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ORIGINAL ARTICLE
Year : 2022 | Volume
: 55
| Issue : 5 | Page : 163-170
Preliminary report on value of Wallis interspinous device for back pain following microdiscectomy: A prospective cohort study
Cheng-Ta Hsieh1, Yu-Hao Chen2, Kuo-Chang Huang3, Pi-Chan Ko3, Jui-Ming Sun4
1 Division of Neurosurgery, Department of Surgery, Sijhih Cathay General Hospital, New Taipei City; School of Medicine, National Tsing Hua University, Hsinchu; Department of Medicine, School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
2 Section of Neurosurgery, Department of Surgery, Ditmanson Medical Foundation, Chia-Yi Christian Hospital, Chia-Yi City; Chung-Jen Junior College of Nursing, Health Sciences and Management, Chia-Yi County, Taiwan
3 Section of Neurosurgery, Department of Surgery, Ditmanson Medical Foundation, Chia-Yi Christian Hospital, Chia-Yi City, Taiwan
4 Section of Neurosurgery, Department of Surgery, Ditmanson Medical Foundation, Chia-Yi Christian Hospital, Chia-Yi City; Department of Biotechnology, Asia University, Taichung City, Taiwan
Correspondence Address:
Jui-Ming Sun
Department of Surgery, Section of Neurosurgery, Ditmanson Medical Foundation, Chia-Yi Christian Hospital, No. 539, Zhongxiao Road, East District, Chia-Yi City 600
Taiwan
Source of Support: None, Conflict of Interest: None
DOI: 10.4103/fjs.fjs_98_22
Background: Postoperative back pain is a common complaint following microdiscectomy. The Wallis implant, an interspinous process device, is effective against mechanical low back pain due to spinal instability following discectomy. The present study aims to evaluate the value of the Wallis implant with microdiscectomy compared with microdiscectomy alone.
Materials and Methods: Twenty patients were enrolled between June 2016 and August 2019. All patients received complete radiography and completed a questionnaire before and 1, 3, 6, and 12 months after surgery. Clinical outcomes were evaluated using the visual analogue scale (VAS) for back pain and Oswestry Disability Index (ODI). Radiologic outcomes were posterior disc height, foraminal height, foraminal area, segmental angle, and range of motion in flexion and extension views.
Results: The Wallis group contained six male and three female patients (mean age 45.7 ± 13.3 years, range 20–61 years), and the control group comprised three male and eight female patients (mean age 47.6 ± 7.5 years, range 34–58 years). All patients had clinical improvements in VAS score and ODI after microdiscectomy alone or with the placement of the Wallis implant. The Wallis group had more favorable mean VAS score and ODI at the 1-, 3-, 6-, and 12-month follow-ups compared with the control group. However, the mean VAS score of the Wallis group was significantly lower than that of the control group only at postoperative month 6 (P = 0.012), whereas the mean ODI in the Wallis group was significantly better than that of the control group only at postoperative months 1 (P = 0.036) and 12 (P = 0.042). Although greater posterior disc height, foraminal height, and foraminal area were observed in the Wallis group, especially in the extension view, the difference in comparison with the control group was not significant.
Conclusion: Our limited results indicate that the Wallis implant may reduce postoperative low back pain (VAS score) and improve quality of life (ODI) following microdiscectomy. However, the difference between microdiscectomy alone and microdiscectomy with the Wallis implant was not consistently significant throughout the 12 months of follow-up, regardless of the maintenance of radiologic outcomes.
Keywords: Interspinous process device, microdiscectomy, postoperative back pain, primary herniated intervertebral disc, Wallis implant
Lumbar radiculopathy is a common disease with symptoms associated with disc herniation occurring during displacement of the nuclear pulposus through the annulus fibrous. The prevalence of symptomatic lumbar radiculopathy is estimated to be between 3% and 5%, with the condition most frequently occurring among those 30–50 years of age.[1] Lumbar microdiscectomy is a common neurosurgical procedure used to manage symptoms related to a herniated intervertebral disc (HIVD) and allows a quick recovery, a short hospital stay, and decreased morbidity.[2],[3],[4] Recurrent disc herniation with or without radicular pain remains the main sequela following lumbar microdiscectomy despite other well-documented complications that include iatrogenic durotomy, nerve root injury, hematoma, and infection.[2],[3],[5],[6] Aggressive discectomy is an alternative procedure to reduce the incidence of reherniation, but this approach may be associated with greater postoperative back pain resulting from intervertebral disc collapse.[3],[7] Therefore, minimizing postoperative back pain and reducing the reherniation rate remains a challenge for surgeons performing lumbar microdiscectomy in patients with HIVDs.
Interspinous process devices (IPDs), also known as dynamic stabilizers, are a novel technology. They expand the spinal canal, limit extension at the symptomatic level, and reduce the risk of adjacent segmental degeneration related to lumbar fusion surgery.[8] IPDs are considered efficient against mechanical low back pain resulting from spinal instability following discectomy.[9] However, the correlation between the magnitude of radiographic improvement and extent of pain relief was reported to be weak (r = 0.33) in a comparison of the placements of different IPDs.[10] Several systematic reviews have also indicated that the use of an IPD alone for lumbar spinal stenosis was significantly associated with greater low-back-pain scores, higher reoperation rates, and higher costs than bony decompression surgery.[11],[12],[13] Therefore, the benefits of IPD implantation in patients with lumbar degenerative disease remain controversial and may depend strongly on the surgical indication and type of implant.[14]
The Wallis implant designed by Senegas in 1986 is a type of restricted IPD approved to treat lumbar degenerative diseases such as disc herniation, recurrent disc herniation, adjacent segmentation of discs, and mild lumbar stenosis.[14],[15] The adjuvant advantages of the Wallis implant for back pain in patients with a primary lumbar herniated disc following microdiscectomy remain unclear.[16],[17],[18] Therefore, we conducted this study to investigate the effects of the Wallis implant with microdiscectomy on postoperative back pain and quality of life compared with microdiscectomy alone.
Materials and MethodsPatient selection
In this prospective cohort study, patients with a single-level lumbar HIVD who underwent microdiscectomy alone or microdiscectomy followed by fixation of the segment with a Wallis implant (Abbott Spine International, Bordeaux, France) at our Institute between June 2016 and August 2019 were investigated. Our study was approved by the Institutional Review Board of Chia-Yi Christian Hospital in Taiwan (CYCH-IRB No: 10529), and informed consent was obtained from all participants. The inclusion criteria were as follows: (1) presentation of a single-level HIVD with sciatica symptoms; (2) surgical intervention with microdiscectomy alone or microdiscectomy followed by the placement of a Wallis interspinous device; and (3) age between 20 and 80 years. The exclusion criteria were as follows: (1) major systemic disease including hemodialysis, chronic obstructive pulmonary disease, congestive heart failure or intracranial disease with neurological deficits; (2) performance of a previous procedure such as laminectomy, laminotomy, microdiscectomy, or fusion surgery; (3) coexistence of spinal neoplasms, infections, or spondylolisthesis; (4) recurrent disc herniation during the 12- month follow-up; and (5) incomplete questionnaire or radiography. Twenty patients were enrolled.
Clinical outcome evaluations
All the patients completed a questionnaire before the operation and 1, 3, 6, and 12 months after surgery. The questionnaire contained the visual analogue scale (VAS) for back pain and the Oswestry Disability Index (ODI). The VAS score ranged from 0 (no pain) to 100 (worst imaginable pain). The ODI, assessed using 10 questions to quantify disability for low back pain, ranged from 0 (no disability) to 50 (maximal disability).
Radiological evaluations
All the patients received a complete radiographic survey before the operation and 1, 3, 6, and 12 months after surgery. Lateral radiographs of the lumbar spine, such as the flexion and extension views, were obtained. The posterior disc height, foraminal height, foraminal area, and segmental angle were measured [Figure 1]. Posterior disc height was defined as the distance between the posterior – Ninferior margin of the superior vertebra and the posterior– superior margin of the inferior vertebra. Foraminal height was defined as the maximum distance between the inferior margin of the pedicle of the superior vertebra and the superior margin of the pedicle of the inferior vertebra. The foraminal area was measured as the area marked around the margin of the foramen by a picture archiving and communication system. The segmental angle was defined as the angle between the tangent of the inferior endplate of the superior vertebra and the tangent of the superior endplate of the inferior vertebra. Negative and positive values of the segmental angle indicated kyphotic and lordotic angles, respectively. Range of motion was defined as the difference in segmental angles between the flexion and extension views.
Figure 1: Illustration of radiographic measurements: Posterior disc height (red), foraminal height (blue), foraminal area (grey), and segmental angle (purple)Statistical analysis
Statistical analyses were performed using IBM SPSS Statistics for MacOS, version 26.0 (IBM Corp., Armonk, NY, USA). Continuous data are presented as means and their standard deviations. Between-group comparisons were performed using the independent-samples Student's t-test. Differences were considered statistically significant when P < 0.05.
ResultsPatient demographics
Nine patients undergoing microdiscectomy with Wallis implant insertion (Wallis group) and eleven undergoing lumbar microdiscectomy alone (control group) were included. The Wallis group contained six male and three female patients aged 45.7 ± 13.3 years (range 20–61 years). The control group had three male and eight female patients aged 47.6 ± 7.5 years (range 34–58 years). One and eight patients had HIVDs at the L2–3 and L4–5 levels, respectively, in the Wallis group; five and six had HIVDs at the L4–5 and L5–S1 levels, respectively, in the control group. Nine Wallis implants with sizes ranging from 6 to 14 mm were inserted in the Wallis group.
Comparison of Visual Analog Scale changes
All the patients experienced relief from symptoms of sciatica and were without recurrent disc herniation during the 12-month follow-up. The VAS scores for back pain in the two groups are shown in [Table 1] and [Figure 2]a. Compared with the preoperative VAS score, the postoperative VAS score for all patients in the Wallis group was significantly improved at 1 month (P = 0.003), 3 months (P = 0.005), 6 months (P = 0.002), and 12 months (P = 0.001). The improvements were sustained from postoperative month 1 to month 12 (postoperative month 1 vs. 3, P = 0.792; postoperative month 3 vs. 6, P = 0.129; postoperative month 6 vs. 12, P = 0.864). All patients in the control group also had significant VAS score improvements at postoperative month 1 (P < 0.001), 3 (P < 0.001), 6 (P < 0.001), and 12 (P < 0.001) compared with the preoperative VAS score. The improvements were also sustained from postoperative month 1–12 (postoperative month 1 vs. 3, P = 0.333; postoperative month 3 vs. 6, P = 0.312; postoperative month 6 vs. 12, P = 0.174). The postoperative mean VAS scores in the Wallis group at the 1-, 3-, 6-, and 12-months follow-ups were all lower than those in the control group. However, a significantly better mean VAS score in the Wallis group than the control group was achieved only at postoperative month 6 (P = 0.012). These results indicated that microsurgery surgery alone or with placement of the Wallis implant was an effective procedure for managing symptoms related to single-level HIVDs. Patients with the Wallis implant had a lower VAS score for postoperative back pain.
Table 1: Summary of the clinical outcomes of the Wallis and control groups
Figure 2: Changes in VAS score (a) and ODI (b) in the present study. *P < 0.05 for comparisons of the investigating time and preoperative scores, #P < 0.05 for comparisons of the Wallis and control groups. VAS: Visual analogue scale, ODI: Oswestry disability indexComparisons of Oswestry Disability Index changes
Postoperative quality of life was investigated using the ODI [Table 1] and [Figure 2]b. Compared with the preoperative ODI, all patients in the Wallis group reported significant improvements at postoperative months 1 (P = 0.013), 3 (P = 0.001), 6 (P = 0.001), and 12 (P < 0.001). The improvements were sustained from postoperative months 1–12 (postoperative month 1 vs. 3, P = 0.133; postoperative month 3 vs. 6, P = 0.096; postoperative month 6 vs. 12, P = 0.095). In the control group, patients reported significant improvements only at postoperative months 3 (P = 0.002), 6 (P = 0.029), and 12 (P < 0.001) compared with the baseline ODI. The improvements were sustained from postoperative months 3–12 (postoperative month 3 vs. 6, P = 0.248; postoperative month 6 vs. 12, P = 0.178). The postoperative mean ODIs in the Wallis group after 1 month, 3 months, 6 months, and 12 months were all lower than those in the control group. The mean ODI in the Wallis group was significantly higher than that in the control group at postoperative months 1 (P = 0.036) and 12 (P = 0.042). These results showed that the microsurgery procedure effectively improved symptoms related to single-level HIVDs. In addition, placement of the Wallis implant may have provided superior quality of life.
Comparison of disc height changes
The mean posterior disc heights in the Wallis group measured in the flexion and extension views remained similar to those measured preoperatively [Table 2] and [Figure 3]a. Significant loss of posterior disc height in the control group was observed only in the flexion view at postoperative month 3 (P = 0.011) compared with the height at postoperative month 1. Although the patients in the Wallis group had greater mean posterior disc heights in the flexion view at postoperative month 3 and in the extension view at postoperative month 6, the difference was not significant in comparison with the control group.
Table 2: Summary of radiological changes in the Wallis and control groups
Figure 3: Changes in posterior disc height (a), foraminal height (b), foraminal area (c), and segmental angle (d). *P < 0.05 for comparisons of the investigating time and preoperative measurementsComparison of changes in foraminal height and area
The mean foraminal height in the extension view at postoperative month 3 was increased in the Wallis group [Table 2] and [Figure 3]b, but the difference compared with the baseline was not significant. In the control group, the mean foraminal height in the extension view at postoperative month 6 was significantly lower than the baseline height (P < 0.001). The differences in foraminal height between the groups were not significant before or after the operation.
The mean foraminal area of the Wallis group was increased after the operation [Table 2] and [Figure 3]c, especially in the extension view at postoperative month 1 (baseline vs. postoperative month 1, P = 0.022). Compared with the control group, the Wallis group had larger foraminal areas at postoperative months 1, 3, 6, and 12. The differences in foraminal area between the groups were nonsignificant before and after the operation.
Comparison of changes in segmental angles and range of motion
In the Wallis group, significantly reduced segmental angles were observed in the extension view, especially at postoperative months 1 (P = 0.018) and 3 [P = 0.014; [Table 2] and [Figure 3]d compared with preoperative segmental angles. The control group also had significantly lower segmental angles in the extension view at postoperative months 1 (P = 0.007), 3 (P = 0.001), and 12 (P = 0.042) relative to the baseline angles. The differences in segmental angles between the groups before or after the operations were not significant.
The range of motion in the control group was significantly decreased from the preoperative mean of 4.2° to − 0.7° at postoperative month 3 (P = 0.006). The Wallis group had a similar range of motion at postoperative month 3 compared with the preoperative range (3.1° vs. 4.3°, P = 0.497). The difference in range of motion between the groups achieved significance at postoperative month 3 (P = 0.016). This result suggested that the placement of a Wallis implant may result in more extensive preservation of range of motion.
DiscussionWith advances in surgical instruments and surgical techniques, microdiscectomy has become a common surgical option for the management of lumbar radiculopathy.[2] Although most patients have favorable clinical outcomes, overall, complications are estimated to occur after 12.5%, 13.3%, and 10.8% of open microdiscectomy, microdiscectomy, and percutaneous microdiscectomy operations, respectively.[6] Because of aggressive removal of disc material, reherniation is a common challenge for spine surgeons after microdiscectomy.[3],[7] In comparative meta-analyses, the pooled means of the reherniation rate and reoperation rate in patients who underwent a microdiscectomy were estimated to be 4.2% to 5.5% and 5.5% to 8.4%, respectively.[5],[6]
However, postoperative back pain is also a prominent postoperative complaint for patients following discectomy, especially with more aggressive removal of disc tissue.[1],[2],[4] In a retrospective study conducted by Parker et al. of 111 patients following primary single-level discectomy, 36 patients (32%) experienced moderate to severe postoperative back pain at a mean follow-up of 37.3 months.[19] In a systematic literature review of 90 studies and prospective outcome study of 192 patients who underwent discectomy for lumbar disc herniation and radicular leg pain, 22% and 26% of patients reported greater postoperative back pain or disability at 1- year and 2- year follow-ups, respectively, compared with within 3 months.[20] The structural and functional changes of the sensory nervous system in intervertebral disc degeneration may play a key role contributing to mechanic postoperative low back pain following discectomy.[21]
IPDs were developed to reduce mechanic back pain.[9] In a cadaveric study, the biomechanical effects of an IPD on flexibility and intradiscal pressure were investigated, and significantly smaller intradiscal pressure and lower range of motion (50%) in extension relative to the neutral position of the intact segment were discovered.[22] In a study of 129 patients with lumbar spinal stenosis, IPD implantations (X-Stop, DIAM, or Wallis) clinically led to a significant increase in radiologic features such as foraminal height, foraminal width, foraminal cross-sectional area, posterior disc height, and intervertebral angle.[10] Although postoperative back pain improved after the placement of an IPD, the significant correlation between the magnitude of radiographic improvement and extent of pain relief was weak (r = 0.33).[10] Therefore, despite the surgical indication and preoperative muscle atrophy, the design of an IPD may influence the improvement of postoperative low back pain.[14],[23]
The Wallis implant consists of an interspinous polyetheretherketone blocker and two pieces of Dacron tape fixed around the spinous process to restrict the extension and flexion, respectively, restoring the physiological condition to treat low back pain related to degenerative instability following a decompressive procedure.[15],[24] In a 2-year follow-up study of 50 patients with degenerative disease treated with the Wallis implant, Pan et al. reported that an IPD significantly maintained the posterior disc height and neural foraminal height and produced satisfactory clinical outcomes with lower ODI scores and higher the Japanese Orthopedic Association (JOA) scores compared with the preoperative scores.[25] These significant improvements in clinical outcomes and radiological findings were also discovered in a minimum 5- year follow-up of 26 patients who underwent primary discectomy followed by fixation of the Wallis implant.[26] However, in a prospective randomized controlled trial of 60 patients who underwent decompression alone or decompression with the Wallis implant, patients in the Wallis group had lower ODI and lower back pain score, but the results did not reveal a significant difference in comparison with the group receiving decompression alone.[27] Therefore, the effectiveness of the Wallis implant for use in patients with lumbar degenerative disease remains unclear.
For a primary lumbar herniated disc, data comparing the results of discectomy alone and discectomy combined with implantation of the Wallis IPD are limited.[16],[17],[18] In a retrospective controlled study of 72 patients with a primary lumbar herniated disc, Zhou et al. reported that clinical outcomes (VAS score and ODI) significantly improved, and similar results were observed up to the final follow-up for both groups.[18] However, the intergroup differences in preoperative and postoperative scores were not significant, which indicated that the Wallis implant, as a definitive treatment for lumbar disc herniation, did not have an advantage over standard open discectomy alone. In a prospective randomized controlled trial of 77 patients conducted by Gu et al., patients who underwent discectomy combined with the placement of the Wallis implant had significantly more favorable scores (VAS score and ODI) at 12 months after the surgery compared with those receiving discectomy alone. However, the differences in the scores between the groups were relatively small.[16] Although a greater intervertebral disc height and smaller range of motion were sustained in the Wallis group, further investigation at the 3- year follow-up revealed no additional benefit relating to pain relief (VAS and JOA scores and ODI) after the Wallis implantation compared with lumbar discectomy alone.[17]
In our preliminary results, all patients had clinical improvements following microdiscectomy alone or with the Wallis implant. The Wallis group had lower mean of VAS score and ODI at the 1-, 3-, 6-, and 12- month follow-ups compared with the control group. However, a significantly better mean VAS score in the Wallis group compared with the control group was achieved only at postoperative month 6 (P = 0.012), whereas the mean ODI in the Wallis group was significantly better than that in the control group only at postoperative months 1 (P = 0.036) and 12 (P = 0.042). These differences in VAS score and ODI were not consistently significant throughout the full 12 months of follow-up. In the present study, reporting short-term results (12 months of follow-up), microsurgery effectively improved symptoms related to single-level HIVDs. Placement of the Wallis implant may also provide better quality of life, a finding similar to that reported by Gu et al.[16] Otherwise, in our study, maintenance of posterior disc height, foraminal height, and foraminal area was discovered in the Wallis group, especially in the extension view. Although greater posterior disc height and foraminal area were observed in the Wallis group, the difference between the groups was not significant. Furthermore, the changes in segmental angles and the limited range of motion were not in agreement with those in previous reports,[16],[17],[18] which may be attributable to the inclusion of surgery at level L5–S1.
Limitations
Our present study had several limitations. First, the sample was relatively small. Second, the Wallis implant was not placed at the L5–S1 level, and comparisons of different levels may have affected the results. Third, only a 12- month follow-up was investigated. Mid-and long-term results were not obtained. A larger randomized controlled trial should be conducted to investigate the efficacy of the Wallis implant for postoperative back pain following microdiscectomy for patients with a primary HIVD.
ConclusionsOur limited preliminary data indicate that microdiscectomy is an effective surgical method for the treatment of primary lumbar herniated discs. All patients who underwent microdiscectomy alone or with placement of the Wallis implant had significant clinical improvements. Maintenance of posterior disc height, foraminal height, and foraminal area was observed in the Wallis group, especially in the extension view. The Wallis implant may additionally reduce low back pain (VAS score) and improve quality of life (ODI). However, the difference between the two groups was not consistently significant throughout the whole 12 months of follow-up. A larger study with a longer follow-up should be conducted to investigate the efficacy of the Wallis implant with microdiscectomy in patients with a primary lumbar herniated disc.
Acknowledgment
This study was supported by the Ditmanson Medical Foundation Chia-Yi Christian Hospital Research Program (R106-006) and Cathay General Hospital Research Grant (CGH-MR-A10701).
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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