Jun Zou

Kinematic analysis of the relationship between the grade of disc degeneration and motion unit of the cervical spine.

Study Design. Kinetic MRIs of cervical spines were obtained and analyzed according to the amount of motion and the degenerative grade of the intervertebral disc. Objective. To define the relationship between the grade of disc degeneration and the motion unit of the cervical spine and elucidate changes in the role of each cervical spine unit during flexion-extension motion caused by degeneration. Summary of Background Data. Degenerative changes in the cervical disc occur with age. The correlation between the degree of cervical disc degeneration and extent of cervical spine mobility has not yet been determined. The effect of degeneration on the overall motion of the functional spinal unit also remains undefined. Methods. We studied 164 patients with symptomatic neck pain. The cervical intervertebral discs were graded by spine surgeons according to the degenerative grading system (Grades I to V). All radiologic data from kinetic MRIs were recorded on a computer for subsequent measurements. All measurements and calculations for translational motion and angular variation of each segment were automatically performed by a computer analyzer. Results. The translational motion in discs with Grade II degeneration (mild degeneration) increased to Grade III degeneration (higher degeneration). However, the translational motion and angular variation significantly decreased for the Grade V (severe degeneration). For patients with relatively low grades of degeneration, Grades I and II discs, the C4–C5 and C5–C6 segmental units contributed the majority of total angular mobility of the spine. However, for the severely degenerated segments, Grade V discs, the contributions of the C4–C5 and C5–C6 U significantly decreased. Conclusion. The changes that occur with disc degeneration progress from the normal state to an unstable phase with higher mobility and subsequently to an ankylosedstage. This study evaluated the contribution of different levels to the changes in overall motion that occur with degeneration.

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.

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.