DOI: https://doi.org/10.21203/rs.3.rs-1202516/v2
Background:Severe and complex cervical spondylotic myelopathy(CSM) requires surgical treatment, usually laminoplasty or laminectomy with lateral mass screw internal fixation. However, the operative effects of these surgical approaches are unclear.Therefore, we aimed to evaluate the clinical effects of posterior cervical laminectomy and lateral mass screw internal fixation in patients with severe and complex CSM.
Methods:We retrospectively analysed 60 patients with severe and complex CSM who underwent posterior cervical laminectomy and lateral mass screw internal fixation between May 2013 and June 2020. C-spine radiographs, computed tomography scans, and magnetic resonance images were used to detect curvature and fusion of the cervical spine, restenosis, and loose/broken internal fixation screws. Clinical efficacy was evaluated using Japanese Orthopaedic Association (JOA)scores, the neck disability index (NDI), Odom’s classification, and the visual analogue scale (VAS) for pain.
Results: At the last follow-up, there was no restenosis or loosened/broken internal fixations. The anterior curvature angle of lordosis (n=46) at the last follow-up was not different from that at baseline (P>0.05). The cervical kyphosis angle (n=14) at the last follow-up was improved compared with that at baseline (P<0.05), as were the JOA, NDI, and VAS scores (all P<0.05). Odom’s classifications at the last follow-up were excellent, good, and fair in 45, 12, and 3patients, respectively.
Conclusions: Posterior cervical laminectomy and lateral mass screw internal fixation achieved satisfactory clinical results in severe and complex CSM cases:the cervical spine was stabilised, achieving spinal decompression while preventing excessive backward drift of the cervical spinal cord.
Severe and complex cervical spondylotic myelopathy (CSM) requires surgical treatment. The most common surgical approaches include the anterior, posterior, and combined anterior and posterior approaches. An anterior approach to the cervical spine is used to remove anterior compressive material; however, it does not provide sufficient decompression for CSM with severe compression of the anterior and posterior long segments [1]. Some patients with CSM have cervical spinal deformities or instability, requiring posterior surgery.
The common methods of posterior cervical spine surgery are laminoplasty and laminectomy with lateral mass screw internal fixation. However, laminectomy with lateral mass screw internal fixationis more suitable for patients with severe multi-level cervical spinal cord compression; it is indirect decompression, with sufficient decompression, and is relatively safe.The principle of this operation is to remove the lamina and ligamentumflavum and enlarge the cervical spinal canal. The dural sac and cervical spinal cord are able to drift backward, relieving or eliminating the compression from the anterior and posterior sides of the spinal cord and achieving direct and indirect decompression [2].Laminectomy with lateral mass screw internal fixation is suitable for CSM caused by severe and complex cervical degeneration, ossification of the posterior longitudinal ligament, thickening of the ligamentum flavum, congenital cervical stenosis, and other factors, accompanied by cervical malformation or instability. The operative effect of posterior laminectomy and lateral mass screw fixation is unclear owing to the complexity and severity of the disease in patients who undergo this surgical treatment[3].
Thus, this study aimed to evaluate the clinical effects of this surgical procedure in patients with severe and complex CSM.We hypothesised that posterior laminectomy and lateral mass screw fixation would result in favourable clinical outcomes.
Patients and study design
Data for patients with complex and severe CSM who underwent posterior cervical laminectomy and lateral mass screw internal fixation between May 2013 and June 2020 at our hospital were retrospectively reviewed. The Ethics Committee of our institution approved this study, and informed consent was obtained from the patients.
The inclusion criteria were as follows: multi-level CSM (no less than three levels) combined with instability (sigmatic vertebral translation in hyperflexion and hyperextension surgery segment>3mm or angle>11°) or deformity (kyphosis angle<20°with mild lateral or anteroposterior displacement); severe medullary symptoms and signs, including Hoffman’s sign and ankle clonus, increased muscle tone, and significant decrease in muscle strength; severe stenosis of the cervical spinal canal suggested on imaging with obvious ischaemic changes in the cervical spinal cord; CSM with discontinuous ossification of the posterior longitudinal ligament and severe anterior and posterior compression; and contraindications for anterior or posterior laminoplasty. Patients with severe anterior and posterior cervical compression with≥60% anterior compression requiring anterior and posterior surgeries were excluded from the study.
Patients were routinely examined using cervical spine lateral and hyperextension radiography, three-dimensional computed tomography, and cervical magnetic resonance(MR)imaging. The post-operative follow-up period ranged from 1 to 6 years (mean 3.6 years).
Surgical methods
Laminectomy and lateral mass screw internal fixation were performed with the patient in the prone position under general anaesthesia. First, a posterior medial incision of the cervical spine was made. The fascia and paravertebral muscles were removed from the spinous process bilaterally to fully expose the lateral mass surface. Lateral mass nails were implanted in C3–7 bilaterally. A grinding drill was used to create a 3-mm wide slot in the inner lamina of the facet joint to reach the inner cortex, and a 1–2-mm thick lamina rongeur was used to bite the inner cortex to complete the slot. Kocher forceps were used to clamp the spinous process and carefully lift the entire lamina from the spinal canal. The lamina was moved to either side, and lamina forceps were used to bite the ligamentumflavum to ensure complete separation from the dural sac. Complete removal of the lamina exposed the sides of the dural sac and the entire surface of the facet joints. If the patient had nerve root-type symptoms, foraminal incision decompression was performed. To maintain cervical lordosis or correct cervical kyphosis, proper compression screws were applied and nuts and connecting rods were installed.C-arm fluoroscopy was used to confirm the ideal position of the internal fixation. Bone granules were implanted on both sides of the lateral mass to promote osseous fusion. All operations were performed by the same surgeon.
Modified surgery
Laminectomy and lateral mass screw internal fixation were combined with 1–2 level laminoplasty to prevent excessive cervical spine drift. The C5 and upper or lower segment were used for the laminoplasty. If the patient had severe neurological symptoms, laminoplasty was approached on the symptomatic side. A drill was used to grind the outer cortex and create a groove at the transition of the lamina and lateral mass. After thinning, the rongeur was used to bite the inner cortex and simultaneously createa ‘door’ 12–14mm wide. The lateral ligamentumflavum was completely loosened and separated. A grinding drill was used on the side of the portal axis to grind off the outer cortex at the junction of the lamina and the lateral mass to form a hinge. The lamina was gently opened at the door until the laminectomy was completed.A curved-arch titanium plate (Synthes GmbH, Zuchwil, Switzerland) was fixed to both ends of the door. Bone granules were implanted in the hinge area to promote bone fusion and form a permanent spinal canal. All operations were performed by the same surgeon.
Post-operative treatment
Antibiotics, mannitol, dexamethasone, nebulised inhalation medications, and other symptomatic therapies were administered to the patients for the first 3–5 days post-operatively. The drainage tube was removed on post-operative day 3–5, and patients were encouraged to ambulate by post-operative day 3–5. Patients wore an immobilising cervical brace for 12 weeks. Cervical spine radiographs and MR images were obtained 1 week post-operatively.
Effect analysis
Imaging evaluations
Cobb’s angle was measured on lateral radiographs of the cervical spine. A positive value indicated lordosis and a negative value indicated kyphosis. The pre- and post-operative angles were compared.
Cervical MR imaging
Cervical MR images were used to detect the degree of backward drift of the cervical spinal cord, re-compression, and obstruction of the cerebrospinal fluid.
Evaluation of clinical efficacy
The Japanese Orthopaedic Association (JOA)scores at baseline and final follow-up were compared to evaluate the improvement in neurological symptoms, the visual analogue scale (VAS) was used to evaluate pain severity, and the cervical neck disability index (NDI) was used to assess the degree of cervical dysfunction. Odom’s classification was used to evaluate the comprehensive clinical efficacy at the last follow-up. The clinical efficacy was classified as follows: excellent in patients whose pre-operative symptoms resolved completely and whose daily lives were no longer affected by their condition,good in patients whose pre-operative symptoms were significantly relieved with no obvious limitations in daily life, general in patients whose pre-operative symptoms were partially relieved and whose daily lives were partially limited, and poor in patients whose pre-operative symptoms did not improve or worsened.
Post-operative complications
The following post-operative complications were evaluated: fusion of the surgical segments, restenosis, loosened or broken internal fixations, cerebrospinal fluid leakage, incision infection, allergic reactions to implant materials, and vascular, nerve, or spinal injuries.
Statistical methods
All analyses were performed with SPSS version 20.0 statistical software (IBM Inc., Chicago, IL, USA). Statistical significance was set at P<0.05. Data are expressed as mean ± standard deviation. The baseline and final cervical physiological curvatures and JOA, VAS, and NDI scores were compared using intra-group t-tests.
In the 60 patients included in this study (Table 1), there were no reports of vascular, nerve, or spinal injuries, cerebrospinal fluid leakage, infection, allergies to implant materials, restenosis, loosening or breakage of the internal fixation, compression of the spinal cord, or obstructed cerebrospinal fluid.
Table 1
General characteristics of the patients
|
Characteristic |
PLF(n＝60) |
|
Sex(male/female) |
48/12 |
|
Age, years (range) |
59.7 (36–76) |
|
Type of cervical spondylosis |
|
|
Instability |
36 |
|
Kyphosis |
14 |
|
Discontinuous ossification of the posterior longitudinal ligament |
10 |
|
Operated level |
|
|
C3–7 |
40 |
|
C4–7 |
8 |
|
C3–6 |
12 |
|
Operative method |
|
|
PLF |
48 |
|
Modified |
12 |
|
F/U period, years (range) |
3.6 (1–6) |
|
Data are presented as the number of patients or mean (range) PLF, posterior laminectomy and lateral mass screw fixation; F/U, follow-up |
|
Among the 46 patients with cervical lordosis, the lordosis angle at the last follow-up was not different from the angle at baseline(P>0.05). Among the 14 patients with cervical kyphosis, the kyphosis angle at the last follow-up was improved compared with the angle at baseline (P<0.05) (Table 2). The JOA, NDI, and VAS scores at the last follow-up were significantly improved compared with the scores at baseline (all P<0.05) (Table 3). According to Odom’s classification, the clinical efficacy at the last follow-up was excellent in 45 patients, good in 12 patients, and general in 3 patients. No patient had poor clinical efficacy. Overall, 95% of the patients achieved excellent or good clinical efficacy.
Table 2
Cervical angle measurements
|
|
Cervical lordosis(n=46) |
Cervical kyphosis(n=14) |
|
Pre-operative |
20.83±2.67 |
9.42±1.80 |
|
Last follow-up |
19.17±2.44 |
3.25±1.64 |
|
P value |
>0.05 |
<0.05 |
Table 3
Neurological function scores
|
|
JOA |
VAS |
NDI |
|
Pre-operative |
9.90±2.44 |
5.40±0.78 |
20.13±4.15 |
|
Last follow-up |
14.90±1.73 |
0.70±0.46 |
8.94±3.27 |
|
P value |
<0.05 |
<0.05 |
<0.05 |
JOA, Japanese Orthopaedic Association; VAS, visual analogue scale; NDI, neck disability index
Two patients experienced mild posterior cervical axial pain that resolved over the course of 3 months. Unilateral C5 nerve palsy occurred in three patients and resolved after a few weeks. Two patients with limb muscle weakness required medication and rehabilitation. One patient experienced limb muscle loss due to a fall, which occurred 1 month post-operatively; the patient recovered after several months. None of the 12 patients who underwent laminectomy and lateral mass screw fixation combined with 1–2 level laminoplasty developed C5 palsy.
In this study, 95% of patients had excellent or good clinical efficacy, and the JOA, VAS, and NDI scores at the last follow-up were improved compared to those at baseline. No cervical MR images revealed cervical spinal cord compression or cerebrospinal fluid obstruction. No loosening, withdrawal, or fractures were observed at the site of the internal fixation. Patients with cervical kyphosis had improved cervical spine curvature at the last follow-up, indicating that laminectomy with lateral mass screw internal fixation with or without laminoplasty can improve cervical kyphosis. In contrast, cervical spine curvature did not improve in patients with cervical lordosis, indicating that laminectomy with lateral mass screw internal fixation with or without laminoplasty can maintain the physiological curvature of the cervical spine (Fig. 1).
Laminoplasty and laminectomy with lateral mass screw internal fixation use a posterior approach to treat CSM. Laminoplasty is indicated for patients with developmental cervical spinal stenosis, cervical disc herniation, and more than three segments of ossification of the posterior longitudinal ligament.Laminectomy with lateral mass screw internal fixation is indicated for patients with CSM and long-segment compression, severe compression, cervical instability, or cervical deformity. Laminectomy with lateral mass screw internal fixation has a higher incidence of C5 nerve palsy than does laminoplasty since excessive backward drift of the cervical spinal cord is not prevented. However, no difference was observed in the recovery of neurological function between the two surgical methods [4, 5], but recurrent nerve compression injuries are more common after laminoplasty because it results in an unstable cervical spine [6].
Laminectomy with lateral mass screw internal fixation has replaced the previous simple posterior cervical laminectomy and is used to treat multi-segment CSM. A simple laminectomy increases the incidence of post-operative kyphosis. Laminectomy with lateral mass screw internal fixation stabilises the cervical spine to prevent complications, including cervical kyphosis [7] and the progression or recurrence of lesions at the surgical segment, and allows surgeons to correct mild, rigid cervical kyphosis to restore the physiological curvature of the cervical spine. The operation is relatively safe, and intervertebral disc-osteophyte complexes can be reduced post-operatively to reduce anterior compression [8]. Compared with laminoplasty, laminectomy with lateral mass screw internal fixation delays the progression of ossification of the posterior longitudinal ligament [9]. However, laminectomy with lateral mass screw internal fixation can lead to posterior cervical axial symptoms mainly caused by imbalance of the muscles of the posterior neck, adhesions, scar compression, and excessive cervical spinal cord drift. This procedure may also result in C5 nerve palsy, cervical spinal cord drift, and unstable activity. Delayed and excessive cervical spinal cord drift can lead to injuries, especially in patients with existing cervical spinal cord disease [10].
The risk of C5 nerve palsy after laminectomy with lateral mass screw internal fixation can be reduced by using a precise surgical protocol to limit the drift of the dural sac [11]. Identifying risk factors to predict complications is also necessary. C5 nerve traction paralysis is associated with the presence of C4–5 intervertebral foraminal stenosis, and preventive decompression of the intervertebral foraminal area can help expand the nerve root canal space [12].
Improvements to the surgical methods of laminectomy with lateral mass screw internal fixation can help reduce the complication rate. Therefore, we combined laminectomy with lateral mass screw internal fixation with laminoplasty of 1–2 spinal segments to prevent excessive cervical spinal cord drift. A previous study reported that laminectomy and internal fixation were performed at the same time as selective blocking, single-doorlaminoplastiesin1–2 spinal segments [13]. Our results indicate that the selective blocking of laminoplasty combined with laminectomy with lateral mass screw internal fixation can prevent excessive backward drift of the cervical spinal cord, reducing the incidence of post-operative C5 paralysis and cervical spinal cord injuries. Inpatients with severe anterior and posterior compression and an anterior occupancy ≤ 60%, the volume of the corresponding segment of the spinal canal can be controlled by adjusting the width of the blocking plate to open the door, preventing excessive posterior drift of the cervical spinal cord. None of the 12 patients who underwent laminectomy and lateral mass screw fixation combined with 1–2 level laminoplasty developed C5 palsy (Fig. 2).
Laminectomy with lateral mass screw fixation is the first choice for patients with severe symptoms or injuries to the cervical spinal cord or canal space. After laminectomy with lateral mass screw internal fixation, the compression in patients with severe anterior and posterior compression cannot change because the cervical spine has been stabilised. Therefore, anterior surgery is not required. No patient in this study required anterior surgery.
Laminectomy with lateral mass screw internal fixation can also correct mild kyphosis with some mobility (kyphosis angle < 20°). The K-line, the straight line connecting the midpoint of the spinal canal from C2 to C7, is often utilised in clinical practice as a reference index for the indication of posterior cervical surgery. When the ossification of the posterior longitudinal ligament range does not exceed the K-line on a standard lateral radiograph, the K-line is positive, and posterior decompression surgery is indicated;when it exceeds the K-line, the K-line is negative, indicating insufficient spinal cord drift. When the spinal canal invasion rate is ≥ 60%, anterior surgery is indicated. However, when the K-line is positive and the spinal canal invasion rate is ≥ 60%, posterior decompression is not contraindicated [14]. Two main factors affect the K-line, namely cervical spine curvature and spinal canal pressure. Changes in these factors affect the selected surgical method. We believe that the curvature of the cervical spine can be changed to affect the K-line to indicate posterior surgery, which is safer and more effective than anterior surgery. When the cervical kyphosis is > 10°–13°, it affects the drift of the cervical spinal cord, and posterior surgery is not indicated. The cervical spine is generally unstable in these patients, and the kyphotic deformity of the cervical spine can be corrected through fixation with side mass screws (Fig. 3).
This study has limitations. First, the sample size of the follow-up cases was small. Second, the follow-up time was insufficient. Further follow-up is needed to verify procedural efficacy.
In conclusion, posterior cervical laminectomy combined with lateral mass screw fixation has excellent clinical efficacy. Combining this surgical method with laminoplasty of 1–2 spinal segments stabilises the cervical spine and provides spinal decompression while preventing excessive backward drift of the cervical spinal cord, resulting in fewer complications.
CSM: cervical spondylotic myelopathy; JOA:Japanese Orthopaedic Association; MR: magnetic resonance; NDI:neck disability index; VAS:visual analogue scale.
Ethics approval and consent to participate:
This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology.Informed consent was obtained from all individual participants included in the study.
Consent for publication:
Written informed consent for publication was obtained from all participants.
Availability of data and materials:
All data generated or analysed during this study are included in this published article and its additional files.
Competing interests:
The authors declare that they have no competing interests.
Funding:
The authors received no financial support for the research, authorship, and/or publication of this article.
Authors’ contributions:
CL, BW, and QXZ developed the idea of the study, participated in its design and co-ordination, and helped draft the manuscript.YCW and HTP contributed to the acquisition and interpretation of data. QXZ provided critical review and substantially revised the manuscript.All authors read and approved the final manuscript.
Acknowledgements:
Not applicable.