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Journal of Back and Musculoskeletal Rehabilitation 28 (2015) 303–309 DOI 10.3233/BMR-140520 IOS Press
Postoperative intervertebral stabilizing effect after cervical laminoplasty Shigeto Ebataa, Hirokazu Satob , Tetsuro Ohbaa , Takashi Andoa and Hirotaka Haroa,∗ a
b
Department of Orthopaedic Surgery, University of Yamanashi, Yamanashi, Japan Department of Orthopaedic Surgery and Spine Center, Saiseikai Kawaguchi General Hospital, Saitama, Japan
Abstract. BACKGROUND: We previously demonstrated short length of rest with a cervical orthosis obtained a decreased tendency for neck or shoulder pain, neck stiffness, and impairment of cervical alignment after cervical laminoplasty. Postoperative maintenance of cervical motion may result in intervertebral instability and poor surgical outcomes. OBJECTIVE: The purpose of this study was to compare the postoperative fusion rate, range of motion (ROM), vertebral listhesis, and surgical outcomes with the duration of rest with a cervical orthosis. METHODS: We conducted cervical laminoplasty on 66 patients with spondylotic myelopathy. All patients were followed for at least two years. Patients remained in bed for two weeks and wore a cervical orthosis for eight weeks postoperatively, postoperative bed rest for seven days and use of an orthosis for four weeks, or postoperative bed rest for five days followed by use of an orthosis for two weeks were assigned. RESULTS: Long rest with a cervical orthosis produced multiple unions and limitation of cervical ROM, resulting in postoperative neck pain. Short rest maintained motion at multiple disc levels. There was no marked difference in neurogenic outcomes between short and long rest. CONCLUSIONS: A short rest period with a cervical orthosis is recommended to maintain cervical motion free from neck pain. Keywords: Cervical laminoplasty, neck pain, orthosis
1. Introduction Cervical spondylotic myelopathy results from both a static factor, a developmental canal stenosis, and a dynamic factor, based on degenerative changes and an unstable spine. Various surgical procedures of cervical laminoplasty are widely used to treat cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament [5,9,11,15,18]. Although cervical laminoplasty has been reported to be superior based on neurological outcomes, preserving spinal stability or preventing postoperative kyphosis or post-laminectomy membrane compared with ∗ Corresponding author: H. Haro, Department of Orthopaedic Surgery, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan. Tel.: +81 55 273 6768; Fax: +81 55 273 9241; E-mail: [email protected].
laminectomy [16], this procedure showed progressive loss of cervical range of motion (ROM), postoperative C5 nerve dysfunction, axial pain, or the occurrence of postoperative membrane resulting in deterioration of neurological function [2,4,6,10,20]. Our procedure is cervical extensive multisegmental laminoplasty consisting of simultaneous mid-dorsal decompression through a median laminar split in, and a lateral gutter on the medial border of the facet joint without injury to the facet joints or pedicles [15]. Our recent study demonstrated that length of rest in combination with a cervical orthosis should be shortened to prevent a tendency for neck or shoulder pain, neck stiffness, and impairment of cervical sagittal alignment [3]. We also revealed that short postoperative rest maintains preoperative cervical range of motion. On the other hand, maintenance of cervical motion after surgery may result in intervertebral instabil-
c 2015 – IOS Press and the authors. All rights reserved ISSN 1053-8127/15/$35.00
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Fig. 1. We investigated neck pain two years postoperatively. Neck pain was determined as excellent (free from pain), fair (always mild pain or sometimes moderate pain), or poor (always severe pain) by patients. Patients either remained in bed for two weeks and wore a cervical orthotic for eight weeks postoperatively (Group A); or remained in bed for seven days and used an orthotic for four weeks (Group B); or were subject to bed rest for five days followed by use of an orthotic for two weeks (Group C). Neck pain was more frequently observed in Groups A and B than in Group C (p < 0.05). ∗ p < 0.05 between Groups A and C.
ity and poor surgical outcomes. Thus, the purpose of the current study is to elucidate postoperative fusion rate, vertebral listhesis, intervertebral ROM, and surgical outcomes in comparison with the duration of rest with a cervical orthosis.
2. Patients and methods Three surgeons were involved in these series. They had all worked as physicians for more than ten years after graduation from medical school and were both board certified orthopaedic surgeons approved by the Japanese Orthopaedic Association and board certified spine surgeons approved by the Japanese Society for Spine Surgery and Related Research. Sixty-six patients (39 male and 27 female, 63.9 ± 11.0 years old) with cervical spondylotic myelopathy underwent cervical extensive multisegmental laminoplasty (Kirita-Miyazaki method). All patients were followed for at least two years. Patients were divided into three groups. Twenty-three patients (15 male and 8 female, 66.48 ± 9.8 years old) in Group A, who were seen between 1994 and May 1998, stayed in bed for two weeks and used a cervical orthosis for eight weeks postoperatively. Twenty-two patients (12 male and 10
female, 64.09 ± 4.4 years old) in Group B, who were seen between June 1998 and May 2000, received postoperative rest in bed for seven days and used an orthosis for four weeks. Twenty-one patients (12 male and 9 female, 61.09 ± 10.7 years old) in Group C were seen between June 2000 and May 2002, and were assigned postoperative rest for five days followed by an orthosis for two weeks. We excluded seven dropout patients, including three in Group A, three in Group B, and one in Group C due to a brain infarct, gastric ulcer, delirium, or failure to visit the out-patient clinic, and excluded them from the current series. The surgical procedure was unchanged from 1994 to 2002. All patients performed physical and occupational exercise for clumsiness or spastic gait immediately after postoperative bed rest. Neck pain was determined as excellent (free from pain), fair (always mild pain or sometimes moderate pain), and poor (always severe pain) by patients two years postoperatively. Cervical myelopathy was assessed pre- and postoperatively using the Japanese Orthopaedic Association (JOA) score [22]. Surgical outcomes were assessed by comparing range of motion (ROM) of C2-C7 from preoperative, and 6-month, 1-year, and 2-year postoperative lateral radiographs in flexion and extension. Intervertebral fusion, defined as complete loss of adjacent intervertebral ROM, and ver-
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A
B Fig. 2. A. Postoperative intervertebral bony fusion (IBF) was determined as a complete loss of adjacent intervertebral ROM on plain radiographs. IBF was observed in 91% (cases) and 53% (levels) in Group A, 82% (cases) and 39% (levels) in Group B, and 43% (cases) and 21% (levels) in Group C respectively. Fusion rate was more frequently observed in Group A than in Group C (∗ p < 0.05). B. The intervertebral fusion rate of each disc level in each group was evaluated on pre- and postoperative plain radiographs. In addition, the C2-3 level was most commonly fused whereas C4-5 was rarely fused. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/BMR-140520)
tebral listhesis, defined as more than 2 mm between adjacent vertebrae, were evaluated from plain radiographs. Cases were classified into two groups: stabilized, which showed less than 2 mm vertebral listhesis, and unstabilized. Radiographic analysis was performed by two independent doctors in a blinded fashion. Statistical analysis was performed to evaluate differences in intervertebral fusion, vertebral listhesis, intervertebral ROM, and the JOA score among groups using the Wilcoxon rank sum test. Specific ethics approval for the current study was not required according to a waiver issued by the ethics
committee in our institute, because this manuscript was a retrospective study using data collected in consecutive years, and because all patients signed informed consent before their surgical procedures.
3. Results 3.1. Postoperative neck pain and surgical outcomes Neck pain was reported more commonly in Groups A and B than in Group C two years postoperatively
S. Ebata et al. / Postoperative intervertebral stabilizing effect after cervical laminoplasty
Result of two years after the operation(%)
306
Fig. 3. We classified cases into two groups depending on whether they showed less than 2 mm vertebral listhesis (stabilized) or more than 2 mm (unstabilized) two years postoperatively. Vertebral olisthesis more commonly was fused in Group A than in Group C. ∗ p < 0.05.
(Fig. 1). We performed a statistical analysis comparing the groups for neck pain and found a significant difference between Group C with Groups A and B using the Student t test (p < 0.05). We evaluated surgical outcomes of patients with JOA score for cervical myelopathy. Preoperative JOA score was 8.1 ± 2.9 in Group A, 8.3 ± 2.3 in Group B, and 9.5 ± 3.0 in Group C respectively, whereas postoperative JOA score was 11.9 ± 2.7 in group A, 12.2 ± 2.2 in group B, and 13.7 ± 2.5 in Group C respectively. The rate of improvement post-operatively compared to pre-operatively was 46.4 ± 21.9 in Group A, 46.1 ± 18.3 in Group B, and 56.7 ± 24.9 in Group C. All groups significantly improved postoperatively (p < 0.05). 3.2. Postoperative interlaminar bony fusion (IBF) More than one level of intervertebral fusion postoperatively was found in 18 cases among 20 cases (61 intervertebral levels among 115 levels) in Group A, 15 cases among 19 cases (43 intervertebral levels among 110 levels) in Group B, and 9 cases among 20 cases (22 intervertebral levels among 105 levels) in Group C (Fig. 2A). We performed a statistical analysis comparing the groups for fusion rate and found a significant difference between Group C and Group A using the student t test (p < 0.05). The C2-3 interver-
tebral level was most commonly fused, whereas C4-5 was rarely fused (Fig. 2B). Although 56.5% in Group A showed intervertebral fusion at 6 months after the surgery, 81.8% or 66.7% of Groups B or C took more than one year to fuse postoperatively. 3.3. Sequential change of vertebral olisthesis The C4-5 intervertebral level was the most common to experience vertebral olisthesis preoperatively, whereas olisthesis was not observed at the C6-7 level. In Group A, 85.7% (12 cases) were stabilized (< 2 mm olisthesis by two years after surgery), compared to 68.9% (11 cases) in Group B, and 25% (6 cases) in Group C (Fig. 3) (p < 0.05, Group A > Group B > Group C). 3.4. Postoperative sequential ROM We examined range of motion from C2 to C7 between anterior flexion and posterior extension before and after the surgery. All groups had significantly decreased ROM over time. C2-C7 ROM two years after surgery was reduced to 46.6% in Group A, 54.3% in Group B, and 71.9% in Group C of pre-operative values and showed significant differences between groups at 6 months, 1 year, and 2 years postopera-
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Fig. 4. We examined the range of motion from C2 to C7 between anterior flexion and posterior extension on plain radiographs pre- and postoperatively. Although all groups showed a significant decrease in ROM over time, and significant differences were found among the groups at 6 months, 1 year, and 2 years postoperatively, Group A had a greater reduction of ROM compared with Groups B and C. ∗ p < 0.05. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/BMR-140520)
tively (p < 0.05) (Fig. 4). Group C maintained intervertebral mobility compared to pre-operative values whereas Group A had significantly reduced ROM compared with Groups B and C (p < 0.05). 4. Discussion An extensive simultaneous multisegment laminectomy for treatment of cervical ossification of the posterior longitudinal ligament was initially established as a safer posterior decompression procedure for the spinal cord compared to traditional laminectomy, and resulted in marked improvement of surgical outcomes [15]. Various laminoplasty techniques for cervical spondylotic myelopathy have been reported [5,9, 11,15,18]. Their surgical outcomes showed excellent results, leading to expansion of the spinal canal, complete decompression of the spinal cord and support of the posterior structure of the cervical spine. However, there have been no marked differences of surgical outcomes postoperatively among these surgical procedures [16]. When laminoplasty was first developed, patients were made to lie down in bed for at least one month postoperatively and then use a cervical orthosis for two or three months. Recent work has demonstrated that postoperative long-term cervical rest with an orthosis stabilized the cervical spine, but also resulted in axial symptoms of neck or shoulder pain, neck stiffness or rigidity due to ossification at facet joints at decompres-
sion sites, and impairment of cervical alignment on lateral views of the cervical spine [7,9,12]. In addition, strong mechanical stresses were concentrated at a few unfused intervertebral joints due to many intervertebral bony fusions, resulting in long-term progressive disc degeneration and neurological impairment postoperatively. Therefore we changed the strategy of postoperative treatment to reduce the period of cervical rest to maintain mobility at many cervical intervertebral levels. However, there are few reports describing how soon after surgery intervertebral fusion occurs, or the rate at which it occurs in patients. Although our current report is retrospective, we demonstrated that long rest with a cervical orthosis produced multiple intervertebral unions and short rest maintained multiple intervertebral motion. There was no marked difference in clinical outcomes between short and long rest, although induction of neck pain was most common in the long rest group (Group A). Intervertebral instability is one of the crucial factors leading to cervical spondylotic myelopathy. However there is no universal definition of intervertebral instability. Some define it as more than 3.5 mm vertebral listhesis and more than 11 degrees of intervertebral ROM [21], whereas others define it as more than 2 mm of vertebral listhesis [13,19]. Previous reports showed that the C4-5 level is the most common in anterior listhesis, ranging between 36–50% of cases [1, 11,13]. Both postoperative sagittal alignment and vertebral listhesis were affected by curvature of the lower cervical spine (C5-7) [14]. Interestingly, preoperative
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intervertebral instability has been strongly related to the onset of cervical myelopathy, but there are many studies showing that postoperative listhesis did not result in impairment of surgical outcomes, postoperative cervical alignment, or reduced ROM [7,8,10,14]. Our study demonstrated that long rest with a cervical orthosis resulted in stabilization of vertebral listhesis and multiple intervertebral unions. However, short rest did not show progression of listhesis or impairment of surgical outcomes. Therefore short rest treatment is not related to negative postoperative surgical outcomes. In addition, we found C4-5 was rarely fused, but commonly produced vertebral listhesis. C2-3 was the most common level for intervertebral fusion, and C6-7 was the least common for vertebral listhesis. We speculate that the mechanism for this relates to the anatomical structure, as C4-5 is at the apex of the cervical lordosis. Following any kind of laminoplasty, postoperative cervical ROM is reduced to almost 60% compared with preoperative ROM following three months of postoperative rest [6,8,9]. Limitation of anterior flexion spares the cervical spinal cord from compression, resulting in satisfactory surgical outcomes [11,14,17]. However, many physicians choose relatively short rest periods, raising the concern that the maintenance of cervical ROM would lead to impairment of surgical outcomes. However, our work shows there is no marked impairment of surgical outcomes following postoperative treatment of rest with use of an orthosis. This study confirmed our previous study that axial pain and complaints related to cervical motion are significantly less in groups with a shorter rest period (Group C vs. Groups A or B) [3]. Intervertebral fusion was obtained in two years at C3-4, 4-5, 5-6, 6-7 levels and in three years at the C2-3 level when postoperative rest for 3 to 4 weeks was selected [8]. Thus we must observe patients suffering from cervical spondylotic myelopathy for much longer periods to reveal when intervertebral fusion is complete or whether listhesis has progressed postoperatively. Based on our current study, we demonstrated that a relatively short rest period post-operatively resulted in maintenance of cervical ROM and reduction in complications such as axial neck pain, and did not change the incidence of the onset of listhesis or the tendency of vertebral listhesis to progress. However, there are several limitations to the current study, including patient selection that occurred long ago. Thus, we have continued this research to prospectively elucidate the relationships between postoperative rest and cervical spinal function, ADL, and pain.
5. Conclusion We classified our patients into three groups and assigned them to post-operative treatment of different durations (8, 4, or 2 weeks) of cervical rest with an orthosis. We measured pain, intervertebral fusion, vertebral listhesis, and range of motion. Postoperatively, a short rest period showed no marked difference in surgical outcomes in groups with longer rest periods by JOA score, but decreased the tendency for both axial neck pain and intervertebral fusion, and maintained ROM of the cervical spine. In addition, the short postoperative treatment did not result in impairment of intervertebral instability.
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Journal of Back and Musculoskeletal Rehabilitation 28 (2015) 303–309 DOI 10.3233/BMR-140520 IOS Press
Postoperative intervertebral stabilizing effect after cervical laminoplasty Shigeto Ebataa, Hirokazu Satob , Tetsuro Ohbaa , Takashi Andoa and Hirotaka Haroa,∗ a
b
Department of Orthopaedic Surgery, University of Yamanashi, Yamanashi, Japan Department of Orthopaedic Surgery and Spine Center, Saiseikai Kawaguchi General Hospital, Saitama, Japan
Abstract. BACKGROUND: We previously demonstrated short length of rest with a cervical orthosis obtained a decreased tendency for neck or shoulder pain, neck stiffness, and impairment of cervical alignment after cervical laminoplasty. Postoperative maintenance of cervical motion may result in intervertebral instability and poor surgical outcomes. OBJECTIVE: The purpose of this study was to compare the postoperative fusion rate, range of motion (ROM), vertebral listhesis, and surgical outcomes with the duration of rest with a cervical orthosis. METHODS: We conducted cervical laminoplasty on 66 patients with spondylotic myelopathy. All patients were followed for at least two years. Patients remained in bed for two weeks and wore a cervical orthosis for eight weeks postoperatively, postoperative bed rest for seven days and use of an orthosis for four weeks, or postoperative bed rest for five days followed by use of an orthosis for two weeks were assigned. RESULTS: Long rest with a cervical orthosis produced multiple unions and limitation of cervical ROM, resulting in postoperative neck pain. Short rest maintained motion at multiple disc levels. There was no marked difference in neurogenic outcomes between short and long rest. CONCLUSIONS: A short rest period with a cervical orthosis is recommended to maintain cervical motion free from neck pain. Keywords: Cervical laminoplasty, neck pain, orthosis
1. Introduction Cervical spondylotic myelopathy results from both a static factor, a developmental canal stenosis, and a dynamic factor, based on degenerative changes and an unstable spine. Various surgical procedures of cervical laminoplasty are widely used to treat cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament [5,9,11,15,18]. Although cervical laminoplasty has been reported to be superior based on neurological outcomes, preserving spinal stability or preventing postoperative kyphosis or post-laminectomy membrane compared with ∗ Corresponding author: H. Haro, Department of Orthopaedic Surgery, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan. Tel.: +81 55 273 6768; Fax: +81 55 273 9241; E-mail: [email protected].
laminectomy [16], this procedure showed progressive loss of cervical range of motion (ROM), postoperative C5 nerve dysfunction, axial pain, or the occurrence of postoperative membrane resulting in deterioration of neurological function [2,4,6,10,20]. Our procedure is cervical extensive multisegmental laminoplasty consisting of simultaneous mid-dorsal decompression through a median laminar split in, and a lateral gutter on the medial border of the facet joint without injury to the facet joints or pedicles [15]. Our recent study demonstrated that length of rest in combination with a cervical orthosis should be shortened to prevent a tendency for neck or shoulder pain, neck stiffness, and impairment of cervical sagittal alignment [3]. We also revealed that short postoperative rest maintains preoperative cervical range of motion. On the other hand, maintenance of cervical motion after surgery may result in intervertebral instabil-
c 2015 – IOS Press and the authors. All rights reserved ISSN 1053-8127/15/$35.00
304
S. Ebata et al. / Postoperative intervertebral stabilizing effect after cervical laminoplasty
Fig. 1. We investigated neck pain two years postoperatively. Neck pain was determined as excellent (free from pain), fair (always mild pain or sometimes moderate pain), or poor (always severe pain) by patients. Patients either remained in bed for two weeks and wore a cervical orthotic for eight weeks postoperatively (Group A); or remained in bed for seven days and used an orthotic for four weeks (Group B); or were subject to bed rest for five days followed by use of an orthotic for two weeks (Group C). Neck pain was more frequently observed in Groups A and B than in Group C (p < 0.05). ∗ p < 0.05 between Groups A and C.
ity and poor surgical outcomes. Thus, the purpose of the current study is to elucidate postoperative fusion rate, vertebral listhesis, intervertebral ROM, and surgical outcomes in comparison with the duration of rest with a cervical orthosis.
2. Patients and methods Three surgeons were involved in these series. They had all worked as physicians for more than ten years after graduation from medical school and were both board certified orthopaedic surgeons approved by the Japanese Orthopaedic Association and board certified spine surgeons approved by the Japanese Society for Spine Surgery and Related Research. Sixty-six patients (39 male and 27 female, 63.9 ± 11.0 years old) with cervical spondylotic myelopathy underwent cervical extensive multisegmental laminoplasty (Kirita-Miyazaki method). All patients were followed for at least two years. Patients were divided into three groups. Twenty-three patients (15 male and 8 female, 66.48 ± 9.8 years old) in Group A, who were seen between 1994 and May 1998, stayed in bed for two weeks and used a cervical orthosis for eight weeks postoperatively. Twenty-two patients (12 male and 10
female, 64.09 ± 4.4 years old) in Group B, who were seen between June 1998 and May 2000, received postoperative rest in bed for seven days and used an orthosis for four weeks. Twenty-one patients (12 male and 9 female, 61.09 ± 10.7 years old) in Group C were seen between June 2000 and May 2002, and were assigned postoperative rest for five days followed by an orthosis for two weeks. We excluded seven dropout patients, including three in Group A, three in Group B, and one in Group C due to a brain infarct, gastric ulcer, delirium, or failure to visit the out-patient clinic, and excluded them from the current series. The surgical procedure was unchanged from 1994 to 2002. All patients performed physical and occupational exercise for clumsiness or spastic gait immediately after postoperative bed rest. Neck pain was determined as excellent (free from pain), fair (always mild pain or sometimes moderate pain), and poor (always severe pain) by patients two years postoperatively. Cervical myelopathy was assessed pre- and postoperatively using the Japanese Orthopaedic Association (JOA) score [22]. Surgical outcomes were assessed by comparing range of motion (ROM) of C2-C7 from preoperative, and 6-month, 1-year, and 2-year postoperative lateral radiographs in flexion and extension. Intervertebral fusion, defined as complete loss of adjacent intervertebral ROM, and ver-
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305
A
B Fig. 2. A. Postoperative intervertebral bony fusion (IBF) was determined as a complete loss of adjacent intervertebral ROM on plain radiographs. IBF was observed in 91% (cases) and 53% (levels) in Group A, 82% (cases) and 39% (levels) in Group B, and 43% (cases) and 21% (levels) in Group C respectively. Fusion rate was more frequently observed in Group A than in Group C (∗ p < 0.05). B. The intervertebral fusion rate of each disc level in each group was evaluated on pre- and postoperative plain radiographs. In addition, the C2-3 level was most commonly fused whereas C4-5 was rarely fused. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/BMR-140520)
tebral listhesis, defined as more than 2 mm between adjacent vertebrae, were evaluated from plain radiographs. Cases were classified into two groups: stabilized, which showed less than 2 mm vertebral listhesis, and unstabilized. Radiographic analysis was performed by two independent doctors in a blinded fashion. Statistical analysis was performed to evaluate differences in intervertebral fusion, vertebral listhesis, intervertebral ROM, and the JOA score among groups using the Wilcoxon rank sum test. Specific ethics approval for the current study was not required according to a waiver issued by the ethics
committee in our institute, because this manuscript was a retrospective study using data collected in consecutive years, and because all patients signed informed consent before their surgical procedures.
3. Results 3.1. Postoperative neck pain and surgical outcomes Neck pain was reported more commonly in Groups A and B than in Group C two years postoperatively
S. Ebata et al. / Postoperative intervertebral stabilizing effect after cervical laminoplasty
Result of two years after the operation(%)
306
Fig. 3. We classified cases into two groups depending on whether they showed less than 2 mm vertebral listhesis (stabilized) or more than 2 mm (unstabilized) two years postoperatively. Vertebral olisthesis more commonly was fused in Group A than in Group C. ∗ p < 0.05.
(Fig. 1). We performed a statistical analysis comparing the groups for neck pain and found a significant difference between Group C with Groups A and B using the Student t test (p < 0.05). We evaluated surgical outcomes of patients with JOA score for cervical myelopathy. Preoperative JOA score was 8.1 ± 2.9 in Group A, 8.3 ± 2.3 in Group B, and 9.5 ± 3.0 in Group C respectively, whereas postoperative JOA score was 11.9 ± 2.7 in group A, 12.2 ± 2.2 in group B, and 13.7 ± 2.5 in Group C respectively. The rate of improvement post-operatively compared to pre-operatively was 46.4 ± 21.9 in Group A, 46.1 ± 18.3 in Group B, and 56.7 ± 24.9 in Group C. All groups significantly improved postoperatively (p < 0.05). 3.2. Postoperative interlaminar bony fusion (IBF) More than one level of intervertebral fusion postoperatively was found in 18 cases among 20 cases (61 intervertebral levels among 115 levels) in Group A, 15 cases among 19 cases (43 intervertebral levels among 110 levels) in Group B, and 9 cases among 20 cases (22 intervertebral levels among 105 levels) in Group C (Fig. 2A). We performed a statistical analysis comparing the groups for fusion rate and found a significant difference between Group C and Group A using the student t test (p < 0.05). The C2-3 interver-
tebral level was most commonly fused, whereas C4-5 was rarely fused (Fig. 2B). Although 56.5% in Group A showed intervertebral fusion at 6 months after the surgery, 81.8% or 66.7% of Groups B or C took more than one year to fuse postoperatively. 3.3. Sequential change of vertebral olisthesis The C4-5 intervertebral level was the most common to experience vertebral olisthesis preoperatively, whereas olisthesis was not observed at the C6-7 level. In Group A, 85.7% (12 cases) were stabilized (< 2 mm olisthesis by two years after surgery), compared to 68.9% (11 cases) in Group B, and 25% (6 cases) in Group C (Fig. 3) (p < 0.05, Group A > Group B > Group C). 3.4. Postoperative sequential ROM We examined range of motion from C2 to C7 between anterior flexion and posterior extension before and after the surgery. All groups had significantly decreased ROM over time. C2-C7 ROM two years after surgery was reduced to 46.6% in Group A, 54.3% in Group B, and 71.9% in Group C of pre-operative values and showed significant differences between groups at 6 months, 1 year, and 2 years postopera-
S. Ebata et al. / Postoperative intervertebral stabilizing effect after cervical laminoplasty
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Fig. 4. We examined the range of motion from C2 to C7 between anterior flexion and posterior extension on plain radiographs pre- and postoperatively. Although all groups showed a significant decrease in ROM over time, and significant differences were found among the groups at 6 months, 1 year, and 2 years postoperatively, Group A had a greater reduction of ROM compared with Groups B and C. ∗ p < 0.05. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/BMR-140520)
tively (p < 0.05) (Fig. 4). Group C maintained intervertebral mobility compared to pre-operative values whereas Group A had significantly reduced ROM compared with Groups B and C (p < 0.05). 4. Discussion An extensive simultaneous multisegment laminectomy for treatment of cervical ossification of the posterior longitudinal ligament was initially established as a safer posterior decompression procedure for the spinal cord compared to traditional laminectomy, and resulted in marked improvement of surgical outcomes [15]. Various laminoplasty techniques for cervical spondylotic myelopathy have been reported [5,9, 11,15,18]. Their surgical outcomes showed excellent results, leading to expansion of the spinal canal, complete decompression of the spinal cord and support of the posterior structure of the cervical spine. However, there have been no marked differences of surgical outcomes postoperatively among these surgical procedures [16]. When laminoplasty was first developed, patients were made to lie down in bed for at least one month postoperatively and then use a cervical orthosis for two or three months. Recent work has demonstrated that postoperative long-term cervical rest with an orthosis stabilized the cervical spine, but also resulted in axial symptoms of neck or shoulder pain, neck stiffness or rigidity due to ossification at facet joints at decompres-
sion sites, and impairment of cervical alignment on lateral views of the cervical spine [7,9,12]. In addition, strong mechanical stresses were concentrated at a few unfused intervertebral joints due to many intervertebral bony fusions, resulting in long-term progressive disc degeneration and neurological impairment postoperatively. Therefore we changed the strategy of postoperative treatment to reduce the period of cervical rest to maintain mobility at many cervical intervertebral levels. However, there are few reports describing how soon after surgery intervertebral fusion occurs, or the rate at which it occurs in patients. Although our current report is retrospective, we demonstrated that long rest with a cervical orthosis produced multiple intervertebral unions and short rest maintained multiple intervertebral motion. There was no marked difference in clinical outcomes between short and long rest, although induction of neck pain was most common in the long rest group (Group A). Intervertebral instability is one of the crucial factors leading to cervical spondylotic myelopathy. However there is no universal definition of intervertebral instability. Some define it as more than 3.5 mm vertebral listhesis and more than 11 degrees of intervertebral ROM [21], whereas others define it as more than 2 mm of vertebral listhesis [13,19]. Previous reports showed that the C4-5 level is the most common in anterior listhesis, ranging between 36–50% of cases [1, 11,13]. Both postoperative sagittal alignment and vertebral listhesis were affected by curvature of the lower cervical spine (C5-7) [14]. Interestingly, preoperative
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S. Ebata et al. / Postoperative intervertebral stabilizing effect after cervical laminoplasty
intervertebral instability has been strongly related to the onset of cervical myelopathy, but there are many studies showing that postoperative listhesis did not result in impairment of surgical outcomes, postoperative cervical alignment, or reduced ROM [7,8,10,14]. Our study demonstrated that long rest with a cervical orthosis resulted in stabilization of vertebral listhesis and multiple intervertebral unions. However, short rest did not show progression of listhesis or impairment of surgical outcomes. Therefore short rest treatment is not related to negative postoperative surgical outcomes. In addition, we found C4-5 was rarely fused, but commonly produced vertebral listhesis. C2-3 was the most common level for intervertebral fusion, and C6-7 was the least common for vertebral listhesis. We speculate that the mechanism for this relates to the anatomical structure, as C4-5 is at the apex of the cervical lordosis. Following any kind of laminoplasty, postoperative cervical ROM is reduced to almost 60% compared with preoperative ROM following three months of postoperative rest [6,8,9]. Limitation of anterior flexion spares the cervical spinal cord from compression, resulting in satisfactory surgical outcomes [11,14,17]. However, many physicians choose relatively short rest periods, raising the concern that the maintenance of cervical ROM would lead to impairment of surgical outcomes. However, our work shows there is no marked impairment of surgical outcomes following postoperative treatment of rest with use of an orthosis. This study confirmed our previous study that axial pain and complaints related to cervical motion are significantly less in groups with a shorter rest period (Group C vs. Groups A or B) [3]. Intervertebral fusion was obtained in two years at C3-4, 4-5, 5-6, 6-7 levels and in three years at the C2-3 level when postoperative rest for 3 to 4 weeks was selected [8]. Thus we must observe patients suffering from cervical spondylotic myelopathy for much longer periods to reveal when intervertebral fusion is complete or whether listhesis has progressed postoperatively. Based on our current study, we demonstrated that a relatively short rest period post-operatively resulted in maintenance of cervical ROM and reduction in complications such as axial neck pain, and did not change the incidence of the onset of listhesis or the tendency of vertebral listhesis to progress. However, there are several limitations to the current study, including patient selection that occurred long ago. Thus, we have continued this research to prospectively elucidate the relationships between postoperative rest and cervical spinal function, ADL, and pain.
5. Conclusion We classified our patients into three groups and assigned them to post-operative treatment of different durations (8, 4, or 2 weeks) of cervical rest with an orthosis. We measured pain, intervertebral fusion, vertebral listhesis, and range of motion. Postoperatively, a short rest period showed no marked difference in surgical outcomes in groups with longer rest periods by JOA score, but decreased the tendency for both axial neck pain and intervertebral fusion, and maintained ROM of the cervical spine. In addition, the short postoperative treatment did not result in impairment of intervertebral instability.
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