Clinical and Radiological Characteristics of Cervical Spondylotic Myelopathy in Young Adults: A Retrospective Case Series of Patients under Age 30.

Background and Objectives: Cervical spondylotic myelopathy (CSM) is a degenerative disease and occurs more frequently with age. In fact, the development of non-herniated CSM under age 30 is uncommon. Therefore, a retrospective case series was designed to clarify clinical and radiological characteristics of young adult patients with CSM under age 30. Materials and Methods: A total of seven patients, all men, with non-herniated, degenerative CSM under age 30 were retrieved from the medical records of 2598 hospitalized CSM patients (0.27%). Patient demographics and backgrounds were assessed. The sagittal alignment, congenital canal stenosis, dynamic canal stenosis, and vertebral slips in the cervical spine were radiographically evaluated. The presence of degenerative discs, intramedullary high-signal intensity lesions, and sagittal spinal cord compression on T2-weighted magnetic resonance images (MRIs) and axial spinal cord deformity on T1-weighted MRIs was identified. Results: All patients (100.0%) had relatively high daily sports activities and/or jobs requiring frequent neck extension. Cervical spine radiographs revealed the sagittal alignment as the "reverse-sigmoid" type in 57.1% of patients and "straight" type in 28.6%. All patients (100.0%) presented congenital cervical stenosis with the canal diameter ≤12 mm and/or Torg-Pavlov ratio <0.80. Furthermore, all patients (100.0%) developed dynamic stenosis with the canal diameter ≤12 mm and/or posterior vertebral slip ≥2 mm at the neurologically responsible segment in full-extension position. In MRI examination, all discs at the neurologically responsible level (100.0%) were degenerative. Intramedullary abnormal intensity lesions were detected in 85.7% of patients, which were all at the neurologically responsible disc level. Conclusions: Patients with non-herniated, degenerative CSM under age 30 are rare but more common in men with mild sagittal "reverse-sigmoid" or "straight" deformity and congenital canal stenosis. Relatively high daily activities, accumulating neck stress, can cause an early development of intervertebral disc degeneration and dynamic canal stenosis, leading to CSM in young adults.

Spinal Subarachnoid Hematoma After Cerebrospinal Fluid Drainage in Thoracoabdominal Aortic Aneurysm Repair: Case Report and Literature Review.

BACKGROUND: Cerebrospinal fluid (CSF) drainage reduces the risk of paraplegia in thoracoabdominal aortic aneurysm (TAAA) repair. Intracranial hemorrhage after TAAA repair has been reported as a rare complication of CSF drainage; however, spinal subarachnoid hematoma has never been reported. Here, we present a case of lumbosacral subarachnoid hematoma after CSF drainage in TAAA repair. CASE DESCRIPTION: The patient was a 76-year-old man who was hospitalized for TAAA repair. Just before the operation, a CSF drainage catheter was inserted into the L4/5 vertebral interspace. Continuous CSF drainage was performed during the operation. The CSF drain was clamped just after the operation, and the drainage catheters were removed at 24 hours after the operation. On postoperative day 1, the patient experienced pain and paralysis in both lower limbs that worsened over time. Magnetic resonance imaging of the brain and spinal cord was indicative of a spinal subarachnoid hematoma. Removal of hematoma with thoracolumbar and lumbosacral laminectomy was performed, and immediately after the surgery, the pain and paralysis in both lower limbs improved. Six months after the removal of the hematoma, the paralysis in both lower limbs completely resolved and the patient achieved the preinjury activity level. CONCLUSIONS: We present a rare case of lumbosacral subarachnoid hematoma after CSF drainage in TAAA repair. We should consider spinal subarachnoid hematoma when paralysis in the lower limbs occurs after CSF drainage.

The factors of deterioration in long-term clinical course of lumbar spinal canal stenosis after successful conservative treatment.

BACKGROUND: The treatment of lumbar spinal canal stenosis (LSS) depends on symptom severity. In the absence of severe symptoms such as severe motor disturbances or bowel and/or urinary dysfunction, conservative treatment is generally the first choice for the treatment of LSS. However, we experienced cases of worsening symptoms even after successful conservative treatment. The purpose of this study is to investigate the long-term clinical course of LSS following successful conservative treatment and analyze the prognostic factors associated with symptom deterioration. METHODS: The study included 60 LSS patients (34 females and 26 males) whose symptoms were relieved by conservative treatment between April 2007 and March 2010 and who were followed up for 5 years or longer. The mean age at admission was 64.8 ± 8.5 years (range, 40-85 years old), and the mean follow-up period was 7.3 years (range, 5.8-9.5 years). We defined "deterioration" of symptoms as the shortening of intermittent claudication more than 50 m compared with those at discharge or the occurrence or progression of lower limb paralysis, and "poor outcome" as the deterioration within 5 years after discharge. The long-term outcome of conservative treatment for LSS was analyzed by Kaplan-Meier analysis. Furthermore, logistic regression analysis was performed to reveal the risk factors of poor outcome for clinical classification, severe intermittent claudication (≤ 100 m), lower limb muscle weakness, vertebral body slip (≥ 3 mm), scoliosis (Cobb angle ≥ 10°), block on myelography, and redundant nerve roots of the cauda equina. RESULTS: Thirty-four (56.7%) patients preserved their condition at discharge during the follow-up, whereas 26 patients (43.3%) showed deterioration. Sixteen patients had a decreased intermittent claudication distance, and 10 patients had newly developed or progressive paralysis. The probability of preservation was maintained at 68.3% at 5 years after discharge. Logistic regression analysis demonstrated that only severe intermittent claudication (≤ 100 m) was a significant risk factor of a poor outcome (p = 0.005, odds ratio = 6.665). CONCLUSIONS: The patients with severe intermittent claudication should be carefully followed up because those are the significant deterioration candidates despite the success in conservative treatment.

Postoperative Walking Ability of Non-ambulatory Cervical Myelopathy Patients.

STUDY DESIGN: A retrospective analysis. OBJECTIVE: The aim of this study was to clarify the postoperative improvement of walking ability and prognostic factors in nonambulatory patients with cervical myelopathy. SUMMARY OF BACKGROUND DATA: Many researchers have reported the surgical outcome in compressive cervical myelopathy. However, regarding severe gait disturbance,, it has not been clarified yet how much improvement can be expected. METHODS: One hundred thirty-one nonambulatory patients with cervical myelopathy were treated surgically and followed for an average of 3 years. Walking ability was graded according to the lower-extremity function subscore (L/E subscore) in Japanese Orthopedic Association score. We divided patients based on preoperative L/E subscores: group A, L/E subscore of 1 point (71 patients); and group B, 0 or 0.5 point (60 patients). The postoperative walking ability was graded by L/E subscore: excellent, ≥2 points; good, 1.5 points; fair, 1 point; and poor, 0.5 or 0 points. We compared preoperative and postoperative scores. The cutoff value of disease duration providing excellent improvement was investigated. RESULTS: Overall, 50 patients were graded as excellent (38.2%), and 21 patients were graded as good (16.0%). In group B, 17 patients (28.3%) were graded as excellent. Seventeen patients who were graded as excellent had shorter durations of myelopathic symptoms and/or gait disturbance (7.9 and 3.8 months respectively) than the others (29.5 and 8.9 months, respectively) (P < 0.05). Receiver-operating characteristic curve showed that the optimal cutoff values of the duration of myelopathic symptoms and gait disturbance providing excellent improvement were 3 and 2 months, respectively. CONCLUSION: Even if the patients were nonambulatory, 28.3% of them became able to walk without support after operation. If a patient becomes nonambulatory within 3 months from the onset of myelopathy or 2 months from the onset of gait disturbance, surgical treatment should be performed immediately to raise the possibility to improve stable gait. LEVEL OF EVIDENCE: 3.

Dysphagia After Occipitothoracic Fusion is Caused by Direct Compression of Oropharyngeal Space Due to Anterior Protrusion of Mid-cervical Spine.

STUDY DESIGN: This was a retrospective study. OBJECTIVE: To investigate the relationship among the craniocervical alignment, the oropharyngeal space, and the incidence of dysphagia after occipitothoracic fusion (OTF). SUMMARY OF BACKGROUND DATA: Craniocervical malalignment after OTF is one of a trigger of dysphagia. However, there has been no logical explanation for the etiology yet. METHODS: A total of 32 patients who underwent OTF (5 male, 27 female) were reviewed. Following 4 parameters on the lateral cervical radiogram, pharyngeal tilt angle (PTA); the angle between the McGregor's line and the line that links the center of C2 pedicle and the center of vertebral body at the apex of cervical sagittal curvature, diameter of oropharyngeal airway space (dPS), O-C2 angle, and C2-C7 angle were measured at follow-up and then the relationship of these parameters and their influence to the incidence of dysphagia were analyzed. RESULTS: Six of 32 cases (18.8%) exhibited postoperative dysphagia. ROC curves showed that PTA and dPS had moderate accuracy for the predictor of the dysphagia after OTF with the area under the curve (AUC) of 0.76 and 0.86 respectively, whereas O-C2 angle had low accuracy with AUC of 0.69 and C2-C7 angle was almost useless for prediction of postoperative dysphagia with AUC of 0.51. A multiple linear regression analysis showed that only PTA was significantly correlated with dPS (ß=0.822, P=0.014), whereas the O-C2 angle (ß=0.101, P=0.779) and C2-C7 angle (ß=0.352, P=0.157) had negligibly small influence on dPS. CONCLUSIONS: Our results demonstrated strong relationships between PTA and the value of dPS, and the incidence of dysphagia. As PTA reflects anterior protrusion of mid-cervical spine, these results indicated that dysphagia after OTF is caused by narrowing of oropharyngeal space due to direct compression from anteirorly protruded mid-cervical spine.

The Prediction and Prevention of Dysphagia After Occipitospinal Fusion by Use of the S-line (Swallowing Line).

STUDY DESIGN: Clinical case series and risk factor analysis of dysphagia after occipitospinal fusion (OSF). OBJECTIVE: The aim of this study was to develop new criteria to avoid postoperative dysphagia by analyzing the relationship among the craniocervical alignment, the oropharyngeal space, and the incidence of dysphagia after OSF. SUMMARY OF BACKGROUND DATA: Craniocervical malalignment after OSF is considered to be one of the primary triggers of postoperative dysphagia. However, ideal craniocervical alignment has not been confirmed. METHODS: Thirty-eight patients were included. We measured the O-C2 angle (O-C2A) and the pharyngeal inlet angle (PIA) on the lateral cervical radiogram at follow-up. PIA is defined as the angle between McGregor's line and the line that links the center of the C1 anterior arch and the apex of cervical sagittal curvature. The impact of these two parameters on the diameter of pharyngeal airway space (PAS) and the incidence of the dysphagia were analyzed. RESULTS: Six of 38 cases (15.8%) exhibited the dysphagia. A multiple regression analysis showed that PIA was significantly correlated with PAS (ß = 0.714, P = 0.005). Receiver-operating characteristic curves showed that PIA had a high accuracy as a predictor of the dysphagia with an AUC (area under the curve) of 0.90. Cases with a PIA less than 90 degrees showed significantly higher incidence of dysphagia (31.6%) than those with a 90 or more degrees of PIA (0.0%) (P = 0.008). CONCLUSION: Our results indicated that PIA had the high possibility to predict postoperative dysphagia by OSF with the condition of PIA <90°. Based on these results, we defined "Swallowing-line (S-line)" for the reference of 90° of PIA. S-line (-) is defined as PIA <90°, where the apex of cervical lordosis protruded anterior to the "S-line," which should indicate the patient is at a risk of postoperative dysphagia. LEVEL OF EVIDENCE: 4.

Preliminary Evaluation of the Pathomechanisms of Dysphagia After Occipitospinal Fusion: Kinematic Analysis by Videofluoroscopic Swallowing Study.

STUDY DESIGN: Kinematic analysis of swallowing function using videofluoroscopic swallowing study (VFSS). OBJECTIVES: The aims of this study were to analyze swallowing process in the patients who underwent occipitospinal fusion (OSF) and elucidate the pathomechanism of dysphagia after OSF. SUMMARY OF BACKGROUND DATA: Although several hypotheses about the pathomechanisms of dysphagia after OSF were suggested, there has been little tangible evidence to support these hypotheses since these hypotheses were based on the analysis of static radiogram or CT. Considering that swallowing is a compositive motion of oropharyngeal structures, the etiology of postoperative dysphagia should be investigated through kinematic approaches. METHODS: Each four patients with or without postoperative dysphagia (group D and N, respectively) participated in this study. For VFSS, all patients were monitored to swallow 5-mL diluted barium solution by fluoroscopy, and then dynamic passing pattern of the barium solution was analyzed. Additionally, O-C2 angle (O-C2A) was measured for the assessment of craniocervical alignment. RESULTS: O-C2A in group D was -7.5 degrees, which was relatively smaller than 10.3 degrees in group N (P = 0.07). In group D, all cases presented smooth medium passing without any obstruction at the upper cervical level regardless of O-C2A, whereas the obstruction to the passage of medium was detected at the apex of mid-lower cervical ocurvature, where the anterior protrusion of mid-lower cervical spine compressed directly the pharyngeal space. In group N, all cases showed smooth passing of medium through the whole process of swallowing. CONCLUSION: This study presented that postoperative dysphagia did not occur at the upper cervical level even though there was smaller angle of O-C2A and demonstrated the narrowing of the oropharyngeal space towing to direct compression by the anterior protrusion of mid-lower cervical spine was the etiology of dysphagia after OSF. Therefore, surgeon should pay attention to the alignment of mid-cervical spine as well as craniocervical junction during OSF. LEVEL OF EVIDENCE: 4.

Intimate relationship between instability and degenerative signs at L4/5 segment examined by flexion-extension radiography.

Relationship between lumbar disc degeneration and segmental instability has remained controversial. Using instability factors that found close relations with symptoms in flexion-extension radiographic study, their relationship with degenerative findings was examined. More than (≥) 3 mm slip in neutral position (SN), ≥3 mm translation (ST), and ≥10° angulation (SA) at L4/5 segment were defined as instability factors and were applied on 447 patients who had low back and/or leg pain and satisfied inclusion criteria for accurate measurements. Radiologic findings for degeneration were disc height including three groups with different disc heights divided by mean ± 1 standard deviation, length of the anterior spur formation, presence of vacuum phenomenon, and endplate sclerosis. As results, group with SN factor was the oldest in age and the lowest in disc height; in contrast, group with SA was the youngest in age and the highest in disc height. The group with ST showed a mid-standing position in both age and disc height. These findings indicate that instability factors are intimately related to age and disc height. The three different disc height groups showed more anterior slip according to the progression of the disc height diminution. Presence of the apparent spur formation and/or vacuum phenomenon had an intimate relationship with the ST factor. Disc height was the most important in the examined parameters and showed an intimate relationship with age and instability factors. Although the etiology is still unknown, clinical common knowledge, that a diminution of disc height with progressive degeneration had a close relation with anterior vertebral slippage, was firstly confirmed. This study allows comprehensive understanding of segmental instability and is useful for considering surgical indications.

Prospective study and multivariate analysis of the incidence of C5 palsy after cervical laminoplasty.

STUDY DESIGN: A prospective comparative study about the incidence of postoperative C5 palsy and multivariate analysis of the risk factors of C5 palsy. OBJECTIVE: To clarify the risk factors of occurrence of C5 palsy after laminoplasty (LP) by comparing the 2 surgical procedures of open-door and double-door LP prospectively. SUMMARY OF BACKGROUND DATA: The incidence of C5 palsy has been reported to average 4.6%, and there has been no difference of the incidence among surgical procedures. However, there were only indirect retrospective studies. METHODS: A total of 146 patients who underwent the LP procedure between 2006 and 2007 were studied prospectively. In 2006, the patients were assigned to undergo the open-door LP, and in 2007, they were assigned to undergo the double-door LP. The incidence of postoperative C5 palsy was compared prospectively between these 2 LP procedures, and the risk factors of C5 palsy were detected with multivariate logistic regression analysis. RESULTS: Postoperative C5 palsy occurred in 7 of 73 cases after open-door LP (9.6%) and in 1 of 73 cases after double-door LP (1.4%). The incidence of C5 palsy after open-door LP was statistically higher than the one after double-door LP (P = 0.029), and open-door LP was recognized as a significant risk factor for postoperative C5 paralysis (odds ratio: 69.6, P = 0.043). In addition, ossification of posterior longitudinal ligament (OPLL) was recognized as a significant risk factor for postoperative C5 paralysis (odds ratio: 43.8, P = 0.048). CONCLUSION: This study showed significant evidence indicating the higher risk of postoperative C5 palsy in open-door LP than double-door LP. Because OPLL as well as open-door LP were recognized as the risk factors of C5 palsy, asymmetric decompression by open-door LP might introduce imbalanced rotational movement of spinal cord and result in C5 palsy. We recommend double-door LP to minimize the postoperative C5 palsy, in particularly, if the patient has OPLL.

The vanishment of an intramedullary high-signal intensity lesion at the craniocervical junction after surgical treatment: a case report of the presyrinx state.

STUDY DESIGN: A case report of the presyrinx state at the craniocervical junction with vanishment of an intramedullary high-signal lesion followed by decompression and fixation. OBJECTIVE: To report the reversible change of an intramedullary high-signal lesion on T2-weighted MRI as a presyrinx state. SUMMARY OF BACKGROUND DATA: The pathology of a T2-weighted high-signal intensity area in the spinal cord has not yet been described in detail. The case presented here showed the vanishment of this lesion after the surgical procedure, which implies that some high-signal intensity lesions might be reversible as a presyrinx state. METHODS: A 75-year-old man presented with severe cervical myelopathy. Neurologic findings and observations on various images indicated compression myelopathy due to both a pseudotumor at the craniocervical junction and spondylosis at C3-C4 disc level due to Klippel-Feil syndrome. The most obvious finding was a vast high-signal intensity lesion at the craniocervical junction, which was speculated to be a syringomyelia before surgery. RESULTS: The MRI at 1 month after surgical treatment (occipito-spinal fusion with the decompression by enlargement of foramen magnum) revealed complete vanishment of the vast high intensity lesion at the craniocervical junction, which remained undetected at the 2 years and 8 months follow-up and corresponded with improvement in the clinical symptoms of myelopathy. CONCLUSION: The vanishment of these signal changes on MRI after surgery was interpreted as a presyrinx state, demonstrating this reversible pathology in the spinal cord.

The influence of sagittal instability factors on clinical lumbar spinal symptoms.

STUDY DESIGN: Cross-sectional and prospective study. OBJECTIVE: To find the critical order of 3 radiographic factors observed in standing flexion-extension films and to discover their combined effect on lumbar symptoms. SUMMARY OF BACKGROUND DATA: Many previous reports have described relationships between degenerative change in the lumbar disc and segmental instability; however, few reports have attempted to show any relationship between instability and symptoms. Little is known about which type of instability is the most critical in the sagittal plane of the lumbar spine. METHODS: Excessive segmental motion (factors): >3 mm slip, >3 mm translation, and >10 degrees angulation, at the L4/5 segment in 880 patients (389 men and 491 women; mean age, 49.4 y) with low back and/or leg pain were investigated at initial visit. Symptoms of low back and leg pain, and walking ability were evaluated at initial visit and 4.6-year follow-up using Japanese Orthopaedic Association's scoring system. Severity and continuity of symptoms were evaluated and compared among the groups according to various combinations of excessive motion. RESULTS: Of the 3 factors, patients with >3 mm slip had the lowest scores, and patients with >10 degrees angulation had the highest, both at initial visit and follow-up (P<0.001). In the comparative study of various factors, the groups with >3 mm slip had significantly lower scores than the group with no factors, and these groups had significantly lower scores in leg pain and walking ability than the nonfactor group (P<0.05). CONCLUSIONS: Of the 3 factors, >3 mm slip had the strongest effect on symptoms followed by >3 mm translation and then >10 degrees angulation. Therefore, patients with low back and/or leg pain at initial visit and >3 mm slip, may expect symptoms of a duration exceeding 4 years. More than 10 degrees angulation had the least effect on symptoms as shown by the similarity in scores with the nonfactor group.

Delayed dural laceration by hydroxyapatite spacer causing tetraparesis following double-door laminoplasty.

OBJECT: The authors describe 4 cases of delayed dural laceration by hydroxyapatite (HA) spacer causing tetra-paresis following double-door laminoplasty. There are few reports of iatrogenic spinal cord lesions developing after double-door laminoplasty, although some complications such as postoperative C-5 paralysis or axial symptoms have been reported. The purpose of this report is to draw attention to the possibility of delayed dural laceration and its triggering mechanism. METHODS: One hundred thirty patients treated for cervical myelopathy were followed up for an average of 2 years and 9 months after laminoplasty. RESULTS: Four patients experienced aggravation of cervical myelopathy. Anterior dislodgement of HA spacers was shown on plain lateral radiographs. Follow-up T2-weighted magnetic resonance imaging demonstrated that the dislodged HA spacers were surrounded by cerebrospinal fluid at the time of aggravation. The dislodged HA spacers were removed and the dural membrane defects were repaired by patching with the fascia of the gluteus maximus muscle. The preoperative symptoms improved after the second operation in all patients. CONCLUSIONS: It is hypothesized that the loosening of the HA spacer in split spinous processes could occur with the movement of the cervical spine and/or the breakage of the suture before bone bonding. Anterior dislodgement of the HA spacer toward the spinal canal would cause dural laceration by direct friction between the dural membrane and the dislodged HA spacer, resulting in clinical aggravation. Despite the well-documented advantages of using HA spacers for double-door laminoplasty, possible laceration due to a dislodged HA spacer should be considered as a late complication.

Lumbar instability and clinical symptoms: which is the more critical factor for symptoms: sagittal translation or segment angulation?

BACKGROUND: The relationship between radiologic instability and its symptoms is controversial. Previous authors consider flexion-extension radiographs to be of little value in evaluating instability; however, the current authors consider the variation of results in evaluating radiologic instability to be the result of limitations in previous researchers' methods. METHODS: In this report, sagittal translation and angulation at the L4-L5 segment were measured in flexion-extension films in 1,090 outpatients with low back and/or leg pain using a three-landmark measuring method. The symptoms of four groups with and without 3-mm translation and with and without 10 degrees angulation were compared for all the patients and for 280 age-matched patients using a scoring system. The age-matched patients were followed up for 4.6 years. RESULTS: Results showed that patients with > or = 3-mm translation had significantly lower scores, indicating a limitation in their daily activities due to pain, than patients < 3-mm translation; however, no difference was observed between the groups in terms of angulation. The group with > or = 3-mm translation and > or = 10 degrees angulation significantly demonstrated the lowest scores at both evaluations during the initial visit and follow-up. This group had been suffering from low back and/or leg pain the longest and had visited the hospital significantly more often than other groups. CONCLUSION: In conclusion, translation of the lumbar segment has a greater influence than angulation on lumbar symptoms. The presence of both radiologic factors could be an indicator for persistence of the symptoms.

Age distribution of three radiologic factors for lumbar instability: probable aging process of the instability with disc degeneration.

STUDY DESIGN: Cross-sectional study of 880 outpatients with low back and/or leg pain regarding age distribution of three radiologic factors. OBJECTIVES: To investigate the proportion and relationship of three individual radiologic factors with age on segmental instability in sagittal plane in consecutive age groups. SUMMARY OF BACKGROUND DATA: Previous studies revealed relationships between radiologic factors for instability and symptoms; however, little is known about the relationship between factors and age except in degenerative spondylolisthesis. METHODS: Excessive segmental motion, defined as more than 10 degrees angulation, more than 3 mm translation, and more than 3 mm slip in neutral position, at the L4-L5 segment in 880 outpatients (389 men, 491 women) with low back and/or leg pain aged from 14 to 84 years was investigated by 3 observers. The number and rate of the patients with each excessive motion were evaluated in continuous age groups of 5 years. RESULTS: The mean ages of patients with excessive angulation, translation, and slip in neutral position were 41.7, 50.0, and 62.8 years, respectively. Both rates of excessive angulation and translation showed two peak patterns demonstrating peaks in the teens and 20s groups and in the over 46 age groups; however, angulation was predominant in younger age groups and translation was predominant in older age groups. Slip in neutral position was frequently observed in age groups over 46 and increased with age. CONCLUSIONS: The presence of patients with excessive angulation and translation in younger age groups suggests they have a hypermobile segment with least degenerated discs. Different predominant patterns of these radiologic factors may reveal the probable aging process of the instability.

Cervical laminoplasty: evaluation of bone bonding of a high porosity hydroxyapatite spacer.

OBJECT: The purpose of this study was to evaluate the usefulness of a high-porosity hydroxyapatite (HA) spacer in cervical laminoplasty. Bone-spacer bonding rates, complications associated with the implant, and factors related to bone bonding were examined. METHODS: The authors evaluated 33 consecutive patients with cervical myelopathy who underwent high-porosity HA spacer-assisted laminoplasty and were followed for at least 1 year (mean 30 months). The results of bone-spacer bonding of the 147 implants were evaluated using computerized tomography (CT) scanning. The symptoms significantly improved in 30 patients. No difference in results was detected between patients with cervical spondylosis and those with ossification of posterior longitudinal ligament. Breakage of seven spacers occurred in four patients without causing neck pain or neurological deficits. There were no other HA spacer-related complications. The spacers became rigidly bound to bone in 61% of the cases, and bone regrowth developed around the spacer in 91%. The rate of bone-spacer bonding increased over time, and the CT-documented attenuation value (Hounsfield unit) of the spacer adjacent to the bone-spacer junction in the group in which union occurred was significantly higher than in the nonunion group. CONCLUSIONS: High-porosity HA spacer-augmented laminoplasty produced good bonding-related results. Bone bonding continued to progress 1 year after surgery, indicating the good osteoconductive capability of high-porosity HA. To avoid breakage of a spacer, a minimum 7-mm distance between spacers is necessary.