Artificial total lumbar disc replacement in Research and Application
Degenerative disc disease (degenerative disc disease, DDD) is a common disease, spinal surgery, pain and disability is an adult one of the main 〔1〕. Conventional wisdom is
that the clinical effect of lumbar fusion is successful, it is not a perfect operation, there is no movement to retain the physiological function of the spine. Lumbar motion segment has been confirmed that the integration of accelerated adjacent segment disc
and facet joint degeneration 〔2〕. Functional anatomy and biomechanics of lumbar
area of in-depth study of different structures and materials made of modern artificial disc device development possible. Artificial disc replacement surgery (artificial disc
replacement, ADR) as an addition to the treatment of lumbar fusion DDD Another reasonable choice is intended to enable pain caused by degenerative disc to be a long-
term mitigation, reconstruction of intervertebral height to protect the nerve tissue, retention spinal movement in order to avoid the late facet joints and adjacent segment of the lesion. With the continuous deepening of artificial disc study in the United States and Europe have confirmed the short-term clinical application can be restored within a
kinematics and load characteristics of the spine and restore spinal stability and functional units of athletic ability〕 〔3 ~ 6. The purpose of this review is to explain the artificial disc prosthesis design principles, introduced in Europe and the United States
research in this field and clinical application.
An anatomical and biomechanical principles of lumbar
For the normal and degenerative lumbar anatomy, biomechanics and kinematics of a comprehensive and accurate understanding of the success of the design of a disc
prosthesis has an important significance. Lumbar spine as a mechanical structure of the complex, providing a normal torso movement, while ensuring the support function of the trunk and protect the nerve tissue from damage. Lumbar structure is a
combination of stability and athletic body, translation and rotation took place in three-
dimensional space. Lumbar intervertebral disc is the movement's main constraints and buffering device, allowing a certain scope and extent of movement 〔7〕, is the most
important restrictions on the movement device, but also is the most important functional units of the spine stabilization device 10〕 〔8. Anterior column of the trunk
in an upright assumed most of the weight of commitment to the posterior column of the
body 16% of the axial load. Hydrophilic nucleus pulposus on the annulus fibrosus tension generated in the resistance to stress and load can be allowed to produce a
certain mobile 〔11〕. 30-year-old after the nucleus pulposus begin to lose moisture,
the volume is also slowly shrinking, loss of stress load conduction and dispersion, fibrous ring bear the load grows, thus gradually become weak and rupture 〔12〕.
Intervertebral disc degeneration can cause intervertebral height changes, the irregular
end-plate and intervertebral disc calcification, eventually leading to reduction in spine activity 〔13〕.
Based on anatomy and biomechanics of lumbar-based research, the success of ADR
prosthesis design goals include ease pain in patients with effective control over the
reconstruction intervertebral height in order to protect nerve tissue and restore spinal movement in order to avoid adjacent segment of the lesion. Prosthesis should be the greatest near-normal physiological disc function of the size and movement in order to
avoid reduce or increase the load on the joint surface.
2 lumbar intervertebral disc prosthesis design
Biomechanics of spine movement required to design a mechanism to rebuild and retain the normal physiological movement in the spine prosthesis. The design difficulty is how to design a good rotation of each lumbar motion segment the center of the center as the flexion and extension, lateral bending and rotation change, and lumbar lateral
flexion accompanied by axial rotation, while 〔5〕. Gunzberg such as an overview of
the principle of intervertebral disc prosthesis design 〔14〕, the level of each segment
there are 3 joints; intervertebral disc to provide an activity and stability of the complex
combination of mechanism; a motion segment center of rotation as the section of segment changes in position or posture change. The first prosthesis by Fernstrom in the last century, described in the late 50s 〔11〕, then used a stainless steel ball prosthesis.
From ADR technology continues to improve the type of prosthesis has also been great development. To date, has designed more than 100 of the artificial disc prosthesis, only a small part of the get tests in animal models, which use less to achieve the level of
clinical 〔12〕. Impede the success of the real design of a prosthesis due to the lack of a credible animal model of high human nature to walk upright so that the force of human lumbar mechanism is different from the animals. At present the main principles of
prosthesis design an analog disc physical movement, these prostheses are generally of metal and polyethylene material composition.
SB Charité is by far the most in-depth study of the artificial disc prosthesis, there
are more than 10 years of satisfactory results of clinical application of 〔17〕. This
device consists of two cobalt-chromium alloy endplates and between the ultra-high
molecular weight polyethylene sliding between the nucleus formed. Each end plate includes three for the dentate Riveting processes and a pure titanium and
hydroxyapatite materials, outer membrane, to strengthen it and the biological fixation between the vertebrae. SB Charité ? prosthesis in vitro biomechanical testing results
for the polyethylene material that can withstand a million times of fatigue tests 〔16〕.
Cadaver spine biomechanics research suggests that this prosthesis can keep L4, 5 segments of the normal campaign, the rotation center is the oval-shaped movable〕
〔15 ~ 17. ProDisc ? also includes three parts: the cobalt-chromium alloy end-plate
appearance of Ti-coated, two vertical wing-like structure fixed to the vertebral body is
used, the ultra-high molecular weight polyethylene core filling in between the end plate. Another prosthesis Sofamor Danek (Memphis.TN) is currently being pre-clinical trials,
which consists of a metal ball and metal cup composition.
In October 2004, FDA formally approved the artificial disc SB Charité ? clinical L4
~ S1 applied to a single segment lumbar intervertebral disc degeneration. And 360 ?
spinal fusion contrast, ProDisc ? prosthesis multi-center trial randomized clinical
trials have been completed and concluded that all of its targets are met or better than the same test as the control of spinal fusion.
3 Indications and contraindications
The application of new technologies, patient selection is essential. ADR provides the current indications are: young, single segment disc degeneration, no osteoporosis, not accompanied by severe facet joint disease, is not associated with lumbar instability, no spinal stenosis or nerve root compression in the rear. FDA trials of these indications with the above inclusion criteria consistent with 〔10〕. In theory, stages of
intervertebral disc replacement suitable for degenerative disc disease. Due to the high medical costs and the potential risk, are now commonly used in severe degenerative disc disease. Many European scholars believe that the ADR symptoms of low back pain
indications including degenerative disc disease and lumbar disc syndrome, postoperative failure. United States Association of Orthopedic Surgeons (AAOS) to ADR indications as: (1) The symptoms of rupture disc; (2) symptomatic disc
degeneration; (3) spinal fusion due to instability of adjacent segment degeneration. Contraindications include: (1) segment of the spinal deformity surgery; (2) severe osteoporosis; (3) ? degrees lumbar spondylolisthesis; (4) bony spinal canal stenosis; (5)
surgical adhesions caused by scar of low back pain.
Four surgical methods
In Europe and the United States, ADR pass through the anterior extraperitoneal prosthesis implantation, and anterior lumbar interbody fusion (ALIF) approach
similar to. Surgical procedures (as an example artificial disc SB Charité ?) are briefly
described below 〔10〕: a small incision along the belly line, after extraperitoneal exposure to the spine in front-line standard anterior discectomy, be careful not to
undermine the bony end-plate. Intervertebral distraction by distraction pliers, design a good size prosthesis after implantation of prosthesis endplate. Prosthesis center location via anteroposterior X-ray identification, lateral view, the vertebral body from the
midline sagittal 2 mm backward ideal location. Polyethylene vertebra in determining the correct position after the implantation of the nuclear test, release the distraction pliers, film to confirm the success of implants, routine abdominal closure. At present
minimally invasive ADR has a certain development.
5 Clinical application of research findings
The U.S. FDA of the Charité ? artificial disc multi-center prospective study
conducted 〔10〕, 56 patients, the shortest follow-up period of 6 weeks, only 22
patients were followed up at 12 weeks or more, 52.7% of patients had VAS score improved, 39.2% of patients ODI score improved. McAfee et al 〔〕 23,24 reported
into the FDA test results of 60 patients, 41 patients with the Charité ? prosthesis OK
ADR, 19 were treated with BAK fusion cage OK ALIF, mean follow-up time for two
years, the results of two ODI score in patients before and after surgery had significantly improved, without prosthesis or graft failure due to dislocation has been
removed, the main complication is the result of the different surgical approaches.
FDA on the Charité ? prosthesis carried out two years of clinical follow-up 25,26
〔〕, 304 patients with 205 regular Charité ? prosthetic replacement, 99-line ALIF as
the control. 63% of the test group patients and 53% of the control group, clinical results were satisfactory, the test group after 6 weeks and 6 months follow-up ODI
score significantly improved, 75% of the test group and 70% of the control group
subjects VAS pain score markedly improved, 73% of the test group and control group 66% of patients improved quality of life score of at least 15%, Charité prosthesis group of patients with lumbar spinal activity 7.4 ?. Replacement after two years three cases of
prosthesis displacement Chao Guo 3 mm, the test group activity relative baseline lumbar spine increased by an average 13.6%, while the control group average of 82.5%, the test group was significantly higher in patients with intervertebral height (P
"0.05), prosthesis subsidence significantly lower than the control group. Concluded that: Charité prosthesis ADR efficacy in at least two years, ALIF quite. ADR surgery can restore and maintain the preoperative lumbar activity, compared with ALIF better
recovery in terms of ADR intervertebral space height and to prevent the prosthesis subsidence. Postoperative lumbar activity and clinical follow-up results there is an
association with surgical precision.
Cinotti et al 〔19〕 reporting application Charité ? prosthesis for ADR were 46
cases of 56 gaps, with an average follow-up of 3.2 years, 63% of patients with good
results. Past history of back surgery or have a two level disc disease in patients with poor postoperative results. Lemaire et al 〔18〕 application Charité prosthesis was
reported in a total of 105 cases of line ADR gap 154, with an average follow-up of 51
months, low back pain to improve the rate of over 90%, 87% of patients back to work. Zeegers et al 〔21〕 reporting application Charité prosthesis OK ADR 50 Li 75 gap, with an average follow-up period 2 years, 65% of patients with low back pain
symptoms were improved after operation, of which 15 patients taking painkillers after reduction or disabled, 43% postoperative recovery in patients with past work. 12
patients underwent surgery 24 times the renovation, of which seven re-operation due to
postoperative complications (such as postoperative hematoma), 6 is the segment of prosthesis implanted, 11 in other segments. Three cases of patients with permanent loss of feeling legs, 4 patients with sympathetic function is permanently blocked, 1 postoperative prosthesis displacement caused by artery damage. van Ooij et al 〔21〕
report of 27 cases of patients with Charité prosthesis OK ADR, the average follow-up
time of 53 months, the main late complication is the disc or the articular surface degeneration, as well as prosthesis subsidence.
Lemaire reported on the application of Charité prosthesis after the clinical and
imaging follow-up results 〔22〕, 100 patients were followed up for more than 10
years, a total of 147 prostheses implanted, 62% of the patients obtained excellent clinical results, 28% good results , 10% poor efficacy, 95 patients return to work,
63.2% of patients with heavy physical labor to restore the original work. All surgical segmental flexion and extension activity for an average of 10.3 ?, the average lateral activity of 5.4 ?. Sagittal, the 6.1% partial prosthesis prior to implant the middle 34%,
59.9% after partial prosthesis Location Center; coronal plane, 75% of the prosthesis center, 25% partial lateral prosthesis. 1 case of intervertebral disc height loss of 1 mm, 2 patients were found in mild prosthesis subsidence, but do not require secondary
surgery. Prosthesis subluxation does not appear, no spontaneous spinal fusion, 5 patients undergoing posterior spinal fusion stage ?, excellent rate of 90%, after at least
10 years of follow-up, Charité artificial disc has excellent lateral flexion and extension,
and the activities of degree and no significant complications, the literature is superior to the efficacy of spinal fusion.
Putzier M recently reported ADR after 17 years of clinical and imaging follow-up
results 〔28〕. 71 patients with moderate to severe DDD patients were implanted with 84 Charité ? ~ ? prosthesis, 53 patients have been in 17 years follow-up, 60% of
patients after the Charité artificial disc replacement has led to spontaneous spinal fusion, 3 types prosthesis there was no significant difference in clinical outcome, 11% of patients need further surgery, although 17% of patients was not observed near the artificial disc implant segment degeneration occurred, but these patients than those in patients with spontaneous spinal fusion satisfaction is lower. ADR was intended to preserve spinal segmental function, and then replace spinal fusion. After short-term
effects can be sure, but the lack of long-term results were reported. The current lack of
outcome long term follow-DDD, as evidence that patients with more effective than
ADR, or at least equivalent to spinal fusion.
Charité ? present the findings of intervertebral disc prosthesis demonstrated a
certain extent, it determines the success, but the literature reflects the problems and
contradictions are also evident. So far, most published clinical series of studies on a smaller sample size, the lack of randomized controlled, incomplete reporting of complications, the lack of long-term follow-up results. The failure rate of clinical
application of long-term pain relief as well as the choice of revision surgery several issues must be resolved.
Bertagnoli reported that the application ProDisc ? OK ADR 108 Li 134 clearance,
more than 90% of the postoperative results were satisfactory 〔24〕. Of which only 54
patients were followed up 1 year, with an average follow-up time is not reported.
Prosthesis implantation on the ProDisc ? Imaging Evaluation of late results showed
that 〔29〕 s technology, measured at different levels of spinal flexion and extension of the average degree of 3.2 ? ~ 4.5 ? in between. If the implants are degeneration of the adjacent intervertebral disc implanted prosthesis segment of activity relative to the adjacent intervertebral disc lesions in patients with non-
significantly reduced, with an average 1.6 ?. A certain extent, this result also supports the retention of the activity segment lesions can reduce adjacent segment degeneration occurred assumptions. Tropiano et al 〔30〕 reported 53 cases of application of this
prosthesis trip single or multiple levels of disc replacement clinical results, with an average follow-up period was 1.4 years, low back pain, and ODI score had significantly improved, 72% of patients back to work. Complications include vertebral fracture in 1 case, prosthesis displacement in 2 cases, nerve root pain in 2 cases, of which three routine refurbishment operations.
Zigler et al 〔31〕 reported on the ProDisc prosthesis FDA multi-center prospective
study of early results of the test group were treated with ProDisc ? prosthesis OK
ADR 28 cases, the control group implanted with iliac 360 ? spinal fusion in 11 cases, 6 months of follow-up results showed that application of ProDisc ?-line ADR can
shorten the patient recovery time, increase patient satisfaction advantages. Clinical trials for the experimental group concluded that all of the indicators are at or better than the same test as the control group, spinal fusion surgery. Tropiano et al 〔32〕
reported on the application of ProDisc ? prosthesis 7 ~ 11 years of clinical and
improved, 55 patients with excellent results in 33 cases, 8 were benign and 14 cases of
poor, gender and multi-segment does not affect the efficacy of surgery, imaging
revealed no prosthetic loosening, displacement, or mechanical failure, 5 patients presented with approach-related complications.
Two kinds of new metal -
Minneapolis, MN), and FlexiCore (Spinecore, Summit, NJ) is the United States clinical trials, there were no relevant information reports. Reposted elsewhere in the paper for free download http://
Discussed earlier two kinds of prosthesis is currently the most widely used, but they do not represent the field of lumbar intervertebral disc replacement all of the current design, technology and research, many other pre-clinical trial prosthesis is 〔11〕.
Present authors can get the following conclusion: short-term effects of pain relief and
functional recovery is good; the current prosthesis implanted in the short term is relatively safe; complications, and surgical approach is often, the operation related to
the early transplant is not a failure; compared to spinal fusion, shortening the postoperative recovery time. There are several issues not fully resolved: (1) relative to the long-term effects of spinal fusion surgery, which design and technology in the end
there is no real sense of progress; (2) degree of pain relief and activities to maintain the long-term effectiveness; ( 3) The body of these prosthesis fatigue resistance and service life is; (4) Prosthetic and production of polyethylene wear debris whether the prosthesis caused by peripheral nerve tissue damage late; (5) renovation might have problems during surgery and how to resolve; (6) whether these artificial prosthesis, as we expected, as can prevent a small joint disease and adjacent segment degeneration of the
emergence and progress. Abroad a large sample of clinical trials and sequence of study will be a good impetus to the above interpretation of several issues that may be 5 to 10 years after follow-up results in patients with long-term statistics came out to get
Authors lumbar intervertebral disc replacement cautiously optimistic. While the experienced surgeon to do this surgery short-term result is good, but require long-term
clinical follow-up and research to improve surgical methods, techniques and prosthesis design. Now, there are several problems remained unsolved: prosthesis design successes and pitfalls of how to determine the current ADR indications are correct and whether
they meet the actual needs of a large sample of clinical applications are a long-term
follow-up data of cases tested. In materials science on the basis of the development of further research, including animal models, laboratory studies and clinical research, will
continue to improve implant design and material choices.
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