Patient selection
In this single-center, retrospective study, we analyzed 52 patients with MCSM with ISI on T2WI who underwent laminoplasty (LP group) from January 2014 to June 2016. As controls, propensity score matching identified 52 patients who underwent laminectomy and fusion (LF group) (1:1) from January 2014 to June 2016 using 7 independent variables (preoperation): age, sex, Japanese Orthopedic Association (JOA) score, Short Form 36 (SF-36) physical component score (PCS), SF-36 mental component score (MCS), preoperative symptom duration and high signal intensity ratio (HSIR).
The patients were chosen according to the following inclusion and exclusion criteria. Inclusion criteria: (1) Features conformed to the diagnostic criteria of MCSM [11, 12]; (2) MRI examination of the cervical spine showed ISI on T2WI; (3) age >18 years; (4) surgery performed by the same surgical team; and (5) positive ‘K-line’ [13]. Exclusion criteria: (1) Cervical congenital malformations and syringomyelia; (2) cervical cancer; (3) ankylosing spondylitis or traumatic injury; (4) cervical kyphosis; (5) decreased signal intensity (DSI) on T1-weighted imaging (T1WI); (6) other severe major organ dysfunction; (7) cervical spine instability (X-ray examination of the cervical spine in flexion and extension showing horizontal displacement of two adjacent vertebrae >3 mm and/or an angle difference >11º between two adjacent vertebral spaces); and (8) previous history of cervical surgery.
The diagnostic criteria of MCSM based on physical and radiographic examinations were as follows: The relevant symptoms included numb hands, clumsy hands, impaired gait, bilateral arm paresthesia, Lhermitte phenomena, and weakness; the patient had least one clinical sign of myelopathy; the relevant signs of myelopathy included corticospinal distribution of motor deficits, atrophy of intrinsic hand muscles, hyperreflexia, positive Hoffman sign, positive Babinski sign, lower limb spasticity, and broad-based unstable gait; MRI examination of the cervical spine showed at least 3 levels of cervical spinal cord compression.
Radiographic and clinical evaluations
X-ray (anteroposterior, flexion, and extension positions), MRI, and computed tomography (CT) examinations were performed before the operation, and X-ray (same positions) and CT examinations were performed at the final follow-up visit. The JOA score, the Visual Analogue Scale (VAS) score, and SF-36 PCS and MCS were recorded before the operation, 12 months after the operation, and at the final follow-up visit. The extension and flexion ranges of motion (ROMs) were recorded before the operation and at the final follow-up visit. In this method, the angle between 2 lines drawn parallel to the posterior surface of the C7 and C2 vertebral bodies was measured [14]. The aforementioned indexes were determined for both groups and compared. Moreover, the operative level, operative duration, blood loss, and surgery-related complications were also recorded and compared.
The intramedullary ISI on T2WI of each patient was recorded before the operation. The MRI data of all patients were analyzed using the image processing software ImageJ (National Institutes of Health, USA). The integrated optical density (IOD) was measured at the location of interest with an area of 0.1 cm2. In the same sagittal plane, the same area was used to measure the IOD at the C7/T1 level with a normal intramedullary signal, and the HSIR was calculated.
Furthermore, a CT scan was performed after each operation. Intraoperative adjustments and screws breaching the bone cortex in any direction by more than 2 mm were defined as unsatisfactory. C5 nerve root paralysis was diagnosed by deltoid weakness, brachialgia, and numbness after the operation[15]. Infection was diagnosed by postoperative fever and increases in the erythrocyte sedimentation rate, C-reactive protein level and white blood cell count after the operation or a positive bacterial wound culture. Axial symptoms (AS) were defined as pain from the nuchal to the periscapular or shoulder region after the operation[16].
Surgical procedures
From January 2014 to June 2016, MCSM patients with ISI on T2WI underwent LP or LF. LP was performed for patients without kyphosis and/or cervical spine instability and/or needing bilateral foraminotomy. LF was performed for patients with kyphosis and/or cervical spine instability and/or needing unilateral foraminotomy. In general, the decision to pursue either LF or LP was made on a case-by-case basis, and patient wishes were taken into account if they fit the indications for both procedures. All patients provided written informed consent.
Each patient was in a prone position on a carbon fiber table. During the entire course of the surgery, neurological function was monitored by somatosensory and motor evoked potentials.
In the LF group, a standard midline posterior approach was used, and the decompression range was determined by the segments of stenosis. Laminectomy was performed after the holes for the lateral mass screws were drilled. The titanium screws were combined with curved titanium rods. The facet joints were decorticated, and autogenous bone was grafted along the lateral masses. Again, a drainage tube was placed in every patient. (Figure 2)
The C2 spinous process and the surrounding muscle were protected during the operation as far as possible[17]. All operations were performed by senior spine surgeons.
Postoperative care
After the operation, the patients who underwent LF wore a brace for 6-8 weeks, while the patients who underwent LP wore a Philadelphia collar for 2 weeks. The drainage tube was removed when the drainage volume was less than 30 ml/24 h. By the third week after the operation, patients in both groups started neck muscle exercises.
Statistical analysis
The statistical analyses were conducted using SPSS, version 22.0 (SPSS, Inc., Chicago, IL, USA). Statistical significance was achieved when P<0.05, and all reported P values were two-tailed. The Kolmogorov–Smirnov test was used to evaluate the normality of the distribution of the obtained data, and the Levene test was used to test for homogeneity of variance. The Mann–Whitney U-test was used for processing non-normally distributed data. Paired and independent samples T-tests were performed to compare normally distributed data. The chi-squared test was performed to compare the operative level, smoking status, total complication rate, and sex.