Yuichiro Morishita

Reliability of a Magnetic Resonance Imaging-based Grading System for Cervical Intervertebral Disc Degeneration

Study Design This was a radiographic reliability study of a novel grading system for cervical intervertebral disc degeneration. Objectives This study aimed to develop and test the reliability of a reproducible grading system for cervical intervertebral disc degeneration on the basis of the routine magnetic resonance imaging (MRI). Summary of Background Data Cervical disc degeneration is common after middle age, and the morphology of cervical disc degenerative disease has often been studied using MRI. There are few specific MRI-based grading systems for cervical intervertebral disc degeneration despite the clinical importance of this problem. This study proposes a novel reproducible grading system for cervical disc degeneration and demonstrates the reliability of this classification scheme. Methods A grading system for cervical intervertebral disc degeneration was developed based on relevant previous literature. MRI grading of 300 cervical intervertebral discs using T2-weighted sagittal images was performed by 4 spinal surgeons (observers) in a blinded fashion. Intraobserver and interobserver reliabilities were assessed by calculating κ statistics. Results Grade I degeneration was observed in 27 discs (9.0%); grade II, in 56 (18.7%); grade III, in 124 (41.3%); grade IV, in 67 (22.3%); and grade V, in 26 (8.7%) discs. Kappa coefficients for intraobserver and interobserver agreements ranged from substantial to excellent (intraobserver, 0.907 to 0.950 and interobserver, 0.730 to 0.826). Complete agreement was obtained, on an average, in 72.1% of the discs. A difference of 1, 2, and 3 grades was observed in 22.4%, 3.3%, and 0.2% discs, respectively. Conclusions This grading system is comprehensive and easily applicable with sufficient reproducibility. It can be used as a common nomenclature for research and discussions.

COMPARISON OF HUMAN MESENCHYMAL STEM CELLS DERIVED FROM ADIPOSE TISSUE AND BONE MARROW FOR EX VIVO GENE THERAPY IN RAT SPINAL FUSION MODEL

Study Design. Rat spinal fusion model. Objective. To compare the efficacy of human adipose tissue-derived mesenchymal stem cells (HATDMSCs) and human bone marrow-derived mesenchymal stem cells (HBMDMSCs) transduced with an adenovirus containing the cDNA for bone morphogenetic proteins (BMP)-2 for inducing spinal fusion in an athymic rat model. Summary of Background Data. Recombinant BMPs have successfully induced spinal fusion in clinical trials. However, large doses are required for adequate bone repair. Regional gene therapy may deliver proteins to specific anatomic sites more efficiently. Gene transfer techniques using HATDMSCs have recently been tested. Methods. Spinal fusion was performed in rats with different treatments: Group I (n = 10) collagen sponge containing HATDMSCs transfected with adeno-BMP-2, Group II (n = 10) collagen sponge containing HBMDMSCs transfected with adeno-BMP-2, Group III (n = 10) collagen sponge containing recombinant BMP-2 (10 &mgr;g), Group IV (n = 6) collagen sponge containing HATDMSCs transfected with adeno-LacZ, Group V (n = 6) collagen sponge containing HBMDMSCs transfected with adeno-LacZ, and Group VI (n = 6) collagen sponge alone. Radiographs were obtained at 4, 6, and 8 weeks. After sacrifice, the rat spines were assessed by manual palpation, microcomputed tomography, and histologic analysis. Results. At 8 weeks, spinal fusion was observed in all Groups I, II, and III rats. 75% (15 of 20) of the gene therapy treatment animals (Groups I and II rats) had spontaneous extension of the fusion to a second level. No Groups IV, V, and VI rats developed fusion. New bone volume was significantly greater in Groups I and II than in Group VI. Conclusion. HATDMSCs transfected with adeno-BMP-2 induce abundant bone formation and have a similar posterolateral spinal fusion in rats as similarly genetically modified HBMDMSCs. Both are potential strategies for spinal fusion and may be a more efficient method of obtaining spinal fusion over currently used grafting substances.

Kinematic analysis of the relationship between sagittal alignment and disc degeneration in the cervical spine.

Study Design. Retrospective analysis using kinetic magnetic resonance images (MRIs). Objective. To investigate the relationship of changes in the sagittal alignment of the cervical spine on the kinematics of the functional motion unit and disc degeneration. Summary of Background Data. Normal lordotic alignment is one of the most important factors contributing to effective motion and function of the cervical spine. Loss of normal lordotic alignment may induce pathologic changes in the kinematics and accelerate degeneration of the functional motion unit. However, the relationship of altered alignment on kinematics and degeneration has not been evaluated. Methods. Kinetic MRIs in flexion, neutral, and extension were performed. Study participants were classified into 5 groups based on the C1–C7 Cobb angle of sagittal alignment—Group A: Kyphosis (n = 19), Group B: Straight (n = 29), Group C: Hypolordosis (n = 38), Group D: Normal (n = 63), and Group E: Hyperlordosis (n = 52). Intervertebral disc degeneration was graded (Grades 1–5), and the kinematics of the functional spinal unit were obtained. Results. When the alignment shifted from normal to less lordotic, the translational motion and angular variation tended to decrease at all levels. The contribution of the C1–C2, C2–C3, and C3–C4 levels to total angular mobility tended to be higher in Group C than Group D. However, the contribution of the C4–C5, C5–C6, and C6–C7 levels tended to be lower in Group C than in Group D. The grade of disc degeneration associated with loss of lordosis tended to be higher than that associated with normal alignment at the C2–C3 and C3–C4 levels. Conclusion. The present study demonstrated that the changes in sagittal alignment of the cervical spine affect the kinematics. Consequently, it may cause changes in the segment subjected to maximum load for overall motion and accelerate its degeneration.

Lumbar Segmental Mobility According to the Grade of the Disc, the Facet Joint, the Muscle, and the Ligament Pathology by Using Kinetic Magnetic Resonance Imaging

Study Design. The kinematic study of human lumbar spinal movements. Objective. To investigate how disc degeneration and the degeneration of facet joint, ligaments, and paraspinal muscles are associated with lumbar segmental mobility. Summary of Background Data. Previous studies revealed relationship between spinal motion and osteoarthritic changes of facet joint as well as disc degeneration; however, little is known about the association of disc, facet joint, ligament, and muscle degeneration with lumbar segmental motion characteristics. Methods. The 1580 lumbar motion segments from 316 patients (200 male, 116 female) underwent Kinetic magnetic resonance imaging, which were used to assess disc degeneration (grade I–V) and facet joint degeneration (grade 1–4), interspinous ligament (ISL) degeneration (grade 1–4), ligamentum flavum hypertrophy (LFH), and fatty degeneration of muscles. Segmental translational and angular motion in the flexion, extension, and neutral postures were digitally automatically measured by MR analyzer. Results. Grade II (46.77%) disc, grade 1 (48.35%) facet joint degeneration, and grade 1 (64.1%) ISL were most common. LFH was most common in L4–L5 (49/330, 14.8%). In younger age (<35), grade I disc and grade 1 facet joint were predominant compared with the older age (35≤ and <45) in which grade III, IV, and V disc and grade 2 facet joint were predominant (P < 0.05). Translational motion increased significantly in high grade of disc and facet joint (except grade V disc and grade 4 facet joint) and with LFH in L1–L5 (P < 0.05). Angular motion significantly decreased in grade V disc, grade 4 ISL, and without LFH in L1–L5 (P < 0.05). According to muscle fatty degeneration, translational and angular motions were not significantly changed. Conclusion. Our results support that facet joint degeneration is followed by disc degeneration according to age. Increased translational movements of the lumbar segments occurred in severe disc degeneration accompanied by facet joint degeneration or the presence of LFH even if the movements were stabilized in the advanced status. Therefore, the current status of the intervertebral discs, facet joints, and ligamentum flavum should be taken into consideration when evaluating stability within the lumbar spine.

Dynamic bulging of intervertebral discs in the degenerative lumbar spine.

Study Design. The effect of postural change on degenerative lumbar discs was quantified using novel kinematic magnetic resonance imaging (kMRI). Objective. The purpose is to describe the bulging of degenerative intervertebral lumbar discs in vivo subjected to different postural loads using a novel kMRI. Summary of Background Data. Symptomatic lumbar disc degeneration is a leading cause of pain and disability throughout the world. Over 70% of US citizens will experience a debilitating episode of low back pain. Earlier reports of degenerative disc changes are cadaver studies or are performed with recumbent MRI that eliminates the functional effects of gravity and muscle power. Little data are available on the behavior of degenerative intervertebral discs in vivo under physiologic loads. Methods. A total of 513 patients obtained kMRI. Disc bulging beyond the intervertebral space was quantified during upright neutral, flexion, and extension imaging. The degree of intervertebral disc degeneration was correlated using the Pfirrmann Classification. Results. Moderately degenerated intervertebral discs (grade III and IV) demonstrated greater bulging than mildly degenerated discs (grade II). Severely degenerated discs (grade V) also showed a trend toward greater bulging, but this was not significant. Grade I discs at all levels moved posteriorly in flexion and anteriorly in extension when compared to neutral posture. However, mild to severe (grade II–V) degenerative discs behaved differently in response to postural loads. Extension resulted in significant posterior bulging, while flexion did not demonstrate obvious anterior derangement. Conclusion. Disc bulging increases with the severity of disc degeneration. Grade I discs demonstrate the expected sagittal migration in response to postural load. However, more degenerative discs behave less predictably, and spine extension may result in significant posterior disc bulging. Degenerative changes in the intervertebral disc significantly affect the kinematic patterns under postural load in vivo. kMRI is a useful tool to quantify the kinematic behavior of degenerative intervertertebral discs.

Comparison of Lentiviral and Adenoviral Gene Therapy for Spinal Fusion in Rats

Study Design. Rat spinal fusion model. Objective. This study aimed to compare the efficacy of lentiviral gene therapy, and adenoviral gene therapy in inducing spinal fusion in an immune competent rat spinal fusion model. Summary of Background Data. Recombinant bone morphogenetic proteins (BMPs) have also been used for spinal fusion successfully in clinical trials. However, large doses of BMPs are required to induce adequate bone repair. Hence, regional gene therapy may be a more efficient method to deliver proteins to a specific anatomic site. Recently, lentiviral vectors based on human immunodeficiency virus have been developed for gene therapy. However, lentiviral gene therapy for spinal fusion has not been compared with adenoviral gene therapy. Methods. Lewis rats were divided into 7 groups. group I, II, III, and IV rats were implanted with a collagen sponge containing rat bone marrow cells (RBMCs) transfected with Lenti-BMP-2, Adeno-BMP-2, Lenti-GFP, Adeno-LacZ, respectively. Group V, VI, and VII rats were implanted with a collagen sponge containing recombinant BMP-2, a collagen sponge containing untransfected RBMCs, and a collagen sponge alone, respectively. The rats were assessed at 4, 6, and 8 weeks after implantation. After sacrificing the rats, their spines were explanted and assessed by manual palpation, high-resolution microcomputed tomography, and histologic analysis. Results. Spinal fusion was observed in all animals in group I, II, and V rats at 8 weeks. None of the rats in groups III, IV, VI, and VII showed spinal fusion. The volumes of the new bone in the area between the L4 and L5 transverse processes were greater in group I rats than in group II, and V rats with a significant difference. Conclusion. BMP-2-producing RBMCs developed using lentiviral gene transfer induced more abundant bone within the fusion mass than the RBMCs transduced via adenoviral gene transfer and recombinant protein therapy.

Missed Lumbar Disc Herniations Diagnosed With Kinetic Magnetic Resonance Imaging

Study Design. A novel dynamic magnetic resonance imaging (MRI) system, kinetic MRI (kMRI), was used to study lumbar disc herniations. Objective. The objective of this study was to determine if adding flexion and extension MRI studies to the traditional neutral views would be beneficial in the diagnosis of lumbar disc herniations. Summary of Background Data. Prior studies demonstrate that only 70% of patients with lumbar disc herniations based on physical examinations are confirmed by MRI studies. Recently, kMRI delivers the ability to scan patients in neutral, flexion, and extension positions, which may allow for improved diagnosis of this problem. Methods. Five hundred fifty-three patients underwent kMRI with assessment of the degree of disc bulge in neutral and flexion and extension. The images were analyzed using computer measurement technology to objectively quantify the amount of disc herniation. Results. For patients with normal or <3 mm of disc bulge in neutral, 19.46% demonstrated an increase in herniation to >3 mm bulge in extension, and 15.29% demonstrated an increase to >3 mm bulge in flexion. For patients in the neutral view that had a baseline disc bulge of 3 to 5 mm, 13.28% had increased herniations to >5 mm in extension and 8.47% had increased herniations to >5 mm in flexion. For patients with a baseline disc bulge of 5 to 7 mm in neutral, 10.58% increased in extension and 5.78% increased in flexion. In addition, for patients with a baseline disc bulge of 7 to 9 mm in neutral, 9.09% increased in extension and 4.55% increased in flexion. Conclusion. A significant increase in the degree of lumbar disc herniation was found by examining flexion and extension views when compared with neutral views alone. kMRI views provide valuable added information, especially in situations where symptomatic radiculopathy is present without any abnormalities demonstrated on conventional MRI.

The effects of the degenerative changes in the functional spinal unit on the kinematics of the cervical spine.

Study Design. The sagittal kinematics of the cervical spine was evaluated using kinematic magnetic resonance imaging (kMRI). Objective. To investigate the effect of degenerative changes in the functional spinal unit on cervical kinematics by using kMRI. Summary of Background Data. Few studies have, thus far, by using MR images, described the contribution of degenerative changes in the functional spinal unit to cervical kinematics; however, the exact cervical kinematics remains uncertain. Methods. A total of 289 consecutive symptomatic patients underwent dynamic cervical MRI in flexion, neutral, and extension postures. All digital measurements and calculations of the variations in segmental angular motion were automatically performed by an MR analyzer using true MR images with 77 predetermined points marked on each image. Each segment was assessed based on the extent of intervertebral disc degeneration (Grades 1–3) and cervical cord compression (groups A–C) observed on T2-weighted MR images. Results. The segmental mobility of the segments with severe cord compression and moderate disc degeneration tended to be lower than that of the segments with severe cord compression and severe disc degeneration, and a significant difference was observed in the segmental mobility of the C5–C6 segment. Moreover, in all segments with moderate disc degeneration, the segmental mobility was significantly reduced in the presence of severe cord compression, as compared with no compression. However, in segments with severe disc degeneration, no significant differences were observed between the segmental mobility of the cord compression groups. Conclusion. Our results suggest that cervical cord compression may cause deterioration of cervical cord function and kinematic changes in the cervical spine. We hypothesize that the spinal cord may potentially protect its functions from dynamic mechanical cord compression by restricting segmental motion, and these mechanisms may be closely related to the intervertebral discs.

The effects of lentiviral gene therapy with bone morphogenetic protein-2-producing bone marrow cells on spinal fusion in rats.

Study Design Rat spinal fusion model. Objective This study aimed to assess the ability of rat bone marrow cells (RBMCs) transfected with bone morphogenetic protein (BMP)-2-containing lentivirus to induce a posterolateral spinal fusion in a rat model. Summary of Background Data Spinal arthrodesis is a commonly performed spinal procedure and autograft remains the standard for achieving spinal fusion. However, its procurement is associated with significant morbidity, and the rate of pseudoarthrosis has been reported to be 5% to 43%. Nonunion frequently leads to an unsatisfactory resolution of clinical symptoms and usually results in high medical costs and morbidity as well as the need for additional surgeries. These problems have led surgeons to search for alternative solutions to stimulate bone formation. Recombinant BMPs have also been used successfully in clinical trials. However, large doses of BMPs were required to induce adequate bone repair. The development of a regional gene therapy may be a more efficient method to deliver proteins to a specific anatomic site. Furthermore, adeno-BMP-2-producing rat bone marrow-derived cells have been used successfully to induce posterior spinal fusion. Recently, lentiviral vectors on the basis of human immunodeficiency virus have been developed for gene therapy. Lentiviruses are capable of insertion into the host genome, ensuring a prolonged gene expression. However, safety issues are a major concern when adopting these vectors for clinical use. Methods In vitro study, we used RBMCs transfected with lentivirus vectors encoding BMP-2 (Lenti-BMP-2), RBMCs transfected with lentivirus vectors encoding the green fluorescent protein (GFP) (Lenti-GFP), and untransfected RBMCs; the latter 2 were used as controls. Alkaline phosphatase (ALP) staining and ALP activity were compared between the groups to assess the ability of the Lenti-BMP-2-transfected RBMCs to stimulate osteoblastic differentiation. In the rat posterolateral spine fusion model, the experimental study comprised 4 groups. Group 1 comprised 6 animals that were implanted with a collagen sponge containing 5 million RBMCs transfected with Lenti-BMP-2. Group 2 comprised 3 animals that were implanted with a collagen sponge containing 5 million RBMCs transfected with Lenti-GFP. Group 3 comprised 6 animals that were implanted with a collagen sponge containing 5 million untransfected RBMCs. Group 4 comprised 3 animals that were implanted with a collagen sponge alone. The rats were assessed by radiographs obtained at 4, 6, and 8 weeks. After death, their spines were explanted and assessed by manual palpation, high-resolution microcomputerized tomography, and histologic analysis. Results The ALP staining was significantly greater in the Lenti-BMP-2-transfected RBMCs than in the untransfected RBMCs and the Lenti-GFP-transfected RBMCs. The ALP activity was 3-fold greater in the Lenti-BMP-2-transfected RBMCs than in the untransfected RBMCs and the Lenti-GFP-transfected RBMCs. In the rat spine fusion model, radiographic evaluation, high-resolution microcomputerized tomography, and manual palpation revealed spinal fusion in all the rats in Group 1 at 8 weeks. Groups 2, 3, and 4 comprised the control group. None of the rats in the control group (0 of 12) developed fusion at L4-L5. Conclusions The present study demonstrated that BMP-2-producing RBMCs, created through lentiviral gene transfer, induced sufficient spinal fusion. The use of lentiviral vectors that contain the cDNA for BMP-2 will be a novel and promising approach for a spinal fusion strategy.

A porcine model of intervertebral disc degeneration induced by annular injury characterized with magnetic resonance imaging and histopathological findings : Laboratory investigation

OBJECT Appropriate animal models of disc degeneration are critical for the study of proposed interventions as well as to further delineate the degenerative process. The purpose of this study was to characterize a porcine model for disc degeneration confirmed on magnetic resonance (MR) imaging studies and histological analysis. METHODS Twelve miniature pigs were used (weight 48-65 kg) to study degeneration in the lumbar spine. Under fluoroscopic guidance, the disc was percutaneously punctured with a 3.2-mm-diameter trephine to a 5-mm depth into the annulus fibrosus. Control and experimental levels were randomized among 6 levels in the lumbar spine. The unlesioned spinal levels were used as controls and were compared with lesioned levels. Magnetic resonance imaging grading and disc height were serially recorded preoperatively, and at 5, 8, 19, 32, and 39 weeks postoperatively. The animals were killed in groups of 3 at 7, 18, 32, and 41 weeks postinjury, and the discs were examined histopathologically. RESULTS Consistent, sequential, and progressive degeneration of the annular injury was observed on MR imaging and histopathological studies from the time of injury to the final time point. The disc height and the disc height index also sequentially decreased from the time of the injury in a consistent manner. The uninjured control levels did not show any progressive degeneration and maintained their normal state. CONCLUSIONS Based on MR imaging and histopathological findings, the authors demonstrated and characterized a reliable model of sequential disc degeneration in miniature pigs with percutaneous injury to the annulus fibrosus. In the early stages, as soon as 5 weeks after injury, significant disc degeneration was seen on MR imaging grading with decreases in disc height. This degeneration did not improve by the final time point of 39 weeks.