Introduction Total disc arthroplasty serves as the next frontier in the surgical management of intervertebral discogenic pathology. As we move from an era of interbody spinal arthrodesis to one in which segmental motion is preserved, this promising new technology offers increasing clinical and research challenges in the areas of spinal kinematics, histologic osseointegration at the prosthetic-bone interface and the effects of particulate wear debris. The primary focus of this paper is to provide a methodological basis to investigate the spinal kinematics, histologic osseointegration and particulate wear debris following total disc replacement arthroplasty using in-vitro and in-vivo models. MethodsPart I: Using an in-vitro cadaveric model, multidirectional flexibility testing evaluated the functional unit kinematics under the following L4-L5 reconstruction conditions: 1) Intact Spine; 2) Charitè Disc Prosthesis; 3) BAK Cages; 4) BAK Cages + ISOLA pedicle screw/rod fixation (anteroposterior). Part II: A total of twenty-seven mature baboons (n=27, Papio cynocephalus) underwent L5-L6 total disk replacement procedures to investigate the biomechanical, histochemical, and biologic ingrowth characteristics of two different lumbar disc prostheses – AcroFlex and Charite’ – for total disc replacement arthroplasty. Functional spinal unit fusion status was assessed using radiographic analysis, biomechanical testing, undecalcified histopathologic and histomorphometric analyses. Part III: Using a total of Fifty New Zealand White rabbits, the current study served to quantify the neural and systemic tissue histopathological response, following epidural application of four different types of spinal instrumentation particulate wear debris – 1) Sham (control) (n=10), 2) Stainless Steel 316LVM (n=10), 3) Titanium Alloy Ti-6AL-4V (n=10), 4) Cobalt Chrome Alloy (n=10) and 5) Ultrahigh molecular weight polyethylene (UHMWPE) (n=10). Results In-vitro multi-directional flexibility testing demonstrates the operative and adjacent level motion preserving properties of total disc arthroplasty versus interbody arthrodesis cages and pedicle screw spinal instrumentation. To this end, disc replacement preserves the normal centrode or locus of intervertebral rotation at the operative and adjacent intervertebral spinal levels compared to conventional stabilization implants. Based on non-human primate modeling in the current studies, porous titanium interface surfaces afforded the greatest percentage of trabecular in-growth at the prosthesis-end-plate interface. In-vivo segmental motion under multi-directional testing was preserved with the Charité device and slightly diminished with the AcroFlex implants. The porous ingrowth coverage at the bone-metal interface was more favorable for total disk replacement (range 40 to 50%) compared to that reported for cementless total joint components in the appendicular skeleton (range 10 to 30%). Direct epidural application of spinal instrumentation particulate wear debris elicits a chronic histiocytic reaction localized primarily within the epidural fibrous layers. Moreover, particles have the capacity to diffuse intrathecally, eliciting a macrophage / cytokine response within the epidural tissues, cerebrospinal fluid and spinal cord itself. Overall, based on the post-operative time periods evaluated, there was no evidence of an acute neural or systemic histopathologic response to the materials included in the current project. Conclusions The implementation of dynamic spinal stabilization systems for fusionless correction of spinal deformity, dynamic posterior stabilization and total disc replacement arthroplasty necessitates improved understanding with regard to spinal kinematics, patterns / mechanisms of histologic osseointegration and the neurohistopathologic response to particulate wear debris. Collectively, the current studies provide a methodological basis to comprehensively evaluate these three areas

Introduction Lumbar fusion may alter the sagittal balance of the spine, including a decrease in the sacral tilt ST and lumbar lordosis. Postoperative pain following a spinal fusion has been shown to be related to changes in sagittal balance, independent of other factors including pseudarthrosis. The goal of this radiological study was to prospectively determine the effect of a single-level, total disc replacement on the sagittal balance of the spine, especially on sacral tilt (ST), pelvic tilt (PT), and lumbar lordosis (Le Huec J, et al; Spine J. 2004). Method 35 patients received a single level disc replacement using the Maverick Total Disc Arthroplasty system (Medtronic Sofamor Danek). The preoperative and postoperative radiographic evaluation included standing anteroposterior and lateral full spine films that included the femoral heads. The parameters studied were ST, PT, global and segmental lordosis, and global kyphosis. The average age of the 35 patients studied was 44.3 years (range 35–57). There were 18 females and 17 males. The disc arthroplasty was performed at the L4–L5 level in 19 patients and at the L5-S1 level in 16 patients. The average follow-up was 14 months (range 6–22 months). Results The preoperative values of global lordosis, ST, PT and global lordosis were not significantly different at last follow-up. When the groups were compared according to the level operated, there was no statistical difference with regard to the overall lordosis, ST, PT or kyphosis from pre- to postoperative period or when the two groups were compared with each other. The level above the prosthesis has significantly less lordosis. Discussion In the present study with use of a motion-preserving intervertebral disc prosthesis, it appears that the patient is able to maintain the preoperative sagittal balance. The prosthesis has enough freedom of motion to allow the patient to maintain the natural sagittal and spinopelvic balance needed to prevent potentially undue stress on the muscles and the sacroiliac joint. Although the number of patients is small, this is the first study that evaluates the sagittal balance after motion-preserving total disc arthroplasty

Introduction: Two total disc replacement devices have been used in Europe for more than 10 years. However, there are few, if any, prospective studies evaluating their results. The purpose of this prospective study using standardized outcome evaluations was to evaluate surgical outcome following implantation of an artificial disc. Methods: This study is based on the consecutive series of the first 57 patients undergoing total disc replacement using the SB Charité (Link) disc prosthesis. Indications included single-level symptomatic disc degeneration, failure of at least 6 months of non-operative treatment including active rehabilitation, and no previous surgery at the operated segment. Data were collected prospectively pre-operatively and at 6 weeks, 3, 6, and 12 months post-operatively (24 month follow-up data collection is continuing). Primary outcome measures included visual analog scales (VAS) assessing pain and the Oswestry Low Back Pain Disability Questionnaire. Results: The mean operative time was 78.5 minutes and the mean estimated operative blood loss was 134.3 cc. Estimated blood loss and operating time were both significantly less for disc replacements at the L5-S1 level than at L4–5 (p< 0.05; t-test). As seen in Figures 1 and 2, there was a significant improvement in the VAS and Oswestry scores (p< 0.05) at the 6-week follow-up visit, and the improvements were maintained during subsequent follow-up visits. There were no cases of device failure, displacement, or migration. Complications were comparable to those encountered with anterior interbody fusion. Discussion: The results of this prospective study, using patient self-report questionnaires, demonstrated significant improvement at 6 weeks and the improvement was maintained during the 12 month follow-up period (24-month data is being collected). The disc prosthesis can be implanted safely, with complications similar to those encountered with anterior lumbar interbody fusion

INTRODUCTION: Two total disc replacement devices have been used in Europe for more than 10 years. However, there are few, if any, prospective studies evaluating their results. The purpose of this prospective study using standardised outcome evaluations was to evaluate surgical outcome following implantation of an artificial disc. METHODS: This study is based on the consecutive series of the first 57 patients undergoing total disc replacement using the SB Charité (Link) disc prosthesis. Indications included single-level symptomatic disc degeneration, failure of at least six months of non-operative treatment including active rehabilitation, and no previous surgery at the operated segment. Data were collected prospectively pre-operatively and at six weeks, three, six, and 12 months post-operatively (24 month follow-up data collection is continuing). Primary outcome measures included visual analog scales (VAS) assessing pain and the Oswestry Low Back Pain Disability Questionnaire. RESULTS: The mean operative time was 78.5 minutes and the mean estimated operative blood loss was 134.3 cc. Estimated blood loss and operating time were both significantly less for disc replacements at the L5-S1 level than at L4-5 (p< 0.05; t-test). As seen in Figures 1 and 2, there was a significant improvement in the VAS and Oswestry scores (p< 0.05) at the six week follow-up visit, and the improvements were maintained during subsequent follow-up visits. There were no cases of device failure, displacement, or migration. Complications were comparable to those encountered with anterior interbody fusion. DISCUSSION: The results of this prospective study, using patient self-report questionnaires, demonstrated significant improvement at six weeks and the improvement was maintained during the 12 months follow-up period (24-months data is being collected). The disc prosthesis can be implanted safely, with complications similar to those encountered with anterior lumbar inter-body fusion

Since total disc replacement (TDR) has broadened the spectrum of surgical treatment of degenerative spine diseases many comparison studies, particularly with interbody fusions (IF), have been done. Even though comparable results concerning functionality, radiologic results and subjective rating of life-quality have been presented, very few data about athletic activity before and after spine surgery exists. Material and Methods: Between 1/2002 and 10/2006 181 patients had interbody fusions and 57 had a total disc replacement. Of 86 IF-patients and 25 patients with TDR we have complete data, which was collected in pre- and postoperative clinic and radiologic routine control with standardised questionnaires containing evaluation of level (frequency) and sort of sport. Patients are matched according to demographic data and preoperative activity beside the most important match of operation method. Results: Patients with Total disc replacement show a later resumption of sports (19 weeks) than fusion patients (14 weeks), but more TDR patients (60%) achieve their preoperative level of sport than IF-patients (36%) do. Vice versa to the Fusion group in the TDR group more patients start a new sport after surgery than to stop one. Percentage of patients doing sports post- compared to preoperative is higher in both groups. Less patients having a TDR complain about technical limitations during practicing sports than fusion patients. Discussion: Despite later resumption of athletic activity TDR seems to be the better surgical treatment of degenerative disc diseases in active patients and athletes due to overall higher sports levels. If long term results can keep up with short time follow ups has to be questioned

Introduction The concept of accelerated degeneration of adjacent disc levels as a consequence of increased stress caused by interbody fusion of the lumbar spine has been widely postulated. Total disc arthroplasty may offer the same clinical benefits as fusion while providing motion that may protect the adjacent level discs from the abnormal and undue stresses associated with fusion. The goal of this study was to prospectively analyse the results of the Maverick Lumbar Disc Prosthesis (Medtronic, USA) at 4 years follow-up. Methods We conducted a prospective analysis of the Maverick Lumbar Disc Prosthesis implanted in the first 50 consecutive patients for the treatment of degenerative disc disease of the lumbar spine resistant to conservative treatment for more than 1 year. 253 Maverick have been implanted in our spine unit and these 50 have the longest follow-up. The outcome data collected included the Oswestry Questionnaire and Visual Analog Scale (VAS) preoperatively and at routine scheduled follow-ups. Radiographic analysis included sagittal balance parameters on standing full length lateral radiographs of the spine and range of motion on flexion/extension dynamic radiographs. 3 European centres were included in the study. The offset on AP x-rays was calculated for all patients and correlated with clinical outcomes. Results There were 32 females and 28 males with an average age of 43, 4 years and average follow-up of 3.1 years (22 to 48 months). The Maverick was implanted at L5S1: 20 cases; L4L5: 17 cases; 3 patients had 2 levels arthroplasty and 10 had a fusion at L5S1 and a prosthesis at L4L5. Clinical success, defined by the FDA as improvement of at least 25% on the Oswestry, was 76% and 81%, at 6 months and 1 year follow-up respectively. The VAS showed an improvement in back pain from 7.1 (+/− 2, 1) pre-operatively to 3.0 (+/− 1.8) post-operatively. Leg pain was significantly higher according to VAS when patients have been previously operated for disc herniation (HD). At the latest follow-up, there was no measurable subsidence of the devices except in one case at L5S1 due to a technical error and no evidence of device migration. The measured range of motion in flexion-extension ranged from 3 to 16 degrees (mean range of motion, 6 +/− 4 degrees). L4–L5 level is more mobile: average 8.4 degrees. With regards to sagittal balance, there was no significant change in any of the variables studied including sacral tilt, pelvic tilt, or overall lordosis after placement of total disc arthroplasty. Only the lordosis at the level above the prosthesis was significantly decreased. The position of the implant on AP and lateral x ray was analyzed and correlated with the clinical results. Less than 19% of offset on AP view had no influence on clinical results. One complication, a ureter injury occurred during the approach in one procedure. One left iliac vein injury occurred per-operatively and treated with vascular clip. One patient with two discs with persistent low back was re-operated for posterior fusion with a significant improvement of pain at two years. This patient had been operated 3 times before for disc herniation and recurrence of HD. Discussion These results of total disc arthroplasty compare favorably with the mid-term clinical outcomes associated with anterior lumbar discectomy and fusion reported in the literature. Unlike fusion however, it appears that the prosthesis has enough freedom of motion to allow the patient to maintain the natural sagittal and spinopelvic balance with radiographic evidence of normal range of motion. However, these early favorable clinical results in addition to the influence on adjacent motion segments can be assessed only after long term follow-up. Previous surgery for HD isn’t the better indication to restore the motion

Purpose: A long spinal fusion across the thoracolumbar region is sometimes applied in scoliosis. Adjacent level degeneration below these constructs has been documented. Treatment with an artificial disc replacement below the fusion has been proposed to prevent degeneration there. There is currently little data detailing the expected biomechanics of this situation. The objective of this study was to evaluate range of motion (ROM) and helical axis of motion (HAM) changes due to one- and two-level Maverick total disc replacement adjacent to a long spinal fusion. Method: A multidirectional flexibility testing protocol with compressive follower preload was used to test seven human cadaveric spine specimens (T8-S1). A continuous pure moment ±5.0 Nm was applied in flexion-extension (FE), lateral bending (LB) and axial rotation (AR), with a compressive follower preload of 400 N. The motion of each vertebra was monitored with an optoelectronic camera system. The test was completed for the intact condition and after each surgical technique:. T8-L4 fusion and facet capsulotomy at L4–L5 and L5-S1;. L4–L5 Maverick;. L5-S1 Maverick. Maverick total disc replacement and fusion with the CD Horizon system was performed. Repeated measures ANOVA was used to analyze changes in ROM and HAM of the L4–L5 and L5-S1 segments. Results: Following L4-L5 Maverick replacement, L4-L5 ROMs tended to decrease slightly (on average from 6.2°±2.8° to 5.1°±3.8° in FE, 1.1°±1.1° to 0.9°±0.5° in LB and 1.3°±0.9° to 1.0°±0.6° in AR). With two-level Maverick implantation, L5-S1 ROMs tended to increase slightly in FE (from 6.6°±2.6° to 7.1°±3.9°), and to decrease slightly in LB (from 1.5°±0.9° to 1.0°±0.3°) and AR (from 1.5°±1.5° to 1.1°±0.6°), compared to the fused condition. As a trend, HAM location shifted posteriorly in FE and AR, and inferiorly in LB following Maverick replacement. However, neither ROM nor HAM at these two segments showed any significant change due to the implantation of one-or two-level Maverick total disc replacement in any of the three directions. Conclusion: The present results suggested that lower lumbar segments with Maverick disc replacement exhibited intact-like kinematics in both extent and quality of motion

The study was designed to observe the patients emotional and physical response to total disc replacement surgery in the cervical spine. A prospective cohort study of patients undergoing Cervical total disc replacement (TDR) surgery at our institution. Surgery was carried for radicular and or axial neck pain. The Activ-C TDR (Aesculap) was used. Pre and post operative data was collected using validated questionnaires. 13 Consecutive patients from Nov 2007 to Aug 2008 were studied. All patients were planned for surgical intervention for symptomatic degenerative cervical disc disease at single or multiple levels. 7 male, 6 female. The Centre for Epidemiological Studies Depression Scale (CES-D) was used to assess the psychological impact. The Neck Disability Index (NDI) and a visual analogue scale (VAS) were used to assess the physical impact of the surgery. NDI shows a significant improvement at 6 and 12 months (p= 0.002 and p=0.02 respectively). The VAS also shows significant improvement at 6 and 12 months (p=0.004 and 0.008 respectively) The CES-D improved but failed to show any significant improvement at either interval. In our patient population surgical intervention with TDR for degenerative disc disease offers significant physical benefit over the short term. This does not correlate with an improvement in their emotional state

School of Mechanical Engineering, University of Birmingham, Birmingham, UK. This study investigated the effects on friction of changing the dimensions of a ball-and-socket Total Disc Arthroplasty (TDA). A generic ball-and-socket model was designed and manufactured based on the dimensions and geometry of a metal-on-metal Maverick (Medtronic, Minneapolis, USA) device. Keeping the radial clearance similar to the Maverick, the ball and socket dimensions varied between 10 to 16 mm and 10.015 to 16.015 mm, respectively, in order to enable the comparison between different dimensions. The implants were made out of Cobalt Chrome Molybdenum alloy, with a surface roughness of 0.05 μm. A Bose spine simulator (Bose Corporation, ElectroForce Systems Group, Minnesota, USA) was used to apply an axial compressive force to the TDA. Axial rotation of ±2° was then applied at various frequencies and the resulting frictional torque measured. The tests were performed under an axial load of 50, 600 and 1200 N and frequencies of 0.5, 1.0, 1.5 and 2.0 Hz, for four different samples of radii 10, 12, 14 and 16 mm (48 combinations in total). The results showed variation of frictional torque in different frequencies for all four samples under constant axial load. It was observed that the frictional torque had the lowest value for the implant with ball radius of 16mm. It might be concluded that the implant with larger ball radius may create less friction and hence offer a longer life

Introduction Current concepts in the treatment of degenerative disc disease include disc replacement. Disc replacement may restore height and lordosis while maintaining motion. This paper reviews the design criteria, biomechanical and biological (wear and safety) testing of the Maverick total disc arthroplasty. The surgical technique and early clinical results of the initial implantations were reviewed (Mathews HH, et al; Spine J. 2004). Methods The Maverick total disc arthroplasty is a semi-constrained, chrome cobalt metal-on-metal, ball and socket design prosthesis designed to resist shear forces. Various prosthetic sizes allow precise end plate coverage to help prevent subsidence and selective restoration of lordosis and disc height. The posterior location of the ball-and–socket articulation approximates the normal centre of rotation. The Maverick disc was subjected to axial compression, cadaveric motion, wear testing, and shock transmission studies. Early clinical outcomes were reviewed. Results Biomechanical testing resulted in no failures, cracks, loss of height or other mechanical damage after subjecting the components to 10 million loading cycles. Cadaveric testing showed maintenance of a range of motion in all planes with no statistically significant (p=.05) differences between the stiffness or range-of-motion measurements in any mode except for extension. Maverick tested at 10 million repetitions of significant bends, estimated to be equivalent to 31.5 years of clinical use, generated only 12 to 14 mm. 3. of debris. This represents approximately 9% of the anticipated debris of a metal-on-metal hip arthroplasty. No difference in shock transmission between metal-on-metal and metal-on-polyethylene prosthesis designs was demonstrated. Clinically at 2 years, at least three-quarters of patients obtained an Oswestry success of 15 points or more usually by 3 months after the procedure. Recovery and improvement was significantly quicker when compared to the historical arthrodesis controls. A few approach-related complications and technical failures have been reported. There have been no implant-related failures. Discussion The most clinically relevant concept in disc replacement may be restoration of spinal balance rather than preservation of motion. Laboratory testing confirms the design rationale of the Maverick disc. Early clinical results are encouraging. Longer term results and more careful study are needed to confirm its efficacy

Background Context: Total disc replacement (TDR) gained enormous popularity as a treatment option for symptomatic degenerative disc disease in the last few years. But the impact of the prosthesis design on the segmental biomechanics in most instances still remains unclear. As TDR results in a distraction of the capsuloligamentous structures, the disc height seems to be of crucial importance for the further biomechanical function of the operated level. Yet the biomechanical role of disc height after TDR still remains unclear. Purpose: The purpose of study was to evaluate the influence of prosthesis height after total disc replacement on: 1) the sagittal balance and 2) the range of motion. Study design: A radiological and an in-vitro biomechanical study. Method: 6 human, lumbar spines L4–L5 were tested in vitro.The segmental lordosis of the specimen were measured on plain radiographs and the range of motion was measured for all six degrees of freedom with a previously described spine tester. The segmental lordosis and the range of motion at level L4–L5 was evaluated for following settings: 1) intact state 2) after implantation of a prosthesis with 5mm endplate 3) after implantation of a prosthesis with 7mm endplate. The prosthesis used was a prototyp and had a constrained design with a ball and socket principle. Results: Even the implantation of the lowest possible prosthesis height (5mm endplate) resulted in an increase of segmental lordosis (intact: 6.9; 5mm endplate: 8.8; p=0,027). Using a higher prosthesis (7mm endplate) further increased the segmental lordosis (10.5, p=0.041). The implantation of the lowest prosthesis resulted in significant increase of movement capability compared to the intact status for flexion-extension (8.6 vs 11.4; p=0.046) and axial rotation (2.9 vs 5.1; p=0.028). Lateral bending did not changed significantly (9.4 vs 8.6; p=0.345). The implantation of the higher prosthesis (7mm endplate) resulted in similar movement capability compared to intact status for flexion-extension (8.4 vs 8.6; p=0.116) and axial rotation (3.3 vs 2.9; p=0.600). Lateral bending decreased significantly compared to the intact status (5.1 vs 8.6; p=0.028). Conclusion: Total disc replacement with the lowest prosthesis height inherently increases segmental lordosis. Further increase of disc height results in a significant enhancement of segmental lordosis by decreasing the range of motion for all three degrees of freedom. Yet, methods for scheduling the ideal disc height preoperatively, to provide a physiological lordosis thereby maintaining physiological range of motion postoperatively, seems not to be established already

Study Design and Objectives: The aim of this prospective study is to analyze clinical results of lumbar total disc arthroplasty according to the MRI evaluation of the disc degeneration. Summary of Background Data: Disc degeneration of the lumbar spine is associated with different signs on MRI study. Such lesions can be treated by spinal fusion or disc arthroplasty, and no strong therapeutic consensus is available at the moment. Non-fusion techniques have been developed for the treatment of disc degeneration disease and are able to preserve intervertebral mobility with good clinical results. Materials and Methods: 221 patients with a mean age of 42 years have been included in this study. 107 patients were classified Modic 0, 65 Modic 1 and 49 Modic 2. Clinical evaluation (Oswestry Disability Index, Lumbar and Radicular visual analogic score) was performed preoperatively and at 3, 6, 12 and 24 months postoperatively. Results: Mean follow-up of the series was 30 months [24–72 months]. A significant clinical improvement (p< 0, 05) was observed on each criteria between the preoperative evaluation and last follow-up. On the multivariate analysis between the three groups, a significant difference was observed, with better clinical results in the group classified Modic 1. Conclusion: Total lumbar disc arthroplasty provide a significant clinical improvement in patients with disc degenerative disease with a minimum follow-up of two years. Best results were achieved in the group of patients classified as Modic 1 on the MRI evaluation. These results are applicable for the selection of indications of total disc arthroplasty and also for the patient information preoperatively

Lumbar Total Disc Replacement (LTDR) is an alternative to fusion for the surgical management of discogenic back pain not responding to conservative therapy. Theoretical advantages include preservation of motion and possible reduction in adjacent segment degeneration. The aim is to review the early results of LTDR in an Auckland private practice. A prospective study was carried out on 32 consecutive patients treated with LTDR. Discogenic back pain was confirmed with plain radiographs, MRI and CT lumbar discogram. The Charité TDR was used in 19 patients and A-MAV in 13. Follow-up was to a minimum of two years. Patients completed Modified Roland Questionnaires (MRQ), Visual Analogue Pain Scores (VAPS) and Lower Back Outcome Scores (LBOS) pre and post-operatively. Patients’ notes and radiographs were reviewed. All outcomes measures improved significantly. Mean MRQ scores improved from 14.2 to 6.4 and 4.8 (at one and two years respectively). Mean VAPS improved from 5.3 to 2.5 and 1.7. Mean LBOS improved from 33 to 52 and 57. 84% had radiographic evidence of motion at the level of the prosthesis. There were four major complications. A retroperitoneal haematoma, an incisional hernia, a ureteric stenosis and subsidence of the prosthesis each occurred in separate patients. These all occurred in the first ten patients of the study and were related to the approach. There were no major thrombo-embolic or infective complications and no revision surgery was required. LTDR is a safe and effective surgical treatment of discogenic back pain. There is however, a steep learning curve with regard to the approach and a higher risk of complications during this time. Initial results are encouraging, but longer term follow-up needs to be performed

INTRODUCTION. Lumbar total disc replacement (TDR) is an alternative treatment to avoid fusion related adverse events, specifically adjacent segment disease. New generation of elastomeric non-articulating devices have been developed to more effectively replicate the shock absorption and flexural stiffness of native disc. This study reports 5 years clinical and radiographic outcomes, range of motion and position of the center of rotation after a viscoelastic TDR. Material and methods. This prospective observational cohort study included 61 consecutive patients with monosegmental TDR. We selected patients with intermediate functional activity according to Baecke score. Hybrid constructs had been excluded. Only cases with complete clinical and radiological follow-up at 3, 6, 12, 24 and 60 months were included. Mean age at the time of surgery was 42.8 +7.7 years-old (27–60) and mean BMI was 24.2 kg/m² +3.4 (18–33). TDR level was L5-S1 in 39 cases and L4-L5 in 22 cases. The clinical evaluation was based on Visual Analog Scale (VAS) for pain, Oswestry Disability Index (ODI) score, Short Form-36 (SF36) including physical component summary (PCS) and mental component summary (MCS) and General Health Questionnaire GHQ28. The radiological outcomes were range of motion and position of the center of rotation at the index and the adjacent levels and the adjacent disc height changes. Results. There was a significant improvement in VAS (3.3±2.5 versus 6.6±1.7, p<0.001), in ODI (20±17.9 versus 51.2±14.6, p<0.001), GHQ28 (52.6±15.5 versus 64.2±15.6, p<0.001), SF 36 PCS (58.8±4.8 versus 32.4±3.4, p<0.001) and SF 36 MCS(60.7±6 versus 42.3±3.4, p<0.001). Additional surgeries were performed in 5 cases. 3 additional procedures were initially planified in the surgical program: one adjacent L3-L5 ligamentoplasty above a L5S1 TDR and two L5S1 TDR cases had additional laminectomies. Fusion at the index level was secondary performed in 2 L4L5 TDR cases but the secondary posterior fusion did not bring improvement. In the 56 remaining patients none experienced facet joint pain. One patient with sacroiliac pain needed local injections. Radiological outcomes were studied on 56 cases (exclusion of 5 cases with additional surgeries). The mean location centers of the index level and adjacent discs were comparable to those previously published in asymptomatic patients. According to the definition of Ziegler, all of our cases remained grade 0 for disc height (within 25% of normal). Discussion. The silent block design of LP-ESP provides an interesting specificity. It could be the key factor that makes the difference regarding facets problems and instability reported with other implants experimentally or clinically. Unfortunately no other comparative TDR series are available yet in the literature. Conclusion. This series reports significant improvement in mid-term follow up after TDR which is consistent with previously published studies but with a lower rate of revision surgery and no adjacent level disease pathologies. The radiographic assessment of the patients demonstrated the quality of functional reconstruction of the lumbar spine after LP ESP viscoelastic disc replacement

Introduction Using a non-human primate model, the purpose of this in-vivo investigation was to evaluate the efficacy of porcine small intestine submucosa (PSIS) for anterior longitudinal ligament replacement and as an anti-adhesion barrier following total disc arthroplasty. Success criteria were based on post-mortem vascular adhesion tenacity scores, biomechanical, histological and immunohistochemical analyses. Methods A total of ten mature male baboons (Papio cynocephalus) were included in the current study and followed for a period of six-months post-operatively. Each animal underwent an anterior transperitoneal approach followed by a total disc arthroplasty procedure at L5-L6 using one of the following treatments: (1) Charité Disc Prosthesis alone (n=5) or (2) Charité Disc Prosthesis + PSIS (n=5). Following anterior annular and anterior longitudinal ligament (ALL) resection, complete diskectomy and endplate decortication, the Charité Device (Size 1) was implanted according to the manufacturer’s specifications. The PSIS material (40mm x 30mm width) was secured across the operative site using surgical bone staples with the abluminal side oriented towards the bone. Post-mortem analysis included vascular adhesion tenacity scores (0–5), histopathology of the operative site ALL, non-destructive biomechanical testing and histomorphometry. Results All animals survived the operative procedure and post-operative interval without significant intra- or peri-operative complication. Vascular adhesion tenacity scores were markedly lower for the PSIS treatments (14/25) versus the Charité alone (20/25) (p=0.057). Gross histopathological analysis demonstrated disorganized collagenous matrix anteriorly spanning the disc arthroplasty site in 4/5 (80%) of the PSIS specimens compared to 2/5 (40%) for the Charité alone treatments. Plain film radiographic analysis showed no lucencies or loosening of any prosthetic vertebral endplate. Multi-directional flexibility testing demonstrated increased range of motion for both treatment groups under axial rotation and decreased motion in lateral bending when compared to the intact spine condition (p< 0.05). The neutral zone values were significantly higher in axial rotation and flexion extension for the both treatments (p< 0.05), with no differences in lateral bending. Discussion Using a non-human primate model, the current study investigated in-vivo response to PSIS following total disc arthroplasty. Surgical application of the PSIS appears to reduce great vessel adhesion and improve regeneration of collagenous tissues at the operative disc space. However, there were no differences in the operative segment range of motion or neutral zone when comparing the two treatments. The current study serves as a basic scientific basis for ongoing clinical investigations into the use and efficacy of PSIS material following total disc arthroplasty

Purpose: To investigate subsidence of the Charite total disc arthroplasty (TDA) and to identify if a discrepancy between vertebral endplate and the Charite footprint predispose to subsidence. Methods: Between July 2001 and May 2008 64 patients underwent a Charite TDA (DePuy Spine, Raynham, MA). They were prospectively followed at 3, 6, 12 months, and once a year thereafter. The following measurements were performed on the replaced motion segment using a lateral radiograph:. The anterior-posterior (AP) dimension of the end plates. Amount of subsidence. The distance between the TDA and the posterior and anterior borders of the vertebra bodies (to represent the extent of uncoverage of the endplate by the TDA). The AP dimension of the TDA metal endplate. The ratio between the actual and radiographic AP length of the metal endplate was calculated and utilized as the correction factor for the error of magnification on all other radiographic measurements. Results: At L5-S1 the mean subsidence was 1.87 mm and occurred exclusively at the posterior part of the inferior end plate of L5. The mean posterior uncoverage was 3.5 mm (L5) and 0.27 mm (S1). At L4–L5 the mean subsidence was 1.48 mm (L4) and 0.56 mm (L5). Posterior uncoverage of L4 and L5 vertebrae were 4.81 and 2.22 mm, respectively. Subsidence of more than 1 mm was present in all cases where the posterior uncoverage of the end plate with the TDA was more than 2 mm (odds ratio: 5.7). Subsidence was non – progressive in all cases. An anatomic mismatch exists between L5 and S1 endplates in the AP dimension; in more than half the patients S1 is shorter than L5. Conclusion: The radiographic measurements suggest an increased likelihood of subsidence with more than 2 mm of posterior uncoverage of the end plate by the TDA. The endplate AP length of S1 is frequently less than that of L5. Implant selection based on the smaller S1 endplate may produce worrisome uncoverage of the L5 inferior endplate leading to an increased risk of subsidence and possible catastrophic failure. TDA design should afford modularity to compensate. No financial benefits or funding has been received for the completion of this study

Background Context: One of the main postulated basic principles of total disc replacement (TDR) is the preservation of flexion/extension ability. In neutral position the ideal disc prosthesis should not stay in maximal possible extension which would imply an impingement of the prosthesis. An impingement would cause shear strains on the prosthesis endplates which probably accelerate loosening. Moreover an additional extension ability from the neutral position would indicate no impingement in the facet joints in neutral position and a physiological movement capability. Purpose: The purpose of study was to evaluate a possible impingement of the prosthesis or facet joints after TDR in neutral position. Study design: Prospective evaluation of radiological outcome measures after total disc replacement. Patient sample: The patients (19 female, 10 male) ranged from 29 to 56 years of age (mean: 42.46.5 years). The mean follow up interval averaged 13.2 months (range: 6 – 35 months). The diagnosis of degenerative disc disease was confirmed by MRI (black disc) and discography (positive „Memory pain“). Pain relief after facet joint infiltration was an exlucsion criteria. All patients had a single-level disc replacement (Prodisc II, Spine Solutions) with the same angulation (6). Outcome measures: Evaluation of a possible impingement of the prosthesis and impingement of facet joints in neutral position. Methods: A computer based analysis of pre- and postoperative lateral X-rays in neutral position and dynamic x-rays. The angulation of prosthesis in neutral position and the extension ability in dynamic x-rays were measured. Results: 15 patients showed no extension ability on dynamic x-rays and 10 of these 15 patients had an impingement with maximum extension of the prosthesis on x-rays in neutral position. In the remaining 14 patients the extension ability averaged pre-/postoperatively 2.3/1.3 (p=0.115). In 4 of the 14 patients the pros-thesis showed an impingement in maximum extension and in 10 patients the prosthesis was not in maximum possible extension. Conclusion: Due to the constrained design of the Pro-Disc an impingement is possible and was recognized in nearly 30% of the cases. The imbalance of flexion vs extension bending moments with increase in extension bending moments due to resection of the anterior longitudinal ligament and anterior anulus seems to be a possible explanation. It still remains unclear if an impingement will result in facet joint protection or will trigger a loosening of the implant. A prosthesis design which preserves the anterior longitudinal ligament would be probably a possible solution

Anterior decompression and fusion has been standard treatment for cervical disc herniation and myelopathy with disc degeneration. Since cervical total disc replacement (TDR) has been introduced with early favorable results and ideal mechanism, it has gained its popularity recently. But varying degrees of heterotopic ossification (HO) around the operated segment have been noted in the literatures. The theoretical advantages of TDR are the maintenance of intervertebral motion and prevention of adjacent segment degeneration. It is questionable that if HO occurs after TDR, mobility of operated segments would be restricted then clinical outcome worse. Purpose of this study is to determine prevalence of HO and to investigate that the presence of HO would limit motion and subsequently negatively affect clinical outcome following cervical TDR. We analyzed 29 patients (30 levels) who were treated with cervical TDR by 2 spine specialists using 4 types of prostheses (Mobi-C: 13 levels, ProDisc: 10, Bryan: 5, Prestige LP: 2) consecutively from July 2004 to June 2007. Postoperative mean follow-up period was 21.4 (12–36) months. We assessed presence of HO and segmental ROM radiographically and clinical outcome by VAS, ODI after 1.5, 3, 6 months, and every year postoperatively in principle. All subjects were divided by 3, which were group A (no HO, McAfee class 0), group B (class I and II), and group C (class III and IV), then compared with each other. HO was detected on 14 levels (46.7%) in the 30 levels after at mean of 8.2 (4–18) months after operation. There were 15 levels(53.3%) of group A (no HO, class 0), 7 levels of group B (class I HO:3, II: 4), and 7 levels of group C (class III: 3, IV: 4). Segmental flexion-extension ROM of group A was 10.1 (5.6–16.2)°, group B is 8.3 (3.5–14.4)°, and group C is 3.1 (0.0–6.6)° (p< 0.001, multiple comparison test with post hoc Bonferroni correction). And no difference in the clinical outcomes, VAS and ODI, was found compared with each other among group A, B, and C (p> 0.05). Nonetheless, longer term follow-up should be performed to investigate whether clinical outcomes would be changed and occur adjacent level degeneration as time goes on. In addition, further study for prevention of HO may be needed as in HO of other joint replacement surgery not to lose superior mechanism to fusion treatment

To determine the cost-effectiveness of Lumbar Total Disc Replacement (LTDR) with circumferential spinal fusion surgery. Cost utility analysis. We prospectively reviewed a cohort of 32 consecutive patients who underwent LTDR between 2004 and 2008 with a mean follow-up for 3.75 years. Identical data was compared to a similar group of patients (n=37) who underwent fusion in our institution. Oswestry Disability Index, visual analogue scale, quality of life (SF-36) and NHS resource use. Cost-effectiveness was measured by the incremental cost per quality-adjusted life year (QALY) gained. QALY gains were estimated from SF-36 data using standard algorithms. There was no significant intergroup difference in the ODI, VAS and SF-36 pre and post-op. Both treatments produced statistically significant and equivalent improvements in mean health state utility at the 24-month follow-up (0.078 for LTDR, 0.087 for fusion). Costs were significantly lower with LTDR than with fusion due to a shorter mean procedure time (193.6 vs 377.4 minutes) and shorter length of stay (5.8 vs 7 days). The mean cost difference was £2,878 per patient. At 2 years, the cost per QALY gain of the lower-cost option (LTDR) was £48,892 although the cost effectiveness ratio would fall to below £30,000 if it is assumed that the patient benefits of LTDR last for at least 4 years. Both treatments led to significant improvements in patient outcomes which were sustained for at least 24 months. Costs were lower with LTDR which is effective and a more cost-effective alternative

Purpose: To investigate subsidence of the Charite total disc arthroplasty (TDA) and to identify if a discrepancy between vertebral endplate and the Charite footprint predispose to subsidence. Method: Between July 2001 and May 2008, 69 patients underwent a Charite TDA (DePuy Spine, Raynham, MA). They were prospectively followed at 3, 6, 12 months, and once a year thereafter. The following measurements were performed on the replaced motion segment using a lateral radiograph:. The anterior-posterior (AP) dimension of the end plates. Amount of subsidence. The distance between the TDA and the posterior and anterior borders of the vertebra bodies (to represent the extent of uncoverage of the endplate by the TDA). The AP dimension of the TDA metal end-plate. The ratio between the actual and radiographic AP length of the metal endplate was calculated and utilized as the correction factor for the error of magnification on all other radiographic measurements. Results: At L5-S1 the mean subsidence was 1.87 mm and occurred exclusively at the posterior part of the inferior end plate of L5. The mean posterior uncoverage was 3.5 mm (L5) and 0.27mm (S1). At L4-L5 the mean subsidence was 1.48 mm (L4) and 0.56 mm (L5). Posterior uncoverage of L4 and L5 vertebrae were 4.81 and 2.22 mm, respectively. Subsidence of more than 1 mm was present in all cases where the posterior uncoverage of the end plate with the TDA was more than 2 mm (odds ratio: 5.7). Subsidence was non – progressive in all cases. An anatomic mismatch exists between L5 and S1 endplates in the AP dimension; in more than half the patients S1 is shorter than L5. Conclusion: The radiographic measurements suggest an increased likelihood of subsidence with more than 2 mm of posterior uncoverage of the end plate by the TDA. The endplate AP length of S1 is frequently less than that of L5. Implant selection based on the smaller S1 endplate may produce worrisome uncoverage of the L5 inferior endplate leading to an increased risk of subsidence and possible catastrophic failure. TDA design should afford modularity to compensate