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COMPARATIVE STUDY BETWEEN INSTRUMENTED POSTEROLATERAL FUSION AND TRANSFORAMINAL LUMBAR INTERBODY FUSION IN ISTHMIC SPONDYLOLISTHESIS Samy Moussa Selim1, Reda Ali Shetta2 and Samer Ibrahim Alajouz3. 1- Lecturer of neurosurgery faculty of medicine for girls, Al-Azhar university, Cairo, Egypt. 2- Consultant of orthopedic, AlAhrar hospital, Zagazig, Egypt. 3- Consultant of orthopedic, AlAhsa hospital, KSA. ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ABSTRACT Background: Spondylolisthesis refers to slippage of one vertebra over the other, which may be caused by a variety of reasons such as degenerative, trauma, and isthmic. Surgical management forms the mainstay of treatment to prevent further slip and worsening. However, there is no consensus regarding the best surgical option to treat these patients. This study compares instrumented posterolateral fusion (PLF) and transforaminal lumbar interbody fusion (TLIF) in patients with isthmic spondylolisthesis and analysis the outcome with respect to clinical and radiological outcome. Materials and Methods: Twenty-six patients operated for spondylolisthesis by instrumented posterolateral or transforaminal fusion between October, 2012, and March, 2014 were included in this retrospective study. They were followed up for 8 to 48 months. Fourteen cases were PLF and twelve cases were TLIF. The patients were evaluated clinically and radiologically at preoperative, and at 1, 6, 12 and 24 months postoperatively and median value of postoperative results was taken to compare it with preoperative data. Results: Both procedures significantly improved the Oswestry Disability Index (ODI) and visual analog scale (VAS) scores; however, the postoperative ODI and VAS scores were unaffected by the procedure type. Postoperative disc heights and percent changes in disc heights did not change by operation type; however, the percent change in the foramen areas was significantly greater in the TLIF group. The addition of TLIF to the PLF procedure resulted in significantly longer operating time and more intraoperative blood loss. Cerebrospinal fluid fistula was the only major complication noted. The radiologic fusion rates were similar between both study groups. Conclusions: Both PLF and TLIF procedures were effective in ameliorating the symptoms of isthmic spondylolisthesis. Although some radiologic parameters favor TLIF, this was not reflected in the clinical outcomes. Key words: Posterolateral fusion, Transformational lumbar interbody fusion, isthmic spondylolisthesis. Abbreviation: ODI = Oswestry Disability Index, PLF = Posterolateral fusion, PLIF = Posterior lumbar interbody fusion, TLIF = Transforaminal lumbar interbody fusion, VAS = Visual Analogue Scale. ALIF= anterior lumbar interbody fusion. INTRODUCTION vertebrae over the subjacent vertebrae as Spondylolisthesis, which typically occurs the initial mechanisms of instability (2). in the lumbosacral region, is a relatively Despite regional involvement, the common entity in clinical practice and subluxation of the segmental lumbar may one of the most common causes of influence the entire biomechanical chronic low back pain (1). It is balance of the spine (3). Among the 5 characterized by the slippage of upper subtypes of spondylolisthesis, isthmic

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spondylolisthesis is named for the between October, 2012, and March, 2014 osseous discontinuity of the vertebral arch were included in this retrospective study. at the pars interarticularis (spondylolysis) The follow up period ranged from 8 to 48 (2). Frequently demonstrated at the L5/S1 months. Fourteen cases were of level, isthmic spondylolisthesis generally instrumented posterolateral fusion (PLF) is considered to be associated with the and twelve cases were of transforaminal stress or fatigue fracture of pars lumbar interbody fusion (TLIF). The interarticularis, with an approximate patients fulfilling the inclusion and incidence of 6% in adults (4,5). Surgical exclusion criteria were included in the interventions are regarded as essential for study. Inclusion criteria were (1) People symptomatic patients with isthmic of either sex who are 18–70 years of age spondylolisthesis. Various fusion (2) X-ray and magnetic resonance techniques that incorporate different imaging (MRI) proven isthmic approaches, vertebral fixation, and fusion spondylolisthesis (3) the grade of materials have been developed and used spondylolisthesis was single level and widely, such as posterolateral fusion, low grade (grade I and II) (4) Consented posterior lumbar fusion, posterior lumbar for the surgical procedures (TLIF and interbody fusion (PLIF), anterior lumbar instrumented PLF) (5) Appeared for interbody fusion, lateral lumbar interbody periodic follow-ups (6) Consented to fusion, and transforaminal lumbar include themselves in the study. The interbody fusion (TLIF) (6). exclusion criteria were (1) Patients who However, there is no consensus regarding have X-ray and MRI proven which form of fusion surgery is the best spondylolisthesis Grade III and IV (2) to treat this problem (7). Various degenerative spondylolisthesis (3) randomized controlled trials (RCTs) have Pregnant women (4) Unsound mind been performed which show no (cannot fill up the questionnaires) (5) Not significant difference in outcomes consented to the study (6) Previous back between instrumented and surgery (7) Previous fractures of the uninstrumented fusion especially in the spine. short term (8,9). However, there is an Diagnosis and decision for surgery were increasing trend toward interbody fusion. determined after a thorough medical This study has been designed to compare history and detailed physical examination. the outcomes between TLIF versus All patients received preoperative instrumented posterolateral fusion (PLF) conservative therapy comprising bed rest, in patients with isthmic spondylolisthesis. nonsteroidal anti-inflammatory drugs, and This study compares instrumented PLF physical therapy for at least 8 weeks. and TLIF in patients with isthmic The patients were worked up for spondylolisthesis and analyzes the anesthetic fitness and all comorbidities outcome with respect to functional were appropriately treated. outcome, pain, fusion rate, adequacy of OPERATIVE PROCEDURE medial facetectomy for decompression, Under general anesthesia, with the patient and complications. in prone position, a standard posterior MATERIALS AND METHODS midline incision was made. Levels were Twenty-six patients operated for ishtmic confirmed using fluoroscopy. Patient is spondylolisthesis by instrumented positioned prone recreating lumbar posterolateral or transforaminal fusion lordosis. Polyaxial pedicle screws

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inserted. This helped in achieving Plain radiographs and computed reduction. No additional reduction tomography were used to evaluate the maneuvers were used. radiologic fusion according to the Lenke In the instrumented PLF group, inferior and Bridwell classification. The OsiriX facet of the superior vertebra was DICOM Viewer was used for radiologic removed bilaterally. Superior articular measurements. Segmental lordosis facet of the inferior vertebral body (relevant to the operated levels) and the preserved and surface curetted up to total lumbar lordosis angles, bleeding bone to make a good bed for intervertebral disc heights, and foramen fusion. Bone grafting was done in the areas were measured as radiologic triangle between superior articular facet, parameters. transverse process, and pars. Segmental and total lordosis Unilateral facetectomy was performed for measurements were conducted using the the TLIF group. Discectomy was done. Cobb method. Intervertebral height was This was followed by preparation of end measured at the anterior, middle, and plates and measurement and insertion of a posterior ends of the intervertebral space TLIF cage packed with bone graft. Global in the midsagittal plane, and the average fusion was not performed. of these 3 measures was recorded. For instrumented PLF, local graft Because the facet joints were excised for harvested from the inferior articular cage insertion, the foramen areas in the process of the superior vertebra bilaterally TLIF group were measured on the along with bone taken from lamina while contralateral side of the operation. doing a foraminotomy was used. Measurements were performed in the For TLIF, bones were taken from oblique plane passing through the foraminotomy site with facetectomy and midpoint of the vertebral pedicle width. A removal of pars were utilized. No similar measurement was made in the deliberate attempt was made for reduction PLF group; however, the mean values of since the study included only low-grade the left and right foramen areas were listhesis. The reduction that was achieved recorded. during the procedure was accepted. Statistics Wounds were closed after securing Wizard 1.9.18 for MacOS was used for perfect hemostasis. statistical analysis. When samples did not Patients were mobilized as tolerated. show normal distribution, the Manne Back strengthening exercises were started Whitney U test was used for unpaired as early as second postoperative day. No data, and Wilcoxon signed-rank test was brace was used. Patients were mobilized used for paired data comparison. For data without aid as early as 4th postoperative that showed normal distribution, a t test day or as early as the they tolerated. and paired t test were used. A chi-square Measurement of the functional outcomes test was applied for analysis of the of these patients was made by the categorical data; P < 0.05 in two-tailed Oswestry disability index (ODI), and pain test was accepted as significant. scores using a Visual Analogue Scale RESULTS (VAS) were recorded preoperative, and A twenty-six cases were evaluated in our the postoperative follow-up scores were study (table 1), fourteen patients were collected at each last visit. included in the PLF group and twelve patients were in the TLIF group. The

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distributions of sex, mean age, and PLF Group presence of spondylolisthesis in the PLF The summary of results of the PLF group and TLIF groups were similar. The PLF is given in table 2. The postoperative group had significantly more L5-S1 median ODI scores were significantly fusion surgery (P = 0.024). Low back improved (56 vs. 20; P < 0.001). pain and neurogenic claudication were the Similarly, the postoperative median VAS predominant symptoms among all scores were significantly lower than the patients. preoperative scores (8 vs. 3; P < 0.001). The median length of hospital stay was 4 In these 14 patients, the median days in the PLF group and 5 days in the preoperative total lumbar lordosis angle TLIF group. The only major complication was 41 degrees, and the median was cerebrospinal fluid (CSF) fistula, postoperative lumbar lordosis angle was which developed in 1 patient in the TLIF 47 degrees (P = 0.37). The mean disc group; the development of a CSF fistula height measurements at the fused influenced the length of stay to 9 days segments increased significantly after the and was managed conservative. The mean instrumentation procedure (8.6 vs. 8.9 follow-up durations were 15.5 and 17.2 mm; P = 0.04). months for the PLF and TLIF groups, respectively. Table 1: summary of study groups Transforaminal Posterolateral P Characteristic Lumbar Interbody Fusion Value Fusion Number of patients 14 12 - Male/female ratio 6/8 5/7 0.45 Mean age (years) 46.3 46.9 0.53 L4-5 (4) L4-5 (3) 0.31 Fusion segments L5-S1 (10) L5-S1 (9) 0.04 Operation time 138 185 0.02 (minutes) Blood loss (mL) 210 390 0.20 Length of stay 4 6 0.07 (days) Number of cerebrospinal 0 1 0.38 fluid fistulas Follow-up months 15.5 17.2 0.24

A B C Figure 1: (a) CT lumbar spine sagittal view showing L4-5 spondylolisthesis; (b) X-ray lumbosacral spine lateral view showing instrumented posterolateral fusion; (c) X-ray lumbosacral spine A-P.

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TLIF Group The results of the TLIF group are summarized in table 2. The preoperative and postoperative median ODI scores were 52 and 17, respectively (P < 0.001). Pain was ameliorated in the postoperative period, as reflected by the median VAS scores (8 vs. 4; P < 0.001). the median preoperative total lumbar lordosis angle was 39 degrees, and the median postoperative lumbar lordosis angle was 48 degrees (P = 0.21). The postoperative mean disc height measurements were significantly higher than the preoperative values (7.9 vs. 8.4 mm; P < 0.001).

A B Figure 2: (a) X-ray lumbosacral spine lateral view showing L5-S1 spondylolisthesis; (b) followup X-ray lumbar spine lateral view showing transforaminal lumbar interbody fusion. Intergroup Analysis vs. 0.83 cm2 [P = 1.00] and 8.6 vs. 7.9 The comparison of the results of the 2 mm [P = 1.00]). Similarly, in all fused study groups is given in Table 2. No segments considered, the type of difference was noted in the preoperative operation was not significant for either ODI and VAS scores between the 2 the postoperative foramen areas (1.24 vs. groups (56 vs. 54 [P = 0.25] and 8 vs. 8 1.32 cm2; P = 1.000) or postoperative [P = 0.26]). Similarly, 2 different fusion disc heights (8.9 vs. 8.4 mm; P = 1.000). procedures did not result in a significant The percentage change in the foramen difference in the postoperative ODI and areas from the preoperative values was VAS scores (P = 0.08 and P = 0.74, significant and in favor of the TLIF respectively). The operation duration was procedure (30% vs. 50%; P = 0.03). longer in the TLIF group (138 vs. 185 Although the median percentage change minutes; P = 0.02), and the TLIF in disc height was greater in the TLIF procedure resulted in more blood loss group, this difference was not significant (210 vs. 390 mL; P = 0.2). As for the (5% vs. 14%; P = 0.42). radiologic measurements, the difference Table 2: preoperative and postoperative value of PLF and TLIF groups. was not significant in the preoperative or Category PLF TLIF P Value ODI postoperative total lordosis angles Preoperative 56 52 0.25 between the groups. Considering all postoperative 20 17 0.08 VAS segments, the preoperative foramen areas Preoperative 8 8 0.26 postoperative 3 4 0.74 and disc heights did not differ Total lordosis angle

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Disc height (mm) Preoperative 8.6 7.9 ˃ 0.99 vertebrae. The absence of motion in Postoperative 8.9 8.4 ˃ 0.99 flexion extension views, as sole criteria Change in disc height +5% +7% 0.42 foramen area (cm2) for assessing fusion postoperatively have Preoperative 0.92 0.83 ˃ 0.99 Postoperative 1.24 1.32 ˃ 0.99 been previously published by Brodsky et Change in foramen area + 30% + 50% 0.03 Radiologic fusion rate 91% 94% 0.72 al., (15) compared the findings of lumbar DISCUSSION flexion extension radiography to surgical Many studies have established that TLIF exploration in a series of 175 patients is a better procedure than PLIF and ALIF who underwent reoperation for various in terms of outcomes and complications indications following instrumented and (10,11) because it is currently believed non-instrumented lumbar fusion. They that interbody fusion is the gold standard found a 62% correlation between in the treatment of spondylolisthesis. preoperative flexion extension Circumferential fusion compared to radiography and intraoperative findings at instrumented PLF provides conflicting exploration (specificity 37%, sensitivity data. Fritzell et al. (12) demonstrated no 96%, positive predictive value 70%, and significant difference between negative predictive value 86%). Their circumferential fusion and PLF. study provides Class II medical evidence However, Videbaek et al. (13) that the absence of motion on flexion demonstrated significant improvement in extension X-ray films is highly suggestive patients who underwent circumferential of a solid fusion. fusion as opposed to PLF. Fujimori et al. The PLF and TLIF procedures in a (14) investigated the benefits of TLIF somewhat heterogeneous group of compared with PLF in a subset of patients patients (i.e., spondylolisthesis, with spondylolisthesis. When 1- or 2- degenerative disc disease, spinal stenosis, level TLIF or PLF was performed, the and failed back surgery) were TLIF procedure resulted in better investigated in a randomized controlled restoration of disc height; however, trial by Hoy et al. (16) The 2-year year health-related outcomes were similar follow-up results indicated that both the between the 2 groups. When evaluated procedures effectively ameliorated separately, each group showed symptoms in degenerative lumbar spine; improvement in the postoperative disc however, no significant difference in the heights. Our results are similar to their radiologic fusion rate, functional study and this might be attributed to the outcomes, and global satisfaction with the result of appropriate selection of the TLIF intervention were noted. Similarly, our cage. clinical outcome measures (i.e., the VAS The aim of spinal fusion surgery is to and ODI scores) did not show any eliminate motion between the two significant difference between the 2 vertebrae. When the vertebrae are fused at groups. two different points, it eliminates motion An issue that requires clarification is the in all three planes. During surgery, we rate of postoperative radiologic fusion. have freshened the transverse process, Together with the current study, almost pars, and superior facet upto bleeding all studies that compared PLF with TLIF bone. Subsequently, graft was placed demonstrated equivalent rates of fusion; between bleeding bones with aim to however, Audat et al. (17) compared achieve union. By this method, we have PLF, PLIF, and TLIF for degenerative ensured reliable union between the disc disease and found that no significant

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difference existed between the three spondylolisthesis. J Neurosurg Spine., groups in terms of clinical outcomes and 13: 288-293. complications. However, there was a 3. Faldini C, Di Martino A, Perna F, small increase in the radiological fusion Martikos K, Greggi T, Giannini S rates in the TLIF group. Interestingly, (2014): Changes in spino-pelvic they stated that their findings were alignment after surgical treatment of consistent with the study published by high-grade isthmic spondylolisthesis Hoy et al. (16) reported 84% versus 94% by a posterior approach: a report of 41 fusion rates for PLF and TLIF, cases. Eur Spine J., 23(suppl. 6): 714- respectively, for which the difference was 719. not significant (P = 0.31). Nevertheless, 4. Gong K, Wang Z, Luo Z (2010): the concept of solid spinal fusion is a Reduction and transforaminal lumbar continuing debate, which should be interbody fusion with posterior resolved with the validation of new fixation versus transsacral cage fusion evaluation methods. in situ with posterior fixation in the instrumented PLF works as an equally treatment of Grade 2 adult isthmic good option with similar outcomes, spondylolisthesis in the lumbosacral similar patient satisfaction scores, and spine. J Neurosurg Spine., 13: 394- complications. However, the cost of 400. adding an interbody cage is significant, 5. Pan J, Li L, Qian L, Zhou W, Tan J, especially in a low-resource country. Zou L (2011): Spontaneous slip limitation of the present study is due to reduction of low-grade isthmic the relatively low number patients in each spondylolisthesis following group; indeed, a larger sample size may circumferential release via bilateral be required for more reliable results and minimally invasive transforaminal subgroup analyses. lumbar interbody fusion: technical CONCLUSION note and short-term outcome. Spine PLF and TLIF added to decompression (Phila Pa 1976), 36: 283-289. surgery were equally effective in 6. Fogel GR, Turner AW, Dooley ZA, ameliorating symptoms in the treatment Cornwall GB (2014): Biomechanical of low Grade isthmic spondylolisthesis. stability of lateral interbody implants Conflicts of interest and supplemental fixation in a There are no conflicts of interest cadaveric degenerative REFERRANCES spondylolisthesis model. Spine (Phila 1. Butt MF, Dhar SA, Hakeem I, Farooq Pa 1976), 39: E1138-E1146. M, Halwai MA, Mir MR (2008): In 7. Gibson JN, Waddell G. Surgery for situ instrumented posterolateral fusion degenerative lumbar spondylosis without decompression in (2005): Updated Cochrane Review. symptomatic low-grade isthmic Spine (Phila Pa 1976), 30: 2312-20. spondylolisthesis in adults. Int 8. Fritzell P, Hägg O, Wessberg P, Orthop., 32: 663-669. Nordwall A (2002): Swedish Lumbar 2. Lastfogel JF, Altstadt TJ, Rodgers RB, Spine Study Group. Chronic low back Horn EM (2010): Sacral fractures pain and fusion: A comparison of following stand-alone L5-S1 anterior three surgical techniques: A lumbar interbody fusion for isthmic prospective multicenter randomized study from the Swedish lumbar spine

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study group. Spine (Phila Pa 1976), Degenerative Spondylolisthesis? 27: 1131-41. Global Spine J., 5: 102-109. 9. Thomsen K, Christensen FB, Eiskjaer 15. Brodsky AE, Kovalsky ES, Khalil SP, Hansen ES, Fruensgaard S, MA (1991): Correlation of radiologic Bünger CE (1997): The effect of assessment of lumbar spine fusions pedicle screw instrumentation on with surgical exploration. Spine (Phila functional outcome and fusion rates in Pa 1976), 16 (6): S261-S265. posterolateral lumbar spinal fusion: A 16. Hoy K, Bunger C, Niederman B, prospective, randomized clinical Helmig P, Hansen ES, Li H (2013): study. Spine (Phila Pa 1976), 22: Transforaminal lumbar interbody 2813-2822. fusion (TLIF) versus posterolateral 10. Brantigan JW, Neidre A, Toohey JS instrumented fusion (PLF) in (2004): The Lumbar I/F Cage for degenerative lumbar disorders: a posterior lumbar interbody fusion randomized clinical trial with 2-year with the variable screw placement follow-up. Eur Spine J., 22: 2022- system: 10-year results of a Food and 2029. Drug Administration clinical trial. 17. Audat Z, Moutasem O, Yousef K, Spine J., 4: 681-688. Mohammad B (2012): Comparison of 11. Zdeblick TA and Phillips FM (2003): clinical and radiological results of Interbody cage devices. Spine (Phila posterolateral fusion, posterior lumbar Pa 1976), 28 (15): S2-7. interbody fusion and transforaminal 12. Fritzell P, Hägg O, Wessberg P, lumbar interbody fusion techniques in Nordwall A (2002): Swedish Lumbar the treatment of degenerative lumbar Spine Study Group. Chronic low back spine. Singapore Med J, 53: 183-187. pain and fusion: A comparison of three surgical techniques: A prospective multicenter randomized study from the Swedish lumbar spine study group. Spine (Phila Pa 1976), 27: 1131-1141. 13. Videbaek TS, Christensen FB, Soegaard R, Hansen ES, Høy K, Helmig P, Niedermann B, Eiskjoer SP, Bünger CE (2006): Circumferential fusion improves outcome in comparison with instrumented posterolateral fusion: long-term results of a randomized clinical trial Spine (Phila Pa 1976), 31(25): 2875-2880. 14. Fujimori T, Le H, Schairer WW, Berven SH, Qamirani E, Hu SS (2015): Does Transforaminal Lumbar Interbody Fusion Have advantages over Posterolateral Lumbar Fusion for

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