Purpose of the study: The theoretical usefulness of a disc prosthesis in comparison with arthrodesis would be to restore physiological segmental motion without perturbing the kinematics of the adjacent levels. The purpose of this study was to determine the rotation centers of the lumbar segments before and after implantation of a disc prosthesis with a mobile insert (Mobidisc™). Material and methods: Lateral flexion and extension views in the sitting position with a stabilized pelvis were obtained before and after implantation of the lumbar disc prosthesis in 32 patients. Spineview™ was applied to the digitalized images for semi-automatic recognition of the vertebral body contours and calculation of the rotation centers. The detection threshold for this automatic system was 5° motion. Results: Rotation centers were difficult to determine preoperatively because of the absence of mobility. A pathological position was found for three patients. Postoperatively, at three and twelve months, the position was «physiological» in 13 patients, in the posterior half of the disc or inferior body near the vertebral end plate. IN 14 patients, the center could not be determined because motion measured 5° or less. For three patients, the center was too anterior on a prosthesis implanted to anteriorly. There were no changes in the rotation centers for the adjacent levels. Discussion: Demonstration of an abnormal rotation center could be an additional indication of presumed instability. In certain cases, a disc prosthesis appears to restore the physiological rotation center. But the position and the thickness of the implant can influence their localization. Conclusion: Restoration of a physiological rotation center for the instrumented intervertebral segment and the absence of change in the rotation centers for the adjacent centers are arguments in favor of disc prosthesis for reducing the incidence of osteoarthritic degradation of adjacent discs in comparison with fusion, under the condition that the implantation and the size are correctly adapted

We present data relating to the Bryan disc arthroplasty for the treatment of cervical spondylosis in 46 patients. Patients with either radiculopathy or myelopathy had a cervical discectomy followed by implantation of a cervical disc prosthesis. Patients were reviewed at six weeks, six months and one year and assessment included three outcome measures, a visual analogue scale (VAS), the short form 36 (SF-36) and the neck disability index (NDI). The results were categorised according to a modification of Odom’s criteria. Radiological evaluation, by an independent radiologist, sought evidence of movement, stability and subsidence of the prosthesis. A highly significant difference was found for all three outcome measurements, comparing the pre-operative with the post-operative values: VAS (Z = 6.42, p < 0.0001), SF-36 (mental component) (Z = −5.02, p < 0.0001), SF-36 (physical component) (Z = −5.00, p < 0.0001) and NDI (Z = 7.03, p < 0.0001). The Bryan cervical disc prosthesis seems reliable and safe in the treatment of patients with cervical spondylosis

Purpose of the study: Discectomy-anterior fusion has proven efficacy for many diseases of the cervical spine. Nevertheless, the loss of motion and the over-solicitation of adjacent levels are arguments in favor of disc replacement. This prospective study examined the early clinical and radiological results obtained in the first 41 patients treated with a new cervical disc prosthesis, Mobi-C. Material and methods: A prospective multicentric clinical and radiological study is being conducted to analyze the safety and efficacy of Mobi-C for degenerative disease. Indications are radiculopathies due to discal herniation or foraminal osteophytic stenosis involving one or two levels from C3 to T1. An independent observer reviewed the patients. SF36, the Neck Disability Index, and a visual analogue scale for pain as well as radiographic mobility were noted. Results: Mean age was 42 years (range 31–56 years). There were 23 men and 18 women. Eight patients had two disc replacements. Mean follow-up was six months (range 3–10 months). Mean operative time was 65 min, similar to operative time for fusion. Blood loss was 90 ml. NSAID were prescribed for the first 15 days. There were no intraopeartive complications and no revisions. Postoperative complications were minimal. There were no specific complications related to the prosthesis, its insertion or its function. The function and quality-of-life scores showed a significant improvement at last follow-up. Radiographically, motion was also improved in most patients. Discussion: The early results on the safety and efficacy of this new cervical prosthesis are promising. Primary stability has been excellent and there have been no specific prosthesis-related complications. Furthermore, several operators have mentioned how easy it is to insert the Mobi-C. Conclusion: The clinical results in terms of pain and function as well as the radiological results have been satisfactory both at the early and at the later assessments. Insertion of this prosthesis is a simple process, similar to insertion of an intersomatic cage, elements arguing in favor of a cervical disc prosthesis. Further follow-up will be needed to assess the long-term efficacy and possible effect on prevention of accelerated degeneration of the adjacent discs

Introduction: There is a great deal of interest in intervertebral disc arthroplasty. These devices have been used in Europe for more than 10 years. There have been several reports published on the European results when using the SB Charité III (link) prosthesis and good results have been reported in 63% to 79% of patients. 1,. 2,. 3. The purpose of this prospective study was to evaluate surgical outcome following implantation of an artificial disc. Methods: The SB Charité III device has two cobalt chromium plates with a polyethylene core between them. Motion occurs through articulation between the concave/convex surfaces of the plates and core. The disc prosthesis is implanted using the same approach as used for anterior lumbar interbody fusion procedures. It comes in multiple sizes to accommodate variations in individual patient size. The disc has been implanted in 39 patients in our clinic. This group includes 19 males and 20 females (mean age 39.8 years, range 26 to 54 years). The primary study inclusion criteria were single-level symptomatic disc degeneration, failure of at least six months of non-operative treatment, and no previous surgery at the operated segment. Outcome measures included neurological examination, radiographic assessment, Oswestry Low Back Pain Disability Questionnaire, visual analog scale (VAS) assessing pain, SF-36, and work status. Data were collected pre-operatively, and at six weeks, three, six, and 12 months post-operatively. To date, 22 patients have reached the 12 months follow-up point. Results: Overall, patients demonstrated improvement in the self-reported outcome measures. The mean VAS score improved approximately 50% at the six weeks follow-up and this improvement was maintained during subsequent follow-up. The Oswestry scores improved 37% at six weeks follow-up and had improved by 50% at subsequent follow-ups. Radiographic assessment revealed no cases of device displacement or migration. Complications were comparable to those reported for anterior lumbar interbody fusion. There have been no cases of device failure. Discussion: The results of this prospective study, using patient self-report questionnaires, demonstrated good clinical outcome. There was a significant improvement noted six weeks post-operatively that was maintained during the follow-up visits. The disc prosthesis can be implanted safely, with complications similar to those encountered with anterior lumbar interbody fusion. As with any surgical procedure, long-term prospective follow-up is needed and data will be collected as these patients reach 24 months follow-up

Purpose of the study. In a recent study, O'Leary et al. [2005] reported their observations on the patterns of Charité disc prosthesis motion under physiologic loads. The purpose of this study was to investigate whether the motion patterns observed in the in vitro model are replicated in clinical practice. Methods. 55 patients with implanted SB Charité 111 artificial lumbar discs were subjected to flexion extension x-rays. Two consultant spinal surgeons and a neuro-radiological consultant were asked to classify the pattern of motion in the clinical subjects based on the patterns observed in the in vitro model. The results were recorded independently then collated. Following this first round of observations an algorithm was devised and the method of measurement was standardised. Summary of findings: There was modest correlation amongst the three observers in distinguishing motion from nonmotion (Kappa 5.6). There was less agreement on what type of motion was present. On both counts using the algorithm there was no correlation. The clinical study based on patients' flexion-extension radiographs identified the following patterns of prosthesis motion:. angular motion between both the upper and lower endplates and core, with visual evidence of core motion;. angular motion predominantly between the upper endplate and core, with little visual evidence of core motion;. lift-off of upper prosthesis endplate from core or of core from lower endplate;. core entrapment and deformation; and. no motion. There are difficulties associated with the interprtation of these using only flexion extension views. Conclusions. In devising artificial discs the requirement would be to replicate spinal motion as closely as possible. O'Leary et al have found non-physiological motions in in vitro models. These have been found in this clinical study but interobserver correlations were far from conclusive. Demonstrating non physiological patterns may have important implications for outcome

Objective: Movement in an artificial disc would be assumed to be a necessary function of the disc. The purpose of this study was to establish whether, if any, relationship existed between movement in the artificial disc and outcome. Subjects: 25 patients who had received an artificial disc prosthesis were assessed using radiological methods. Despite many vagaries in the measurement of X-rays, fluoroscopy was used to assess gross movement and end of flexion/extension views used to measure degrees of motion. Outcome measures: Oswestry disability score. Results: A very clear relationship has been established between motion in the artificial disc and outcome. Conclusions: It is likely that spinal fusion will ultimately give way to disc replacement. Although spinal fusion has been shown in the Swedish spine series to produce good outcomes for significant numbers of patients, it remains to be seen whether the retention of motion will enhance outcome in low back pain patients. This series suggests that the retention of motion is an important component in the outcome of surgery in back pain sufferers

Introduction: The Charite Mark 3 disc prosthesis has been used by the senior author for ten years. There has always been a question mark over the wear properties of the high density polyethylene spacer used in this prosthesis. Methods: Ten patients who have received Charite implants, eight, nine and ten years ago were subjected to helical CT scanning. Slices at 3 mm. intervals were taken across the prosthetic levels. Fifteen prostheses were studied. Four clinicians, two of whom were radiologists and one a spinal fellow, assessed the CT scans against a standard protocol. Since the original heights of the prostheses were known, it was possible to measure prosthetic height and therefore get an estimate of wear. In addition, areas of osteolysis around the prostheses were estimated, again as a sign of wear. Results: Remarkably little wear or wear debris was noted around the 15 prostheses. Conclusions: Although this is a small series, it confirms that the medium-term performance of this prosthesis as far as wear is concerned is good

Introduction The early clinical results of cervical disc replacement surgery are encouraging but the in vivo kinematics of prostheses remains poorly understood. Two recent published reports suggest that use of a prosthesis with an unconstrained (over normal range of motion) biconvex nucleus (Bryan Cervical Disc® – Medtronic Sofamor Danek, Memphis, TN) can be associated with post-operative segmental kyphosis. This study examines post-operative kyphosis and segmental imbalance following cervical disc replacement using the Bryan Cervical Disc prosthesis and factors which may influence this. In particular, the influence of change in disc space height as a result of surgery was studied. Methods 67 patients underwent prosthetic disc replacement by one of three surgeons (19, 25 and 23 patients, respectively) using the Bryan prosthesis. 46 single, 20 double and 1 triple level were operated. Neutral pre- and post-op erect and intra-operative x-rays were examined manually and using digital image analysis software (Medical Metrics, Inc. Houston, TX). Possible contributing factors to segmental alignment were studied including: pre-op alignment, angle of prosthesis insertion, disc space degeneration and sacrifice of the posterior longitudinal ligament (PLL). Particular attention was given to changes in disc space height and factors which may influence this. Inter- and intra-observer agreement was assessed. Non-parametric tests were used for assessment of categorical and skewed continuous variables. Multivariate linear regression was used to adjust significant correlation coefficients. Significance was set at p< 0.05. Results The median pre-op focal lordosis of +0.5° (range: 21 to −14°, −ve = kyphotic) changed by −1° (+14 to −17°), to post-op: 0° (+11.5 to −16°). There was a significant difference in the median change in focal lordosis for surgeon 1 (−3°) vs. surgeons 2 & 3 (−1°) (p< 0.005) and in the loss of disc space height. Median loss of disc space height for surgeon 1 was 22% vs. 8% for surgeons 2 & 3 (p< 0.002). Correlation co-efficient (Spearman) for change in disc space height vs. change in disc space angulation was 0.67 (p< 0.0001). No single pre- or intra-operative factor was found to clearly correlate with subsequent loss of disc space height apart from a trend towards a weak correlation with the angle of prosthesis insertion (r=0.24, p=0.06). Discussion The median change (loss) in focal lordosis was −1.5° but there was considerable range: from +14° to −17°. Attempts to identify contributing factors suggest that a number may be involved but there did appear to be a highly significant correlation between loss of disc space height following surgery and subsequent focal kyphosis. While the difference in outcomes between Surgeon 1 and Surgeons 2 & 3 is probably not clinically significant, it does suggest that intra-operative factors such as the angle of prosthesis insertion may be important. We are continuing to study these factors

Fusion has been the surgical reference for treating degenerative disc disease, nevertheless in the last two decades the recognition of it’s inconvenients, such as the degenerescence of the adjacent level, the growing demand for a better life quality by the patients and the evolution of the knowledge regarding the biomechanics of the spine and of the intervetebral disc itself, have stimulated the development of new technologies for the treatment of DDD among which the Disc Replacement.

In this symposium will be analysed the biomechanics of the disc and disc replacement, enhancing the already known benefits of the movement preservation, by discussing the different philosophies of the available systems: non-constraint; semi-constraint; and constraint.

The analysis of the overview results in the literature of fusion in comparison with disc replacement will also proportionate a fundamental actualization when deciding over the current perspectives in the treatment of DDD, considering the treatment alternatives developed in the meanwhile.

The disc replacement is an actual challenge with believers all over the world as an important step forward towards better life quality of patients with incapacitant low back pain. But with indications and limits that must be well known. Besides that it’s a demanding technique with potential risks associated and that demands specialization in this domain for its practice.

Always considering the different phases of evolution of the DDD, which can occur simultaneously in the same patient, different therapeutics solutions are considerate and which application deserves a profound reflexion according to the diagnosis characteristics, its staging, the ponderation of risks and benefits and as well its socioeconomics consequences.

Sixty-one lumbar disc replacements in 50 consecutive patients were performed between June 2001 and October 2002. The mean age of the patients was 42.42 years (24 to 61). All presented with mechanical back and/or leg pain. The primary diagnosis was degenerative disc disease. Three patients underwent fusions of another level during the same operation. Seven patients presented with adjacent level disc disease after previous instrumented posterolateral fusion.

The mean postoperative hospital stay was 3.6 days (2 to 8). One patient with a double-level disc replacement and misplacement of the proximal prosthesis underwent revision surgery three days later. Six patients had subsidence on one of the endplates, all within six weeks postoperatively. All but one patient went back to their previous occupation at a mean time of 26 days (7 to 91).

Patients completed questionnaires at 3, 6, 12 and 24 months postoperatively. In the latest follow-up questionnaire, 47 patients said they were satisfied or very satisfied. Forty-five patients would undergo the same operation again or recommend it to friends, two patients were uncertain and two indicated they would not undergo the procedure again. One patient from another country was lost to follow-up, but a telephonic enquiry six months after surgery suggested that he was doing well.

Although our follow-up period is short, the clinical results compare favourably to those in the literature. The rate of immediate subsidence, which seems to be linked to the anchoring teeth, is of concern.

Introduction: The artificial disc consists of proprietary polyolefin rubber core bonded between two titanium endplates. It has been developed for the treatment of symptomatic disc degeneration with the aim of providing segmental stability and motion following wide disc space clearance. It was designed to have similar properties to a normal adult human intervertebral disc when working in conjunction with the retained anulo-vertebral tissues and the supporting musculoligamentous system.

Methods: Over 120 discs were used to biomechanically characterize the Device. Range of motion tests were designed and performed to measure the axial compression, torsional, and shear stiffness of the artificial disc and to compare this with the known values for the human lumbar disc. Pullout test was performed to evaluate the immediate and short-term stability of the inserted device by assessing the mechanical resistance to pullout or expulsion. To assess the ability of the implant to withstand average daily living loads throughout its predicted life, compression and compressive shear fatigue testing were performed.

Discussion: The device was found to replicate many of the physiologic characteristics of the in-vivo FSU. The quasi-static testing showed the device to have higher strength values than the highest in-vivo loads and displacements. Fatigue testing showed the smallest device endurance limit of 3,500N at ten million cycles.

The results demonstrate that the failure modes of the device contain sufficient safety margins to support the use of the device in a prospective clinical study.

Introduction

Current artificial discs include 1 or 2 bearing surfaces, providing 3 or 5 degrees of freedom. The ESP® is a one-piece e implant made of silicon and polycarbonate -urethane securely fixed to titanium endplates. It allows limited rotation and translation with elastic return. This cushion without fixed rotation center achieves 6 degrees of freedom including shock absorption. This objective of this study was to evaluate the safety and efficacy of the concept in a prospective nonrandomized trial.

Introduction: Current total disc prostheses are 2- or 3-pieces devices, including 1 or 2 bearing surfaces, and providing 3 or 5 degrees of freedom but with no, or very little, resistance. The ESP^® is a one-piece deformable implant made of silicon and polycarbonate polyurethane elastomer securely fixed to titanium endplates. It allows limited rotation and translation with elastic return. This cushion without fixed rotation center achieves 6 degrees of freedom including shock absorption. An earlier attempt to use elastomers (Acroflex^®) failed clinically due to the polymer. This highlights the need for accurate in-vitro fatigue testing and clinical evaluations.

Methods: In-vitro fatigue testing with more than 40 millions cycles were performed on different samples for compression, flexion-extension bending, lateral bending, torsion and shear. A prospective trial was initiated in 2004 for L3L4, L4L5 and L5S1 levels. Total disc replacements have been performed in 153 lumbar levels through extra-peritoneal mini-invasive anterior approach

Results: After in-vitro testing, microscopic examination showed that the polymer core remained unchanged without evidence of cracking or other degradation. Gravimetric analysis revealed insignificant changes in weight. The geometrical characteristics and the cohesion of the implants remained stable. After 3 years clinical experience, there was no device related complication, except one early revision for a post-traumatic implant migration. VAS and ODI scores improvements were equivalent to other published series.

Discussion and Conclusion: In-vitro fatigue testing and short term results of the innovative ESP^® prosthesis demonstrate the reliability of the concept. The results are equivalent to other series with conventional implants.

Introduction The use of unconstrained artificial cervical disc replacement (specifically the Bryan ® prosthesis) allows maintenance of normal cervical motion (unlike conventional fusion techniques) with the goal of alleviating neck and arm pain associated with spondylotic radiculopathy.

As a relatively new technique, there is little in the literature regarding patient satisfaction with this device and there are no long term trials defining the most appropriate indication for this device nor benefits over alternative and more conventional procedures such as discectomy and fusion. This study aimed to quantify the degree of disability and functional limitation in patients selected for Bryan disc replacement both pre-operatively and from 3 months post-operatively.

Methods The Oswestry Disability Index (ODI) and the SF36 Index were both used, being robust and reproducible tools in this setting. Patients completed questionnaires pre-operatively and from 3 months post-operatively. From 1 to 3 Bryan disc prostheses were implanted in the cervical spine at each operation. Post-operative index scores were compared with the pre-operative scores for 45 patients who completed all questionnaires, from a total of 47 operated patients in one practice (97% response, 69 total implants).

Results Patients reported a decrease in measured disability and an increase in general functioning and wellbeing after Bryan cervical disc replacement. Where 100% represents total and complete disability, the mean ODI improved from 43.65% pre-operatively (95% confidence interval 37.9 – 49.4) to 19.4% (14.0 – 24.9) post-operatively. Where 100% represents full and limitless functioning, the mean SF36 improved from 42.7% pre-operatively (36.7 – 48.6) to 64.9% (57.7 – 72.0) post-operatively. All the results were significant (p value < 0.05).

Discussion After single and multiple level Bryan cervical disc replacements in the cervical spine, there is significant decrease in perceived disability and pain as well as improvement in functional ability when compared to the pre-operative status of these patients. It is proposed that if undertaking cervical discectomy, maintenance of normal cervical motion where possible correlates with higher patient satisfaction when compared to more conventional cervical discectomy techniques.

Introduction

The viscoelastic cervical disk prosthesis ESP is an innovative one-piece deformable but cohesive interbody spacer. It is an evolution of the LP ESP lumbar disk implanted since 2006. CP ESP provides 6 full degrees of freedom about the 3 axes including shock absorption. The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion (figure 1)

It thus differs substantially from current prostheses. This study reports the results of a prospective series of 49 patients who are representative of the current use of the ESP implant since 2012.

Introduction

The ESP prosthesis is a one-piece deformable but cohesive interbody spacer. it provides 6 full degrees of freedom about the 3 axes including shock absorption (fig1). The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion in this “silentblock” implant. It thus differs substantially from current prostheses.

Introduction

The viscoelastic lumbar disk prosthesis ESP is an innovative one-piece deformable but cohesive interbody spacer; it provides 6 full degrees of freedom about the 3 axes including shock absorption. The prosthesis geometry allows limited rotation and translation with resistance to motion (elastic return property) aimed at avoiding overload of the posterior facets. The rotation center can vary freely during motion. It thus differs substantially from current prostheses. This study reports the results of a prospective series of 120 patients who are representative of the current use of the ESP implant since 2006.

Current total disc prostheses are 2- or 3-pieces devices, including 1 or 2 bearing surfaces, and providing 3 or 5 degrees of freedom but with no, or very little, resistance. The ESP^® is a one-piece deformable implant made of silicon and polycarbonate polyurethane elastomer securely fixed to titanium endplates. It allows limited rotation and translation with elastic return. This cushion without fixed rotation center achieves 6 degrees of freedom including shock absorption. An earlier attempt to use elastomers (Acroflex^®) failed clinically due to the polymer. This highlights the need for accurate in-vitro fatigue testing and clinical evaluations.

In-vitro fatigue testing with more than 40 millions cycles were performed on different samples for compression, flexion-extension bending, lateral bending, torsion and shear. A prospective trial was initiated in 2004 for L3L4, L4L5 and L5S1 levels. Total disc replacements have been performed in 153 lumbar levels through extra-peritoneal mini-invasive anterior approach.

After in-vitro testing, microscopic examination showed that the polymer core remained unchanged without evidence of cracking or other degradation. Gravimetric analysis revealed insignificant changes in weight. The geometrical characteristics and the cohesion of the implants remained stable. After 3 years clinical experience, there was no device related complication, except one early revision for a post-traumatic implant migration. VAS and ODI scores improvements were equivalent to other published series.

In-vitro fatigue testing and short term results of the innovative ESP^® prosthesis demonstrate the reliability of the concept. The results are equivalent to other series with conventional implants.

This prospective multicentre study was undertaken to determine segmental movement, disc height and sagittal alignment after total disc replacement (TDR) in the lumbosacral spine and to assess the correlation of biomechanical properties to clinical outcomes.

A total of 173 patients with degenerative disc disease and low back pain for more than one year were randomised to receive either TDR or multidisciplinary rehabilitation (MDR). Segmental movement in the sagittal plane and disc height were measured using distortion compensated roentgen analysis (DCRA) comparing radiographs in active flexion and extension. Correlation analysis between the range of movement or disc height and patient-reported outcomes was performed in both groups. After two years, no significant change in movement in the sagittal plane was found in segments with TDR or between the two treatment groups. It remained the same or increased slightly in untreated segments in the TDR group and in this group there was a significant increase in disc height in the operated segments. There was no correlation between segmental movement or disc height and patient-reported outcomes in either group.

In this study, insertion of an intervertebral disc prosthesis TDR did not increase movement in the sagittal plane and segmental movement did not correlate with patient-reported outcomes. This suggests that in the lumbar spine the movement preserving properties of TDR are not major determinants of clinical outcomes.

Cite this article: Bone Joint J 2013;95-B:81–9.

Introduction The current study was undertaken to investigate the biomechanical and biologic in-growth characteristics of the Porous Coated Motion™ cervical disc prosthesis following a six and twelve-month implant duration using an in-vivo caprine model. Methods Twelve mature Nubian goats were divided into two groups based on post-operative survival periods of six (n=6) and twelve months (n=6). Using an anterior surgical approach, a complete diskectomy was performed at the C3-C4, followed by implantation of the Porous Coated Motion™ device. Functional outcomes of the disc prosthesis were based on computed tomography (CT), multi-directional flexibility testing, undecalcifed histology, histomorphometry and immunocytochemical analyses. Results There was no evidence of prosthesis loosening, neurologic or vascular complications. CT scans demonstrated the ability to image and assess the cervical spinal canal for the presence of compressive pathology in the area of the CoCrMo prosthesis. Multi-directional flexibility testing indicated no differences in full range of intervertebral motion between the disc prosthesis and non-operative controls (n=7) under axial rotation or lateral bending conditions (p> 0.05). Flexion-extension produced significantly more motion for the intact spine compared to the cervical disc prosthesis (p< 0.05). Based on immunohistochemical and histologic analysis, there was no evidence of particulate debris, cytokines or cellular apoptosis within the local tissues overlying the operative site or systemic tissues. Moreover, review of the spinal cord at the operative levels indicated no evidence of cord lesions, inflammatory reaction, wear particles or significant pathologic changes in any treatment. Histomorphometric analysis at the metal-bone interface indicated the mean trabecular ingrowth of 40.5±24.4% at six-months and 58.65% ± 28.04 at twelve months. Discussion All twelve goats undergoing cervical disc replacement had no evidence of implant loosening or inflammatory reactions from particulate wear debris. Segmental intervertebral motion was preserved based on multi-directional flexibility testing. The TiCaP porous ingrowth surface provided some immediate advantages for endplate osseointegration as there was no evidence of implant subluxation, despite immediate post-operative unrestricted cervical activity. Following cervical disc replacement, histological osseointegration at the implant-bone interface is possible, while preserving segmental motion