Implantation Of Artificial Disc Research Articles

133. Facet joint loading after one- and two-level cervical disc arthroplasty

133. Facet joint loading after one- and two-level cervical disc arthroplasty

A review of discogenic pain management by interventional techniques.

This review article describes the various image guided interventional techniques used for treating chronic backache attributed to disc related pathologies. With the aim of minimum invasion and maximum relief, these procedures comprise predominantly of annuloplasty and disc decompression via different mechanisms. Newer therapies are discussed in this review article with the objective of restoring disc height and its biomechanical function by substitution of biochemical constituents, regeneration of cartilaginous end plate and finally artificial disc implantation.

A Comparative in vivo Study of Semi-constrained and Unconstrained Cervical Artificial Disc Prostheses.

The objective of this study is to directly compare different types of cervical artificial disc implants using an in vivo model capable of simulating the axial load on a neck that is similar to the human neck. Cervical arthroplasty was performed at C3-4 in 14 healthy female adult Alpine goats. The goats were divided into three groups. Group A received Bryan (unconstrained one-piece design); Group B received ProDisc-C (semi-constrained two-piece design); and Group C received Mobi-C (unconstrained three-piece design) artificial discs. The goats were monitored in a veterinary unit for 6 months with radiography at regular intervals. Each goat tolerated cervical arthroplasty well and had satisfactory placement of their implant per intra-operative radiography. Implants monitored in Group A demonstrated no migration. One out of five implants in Group B experienced anterior migration at 3 months. In Group C, anterior migration and disintegration occurred in all four implants, with migration occurring during the first postoperative week in three implants and after 5 weeks in the fourth. Unconstrained multi-piece artificial cervical discs may be prone to anterior migration and extrusion out of the disc space. This outcome deserves attention in individuals with a hypermobile neck and/or an occupation involving the use of a head-supported mass, such as helmets.

Anterior lumbar interbody surgery for spondylosis results from a classically-trained neurosurgeon

Anterior lumbar surgery for degenerative disc disease (DDD) is a relatively novel technique that can prevent damage to posterior osseous, muscular and ligamentous spinal elements. This study reports the outcomes and complications in 286 patients who underwent fusion – with artificial disc implants or combined fusion and artificial disc implants – by a single-operator neurosurgeon, with up to 24months of follow-up. The visual analogue scale (VAS), Oswestry Disability Index (ODI), Short Form 36 (SF36) and prospective log of adverse events were used to assess the clinical outcome. Radiographic assessments of implant position and bony fusion were analysed. Intraoperative and postoperative complications were also recorded. Irrespective of pre-surgical symptoms (back pain alone or back and leg pain combined), workers’ compensation status and type of surgical implant, clinically significant improvements in VAS, ODI and SF36 were primarily observed at 3 and/or 6month follow-up, and improvements were maintained at 24months after surgery. A 94% fusion rate was obtained; the overall complication was 9.8% which included 3.5% with vascular complications. The anterior lumbar approach can be used for treating DDD for both back pain and back and leg pain with low complication rates. With appropriate training, single-operator neurosurgeons can safely perform these surgeries.

Impact of Cervical Artificial Disc Implantation on the Biomechanical Function of Adjacent Segments

The range of movement(ROM) of adjacent segments and the change of intervertebral disc stress after implanting artificial cervical disc are investigated. The contact problem for bio-modeling is introduced. A normal cervical spine finite element model is proposed. The bone graft and fusion between C5 and C6 and C5/6 artificial disc implantation were simulated. The range of movement on adjacent segment and the change of intervertebral disc’s stress in such two cases are analyzed. Computational results show that the model includes the ligaments, joint capsule and other soft tissue structures, which is real, fine and high accuracy. When the adjacent intervertebral ROM was increased after interbody fusion surgery, the stress of corresponding intervertebral disc was increased obviously and the stress of upper segment of nucleus pulposus and annulus fibrosus were also increased about 70% ,besides the next-bit segments was increased about 40%. There were no differences among cervical spine ROM except extension (p> 0.05) after the implantation of artificial disc, and the stress on adjacent segments was increased less than 10%. The implantation of artificial cervical disc can release the stress on adjacent segments in a certain extent, and resume cervical activities at the same time.

Biotechnologies in the Treatment of Degenerative Disc Disease of the Cervical Spine

ABSTRACTDegenerative disc disease of the cervical spine is a common medical condition in the population with underlying aging, genetic, mechanical and environmental factors. It is characterized with structural collapse, osteophyte formation and loss of the loading function of the intervertebral disc. As a consequence a compression of neural structures is observed with axial neck pain, cervical radiculopathy and myelopathy.Currently, the cervical interbody fusion and artificial disc implantation are the available operative treatment options when medications and physiotherapy are ineffective. New strategies focusing on biologic modalities would be appealing. We review the advanced biotechnologies in the treatment of degenerative disc disease of the spine.Many studies are focused on therapeutic molecules capable to influence the biochemical and structural processes of intervertebral disc degeneration. These factors are categorized as anticatabolics, mitogens, chondrogenic morphogens and intracellular regulators. Another step that further opposes the simple injection of tissues with therapeutic molecules is gene therapy seeking to transfer genetic material into target cells, which in turn become in situ factories for the long-term production of desired proteins. The use of tissue-engineered intervertebral disc constructs may prove helpful when treating degenerative cervical disc disease. An in vitro technology designed to produce cartilage or bone with desired biomechanical properties to repair damaged tissues is available nowadays. In the near future the golden standard might be the replacement of the degenerated disc with biological rather than polymer or metal prostheses.However, the cost-effectiveness of the reviewed approaches has not been definitively established. Regardless of its efficacy, the safety and economic issues may ultimately determine whether these therapies are viewed as an acceptable alternative to the recent treatment options.

Models that incorporate spinal structures predict better wear performance of cervical artificial discs

Wear simulators and their corresponding wear predictive models provide limited information on wear characteristics of artificial discs. Analyses in previous studies that controlled loading profiles according to International Standards Organization (ISO)/American Society for Testing and Materials standards did not account for factors such as the influence of anatomic structures. Retrieval analyses reveal failure modes that are not observed in benchtop simulations and thus indicate deficiencies associated with existing approaches. To understand the impact of the adjoining spinal structures of a ligamentous segment on the wear of an artificial cervical disc. Prediction of wear in artificial disc implants (total disc replacement [TDR]) in situ using finite element modeling. A novel predictive finite element model was used to evaluate wear in a simulated functional spinal unit (FSU). A predictive finite element wear model of the disc alone (TDR Only) was developed, along the lines of that proposed in the literature. This model was then incorporated into a ligamentous C5-C6 finite element model (TDR+FSU). Both of these models were subjected to a motion profile (rotation about three axes) with varying preloads of 50 to150 N at 1 Hz, consistent with ISO 18192. A subroutine based on Archard law simulated abrasive wear on the polymeric core up to 10 million cycles. The TDR+FSU model was further modified to simulate facetectomy, sequential addition of ligaments, and compressive load; simulations were repeated for 10 million cycles. The predicted wear patterns in the isolated disc (TDR Only) and in TDR+FSU were completely inconsistent. The TDR+FSU model predicted localized wear in certain regions, in contrast to the uniformly distributed wear pattern of the TDR-only model. In addition, the cumulative volumetric wear for the TDR-only model was 10 times that of the TDR+FSU model. The TDR+FSU model also revealed a separation at the articulating interface during extension and lateral bending. After facetectomy, the wear pattern remained lopsided, but linear wear increased eightfold, whereas volumetric wear almost tripled. This was accompanied by a reduction in observed liftoff. The addition of anterior longitudinal ligament/posterior longitudinal ligament did not affect volumetric or linear wear. On the removal of all ligaments and facet forces, and replacement of follower load with a compressive load, the wear pattern returned to an approximation of the TDR-only test case, whereas the cumulative volumetric wear became nearly equivalent. In this case, the liftoff phenomenon was absent. Anatomic structures and follower load mitigate the wear of an artificial disc. The proposed model (TDR+FSU) would enable further study of the effects of clinical parameters (eg, surgical variables, different loading profiles, different disc designs, and bone quality) on wear in these implants.

Intervertebral Disc: Anatomy‐Physiology‐Pathophysiology‐Treatment

This review article describes anatomy, physiology, pathophysiology and treatment of intervertebral disc. The intervertebral discs lie between the vertebral bodies, linking them together. The components of the disc are nucleus pulposus, annulus fibrosus and cartilagenous end-plates. The blood supply to the disc is only to the cartilagenous end-plates. The nerve supply is basically through the sinovertebral nerve. Biochemically, the important constituents of the disc are collagen fibers, elastin fibers and aggrecan. As the disc ages, degeneration occurs, osmotic pressure is lost in the nucleus, dehydration occurs, and the disc loses its height. During these changes, nociceptive nuclear material tracks and leaks through the outer rim of the annulus. This is the main source of discogenic pain. While this is occurring, the degenerative disc, having lost its height, effects the structures close by, such as ligamentum flavum, facet joints, and the shape of the neural foramina. This is the main cause of spinal stenosis and radicular pain due to the disc degeneration in the aged populations. Diagnosis is done by a strict protocol and treatment options are described in this review. The rationale for new therapies are to substitute the biochemical constituents, or augment nucleus pulposus or regenerate cartilaginous end-plate or finally artificial disc implantation..

Cervical arthroplasty in the management of spondylotic myelopathy: 18-month results

Cervical spinal cord compression managed via an anterior approach with an arthrodesis may be associated with a decreased range of motion and accelerated adjacent-segment degeneration. Artificial cervical disc replacement may address these problems. The author presents a series of 11 patients (seven men and four women, ages 31-55 years) with anterior cervical decompression and placement of a total of 15 artificial disc prostheses. Clinical and radiological follow-up review was performed at 24 hours, 6 weeks, 3 months, 6 months, and then yearly (mean follow-up period 18.4 months, range 10-32 months). There were no major complications. There was an improvement in the Nurick grade by 0.91 grades (p < 0.001) and in the Oswestry Neck Disability Index by 41.5 percentage points (p < 0.001). In one case fusion was attained at 17 months postoperatively and one patient had a transient worsening of preoperative symptoms postoperatively, with focal kyphosis. The spinal cord was decompressed on postoperative imaging in all cases. Cervical arthroplasty after anterior cervical decompression at one or more levels represents an exciting tool in the management of spinal cord compression caused by spondylotic disease or acute disc prolapse. Results obtained in this study add further weight to the potential role of cervical arthroplasty for cervical myelopathy and longer follow up is provided on a previously reported series. It is suggested that care must be taken in using this unconstrained prosthesis if there is a preexisting spinal deformity. Longer follow up will reveal any delayed problems with artificial disc implantation, but in the short to medium term, this technique offers an excellent outcome.

Cervical Arthroplasty in the Management of Spondylotic Myelopathy

Cervical spinal cord compression managed via an anterior approach with an arthrodesis is associated with a decreased range of motion and accelerated adjacent segment degeneration. Artificial cervical disc replacement may address these problems. A series of seven cases (three women, two men; age 31–55 years) of anterior cervical decompression and placement of an artificial disc prosthesis is presented. A total of nine Bryan cervical disc prostheses (Spinal Dynamics Corp., Mercer Island, WA) were placed. Clinical and radiologic follow-up was performed at 24 hours, 6 weeks, 3 months, 6 months, and then yearly (mean follow-up period 6.29 months, range 1–17 months). There were no complications. There was an improvement in Nurick grade by 0.72 grade (P < 0.05) and Oswestry Neck Disability Index score by 51.4 points (P < 0.0001). Motion was preserved. Improvement in lordosis occurred in 29% of cases. The spinal cord was decompressed on postoperative imaging. Cervical arthroplasty after anterior cervical decompression at one or more levels represents an exciting tool in the management of spinal cord compression secondary to spondylotic disease or acute disc prolapse. This is the first study that looks specifically at cervical arthroplasty for cervical myelopathy. Longer follow-up will reveal any delayed problems with artificial disc implantation, but in the short term, this technique offers an excellent outcome.