OBJECTIVE: The purpose of this study was to analyze the biomechanical effects of three different constrained types of an artificial disc on the implanted and adjacent segments in the lumbar spine using a finite element model (FEM). METHODS: The created intact model was validated by comparing the flexion-extension response without pre-load with the corresponding results obtained from the published experimental studies. The validated intact lumbar model was tested after implantation of three artificial discs at L4-5. Each implanted model was subjected to a combination of 400 N follower load and 5 Nm of flexion/extension moments. ABAQUStrade mark version 6.5 (ABAQUS Inc., Providence, RI, USA) and FEMAP version 8.20 (Electronic Data Systems Corp., Plano, TX, USA) were used for meshing and analysis of geometry of the intact and implanted models. RESULTS: Under the flexion load, the intersegmental rotation angles of all the implanted models were similar to that of the intact model, but under the extension load, the values were greater than that of the intact model. The facet contact loads of three implanted models were greater than the loads observed with the intact model. CONCLUSION: Under the flexion load, three types of the implanted model at the L4-5 level showed the intersegmental rotation angle similar to the one measured with the intact model. Under the extension load, all of the artificial disc implanted models demonstrated an increased extension rotational angle at the operated level (L4-5), resulting in an increase under the facet contact load when compared with the adjacent segments. The increased facet load may lead to facet degeneration.
Information Systems ; Spine ; Total Disc Replacement

STUDY DESIGN: A review of the literature regarding anterior cervical surgery in degenerative cervical radiculopathy. OBJECTIVES: To review and discuss anterior cervical spine surgery. SUMMARY OF LITERATURE REVIEW: Anterior cervical spine surgery is commonly used to treat numerous pathologic entities and is expected to increase with the development of surgical techniques and instruments. Nevertheless, there is some controversy. MATERIALS AND METHODS: Literatures review. RESULTS: Surgical treatments using the anterior approach in degenerative cervical disease have shown excellent results. A range of techniques using plate augmentation and artificial disc replacement are now accepted as effective methods. CONCLUSIONS: The appropriate method considering the pathologic status of the patient and surgeon's surgical experience can prevent complications and lead to excellent surgical outcomes.
Humans ; Radiculopathy ; Spine ; Total Disc Replacement

Direct anterior approach for lesions located anterior to the thecal sac is definitely superior to lateral or posterior approach in many respects. However, various anatomical obstacles and technical difficulties often hinder direct anterior approach. Thanks to ripe experience of retroperitoneal approach to the lumbar spine for anterior lumbar interbody fusion and total disc replacement, the authors could perform lumbar corpectomy and reconstruction by using midline retroperitoneal approach recently. During this approach, we repaired anterior longitudinal ligament also to reduce the risk of graft extrusion and to prevent erosion of vascular wall due to direct contact between metallic hardware, which was used for reconstruction of vertebral body, and major vessels.
Longitudinal Ligaments ; Spine ; Total Disc Replacement ; Transplants

OBJECTIVE: This study was designed to investigate the correlation between insertion depth of artificial disc and postoperative kyphotic deformity after Prodisc-C total disc replacement surgery, and the range of artificial disc insertion depth which is effective in preventing postoperative whole cervical or segmental kyphotic deformity. METHODS: A retrospective radiological analysis was performed in 50 patients who had undergone single level total disc replacement surgery. Records were reviewed to obtain demographic data. Preoperative and postoperative radiographs were assessed to determine C2-7 Cobb's angle and segmental angle and to investigate postoperative kyphotic deformity. A formula was introduced to calculate insertion depth of Prodisc-C artificial disc. Statistical analysis was performed to search the correlation between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity, and to estimate insertion depth of Prodisc-C artificial disc to prevent postoperative kyphotic deformity. RESULTS: In this study no significant statistical correlation was observed between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity regarding C2-7 Cobb's angle. Statistical correlation between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity was observed regarding segmental angle (p<0.05). It failed to estimate proper insertion depth of Prodisc-C artificial disc effective in preventing postoperative kyphotic deformity. CONCLUSION: Postoperative segmental kyphotic deformity is associated with insertion depth of Prodisc-C artificial disc. Anterior located artificial disc leads to lordotic segmental angle and posterior located artificial disc leads to kyphotic segmental angle postoperatively. But C2-7 Cobb's angle is not affected by artificial disc location after the surgery.
Congenital Abnormalities ; Humans ; Retrospective Studies ; Total Disc Replacement

Complex regional pain syndrome (CRPS) is characterized by pain, sensory, motor and autonomic symptoms. But its pathophysiological mechanisms are unclear and CRPS is quite difficult to comprehend and treat. The diagnostic criteria for CRPS at this time are purely clinical, and the use of diagnostic tests has not been demonstrated, so that misdiagnosis of CRPS is not uncommon. We report a case misdiagnosed CRPS which is due to the complication of one level total cervical disc replacement, which was treated successfully with reoperation.
Diagnostic Errors ; Diagnostic Tests, Routine ; Humans ; Reoperation ; Total Disc Replacement

OBJECTIVETo evaluate stress changes of intervertebral space and adjacent intervertebral space after artificial disc replacement with angles.

METHODSArtificial disc replacement with angles were designed according to existing data. Axial pressure, flexion/extension, lateral bending and torsion loading were applied on finite element models of normal cervical discs on C4,5 segments, C4,5 segments with 0 degrees artificial cervical discs and C4,5 segments with 10 degrees artificial cervical discs, then stress changes of C4,5 space was observed. The same loadings were applied on finite element models of normal cervical discs on C4-C6 segments, C4,5 segments with 0 degrees, C4,5 segments with 10 degrees, then stress changes of replaced segments space and adjacent segment space were observed.

RESULTSFor C4,5 segments, 80 MPa/0 degrees artificial discs and 80 MPa/10 degrees artificial discs had the similar equivalent shear stress (Se), and were both larger than that of normal discs, when lateral bending were performed, 80 MPa/0 degrees artificial discs were closed to normal discs when axial pressure and flexion/extension were carried out, while 80 MPa/10 degrees artificial discs had a larger Se than that of normal ones,when torsion loading were applied, Szx/Szy stress of 80 MPa/0 degrees and 80 MPa/10 degrees artificial discs were closed to normal ones. For C4-C6 segments, the axial pressure, flexion/extension and lateral bending of C5,6 were all lower than normal discs after C4,5 discs were replaced by 80 MPa/10 degrees artificial discs, while Szx/Szy of torsion loading were closed to normal ones.

CONCLUSIONArtificial discs with 10 degrees have less influences on stress of adjacent intervertebral space and closer to mechanical property after being implanted into intervertebral space.

We present two cases of unexpected postoperative intractable cervicalgia due to over-sized implant insertion during simple anterior cervical decompression and fusion (ACDF) or artificial disc replacement (ADR). These patients experienced severe cervicalgia mostly related to their neck motion even after standard cervical operations. In both cases, the restored disc heights after the operations were prominently greater than the preoperative disc heights. The patients had not responded to any of the conservative treatments, and unloading of these excessively distracted segments through ultimate revision surgery led to dramatic pain relief. This report emphasizes the increase in distractional forces that takes place after a standard ACDF or ADR, as well as the importance of a proper sized implant. It also includes the reviews of other biomechanical or clinical reports dealing with this issue, thereby cautioning the surgeons not to disregard these factors, which might have an adverse effect in patients with cervicalgia even after radiographically successful cervical procedures.
Allografts ; Decompression ; Humans ; Neck ; Neck Pain ; Surgeons ; Total Disc Replacement

In surgical treatments of degenerative lumbar disc disease, arthrodesis is well known to be a gold standard; however various disadvantages related to elimination of the segmental motion and the procedures of fusion surgery have become a matter of concern. To this end, total disc replacement (TDR) was recently highlighted as one of alternative surgical modalities and being used widely. However, although it has been almost 10 years since lumbar TDR was int- roduced and actively used in the clinic, its clinical usefulness is still in dispute. The authors review and put together the history, biomechanics, and currently available prostheses of lumbar TDR in the present study. Some of the recent preliminary, mid-term and long-term clinical results of lumbar TDR in degenerative lumbar spine diseases are also reviewed. Lastly, we look out over the future prospect of lumbar TDR.
Arthrodesis ; Biomechanics ; Dissent and Disputes ; Intervertebral Disc Degeneration ; Intervertebral Disc Displacement ; Prostheses and Implants ; Spine ; Total Disc Replacement

BACKGROUND: Several scoring systems for cervical disc and facet joint degeneration, using radiography or computed tomography, have been developed and tested for reliability. However, definitions of disc height and facet joint space narrowing vary. To our knowledge, no study has reported quantitative data for normal radiologic values of the cervical spine in the Korean population. The purpose of this study is to determine normal cervical disc height, disc height ratio, and facet joint space values, and investigate the correlation between demographic data and these values. METHODS: We performed a retrospective study of patients who underwent artificial disc replacement of the cervical spine. Disc heights and facet joint spaces were measured using cervical neutral lateral radiographs and computed tomography. The means, standard deviations, and 95% confidence intervals of the values were determined. RESULTS: We measured 148 intervertebral discs and 352 posterior facet joints. The mean disc height measured by plain radiography and computed tomography was 5.57 ± 0.81 mm and 4.94 ± 0.94 mm, respectively. The mean facet joint space values measured by plain radiography and computed tomography were 1.94 ± 0.45 mm and 1.43 ± 0.39 mm, respectively. The disc heights and facet joint space values measured by plain radiography were greater than those measured by computed tomography. The lower limit of the 95% confidence interval of the disc height ratio calculated by plain radiography and computed tomography was greater than 0.94 at all levels except for C5–6. Patient height and disc height showed a tendency of positive correlation. CONCLUSIONS: In a Korean population, the normal cervical disc height was about 5.0 mm and the normal facet joint space was 1.4 mm. Disc height ratio can reliably identify normal cervical disc height in patients with mild degeneration. Patient height was positively correlated with disc height and facet joint space. Thus, when selecting a cervical implant, surgeons should consider patient height as well as estimated normal disc height.
Humans ; Intervertebral Disc ; Intervertebral Disc Degeneration ; Radiography ; Retrospective Studies ; Spine ; Surgeons ; Total Disc Replacement ; Zygapophyseal Joint

Fusion surgery remains the gold standard for surgical treatment of lumbar degenerative disc disease (DDD). However, fusion surgery has many intrinsic problems related to altered biomechanics and balance. Total disc replacement (TDR) has received increasing attention over the last several years because of its capacity for both functional and symptomatic improvement and its avoidance of problems intrinsic to fusion surgery. Artificial disc replacement is not a new concept, the first attempts having been undertaken in the early 1950s. However, during the past 15 years, considerable advances have been made, with clinical success noted in several prospective randomized studies and mid-long term retrospective studies. Proper patient selection and surgical technique are key factors in achieving a successful outcome. TDR plays a limited role and has limited indications for replacing fusion surgery in patients with lumbar DDD. The main goal of TDR is restoration of normal intervertebral disc function. Varying degrees of motion can be restored through TDR; however, the pattern of motion and center of rotation are not physiologic. In spite of some favorable reports, many TDR-related problems remain to be solved. Successful disc function is measured not only in terms of quantity of motion, but also in terms of quality of motion and shock energy absorption capacity. For successful repair to be declared, facet unloading should be achieved, and fatigue strength should be improved. New procedures should be characterized by a reduction in the technical problems of implantation and retrieval. We expect that the next generation of TDR will overcome the limitations of first generation TDR. This therapeutic modality shows much promise for the treatment of lumbar DDD.
Absorption ; Biomechanics ; Dichlorodiphenyldichloroethane ; Fatigue ; Humans ; Intervertebral Disc ; Patient Selection ; Shock ; Total Disc Replacement