Background:
The efficacy and noninferior of performing modified double-door laminoplasty (MDDL) (C4–C6 laminoplasty plus C3 laminectomy, alongside a dome-like resection of the inferior part of the C2 lamina and the superior part of the C7 lamina) in patients with multilevel cervical spondylotic myelopathy (MCSM) is equivocal. A randomized, controlled trial is warranted.
Objective:
The objective was to evaluate the clinical efficacy and noninferior of MDDL compared with traditional C3–C7 double-door laminoplasty.
Study design:
A single-blind, randomized, controlled trial.
Methods:
A single-blind, randomized, controlled trial was conducted in which patients who with MCSM with greater than or equal to 3 levels of spinal cord compression from the C3 to the C7 vertebral levels were enrolled and assigned to undergo either MDDL group or conventional double-door laminoplasty (CDDL) group in a 1:1 ratio. The primary outcome was the change in the Japanese Orthopedic Association score from baseline to 2-year follow-up. The secondary outcomes included changes in the Neck Disability Index (NDI) score, the Visual Analog Scale (VAS) for neck pain, and imaging parameters. Operative complications were also collected and reported. The outcome measures were compared between the groups at 3 months, 1 year, or 2 years after surgery.
Results:
A total of 96 patients (mean age 67 years, 39.8% women) underwent randomization. Of these patients, 93 completed 3-month follow-up, 79 completed 1-year follow-up, and 66 completed 2-year follow-up. The changes in the Japanese Orthopedic Association score did not differ significantly between the study groups at the three time points after surgery. With respect to amelioration of neck pain and disability related to neck pain, patients in the MDDL group had a significantly greater decrease in the VAS and NDI component summary score than did those in the CDDL group at 1-year (VAS: −2.5 vs. −3.2, difference −0.7, 95% CI −1.1 to −0.2, P=0.0035; NDI: −13.6 vs. −19.3, difference −5.7, 95% CI −10.3 to −1.1, P=0.0159) and 2-years (VAS: −2.1 vs. −2.9, difference −0.8, 95% CI −1.4 to −0.2, P=0.0109; NDI: −9.3 vs. −16.0, difference −6.7, 95% CI −11.9 to −1.5, P=0.0127). The changes in the range of motion (ROM), the C2–C7 Cobb angle, and the cervical sagittal vertical axis in the MDDL group were significantly less than those in the CDDL group (ROM: −9.2±6.4 vs. −5.0±6.0, P=0.0079; C2–C7 Cobb angle: −7.9±7.8 vs. −4.1±6.2, P=0.0345; cervical sagittal vertical axis: 0.6±0.9 vs. 0.2±0.6, P=0.0233). The MDDL group had less blood loss (428.1 vs. 349.1, P=0.0175) and a lower rate of axial symptoms (27.3 vs. 6.1%, P=0.0475) than the CDDL group.
Conclusions:
Among patients with MCSM, the MDDL produced similar cervical cord decompression compared with the conventional C3–C7 double-door laminoplasty. The modified laminoplasty was associated with meaningful improvement in amelioration of neck discomfort, maintaining a better cervical ROM and sagittal alignment, decreasing blood loss, and reducing the incidence of axial symptoms.
Keywords: axial symptoms, cervical spondylotic myelopathy, Japanese Orthopedic Association score, modified laminoplasty, neck disability index, RCT study, visual analog scale
Introduction
Highlights
The modified laminoplasty with preservation of muscle insertions into the C2 and C7 spinous process achieved similar cervical cord decompression and neurological recovery as the conventional C3–C7 laminoplasty and showed obvious advantages in alleviating postoperative neck discomfort.
The modified laminoplasty showed obvious advantages in maintaining the sagittal alignment and reducing postoperative axial symptoms.
The modified laminoplasty was less invasive, which could reduce intraoperative bleeding and shorten postoperative hospital stay.
Cervical spondylotic myelopathy (CSM) is an age-related degenerative disease that is the most common cause of neurological dysfunction of the spinal cord worldwide1. CSM is characterized by compression of the spinal cord, which presents a series of clinical symptoms and signs such as neck pain or stiffness, bladder dysfunction, gait instability, fine finger motor difficulties, hyperreflexia, weakness, and alteration in proprioception. A clinical practice guideline2 recommended surgical intervention for patients with moderate or severe CSM. For patients with mild CSM who pursue initial nonoperative management, operative intervention is recommended if neurological function fails to improve or deteriorates.
Double-door laminoplasty (DDL) has been an effective posterior cervical decompression method for treating multilevel cervical spondylotic myelopathy (MCSM) since Kurokawa described this operation3,4. Clinical follow-up results indicate that DDL achieves positive clinical outcomes with effective decompression and stable neurologic improvement5,6. In conventional C3–C7 DDL, it is necessary to cut the semispinalis cervicis (SSC) muscle from the C2 spinous process while opening the C3 lamina. In addition, the C3–C7 spinous processes are resected, which will lead to structural damage of the posterior cervical tension band and muscles, resulting in muscle atrophy and cervical sagittal imbalance. Consequently, there are several postoperative complications, such as loss of lordotic curvature, decrease in the neck range of motion (ROM), postoperative kyphotic deformity, and axial symptoms (AS)7–11. To prevent perioperative complications and to improve quality of life, many researchers have modified the traditional surgical techniques by focusing on a minimally invasive surgical approach to preserve the nuchae muscular attachments to the spinous processes. According to previous reports, modified DDL that preserves the SSC insertion into C2 and/or preserves nuchal muscle insertion into C7 can achieve similar decompression. This approach can also maintain a better cervical lordosis curve, reduce ROM loss, and decrease the incidence of postoperative complications including axial neck pain compared with the conventional C3–C7 DDL12–18.
Nevertheless, the importance of preserving the muscle group inserted into the C2 or/and C7 spinous process is equivocal19. To date, there is no class I evidence that modified laminoplasty is not inferior to conventional laminoplasty for the treatment of MCSM. This lack of evidence complicates the effort to develop guidelines and to standardize surgical practice, so a randomized, controlled trial is warranted. In this randomized controlled trial, we modified the posterior surgical approach: we preserved muscular insertion into the C2 and C7 spinous processes. We aimed to investigate whether this modified DDL with a minimally invasive surgical approach is noninferior to conventional DDL in the treatment of CSM. The clinical outcomes were reported here.
Methods
Study design and oversight
We conducted a single-blind, randomized controlled trial at ** Hospital. The trial followed the requirements of the Declaration of Helsinki and was registered as a Chinese domestic clinical trial (ChiCTR**) at Chictr.org. In this trial, patients who with MCSM with greater than or equal to 3 levels of spinal cord compression from the C3 to the C7 vertebral levels were randomly assigned, in a 1:1 ratio, to undergo either modified double-door laminoplasty (MDDL) group or traditional C3–C7 double-door laminoplasty group. The institutional ethics review board approved the trial, and all patients provided written informed consent. The data were managed by an investigator who was not involved in the randomization process and surgery. The trial has been reported in line with Consolidated Standards of Reporting Trials (CONSORT) Guidelines20. All of the authors vouch for the completeness and accuracy of the data and for the trial’s fidelity to the protocol.
Patients
Patients were assessed for MCSM before they underwent randomization. The inclusion criteria for screening and enrollment were age 40–80 years; cervical myelopathy, defined as having two or more of the following typical signs or symptoms of spinal cord compression: fine finger motor difficulties, gait disturbance, hyperreflexia, the Babinski sign, bladder dysfunction, or ankle clonus; three or more levels of spinal cord compression from C3 to C7, confirmed by MRI or computed tomography myelography; and nonoperative treatment with no effect. The exclusion criteria included C2–C7 kyphosis greater than 5° (measured on standing cervical lateral radiographs); cervical instability; previous cervical spinal surgery; cervical spinal cord compression above C3 or below C7; or a significant health-related comorbidity such as cancer, severe cardiovascular diseases, and other critical diseases. A panel of five expert spine surgeons was formed to review a brief clinical vignette plus standardized radiographic and MRI for each patient to assess suitability for randomization. Baseline data were obtained during the perioperative period, and follow-up data were obtained during outpatient follow-up through medical records, imaging examinations, and questionnaires.
Randomization and blinding
Patients were randomly assigned, in a 1:1 ratio, to undergo either MDDL group or conventional double-door laminoplasty (CDDL) group. Randomization was performed with the use of a random number table method and opaque envelopes, which enabled random treatment assignment. Random numbers were selected and concealed in the envelopes. The patients submitted to MDDL or CDDL were determined by odd or even numbers in the envelopes. In this trial, patients, data collectors, and statistical analysts were blinded to the treatment, but surgeons were aware of the treatment.
Interventions
For patients assigned to undergo CDDL, the SSC insertion into the C2 spinous process was detached during posterior cervical muscle dissection, and C3–C7 laminoplasty was performed without preservation of the muscle and ligament complex of the C7 spinous process. In the event of upper C3 involvement, a C2 dome-shaped laminectomy was performed. For patients who were assigned to undergo MDDL, C4–C6 laminoplasty plus C3 laminectomy was used, and a dome-like resection of the inferior part of the C2 lamina and the superior part of the C7 lamina were added after a total laminectomy of C3, in which the muscle and ligament complex insertions into the C2 and C7 spinous processes were preserved (Fig. 1). In both groups, the laminoplasty procedure was adopted for spinous process splitting using a thread-wire saw, and hydroxyapatite spinous process spacers were placed between the split spinous processes to fix them in place. All the trial surgeons were senior consultants and were highly experienced in performing the two trial interventions. All patients had cervical collar fixation for 2 weeks, got out of bed 1 week after surgery, and began neck and shoulder functional exercise 2 weeks after surgery.
Figure 1.
Schematic diagram of the modified double-door laminoplasty. (A) intraoperative image, arrows indicate dome-like resection of the inferior part of the C2 lamina and the superior part of the C7 lamina; (B) postoperative three-dimensional computed tomographic reconstruction.
Outcomes
The primary outcome was the change in the Japanese Orthopedic Association (JOA) score from baseline to 2-year follow-up. This questionnaire comprises six questions with a total score ranging from 0 to 17, where lower scores indicate greater impairment related to spinal cord compression. It has been used and validated to assess treatment outcomes in patients with CSM. The minimal clinically important difference, which was determined based on previous studies, was prespecified to be 2.5 points21,22.
The change in the Neck Disability Index (NDI) score (range 0–100, with higher scores indicating greater disability related to back pain) and the Visual Analog Scale (VAS), (range 0–10, with higher scores indicating a greater degree of neck pain) from baseline to 2-year follow-up were secondary outcome measures. Other secondary outcomes included the change in the imaging parameters to assess cervical alignment and sagittal balance, including ROM, C2–C7 Cobb angle, T1 slope (T1S), thoracic inlet angle (TIA), and cervical sagittal vertical axis (CSVA) 2 years after surgery (shown in Fig. 2).
Figure 2.
Diagram of the imaging measurement. Range of motion, the angle between the posterior edge of the C2 and C7 vertebral body was measured as α1 in the full flexion and as α2 in the full extension radiographs, Range of motion=α1+α2; C2–C7 Cobb angle, the angle between the inferior endplate of C2 and the inferior endplate of C7; T1 slope (T1S), the angle between the T1 superior endplate and the horizontal plane; thoracic inlet angle, the angle between the vertical line of the T1 superior endplate and the line an angle formed by a line perpendicular to the superior endplate of T1 and a line connecting the center of the T1 upper end plate and the upper end of the sternum; cervical sagittal vertical axis, the distance between a plumb line dropped from the center of C2 and the superior posterior aspect of C7. CSVA, cervical sagittal vertical axis; TIA, thoracic inlet angle.
Additional outcome measures were operative complications recorded at 30 days and 2 years after surgery. Complications included those associated with laminoplasty like AS and C5 palsy, and other common complications in spinal operation that occurred within 1 month after surgery, such as spinal cord injury, cerebrospinal fluid fistula, rebleeding, hematoma, fever (unknown source), surgical incision infection, delayed wound healing, venous thromboembolism, urethritis, ileus, spinal cord injury, and reoperation. The length of the procedure, blood loss, the length of stay after surgery, and the quantity of postoperative drainage were also collected and reported.
Statistical analysis
The sample size was estimated based on previous nonrandom prospective or retrospective studies16–18. We reviewed these studies and calculated that the total SD of the postoperative JOA score for all patients involved in the three studies was 2.9. On the conservative assumption of a mean SD of 3 points during the second year, we calculated that a sample of 31 patients per treatment group would be required to provide statistical power of 0.90 with a one-tailed significance level of 0.025 to detect noninferiority of MDDL to CDDL with a 2.5 noninferiority margin (the minimal clinically important difference of the JOA). To account for a possible dropout rate of 20%, 40 patients were required in each group.
The primary analysis included the patients who could be evaluated in the per-protocol population (i.e. patients who had completed at least one follow-up). We used mixed-effects models for repeated measures for the between-group comparisons of changes in the JOA, VAS, and NDI scores from baseline. We included fixed effects for the treatment (CDDL vs. MDDL), time (3 months, 1 year, and 2 years after randomization), and the time × treatment interaction and calculated least-squares means and 95% CI. We computed the robust standard errors and test statistics involving the fixed effects by using the PROC MIXED procedure (SAS Institute). We compared least-squares means between the treatment groups at each time point and between time points within each treatment group by using appropriate contrasts within the mixed-effects models for repeated measures. For other analyses, we performed independent-sample t-tests for continuous variables, which are presented as means and SDs, and the χ 2-test or Fisher’s exact test for categorical variables, which are presented as numbers and percentages.
Results
Patient characteristics
Figure 3 shows the enrollment, randomization, and follow-up for the trial. From July 2015 to December 2018, we screened 257 patients, 134 of whom were eligible. Of these patients, 38 declined to participate in the trial 96 consented to be assigned randomly to one of the two groups. Of the randomized patients, 93 completed at least the 3-month follow-up and were included in this analysis. In addition, 79 patients completed a 1-year follow-up, and 66 completed a 2-year follow-up. The final follow-up date was December 2020. All baseline characteristics were comparable between the two groups (Table 1).
Figure 3.
Consort diagram of participants flow. CDDL, conventional double-door laminoplasty; MDDL, modified double-door laminoplasty.
Table 1.
Baseline characteristics of the patients
| CDDL group | MDDL group | ||
|---|---|---|---|
| Characteristic | (n=47) | (n=46) | P |
| Age—years | 60.0±10.9 | 59.5±10.0 | 0.8342 |
| Female — No/total (%) | 17/47(36.2) | 20/46(43.5) | 0.4716 |
| BMI | 25.6 ±4.8 | 25.8±3.4 | 0.7575 |
| Smoking — No/total (%) | 22/47(46.8) | 20/46(43.5) | 0.7470 |
| Underlying diseases | |||
| Hypertension — No/total (%) | 21/47(44.7) | 20/46(43.5) | 0.9070 |
| Diabetes — No/total (%) | 9/37(19.1) | 10/46(21.7) | 0.7568 |
| Cardio-cerebro-vascular diseases — No/total (%) | 14/47(29.8) | 12/46(26.1) | 0.6910 |
| Respiratory diseases — No/total (%) | 1/47(2.1) | 2/46(4.3) | 0.9849 |
| Urinary system diseases — No/total (%) | 1/47(2.1) | 1/46(2.2) | 1.0000 |
| Kyphosis line — No(negative)/total (%) | 1/47(2.13) | 0 | 1.0000 |
| JOA score | 10.3±1.9 | 10.2±2.5 | 0.8627 |
| VAS score | 4.9±1.4 | 4.8±1.4 | 0.5831 |
| NDI score | 33.7±13.3 | 33.9±16.1 | 0.9451 |
| ROM — degree | 41.1±10.4 | 43.2±9.3 | 0.3958 |
| C2-C7Cobb angle — degree | 18.1±12.1 | 20.2±11.1 | 0.4637 |
| T1S at baseline — degree | 25.3±7.2 | 25.9±6.3 | 0.7320 |
| TIA at baseline — degree | 79.8±9.1 | 81.0±7.8 | 0.5532 |
| CSVA at baseline — cm | 1.9±1.5 | 1.8±1.4 | 0.8489 |
CDDL, conventional double-door laminoplasty; CSVA, cervical sagittal vertical axis; JOA, Japanese Orthopedic Association; MDDL, modified double-door laminoplasty; NDI, Neck Disability Index; ROM, range of motion; T1S, T1 slope; TIA, thoracic inlet angle; VAS, Visual Analog Scale.
Primary outcome
Partial data loss can be allowed in mixed-effects models, so patients who had completed at least one follow-up (93 patients, 47 in the CDDL group and 46 in the MDDL group) were included in the primary outcome analysis. After surgery, patients in both groups had an increased JOA score compared with baseline. As shown in Table 2, there was no significant difference in the least-squares means of the change in the JOA score between the groups at 3 months (3.5 vs. 3.3 points, difference −0.2, 95% CI −0.8 to 0.4, P=0.5415), 1 year (4.1 vs. 3.7 difference −0.4, 95% CI −1.0 to 0.3, P=0.2681), and 2 years (3.6 vs. 3.4, difference −0.2, 95% CI −0.8 to 0.6, P=0.7417). The difference in the JOA score change between the two groups was the smallest at the last follow-up.
Table 2.
Changes in the Japanese Orthopaedic Association (JOA), Visual Analog Scale (VAS), and Neck Disability Index (NDI) scores from baseline
| Change from Baseline | ||||
|---|---|---|---|---|
| Outcomes | CDDL group (n=46) | MDDL group (n=47) | Difference in Change(95%CI) | P |
| JOA score | ||||
| Baseline* | 10.3 | 10.2 | NA | NA |
| 3months | 3.5 | 3.3 | −0.2 (−0.8 to 0.4) | 0.5415 |
| 1year | 4.1 | 3.7 | −0.4 (−1.0 to 0.3) | 0.2681 |
| 2 years | 3.6 | 3.4 | −0.2 (−0.8 to 0.6) | 0.7417 |
| VAS score | ||||
| Baseline* | 4.9 | 4.8 | NA | NA |
| 3months | −3.3 | −3.3 | 0.0 (−0.5 to 0.5) | 0.8820 |
| 1year | −2.5 | −3.2 | −0.7 (−1.1 to −0.2 ) | 0.0035 |
| 2 years | −2.1 | −2.9 | −0.8 (−1.4 to −0.2) | 0.0109 |
| NDI score | ||||
| Baseline* | 33.7 | 33.9 | NA | NA |
| 3months | −21.2 | −22.5 | −1.3 (−6.4 to 3.9) | 0.6346 |
| 1year | −13.6 | −19.3 | −5.7 (−10.3 to −1.1) | 0.0159 |
| 2 years | −9.3 | −16.0 | −6.7 (−11.9 to −1.5) | 0.0127 |
The baseline scores shown are the mean values in group.
CDDL, conventional double-door laminoplasty; JOA, Japanese Orthopedic Association; MDDL, modified double-door laminoplasty; NA, not applicable; NDI, Neck Disability Index; VAS, visual analog scale.
Secondary outcomes
The amelioration of neck pain and disability related to neck pain were measured by the change in the VAS and NDI scores at 3 months, 1 year, and 2 years. Neck pain showed the greatest relief at 3 months after surgery, followed by a slow increase at the 1-year and 2-year follow-ups. As shown in Table 2, there was no significant difference in the change in the VAS and NDI scores between the two groups; however, patients in the MDDL group had a significantly greater decrease in the VAS score and the NDI component summary score than did those in the CDDL group at 1 year (VAS: −2.5 vs. −3.2, difference −0.7, 95% CI −1.1 to −0.2, P=0.0035; NDI: −13.6 vs. −19.3, difference −5.7, 95% CI −10.3 to −1.1, P=0.0159) and 2 years (VAS: −2.1 vs. −2.9, difference −0.8, 95% CI −1.4 to −0.2, P=0.0109; NDI: −9.3 vs.−16.0, difference −6.7, 95% CI −11.9 to −1.5, P=0.0127). We further analyzed the changes in the imaging parameters of the patients. At the 2-year follow-up, the changes in ROM, the C2–C7 Cobb angle, and CSVA in the MDDL group were significantly less than in the CDDL group (ROM: −9.2±6.4 vs.−5.0±6.0, P=0.0079; C2–C7 Cobb angle: −7.9±7.8 vs. −4.1±6.2, P=0.0345; CSVA: 0.6±0.9 vs. 0.2±0.6, P=0.0233), and there were marginal, nonsignificant differences in the change in TIA between the two groups (2.6±4.8 vs. 0.2±5.0, P=0.0584) (Table 3). Blood loss was significantly less in the MDDL group than in the CDDL group (428.1 vs. 349.1, P=0.0175). There was a trend for a shorter length of stay in the MDDL group (12.8 vs. 10.9, P=0.0846). The MDDL group had a lower rate of AS than the CDDL group (27.3% vs. 6.1%, P=0.0475) (Table 4).
Table 3.
Changes in imaging parameters from baseline
| Outcomes | CDDL group | MDDL group | P |
|---|---|---|---|
| ROM at baseline — degree | 41.1±10.4 | 43.2±9.3 | 0.3958 |
| Changes in ROM from baseline to postoperative 2 years — degree | −9.2±6.4 | −5.0±6.0 | 0.0079 |
| C2-C7 Cobb angle at baseline — degree | 18.1±12.1 | 20.2±11.1 | 0.4637 |
| Changes in C2-C7 Cobb angle from baseline to 2 years — degree | −7.9±7.8 | −4.1±6.2 | 0.0345 |
| T1S at baseline — degree | 25.3±7.2 | 25.9±6.3 | 0.7320 |
| Changes in T1S from baseline to 2 years — degree | 2.6±6.3 | 0.8±4.3 | 0.1782 |
| TIA at baseline — degree | 79.8±9.1 | 81.0±7.8 | 0.5532 |
| Changes in TIA from baseline to 2 years — degree | 2.6±4.8 | 0.2±5.0 | 0.0584 |
| CSVA at baseline — cm | 1.9±1.5 | 1.8±1.4 | 0.8489 |
| Changes in CSVA from baseline to 2 years — cm | 0.6±0.9 | 0.2±0.6 | 0.0233 |
CDDL, conventional double-door laminoplasty; CSVA, cervical sagittal vertical axis; MDDL, modified double-door laminoplasty; ROM, range of motion; T1S, T1 slope; TIA, thoracic inlet angle.
Table 4.
Surgical complications
| Complications | CDDL group | MDDL group | P |
|---|---|---|---|
| Length of procedure — min | 135.1±23.8 | 138.7±24.5 | 0.4749 |
| Blood loss — ml | 428.1±145.4 | 349.1±129.2 | 0.0175 |
| Quantity of postoperative drainage — ml | 308.5±159.3 | 264.8±131.6 | 0.1491 |
| Length of stay after operation — days | 12.8±6.3 | 10.9±4.2 | 0.0846 |
| AS — No/total (%) | 9/33 (27.3) | 2/33 (6.1) | 0.0475 |
| C5 palsy — No/total (%) | 1/33 (3.0) | 1/33 (3.0) | 1.0000 |
| Rebleeding — No/total (%) | 1/47 (2.1) | 1/46 (2.2) | 1.0000 |
| Fever (unknown source) — No/total (%) | 1/47 (2.1) | 1/46 (2.2) | 1.0000 |
| Surgical incision infection — No/total (%) | 1/47 (2.1) | 0 | 1.0000 |
| Delayed wound healing — No/total (%) | 1/47 (2.1) | 0 | 1.0000 |
| Urethritis — No/total (%) | 0 | 1/46 (2.2) | 1.0000 |
AS, axial symptoms; CDDL, conventional double-door laminoplasty; MDDL, modified double-door laminoplasty.
Discussion
In this trial, we evaluated whether modified laminoplasty with preservation of muscle and ligament complex insertion into C2 and C7 was noninferior to conventional C3–C7 laminoplasty. The primary outcome measures—the change in cervical spinal cord neurological dysfunction after 2 years, as measured by the JOA score—was not different between the groups. This finding suggests that modified laminoplasty can achieve similar decompression results as conventional laminoplasty. The between-group differences in the decreases in the NDI and VAS scores were clinically meaningful, which were the secondary outcome measures of disability related to neck pain. Hence, MDDL had significant advantages over CDDL in ameliorating postoperative neck discomfort. By reviewing the patients’ imaging data, we found that the modified laminoplasty reduced postoperative cervical ROM loss and helped maintain cervical curvature and sagittal balance. In addition, the modified procedure resulted in less intraoperative bleeding and a shorter postoperative hospital stay because of the smaller surgical approach; more importantly, it also reduced the incidence of postoperative AS.
At present, laminoplasty is the preferred treatment for MCSM in China. However, after surgery, patients are prone to the loss of physiological neck curvature, reduced mobility, and pain, which may be related to the cervical mechanical imbalance caused by the destruction of the neck extensor muscle group during the operation. Neck balancing consists of static and dynamic equilibria. Muscles and ligaments around the neck are considered the components of dynamic stabilizers23,24. It is generally agreed that posterior cervical deep extensors, especially the SSC, act as the primary dynamic stabilizers, maintaining lordosis and alignment of the cervical vertebrae25–27. Thirty-seven percent of the extension moment-generating capacity comes from SSC at the neutral position25. The C7 spinous process also plays an important role in the biomechanics of the cervical posterior extensor muscle. The height of this spinous process increases the moment arm of the extensor muscle complex19. Muscles that attach to the C7—the rhomboideus minor, serratus posterior superior, and splenius capitis—provide a large portion of the extension moment-generating capacity25,28.
Given the anatomical importance of muscle attachments to the C2 and C7 spinous processes, many studies have focused on re-suturing or preserving the C2 and C7 spinous processes and their muscle attachments during laminoplasty. Kurokawa29 modified DDL by preserving the spinous process as long as possible as an anterior support and re-sutured the SSC that had been detached earlier from the C2 spinous process before closure. However, reconstruction possibly failed due to considerable individual variations in the morphologic features of the C2 spinous process and the C2 insertion of the SSC30. Therefore, many researchers have modified laminoplasty (unilateral or double open door) to preserve muscle attachments. Shiraishi et al.31 developed a new surgical technique named skip laminectomy, which preserves the attachments of the SSC and multifidus muscles on the cervical spinous processes and limits the damage to the attachments of the interspinous and rotator muscles. Takeuchi et al.12 presented a modified surgical technique to preserve the SSC insertion into C2 by C4–C7 laminoplasty with C3 laminectomy. The results showed that this modified procedure could reduce the incidence of AS and improve alignment, which are similar to the results we reported in this trial. Kihara et al.13 developed a modified technique, namely C3–C6 laminoplasty plus resection of the superior one third of the C7 lamina to preserve the architecture of the C7 vertebra and attached the nuchal ligament while decompressing the C6–C7 area. Similarly, it has been reported that preserving the C7 spinous process and its muscle attachments can improve postoperative neck discomfort and reduce the incidence of AS15. A meta-analysis32 reported that laminoplasty with C3 laminectomy and C7 spinous process conservation produced a lower incidence of AS than only C3 laminectomy or only C7 spinous process conservation. In the same way, the modified unilateral laminoplasty technique, which preserved muscle attachments to the C2 and C7 spinous process, ensured very good neurological status and ROM after 2 years and was associated with low incidences of axial neck pain and serious complications33.
As mentioned above, muscles that attach to the C2 and C7 spinous processes provide a large part of the posterior extension moment. CDDL damages the muscle attachment to the C2 and C7 spinous processes, which dramatically weakens the mechanical role of the posterior extensor muscle group in maintaining the cervical curvature and sagittal alignment, resulting in the loss of cervical curvature and ROM and sagittal imbalance. We conclude that destroying the posterior extensor muscle group attached to the C2 and C7 spinous processes reduces the neck’s torque and range of posterior extension, thereby reducing the neck ROM. At the same time, with strong relative antagonism of neck flexion, cervical lordosis is hard to maintain, and the head shows a downward trend. For maintaining the head in a neutral position, the undamaged extensor will contract greater, and the curvature of segments without laminoplasty will be compensatory increased. The above changes are shown by a decrease in the C2–C7 Cobb angle and an increase in the T1S, TIA, and CSVA on X-ray film. Prolonged contraction and stretching of muscles lead to pain, stiffness, and even spasm in the neck and shoulders, which may cause AS. The MDDL preserved more posterior neck extensor muscles, which may explain less neck discomfort and a lower incidence of AS after surgery.
Randomized controlled trials provide a high level of clinical evidence and are the gold standard for clinical effect evaluation. However, there are still some limitations to this study. First, this study only considered patients from a single center. Second, more than 30% of the patients were lost to follow-up at 2 years after randomization. Although we recruited additional patients with the approval of the ethics committee to meet the requirements of the minimum sample size, the limitation was still inevitable. Third, the follow-up period was only 2 years, so it was not possible to obtain a long-term efficacy evaluation. In addition, due to the low incidence of complications such AS and C5 palsy, a large number of samples are needed to compare accurately between the groups, so the comparison of complications in this study may be biased. Finally, the contribution of a single structure to the efficacy could not be determined because muscle attachments to C2 and C7 spinous processes were preserved simultaneously. In future studies, it is necessary to increase the sample size, extend the follow-up time, and design a single structure preservation control group to address these limitations.
Conclusions
In this study, we conducted a prospective randomized controlled trial and found that MDDL with preservation of muscle insertions into the C2 and C7 spinous process achieves similar cervical cord decompression and neurological recovery as conventional C3–C7 DDL. MDDL also maintains a better cervical ROM and sagittal alignment, alleviates postoperative neck pain, and reduces the incidence of AS.
Ethical approval
This research was approved by the institutional ethics committee of Beijing Shijitan Hospital (sjtkyll-lx-2017(37)).
Sources of funding
This study was sponsored and funded by Beijing Science and Technology Planning Project (Z151100004015068) and Beijing Natural Science Foundation (Haidian Original Innovation Joint Fund Frontier Project, L202053).
Author contribution
W.L., J.S., and L.D. were involved in study concept and design; W.L. and J.S. drafted the manuscript; S.Y. and Y.Z. recruited and randomized the patients; M. Y. and M. Y. collected and managed the data; Y.F. and Z.L. analyzed the data; L.D. supervised the study.
Conflicts of interest disclosure
The authors declare no conflicts of interest associated with this manuscript.
Research registration unique identifying number (UIN)
Name of the registry: Chinese Clinical Trial Registry
Unique Identifying number or registration ID: ChiCTR1800016810
Hyperlink to your specific registration (must be publicly accessible and will be checked): http://www.chictr.org.cn/showproj.aspx?proj=16644
Guarantor
Professor Lixiang Ding. E-mail address: dinglx@bjsjth.cn
Data availability statement
No additional data are available.
Acknowledgments
The authors thank the patients who consented to participate in this study and all participating staff at the investigational center.
Footnotes
Wancheng Lin and Jipeng Song are the co-first authors.
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
Published online 31 March 2023
Contributor Information
Wancheng Lin, Email: wancheng_lin@163.com.
Jipeng Song, Email: sjpfly@163.com.
Yao Zhang, Email: drzal0221@163.com.
Siyuan Yao, Email: syyao_sjth@163.com.
Meng Yi, Email: 240872640@qq.com.
Mingtao Yao, Email: ymt18170605479@163.com.
Yuyu Fan, Email: fanyy0507@163.com.
Zhengning Luo, Email: 3300719609@qq.com.
Lixiang Ding, Email: dinglx@bjsjth.cn.
References
- 1. Badhiwala JH, Ahuja CS, Akbar MA, et al. Degenerative cervical myelopathy - update and future directions. Nat Rev Neurol 2020;16:108–124. [DOI] [PubMed] [Google Scholar]
- 2. Fehlings MG, Tetreault LA, Riew KD, et al. A clinical practice guideline for the management of degenerative cervical myelopathy: introduction, rationale, and scope. Global Spine J 2017;7(3 suppl):21S–27S. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. Kurokawa T, Tsuyama N, Tanaka H. Enlargement of spinal canal by the sagittal splitting of the spinous process. Bessatusu Seikeigeka 1982;2:234–240. [Google Scholar]
- 4. Luo WQ, Li YY, Zhao JH, et al. Open-versus french-door laminoplasty for the treatment of cervical multilevel compressive myelopathy: a meta-analysis. World Neurosurg 2018;117:129–136. [DOI] [PubMed] [Google Scholar]
- 5. Chen GL, Liu XZ, Chen NN, et al. Ten-year surgical outcomes and prognostic factors for french-door laminoplasty in the treatment of multilevel cervical spondylotic myelopathy. Biomed Res Int 2020;2020:1–8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6. Seichi A, Takeshita K, Ohishi I, et al. Long-term results of double-door laminoplasty for cervical stenotic myelopathy. Spine (Phila Pa 1976) 2001;26:479–487. [DOI] [PubMed] [Google Scholar]
- 7. Matsumoto M, Chiba K, Toyama Y. Surgical treatment of ossification of the posterior longitudinal ligament and its outcomes: posterior surgery by laminoplasty. Spine (Phila Pa 1976) 2012;37:E303–E308. [DOI] [PubMed] [Google Scholar]
- 8. Kimura A, Endo T, Inoue H, et al. Impact of axial neck pain on quality of life after laminoplasty. Spine (Phila Pa 1976) 2015;40:E1292–E1298. [DOI] [PubMed] [Google Scholar]
- 9. Sakaura H, Hosono N, Mukai Y, et al. C5 palsy after decompression surgery for cervical myelopathy: review of the literature. Spine (Phila Pa 1976) 2003;28:2447–2451. [DOI] [PubMed] [Google Scholar]
- 10. Kim SW, Jang SB, Lee HM, et al. Analysis of cervical spine alignment and its relationship with other spinopelvic parameters after laminoplasty in patients with degenerative cervical myelopathy. J Clin Med 2020;9:713. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11. Machino M, Yukawa Y, Hida T, et al. Cervical alignment and range of motion after laminoplasty: radiographical data from more than 500 cases with cervical spondylotic myelopathy and a review of the literature. Spine (Phila Pa 1976) 2012;37:E1243–E1250. [DOI] [PubMed] [Google Scholar]
- 12. Takeuchi K, Yokoyama T, Aburakawa S, et al. Axial symptoms after cervical laminoplasty with C3 laminectomy compared with conventional C3-C7 laminoplasty: a modified laminoplasty preserving the semispinalis cervicis inserted into axis. Spine (Phila Pa 1976) 2005;30:2544–2549. [DOI] [PubMed] [Google Scholar]
- 13. Kihara S, Umebayashi T, Hoshimaru M. Technical improvements and results of open-door expansive laminoplasty with hydroxyapatite implants for cervical myelopathy. Neurosurgery 2005;57:348–356. [DOI] [PubMed] [Google Scholar]
- 14. Takeuchi K, Yokoyama T, Ono A, et al. Cervical range of motion and alignment after laminoplasty preserving or reattaching the semispinalis cervicis inserted into axis. J Spinal Disord Tech 2007;20:571–576. [DOI] [PubMed] [Google Scholar]
- 15. Takeuchi T, Shono Y. Importance of preserving the C7 spinous process and attached nuchal ligament in French-door laminoplasty to reduce postoperative axial symptoms. Eur Spine J 2007;16:1417–1422. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16. Ding LX, Chen YC, Yao Q. Cervical French door laminoplasty with C3 laminectomy and preserve C7 spinous process. Orthoped J China 2009;17:1303–1306. [Google Scholar]
- 17. Wang L, Liu SY, Li HS, et al. Comparative study of Kurokawa’s double door laminoplasty and modified Kurokawa’s double door laminoplasty for the treatment of cervical disorders. Chin J Sur 2013;51:508–512. [PubMed] [Google Scholar]
- 18. Long HQ, Kazumasn U, Liu SY, et al. Cervical bilateral open-door extended laminoplasty with complete preservation of semispinalis cervicis insertion in spinous process of C2. Chin J Clin Anat 2006;24:493–497. [Google Scholar]
- 19. Riew KD, Raich AL, Dettori JR, et al. Neck pain following cervical laminoplasty: does preservation of the c2 muscle attachments and/or c7 matter? Evid Based Spine Care J 2013;4:42–53. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20. Schulz KF, Altman DG, Moher D, et al. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. Brit Med J 2010;340:c332. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21. Oshima Y, Takeshita K, Kato S, et al. Comparison between the japanese orthopaedic association (joa) score and patient-reported joa (pro-joa) score to evaluate surgical outcomes of degenerative cervical myelopathy. Glob Spine J 2022;12:795–800. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22. Kato S, Oshima Y, Matsubayashi Y, et al. Minimum clinically important difference and patient acceptable symptom state of japanese orthopaedic association score in degenerative cervical myelopathy patients. Spine (Phila Pa 1976) 2019;44:691–697. [DOI] [PubMed] [Google Scholar]
- 23. Esmende SM, Daniels AH, Paller DJ, et al. Cervical total disc replacement exhibits similar stiffness to intact cervical functional spinal units tested on a dynamic pendulum testing system. Spine J 2015;15:162–167. [DOI] [PubMed] [Google Scholar]
- 24. Miyamoto S, Yonenobu K, Ono K. Experimental cervical spondylosis in the mouse. Spine (Phila Pa 1976) 1991;16:S495–S500. [DOI] [PubMed] [Google Scholar]
- 25. Vasavada AN, Li SP, Delp SL. Influence of muscle morphometry and moment arms on the moment-generating capacity of human neck muscles. Spine (Phila Pa 1976) 1998;23:412–422. [DOI] [PubMed] [Google Scholar]
- 26. Nolan JP, Sherk HH. Biomechanical evaluation of the extensor musculature of the cervical-spine. Spine (Phila Pa 1976) 1988;13:9–11. [DOI] [PubMed] [Google Scholar]
- 27. Conley MS, Meyer RA, Bloomberg JJ, et al. Noninvasive analysis of human neck muscle function. Spine (Phila Pa 1976) 1995;20:2505–2512. [DOI] [PubMed] [Google Scholar]
- 28. Ono A, Tonosaki Y, Yokoyama T, et al. Surgical anatomy of the nuchal muscles in the posterior cervicothoracic junction - significance of the preservation of the c7 spinous process in cervical laminoplasty. Spine (Phila Pa 1976) 2008;33:E349–E354. [DOI] [PubMed] [Google Scholar]
- 29. Kurokawa T. Double-door laminoplasty by longitudinal splitting of spinous process - modified procedure and its surgical result. Bessatsu Seikeigeka 1986;9:30–32. [Google Scholar]
- 30. Takeuchi K, Yokoyama T, Aburakawa S, et al. Anatomic study of the sennispinalis cervicis for reattachment during laminoplasty. Clin Orthop Relat Res 2005;436:126–131. [DOI] [PubMed] [Google Scholar]
- 31. Shiraishi T, Fukuda K, Yato Y, et al. Results of skip laminectomy - minimum 2-year follow-up study compared with open-door laminoplasty. Spine (Phila Pa 1976) 2003;28:2667–2672. [DOI] [PubMed] [Google Scholar]
- 32. Wang M, Luo XJ, Deng QX, et al. Prevalence of axial symptoms after posterior cervical decompression: a meta-analysis. Eur Spine J 2016;25:2302–2310. [DOI] [PubMed] [Google Scholar]
- 33. Umeda M, Sasai K, Kushida T, et al. A less-invasive cervical laminoplasty for spondylotic myelopathy that preserves the semispinalis cervicis muscles and nuchal ligament clinical article. J Neurosurgery Spine 2013;18:545–552. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
No additional data are available.