Motion-preserving Technologies Research Articles

Adjacent Segment Disease

Spinal fusion is gold-standard treatment for degenerative disc disease (DDD) both at cervical and lumbar spine, and it is time tested. Perhaps it has its bundle of complications. Elimination of motion results in accentuated degeneration of adjacent segments leading to adjacent segment degeneration radiographically and, if symptomatic, leads to adjacent segment disease. There is still a debate on whether there is such an entity or whether it is a manifestation of natural history or an iatrogenic phenomenon. Motion preservation surgeries were developed to address the same issue, which includes total disc replacement, nucleus replacement, interspinous implants, and dynamic posterior stabilization systems. The primary goal of motion preservation surgery is to maintain normal or near-normal motion in an attempt to prevent adverse outcomes, which are commonly seen with conventional spinal fusion, most notably the development of adjacent-level DDD. A search was conducted in PubMed using the terms (“adjacent segment”) AND (“disease” OR “degeneration” or “pathology”). Then the articles were shortlisted based on time of publication (2005 onward), publication in English and inclusion of human subjects. This resulted in 253 articles. Another search for ((“Motion preservation”) AND (“Spine”)) OR (“Adjacent segment disease”) OR (“Adjacent segment pathology”) OR (“Adjacent segment degeneration”) yielded 76 articles. This narrative review discusses various issues pertaining to the current evidence regarding adjacent segment disease (ASD), including the controversy on whether ASD is actually an entity, its etiopathogenesis, clinical features, as well as the role of motion preservation technologies to reduce its incidence. There is still enthusiasm and concerns regarding the benefits of motion preservation surgery since it is still an area of ongoing research.

Current concepts of spondylosis and posterior spinal motion preservation for radiologists.

Spinal fusion is performed to eliminate motion at a degenerated or unstable segment. However, this is associated with loss of motion at the fused levels and increased stress on adjacent levels. Motion-preserving implants have been designed in effort to mitigate the limitations of fusion. This review will focus on posterior spinal motion-preserving technologies. In the cervical spine, laminoplasty is a posterior motion-preserving procedure used in the management of myelopathy/cord compression. In the lumbar spine, motion-sparing systems include interspinous process devices (also referred to as interspinous process spacers or distraction devices), posterior dynamic stabilization devices (also referred to as pedicle screw/rod fixation-based systems), and posterior element replacement systems (also referred to as total facet replacement devices). Knowledge of the intended physiologic purpose, hardware utilized, and complications is important in the assessment of imaging in those who have undergone posterior motion preservation procedures.

Cervical Arthroplasty: Long-Term Outcomes of FDA IDE Trials.

Study Design:Special Issues MIS/Navigation.Objectives:Over the past decade, cervical total disc replacement has been established in numerous randomized clinical trials as an alternative to anterior cervical discectomy and fusion. The purpose of this review is to evaluate the long-term outcomes after cervical arthroplasty.Methods/Results:Early outcomes (studies with 2-year follow-up) after arthroplasty established the efficacy of total disc replacement and, more recently, long-term studies have shown the durability of these good clinical outcomes. Biomechanical and clinical data have demonstrated that this motion preservation technology decreases adjacent-level stresses compared with fusion. Additionally, long-term outcomes as well as outcomes after multilevel arthroplasty have now established the role of arthroplasty in select patient populations, namely patients with 1- and 2-level spondylosis/stenosis causing radiculopathy from C3-7.Conclusions:Data on adjacent segment deterioration and adjacent segment reoperation remains controversial but suggest a positive effect after arthroplasty. But these are multifactorial issues and we still do not fully understand all the factors affecting adjacent segment pathology and longer-term studies after arthroplasty will continue to address this issue.

Value of Cervical Disk Arthroplasty.

Over the last decade, several of the Food and Drug Administration-regulated investigational device exemption (IDE) trials have compared multiple cervical disk arthroplasty (CDA) devices to anterior cervical decompression and fusion (ACDF) showing comparable and even superior patient-reported outcomes. CDA has been an increasingly attractive option because of the positive outcomes and the motion-preserving technology. However, with the large burden that health care expenditures place on the economy, the focus is now on the value of treatment options. Cost-effectiveness studies assess value by evaluating both outcomes and cost, and recently several have been conducted comparing CDA and ACDF. The results have consistently shown that CDA is a cost-effective alternative, however, in comparison to ACDF the results remain inconclusive. The lack of incorporation of disease specific measures into health state utility values, the inconsistent methods of calculating cost, and the fact that a vast majority of the results have come from industry-sponsored studies makes it difficult to form a definitive conclusion. Despite these limitations, both procedures have proven to be safe, effective, and cost-efficient alternatives.

Adjacent Segment Pathology after Anterior Cervical Fusion

Anterior cervical fusion has become a standard of care for numerous pathologic conditions of the cervical spine. However, subsequent development of clinically significant disc disease at levels adjacent to fused discs is a serious long-term complication of this procedure. As more patients live longer after surgery, it is foreseeable that adjacent segment pathology (ASP) will develop in increasing numbers of patients. Also, ASP has been studied more intensively with the recent popularity of motion preservation technologies like total disc arthroplasty. The true nature and scope of ASP remains poorly understood. The etiology of ASP is most likely multifactorial. Various factors including altered biomechanical stresses, surgical disruption of soft tissue and the natural history of cervical disc disease contribute to the development of ASP. General factors associated with disc degeneration including gender, age, smoking and sports may play a role in the development of ASP. Postoperative sagittal alignment and type of surgery are also considered potential causes of ASP. Therefore, a spine surgeon must be particularly careful to avoid unnecessary disruption of the musculoligamentous structures, reduced risk of direct injury to the disc during dissection and maintain a safe margin between the plate edge and adjacent vertebrae during anterior cervical fusion.

Fluoroscopic assessment of lumbar total disc replacement kinematics during walking.

Descriptive. The purpose of this study was to determine the in vivo kinematics of functional spinal units, during gait, in individuals with a single-level lumbar total disc replacement (TDR). TDR is a motion preservation technology that offers an alternative to spinal fusion for treatment of degenerative disc disease. The aim of TDRs is to replicate motion of the functional spinal units, which may protect adjacent intervertebral discs against accelerated degeneration. At present, there is limited understanding of the in vivo motion of TDRs, particularly during dynamic activities such as gait. Such information is important for understanding the wear characteristics of TDRs and furthering design rationale of future implants. TDR motions were obtained from 24 participants who underwent implantation with single-level L4-L5 or L5-S1 CHARITÉ or In Motion TDRs. Video fluoroscopy was used to obtain measurements in the frontal and sagittal planes during fixed speed treadmill walking. The mean range of motion between the upper and lower lumbar TDR endplates during walking was 1.6° and 2.4° in the frontal and sagittal planes, respectively. These values were significantly different from zero and corresponded to 19% of the maximum static range of motion in each plane. Lumbar TDRs provide a degree of motion preservation at the operative level during moderate speed walking. The distribution of lumbar TDR motions during walking presented here will inform relevant standards for conducting standardized tests of lumbar TDRs, particularly wear assessments, and, hence, enable more realistic mechanical and computer-based wear simulations to be performed. N/A.

Incidence of adjacent segment degeneration in cervical disc arthroplasty versus anterior cervical decompression and fusion meta-analysis of prospective studies.

PurposeTo evaluate the incidence of adjacent segment disease (ASD) requiring surgical intervention between anterior cervical decompression and fusion (ACDF) and total disc replacement (TDR).BackgroundThe concern for ASD has led to the development of motion-preserving technologies such as TDR. However, whether replacement arthroplasty in the spine achieves its primary patient-centered objective of lowering the frequency of adjacent segment degeneration is not verified yet.MethodsA comprehensive literature search was performed using PubMed, Cochrane Central Register of Controlled Trials and Embase. These databases were thoroughly searched for prospective randomized studies comparing ACDF and TDR. Eight studies met the inclusion criteria for a meta-analysis and were used to report an overall rate of ASD for both ACDF and TDR.ResultsPooling data from 8 prospective studies, the overall sample size at baseline was 1,726 patients (889 in the TDR group and 837 in the ACDF group). The ACDF group had significantly more ASDs compared with the TDR group at 24 months postoperatively [odds ratios (OR), 1.31; 95 % confidence interval (CI), 1.04–1.64; p = 0.02]. The TDR group had significantly fewer adjacent segment reoperations compared with the ACDF group at 24 months postoperatively (OR, 0.49; 95 % CI, 0.25–0.96; p = 0.04).ConclusionsFor patients with one-level cervical degenerative disc disease (CDDD), total disc replacement was found to have significantly fewer ASDs and reoperations compared with the ACDF. Cervical replacement arthroplasty may be superior to ACDF in ASD. Therefore, cervical arthroplasty is a safe and effective surgical procedure for treating CDDD. We suggest adopting TDR on a large scale.

Quantitative analysis of the nonlinear displacement-load behavior of the lumbar spine.

There is currently no universal model or fitting method to characterize the visco-elastic behavior of the lumbar spine observed in displacement versus load hysteresis loops. In this study, proposed methods for fitting these loops, along with the metrics obtained, were thoroughly analyzed. A spline fitting technique was shown to provide a consistent approximation of spinal kinetic behavior that can be differentiated and integrated. Using this tool, previously established metrics were analyzed using data from two separate studies evaluating different motion preservation technologies. Many of the metrics, however, provided no significant differences beyond range of motion analysis. Particular attention was paid to how different definitions of the neutral zone capture the high-flexibility region often seen in lumbar hysteresis loops. As a result, the maximum slope was introduced and shown to be well defined. This new parameter offers promise as a descriptive measurement of spinal instability in vitro and may have future implications in clinical diagnosis and treatment of spinal instability. In particular, it could help in assigning treatments to specific stabilizing effects in the lumbar spine.

Rate of Adjacent Segment Disease in Cervical Disc Arthroplasty Versus Single-Level Fusion

Meta-analysis of randomized controlled trials. To compare the reported incidence of adjacent segment disease (ASD) requiring surgical intervention between anterior cervical decompression and fusion (ACDF) and total disc arthroplasty (TDA). The concern for ASD has led to the development of motion-preserving technologies such as TDA. To date, however, no known study has sought to compare the incidence of ASD between ACDF and TDA in major prospective studies. A systematic review of IDE and non-IDE trials was performed using PubMed and Cochrane libraries. These databases were thoroughly searched for prospective randomized studies comparing ACDF and TDR. Six studies met the inclusion criteria for a meta-analysis and were used to report an overall rate of ASD for both ACDF and TDA. Pooling data from 6 prospective studies, the overall sample size at baseline was 1586 (ACDF = 777, TDA = 809) and at the final follow-up was 1110 giving an overall follow-up of 70%. Patients after an ACDF had a lower rate of follow-up overall than those after TDR (ACDF: 67.3% vs. TDR: 72.6%, P= 0.01). Thirty-six patients required adjacent-level surgery after an ACDF at 2 to 5 years of follow-up (6.9%) compared with 30 patients after a TDA (5.1%). The corresponding reoperation rate for ASD was 2.4 ± 1.7% per year for ACDF versus 1.1 ± 1.5% per year for TDR. These differences were not statistically significant (P= 0.44). Using a Kaplan-Meier analysis and historical data, we expect 48 patients in the ACDF group and 55 patients in the TDR group to have symptomatic disease at an adjacent level. From a meta-analysis of prospective studies, there is no difference in the rate of ASD for ACDF versus TDA. We also report an overall lower rate of follow-up for patients with ACDF than for those with TDR. Future prospective studies should continue to focus on excellent patient follow-up and accurate assessment of patient symptoms that are attributable to an adjacent level as this has been an under-reported finding in prospective studies. 1.

How often is adjacent segment disease reported? A systematic review of prospective studies comparing total disc arthoplasty versus ACDF

After a systematic review, six prospective studies comparing TDR versus ACDF were selected. These studies had between 2–5 years follow-up and reported revisions due to adjacent segment disease. The concern for adjacent segment disease (ASD) has led to the development of motion-preserving technologies such as total disc arthoplasty (TDA). However, numerous studies comparing ACDF versus TDA do not report the number of patients who develop symptoms attributable to an adjacent level or the number of revisions that occur at an adjacent level. Often the follow-up period is limited as well. A systematic review of IDE and non-IDE trials was performed using PubMed and Cochrane Libraries. These databases were thoroughly searched for prospective randomized studies comparing ACDF and TDR. Specifically, studies reporting clinical outcomes and symptomatic ASD with at least 2 years of follow-up were selected. Six studies met the inclusion criteria and are discussed in the review. Pooling data from six prospective studies, the overall sample size at baseline was 1586 (ACDF = 777, TDA = 809) and at final follow-up was 1110, giving an overall follow-up of 70%. Of 1586 surgically treated patients, 51 (3.2%, ACDF = 30, TDA = 21) required revision surgery at an adjacent level at 2–5 years of follow-up. There was no data available on the incidence of ASD or the number of patients with ASD treated non-operatively. There has not been a study to date that has demonstrated a difference in the rate of ASD for ACDF versus TDR. There is a paucity of data from prospective studies regarding the incidence of ASD and the proportion of patients who go on to require further surgical intervention. Prospective studies should continue to focus on excellent patient follow-up and accurate assessment of patient symptoms as ASD has been under reported in prospective studies.

Access related complications during anterior exposure of the lumbar spine

The new millennium has witnessed the emergence of minimally invasive, non-posterior based surgery of the lumbar spine, in particular via lateral based methodologies to discectomy and fusion. In contrast, and perhaps for a variety of reasons, anterior motion preservation (non-fusion) technologies are playing a comparatively lesser, though incompletely defined, role at present. Lateral based motion preservation technologies await definition of their eventual role in the armamentarium of minimally invasive surgical therapies of the lumbar spine. While injury to the major vascular structures remains the most serious and feared complication of the anterior approach, this occurrence has been nearly eliminated by the use of lateral based approaches for discectomy and fusion cephalad to L5-S1. Whether anterior or lateral based, non-posterior approaches to the lumbar spine share certain access related pitfalls and complications, including damage to the urologic and neurologic structures, as well as gastrointestinal and abdominal wall issues. This review will focus on the recognition, management and prevention of these anterior and lateral access related complications.

Biomechanics of Disc Degeneration

Disc degeneration and associated disorders are among the most debated topics in the orthopedic literature over the past few decades. These may be attributed to interrelated mechanical, biochemical, and environmental factors. The treatment options vary from conservative approaches to surgery, depending on the severity of degeneration and response to conservative therapies. Spinal fusion is considered to be the “gold standard” in surgical methods till date. However, the association of adjacent level degeneration has led to the evolution of motion preservation technologies like spinal arthroplasty and posterior dynamic stabilization systems. These new technologies are aimed to address pain and preserve motion while maintaining a proper load sharing among various spinal elements. This paper provides an elaborative biomechanical review of the technologies aimed to address the disc degeneration and reiterates the point that biomechanical efficacy followed by long-term clinical success will allow these nonfusion technologies as alternatives to fusion, at least in certain patient population.

Reoperations and Complications of Failed Lumbar Total Disk Replacement

Advancements in lumbar total disk replacement (TDR) and motion preserving technology have become more prevalent. With the clinical application of these devices, complications and failures will need to be addressed. These complications have been correlated with patient and surgeon related factors. Successful management is dependant on identifying the mode of failure and surgeon awareness of approach related complications. Adhering to patient selection criteria and avoiding technical errors can minimize device failure. When revision surgery is indicated, careful preoperative planning is mandated in order to identify the underlying pathology and obtain successful revision goals.

Motion-preserving technologies for degenerative lumbar spine: The past, present, and future horizons

Over the past few decades, remarkable advancements in the understanding of the origin of low-back pain and lumbar spinal disorders have been achieved. Spinal fusion is generally considered the “gold standard” in the treatment of low-back pain; however, fusion is also associated with accelerated degeneration of adjacent levels. Spinal arthroplasty and dynamic stabilization technologies, as well as the continuous improvement in diagnosis and surgical interventions, have opened a new era of treatment options. Recent advancements in nonfusion technologies such as motion-preservation devices and posterior dynamic stabilization may change the gold standard. These devices are designed with the intent to provide stabilization and eliminate pain while preserving motion of the functional spinal unit. The adaption of nonfusion technologies by the surgical community and payers for the treatment of degenerative spinal conditions will depend on the long-term clinical outcome of controlled randomized clinical studies. Although the development of nonfusion technology has just started and the adoption is very slow, it may be considered a viable option for motion preservation in coming years. This review article provides technical and surgical views from the past and from the present, as well as a glance at the future endeavors and challenges in instrumentation development for lumbar spinal disorders.

L5–S1 disc replacement after two previous fusion surgeries for scoliosis

Following scoliosis surgery, lumbar motion segment degeneration below the level of fusion is not uncommon. Especially long fusions extending to the mid and lower lumbar spine increase the likelihood of degeneration of the remaining motion segments. The management for these patients is controversial and depends on the clinical presentation and level of degeneration. The increasing confidence in motion-preserving technology leads to a dilemma on whether to fuse the remaining lumbar levels or risk utilising disc arthroplasty to preserve the remaining motion segments and facilitate coronal balance in patients with previous long fusion for scoliosis. We present an interesting case of a 44-year-old lady, who underwent two-stage corrective surgery for progressive idiopathic scoliosis at the age of 22years. In the first stage, she had T11-L3 anterior fusion, whilst in the second stage posterior fusion was done from T5 to L3. At 22years after the initial surgery, she presented with worsening low back pain and bilateral L4 radicular symptoms. MRI scan confirmed severe disc degeneration at L3-4 and L5-S1 levels with preserved L4-5 disc. She initially underwent L3-L4 decompression and posterolateral fusion at that level, which relieved her radicular symptoms. However, she had persistent pain at the lumbosacral junction with Modic I changes. The options of an anterior L5-S1 fusion or disc replacement were considered and discussed with the patient. The disc replacement option was decided upon with the patient, as anterior fusion was judged to increase the risk of coronal imbalance. At the 1-year follow-up, she reported significant improvement in the back pain. The radiographs at 1year showed satisfactory position and function of the artificial disc replacement. The disc was flexed laterally, accommodating the coronal balance of the spine. We conclude that L5-S1 motion segment can be preserved with artificial disc replacement in patients with previous long fusion for scoliosis surgery. The real difficulty arises when choosing between disc replacement and extension of fusion. In our patient, the disc replacement has worked well so far. However, the disc is clearly at a mechanical disadvantage, and loss of function in the mid- or long term would not be surprising.

Motion-preserving Surgery Can Prevent Early Breakdown of Adjacent Segments

A retrospective study. This study aims to determine the prevalence and nature of adjacent-segment deterioration after posterior ligamentoplasty, posterolateral lumbar fusion (PLF) versus posterior lumbar interbody fusion (PLIF). Motion-preserving technologies including disc arthroplasty and ligamentoplasty were gaining interest to reduce the risk of adjacent-segment morbidity. However, few clinical studies have reported the prevalence of adjacent-segment disease in motion-preserving surgeries. Two-hundred and eighteen consecutive patients who had undergone single-level posterior L4-L5 pedicle-screw-instrumented fusion or ligamentoplasty were reviewed at minimum 2-year follow-up. They were 91 males and 127 females with mean age of 62 years. Follow-up period was averaged 41 months and follow-up rate was 97.3%. There were 78 cases of PLIF, 75 of PLF, and 65 of ligamentoplasty. Demographics were not statistically different among the 3 groups. Prevalence of adjacent-segment morbidity (radiculopathy associated with newly developed pathologies at neighboring levels) and required additional surgery were investigated. Prevalence of adjacent-segment morbidity was 14.1% in PLIF, 13.3% in PLF, and 9.2% in ligamentoplasty; the time to represent symptom was averaged 25.2, 39.3, and 51.8 postoperative months, respectively. Additional surgeries for adjacent-segment pathologies were required for 7.6% in PLIF, 6.7% in PLF, and 1.5% in ligamentoplasty. Although all PLF cases needed only decompression surgeries, 66.7% of reoperations in the PLIF group required fusion owing to progression of adjacent-segment instability. Prevalence of adjacent-segment disease and reoperation rate seemed to be lower in ligamentoplasty than fusion surgeries, but the difference was not significant. Ligamentoplasty circumvented adjacent-segment disease for longer period than fusion surgeries. Although the rates of additional surgeries in PLIF and PLF were comparable, PLIF developed adjacent-level instability and required fusion surgery more frequently than PLF.

Delayed Hyper-Reactivity to Metal Ions After Cervical Disc Arthroplasty

Anecdotal case report. To report a very interesting and perplexing complication of cervical total disc arthroplasty that has not been previously reported in literature. Although there has been increasing interest in the field of artificial disc replacement to treat cervical degenerative disc disease, not much has been mentioned in the literature about the potential complications of the disc itself. We encountered a delayed complication in 1 patient that has not been reported in the literature. Thirty-nine-year-old white woman received total disc arthroplasty for herniated intervertebral disc at C5-C6 level uneventfully. She had recurrence of symptoms 9 months after the procedure and failed to respond to conservative measurements. Imaging revealed soft tissue mass posterior to the implanted disc encroaching the spinal cord. Surgical explantation and exploration of the disc space revealed thick layer of abnormal hyaline cartilaginous tissue with chronic inflammatory debris. The patient had complete resolution of symptoms after the revision surgery. Although there is increased enthusiasm about motion preservation technology and disc replacement surgery for intervertebral disc herniation, unexpected complications like the present case need to be shared within the scientific community to better understand the risks associated with these new and promising devices.

P134. Quantification of Facet Joint Integrity using T1rho MRI

BACKGROUND CONTEXT: Advancements in diagnostic methods and biomarkers of facet arthrosis are needed as emerging motion-preserving technologies to treat spinal deformities and degenerative spinal conditions continue to develop. Currently there exists no imaging tool that facilitates a quantitative measure of facet articular cartilage integrity. We have recently validated T1rho MRI as a noninvasive, quantitative, highly reproducible biomarker of nucleus pulposus proteoglycan loss and early degenerative disc disease (DDD).

Anatomic Facet Replacement System (AFRS) Restoration of Lumbar Segment Mechanics to Intact: A Finite Element Study and In Vitro Cadaver Investigation

Background Many decompression procedures involve complete or partial facetectomy. Spinal fusion usually stabilizes the motion segment after complete facetectomies. However, problems with fusion, such as adjacent-level degeneration, have increased interest in motionpreservation technologies. Facet arthroplasty may become an important posterior motion-preservation device, but its biomechanical literature is sparse. Methods We conducted an in vitro investigation and finite element study to compare the biomechanical effects of an artificial facet system to the intact spine. In the in vitro study, we tested human osteo-ligamentous segments (L3-S1) in intact, injured, and artificial facet–repaired conditions. For the finite element study, we used a 3-dimensional ligamentous L3-S1 segment model. We simulated destabilization in the intact model by removing the facets across the L4-L5 functional unit, then repaired it with appropriately sized facet implants and compared the ranges of motion, facet loads, disc pressures, and device loads. We also analyzed a finite element model with a rigid posterior pedicle-rod fixation system. We subjected the cadaveric specimens and the models to 400 N of follower load plus a 10 Nm moment in extension, flexion, bending, and rotation. We used a novel technique to apply the follower load in the finite element models such that preload induced minimal vertebral rotation during the range of motion. Results The predicted ranges of motion for the intact and implanted models were consistent with cadaver data. After destabilization and facet replacement, the artificial facet system restored motion in all loading modes to intact values. The implant facet loads were similar to intact facet loads in extension and axial rotation, but less in lateral bending. The intradiscal pressure at the implanted level for the facet replacement device was similar to the intact pressure, whereas with the rigid system the intradiscal pressure was up to 70% less than the intact pressure. The maximum von-Mises stress predicted in the facet replacement construct was 85 MPa in extension at the bone–pedicle screw interface, compared with 174 MPa in the rigid system. Contact stresses at implant mating surfaces were minimal. Conclusions The artificial facet system replicated natural facet kinematics. The cadaveric ranges of motion and the predicted finite element–based data indicated that the implant can “restore” the normal function of the segment after artificial facet replacement. Clinical Relevance Compared to rigid posterior pedicle-rod fixation, the artificial facet system restored the intact mechanics at the implanted level and may prevent adjacent-level degeneration.

Adjacent Level Intradiscal Pressure and Segmental Kinematics Following A Cervical Total Disc Arthroplasty

In vitro investigation of cervical adjacent level intradiscal pressures (IDPs) following a total disc replacement arthroplasty. The current in vitro study was undertaken to compare adjacent level IDPs and operative level kinematics following a cervical arthroplasty versus an arthrodesis procedure. Clinical data indicate the incidence of symptomatic transition syndrome to be as high as 3% annually following a cervical interbody arthrodesis. Recent developments in the motion preservation technology should, in theory, minimize transition syndrome at the adjacent levels. A total of 10 human cadaveric cervical spines were used in this investigation. Following intact analysis, all specimens were sequentially reconstructed at C5-C6 with 1) total disc replacement (TDR), 2) allograft dowel, and 3) allograft dowel + anterior cervical plate. Testing was performed in displacement control under axial rotation, flexion/extension, and lateral bending loading modes. IDPs were recorded at C4-C5 and C6-C7 whereas peak range of motion (ROM) and NZ were monitored at C5-C6 level. Similar IDPs were recorded between the intact condition and a TDR reconstruction at both adjacent levels under all loading modes (P > 0.05). However, the C4-C5 IDP values produced under flexion/extension testing for both arthrodesis treatments were significantly higher than the means obtained for the intact and disc replacement groups (P < 0.05). Similar intergroup differences were observed at the C6-C7 level; however, statistical significance was achieved during all three loading methods (P < 0.05). C5-C6 ROM analysis indicated a significantly lower ROM for both arthrodesis constructs compared with intact and TDR groups during flexion/extension testing (P < 0.05). No differences were recorded between the intact and the total disc replacement group under any loading conditions (P > 0.05). This is a first study to document that a cervical disc replacement arthroplasty procedure maintains adjacent level IDPs and reconstruction level kinematics near the preoperative values. Consequently, total disc replacement may provide an alternative to conventional surgical management of cervical discogenic pathology decreasing the incidence of symptomatic transition syndrome.