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ORIGINAL ARTICLE
Year : 2014  |  Volume : 27  |  Issue : 1  |  Page : 191-196

Posterolateral fusion versus posterior interbody fusion in adult lumbar isthmic spondylolisthesis


Department of Neurosurgery, Faculty of Medicine, Menoufia University, Shibin Al Kawm, Egypt

Date of Submission20-Nov-2013
Date of Acceptance05-Jan-2014
Date of Web Publication20-May-2014

Correspondence Address:
Hosam A.M. Habib
MD, PhD, Department of Neurosurgery, Faculty of Medicine, Menoufia University, Shibin Al Kawm, 27 Dr. Sayed Fahmy St. Sidi Gaber Alexandria 21431
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.132800

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  Abstract 

Objective
The aim of this study is to assess and compare the outcomes of posterior lumbar interbody fusion (PLIF) and posterolateral fusion (PLF) in adult isthmic spondylolisthesis.
Background
Both PLIF and PLF have been used widely in the treatment of lumbar degenerative spinal diseases. Although PLIF has theoretical and demonstrable advantages over PLF, many authors did not observe this and report that outcomes of both surgical methods are comparable.
Materials and methods
Fifty patients with lumbar spondylolisthesis were operated for isthmic spondylolisthesis complaining of low back pain with or without sciatica and neurogenic claudication. The patients were allocated randomly to two groups according to the mode of bony fusion into PLIF and PLF groups. The two groups were statistically similar with respect to demographic and clinical data.
Results
No significant differences were found between PLIF and PLF in blood loss, short-term postoperative clinical result, or complications, but the operation time was longer with PLIF. Postoperative long-term visual analogue scale (VAS) for back pain, the Oswestry disability index, and fusion rates were significantly better in PLIF.
Conclusion
PLIF seems to be a better bone fusion technique than PLF in the management of isthmic spondylolisthesis.

Keywords: Lumbar fusion, posterior lumbar interbody fusion, posterolateral lumbar fusion, spondylolisthesis


How to cite this article:
Habib HA. Posterolateral fusion versus posterior interbody fusion in adult lumbar isthmic spondylolisthesis. Menoufia Med J 2014;27:191-6

How to cite this URL:
Habib HA. Posterolateral fusion versus posterior interbody fusion in adult lumbar isthmic spondylolisthesis. Menoufia Med J [serial online] 2014 [cited 2017 Oct 22];27:191-6. Available from: http://www.mmj.eg.net/text.asp?2014/27/1/191/132800


  Introduction Top


Isthmic spondylolisthesis surgery aims to accomplish fusion and neural decompression with or without instrumentation, to correct the present instability, and alleviate pain. In 1889, Hadra [1] described the use of wires in treating spinal deformities caused by Potts disease. Later, Albee [2] and Hibbs [3] each presented variable successful methods to prevent progressive kyphosis in Potts patients and scoliosis treatment utilizing autogenous bone grafts derived from the spinous processes or tibia or iliac crest, which were placed on-lay of decorticated laminae to achieve fusion. Unfortunately, the high incidence of pseudoarthrosis in their series necessitated prolonged postoperative immobilization and external orthosis. Posterolateral fusion (PLF) was an improvement of these techniques, where the side of the vertebral bodies and transverse process were decorticated and bone grafts were placed on-lay to allow intertransverse process fusion, minimizing the risk of neobone formation into the neural canal. Because of the ease and good fusion rates with PLF, it has and still remains one of the largely used posterior fusion techniques [4].

Cloward [5], in 1952, placed the bone grafts anteriorly between the vertebral bodies, promoting fusion to occur through the disk space, while decompressing the spinal canal posteriorly by performing a laminectomy. This was the first introduction of the posterior lumbar interbody fusion (PLIF) technique. The possible risk of root injury caused by excessive retraction minimized the use of this technique by many surgeons. In the past two decades, there has been a resurge in the use of this technique because of innovations in the surgical instruments, which minimizes the amount of retraction and possibility of nerve injury, while providing the theoretical advantages of PLIF including preservation of sagittal balance and disk height [6],[7],[8].

To date, both PLF and PLIF are widely used fusion techniques, applied during spondylolisthesis surgery. Several studies have shown that PLIF has theoretical and demonstrable advantages over PLF [9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19], whereas others report that the outcomes of both techniques are comparable [11],[13],[14]. Thus, the aim of this series is to compare the outcomes of PLIF and PLF.


  Materials and Methods Top


Fifty patients with lumbar spondylolisthesis in the period between 2007 and 2011 were operated for isthmic spondylolisthesis. The surgical indication was persistent low back pain with or without neurological compromise that failed to respond to 6 months of conservative treatment. These patients were then allocated randomly to two groups according to the mode of bony fusion into PLIF and PLF groups. The two groups were similar with respect to grade of slipping, sex, age, and activity.

After induction of anesthesia, the patients were placed in the prone position. Posterior spinal column and the transverse processes were exposed through a posterior midline incision. Excision of mobile laminae, including the attached spinous processes and inferior facet, was performed in addition to medial facetectomy and foraminotomy to achieve proper thecal sac decompression as well as the roots existing at the motion segment. The excised bone was kept for use as bone grafts after careful removal of any attached soft tissue. Pedicle screw instrumentation was carried out in all patients with care not disrupt the upper facet joint.

In the PLIF group, an almost complete diskectomy and end-plate decortication was performed. Intervertebral disk space spreaders were then sequentially inserted and rotated to restore the normal disk space height. The disk space was then packed with the laminectomy bone, starting with the smaller bone chips anterior and larger ones mainly consisting of a large portion of the lamina, which is sculptured to fit anterior to the posterior vertebral borders, to act as a mechanical barrier to prevent escape of the smaller bone chips.

In the PLF group, high-speed drilling of the side of the remaining parts of the facet joints and transverse processes was performed bilaterally for decortication, followed by on-lay placement of laminectomy bone chips bilaterally. All patients used a soft lumbar corset for 3 months.

A minimum 18-month follow-up was available in all patients. For clinical evaluation, the patients visual analogue scale (VAS) scores for leg and back pain were administered at 6-monthly intervals, where the sixth postoperative month was considered the short-term VAS and those obtained at 18 months or later were considered the long-term VAS.

The Oswestry disability index (ODI) [20] questionnaire with its 10-item ordinal scale (pain intensity; personal care; ability to lift, walk, sit, stand, and sleep; sex life; social; and traveling; each item had six responses, where 0 was normal functionality and 5 the worst, and the sum of these is multiplied by two, thus providing a worst sum of 100 and a best of 0) was administered in a similar manner as the VAS [21].

Anteroposterior, lateral, and dynamic radiographs views were performed at 3, 6, 12, and 18 month postoperatively for all patients, and, if possible, in subsequent visits, where the last was considered the final follow-up. Rarely computed tomography was utilized when fusion was questionable. 'Solid bony fusion' was considered when a bridging bony trabecular continuity and a mobility of less than 4° were documented radiographically [22]. In this study, failure to achieve this by the end of the first postoperative year was considered a failure of fusion. Posterolateral spinal fusion was evaluated according to the Christensen classification [23], where the formation of a continuous intertransverse bony bridge at a minimum of one of the two sides indicated fusion at that level. The operative duration, postoperative complications, and need for a second surgery were assessed.

Statistical analysis

The data were collected and analyzed using the Statistical Package for Social Sciences (SPSS, version 17; SPSS Inc., Delaware, USA) software. Arithmetic mean, SD, number, and percent were calculated. For categorized parameters, the χ2 -test was used, whereas for numerical data, the t-test was used to compare two groups. The level of significance was 0.05.


  Results Top


The study included 29 female and 21 male patients, with mean ages of 52.7 years in the PLIF group and 51.3 years in the PLF group. The two groups were statistically similar with respect to demographic and clinical data, which are summarized in [Table 1].
Table 1: Demographic characteristics of the patients

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The minimum follow-up period in each group was 18 months. The mean follow-up period was 26 months (range, 18-46 month) for the PLIF group and 29 months (range, 20-52 month) for the PLF group; the difference between the two groups was not significant.

The mean operative time for single-level surgery was 110 min in the PLF group (range, 85-125 min) compared with 125 min (range, 100-140 min) in the PLIF group, whereas the mean operative time for double-level surgery was 140 min (range, 110-155 min) in the PLF group and 160 min (range, 140-185 min) for the PLIF group; these differences were significant (P < 0.05). Perioperative blood loss was 750 ml (range, 250-1100 ml) for patients in the PLF group and 850 ml (range, 450-1400 ml) for patients in the PLIF group: this difference was not significant [Table 2].
Table 2: Operative data and complications

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There were three perioperative complications in the PLF group: a dural tear in a patient, and postoperative aggravation of the radicular pain in two patients. In the PLIF group, two patients had probable dural tears detected postoperatively by the occurrence of postural headache and cerebrospinal fluid through the drain; both were self-limited and required no intervention. In addition, four patients had transient de-novo parethesia, related to radicular manipulation and not actual root injuries, and they resolved spontaneously [Table 2].

Radiological fusion was confirmed in 24 patients (96%) of the PLIF group [Figure 1] and 17 patients (68%) in the PLF group [Figure 2] by the end of the first year. None of the patients who failed to achieve fusion had achieved it in their later visits despite incomplete resorption of the bone chips. The difference in the prevalence of fusion between the two groups was significant (P = 0.0442).
Figure 1:

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Figure 2:

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The average short-term visual analogue score for leg and back pain, measured at the sixth postoperative month, showed improved leg pain from 65 preoperatively to 30, whereas back pain improved from 73 preoperatively to 35 in the PLF group and the PLIF leg pain from 68 to 24 and back pain 75 to 30, but the difference between the two groups was not significant (P > 0.05). The final follow-up visual analogue score for leg and back pain showed improved leg pain in both PLF and PLIF groups to 22 and 25, respectively, whereas back pain improved in PLIF to 22 and increased to 40 in the PLF group; the difference between the two groups was significant (P = 0.002) in terms of long-term VAS for back pain [Table 3].
Table 3: Visual analogue score (VAS) for leg and back pain

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There was a marked reduction in the preoperative ODI [Table 4] from that recorded in the final examination. The PLF group had a mean preoperative ODI of 38.5 (range, 22-82) that was reduced to a mean of 25.1 (range, 2-55) at the final postoperative follow-up. However, in the PLIF group, it was reduced from 36.9 (range, 24-68) preoperatively to 16.2 (range, 0-36). The difference between the two groups was significant (P = 0.0058).
Table 4: Oswestry disability index (ODI)

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Eight patients (16%) underwent a second surgery, all of whom had radiological nonfusion: a patient (4%) from the PLIF group because of the occurrence of pseudoarthrosis and persistence of severe back and seven patients (24%) from the PLF group for persistent severe back pain and, loosening of the screw caps in two cases and screw breakage in one [Figure 3]. In their second surgery, PLIF was performed. The difference between PLIF and PLF was significant (P < 0.002).
Figure 3:

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  Discussion Top


After Clowards' [5] first description of PLIF in 1952, he later published the data of 165 patients who underwent PLIF for spondylolisthesis, where a fusion rate of 93% and excellent clinical results in 95% of the patients were recorded [24]. In another series of 465 patients who were studied by Lin [25] in whom PLIF was performed for various spinal degenerative pathologies, a satisfactory clinical outcome was found in 82% of the patients, whereas 88% had radiographic fusion.

Ray [16] reported a radiographic fusion rate of 96%, and a clinical outcome of good to excellent in 65% in his series after a follow-up duration of 2 years; he reported that PLIF reduced the mechanical stresses in the fused segment and prevented the possible leakage of chemical irritants (such as phospholipoic acid from the disk space), and led to a reduction in the pseudoarthrosis rate with an improvement of clinical outcome, especially if augmented by instrumentation. Similarly, Brantigan et al. [26] reported a 98.9% fusion rate and 86% clinical success in their PLIF series when augmented by posterior instrumentation.

Dantas et al. [27] reported that PLIF augmented by transpediclular screws led to better clinical outcomes, Prolo economic, and functional scales, and fewer complications when compared with PLF. This is in agreement with the results obtained in this study.

La Rosa et al . [28] support the view that PLIF confers a superior mechanical strength to the spinal construct, whereas in PLF, there is a progressive reduction in the correction achieved, but not to the extent to affect the clinical outcome.

Deuhoux et al. [29] reported that fusion rates are directly proportional to the degree of slippage and disk height, while not affecting the functional outcome. Hence, they prefer to use PLIF for high-grade spondylolisthesis requiring reduction or if the disk space is still high, whereas in low-grade slippage, or narrow disk spaces, PLF is preferable.

Musluman et al. [30] reported a clinical outcome of good or excellent in 22 (88%) cases in the PLIF group and 19 (76%) cases in the PLF group. Fusion ratios were 100% in the PLIF group and 84% in the PLF group. Both lumbar lordosis and the segmental angle showed greater improvement in the PLIF group, but there was no difference in the complication rates for each group.

Ekman et al. [11] reported that the results of PLIF and PLF in the surgical management of adult isthmic spondylolisthesis were comparable in the patient outcome at the end of their 2-year follow-up. In this study, there was a significant difference between both techniques in favor of PLIF, and this was the basis for its application in the patients who needed a second surgery. In contrast, Mada n et al. [31] reported better clinical outcome in low grades of isthmic spondylolisthesis with PLF than PLIF, although they report that PLIF fusion is more predictable in maintaining correction and achieving union.

Wu et al. [32] reported a significant reduction in both pain and Oswestry disability indices for both PLIF and PLF groups, where 88% of the patients in the PLF group and 91% of the patients in the PLIF group had radiological fusion, which was statistically insignificant. Although both techniques were comparable in terms of the outcome, PLF had greater tendency for hardware failure than the PLIF group, which was statistically insignificant.

There is a general consensus that PLIF is a cumbersome procedure, where the surgeon might be faced with excessive bleeding and a protracted operative time [33], but with practice, it should not pose a technical challenge. In the present study, there was no significant difference in the perioperative blood loss between the PLF group and the PLIF group. However, impacting the bone and sculpturing the most dorsal bone graft did lengthen the procedure by an average of 15 min per level. These results are similar to those obtained by Suk et al. [34].

Despite the longer duration of procedure with the PLIF technique, it seems justifiable owing to the high fusion rates reported by many authors for interbody fusion [9],[10],[11],[13],[14],[15],[16],[18],[19], and the overall superior reliability and resistance of the implanted systems associated with the PLIF procedures rather than PLF procedures, because of reduced mechanical stress conferred to the hardware [Figure 4], minimizing their failure as confirmed by several authors as well as this study [32],[35],[36].
Figure 4:

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  Conclusion Top


PLIF seems to be a better option for the management of isthmic spondylolisthesis on the basis of the better clinical outcome and higher fusion rates and fewer construct failures found in this study.


  Acknowledgements Top


The funding resources were provided by the Department of Neurosurgery, Faculty of Medicine, Menoufia University.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
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