Surgical Results of Posterior Lumbar Interbody Fusion with Transpedicular Fixation in Management of Spondylolisthesis

Objective: To evaluate the surgical results of posterior lumber interbody fusion with transpedicular fixation with rod screw system in management of spondylolisthesis. Study Design: Retrospective study reviewed all patient treated by lumber interbody fusion with transpedicular fixation with rod screw system. Patients and Methods: They were 40 patients operated for lumber and lumbosacral spondylolisthesis from Feb 2014 to April 2017 in Al-Azhar university hospital. These patients followed postoperatively clini-cally for improved neural function and for fusion stability and hardware fixation by radiological investigation. Data about pain intensity (by Visual Analogue Scale) was collected pre- and postoperatively; and outcome was assessed by Oswetry disability index (ODI). Outcome was graded as excellent, good, fair, or poor. Pre- and Post-operative data were statistically compared. Results: The mean age was 45 years (range between 30 - 60 years) with female sex predominance (male:female = 1:3). They had lytic (n = 30) or degenerative (n = 10) spondylolisthesis; and all underwent PLIF (posterior lumbar interbody fusion). In lytic group, the level was L4/L5 in 19 patients and L5/S1 in 11 patients, while in degenerative group the level was L4/L5 in 4 patients, L5/S1 in 3 patients, L2/L3 in 2 and L3/L4 in one patient. The spondylolisthesis safe and effective surgical intervention in both lytic and degenerative types.


Introduction
Spondylolisthesis is defined as the "subluxation of a vertebral body over another in the sagittal plane". It is a frequent mechanism responsible for intervertebral instability [1] [2]. In addition, spondylolisthesis could be attributed to Pars interarticularis defects, previous surgical intervention or trauma leading to laxity of ligaments. In general populations, spondylolisthesis affects about 5.0% with no specific age predilection [3]. Indications of surgical treatment of spondylolisthesis included claudication of neurogenic origin, severe radicular pain, intractable low back pain, instability, neurological manifestations, failure of medical treatment, progressive course, grades III and IV of listhesis and spondyloptosis [2] [4] [5].
In addition, spondylolisthesis could be due to a spondylolysis. Marchetti and Bartolozzi [6] classification investigates two broad etiological causes (developmental or acquired) ( Table 1). The classification is relevant to many disease criteria (e.g., natural history, progression risk, and had treatment implications). On the other side, the Meyerding's classification [7] aims to assess severity of disease using lateral radiographs to judge the potential anterior displacement of the cephalad vertebral body over its distal counterpart.
As previously state, in general population, the incidence of disease is around 5%. However, high prevalence (up to 12%), was reported in adolescents who had Scheurman's disease, athletes (weight lifters, football players, and gymnastics), indicating that, the disease could be due to mechanical factors [8].
Congenital predisposition to spondylolysis was proposed in many studies, with prevalence rate of 27% -69% in families of affected members [9]. In addition, the condition was found to be associated with high incidence of spina bifida (28% -42%), congenital sacrum and superior sacral facet deficiencies [10].
In addition, it is thought that, structural failure in a dysplastic spine could be due to repetitive traumatic stress on the pars inter-articularis [11]. The defects in pars are usually acquired and rarely seen in newborn [8]. L4 and L5 represented the keystones of lumbo-sacral spine as they provide stability by supporting physiological loads and stopping unnecessary motion. Both are the most commonly affected vertebrae. The course of the disease is usually benign as reported in long term follow up longitudinal studies [12]. However, disease progression with neurological affection and low back pain were reported in association with the low sacral index, degenerative disc of Meyerding grade [13].
In patients with isthmic spondylolisthesis, the incidence of spondylolysis may be elevated up to 70% [11]. The progression to spondylolisthesis from spondylolysis is as low as 4% -5% [7]. The risk factors responsible for increased likelihood of further slippage include younger age, female sex, spina bifida, wedging vertebrae, rounded anterior sacral dome and hyperlordosis [14].

Aim of the Work
The aim of this study is to assess the results of surgical intervention after surgery  Digital X-ray, CT and MRI films of the spine were acquired to measure instability and discover any intraspinal neurological deficits.

Patients and Methods
Visual analogue score (VAS) [15] for pain and the Oswestry Disability Index (ODI) [16] were implemented for every patient at postoperative 3, 6 and 12 months. Fusion status was radiologically assessed (X-ray, CT or MRI). CT was done when radiological fusion was doubted or proposed to be not achieved.
Outcome was graded by Macnab criteria [17] as excellent (full recovery of symptoms and no limitation of work-related or daily activities), good (residual or occasional symptoms but the subject is able to continue normal daily activities), fair (partial recovery of symptoms, difficulty or inability to work), or poor (no recovery or worsening of symptoms).

Results
The study included 40 patient (30 female and 10 male) diagnosed as spondylolisthesis with failed conservative management. Thus, surgical management was indicated and carried out. All the patients were evaluated by clinical and radiological examinations in pre and postoperative periods (Figures 2-8).
A. Taha, M. Youssef Open Journal of Modern Neurosurgery       The youngest patient included in this series was 30 years, the oldest patient was 60 years with mean age 45 ± 14.06 and females were commonly involved (male:female = 1:3).
All patients complained from low back pain (lumbar pain), reduced range of motion of the lumber area, aggravation of symptoms with prolonged standing.
The symptom duration ranged from 1 -3 years (mean 1.5 years). The most common affected level was L4 -L5, as it was discovered among 19 patients. Instability and its related hypermobility related to the affected level were discovered intraoperatively. The operative time ranged between 45 -150 minutes (mean value was 100 minutes) and the mean duration of hospital stay was 8.5 days.
The follow up duration was at least 12 months. Revision surgery was reported and 2.79 (between 0 -5), respectively; with statically significant reduction. Five subjects with no resolve of their complaints after the surgery were still heavy workers.
Good outcome was significantly associated with younger age group (31 -40 years). In addition, good outcome was linked to male gender. Furthermore, good outcome was strongly associated with lower grade of slip, as showed in Table 2.

Discussion
Surgical management of spondylolisthesis (PLIF) permits decompression of nerves, stabilization of deranged motion segment, restoration of the height of the disc, and restoration of translated sagittal plane and rotational alignment [15].
Age in the present study is comparable to previous studies, reported that, the age ranged from 29.8 to 53.4 years in patients managed for isthmic spondylolisthesis [16] [17]. In another study, the mean age was as that of the present work (45 years) in patients who underwent PLF [18].
Also, the duration of symptoms ranged from 8 to 60 months, with a mean duration of 38.4 months in one study [16], which comparable to the present work.
In our series, level L4-5 involvement was reported in 19 patients, L5 -S1 in 11 subjects and 25 patients had grade 1 slip, while grade II slip was discovered in 11 patients. Kim et al. reported that 50% of the affected levels were L4-5, and this ratio was similar to that found in the present work.
Posterolateral fusion has been one of the standards surgical interventions for instability of lumbar spine with use of spinal instrumentation. For assessment of  [20]. It is recommended that a decrease in neurological complications may be achieved by the use of intraoperative neuromonitoring especially in surgeries like for spondylolisthesis [21]. In the present work, no implant failure was reported and no mortality was registered. All patients with post-surgical morbidities responded to conservative management.
Some researchers reported that, the clinical outcome for PLIF is not better than other fusion interventions [22]. However, in PLIF, the wider retraction of the nerve root and thecal sac was obviously disadvantageous because it stimulated leg pain. But, an ODI of 89% with good or excellent results was reported in the PLIF, and 86% in PLF. The difference was not statistically significant [23] [24].

Conclusion
In