Assessing the sagittal alignment of the cervical

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1 See the editorial in this issue, pp J Neurosurg Spine 11: , 2009 Cervical spondylotic myelopathy associated with kyphosis or sagittal sigmoid alignment: outcome after anterior or posterior decompression Clinical article *Ke n z o Uc h i d a, M.D., Ph.D., Hi d e a k i Na k a j i m a, M.D., Ph.D., Ry u i c h i r o Sa t o, M.D., Ph.D., Ta k a f u m i Yaya m a, M.D., Ph.D., Er i sa S. Mw a k a, M.D., M.Me d., Sh i g e r u Ko b aya s h i, M.D., Ph.D., a n d Hi s a t o s h i Ba b a, M.D., Ph.D. Department of Orthopaedics and Rehabilitation Medicine, Fukui University Faculty of Medical Sciences, Eiheiji, Fukui, Japan Object. The effects of sagittal kyphotic deformities or mechanical stress on the development of cervical spondylotic myelopathy, or the reduction and fusion of kyphotic sagittal alignment have not been consistently documented. The aim in this study was to determine the effects of kyphotic sagittal alignment of the cervical spine in terms of neurological morbidity and outcome after 2 types of surgical intervention. Methods. The authors retrospectively reviewed the records of 476 patients who underwent cervical spine surgeries for spondylotic myelopathy between 1993 and 2006 at their university medical center. Among these were identified 43 patients 30 men and 13 women, with a mean age of 58.8 years who had cervical kyphosis exceeding 10 on preoperative sagittal lateral radiographs obtained in the neutral position, and their cases were analyzed in this study. Anterior decompression with interbody fusion was conducted in 28 patients, and en bloc open-door C3 7 laminoplasty in 15 patients. Both pre- and postoperative neurological, radiographic, and MR imaging findings were assessed in both surgical groups. Results. The mean preoperative kyphotic angle in all 43 patients was 15.9 ± 5.9 in the neutral position. Segmental instability was noted in 26 patients (61%) and reversed dynamic spinal canal stenosis at the level above the local kyphosis in 22 (51%). Preoperative T2-weighted MR images showed high-intensity signal within the cord at and around the level of maximal compression or segmental instability in 28 patients (65%). The mean kyphotic angle in both the neutral and flexion positions was significantly smaller at 4 6 weeks after surgery in the anterior spondylectomy group than in the laminoplasty group (p < 0.001). Furthermore, the angle in the neutral position was significantly smaller on follow-up in the anterior spondylectomy group than in the laminoplasty group (p = 0.034). The transverse area of the spinal cord was significantly larger in the anterior spondylectomy group than in the laminoplasty group on follow-up (p = 0.037). Preoperative neurological scores (assessed using the Japanese Orthopaedic Association scale) and improvement on follow-up 2 years after treatment (average 3.3 years) were not significantly different between the 2 groups; however, there was a significant difference in Japanese Orthopaedic Association score at 4 6 weeks postoperatively (p = 0.047). Conclusions. Kyphotic deformity and mechanical stress in the cervical spine may play an important role in neurological dysfunction. In a select group of patients with kyphotic deformity 10, adequate correction of local sagittal alignment may help to maximize the chance of neurological improvement. (DOI: / SPINE08385) Ke y Wo r d s kyphosis sagittal alignment cervical spondylosis myelopathy comparative study Assessing the sagittal alignment of the cervical spinal column is essential when a patient is amenable to neurosurgical treatment for cervical compressive myelopathy. The kyphotic deformity associated with cervical spondylosis is the result of progressive Abbreviations used in this paper: CSM = cervical spondylotic myelopathy; JOA = Japanese Orthopaedic Association. * Drs. Uchida and Nakajima contributed equally to this work. subluxation of the apophyseal joints due to degenerative changes in the facet joints and discs. 30,35,39 In patients with kyphotic deformities, the spinal cord shifts to the anterior portion of the spinal canal and abuts the posterior aspect of the vertebral bodies at the apex of the deformity. 2 With the progression of kyphosis, the mechanical stress applied to the anterior aspect of the spinal cord eventually increases. 27 In addition, dynamic forces caused by segmental instability, which is often seen at the level J Neurosurg: Spine / Volume 11 / November

2 K. Uchida et al. of kyphosis particularly in cervical flexion movement, contribute to compromised cord function. 6,7,11,15,25,35,38 Although cervical myelopathy could develop as a result of spinal cord compression with or without deformity, the effects of sagittal kyphotic deformities or mechanical stress on the development of CSM, or the reduction and fusion of kyphotic sagittal alignment has not been consistently documented. 20,26 The optimal surgical procedure for CSM associated with sagittal kyphotic alignment remains controversial. It may be theoretically appropriate to reduce the excessive kyphosis and maintain its sagittal alignment within the physiologically permissible flexural tension zone. 37 Admittedly, each anterior route surgery or laminoplasty has advantages and disadvantages. Segmental and kyphotic instability in association with vertebral slippage anteriorly or posteriorly following anterior fusion 6,7 could be the cause of neurological recurrence. Furthermore, poor spinal cord posterior migration and expansion, which were closely associated with poor neurological improvement after laminoplasty, have been reported in patients with kyphotic alignment. 8,9 Since 1998, based on our observations and experience, 3 9 we have favored anterior spondylectomy and fusion to maintain kyphosis-reduced alignment in patients with kyphotic deformity. In the context of clinical practice, since the main purpose of surgery is to attain optimal neurological improvement, both anterior spondylectomy and laminoplasty have been used at our institution under certain strategic guidelines and a consistent clinical background. The present study was designed to investigate the effects of sagittal kyphotic deformities on the development of CSM and to compare the neurological improvement and radiological changes after anterior spondylectomy and laminoplasty. Based on our findings, we discuss the pros and cons of both surgical options for multisegmental CSM associated with kyphotic and/or sigmoid sagittal alignment. TABLE 1: Japanese Orthopaedic Association scoring system for the assessment of cervical myelopathy* Category Score (point) I. Motor function of the upper extremity unable to eat with either chopsticks or a fork 0 able to eat with a fork, but not with chopsticks 1 able to eat with chopsticks, but inadequately 2 able to eat with chopsticks, but awkwardly 3 normal 4 II. Motor function of the lower extremity unable to walk 0 needs a cane or other walking aid on flat ground 1 needs walking aid only on stairs 2 able to walk unaided, but slowly 3 normal 4 III. Sensory function A) Upper extremity apparent sensory disturbance 0 minimal sensory disturbance 1 normal 2 B) Lower extremity apparent sensory disturbance 0 minimal sensory disturbance 1 normal 2 C) Trunk apparent sensory disturbance 0 minimal sensory disturbance 1 normal 2 IV. Bladder function urinary retention or incontinence 0 severe dysuria (sense of retention) 1 slight dysuria (pollakiuria, retardation) 2 normal 3 * Japanese Orthopaedic Association, Category I is modified from the original scoring system. The score in a healthy patient is the total of the best scores: (I + II + III + IV) = 17 points. Methods Patients and Surgeries We retrospectively reviewed the records of 476 patients who underwent cervical spine surgeries for spondylotic myelopathy or radiculopathy between 1993 and 2006 at our university medical center. Among these patients, we identified 43 patients (30 men and 13 women) who had cervical kyphosis exceeding 10 on preoperative sagittal lateral radiographs obtained in the neutral position, and their cases were analyzed in this study. Patients with kyphotic deformities caused by spinal injury, vertebral tumors, infection, or congenital disorders were not included in this study. The average age at surgery was 58.8 years (range years). Anterior decompression and interbody fusion were performed in 28 patients (1-vertebra subtotal spondylectomy in 17 patients, 2-vertebrae spondylectomy in 8, and 3-vertebrae spondylectomy in 3), and anterior plate fixation was performed in 5 of these patients. On the other hand, en bloc open-door C3 7 laminoplasty with unilateral foraminotomy was performed in 15 patients. In anterior decompression, the apex vertebra(e) involved in kyphosis was primarily resected along with often unstable adjacent disc level(s). After spondylectomy of 1 3 vertebrae, sagittal alignment of the cervical spine was corrected with meticulous attention by using a Caspar distractor or a pillow placed posterior to the scapula, followed by trapezoidal iliac bone grafting to maintain the kyphosis-reduced alignment. In cases with a narrow spinal canal (anteroposterior diameter of the neural canal 12 mm at the C4 6 levels), laminoplasty was the primary surgical option. The surgical indications and techniques have been described previously, 3 9 and the senior author (H.B.) performed all surgeries using uniform techniques. The neurological status of each patient was assessed according to the JOA scoring system (Table 1), 19 and the 522 J Neurosurg: Spine / Volume 11 / November 2009

3 Cervical myelopathy with kyphotic alignment Fig. 1. Preoperative lateral radiographs of the cervical spine obtained in the neutral position, showing representative alignment of 3 types of kyphotic deformities with a kyphosis angle > 10, through C-2 to C-7: kyphosis (A), sigmoid type (B), and reversed sigmoid type (C). postoperative neurological improvement rate was calculated using the following formula: (postoperative JOA score preoperative JOA score) 100/(17 preoperative JOA score). Patients were followed-up for 2 years (average follow-up 3.3 years, range 2 7 years). The study protocol was approved by the ethics review committee of our university medical faculty, and written informed consent was obtained from all patients. Radiological Assessment Patients showed a multitude of kyphotic deformities, which for the purposes of this study were divided into kyphosis (20 patients), sigmoid type (13 patients), and reversed sigmoid type (10 patients; Fig. 1). We measured the kyphotic angle on lateral radiographs obtained in the neutral and flexion positions, which was represented by the angle (θ) between the 2 lines at the posterior margin of the most cranial and caudal vertebral bodies forming maximal kyphosis through C-2 to C-7 (Fig. 2) before and after surgery. The following 3 values were considered as the major factors contributing to segmental instability: 5 7,37 1) anterior spondylolisthesis (anterior vertebral translation 3 mm in the sagittal plane); 2) vertebral slip angle (anterior rotation 10 in the sagittal plane); 3) reversed dynamic spinal canal stenosis (the distance between the posterior superior edge of the vertebral body and the anterior edge of the lamina 1 segment above, in the flexion position 12 mm on a flexion film). Segmental instability was defined as when > 2 of the above features were observed preoperatively. At the level of the kyphotic apex and its vicinity, often showing segmental instability, we assessed the transverse area of the spinal cord and intramedullary signal changes on MR images (1.5-T Signa, General Electric). Fig. 2. Illustrations demonstrating radiographic measurements of the cervical spine in kyphosis and segmental instability. A: Kyphosis (the angle [θ] between the 2 lines at the posterior margin of the most cranial and caudal vertebral bodies forming the maximal kyphosis through C-2 to C-7 is > 10 ) in the neutral and flexion positions. B: Anterior spondylolisthesis (anterior vertebral translation 3 mm in the sagittal plane) and vertebral slip angle (anterior rotation 10 in the sagittal plane) in the flexion position. C: Reversed dynamic spinal canal stenosis (distance between the posterior superior edge of the vertebral body and the anterior edge of the lamina 1 segment above is 12 mm) in the flexion position. J Neurosurg: Spine / Volume 11 / November

4 K. Uchida et al. We measured the transverse area of the spinal cord at the level of severest impingement by the compressive lesion on transaxial T1-weighted MR images (TR 350 msec, TE 19 msec), both preoperatively and on follow-up. The measurement of the transverse area of the spinal cord was conducted directly on images converted from the stored MR imaging data by using NIH imaging software (version 1.59, Ohlandorf Research). 8 Intramedullary signalintensity changes on sagittal T2-weighted sequences (TR 4000 msec, TE 98 msec) were serially monitored. 34 Statistical Analysis Neurological and radiographic assessments were performed by observers independent of the principal surgeon. Data were collected and then analyzed using the StatView 5 program (SAS Institute). Data are expressed as the means ± SD. The Pearson correlation analysis was applied to assess the relationship between radiological factors and neurological score. Differences between the 2 groups were statistically evaluated using the Mann- Whitney U-test. A p < 0.05 indicated the presence of a statistically significant difference. Results Correlation Between Radiological Findings and Neurological Data The mean preoperative kyphotic angle of all 43 patients was 15.9 ± 5.9 in the neutral position and 18.7 ± 10.4 in the flexion position. Among all patients, 26 (60.5%) had segmental instability at the upper (24 patients) and lower (2 patients) levels of maximal local kyphosis. These 26 patients showed kyphosis (5 patients), sigmoid-type abnormality (14 patients), and reversed sigmoid-type deformity (7 patients). Twenty-two patients (51%) showed reversed dynamic spinal canal stenosis at the adjacent level above the maximal local kyphosis: kyphosis in 5 patients, sigmoid-type in 11, and reversed sigmoid-type in 6. On T2-weighted preoperative MR images, 28 patients (65.1%) exhibited iso- to hyperintense signals within the cord at and around the level of the maximal compressive lesion or segmental instability. There was no significant correlation between the preoperative kyphotic angle and preoperative JOA score (p = 0.116), between the preoperative kyphotic angle and preoperative transverse area of the spinal cord (p = 0.207), or between the preoperative kyphotic angle and presence of high-intensity signals within the cord (p = 0.342). Neurological Outcomes Following Anterior Spondylectomy and Laminoplasty There were no significant differences between the 2 treatment groups in terms of age (p = 0.80), duration of disease (p = 0.87), preoperative JOA score (p = 0.55), preoperative kyphotic angle (p = 0.067), presence of highsignal intensity on MR imaging (p = 0.80), and duration of follow-up period (p = 0.95). Neurological JOA scores at 4 6 weeks after surgeries were significantly high in the anterior spondylectomy TABLE 2: Neurological outcome for anterior spondylectomy and laminoplasty* Parameter Anterior Spondylectomy Laminoplasty p Value preop JOA score 11.6 ± ± postop (4 6 weeks) JOA score 14.7 ± ± follow-up JOA score 14.5 ± ± ne urological improvement rate at follow-up (%) 67.5 ± ± * Data expressed as the means ± SD. Mann-Whitney U-test. group (p = 0.047) compared with those in the laminoplasty group, but the difference became insignificant (p = 0.29) at the follow-up (Table 2). Radiographic Findings in Anterior Spondylectomy and Laminoplasty Groups The mean kyphotic angle at both neutral and flexion positions was significantly smaller at 4 6 weeks after surgery in the anterior spondylectomy group than in the laminoplasty group (p < 0.001). Furthermore, the angle at the neutral position was significantly smaller on follow-up in the anterior spondylectomy group than in the laminoplasty group (p = 0.034). The transverse area of the spinal cord was significantly larger in the anterior spondylectomy group than in the laminoplasty group (p = 0.037; Table 3). The kyphotic angle tended to decrease on follow-up in the laminoplasty group, although this change was not significant. Figure 3 shows typical cases of anterior spondylectomy, and Fig. 4 shows a case of expansive open-door laminoplasty. Treatment Complications In 2 patients who underwent anterior plate fixation, loose screws were observed on follow-up, although they were causing no problems. Transient motor weakness of the deltoid muscles developed in 2 patients who had undergone laminoplasty, but spontaneous recovery of the palsy was noted within 6 months. Discussion Loss of lordosis or kyphotic alignment of the cervical spine and spinal cord may contribute to the development of myelopathy, 8,9 and in patients with cervical kyphotic deformity, the spinal cord could be compressed by tethering over the apical vertebra or intervertebral disc or by ossification of the posterior longitudinal ligament. 16 Longitudinal distraction is a possible factor in progressive spinal cord dysfunction, and this issue is often discussed clinically in the pathophysiology of tethered spinal cord syndrome and tight dural tube mechanism. 18,24,36 In a previous animal study, 21 we reported that artificial distraction of C-1 and C-7 resulted in the disappearance 524 J Neurosurg: Spine / Volume 11 / November 2009

5 Cervical myelopathy with kyphotic alignment TABLE 3: Radiological outcome for anterior spondylectomy and laminoplasty Parameter preop kyphotic angle ( ) neutral position flexion position po stop (4 6 weeks) kyphotic angle ( ) neutral position flexion position follow-up kyphotic angle ( ) neutral position flexion position pr eop transverse area of spinal cord (mm 2 ) fo llow-up transverse area of spinal cord (mm 2 ) 17.0 ± ± ± ± 3.8 Anterior Spondylectomy Laminoplasty 15.6 ± ± ± ± 4.2 p Value* <0.001 < ± ± ± ± ± ± ± ± * Mann-Whitney U-test. of spinal cord evoked potentials especially at the midcord segment, suggesting that distraction stress in humans is mostly concentrated at the C-4 and C-5 levels that is, at the same site where kyphosis and/or local angulatory deformity is frequent, as seen in the present series of patients. Thus, even when the entire spinal cord is longitudinally distracted, injury of the anterior horn and the pyramidal tracts induced by such mechanical distraction stress will be significant. In the present study, there was a high frequency of segmental instability (61%), including anterior spondylolisthesis and/or vertebral slip angle, together with coexisting reversed dynamic spinal canal stenosis (51%), as compared with our previous radiographic data on CSM with or without deformity (14 and 10%, respectively). 34 In their microvascular study, Breig and El-Nadi 12 demonstrated that cervical flexion produces flattening of the small feeding vessels. If the kyphotic deformity continues, there may be progression of myelomalacia and spinal cord atrophy. Patients with long-standing kyphotic deformities are at risk for progression of myelopathy with resultant permanent damage to the spinal cord. White and Panjabi 37 have demonstrated that the application of distraction stress to the spinal cord longitudinally during flexion leads to more significant impingement on the anterior part of the cord by the anterior compressive lesion (for example, spondylotic osteophyte or vertebral bodies) than the posterior part. Our results suggest that flexion mechanical stress caused by segmental instability could also contribute to the development of myelopathy and neurological dysfunction when the CSM associated with static compression has more than 10 kyphosis in the cervical spine. The relationship between sagittal alignment and spinal cord function has not been consistently documented in clinical and statistical studies. A previous clinical study demonstrated no relationship between cervical myelopa- J Neurosurg: Spine / Volume 11 / November 2009 Fig. 3. Images obtained in a 66-year-old man with severe cervical myelopathy (JOA Score 10 points). Anterior decompression with interbody fusion (C5 6 subtotal spondylectomy) using an anterior cervical plate was performed. The patient gained a 5-point increase in the JOA score on follow-up (rate of neurological improvement 71%). Preoperative lateral plain radiograph (A) showing that the patient had a kyphotictype cervical spine alignment (preoperative kyphotic angle 12 ). Postoperative lateral plain radiograph (B) showing some correction of the cervical spine alignment (postoperative kyphotic angle 4 ). Preoperative sagittal MR image (C) demonstrating compression of the dural tube and kyphotic alignment of the spinal cord from the C-4/5 to C-6/7 levels. Postoperative sagittal MR image (D) revealing decompression and anterior shift of the spinal cord. Preoperative (E) and postoperative (F) axial MR images obtained at C5 6, indicating a transverse area of the cord of 55 mm 2 preoperatively and 83 mm 2 on follow-up. 525

6 K. Uchida et al. Fig. 4. Images obtained in a 58-year-old man with cervical myelopathy (JOA Score 12 points). En bloc C3 7 open-door type laminoplasty with foraminotomy was performed. The patient gained a 3-point increase in his JOA score on follow-up (rate of neurological improvement 60%). Preoperative lateral plain radiograph (A) showing a kyphotic type cervical spine alignment (preoperative kyphotic angle 18 ). Postoperative lateral plain radiograph (B) showing some correction of cervical spine alignment (postoperative kyphotic angle 8 ). Preoperative sagittal MR image (C) demonstrating compression of the dural tube at multiple levels. Postoperative sagittal MR image (D) revealing decompression and a posterior shift of the spinal cord. Preoperative (E) and postoperative (F) axial MR images at C4 5 are shown. The transverse area of the cord was 61 mm 2 preoperatively and 76 mm 2 at follow-up. thy and the degree of kyphosis 17 or between the preoperative JOA core and preoperative spinal cord alignment. Similarly, in the present study, there was no significant correlation between the preoperative kyphotic angle and preoperative JOA score or between the preoperative transverse area of the spinal cord and the presence of highintensity signals within the cord. Hence, it is difficult to preoperatively demonstrate the correlation between the development and severity of myelopathy caused by this distraction stress and the degree of kyphosis in each patient with cervical myelopathy given that many factors including age, duration of symptoms, irreversible changes in the spinal cord, and static and dynamic canal stenosis including segmental instability could affect the myelopathy, neurological dysfunction, and surgical outcome. 34 Both anterior route surgery and laminoplasty have certain postoperative disadvantages for multisegmental CSM with kyphosis. We previously analyzed 106 patients who underwent anterior fusion, and found 6 patients (5%) in whom there was a neurological recurrence due to progression of kyphosis > In another study, we examined 56 patients with spondylotic myelopathy, including kyphotic sagittal alignment, who underwent laminoplasty. Sixteen patients (29%) showed reduced lordotic alignment, and 9 patients (16%) with preoperative kyphosis (kyphotic angle range , average 11.7 ) had significantly poor neurological improvement after surgery. 7 Based on our experience, anterior spondylectomy and fusion have been applied since 1998 at our institution in patients with multisegmental CSM with kyphosis. In our spondylectomy technique, we perform a more gentle and smaller correction of kyphosis (average ~ 7.8 ) on followup compared with other research groups. 1,17,28 Although maintaining normal cervical anatomy with its lordosis can optimize cord function and the anterior aspect of the cord can be protected from contact by correction surgery, the correction of a kyphotic deformity has not been consistently shown to improve myelopathy, and the benefits of such correction remain obscure. 20,39 Note, however, that in the anterior spondylectomy group in the present study, the mean kyphotic angle was smaller on follow-up, and there was a significant difference in the transverse area of the spinal cord between the anterior spondylectomy group and laminoplasty group. Direct compression of the myelopathic spinal cord could be associated with a variable rate of functional recovery and morphological restoration of the spinal cord in part due to ongoing compression, a bowstring effect with tension in the cord, or dynamic factors affecting the cord blood supply and metabolism. 10,33 Although conventional expansive open-door laminoplasty has proven to be a useful treatment for multisegmental compressive myelopathy, 8,9,13 the procedure in a patient with kyphosis or neutrally aligned spinal column will not allow posterior translation of the spinal cord away from an anterior compressive abnormality. 9,23,31 In this regard, Suda et al. 32 have estimated the maximal preoperative local kyphotic angle for successful expansive laminoplasty to be < 13, as calculated with the multivariate logistic regression model. In the present study of CSM with preoperative kyphosis > 10 (mean 16 ), however, there was no significant difference in the JOA scores (p = 0.29) and neurological improvement at the final follow-up (p = 0.10) between the anterior spondylectomy and laminoplasty groups. Although the exact reason for this finding is not clear at present, we speculate that a slack in the spinal cord could induce a postoperative reduction in disc height in patients with multiple-level CSM, especially elderly 526 J Neurosurg: Spine / Volume 11 / November 2009

7 Cervical myelopathy with kyphotic alignment patients. According to Chiba et al., 14 this slack should allow acceptable recovery following posterior compression, even in the context of a kyphotic spine. With regard to changes in sagittal alignment following laminoplasty, Kawai 22 has described some reduction in lordotic alignment in ~ 30% of patients treated with laminoplasty. In a preliminary study, we also observed deterioration of sagittal alignment in 12 (26%) of 47 patients. Data in the present study demonstrated that cervical kyphosis was not only maintained, but also diminished by ~ 2.4 on follow-up. Furthermore, the kyphotic angle in the flexion position also decreased at the follow-up. The postoperative changes may be partly due to improved and facilitated neck rehabilitation, but more importantly the results indicate that the operative technique influences the back muscles as well as the cervical spine. Reduced movement after laminoplasty may also be an expedient solution to the instability. 7,29 Conclusions We conclude that the sagittal kyphotic deformity related to flexion mechanical stress may be a significant factor in the development of CSM. It is difficult to consider the kyphosis and flexion mechanism as distinct causes, but it is suggested that increased longitudinal stress seems to be closely associated with the resultant increase in the anterior compressive effect on the spinal cord. Although the present study should be regarded as preliminary in nature because of the retrospective study design and the small numbers of patients, in a select group of patients with kyphotic deformity 10, a reduction of local sagittal alignment may assist in maximizing the chances of recovering spinal cord function. Disclaimer The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. Acknowledgments This work was supported in part by grants ( ) from the Investigation Committee on Ossification of the Spinal Ligaments, Public Health Bureau of the Japanese Ministry of Health and Welfare, and by Grants-in-Aid (Nos , , and ) for General Scientific Research of the Japanese Ministry of Education, Science and Culture. References J Neurosurg: Spine / Volume 11 / November Abumi K, Kaneda K, Shono Y, Fujiya M: One-stage posterior decompression and reconstruction of the cervical spine by using pedicle screw fixation systems. J Neurosurg 90 (1 Suppl):19 26, Albert TJ, Vacarro A: Postlaminectomy kyphosis. Spine 23: , Baba H, Chen Q, Uchida K, Imura S, Morikawa S, Tomita K: Laminoplasty with foraminotomy for coexisting cervical myelopathy and unilateral radiculopathy: a preliminary report. Spine 21: , Baba H, Furusawa N, Chen Q, Imura S, Tomita K: Anterior decompressive surgery for cervical ossified posterior longitudinal ligament causing myeloradiculopathy. 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