Single Space Transforaminal Lumbar Interbody Fusion in Spondylolisthesis: Initial Experience of 30 Cases

Spondylolisthesis in adults is characterized by the loss of disc height across the affected segment with sagital translation. The goal of stabilizing the spine is accomplished by fusion. Transforaminal approach for lumbar interbody fusion is a very good approach and reduces the complications associated with traditional posterior approach. It has been reported to be safe and effective in the treatment of spondylolisthesis. It has done to assess the functional outcome of Transforaminal Lumbar Interbody Fusion (TLIF) in spondylolisthesis. This prospective interventional study was performed from July 2008 to June 2011 included 30 patients (male 07, female 23), within a age range of 30-59 years. Nineteen cases were lytic, 08 cases were degenerative, 02 were post-traumatic and 01 dysplastic variety of spondylolisthesis. Follow up ranged from 12 to 24 months and outcome assessed by VAS and ODI regarding pain and disability. Achievement of fusion and complications were documented accordingly. Statistical analysis was done by unpaired t-test and chi-squared test in appropriate instances. We included twenty 0ne (70.00%) patient had Grade-II Spondylolisthesis and L 4 over L 5 had been the commonest level (53.33%) involved. Pain and disability improved significantly and 22 (73.33%) patients returned to their previous level of activity. One (03.33%) patient developed superficial wound infection and 01 (03.33%) had persistent low back pain. All patients had neurological improvement. We concluded that Transforaminal Lumbar Interbody Fusion is an effective alternative surgical procedure for the treatment of spondylolisthesis. Overall outcome is satisfactory in 93.33% cases.


Introduction
Spondylolisthesis is a common condition and is defined as the forward shift of the spinal column 1 which is characterized by a failure of the threecolumn support with severe complex instability requiring reconstruction 2 .The extent of the slip is usually graded using the Meyerding classification 3 in which the displacement of one vertebral body on another is divided into four equal parts.Grades I and II represent up to 25% and 50% displacement respectively and cover the majority of cases, are referred to as low-grade slips.The initial management of the condition is conservative.When this is deemed to have failed, surgery is considered.Surgery is indicated to prevent further progression of slip, to relief back and leg pain, reverse the neuro-deficit and stabilize the segment 4 .Posterolateral fusion has long been considered the "gold standard" for surgical treatment of adult spondylolisthesis.
Superior results have subsequently been reported with interbody fusion with cages and posterior instrumentation 5 .

Interbody fusion techniques have been developed
to provide solid fixation of spinal segments while maintaining load-bearing capacity and proper disc height 6 .The ability to reconstruct the anterior column is important because 80% of the compressive, torsion, and shear forces are transmitted through the anterior column 7 .The two methods of achieving an interbody fusion from a posterior approach are Posterior Lumbar Interbody Fusion (PLIF) and Transforaminal Lumbar Interbody Fusion (TLIF) 8 .Since Harms and Rolinger 9 introduced transforaminal lumbar interbody fusion (TLIF), TLIF has been performed as an alternative to conventional posterior lumbar interbody fusion (PLIF) 10 .TLIF is an alternative interbody fusion procedure in which interbody space is accessed via the far lateral portion of the vertebral foramen 11 .It has several advantages over other fusion methods 12 and the clinical outcomes associated with TLIF have been reported to be comparable to those of PLIF or Anterior Lumbar Interbody Fusion (ALIF) 13 and has been reported to gain popularity world wide 14 .This technique is very new in Bangladesh and performing in our University and other private hospitals.We have performed this study with an aim to assess the outcome of TLIF in Spondylolisthetic cases.

Materials and Methods
This prospective interventional study was performed from July 2008 to June 2011 in our official and private setup.The patients with unstable Spondylolisthesis grade I-II were included but with the followings were excluded: i) Spondylolisthesis >grade II; ii) Previous history of spondylo-discitis; iii) Medically unfit patients.We included 30 patients (male 07, female 23); within an age range of 30-59 years.All the patients were evaluated preoperatively by X-ray L/S spine A/P, Lateral ] was done routinely to delineate the intra spinal neurological condition.Nineteen cases were lytic, 08 cases were degenerative, 02 were post-traumatic and 01 dysplastic variety of spondylolisthesis.The L 4/5 level was involved in 17 cases, L 5 /S 1 level in 10 cases and L 2/3 level in 03 cases.Fourteen patients had sensory involvement, 10 patients had motor involvement and 05 had loss of reflexes.
Follow ups: Follow up ranged from 12 to 24 months and outcome assessed regarding pain, disability and achievement of fusion.All the cases were evaluated both preoperatively and postoperatively regarding the clinical outcome and improvement of pain and disability status.Follow up was consecutively at 3 months, 6 months and 12 months followed by 6 months interval thereafter.All the patients were evaluated clinically to assess the neurological status.Assessment: We assessed the patients with Visual Analogue Score (VAS) 15 and Oswestry Disability Index (ODI) 16 at every follow-up.Every patient had done check X-ray L/S spine A/P and lateral view [Figure-1 (d), (e) and Figure-2 (d), (e)] and send to a radiologist for comments about the fusion status with blinding.Computed Tomography (CT) scan had been reserved for cases where radiological fusion was doubtful or in cases with pseudoarthrosis.The patients were documented with the standard VAS and ODI questionnaire to assess the improvement of the pain and disability status in every follow-up.We have graded the overall comprehensive outcome of the study by the Macnab`s criteria 17 as follows; Excellent: Full recovery of symptoms and no restriction of occupational or daily activities; Good: Residual or occasional symptoms but able to continue normal activities; Fair: Partial recovery of symptoms, unable or difficulty to continue work; Poor: No recovery or worsening of symptoms.Statistical analysis was done by unpaired t-test and chisquared test in appropriate instances.
The operative technique: We used the posterior midline incision followed by subperiosteal muscular dissection.The lateral margin of the facet joints as well as the transverse processes was identified to determine the site of pedicle.Pedicle screws were inserted using the freehand technique and checked for proper placement by C-arm.Unilateral laminotomy and partial facetectomy were performed on the side consistent with the patient's symptoms.The disc space was gradually distracted by using the pedicle screws and rods with distractors.Annulotomy done over the posterolateral portion of the annulus and the entire discs were removed.Endplates was curetted out by the specially designed box currettes with carefully protecting the thecal sac and nerve roots.We took the morcelized bone grafts from the excised spinous process and parts of laminae and introduced to the anterior part of the disc space and impacted with an impactor.The serial cage template was inserted and the interbody cage of appropriate size, packed with bonegraft was placed within the space and checked for proper positioning.Once the cage with graft has been placed, pedicle screws are then attached to lordotic rod

Results
The

Discussion
TLIF is a very good alternative technique which can theoretically prevent typical disadvantages of those seen in anterior and posterior lumbar interbody fusion 18 .Hee et al 19 compared TLIF with combined anterior and posterior fusion concluding that TLIF patients had a shorter operative time, less blood loss and shorter hospital stay compared to single stage anterior and posterior fusion.Humphreys et al 20 compared Posterior Lumbar Interbody Fusion (PLIF) and TLIF showing that TLIF had a much lower complication rate.Brislin and Vaccaro 21 have reported lower risk of nerve tethering in TLIF compared to traditional PLIF.These study reports had definite influence regarding the adoption of TLIF as a surgical method of choice.The operating time was 190 minutes averaged in our series and preoperative blood loss in our single level surgical intervention was average 215ml and required only 1 unit of blood transfusion almost in every case.We ended up with superficial wound infection in 02 cases which were improved by broad spectrum antibiotic administration according to sensitivity report and regular dressing.One case needed debridement.Elmasry et al 22  The study had limitations because we had no cases to include with unstable upper lumbar spondylolisthesis or even multiple level instabilities requiring fusion, without which a rational conclusion of using TLIF is difficult to determine.A larger sample size with a long period study might include such cases.The period of study is not sufficiently long to conclude regarding more specified outcome regarding the hardware and its long-term functional and structural effect.Studies with larger population comparing with the specialized centers would help to find out even more advanced method of surgical management.

Conclusion:
Transforaminal lumbar interbody fusion is an effective method for surgical management of low grade spondylolisthesis.The complications rate is less and provides good fusion and functional outcome.
[Figure-1(a) and Figure-2(a)] and oblique view.Flexion-extension films were done to assess the instability.MRI of the L/S spine [Figure -1(b) and Figure -2(b)

Fig. 1 :
[Figure-1(c) and Figure-2(c)] and compressed to restore the lumbar lordosis.The exiting nerve roots were decompressed and the traversing roots were checked for any residual compression.Laminae and the remaining contralateral facet joint are decorticated, and packed with local autologous graft taken from the excised spinous process and part of laminae.The lateral intertransverse space was also packed and wound was closed with a drain insitu.Patient with grade-II Spondylolisthesis with instability at L5 over S1.The preoperative A/P and lateral view of L/S spine (a,b); The intraoperative view of instrumentation (c); The A/P film showing the sagittal orientation of hardware (d); The Postoperative lateral film showing restoration of anatomy and good position of hardware (e).

Fig. 2 :
Patient with grade-I Spondylolisthesis with instability at L4 over L5.The preoperative A/P and lateral view of L/S spine (a,b); The intraoperative view of instrumentation (c); The A/P film showing the sagittal orientation of hardware at 1 year follow up (d); The lateral film of same follow up showing restoration of anatomy and good position of hardware and achievement of fusion (e).

Table - I
: Demographic variables of the patients.(n=40) All the patients returned to their previous level of activity except 01 with infection requiring debridement.The patient needed occasional analgesics to get relieved from pain which was limiting his level of activity.Satisfactory (Excellent and good) results were achieved in 37 (93.33%)cases.Elmasry et al 22 reported 90% excellent or good result with 91% fusion in his series of 30 patients with low grade spondylolisthesis treated by TLIF.Yehya 23 found 73.30% excellent and 26.70% good result with TLIF in 30 patients with spondylolisthesis.Lowe et al 24 reported 85% good and excellent clinical results, with 90% radiological fusion in his series of TLIF with two cages.