Cervical ossification of the posterior longitudinal ligament: Biomechanical analysis of the influence of static and dynamic factors.

OBJECTIVE: Cervical myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is induced by static factors, dynamic factors, or a combination of both. We used a three-dimensional finite element method (3D-FEM) to analyze the stress distributions in the cervical spinal cord under static compression, dynamic compression, or a combination of both in the context of OPLL. METHODS: Experimental conditions were established for the 3D-FEM spinal cord, lamina, and hill-shaped OPLL. To simulate static compression of the spinal cord, anterior compression at 10, 20, and 30% of the anterior-posterior diameter of the spinal cord was applied by the OPLL. To simulate dynamic compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction. To simulate combined static and dynamic compression under 10 and 20% anterior static compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction. RESULTS: The stress distribution in the spinal cord increased following static and dynamic compression by cervical OPLL. However, the stress distribution did not increase throughout the entire spinal cord. For combined static and dynamic compression, the stress distribution increased as the static compression increased, even for a mild range of motion (ROM). CONCLUSION: Symptoms may appear under static or dynamic compression only. However, under static compression, the stress distribution increases with the ROM of the responsible level and this makes it very likely that symptoms will worsen. We conclude that cervical OPLL myelopathy is induced by static factors, dynamic factors, and a combination of both.

Biomechanical analysis of cervical spondylotic myelopathy: the influence of dynamic factors and morphometry of the spinal cord.

OBJECTIVE: Patients with cervical spondylotic myelopathy (CSM) have the same clinical symptoms that vary according to the degree of spinal cord compression and the cross-sectional cord shape. We used a three-dimensional finite element method (3D-FEM) to analyze the stress distributions of the spinal cord with neck extension under three cross-sectional cord shapes. METHODS: Experimental condition for the 3D-FEM spinal cord, ligamentum flavum, and anterior compression shape (central, lateral, and diffuse types) was established. To simulate neck extension, the spinal cord was extended by 20° and the ligamentum flavum was shifted distally according to movement of the cephalad lamina. RESULTS: The stress distribution in the spinal cord increased due to invagination of the ligamentum flavum into the neck extension. The range of stress distribution observed for the diffuse type was wider than for the central and lateral types. In addition, the stress distribution in the spinal cord was increased by the pincer movement of the ligamentum flavum and by the anterior compression of the spinal cord. The range of stress distribution observed for the diffuse type under antero-posterior compression was also wider than for the central and lateral types. CONCLUSION: This simulation model showed that the clinical symptoms of CSM due to compression of the diffuse type may be stronger than for the central and lateral types. Therefore, careful follow-up is recommended for anterior compression of the spinal cord of diffuse type.

Development of less invasive neuromuscular electrical stimulation model for motor therapy in rodents.

BACKGROUND: Combination therapy is essential for functional repairs of the spinal cord. Rehabilitative therapy can be considered as the key for reorganizing the nervous system after spinal cord regeneration therapy. Functional electrical stimulation has been used as a neuroprosthesis in quadriplegia and can be used for providing rehabilitative therapy to tap the capability for central nervous system reorganization after spinal cord regeneration therapy. OBJECTIVE: To develop a less invasive muscular electrical stimulation model capable of being combined with spinal cord regeneration therapy especially for motor therapy in the acute stage after spinal cord injury. METHODS: The tibialis anterior and gastrocnemius motor points were identified in intact anesthetized adult female Fischer rats, and stimulation needle electrodes were percutaneously inserted into these points. Threshold currents for visual twitches were obtained upon stimulation using pulses of 75 or 8 kHz for 200 ms. Biphasic pulse widths of 20, 40, 80, 100, 300, and 500 µs per phase were used to determine strength-duration curves. Using these parameters and previously obtained locomotor electromyogram data, stimulations were performed on bilateral joint muscle pairs to produce reciprocal flexion/extension movements of the ankle for 15 minutes while three-dimensional joint kinematics were assessed. RESULTS: Rhythmic muscular electrical stimulation with needle electrodes was successfully done, but decreased range of motion (ROM) over time. High-frequency and high-amplitude stimulation was also shown to be effective in alleviating decreases in ROM due to muscle fatigue. CONCLUSIONS: This model will be useful for investigating the ability of rhythmic muscular electrical stimulation therapy to promote motor recovery, in addition to the efficacy of combining treatments with spinal cord regeneration therapy after spinal cord injuries.

Biomechanical study of the spinal cord in thoracic ossification of the posterior longitudinal ligament.

BACKGROUND: Ossification of the posterior longitudinal ligament (OPLL) in the thoracic spine produces myelopathy. This is often progressive and is not affected by conservative treatment. Therefore, decompressive surgery is usually chosen. OBJECTIVE: To conduct a stress analysis of the thoracic OPLL. METHODS: The three-dimensional finite element spinal cord model was established. We used local ossification angle (LOA) for the degree of compression of spinal cord. LOA was the medial angle at the intersection between a line from the superior posterior margin at the cranial vertebral body of maximum OPLL to the top of OPLL with beak type, and a line from the lower posterior margin at the caudal vertebral body of the maximum OPLL to the top of OPLL with beak type. LOA 20°, LOA 25°, and LOA 30° compression was applied to the spinal cord in a preoperative model, the posterior decompressive model, and a model for the development of kyphosis. RESULTS: In a preoperative model, at more than LOA 20° compression, high stress distributions in the spinal cord were observed. In a posterior decompressive model, the stresses were lower than in the preoperative model. In the model for development of kyphosis, high-stress distributions were observed in the spinal cord at more than LOA 20° compression. CONCLUSIONS: Posterior decompression was an effective operative method. However, when the preoperative LOA is more than 20°, it is very likely that symptoms will worsen. If operation is performed at greater than LOA 20°, then correction of kyphosis by fixation of instruments or by forward decompression should be considered.

Transplantation of neurospheres derived from bone marrow stromal cells promotes neurological recovery in rats with spinal cord injury.

Previous studies have revealed that cell therapy using bone marrow stromal cells (BMSCs) could promote motor functional recovery in animals with spinal cord injury (SCI). We describe here the development of cell biology technique and the experimental study of regeneration in SCI. The aim of this study was to investigate the potential for neurological recovery by transplantation neurospheres (NS) derived from BMSCs into thoracic SCI. Adult Fisher rats were used: 45 were subjected to complete thoracic SCI performed by the balloon compression method. BMSCs were cultured in vitro to obtain NS. Seven days after thoracic SCI, groups of 15 rats each received transplants of BMSCs-NS (group A), BMSCs (group B), or injection of medium only (group C) into the SCI lesion. Rats from each group were evaluated and compared longitudinally for motor function recovery. The spinal cords (SC) of injured rats were harvested at day 21 or day 42 and prepared for histological analysis. Five weeks after transplantation, many neuronal or axonal sproutings were observed and replaced by host cells in the SCI lesion of group A. Also, transplanted BMSCs-NS expressed neuronal lineage markers. Transplanted rats could walk with weight bearing and showed recovered motor evoked potentials (MEPs).

Etiology of cervical myelopathy induced by ossification of the posterior longitudinal ligament: determining the responsible level of OPLL myelopathy by correlating static compression and dynamic factors.

STUDY DESIGN: Retrospective study. OBJECTIVE: To determine the responsible level of cervical myelopathy induced by ossification of the posterior longitudinal ligament (OPLL). This was achieved by correlating the intervertebral range of motion (ROM) as the dynamic factor with the space available for spinal cord (SAC) as the static compression factor. SUMMARY OF BACKGROUND DATA: The association between spinal canal stenosis and the occurrence of the myelopathy has previously been reported for OPLL patients, but not the detailed relationship between SAC, ROM, and myelopathy. METHODS: We investigated OPLL type, SAC, and ROM in relation to the responsible level of cervical OPLL myelopathy in 27 cases. SAC and ROM were measured at each vertebral and intervertebral levels. The responsible level was diagnosed using spinal cord-evoked potentials and classified as group A, whereas the nonresponsible level was classified as group B. RESULTS: Spinal cord-evoked potentials revealed 21 cases with a single responsible level and 6 cases with 2 responsible levels. The mean ROM of group A (8.9 degrees) was significantly higher (P<0.01) than that of group B (5.7 degrees). The mean SAC of group A (8.2 mm) was significantly lower (P<0.01) than that of group B (12.4 mm). Using discriminate analysis, significant differences for both SAC and ROM were observed between groups A and B [Box's M test: chi=3.31

Selective laminoplasty after the preoperative diagnosis of the responsible level using spinal cord evoked potentials in elderly patients with cervical spondylotic myelopathy: a preliminary report.

STUDY DESIGN: A preliminary report of a new operative method termed selective laminoplasty after the preoperative diagnosis of the responsible level using spinal cord evoked potentials (SCEPs) in elderly patients with cervical spondylotic myelopathy. OBJECTIVE: To introduce the method and clinical results for selective laminoplasty. SUMMARY OF BACKGROUND DATA: Clinical results for conventional laminoplasty and anterior decompression and fusion guided by SCEPs have been reported. However, there have been no reports that consider SCEP results for selecting the optimal level in lamioplasty for cervical spondylotic myelopathy. METHODS: Seven elderly patients who underwent selective laminoplasty were followed for a minimum of 12 months. The T2-high-intensity area on magnetic resonance imaging, the responsible level detected by SCEPs, and the laminoplasty level were recorded. The operative time, intraoperative bleeding, clinical results including the Japanese Orthopaedic Association score, recovery rate, Nurick grading scale, and visual analog scale of axial pain were investigated preoperatively and postoperatively. RESULTS: The responsible intervertebral levels were at C3-C4 in 3 patients and at C4-C5 in 4 patients. These were identical for SCEP recorded after median nerve stimulation and transcranial electric stimulation. High-intensity area on T2-weighted magnetic resonance imaging was seen in 6 patients (3 at C3-C4 and 3 at C4-C5). The average operative time was 106 minutes and the average amount of bleeding was 20 mL. Neurologic recovery was achieved in all patients except 1 who had severe myelopathy. Visual analog scales of axial pain were 41.3 + or - 33.9 before surgery and 18.0 + or - 19.4 at final follow-up. The Japanese Orthopaedic Association score and the Nurick grade improved in 6 patients but did not change in 1 patient. CONCLUSIONS: Preliminary clinical results for selective laminoplasty were satisfactory in all but 1 case. Although long-term results are not yet available, we consider this method to be less invasive and capable of giving satisfactory clinical results and benefits for elderly patients.

Flexion model simulating spinal cord injury without radiographic abnormality in patients with ossification of the longitudinal ligament: the influence of flexion speed on the cervical spine.

BACKGROUND/OBJECTIVE: It is suspected that the speed of the motion of the spinal cord under static compression may be the cause of spinal cord injury (SCI). However, little is known about the relationship between the speed of the motion of the spinal cord and its stress distributions. The objective was to carry out a biomechanical study of SCI in patients with ossification of the longitudinal ligament without radiologic evidence of injury. METHODS: A 3-dimensional finite element spinal cord model was established. After the application of static compression, the model underwent anterior flexion to simulate SCI in ossification of the longitudinal ligament patients without radiologic abnormality. Flexion of the spine was assumed to occur at 1 motor segment. Flexion angle was 5 degrees, and flexion speeds were 0.5 degrees/s, 5 degrees/s, and 50 degrees/s. Stress distributions inside of the spinal cord were evaluated. RESULTS: Stresses on the spinal cord increased slightly after the application of 5 degrees of flexion at a speed of 0.5 degrees/s. Stresses became much higher at a speed of 5 degrees/s and increased further at 50 degrees s. CONCLUSIONS: The stress distribution of the spinal cord under static compression increased with faster flexion speed of the spinal cord. High-speed motion of the spinal cord under static compression may be one of the causes of SCI in the absence of radiologic abnormality.

Validation study of a clinical diagnosis support tool for lumbar spinal stenosis.

BACKGROUND: A clinical diagnosis support tool for lumbar spinal stenosis was developed by the Japanese Society for Spine Surgery and Related Research. However, the use of this tool has not yet been validated. METHODS: Patients with symptoms in the lower extremities and who visited the Department of Orthopedics initially were recruited to the study. Orthopedic physicians who were not spine specialists completed the support tools. Spine specialists examined the patients, made a diagnosis, and completed the lumbar spine examination sheet made for the study. The support tool and lumbar spine examination sheet were sent to a central panel comprising four panelists who then decided on a final diagnosis. RESULTS: In total, 118 patients were evaluated, including 62 males and 56 females. Lumbar spinal stenosis was diagnosed in 58 and nonlumbar spinal stenosis in 60 patients. The mean score in the lumbar spinal stenosis group was 12.2 points (median 13 points). In the nonlumbar spinal stenosis group, the mean score was 7.5 points (median 7 points). Sensitivity was 0.948, and specificity was 0.40. CONCLUSIONS: Patients with lumbar spinal stenosis with a very low score were diagnosed with mild lumbar spinal stenosis, whereas nonlumbar spinal stenosis patients with a very high score were diagnosed as suffering from spine disease and needing special treatment by spine surgeons. Our results validate the use of the support tool for the diagnosis of lumbar spinal stenosis. Although the specificity observed in the present study was lower than that reported at development, we conclude that this support tool is useful for screening patients with lumbar spinal stenosis.

Environmental factors involved in axonal regeneration following spinal cord transection in rats.

A recent study of a rat model treated with grafted collagen filament (CF) after spinal cord transection showed dramatic recovery of motor function but did not report on the acute-stage phenomenon. In the present study, we describe molecular and histological aspects of the axonal regeneration process during the acute stage following spinal cord transection. The spinal cord of 8-week-old rats was completely transected, and a scaffold of almost the same size as the resected portion was implanted in the gap. Changes in the mRNA expression of four neurotrophic factors [nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, and glial cell-derived neurotrophic factor (GDNF)] were analyzed after 72 h. The expression of BDNF and NT-3 mRNA increased significantly in the CF-grafted group compared to the nongrafted group. Immunostaining for BDNF and NT-3 revealed that cells positive for these neurotrophic factors extended along the collagen filaments in the CF-grafted group. Similarly, astrocytes extended into the collagen filament scaffold together with the neurotrophic factors and partly across a border line. These findings indicate that collagen filament helps to reduce scar tissue, supports the expression of neurotrophic factors, and serves as a scaffold for the outgrowth of regenerating axons.

Dynamic electrophysiological examination of cervical flexion myelopathy.

Cervical flexion myelopathy is thought to arise following compression of the spinal cord by vertebrae or intervertebral discs and dura mater, or from overstretching of the spinal cord induced by cervical spinal flexion. However, the influence of spinal flexion on the spinal cord and the detailed origins of this disease are unknown. In this article the authors report a case of cervical flexion myelopathy in which dynamic electrophysiological examination was performed using an epidural electrode. This investigation showed the real-time influence of flexion of the cervical spine on spinal cord function. This technique was considered to be useful for diagnosis and in decision making for treatment. Anterior fusion was the optimal surgical method for treating this disease.

Biomechanical study of cervical flexion myelopathy using a three-dimensional finite element method.

OBJECT: The goal of this study was to perform a biomechanical study of cervical flexion myelopathy (CFM) using a finite element method. METHODS: A 3D finite element model of the spinal cord was established consisting of gray matter, white matter, and pia mater. After the application of semi-static compression, the model underwent anterior flexion to simulate CFM. The flexion angles used were 5 degrees and 10 degrees , and stress distributions inside the spinal cord were then evaluated. RESULTS: Stresses on the spinal cord were very low under semi-static compression but increased after 5 degrees of flexion was applied. Stresses were concentrated in the gray matter, especially the anterior and posterior horns. The stresses became much higher after application of 10 degrees of flexion and were observed in the gray matter, posterior funiculus, and a portion of the lateral funiculus. CONCLUSIONS: The 5 degrees model was considered to represent the mild type of CFM. This type corresponds to the cases described in the original report by Hirayama and colleagues. The main symptom of this type of CFM is muscle atrophy and weakness caused by the lesion of the anterior horn. The 10 degrees model was considered to represent a severe type of CFM and was associated with lesions in the posterior fand lateral funiculi. This type of CFM corresponds to the more recently reported clinical cases with combined long tract signs and sensory disturbance.

Warfarin-induced impairment of cortical bone material quality and compensatory adaptation of cortical bone structure to mechanical stimuli.

Long-term warfarin use has been reported to increase fracture risk of rib and vertebra but not hip in elderly patients, but the mechanisms remain unknown. We hypothesized that warfarin would impair bone material quality but could not weaken bone strength under conditions with higher mechanical stimuli. To test this hypothesis, rats were randomized to vehicle or warfarin group at 4 weeks of age and subsequently weight matched into a sedentary or jumping exercise group at 12 weeks of age. At 6 months of age, osteocalcin content, bone mineral density (BMD), mineral size, material properties, morphological parameters, and biomechanical properties of cortical bones were evaluated. In order to seek evidence for a common mechanism of action, effects of nucleation rate of mineral crystals on their rigidity were also investigated using computer simulation. In humeral cortical bones, warfarin did not change BMD, but markedly decreased osteocalcin content, diminished mineral size, and impaired material hardness. Consistent with these results, our computer-simulation model showed that osteocalcin-induced delay of mineral crystal nucleation decreased mineral formation rate, increased mean and distribution of mineral sizes, and strengthened mineral rigidity. In tibial cortical bones, warfarin decreased material ultimate stress; however, under jumping exercise, warfarin increased cross-sectional total and bone areas of these tibiae and completely maintained their biomechanical properties including work to failure. Collectively, our findings suggest that long-term warfarin therapy weakens rib and vertebra by impairing cortical bone material quality due to a marked decrease in osteocalcin content but could not reduce hip strength through compensatory adaptation of cortical bone structure to higher mechanical stimuli.

Cervical ossification of the posterior longitudinal ligament: factors affecting the effect of posterior decompression.

OBJECTIVE: Decompression procedures for cervical myelopathy of ossification of the posterior longitudinal ligament (OPLL) are anterior decompression with fusion, laminoplasty, and posterior decompression with fusion. Preoperative and postoperative stress analyses were performed for compression from hill-shaped cervical OPLL using 3-dimensional finite element method (FEM) spinal cord models. METHODS: Three FEM models of vertebral arch, OPLL, and spinal cord were used to develop preoperative compression models of the spinal cord to which 10%, 20%, and 30% compression was applied; a posterior compression with fusion model of the posteriorly shifted vertebral arch; an advanced kyphosis model following posterior decompression with the spinal cord stretched in the kyphotic direction; and a combined model of advanced kyphosis following posterior decompression and intervertebral mobility. The combined model had discontinuity in the middle of OPLL, assuming the presence of residual intervertebral mobility at the level of maximum cord compression, and the spinal cord was mobile according to flexion of vertebral bodies by 5°, 10°, and 15°. RESULTS: In the preoperative compression model, intraspinal stress increased as compression increased. In the posterior decompression with fusion model, intraspinal stress decreased, but partially persisted under 30% compression. In the advanced kyphosis model, intraspinal stress increased again. As anterior compression was higher, the stress increased more. In the advanced kyphosis + intervertebral mobility model, intraspinal stress increased more than in the only advanced kyphosis model following decompression. Intraspinal stress increased more as intervertebral mobility increased. CONCLUSION: In high residual compression or instability after posterior decompression, anterior decompression with fusion or posterior decompression with instrumented fusion should be considered.

CT-Guided Intranodal Lymphangiography for Postoperative Chylous Ascites.

The utility and minimal invasiveness of ultrasound-guided intranodal lymphangiography have already been reported by several researchers. Although ultrasound-guided intranodal lymphangiography is known to be not technically difficult in general, a patient's edematous groin due to hypoalbuminemia resulting from chylous ascites made it too challenging to detect and prick the lymph nodes precisely. This report describes a 71-year-old female with refractory chylous ascites due to an operation for an extrahepatic bile duct cancer, who was successfully treated by computed tomography (CT)-guided intranodal lymphangiography. After switching from ultrasound- to CT-guided lymphangiography, the procedure was successfully performed, and the refractory chylous ascites was treated.

Epidurally recorded spinal cord evoked potentials in patients with cervical myelopathy and normal central motor conduction time measured by transcranial magnetic stimulation.

OBJECTIVE: Use epidural recording of evoked spinal cord potentials (ESCPs) to investigate the pathology of cervical spondylotic myelopathy (CSM) in patients with normal central motor conduction time (CMCT) in upper and lower limbs. METHODS: A total of 75 patients with CSM were studied. All patients were examined before surgery for motor evoked potentials (MEPs) following transcranial magnetic stimulation (TMS). They were also evaluated during surgery by epidurally recorded ESCPs following stimulation of the median nerve, brain and spine. RESULTS: Seven patients (9%) showed normal CMCT in upper and lower limbs upon TMS examination. Only the ESCPs following median nerve stimulation (MN-ESCPs) were abnormal in these patients. In 5 of the 7 patients, a marked block in conduction of MN-ESCPs was observed at the C3-4 intervertebral level. The remaining two patients showed attenuation in the amplitude of MN-ESCPs at mid-cervical levels. CONCLUSIONS: We present 7 cases of CSM with negative CMCT findings. From the MN-ESCP results, we surmise that the pathology of CSM with normal CMCT is due predominantly to dysfunction of sensory systems involved in the upper limbs. SIGNIFICANCE: Examination by TMS is useful in the diagnosis of CSM but the possibility of negative CMCT findings upon TMS must be borne in mind. Multi-functional evoked spinal cord responses demonstrate that lesions in the sensory system are the major underlying pathology.

A case of an anaplastic meningioma metastasizing to the mediastinal lymph nodes.

CONTEXT: Grade II and III (World Health Organization classification) meningiomas rarely develop in the spinal cord. However, we experienced a case with an anaplastic meningioma that developed in the spinal cord at the cervicothoracic junction and metastasized to the mediastinal lymph nodes. No such cases have previously been reported. FINDINGS: The patient was a 68-year-old man who developed back pain that did not affect his daily living. He developed left lower limb paralysis, and was admitted after magnetic resonance imaging (MRI) revealed an intramedullary tumor at the level of cervical vertebra 7 and thoracic vertebra 1. Positron emission tomography revealed tracer uptake in the intramedullary tumor and the mediastinal lymph nodes, suggesting a metastatic spinal cord tumor or malignant lymphoma. A lymph node biopsy was then performed. Although the tumor was highly malignant, its primary site was not identified. Detailed examinations by several other departments revealed no abnormalities. On hospital day 30, his left lower limb paralysis deteriorated, and MRI revealed that the tumor had grown. Thus, laminaplasty, laminectomy, and tumor resection were performed. The tumor was an anaplastic meningioma that resembled mediastinal lymph node tissue, and other tumor lesions were not found. These findings suggested that an anaplastic meningioma had metastasized to the mediastinal lymph nodes. The patient did not respond to radiotherapy, and he was transferred to another hospital. CONCLUSION: In cases of intramedullary spinal tumors with metastasis without other potential primary tumor lesions, early diagnosis and treatment should be performed while considering anaplastic meningioma.

Stress analysis of the cervical spinal cord: Impact of the morphology of spinal cord segments on stress.

OBJECTIVE: Although there are several classifications for cervical myelopathy, these do not take differences between spinal cord segments into account. Moreover, there has been no report of stress analyses for individual segments to date. METHODS: By using the finite element method, we constructed 3-dimensional spinal cord models comprised of gray matter, white matter, and pia mater of the second to eighth cervical vertebrae (C2-C8). We placed compression components (disc and yellow ligament) at the front and back of these models, and applied compression to the posterior section covering 10%, 20%, 30%, or 40% of the anteroposterior diameter of each cervical spinal cord segment. RESULTS: Our results revealed that, under compression applied to an area covering 10%, 20%, or 30% of the anteroposterior diameter of the cervical spinal cord segment, sites of increased stress varied depending on the morphology of each cervical spinal cord segment. Under 40% compression, stress was increased in the gray matter, lateral funiculus, and posterior funiculus of all spinal cord segments, and stress differences between the segments were smaller. CONCLUSION: These results indicate that, under moderate compression, sites of increased stress vary depending on the morphology of each spinal cord segment or the shape of compression components, and also that the variability of symptoms may depend on the direction of compression. However, under severe compression, the differences among the cervical spinal segments are smaller, which may facilitate diagnosis.

Biomechanical analysis of cervical myelopathy due to ossification of the posterior longitudinal ligament: Effects of posterior decompression and kyphosis following decompression.

Cervical ossification of the posterior longitudinal ligament (OPLL) results in myelopathy. Conservative treatment is usually ineffective, thus, surgical treatment is required. One of the reasons for the poor surgical outcome following laminoplasty for cervical OPLL is kyphosis. In the present study, a 3-dimensional finite element method (3D-FEM) was used to analyze the stress distribution in preoperative, posterior decompression and kyphosis models of OPLL. The 3D-FEM spinal cord model established in this study consisted of gray and white matter, as well as pia mater. For the preoperative model, 30% anterior static compression was applied to OPLL. For the posterior decompression model, the lamina was shifted backwards and for the kyphosis model, the spinal cord was studied at 10, 20, 30, 40 and 50° kyphosis. In the preoperative model, high stress distributions were observed in the spinal cord. In the posterior decompression model, stresses were lower than those observed in the preoperative model. In the kyphosis model, an increase in the angle of kyphosis resulted in augmented stress on the spinal cord. Therefore, the results of the present study indicated that posterior decompression was effective, but stress distribution increased with the progression of kyphosis. In cases where kyphosis progresses following surgery, detailed follow-ups are required in case the symptoms worsen.

Prediction of surgical outcome for proximal-type cervical spondylotic amyotrophy novel mode of assessment using compound action potentials of deltoid and biceps brachii and central motor conduction time.

STUDY DESIGN: Case studies of patients with cervical spondylotic amyotrophy used compound muscle action potentials (CMAPs) of deltoid and biceps brachii muscles and central motor conduction time (CMCT). OBJECTIVE: To discuss surgical outcome for proximal-type cervical spondylotic amyotrophy in the context of results obtained with CMAPs and CMCT. SUMMARY OF BACKGROUND DATA: There have been no reports that correlate surgical outcome with CMAPs of deltoid and biceps brachii muscles or with CMCT. METHODS: A retrospective study was performed for 24 patients with proximal-type cervical spondylotic amyotrophy who underwent surgical treatment of the cervical spine. Erb-point-stimulated CMAPs were recorded in the deltoid and biceps. The percent amplitude of CMAPs was calculated in comparison with the opposite side. Motor-evoked potentials were recorded from bilateral abductor digiti minimi. CMAPs and F waves were recorded after supramaximal electric stimulation of ulnar nerves. CMCT was calculated as follows: motor-evoked potentials latency - (CMAPs' latency + F latency - 1)/2 (ms). Muscle strength was evaluated using manual muscle testing. Improvements in strength were classified as excellent, good, or fair. RESULTS: The improvement was graded as excellent in 12 cases, good in 2 cases, and fair in 10 cases. The average percentage for CMAPs' amplitude on the affected side compared with the normal side in deltoid and biceps brachii muscles was significantly different between the excellent and fair patient groups. The CMCT on the affected side was not significantly different between excellent and fair patient groups. CONCLUSION: The average percentage range of deltoid and biceps brachii muscle CMAPs' amplitude determined at the onset of illness correlated significantly with postoperative recovery. Surgical intervention of the cervical spine should be performed in patients in whom the average percentage of CMAPs' amplitude in deltoid and biceps brachii muscles ranges from 30% to 50%.