis

Pathoanatomy :

The anatomy of the lateral lumbar spinal canal and nerve roots has been described in several studies (5,6,7) The normal and pathological anatomy as described by Crock (5), the lumbar nerves emerge at their respective intervertebral foramina lying inferior to the lumbar pedicle. The intervertebral foramen is bounded above and below by the vertebral pedicles. Its floor from above downwards is formed by the postero-inferior margin of the superior vertebral body, the intervertebral disc and the posterosuperior margin of the inferior vertebral body. The roof is formed by the ligamentum flavum, terminating at its outer free edge, and posteriorly lies the pars interarticularis and the apophysial joint, formed between the adjacent inferior and superior vertebral facets. The vertical height of the foramen is determined by the vertical height of the corresponding intervertebral disc space. The development of foraminal stenosis is related to the process of lumbar spondylosis. The loss of intervertebral disc height secondary to desiccation and degeneration allows the superior articular process of the inferior vertebra to subluxate anteriorly and superiorly, diminishing the area of the foramen (Fig.1).

Methods:
Prospectively collected outcomes data for 27 consecutive patients undergoing single or double ALIF to treat L5 radiculopathy due to foraminal stensosis was reviewed. All cases were selected and operated on by one surgeon. VAS for pain assessment is a simple assessment tool consisting of a 10 cm line with 0 on one end, representing no pain, and 10 on the other, representing the worst pain experienced, which a patient marks to indicate the severity of his or her pain (9) The Oswestry Disability Index and Roland-Morris Questionnaire (RMQ) were used to assess functional disability. Radiological assessment was performed using erect plain x-ray and MRI scan preoperatively.

Demographics

The number of patients in the study was 27, with 17 men and 14 women.
Unfortunately 3 patients were lost to follow up. The average age was 54.4 years and
the age ranged from 30 years to 76 years. Average follow-up period was 6 months.
Out of 24 patients available for a follow up 20 patients underwent single level ALIF
and 4 patients underwent two level ALIF 

Types Of cases

Operating time for single level was from 100 – 195 minutes, the average time was 138.16 minutes. Length of stay in hospital for a single level ALIF varied from 2 to 6 days, with an average of 3.3 days. For a two level ALIF hospital stay varied from 4 to 5 days, with an average of 4.3 days.

Surgical Technique

In all the cases a retroperitoneal approach to the anterior lumbar spine was performed after harvesting autogenous graft from the right iliac crest. Following clearance of the disc space a laminar spreader was introduced and a ronguer was used to clear the disc annulus and osteophytes from the foramen. If the posterior annulus was solidly calcified, a burr was used to achieve foraminal decompression. An interbody device

packed with the harvested graft was then secured by four screws in the intervertebral space to restore disc height

Results

Complete data was available for 24 out of the 27 patients. Of the 3 lost to follow up one had a bad outcome despite undergoing a technically successful procedure. He withdrew from the study. A 2nd patient had an excellent clinical result from the surgery based on post procedure follow-up. However, due to inadequate pre procedure data the patient was excluded. The 3rd patient has been lost to follow up and did not attend post procedure follow-up. A statistical package (STATA) and the Wilcoxin Signed Rank Test were applied to interpret the data. Of the 24 patients with complete data there was clinically and statistically significant improvements in all measured parameters at 3 and 6 months for both degenerative disc and spondylolisthesis cases (Table 2, 3&4). The VAS

(Graph 1)

improved from a mean pre-op of 6.5 ( 95 % CI 5.9 - 7.1) to 1.3 ( 95% CI 0.8 - 1.8) at 3 months and 0.9 ( 95%CI 0.5 - 1.3) at six months ( p< 0.0000). Oswestry scores

improved from a mean pre-op of 36.8 (95% CI 31.5 - 42.1) to 12.1 (95% CI 6.8 - 17.4) at 3 months and 8.8 ( 95%CI 4.4 - 13.2) at six months ( p< 0.0000). Roland Morris scores

improved from a mean pre-op of 11.0 (95% CI 9.1 - 12.9) to 1.9 (95% CI 0.8 - 3.0) at 3 months and 1.6 (95%CI 0.7 - 2.5) at six months (p< 0.0000). Hospital stay, overall cost and complication rates are favorable when compared to current available alternative surgical procedures.

Discussion

Loss of disc height results in the displacement of facets and an overall reduction in size of intervertebral foramen (4) in a cadaveric study Hasegawa et al demonstrated that a significant nerve root compression is associated with a foraminal height of less than 15 mm and posterior disc height of 4 mm (14). A loss of disc height by 4 mm, which is 35-50% of its normal height results in a reduction in the diameter of the neuroforamen (15). Previous studies have shown a total increase in AP diameter after anterior fusion appears to be directly related to the clinical outcome (16). A study by Chan and Fay showed an increase in the volume of the neuroforamen by 22.9% for L4-5 and 21.5% for L5-S1, the posterior disc height increased by 37.1 % at L4-5 and 45.1% at L5-S, following BAK instrumentation(4).

Anterior procedures that restore the height of the disc space can indirectly enlarge a stenosed neuroforamen. Anterior interbody fusion also corrects mal-alignment of the lumbar spine and reduces anterior slippage. The several advantages of anterior interbody fusion(12) are direct observation of the anteriorly displaced vertebral body, avoidance of damage to the posterior supporting ligaments, dura mater and nerve root; reduced need for blood transfusion, early postoperative ambulation and a reduction hospital stays, eradication of postoperative back pain and/or radiating pain; and a high fusion rate (17,26)

Various previous studies have shown satisfactory clinical results for back pain with anterior lumbar interbody fusion. (2,18,19,20,21,22) Kim and Lee (18) reported no significant difference in clinical outcomes and fusion rates between anterior interbody fusion and posterolateral fusion with transpedicular fixation for isthmic spondylolisthesis in Adults.

Greenough et al (24) demonstrated posterior instrumental fusion higher fusion rates (82%) compared (25) to anterior fusion (76%) but with better clinical results in the latter procedure. Pradhan’s (26) study showed the anterior approach to single-level lumbar fusion is associated with less morbidity than the postero-lateral approach with no significant difference in need for transitional facility care, complication rates, and given followup period in radiographic fusion rate and clinical outcome. Above mentioned studies have previously shown advantages of ALIF over other procedures in terms of avoidance of damage to the posterior musculature, ligaments, neural structures,

reduced need for blood transfusion, early postoperative ambulation and reduced hospital stay. In conclusion our study has shown that ALIF is an excellent option for the treatment of L5 radiculopathy due to foraminal stenosis as results are consistent with a significant improvement in disability, faster postoperative recovery, earlier return to employment, reduced operating time and is more cost effective compared to other available treatment options.

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