ORIGINAL ARTICLE |
https://doi.org/10.5005/jojs-10079-1161 |
Clinical and Radiological Outcome of Transforaminal Lumbar Interbody Fusion with Polyether Ether Ketone Cage in Patients with Lumbar Spondylolisthesis
1–6Department of Orthopedics, SRM Institute of Science and Technology, Potheri, Tamil Nadu, India
Corresponding Author: Rishab Chandraprakash, Department of Orthopedics, SRM Institute of Science and Technology, Potheri, Tamil Nadu, India, Phone: +91 9994111656, e-mail: rishabc@srmist.edu.in
Received: 14 February 2024; Accepted: 17 April 2024; Published on: 14 June 2024
ABSTRACT
Aim: Lumbar spondylolisthesis has been a major cause of disability in the general population, mostly in the later part of the productive age-group. Various modes of treatment and surgeries have come up to tackle this morbidity, but with differing results. This study aims to assess clinical and radiological outcomes in patients who underwent transforaminal lumbar interbody fusion (TLIF) with a polyether ether ketone (PEEK) cage for lumbar spondylolisthesis.
Materials and methods: A total of 38 patients with varying grades of lumbar spondylolisthesis, among which, 11 males and 27 females were included in this study. All underwent TLIF with PEEK cage surgery. Their preoperative and postoperative pain score, functional scores, and radiological parameters were compared. All patients were followed up to 12 months.
Results: The mean preoperative visual analog scale (VAS) started from 8.53 and came to 2.79, postoperatively. Around 68.4% of patients showed minimal disability. Around 60.5% of patients showed excellent outcomes. Around 73.7% of patients showed fusion at 12 months. Near-normal radiological parameters were achieved in all the patients. Five patients showed complications.
Conclusion: Overall patient satisfaction was observed in this study, and good radiological outcomes were achieved. The PEEK cage augments the mechanical support provided by TLIF.
Clinical significance: The modulus of elasticity of PEEK (3.6 GPa) makes it more closely aligned with cancellous bone (1–20 GPa) compared to traditionally used titanium cages (120 GPa). This alignment contributes to lower rates of bone dehiscence and improved patient outcomes.
How to cite this article: Chandraprakash R, Kalirajan R, Bhalodiya M, et al. Clinical and Radiological Outcome of Transforaminal Lumbar Interbody Fusion with Polyether Ether Ketone Cage in Patients with Lumbar Spondylolisthesis. J Orth Joint Surg 2024;6(2):130–135.
Source of support: Nil
Conflict of interest: None
Keywords: Polyether ether ketone cage, Spondylolisthesis, Transforaminal lumbar interbody fusion.
INTRODUCTION
Spondylolisthesis is one of the major causes of low-back aches, mostly in the later part of middle (productive) age. Lumbar instability is not seen in all cases of spondylolisthesis. This segmental instability is associated with chronic low-back pain with or without radiculopathy.
Since the evolution of modern orthopedic instrumentation, many surgical techniques have been adopted for lumbar instability to give such patients a pain-free life and early return to their routine. Among these, transforaminal lumbar interbody fusion (TLIF) is well-documented and accepted in the literature as it provides circumferential stabilization in a single incision.1,6 TLIF is also regarded safer than other surgeries on the spine due to its approach.
Intervertebral cages of various materials also have been introduced to augment the stability. Polyether ether ketone (PEEK) cage with its modulus of elasticity, equivalent to cancellous bone, has been used as an alternative to titanium.7,8 However, not much has been documented regarding TLIF surgeries with PEEK cages. We aim to study the functional outcomes after TLIF with PEEK cage fixation in patients operated on for lumbar segmental spondylolisthesis and correlate radiologically by assessing fusion, implant position, and complications.
MATERIALS AND METHODS
A total of 38 patients (11 males and 27 females) were included in this study. The age-group ranged between 30 and 67 years (mean age—49.29 years). Inclusion criteria were either isthmic or degenerative spondylolisthesis after failed conservative management for >6 months. Exclusion criteria were <20 and >70 years of age, instability of more than two levels, dysplastic or pathologic type of spondylolisthesis, previous spine surgery, and moribund patients. The procedure was explained to the patients, and proper consent was obtained. Preoperative visual analog scale (VAS) and functional status using the Oswestry Disability Index (ODI) short form-12 (SF-12) questionnaire were documented, and thorough physical and neurological examination was done. Lumbosacral (LS) spine stress (flexion-extension) view X-rays (Fig. 1 and Table 1) were done to assess instability and pelvic parameters (lumbar lordosis, slip grade, slip angle, disk height, foraminal height, sagittal vertical axis, sacral slope, pelvic tilt, and pelvic incidence) and were documented as shown in Table 1. Magnetic resonance imaging (MRI) of the LS spine (Fig. 2) was done as a part of preoperative planning and to assess canal stenosis.
| Spinal parameters (preoperative) | Values/findings |
|---|---|
| Listhesis | Grade II |
| Slip angle | −15° |
| Sacral slope | 46° |
| Pelvic tilt | 18° |
| Pelvic incidence | 64° |
| Disk height | 6.7 mm |
| Foraminal height | 7.9 mm |
Fig. 1: Grade II listhesis of L4 over L5
Fig. 2: Magnetic resonance imaging of the LS spine for preoperative planning showing canal stenosis and bilateral nerve root compression
Surgical Technique
After a proper preanesthesia workup and prophylactic antibiotic cover, general anesthesia was given. Patients were put in a prone position on the Relton–Hall (four-poster) frame. Through the standard midline approach, posterior elements were exposed. Polyaxial, nonreduction pedicle screws (5.5/6.5 mm) were inserted freehand and checked under the image intensifier. Rod (contoured prior) was applied on the less symptomatic side, and laminectomy was done at an appropriate level. Disk space was prepared, and an appropriate size of PEEK cage was used (Figs 3 and 4). Another rod was placed on the other side as well. Contoured rods help to maintain lumbar lordosis.
Fig. 3: C-arm image showing a lateral view of the spine segment with pedicle screws and PEEK cage in position
Fig. 4: C-arm image showing an anteroposterior view of the spine segment with pedicle screws and PEEK cage in position
Postoperative Care
Patients were mobilized with an LS corset from 2nd postoperative day after drain removal with walker support with restriction of forward bending.
Neutral LS radiographs were taken in the immediate postoperative period (Fig. 5). Functional status was assessed using VAS, ODI, Macnab’s criteria, SF-12, and radiological parameters were documented at 6 months postoperative follow-up (Fig. 6). Fusion was assessed at the final follow-up at 12 months using Brantigan–Steffee criteria9,10 (Fig. 7) and the spine parameters in the 1-year postoperative X-ray of LS spine were documented (Table 2).
| Spinal parameters (postoperative) | Values/findings |
|---|---|
| Listhesis | Reduced |
| Slip angle | 11° |
| Sacral slope | 45° |
| Pelvic tilt | 10° |
| Pelvic incidence | 55° |
| Disk height | 11.1 mm |
| Foraminal height | 13.6 mm |
Fig. 5: Immediate postoperative radiograph
Fig. 6: 6th-month postoperative radiograph
Fig. 7: 1-year postoperative radiograph
Statistical Analysis
All the data were analyzed using Statistical Package for the Social Sciences 13.0 on Windows. Preoperative and postoperative VAS, ODI, and SF-12 were compared using a Student’s t-test. A p-value of <0.05 was not found to be significant.
RESULTS
Among the 38 patients, 18 patients had grade II listhesis, and two patients had grade III listhesis. There were 11 male and 27 female patients. Their mean age was 49.29 years (range 30–67 years). The mean duration of surgery was 137 minutes, and the mean blood loss was 280 mL. Postoperatively, about 28 patients (73.7%) showed grade 0, nine patients (23.7%) showed grade I listhesis, and only one (2.6%) patient showed no listhesis reduction. Patients with good listhesis reduction showed better outcomes in our study, which is discussed later. Cage sizes varied from 7 to 11 mm.
The mean preoperative VAS was 8.53, which improved to 2.79 in the 6th month postoperative period. About 26 patients (68.4%) showed minimal disability, and 12 patients showed (31.6%) moderate disability at 6 months of postoperative period as per ODI. Macnab’s criteria showed excellent outcomes in 23 patients (60.5%), good in 12 patients (31.6%), and fair outcomes in three patients (7.9%). ODI and VAS scores showed improvement in all the patients. Physical scoring by SF-12 also showed improved from 25.78 to 48.25, and mental scoring improved from 25.28 to 52.87.
All the patients showed near-normal physiological pelvic incidence (sacral slope + pelvic tilt) in the postoperative radiographs. The preoperative sacral slope and pelvic tilt were 36.02 and 14.64, respectively. The mean 1-year postoperative sacral slope and pelvic tilt were 34.74 and 12.13, respectively. Preoperative mean pelvic incidence was 50.66°, and 1-year postoperatively pelvic incidence was 46.87° attributable to near normal physiological range. Preoperative mean disk height and foraminal height were 7.1 and 13.1, respectively, and mean 1-year postoperative disk height and foraminal height were 11.2 and 17.7, respectively. All the above findings have been summarized below (Table 3). Fusion was seen in 28 patients (73.7%) at the final (1 year) follow-up. Patients who showed excellent and good outcomes showed fusion at the involved level and restoration of disk height and foraminal height at the affected level.
| Variables | Mean |
|---|---|
| Age (years) | 49.29 |
| Duration (months) | 22.26 |
| Preoperative VAS | 8.53 |
| Preoperative ODI | 56.00 |
| Preoperative SF-12 physical component summary (PCS) | 25.78 |
| Preoperative SF-12 mental component summary (MCS) | 25.18 |
| Preoperative pelvic incidence | 50.66 |
| Duration of surgery (hours) | 2.63 |
| Blood loss (mL) | 279.7 |
| Postoperative VAS | 2.79 |
| Postoperative ODI | 20.58 |
| Postoperative SF-12 PCS | 48.25 |
| Postoperative SF-12 MCS | 52.87 |
| Postoperative pelvic incidence (degree) | 46.87 |
Intraoperative complications like dural tears occurred in two patients (5.3%), and the cage broke while being placed in three patients (7.9%). Postoperative complications like wound site infection occurred in one patient (2.6%), and cage migration was noted in two patients (5.3%). None of the patients had neurological deficits.
DISCUSSION
Lumbar segmental instability has become one of the major reasons for disability in the general population, especially in their productive age. This has led to a significant increase in morbidity due to an increase in loss of work days and increased health expenditure. In this mechanical era, the focus is on selecting patients for surgery as definitive management and giving pain-free lives and early return to their normal routine.
Instability can develop in a spondylotic spine, leading to degenerative spondylolisthesis and remodeling of the articular process at the level of the involved segment. This is assumed to be due to degenerative disk disease, in which the intervertebral disk becomes dehydrated and annulus fibrosus loses tensile strength. The dehydrated disk reduces in height, leading to posterior face joint subluxation and intersegmental instability.11,12 The other etiological types of spondylolisthesis are dysplastic, isthmic, pathological, and traumatic. The presence of intact pars interarticularis differentiates from the isthmic type.13
Spinal instability refers to abnormal slippage of one vertebra over the adjacent vertebra. White and Panjabi have defined instability as “the loss of the ability of the spine under physiological loads to maintain relationships between vertebrae in such a way that there is neither damage nor subsequent irritation to the spinal cord or nerve roots, in addition, there is no development of incapacitating deformity or pain due to structural changes.”14
To overcome pain due to spinal instability, solid spinal fusion is necessary, as stated by Weinstein et al.15 The earliest known procedures of pars repair by Bucks or Wiltse modification of posterolateral fusion with bone grafts had prolonged healing time and poor stability till the spine fused. Hence, Cloward introduced a solid interbody, but it showed a significant rate of complications and difficulty in disk preparation. TLIF, a modification of PLIF, was introduced by Harms and Bollinger. It gives easier access to posterior structures and good circumferential stability in the single incision.16
Interbody cages were introduced to augment segmental instability in the form of bone grafts and then metallic (titanium) cages for PLIF or TLIF. Due to metal-related complications (like subsidence/migration),17,18 PEEK cages were used. Chen et al.,18 in their study regarding interbody cages, found cage subsidence as a complication in about 34.5% of patients in the titanium group, whereas 5.4% of patients in the PEEK cage group in their 7 years of follow-up. Seaman et al.17 meta-analyses found fewer complication rates in the PEEK group compared to the titanium group. This can be attributed to Young’s modulus of elasticity of PEEK, which matches the cancellous bone.
The preoperative VAS mentioned here is after failed conservative management, and this is comparable with a study by Möller and Hedlund.19 The VAS and ODI of this study are comparable to the study by Hackenberg et al.,20 where the 6 months postoperative ODI and VAS were 20.3 and 3.9, respectively and Boissiere et al.21 where the final ODI and VAS were 23.6 and 3.4, respectively.
All patients showed significant improvement in their radiological parameters. Their preoperative pelvic incidence was 50.66, and their postoperative was 46.87, which was in the physiologically normal range, which is comparable with a study by Uysal et al., who stated that “pelvic tilt is dependent on pelvic incidence. The pelvic tilt could be as high as pelvic incidence, as the sacral slope could be as low as zero.”22 The disk height and foraminal height were restored at the affected level in most of the patients, which was comparable with the study done by Yan et al.23 and Jagannathan et al.2 Kwon et al.24 in their study achieved good disk height initially, but in their long follow-up, they found disk height was reduced in the final follow-up compared to the immediate postoperative radiographs and the same was observed in our study at the final follow-up.
Uysal et al.22 had achieved listhesis reduction in all patients. Their preoperative mean grade was 1.11, and their postoperative mean grade was 0.11, which is comparable to this study, where the mean preoperative and postoperative grades were 1.57 and 0.28, respectively. In a study by Hagenmaier et al., listhesis reduction and fusion did not influence the clinical outcome,25 whereas in our study, when the collected results were paired up, ODI score and VAS were even better in patients with good listhesis reduction and the same was observed in patients with fusion.
A study by Soleman et al.26 in which a Loop PEEK cage was used, showed cage dislocation in two patients and nerve deficit in three patients among 41 patients, but we did not encounter such complications in our study, which may be because we used a bullet PEEK cage. In our study, two patients showed cage migration after 6 months of follow-up. Both patients did not have any worsening symptoms or neurological deficits. They were managed, conservatively, and advised for further prolonged follow-up. Intraoperatively, a dural tear was seen in two patients, and they were sutured.
Fusion was seen in 73.7% of the patients at the end of 1 year, whereas in a study by Hackenberg et al.,20 fusion was seen in 89% of patients at the end of 3 years using the same criteria as used in our study. VAS improved significantly in patients who showed fusion, and this is comparable to the study done by Poh et al.,27 Whereas Hackenberg et al.20 have concluded that the functional outcomes did not seem to corelate with the fusion status. The limitations of our study are the shorter duration of follow-up and the lack of a control group.
CONCLUSION
This study shows good patient satisfaction and outcomes. Radiological outcomes are also good with the fusion seen in the majority of the patients. The complication rates are relatively low. Functional outcome was much better in the patients with fusion and good listhesis reduction. However, a proper randomized controlled trial is required in this gray region.
Clinical Significance
The modulus of elasticity of PEEK (3.6 GPa) as a material for the implant is closer to cancellous bone (1–20 GPa) than conventionally used titanium (120 GPa) cages, which in turn results in lesser rates of bone dehiscence and better patient outcomes.
ORCID
Rishab Chandraprakash https://orcid.org/0009-0008-1712-9624
Rajavel Kalirajan https://orcid.org/0009-0000-3675-2229
Milap Bhalodiya https://orcid.org/0009-0008-2880-1420
Vijayanand Balasubramanian https://orcid.org/0000-0003-3638-1127
Gowthaman Nambiraj https://orcid.org/0009-0002-7492-4946
Mohan Mahendramani https://orcid.org/0009-0002-0241-3389
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