Background and introduction
Cervical spondylosis is an age-related degenerative change in the spine. Radiographic evidence of cervical spondylosis can be observed in more than 85% of those greater than 60 years old [
1]. In cervical spondylosis, herniated discs; osteophytes; arthritic facet joints; buckled, thickened, or ossified ligamentum flavum; and hypertrophy or ossification of the posterior longitudinal ligament may all cause multilevel cervical stenosis, resulting in spinal cord compression. Chronic compression of the cervical spinal cord causes the clinical syndrome of cervical spondylotic myelopathy (CSM) [
2],[
3]. In certain patients who exhibit developmental stenosis of the cervical spine, myelopathy may occur early in life, particularly after hyperextension injuries [
4].
Patients who experience progressive, long-standing, or severe myelopathy are candidates for surgical decompression of the spinal cord [
2],[
5]–[
7]. The options decompressing multilevel stenosis involve anterior or posterior approaches. The factors influencing the operative approach are the location of the cord compression, number of levels involved, sagittal alignment, instability, associated axial neck pain, and risk factors for pseudarthrosis [
7],[
8]. Anterior cervical discectomy with fusion (ACDF), anterior cervical corpectomy with fusion (ACCF), and a combination of both are major anterior approaches that directly eliminate the anterior compression. The posterior options are laminectomy without fusion, laminectomy with instrumented fusion, and laminoplasty. The posterior approach relies on the decompression by both the direct removal of offending posterior structures and indirect posterior translation of the spinal cord; thus, patients should undergo maintenance of lordosis or correctable kyphosis to permit adequate indirect decompression [
5]. Laminoplasty is superior to laminectomy without fusion because it decreases perineural adhesion and late kyphosis. Compared with ACDF, ACCF, or laminectomy involving instrumented fusion, laminoplasty preserves motion segments and prevents fusion-related complications, including bone graft dislodgement, pseudarthrosis, and adjacent segment disease [
5],[
9].
Several types of laminoplasty exist such as Z plasty, open-door laminoplasty, and French-door laminoplasty with variable modifications [
7],[
10]. Laminar Z plasty was devised by Hattori in 1971, reported by Oyama in 1973 [
11], and subsequently modified by Tomimura and Watanabe in 1984 and 1987, respectively. Because of their complexity, these techniques were not popular [
9].
Expansive open-door laminoplasty (EOLP) was developed by Hirabayashi in 1977; which was fixed with suture material between a hinge-side facet capsule and opened laminae. French-door laminoplasty was first documented by Kurokawa in 1982. Both EOLP and French-door laminoplasty became popular, and multiple subtypes of these operations were developed [
9]. Biomechanical studies have demonstrated that the range of motion (ROM) and stability of the cervical spine did not change immediately after expansive laminoplasty [
12],[
13]; however, in one study, the ROM significantly decreased after 6 months. Herkowitz determined that EOLP yields a decompression effect equivalent to that of laminectomy or anterior decompression with fusion [
14],[
15]. Moreover, previous reports on long-term surgical outcomes have indicated the usefulness of conducting laminoplasty to treat patients with CSM [
16]. However, complications have been reported shortly after surgery, and 30%–60% of patients exhibited postoperative neck pain [
17],[
18], 0%–30% (4.7%) exhibited C5 palsy [
19],[
20] and 34% exhibited lamina closure [
21],[
22], thereby compromising the surgical results. In 1996, O'Brien et al. reported a method involving maxillofacial miniplates and screws for securing the laminae in their opened positions [
23]. This design provides primary resistance against closure of the laminae. Conducting EOLP by using miniplates and screw fixation remains a popular technique for treating multilevel CSM; however, few clinical reports have been conducted regarding this method.
Various methods can be employed to open the laminae and fix them to prevent reclosure. When conducting EOLP, we use the scalp clip applier as a special laminae opening tool and fix the opened laminae by using self-bent titanium miniplates. In this study, we present the surgical outcome of treating 104 patients with multilevel CSM by using EOLP secured with titanium miniplates without bone grafting.
Discussion
CSM was proven to result from the narrowing of the normal anteroposterior cervical spinal canal to a critical threshold [
13]. The normal cervical aging process, congenital narrowing aggravated by acute trauma and bony malformations were identified as the primary causes of cervical stenosis that result in myelopathy [
32]. The prognosis of untreated myelopathy was typically poor and conservative treatment was largely ineffective in ceasing the progression of neurological deterioration [
15]. Operations have become a mainstream method of treating. Anterior approaches, (primarily ACDF, ACCF, or a combination of both) could be used to eliminate anterior compression directly and correct kyphotic deformity and instability. These approaches are reserved for pathology less than or equal to three motion segments. Regarding multilevel CSM in four or more motion segments, posterior procedures are the primary treatment options [
5]. Laminectomy, an accepted decompressive procedure for treating multilevel CSM, has been reported to cause an increased incidence of complications, including perineural adhesion, instability, and late kyphosis involving neurological deterioration. Laminectomy with instrumented fusion provides stability and prevents late kyphosis; however, problems related to perineural adhesion and fusion have been reported [
5],[
33]. Laminoplasty, through various modifications and improvements, is considered advantageous for expanding the spinal canal and can preserve the posterior structure of the cervical spine in an effort to secure stability and prevent the formation of a postlaminectomy membrane. In addition, numerous studies have reported satisfactory surgical outcomes among patients receiving laminoplasty [
34]. Hirabayashi described EOLP based on a modification from O'Brien, and the method of using titanium miniplates to secure the opening of spinal canal has remained a popular surgical procedure [
28],[
31]. Customized miniplates have been developed to fix the opened laminae; however, these are expensive and the adaptation can be limited by local anatomy. In this study, we conducted the operations by using self-bent miniplates cut from a long, straight titanium miniplate; using this method is both cheaper and more popular than using customized miniplates. The self-bent miniplates were advantageous because they could be readily applied and shaped and provided effective stability. In our case series, no laminae collapse or implant dislodgement was indicated in the follow-up plain films or CT scans.
In the study of Ratliff, cervical curvature was decreased by 35% and ROM was decreased by 50% after laminoplasty [
35]. The loss of ROM was progressive and plateaued at 18 months postlaminoplasty [
36]. In the biomechanical study of Puttlitz, neck extension-flexion ROM was decreased by approximately 25% at 6 months postlaminoplasty and no obvious kinetic differences were observed between EOLP and French-door laminoplasty [
12]. The study suggested that decreased intervertebral motion should be expected and early rehabilitation therapy should be considered. In the current study, significant decreases in cervical curvature and ROM losses were observed at 3 months postoperation. The cervical curvature had almost returned to preoperative levels at 1 year postoperation. However, the ROM was only partially restored. The mean loss of cervical ROM was 35% at 2 years postoperation. In this study, the reason for the improved cervical curvature and ROM from 3 months to 1 year postoperation was aggressive rehabilitation after removal of the neck collar at 3 months postoperation. Lamina closure has been associated with unsatisfactory clinical outcomes after laminoplasty. It can be defined as a decrease of greater than 10% in the canal-body ratio (i.e., Pavlov ratio) [
21]. In the study of Matsumoto, 34% of patients receiving open-door laminoplasty without plates or spacers on the open sides developed lamina closure [
21]. In the current study, no cases of this complication were observed at 12 months postoperation. Our bent miniplates provided initial resistance and good stability for elevated laminae.
The surgical outcomes and risk factor analyses were primarily assessed using the JOA recovery rate; despite the popularity of this method, it involves certain limitations. Based on the preoperative JOA score, the actual surgical recovery could be distinct among patients who exhibit the same recovery rates. The recovery rate is low among patients who exhibit a low preoperative JOA score, even if they attain the same postoperative scores. Thus, we analyzed the six individual sections of the JOA score to determine how the levels of postoperative improvement and preoperative severity were correlated with the surgical outcome. We also used the Nurick score as a secondary method of assessing postoperative conditions. We determined that sensory and motor deficit in the limbs were highly correlated with the recovery rate, particularly the sensory parts of the upper extremities. We proved that the Nurick score was a strong predictor of surgical outcome. Furthermore, numerous factors affect the postoperative outcomes of patients with CSM. The prognostic factors of outcome after undergoing expansive laminoplasty to treat CSM have been identified as age [
37], symptom duration, comorbidities [
38], congenital narrow spinal canal [
29], myelopathy severity, myelomalacia observed in MRI scans [
11], and sagittal cervical alignment [
15],[
30]. Although each factor is essential for determining the prognosis of postoperative neurological improvement, no reports have described the factor most critical for predicting the surgical outcome. In the current study, increased age, depression disorder, and myelomalacia significantly and negatively affected the surgical outcome; however, further observation and follow-up is necessary.
In this study, the surgical outcomes of laminoplasty in patients with CSM were observed for an average of 25 months. No further deterioration was observed in the clinical and radiographical follow-up results after 12 months postoperation, indicating that surgical outcomes stabilize at month 12. Thus, only data until month 12 are presented in this study. No progression of cervical myelopathy was observed among the patients. Only three patients demonstrated evident C5 palsy (MMT score < 3), and this incidence (2.8%) was relatively low compared with that of the average values (4.7%) that have been reported in the literature [
19],[
20]. Substantial posterior shifts of the spinal cord caused by excessive expansion can readily cause the development of C5 palsy [
20]. This problem could be solved by placing a medial trough as a hinge and lowering the lamina opening to minimize excessive posterior cord drift.
Five patients demonstrated poor wound healing and received prolonged or second admission to undergo debridement and antibiotic treatment. All five patients exhibited Type II DM, which yields elevated wound complication rates; thus, we consulted with metabolism doctors to control patient glucose levels by using medication and diet controls. No subsequent deep tissue infection or osteomyelitis was observed. To prevent severe complications, urgent debridement and antibiotic treatment followed by in-patient wound observation should be administered to those who exhibit poor wound healing. No cases of screw loosening occurred, and we carefully verified the screw purchasing quality intraoperatively. Thick screws are chosen or the fixing of original screws to the other bone area of the opened laminae is warranted when the screws tend to loosen.
Ten patients had developed kyphosis at 3 months postoperation. The reasons for the kyphotic change may be related to disrupted dorsal ligamentous structures, compromised extensor musculature, and the force from the less mobile segment; these factors may be related to late rehabilitation. Several modified surgical techniques have been developed to reduce postoperative neck pain after laminoplasty [
39]. Early postoperative ROM exercises and a decreased period of neck collar protection may improve postoperative neck pain and decrease the loss of cervical ROM [
40]. In the current study, the average level of moderate to severe postoperative neck pain was 42% at 3 months postoperation; this rate was similar to those reported in previous studies [
17],[
18]. The modifications that we implemented required decreased surgical dissection after the careful repair of the semispinalis cervicis muscle and nuchal ligament. In addition, the patients were provided early education regarding neck extension exercise to be practiced while wearing their protective neck collars. After March 2011, we implemented additional changes to our surgical procedures to minimize surgical trauma and reduce postoperative neck pain.
Based on the literature, the mean surgical time for various kinds of laminoplasty was approximately 50–230 min and the mean intraoperative blood loss was 52–370 ml [
26],[
41],[
42]. To conduct the current procedure, we used a scalp clip applier to safely and gently open the laminae, subsequently fixing the opened laminae with self-bent titanium miniplates. The mean blood loss amount and average surgical times were within the normal ranges and the surgical outcomes were satisfactory. We suggest that surgical techniques be chosen based on the experience of the surgeon with specific procedures.
Regarding potential study limitations, the total follow-up period was short and no control group was formed. In addition, no patient-based outcome measures, such as the short-form health survey or subjective satisfaction measure, were assessed in this study. The current results demonstrated that conducting EOLP with miniplates is a safe and effective procedure; furthermore, it yields a low complication rate and can stop the progressive loss of or restore neurological function. The recovery rate in this study was more than 75%, which is comparable to that in previous reports [
43],[
44]. No patients in this study required revision to correct fixation failure, which could have caused lamina closure. This demonstrates that internal fixation facilitates maintaining the position of the lamina.
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.
The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
All authors had substantial contributions to the conception and design of the study and giving of the final approval to the manuscript. KTY, TCY, and WTW participated in the data acquisition. KTY and TCY were responsible for the data interpretation and writing of the manuscript. WTW and RPL were responsible for the manuscript modification and concept clarification. All authors have read and approved the final manuscript.