Study Design. Cross-sectional study. Objective. To investigate the prevalence, concomitance, and distribution of various types of ossification of the spinal ligaments in healthy subjects using computed tomography (CT). Summary of Background Data. CT has better diagnostic accuracy for ossification of the spinal ligaments compared to plain radiography. Currently there is no study that examines the prevalence of ossification of the spinal ligaments using whole spine CT scans. Methods. One thousand five hundred Japanese patients (888 men and 612 women) who underwent positron emission tomography and CT (PETCT) in a private health check center between 2006 and 2013 were included. This PETCT was performed on self-paying participants as a preventive cancer screen. Existence of ossification of the posterior longitudinal ligament (OPLL), ligamentum flavum (OLF), anterior longitudinal ligament (OALL), diffuse idiopathic skeletal hyperostosis (DISH), and nuchal ligament (ONL) was examined. Results. The prevalence of spinal ligament ossifications was found to be 6.3% in cervical OPLL (8.3% in men and 3.4% in women), 23% in ONL (33% in men and 8.8% in women), 1.6% in thoracic OPLL (1.4% in men and 2.0% in women), 12% in thoracic OLF (15% in men and 7.7% in women), 37% in thoracolumbar OALL (45% in men and 26% in women), and 12% in DISH (16% in men and 6.2% in women). Thirteen percent of patients with cervical OPLL had thoracic OPLL, 34% of cervical OPLL had thoracic OLF, 45% of cervical OPLL had ONL, and 36% of cervical OPLL had DISH. The most common level was C5 for cervical OPLL, T1/2 for thoracic OPLL, T11 for thoracic OLF, and T8/9 for OALL. Conclusion. Accurate prevalence of various types of ossification of the spinal ligaments evaluated by CT was revealed. High concomitance was observed in each classification of spinal ligament ossification. Level of Evidence: 3

Study Design. Retrospective study. Objective. We sought to determine the long-term outcomes of laminoplasty versus anterior decompression and fusion in the treatment of cervical myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) and to ascertain what factors should be considered in selecting appropriate surgical procedure. Summary of Background Data. There are little data about long-term results of cervical myelopathy due to OPLL with an occupying ratio 60% or more. Methods. We retrospectively studied 27 patients having OPLL with an occupying ratio 60% or more and a follow-up period of at least 2 years. Clinical outcome was evaluated using Japanese Orthopaedic Association scores and recovery rates (≥75%, excellent; 50%–74%, good; 25%–50%, fair; and <25%, poor). Results. The mean age and the mean duration of follow-up were 57 years and 10.2 years. The mean Japanese Orthopaedic Association score was 9.3 before surgery and 12.4 at the final follow-up examination. There were 15 patients in the laminoplasty group (LAM group) and 12 patients in the anterior decompression and fusion group (ADF group). The ADF group had a significantly better recovery rate at final evaluation (53% vs. 30%; P = 0.04), a longer duration of surgery (314 vs. 128 min; P < 0.01), and greater blood loss (600 vs. 240 mL; P < 0.01) than did the LAM group. In the LAM group, 4 patients with excellent or good results had a significantly larger degree of cervical lordosis (30°vs. 10°; P = 0.002) than others. Conclusion. The ADF group had a significantly better recovery rate than the LAM group, although the degree of surgical invasiveness was high. ADF is generally recommended for OPLL with an occupying ratio 60% or more. Level of Evidence: 3

Study Design: Retrospective cohort study. Objective: To compare the clinical and radiographic outcomes of transforaminal lumbar interbody fusion (TLIF) and posterolateral lumbar fusion (PLF) in the treatment of degenerative spondylolisthesis. Methods: This study compared 24 patients undergoing TLIF and 32 patients undergoing PLF with instrumentation. The clinical outcomes were assessed by visual analog scale (VAS) for low back pain and leg pain, physical component summary (PCS) of the 12-item Short-Form Health Survey, and the Oswestry Disability Index (ODI). Radiographic parameters included slippage of the vertebra, local disk lordosis, the anterior and posterior disk height, lumbar lordosis, and pelvic parameters. Results: The improvement of VAS of leg pain was significantly greater in TLIF than in PLF unilaterally (3.4 versus 1.0; p = 0.02). The improvement of VAS of low back pain was significantly greater in TLIF than in PLF (3.8 versus 2.2; p = 0.02). However, there was no significant difference in improvement of ODI or PCS between TLIF and PLF. Reduction of slippage and the postoperative disk height was significantly greater in TLIF than in PLF. There was no significant difference in local disk lordosis, lumbar lordosis, or pelvic parameters. The fusion rate was 96% in TLIF and 84% in PLF ( p = 0.3). There was no significant difference in fusion rate, estimated blood loss, adjacent segmental degeneration, or complication rate. Conclusions: TLIF was superior to PLF in reduction of slippage and restoring disk height and might provide better improvement of leg pain. However, the health-related outcomes were not significantly different between the two procedures.

In vivo 3-dimensional (3D) study of the thoracic spine. To demonstrate axial rotations (ARs) and coupled motions of the thoracic spine. In vivo 3D kinematics of the thoracic spine in trunk rotation with intact thorax and soft tissues has not been well-known. There were no quantitative data of AR in the consecutive thoracic spinal segments. Patterns of coupled motion with AR have been controversial. Thirteen healthy volunteers underwent 3D computed tomography of the thoracic spine in 3 positions; neutral, right, and left maximum trunk rotation. Relative motions of vertebrae were calculated by automatically superimposing the vertebrae in a neutral position over images in rotational positions, using voxel-based registration. Motions were represented with 6 degrees of freedom by Euler angles and translations on the local coordinate system. Mean (±SD) relative rotational angles of T1 with respect to L1 to 1 side were 24.9° ± 4.9° in maximum trunk rotation. AR of each thoracic segment with respect to the inferior adjacent vertebra to 1 side was 1.2° ± 0.8° at T1–T2, 1.6° ± 0.7° at T2–T3, 1.4° ± 0.9° at T3–T4, 1.6° ± 0.8° at T4–T5, 1.8° ± 0.7° at T5–T6, 1.9° ± 0.6° at T6–T7, 2.3° ± 0.7° at T7–T8, 2.5° ± 0.8° at T8–T9, 2.7° ± 0.6° at T9–T10, 2.6° ± 0.8° at T10–T11, 1.3° ± 0.7° at T11–T12, and 0.5° ± 0.4° at T12–L1. Significantly larger segmental AR was observed at the middle thoracic segments (T6–T11) than at the upper (T1–T6) and lower (T11–L1) segments. At the upper thoracic segments, coupled lateral bending with AR was observed in the same direction as AR. However, at the middle and lower thoracic segments, coupled lateral bending occurred both in the same and opposite directions. In vivo 3D ARs and coupled motions of the consecutive thoracic spinal segments in trunk rotation were investigated accurately for the first time.