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.

We investigated intervertebral motions of the subaxial cervical spine during head rotation using a three-dimensional imaging system, and obtained the first accurate depictions of in vivo coupled motion. These findings will be helpful as the basis for understanding abnormal conditions.

We succeeded in identifying in vivo coupled motions of the cervical spine in lateral bending for the first time.

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 voxelbased 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°t o 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.

Several articles reported the association between the development of subaxial kyphosis and the hyperlordotic fixation of C1-C2. However, their patients were heterogeneous in both primary disease and operative procedure. Transarticular screw fixation has become a popular procedure for C1-C2 arthrodesis instead of wiring techniques in which C1-C2 is difficult to fix in the intended alignment. Furthermore, in rheumatoid arthritis (RA) patients, subaxial lesions play an important role in potential subaxial alignment changes. The subaxial influences after C1-C2 transarticular screw fixation in patients with RA are unclear. To investigate the radiographic features of the subaxial cervical spine after C1-C2 transarticular screw fixation for RA, we reviewed 28 cases of C1-C2 transarticular screw fixation for rheumatoid atlanto-axial subluxation. The sagittal alignment of C1-C2 and the subaxial cervical spine was measured and the factors that affect subaxial alignment were investigated. Subaxial alignment became less lordotic in the postoperative course. The C1-C2 fixation angle and subaxial alignment showed a negative linear correlation. However, no significant correlation was found between changes in the C1-C2 angle and changes in the subaxial alignment. Four patients had a postoperative kyphotic subaxial deformity. Neurologic deterioration recurred in 4 patients, because of the postoperative development of subaxial subluxation. Common radiographic changes included an increase in C1-C2 lordosis, constant inclination of C1, an anterior shift of C2, and a decrease in C2-C7 lordosis. Many factors, not only C1-C2 angle, are associated with subaxial sagittal alignment change after C1-C2 transarticular screw fixation.