Ryutaro Fujii

Kinematics of the subaxial cervical spine in rotation in vivo three-dimensional analysis

Study Design. Kinematics of the upper cervical spine during head rotation were investigated using three-dimensional magnetic resonance imaging (MRI) in healthy volunteers. Objectives. To demonstrate in vivo intervertebral coupled motions of the upper cervical spine. Summary of Background Data. Although various in vivo and in vitro studies have identified the normal movement patterns of the upper cervical spine, no previous studies have accurately analyzed in vivo three-dimensional intervertebral motions of the upper cervical spine during head rotation. Methods. Fifteen healthy volunteers underwent three-dimensional MRI of the upper cervical spine using a 1.0-T imager in progressive 15° steps during head rotation. Segmented three-dimensional MRIs of each vertebra in the neutral position were superimposed over images taken at other positions, using voxel-based registration. Relative motions between occiput (Oc) and atlas (C1) and between C1 and axis (C2) were measured and described with 6 degrees of freedom by rigid body Euler angles and translations. Results. Mean (± SD) maximum angles of axial rotation in Oc–C1 and C1–C2 were 1.7 ± 1.5° and 36.2 ± 4.5° to each side, respectively. Increases in angle of axial rotation in C1–C2 became smaller with increased head rotation, indicating axial rotation in C1–C2 displayed nonlinear motion. Coupled lateral bending with axial rotation was observed in the direction opposition to that of axial rotation in Oc–C1 (mean, 4.1 ± 1.4°) and C1–C2 (mean, 3.8 ± 3.0°). Coupled extension with axial rotation occurred at both C0–C1 (mean, 13.3 ± 4.9°) and C1–C2 (mean, 6.9 ± 3.0°). Conclusions. We developed an innovative in vivo three-dimensional motion analysis system using three-dimensional MRI. In vivo coupled motions of the upper cervical spine investigated using this system supported the results of the previous in vitro study.

Kinematics of the cervical spine in lateral bending: in vivo three-dimensional analysis.

Study Design. Kinematics of the cervical spine during lateral bending were investigated using a novel system of three-dimensional motion analysis. Objectives. To demonstrate in vivo intervertebral coupled motions of the cervical spine during lateral bending of the neck. Summary of Background Data. No previous studies have successfully documented in vivo three-dimensional intervertebral motions of the cervical spine during lateral bending. Methods. Twelve healthy volunteers underwent three-dimensional magnetic resonance imaging (MRI) of the cervical spine in 7 positions with 10° increments of lateral bending. Relative motions of the cervical spine were calculated automatically by superimposing a segmented three-dimensional-MRI of the vertebra in the neutral position over images of each position using volume registration. Results. Mean maximum lateral bending of the cervical spine to one side was 1.6° to 5.7° at each level. Coupled axial rotation opposite to lateral bending was observed in the upper cervical levels (Oc-C1, 0.2°; C1–C2, 17.1°), while in the subaxial cervical levels, it was observed in the same direction as lateral bending except for at C7–T1. Coupled flexion-extension motion was small at all vertebral levels (<1.1°). Conclusions. We succeeded in identifying in vivo coupled motions of the cervical spine in lateral bending for the first time.

C3-6 laminoplasty takes over C3-7 laminoplasty with significantly lower incidence of axial neck pain

Five-lamina (C3-7) procedure is the most popular cervical laminoplasty and there have been no studies on the most appropriate number of laminae to be opened. We prospectively reduced the range of laminoplasty from C3-7 to C3-6 in 2002 and compared the outcome of C3-6 laminoplasty (n=37) to that of C3-7 laminoplasty (n=28). In both groups, neurological gain was satisfactory, radiographic changes were minimal, and postoperative MRI indicated sufficient expansion of the dura and the spinal cord. Average operating period was significantly shorter, and length of the operative wound was significantly less in the C3-6 group than in the C3-7 group. Postoperative axial neck pain was significantly rarer after C3-6 laminoplasty than after C3-7 laminoplasty (5.4% vs. 29%, P=0.015). Due to its simplicity and various benefits, C3-6 laminoplasty is a promising alternative to conventional C3-7 laminoplasty for treatment of multisegmental compression myelopathy.

Kinematics of the lumbar spine in trunk rotation: in vivo three-dimensional analysis using magnetic resonance imaging

In vivo three-dimensional (3D) kinematics of the lumbar spine has not been well evaluated by the conventional methods because of their methodological limitations, while 3D intervertebral motions have been quantitatively determined by cadaver studies. We thus developed a novel 3D analyzing system for the relative motions of individual vertebrae using 3D magnetic resonance imaging (MRI) and analyzed in vivo 3D intervertebral motions of the lumbar spine during trunk rotation. Ten healthy volunteers underwent 3D MRI of the lumbar spine in nine positions with 15° increments during trunk rotation (0°, 15°, 30°, 45°, and maximum). Relative motions of the lumbar spine were calculated by automatically superimposing a segmented 3D MRI of the vertebra in the neutral position over images of each position using the voxel-based registration method. These 3D motions were represented with 6 degrees of freedom by Euler angles and translations on the coordinate system. The mean axial rotation of ten healthy volunteers of each lumbar spinal segment in 45° trunk rotation to each side ranged from 1.2° to 1.7°. Coupled flexion with axial rotation was observed at the segments from L1/2 to L5/S1. Coupled lateral bending of the segments from L1/2 to L4/5 was in the opposite direction of the trunk rotation, while that of T12/L1 and L5/S1 was in the same direction. The direction of the coupled lateral bending in the present study was different from that in the previous cadaver study only at L4/5. This difference might result from the non-load state of the supine position in the current study and/or the non-physiological state in the cadaver study. Our system has two limitations: (1) the study was conducted with each volunteer in the supine position, and (2) because the rotation device regulated trunk rotation, trunk rotation might not have been physiological. In vivo 3D intervertebral motions of the lumbar spine during trunk rotation were evaluated using our novel motion analysis system. These data may be useful for the optimal orthopaedic management of lumbar spinal disorders.

Segmental Motor Paralysis After Cervical Laminoplasty : A Prospective Study

Study Design. A prospective study. Objective. To examine the prevalence and clinical manifestations of segmental motor paralysis after cervical laminoplasty and to investigate the presence of intramedullary high-signal intensity area (HIA) on postoperative T2-weighted magnetic resonance imaging (MRI). Summary of Background Data. Almost all previous studies had been retrospectively conducted, and MRIs of all subjects, including a control population, have never been investigated. Methods. In the 79 patients of the prospective group, the sole examiner evaluated muscle strengths daily for perioperative 3 weeks and MRI scans were performed before and after surgery. Medical records of the 79 consecutive patients before this study were also investigated (control group). Results. Ten patients from the prospective group developed segmental motor paralysis (proximal in 5, distal in 2, and diffuse in 3), whereas paralysis occurred in only 4 patients from the control group (proximal in 3 and diffuse in 1). On postoperative MRI, a linear HIA corresponded to the paralyzed segment more frequently than a focal or no HIA. Conclusion. In the prospective cases, distal or diffuse paralysis was found more frequently than in the retrospective control group. Linear HIAs were significantly more likely to present in the paralyzed segments.

Repeated vertebrobasilar thromboembolism in a patient with severe upper cervical instability because of rheumatoid arthritis

BACKGROUND CONTEXT Although many reports have examined upper cervical rheumatoid arthritis (RA) and spinal cord disorders resulting from RA lesions, few cases of thromboembolic events in the vertebrobasilar system associated with RA lesions of the upper cervical spine have been reported. PURPOSE We encountered a rare case of repeated vertebrobasilar thromboembolism with severe upper cervical instability resulting from RA. Furthermore, we obtained clinical images of the vertebrobasilar system just before and after the first thromboembolic event. We thus present the case of a patient with RA who recovered without surgery from repeated vertebrobasilar thromboembolism that might have been caused by severe upper cervical instability. STUDY DESIGN Case report. METHODS A 59-year-old man with a 14-year history of RA experienced nuchal pain because of severe atlantoaxial and vertical subluxations. While awaiting surgery, he developed left Wallenberg syndrome because of occlusion in the left vertebral artery (VA). Five days later, he displayed impaired consciousness and symptoms of right Wallenberg syndrome. Emergency magnetic resonance angiography showed occlusion in the basilar artery. After thrombolytic therapy, he gradually recovered. RESULTS Because we presumed that the patients recurrent thrombus formation resulted from kinking of the right VA caused by severe instability of the upper cervical spine, we planned to treat him surgically despite his impaired consciousness and tracheostomy. However, the anesthesiologist would not approve surgery because the patient had high-risk conditions. The cervical spine was thus realigned and immobilized in a halo apparatus for 3 months to achieve stability. Now, more than 5 years after these events, the patient has experienced no more thromboembolic events and his condition has remained stable, without need for surgery. CONCLUSIONS Repeated vertebrobasilar thromboembolism in patients with RA may sometimes be caused by severe upper cervical instability that can be treated without surgery.

Persistent local pain after posterior spine surgery for thoracic lesions.

Many surgeons have investigated local pain associated with posterior spine surgery for cervical or lumbar lesions. However, little information is available concerning local pain after posterior thoracic spine surgery. This prospective study was, thus, performed to investigate the frequency and clinical features of local pain after posterior spine surgery for thoracic lesions. In 29 consecutive patients undergoing posterior spine surgery for various thoracic spinal disorders, local pain was investigated before and after surgery. In all 19 patients with preoperative back pain presumably due to thoracic lesions, pain was well alleviated after surgery. In contrast, 6 patients (21%) newly developed persistent shoulder angle pain after surgery, which resembled axial pain after cervical laminoplasty. In 5 of these 6 patients surgical exposure was extended to the cervicothoracic junction, whereas persistent shoulder angle pain was independent of disease etiologies and surgical procedure, and all of the 5 patients had no other etiologies of local pain such as surgical site infections, hardware failures, pseudoarthrosis, other metastasis, and vertebral fractures. These results suggest that dissection of muscle attachments to the cervicothoracic junction would play some part in the development of persistent local pain after posterior spine surgery for thoracic lesions, although surgical exposure of the zygapophysial joints at the cervicothoracic junction might be a possible source of postoperative shoulder pain. Therefore, to minimize such surgical complications, muscle insertions into the cervicothoracic junction should be preserved as far as possible.