Published online Dec 31, 2011.
https://doi.org/10.4184/jkss.2011.18.4.208
Comparative Study of the Clinical Outcomes of Unilateral Transforaminal Lumbar Interbody Fusion(TLIF) with Bilateral TLIF using Wiltse Approach and Conventional Approach
Abstract
Study Design
Comparative study.
Objectives
To compare the outcomes of unilateral TLIF, bilateral TLIF using Wiltse approach and bilateral TLIF using conventional midline approach.
Summary of Literature Review
There are many studies about outcomes of Unilateral TLIF, but few have compared the 3 different fusion procedures.
Materials and Methods
60 patients were divided into 3 groups. Each group has enrolled 20 patients (Study group: unilateral TLIF, Control group 1: bilateral TLIF using Wiltse approach, Control group 2: bilateral TLIF using conventional midline approach). For clinical outcomes, we compared operative time, blood loss, time for ambulation and discharge, VAS for back pain and leg pain and ODI among three groups. For radiologic evaluation, disc height and segmental lordosis were examined.
Results
The mean operative time was 147 minutes in study group(SG), 172 minutes in control group 1(CG1), 167 minutes in control group 2(CG2). The mean total blood loss was 466ml in SG, 569ml in CG1, 1140ml in CG2 respectively. VAS for back pain at the third postoperative day significantly decreased in SG and CG1 compared with CG2. There was no significant difference in ODI, disc height and segmental lordosis among the groups.
Conclusion
Using Wiltse approach, there were several advantages in decreasing blood loss, immediate postoperative back pain, hospital stay and early ambulation. Clinical and radiological results of unilateral TLIF were comparable with bilateral TLIF.
INTRODUCTION
Spinal decompression and fusion is commonly performed to relieve symptoms of lumbar degenerative diseases such as spinal stenosis or spondylolisthesis and there are various surgical approaches. Conventional posterior mid-line approach is the most well-known among these but complications associated with muscle damages due to extensive mediolateral muscle stripping has been reported.1) To overcome this problem, Wiltse approach advancing through between multifidus and longissimus muscle was reported and most recently, minimally invasive direct approach using tubular retractor was introduced and being used widely.2-4) As advantages of posterior interbody fusion were recognized and became popular, terms such as posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF) and extreme lateral interbody fusion (ExLIF) have been used. It is also possible to insert cages filled with autogenous or allogeneic bone graft unilaterally or bilaterally. Among these, unilateral transforaminal lumbar interbody fusion (unilateral TLIF) was developed by modifying established PLIF and was reported by Harms and Jeszenszky5) in 1998. With Developments in minimally invasive spinal surgery, minimal invasive TLIF using tubular retractor or other instruments has been introduced and satisfactory results have been reported since the early 2000s.6) However, minimal invasive TLIF required longer operating time due to the limited exposure and disadvantages such as doubts about sufficient decompression or challenging situation to solve complications such as accidental dural tear during the procedure were emerged. It was also questionable whether sufficient pressure could be applied to the interbody space through percutaneous pedicle screws. For these reasons, the authors took interest in the unilateral TLIF with Wiltse approach. This study aimed to compare the clinical and radiological outcomes of unilateral TLIF, bilateral TLIF using Wiltse approach and bilateral TLIF using conventional midline approach in the patients with degenerative spinal disease who complaining of back pain and radiating leg pain and discuss them with literature review (Fig. 1).
Fig. 1
Schematic illustrations show the three different fusion procedures. (A) Unilateral TLIF (B) Bilateral TLIF using Wiltse's approach (C) Bilateral TLIF using conventional midline approach
MATERIALS AND METHODS
1. Materials
From April 2006 to May 2008, 20 patients who had undergone contiguous unilateral TLIF procedure among those patients who needed surgical procedure due to their recurrence of symptoms that had been treated with selective epidural nerve root block were enrolled Study Group(SG). For a comparative study, through a retrospective analysis of a medical records, 20 contiguous surgical cases that had received interbody fusions through different methods but showing similar surgical indications were selected. Control Group 1(CG1) was comprised of 20 cases that had undergone bilateral TLIF using the bilateral Wiltse approach since 2003. Control Group 2(CG2) was comprised of 20 cases that had undergone bilateral TLIF using conventional posterior mid-line approach since 2001. The SG had 7 male and 13 female patients, the average age was 57.5 years (52-66), the average follow-up period was 38.2 months (24-47), there were 5 cases of spinal stenosis and 15 cases of spondylolisthesis. The CG1 had 6 male and 14 female patients, the average age was 60.1 years (55-67), the average follow-up period was 52.8 months (24-79), there were 7 cases of spinal stenosis and 13 cases of spondylolisthesis. The CG2 had 7 male and 13 female patients, the average age was 56.6 years (49-65), the average follow-up period was 46.3 months (24-60), there were 8 cases of spinal stenosis and 12 cases of spondylolisthesis.
2. Surgical methods
All surgeries were performed under general anesthesia in the prone position. The surgical procedure for the SG, conventional posterior mid-line approach was used for the symptomatic side which requiring decompressions surgery. Through the Wiltse approach that used the same incisions, pedicle screws were inserted for the opposite side. On the symptomatic side, after the facet joint was removed, posterior decompressions procedure was performed, then the over-the-top technique that decompressed also the opposite side was performed. After checking the disc space, performing discectomy and end plate curettage on symptomatic side, single cage with autogenous local and allogeneic chip bone was inserted in disc space. The cage was inserted in an oblique angle and centered in the disc space. Metal rods were connected with pedicle screws and fixated under appropriate compressive pressure (Fig. 2).
Fig. 2
These photographs show the unilateral TLIF procedures.(A) Conventional approach at symptomatic side (B) Unilateral disc preparation and cage insertion (C) Decompression of contralateral side (D) Wiltse approach at contralateral side (E) Pedicle screw insertion through Wiltse approach
In the case of bilateral TLIF using the Wiltse approach(CG1), a 3~4cm longitudinal incision was made in the midline and exposed the lumbodorsal fascia. Afterwards, made a fascial incision approximately 2cm lateral to the midline and entered between the multifidus and longissimus muscle. Multifidus muscle was retracted medially and the facet joint was exposed and pedicle screws were inserted. After removing the facet joint, decompressions and interbody fusion were done in both sides. Cages with autogenous local and allogeneic chip bone were inserted in both sides and metal rods were connected and fixated under appropriate compressive pressure.
In the case of bilateral TLIF using the conventional bilateral posterior approach(CG2), screws were inserted in both sides using a typical posterior approach, and afterwards, cages filled with local bones were inserted in both sides.
3. Clinical and Radiographic Analysis
For clinical analysis, the operative time, blood loss during and after surgery, time for ambulation, duration of hospital stay and complications were compared and evaluated for each group. In addition, preoperative and postoperative back pain and radiating pain were measured using the visual analog scale (VAS), and compared with the Control Groups. For clinical assessment of operation results, the Oswestry disability index was used. Radiological analysis was conducted with the images taken every 3 months. The determination criteria for interbody fusion were based on presence of a bony bridge in the anterior part of the cage, or less than 5° movement on lateral flexion and extension views, and less than 2mm radiolucencies around the cage and cage migration. If the fusion was uncertain, computed tomography was used to check the fusion had been completed. Changes in the anterior-posterior disc heights and segmental angle before and after surgery were measured. To compare the disc height with the upper vertebra height, regardless of the enlargement ratio of radiographs, the disc height was measured in percentage, with the height of the upper vertebra being 100%. Anterior and posterior disc heights were measured separately, and postoperative results were indicated in percentage, with 100% being the preoperative level.7) (Fig. 3). The Cobb method was used to measure changes of the segmental angle of fused vertebral segments.
Fig. 3
Radiographic measurement of anterior (A2/A1, original magnification × 100) and posterior disc heights. (P2/P1, original magnification × 100)
4. Statistics
All data were processed using the SPSS statistical program. For discontinuous variables, the χ2 test was used to calculate statistical significance. ANOVA test was used to analyze the statistical significance among the three groups, and the paired sample t test was used to verify the statistical significance within each group.
RESULTS
1. Clinical Results
The SG showed the shortest operative time with the average operative time of 147 minutes, and the CG1 showed the longest operative time with the average time of 172 minutes, meanwhile the CG2 showed the average operative of 167 minutes. The average blood loss during surgery was 212 ml in the SG, 254ml in the CG1, 486ml in the CG2. SG and CG1 had a significantly less blood loss than the CG2. The average blood loss after surgery were 253 ml in the SG, 315ml in the CG1, 653ml in the CG2. CG2 had a significantly large amount of blood loss than SG and CG1. The average time for ambulation was 3.1 days in SG, 3.4 days in CG1 and 4.7 days in CG2, respectively. In the SG and CG1, which were significantly faster than the CG2. In the SG and CG1, in terms of the average duration of hospital stay were 5.1 days and 6.5 days, respectively. These results were much shorter than the 7.9 days in the CG2 and earlier discharges were possible (Table 1). The average VAS for the postoperative pain after the third day of the surgery were 3.1 and 3.3 for the SG and the CG1, respectively and these were significantly lower than the CG2's 6.1. However, the differences gradually decreased and there were no differences at final follow-up. The postoperative radiating pain showed no difference among the three groups and there was no difference in Oswestry disability index among the three groups (Table 2).
Table 1
Operative and Perioperative Data
Table 2
Pain and Disability Scores at Follow-up
2. Radiographic Results
Bone fusion was confirmed by radiographs at the two-year follow-up. There was 1 case in the SG that was suspected of incomplete fusion, and CT scan was conducted to confirm and even the CT showed some signs of incomplete fusion, however there was not any particular symptom so the case is being observed. Other than this case, there were no cases of incomplete fusion in any of the 3 groups (Fig. 4). There was no statistical difference among the 3 groups in terms of the anterior and posterior disc height (Table 3). There was no difference among the 3 groups in terms of the segment angle (Table 4).
Fig. 4
These radiographs are taken from the patient who underwent unilateral TLIF at 2 years follow up. Suspicious nonunion is observed in these radiographs. (A, B) X-ray shows radiolucent area around the cage. (C, D) CT scan shows discontinuity of bridging bone in interbody space.
Table 3
Change of Disc Height
Table 4
Change of Mean Segmental Lordosis
3. Complications
Although in 2 cases from the SG showed paresthesia in the lower limb on the opposite side but the symptoms were disappeared in 3 months after the operation. 1 case from the CG1 showed superficial seroma, but this was eliminated with a conservative treatment. 1 case from the CG2 showed some symptoms of local infections, but the symptoms improved after 2 weeks of intravenous antibiotics.
DISCUSSION
As the effect of interbody fusion as compared to posterior or posterolateral fusion is recognized, the current trend indicates that opting for the interbody fusion is prevalent when it is possible. Interbody fusion is largely classified into anterior and posterior methods depending on the approach. Typical posterior fusion procedures are PLIF and TLIF. TLIF inserts a cage through a space made available after removing the facet joint, and compared to conventional PLIF, does not require excessive retraction of dura, which helps reduce neurologic complications. This is widely known and various forms of TLIF procedures have been reported due to this advantage. The unilateral TLIF published by Harms and Jeszenszky5) of Germany in 1998 was a conventional midline approach. This approach exposed both sides of the facet joint completely and performed unilateral facetectomy and inserted on one side 2 cages and posterior fusion was performed on the other side. The reports published after this by Humphreys8) and Lowe and Tahernia,9) their methods also were using conventional posterior mid-line approach. In 2003, Kim et al6) and Foley et al2) reported on a bilateral TLIF that combined minimally invasive approach that used tubular retractors. Recently, interest in minimally invasive spinal surgery gradually increased and there have been numerous reports on minimally invasive TLIFs. It was highlight that the postoperative back pain was reported to be lower since there was less damage to the soft tissues and this facilitated faster recovery in minimally invasive TLIF and it showed similar clinical outcomes comparing to the conventional midline approach.10-14) On the other hand disadvantages such as lengthy learning curve, longer operative time, high risk of complications and longer exposure to radiation also reported. In addition specially designed instruments and implants are required to perform minimally invasive TLIFs. The authors used to perform minimal invasive TLIF using tubular retractor system in the past but encountered potential problems such as incomplete decompression, insufficient compression through percutaneous pedicle screws after the cage insertion, inconvenience to deal with problems such as dural tear during the operation. For these reasons, the TLIF via Wiltse approach were performed and the clinically results indicating that there were no differences in terms of postoperative pains and recovery time compared to minimally invasive TLIFs were obtained. However it was possible to know that TLIFs using the Wiltse approach had shortcomings of limited surgical field of vision due to the existence of multifidus muscle medially which causes insufficient decompression and longer operative times. For these reasons, currently the side with symptoms is treated with decompression and interbody fusion using conventional posterior mid-line approach, and the opposite side with no symptoms is treated with a variation of unilateral TLIF using the Wiltse approach and insertion of pedicle screws. The authors' method enabled to reduce soft tissue damage, operative time and the blood loss by using conventional midline approach at only one side and Wiltse approach to the other side. Additionally, it was possible to ensure sufficient decompression and to perform direct compression with pedicle screw after the insertion of cages because the method facilitated to secure relatively wider visualization. Also it was possible reduce the additionally required skin incision and radiation exposure during percutaneous pedicle screw insertion. It was also possible to decompress the other side by approaching the affected side only when the over-the-top technique was performed with tilting of the patient and it was thought that postoperative neurological complications due to unnecessary neural irritation was avoidable. The possibility of occurrence of radiculopathy on the opposite side have been reported. We think that if the intervertebral foraminal space can be increased through insertion of relatively large height cage, the possibility of symptoms on the opposite side can be reduced. But it will be necessary to minimize the compressive pressure between pedicle screws on the unaffected side. Although there was no statistical difference in the operative times among the 3 groups, but the groups that underwent Wiltse approach were statistically lower in terms of the blood loss and postoperative pains indicated that there was less soft tissue damage. Since after 6 months and 2 years there were no differences in the back pain and radiating pain, the Wiltse approach has advantages in the short term right after an operation, and these advantages can be considered as results that there would be no long-term follow-up issues. Radiological results showed 1 case of incomplete fusion from the SG and we think that more thorough removal of soft tissues in the disc space when unilaterally inserting a cage.
CONCLUSION
The blood loss and postoperative pain was significantly lower in unilateral TLIF and bilateral TLIF comparing to the conventional TLIF and this facilitated the early ambulation and the early discharge. Unilateral TLIF showed similar clinical and radiological results with bilateral TLIF in patients with unilateral leg pains. Unilateral TLIF seems to be relatively easily accepted by the spine surgeons who are experienced in the conventional TLIF. Unilateral TLIF can be considered one of the various TLIF procedures that can be applied relatively easily.
References
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Foley KT, Holly LT, Schwender JD. Minimally invasive lumbar fusion. Spine (Phila Pa 1976) 2003;28 15 Suppl:S26–S35.
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Kim KT, Suk KS, Lee YH, Kim YW, Lee SH. The Posterior Decompression and Posterior Lumbar Interbody Fusion Using a Mini-open Technique - New Suggestion of Minimally Invasive Technique - A Prelimainary Report. J Korean Orthop Assoc 2003;38:492–497.
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Schwender JD, Holly LT, Rouben DP, Foley KT. Minimally invasive transforaminal limbar interbody fusion (TLIF): technical feasibility and initial results. J Spinal Disord Tech 2005 18 Suppl:S1–S6.
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