4th German Spine Conference, ADR Notes: European Spine Journal 2009 Nov

[Slackwater]

Eur Spine J (2009) 18:1713–1826
DOI 10.1007/s00586-009-1188-1
© 2009 Springer

Abstracts V65 (below, 93 patients) and P176 (far below, 335 patients ActivL and ProdiscL) have different results on facet joint degeneration with ADR (artificial disc replacement). Follow-up is 53 months average and 3 year minimum respectively for the abstracts.

LP.ESP is a viscoelastic ADR, mentioned in two (2) abstracts below.





V 65
Facet Joint and Adjacent Level Degeneration following Total Lumbar Disc Replacement: A Prospective Clinical, X-Ray and MRI Investigation
C.J. Siepe 1, P. Zelenkov 2, J. Sauri-Barraza 3, U. Szeimies 4, R. Beisse 1, A. Korge1, A. Stäbler4, H.M. Mayer 1
1 Orthopädische Klinik München-Harlaching, Wirbelsäulenzentrum, München;
2 Burdenko Institute of Neurosurgery, Department of Spine Surgery, Moskau, Russland;
3 Centro Médico ABC, Orthopaedic Department, Mexico City, Mexiko;
4 Radiologisches Institut München-Harlaching, München

Introduction: Fusion procedures have been associated with adjacent level degeneration (ALD) and facet joint degeneration (FJD) in a considerable number of patients. Whether the incidence of these negative side effects can be reduced with total lumbar disc replacement (TDR) remains unestablished.

Materials and Methods: Clinical outcome scores Visual Analogue Scale (VAS), Oswestry Disability Index (ODI) and patient satisfaction rates were acquired within the framework of an ongoing prospective study with ProDisc II. The mean index level ROM was established for every patient over the entire post-operative period. The progression of ALD and FJD was evaluated from pre- and postoperative MRI images by 2 independent radiologists.

Results: 93 patients with an average FU of 53.4 months (range 24.1-98.7 months) were included in this study. The overall results showed a significant improvement from preoperative VAS and ODI levels (p<0.0001). The incidence of ALD was 10.2% (n=11/108 levels). The degenerative changes were mild and occurred late postoperatively (mean 65.2 months, range 37.9 - 85.6 months). There was no significant correlation between index-level ROM and the occurrence of ALD (p>0.05).

Progression of FJD was observed in 20.0% of all facet joints (n=44/220). FJD occurred significantly more often at the lumbosacral junction in comparison to the level above the lumbosacral junction (p<0.02) and was observed more frequently at index-levels than at non-index levels (p<0.001).

The degenerative changes were associated with a negative influence on postoperative outcome parameters VAS and ODI (p<0.03) that were already detected early postoperatively. The mean postoperative ROM was significantly lower in patients with FJD in comparison to the remaining cohort (p<0001).

Conclusion: Total lumbar disc replacement (TDR) proved to have a beneficial effect with regard to adjacent segment preservation. Progressive index-level facet joint degeneration (FJD) was observed in a considerable number of patients, particularly at the lumbosacral junction. Lower segmental mobility and less favourable clinical results point to the fact that a particular cohort of patients may predominanty be affected in which TDR shows inferior compatibility with the index segment´s biomechanics.


V 66
Radiological and clinical investigation of adjacent – segment
disease after cervical disc replacement versus fusion: Five
year’s results
A. Nabhan1, B. Ishak1, W.-I. Steudel1
1Uniklinik Homburg, Neurochirurgie, Homburg/Saar

Introduction: Disc prostheses have been designed to restore and maintain cervical segmental motion and reduce the accelerated degeneration to the adjacent level. In vitro studies could show that fusion promotes higher internal stresses in the disc adjacent to fusion and that these can lead to adjacent - segment disease. However the objective was to determine the incidence of radiological changes and symptomatic adjacent level cervical disc disease after cervical disc replacement in comparison to patients received anterior cervical discectomy and fusion.

Methods: The patients were treated either with anterior cervical discectomy and fusion (25 patients) or the Pro Disc C Artificial Cervical Disc (24 patients). For each group the patients were required to undergo serial cervical radiography preoperatively and 5 years postoperatively, as well as clinical evaluations including Visual Analogue Scale (VAS) and Neck Disability Index (NDI). Indicative of adjacent-level disease were radiological findings with new anterior osteophyte formation or enlargement of already existing osteophyte, increased narrowing of disc space, new DDD, and calcification of the anterior longitudinal ligament.

Results: Fusion was accompanied by a significant increase in degenerative change of adjacent-disc evaluated by x-ray films (p < 0,05) in comparison to patients received artificial disc. The incidence of the clinical symptomatic evaluated using VAS and NDI was also significant higher in the fusion group (p < 0,05). The patients treated by fusion procedure required statistically more revision surgeries to the adjacent level than the prostheses group.

Conclusion: This prospective study did show that maintaining segmental motion rather than fusion will prevent symptomatic adjacent-disc disease and will decrease adjacent – segment radiological findings five years after surgery.


P 7
Kinematic Evaluation of Cerkinetic™: A New Cervical TDR
with Novel Geometry of Bearing Core Mechanism
R. Bostelmann1, M. Leimert2, M. Klingenhöfer1, P. Slotty1, C. Wille1, M. Wild3
1 Heinrich Heine Universität Düsseldorf, Neurochirurgische Klinik, Düsseldorf;
2 Technische Universität, Neurochirurgie, Dresden;
3 Heinrich Heine Universität Düsseldorf, Klinik für Unfall- und Handchirurgie, Düsseldorf

Introduction: Anterior cervical discectomy and fusion (ACDF) may result in progressive degeneration of adjacent level discs and facets in the cervical spine. Total Disc Replacement (TDR) was introduced in order to overcome these ACDF's physio-pathologic consequences, as well as to preserve inter-somatic motion. However, various studies report that these abnormal accelerated degenerative processes still occur after TDRs despite their motion capacity. TDR's Kinematic properties should emulate the natural disc motion qualities as closely as possible in order to avoid motion patterns which are extraneous per nature to the cervical spine dynamic scheme.

Purpose: the prime objective of this project was to quantify the motion attenuation properties of the Cerkinetic™ - a novel cervical TDR of OrthoKinematica Ltd. expressed as stiffness (Nm/deg). Namely, ultimate moment (Nm) corresponding to angular displacement (deg). A secondary objective was to describe the correlation between geometrical configuration and the motional outcome enabling the Cerkinetic™ to reproduce the natural disc kinematics, including properties conferred by the visco-elastic physics of the natural disc in a Metal on Metal (MOM) cervical TDR.

Method: Six Cerkinetic™ implants were tested for static angular displacement and the required applied moments in a preload mode of 150N to 10° in torsion, 8° in flexion/extension and 8° in lateral bending using INSTRON 8874 testing device. Static Axial test protocol followed the ASTM F2346-05. The lateral bending and flexion/extension torsion test protocol was designed to adapt to the guidelines delineated by ASTM Standard F2346-05 Standard Test Methods for Static and Dynamic Characterization of Spinal Artificial Discs. The procedures and their analysis criteria were applied to the two additional orthogonal axes of the 3D Cartesian system: Lateral Bending and Flexion/Extension. The geometrical configuration of the device's bearing core is designed to provide the non linear motional resistance to angular displacement - which is the characteristic pattern of the natural disc harbored within the cervical inter-somatic C3-C7.

Results: The mean moments versus angular displacements are summarized as follows (Fig. 1): Static Axial Torsion Ultimate Moment (Nm 1.92), Displacement (deg) 9.97; Static Flexion/Extension Ultimate Moment (Nm 1.01), Displacement (deg) 7.98; Static Lateral Bending Ultimate Moment (Nm 1.16), Displacement (deg) 8.00.

Conclusion: It is of crucial importance to provide an artificial TDR which can emulate kinematic features of the natural disc. Such emulation preserves: a) the properties conferred to the interspace by it visco-elastic nature; b) intervertebral height; c) foraminal patency; d) motion pattern of the specific treated interspace; e) intervertebral and global cervical spine column dynamic scheme.

Kinematic testing shows that all these properties have been reproduced in a MOM Prosthesis.


P 81
BAGUERA® C cervical disc replacement – Multicentric clinical study: Results up to 2 years follow up
G. Maestretti 1
1 Hôpital Cantonal de Fribourg, Service de Chirurgie Orthopédie, Fribourg, Schweiz

Introduction: Baguera® C cervical disc replacement is currently undergoing clinical evaluation in a Multicentre European Observational Study.The purpose of this study is to assess safety and efficacy of this procedure with early clinical and radiographic outcomes.

Materials and Methods: A series of 68 cases implanted from February 2007 to February 2008 in 4 European sites were studied with an average of 14 months follow up (range 4 to 24 months). Clinical outcomes were recorded with the following scores: VAS (Visual Analog Scale) pain scores and NDI (Neck Disability Index), at the following intervals: preoperatively, 3 months, 6 months, 12 months, and 24 months postoperatively. Intraoperative and postoperative complications were recorded. Radiographs included MRI, AP/lateral, flexion and extension Xrays preoperatively and at different intervals postoperatively.

Results: Out of 68 patients, 23 patients were male and 45 female. The average age for the group was 50 (range 25 to 72). Surgical procedures were as follows: 51 one level cases, 16 two level cases and 1 three level case. There was one procedure at level C3-C4, 3 at level C4-C5, 32 at level C5-C6 and 15 at level C6-C7. For the two level cases, there were 2 procedures at levels C3-C4 and C4-C5, 3 at levels C4-C5 and C6-C7, 11 at levels C5-C6 and C6-C7. The three level case was at the levels C3-C4/C4-C5/C5-C6. The operative time averaged 89 minutes (range 55 -160 minutes). Over a period of 12 months follow up for 22 patients, VAS (neck) was down from 5.9 to 1.8 and VAS (arm) was down from 7.4 to 0.9. NDI scores similarly decreased from 33.5 to 10.7.Over a period of 22 months follow up for 46 patients, VAS (neck) was down from 6.3 to 2 and VAS (arm) was down from 7.3 to 1.2. NDI scores similarly decreased from 32.5 to 9. Clinical outcomes reveal significant improvement in VAS and NDI scores.

Conclusion: Baguera® C has presented good clinical outcomes, both in terms of recovery of functionality and the reduction of postoperative pain. This technique seems to allow the restoration of both the mobility of the disc and the morphology of the cervical spine. The low ratio of complications and adverse events reported postoperatively is encouraging for the continuity of implantation and the use of this surgical procedure. Moreover, this technique allows multilevel implantation due to its design. Further data and longer term follow up are ongoing.


P 82
Outcome after cervical arthroplasty: Clinical and radiological follow-up with comparison of two types of prostheses
A. Grimmer1, M. Sonnberger2, J. Zöhrer1, B. Parsaei1, T. Narovec1, G. Wurm1
1 Landesnervenklinik Linz, Abteilung für Neurochirurgie, Linz, Österreich;
2 Landesnervenklinik Linz, Radiologisches Institut, Linz, Österreich

Introduction: Anterior cervical discectomy and fusion is an established procedure in case of cervical degenerative disc disease. Fusion of a segment, however, may lead to increased forces at the levels above and below the operated segment resulting in adjacent segment degeneration. An alternative to fusion procedures is cervical disc prosthesis with the aim of restoring near-normal spinal motion and potentially reducing adjacent segment degeneration. In a retrospective study, the clinical and radiological results before and after cervical arthroplasty were evaluated.

Patients and Methods: Between April 2002 and November 2007, 207 patients received 273 cervical disc prostheses in our department. 71 patients received Bryan and 136 Patients Prestige Prostheses.

The mean duration of preoperative clinical symptoms was 22.4 months (range 0-180). They had symptomatic myelopathy (n=69) and/or radiculopathy (n=157), with neck pain (n=153), motor (n=118) and/or sensory deficit (n=174). Predominant pain in the arm was found in 129 patients (66.2%), and predominant neck pain in 67 patients (34.2%). A single level operation was done in 150 patients (72.5%) and multilevel procedures, up to 4 levels, were performed in 57 patients (27.5%). In the clinical follow-up (mean 2.2 years), we examined the pre- and postoperative VAS for neck and arm, the NDI, the neurological status and the degree of satisfaction with the operation. In the radiological follow-up we investigated the ROM on disc level, on the FSU and C2-7 and the number of fusions. For statistical analysis, we used the Fischer Exact Test and the Wilcoxon Test. The influence of different covariables was calculated with different regression models.

Results: In the clinical follow-up, radicular arm pain disappeared in 100/145 patients (69%), and was improved in further 38 patients (26.2%). The myelopathic symptoms disappeared or improved in 57/67 patients (85.1%). For all patients, even for those with myelopathy, a high significant improvement was found in VAS for arm and neck pain in which arm pain improved
more than neck pain. There were no significant differences for VAS and NDI in the two types of prostheses. 171/183 (93%) patients were content with the operation results.

In the radiological follow-up, we found in single level operated patients a high significant improvement of ROM at the disc level (3.1 degree) and in C2-7 (8.4 degree). Multilevel patients showed no significant improvement of motion in C2-7. 11/64 (17.6%), who had a preoperative ROM >2 degrees, showed no movement at the disc level (ROM <2 degree) in the follow-up. A higher risk of fusion is suggested for patients with a Prestige Prosthesis (22.73%) than for patients with Bryan Prosthesis (14.29%). No correlation was found between clinical improvement and improvement of postoperative ROM.

Conclusion: Our preliminary results suggest that patients whose predominant preoperative pain had been in the arm improved more than in those with neck pain. Long term follow-up is needed to determine, if patients treated with arthroplasty have more clinical improvement, than those with cervical decompression and fusion alone.

P 84
Operational demographics and clinical results of 100 consecutive artificial cervical disc replacements
H. Poimann1, K. Thießen2, H. Fröhlich1, R. Popp1, J. Harth1, M. Schaefer1
1 Neurochirurgische Praxisgemeinschaft, Neurochirurgie, Würzburg;
2 Rotkreuzklinik, OP, Würzburg

Introduction: Prospective, consecutive series of 100 patients with prosthetic implantations, that were concurrently enrolled between four different kind of prothesis. Operative demographics
and clinical result of 80 single level cervical disc replacements and 20 two level operations were investigated.

A second aim was to compare both clinical success as well as operative demographics to known figures in current literature.

Material/Methods: Surgery was performed at no more than 2 continuous levels by four expierenced neurosurgeons. 100 unselected consecutive patients suffering from radiculopathy/myelopathy due to degenerative disc disease/cervical spondylosis were undergoing disc replacement. Mean follow-up time was 16 month. We evaluated intraoperative bloodloss, length of surgery perioperative complications the learning-curve of the surgeons and the patients neurological and functional outcomes.

Results: The four types of prothesis (49 Spinal kinetics and 22 Bryan, 19 Pro Disc, 10 Prestige) were 8 times two level prothesis, 80 single level disc replacements and 12 hybrid solutions. There is no significant difference between the four types of prosthesis (p.<.05). Compared to results reported in literature (1-6) there are no real differences either to other series of disc replacement or results regarding to anterior cervical discectomy and fusion (ACDF). There is no noticeable ossification and good range of motion as shown by functional x-rays. Operative demographics showed a length of surgery of 120 (+/- 26) minutes, a measured blood loss of 91 (+/- 116.49) ml and 2 % tissue lesions. 32 % of the patients were without any complaints, 42 % without neck pain, 76 % without radiculopathy, 46 patients didn`t need any more treatment by a doctor and 51 % didn`t take any medication at all. The improvement in the VAS was from 8.08 to 2.02 postoperatively. The odom's were 59 % excellent, 22 % good, 10 % fair and 9 % poor results. 89 patients went back to work and 11 patients retired. Over-all-patients satisfaction with surgery was 6.17(on a scale 1 (poor)- 7 (excellent)) 89.47 % would choose the same treatment again. There was no persisting neurologic defects regarding to muscular paresis; disturbation of sensibility persisted in 14 %.

Conclusions: Disc replacement is a safe procedure with very good clinical and functional results. It provides an excellent alternative to fusion regarding the individual patients preoperative situation. In order to proof the superiority of artifical disc replacement to ACDF large trials with strict randomization are still to be done.


P 89
Cervical disc replacement with Discocerv® mobile disc prosthesis – the United Kingdom experience
S. Tucker1
1Royal National Orthopaedic Hospital, Stanmore, UK

Introduction: Cervical disc arthroplasty preserves motion and is supposed to improve load transfer to the adjacent levels, thus overcoming adjacent level degeneration which is a major drawback of fusion. Though literature shows comparable early results between cervical arthroplasty and fusion, mid and long term data is needed to evaluate its outcomes, especially as new implant-related complications may occur, such as heterotopic ossification. The present study shows the UK clinical experience of cervical arthroplasty with a ceramic on ceramic mobile disc prosthesis of specific anatomical profile that avoids the conflict with uncii (and the subsequent need for substantial bone resection leading to heterotopic ossification).

Material and Methods: 127 patients were enrolled in this prospective non comparative study, with a male: female ratio of 1.1; average age 51.4 ± 7 years. 2.4% of patients had previously undergone cervical spine surgery, 26% were smokers and almost a half presented significant comorbidity: i.e. 12.2% were hypertensive; 2.4% were diabetic and 2.4% presented ischemic heart disease. Main symptoms were: axial neck pain in 27.3%, radicular pain only in 27.3% and combined neck and radicular pain in 45.5%, treated in all patients by cervical arthroplasty with Discocerv mobile disc prosthesis. The device is constrained, limiting the mobility to 18° and fixing upwards (with regard to the lower vertebra) the axis of rotation in sagittal and frontal planes. Patients were followed up to 24 months and pain (VAS scale), function (Neck Disability Index) and quality of life (SF36) were evaluated, as well as flexion-extension mobility and axis of rotation from X-ray films. Statistical significance was set at 0.05 for comparison of score and mobility values before and after surgery by means of paired Student t test.

Results: Single level surgery was performed in 89.7%, two-level surgery in 9% and three level in 1% of cases. The average length of surgery was 79 minutes with a range of 55-120 minutes and
average patient hospital stay was 3 days. There were no immediate operative complications but some were observed postoperatively (1 case of each): transient dysphagia, superficial infection, implant subluxation and spontaneous fusion around the implant, possibly related to implant malpositioning. Improvements in SF36, VAS, and NDI scores were seen from preoperative levels in all but one patient (statistically significant between preoperative and immediately postoperative values p<0.001 and stable afterwards). Flexion-extension mobility was preserved in all but one case.

Discussion: Early results with the cervical disc arthroplasty suggest results similar to fusion literature data with respect to the improvement in pain, function and quality of life. Motion within the operated segment has been preserved in all but one patient. Cervical disc replacement with a ceramic on ceramic prosthesis seems to provide satisfactory clinical outcomes with low surgical morbidity and low rate of implant related complications. However, longer term follow-up is needed to evaluate motion preservation and its impact on the incidence of adjacent segment degeneration.


P 90
A dynamic cervical disc replacement - in between fusion and prosthesis
J. Herdmann1, P. Buddenberg1, S. Rhee1, A. Pilz1, F. Floeth1
1 St. Vinzenz-Krankenhaus Düsseldorf, Klinik für Wirbelsäule & Schmerz, Düsseldorf

Introduction: The aim of most new implants for cervical disc replacement is to maintain or restore function. In the past years there have been a large number of reports on advantages and disadvantages of cervical disc arthoplasty with prosthesis. Limitations for the use of prosthesis are restricted indications, secondary fusion, possible overdistraction and a number of design specific complications.

The new Dynamic Cervical Implant (DCI) aims at combining the advantages of the save gold standard fusion technique with the motion preservation philosophy. DCI has a limited motion: it
works like a shock absorbing spring and may help to slow down adjacent segment degeneration.

Material and Methods: Between April 2007 and May 2009 52 patients (29 women and 23 men) aged 32 to 73 years were selected for motion preservation with DCI (Paradigm Spine) at either one or two levels (9 patients). Indications were radiculopathies (n=29), axial pain (n=2) or spondylotic stenosis (n=21) due to disc hernia or degeneration. Hypermobility was an exclusion criterion. Flexion/extension radiographs were obtained before treatment, at dismissal, and at 3, 6, and 12 months after surgery.

Results: Disc surgery was performed at C3/C4 (n=3), C4/5 (n=5), at C5/6 (n=29) ant at C6/7 (n=24). In flexion/extension radiographs motion rapidly increased after surgery. However, 8 of 61 treated levels were fused (seen at 6/12 months). In 7 of 8 segments fused an implant of insufficient size had been used (initial phase trial). Implant footprint was changed and larger sizes are now provided. In one patient subsidence of the implant into the endplate was seen. Still 94% of the patients rated their clinical result as excellent or good. There were no further implant related complications.

Conclusions: Disc replacement with DCI is a completely new strategy that is positioned in between anterior cervical fusion and disc prosthesis. Up to now (date of abstract submission) we can only report about initial results in an early trial of patients that is continuously followed up. Clinical results are as good as in anterior cervical fusion. Adjacent segment protection must be judged in future follow-ups, especially with regard to the high fusion rate in our early series. We were able to show that the change of implant footprint has helped to reduce fusion rate.


P 134
Total lumbar disc replacement with a 6 degrees freedom prosthesis LPESP®: 5 years clinical experience, effects on kinematic, sagittal balance and clinical outcomes
J.Y. Lazennec 1, J. Even 1, H. Pascal Mousselard 1, O. Ricart1 J.P. Rakover 1, H. Afshar 2, M.A. Rousseau 1
1 Hopital La Pitié, Paris, Frankreich;
2 Klinikum Leer, Leer


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. The LP.ESP® disc is the first bi-composite
polymeric implant achieving 6 degrees of freedom (DOF), including shock absorption and elastic return. The authors report their 5 years pioneering experience including more than 400 implantations.

Material and Methods: The LP.ESP II ® is a one piece deformable implant made of silicon gel with micro voids and surrounded by polycarbonate polyurethane securely fixed to titanium endplates. The endplates have five anchoring pinches to provide primary fixation and are covered by hydroxyapatite to provide optimal bone ingrowth. This geometry allows limited rotation and translation with elastic return. The concept is to authorize more liberty to the rotation centre and a growing resistance in each direction of solicitation to avoid hyper solicitation on posterior facet joints. The prosthesis was implanted through a anterior retroperitoneal or transperitoneal approaches for L4L5 and L5 S1 levels. Medical data and radiographs were prospectively analyzed and compared using a paired t test.

Results: Mean range of motion in flexion-extension averaged 5.0 degrees (Range 0 to 21.6°) with 4.8 degrees of standard deviation. If we consider that prosthesis with a ROM under 2° have no motion, 68 % had a motion, the mean ROM is 7.5° with 4.5 degrees of standard deviation. The mean centre of rotation was in a usual area in 87.5%. The coordinate of the MCR LPESP prosthesis seems similar to those of natural disc described in literature. The MCR location tends to normalize itself during the first year. On sagittal balance, pelvic tilt, sacral tilt and segmental lordosis were significantly improved with respectively 16.7±7.8, 36.5±1O.6 and 19.4±6.7 degrees preoperatively and 12.9±6.5, 40.1±9.8 and 27.8±7.8 degrees at last follow-up. Disc height was fully restored after implantation. ROM, MCR, disc height of the adjacent upper level did not change during the follow-up. No intraoperative complication occurred. There was no device related complication. Clinical scores were all significantly improved, respectively 4. 8 points for the back pain visual analogue scales (VAS), 33.8 points for the Oswestry disability index (ODI), 3.8 points for the SF36 and 17 points for the GHQ28.

Conclusion: Elastic one device prosthesis is a different concept than low friction prosthesis usually used in lumbar spine; it allows 6 degree of freedom to not constrain the instantaneous
axis of rotation and reduce facet forces. Despite the limitation of our study due to the follow-up duration, it appears that LP.ESP® prosthesis is able to recreate a function to the lumbar spine similar tothe healthy disc in terms quality of movement, effect on sagittal balance and absence of modification in the kinematics of the upper adjacent level.



P 143
Is the final outcome predictable following total lumbar disc replacement?
C.J. Siepe1, A. Tepass2, W. Hitzl3, P. Meschede1, R. Beisse1, A. Korge1, H.M. Mayer1
1 Orthopädische Klinik München-Harlaching, Wirbelsäulenzentrum, München;
2 PMU, Salzburg, Österreich;
3 Paracelsus Medizinische Universität, Dept. Biostatistics, Research Office, Salzburg, Österreich

Introduction: Previously published TDR studies reported on the pooled data averages collected from various cohort sizes. The individual patient´s prognosis as well as prognostic factors of postoperative improvement remain un-established. The objectives of this study were to to examine whether baseline variables VAS (Visual Analogue Scale) and ODI (Oswestry Disability Index) correspond with late and final postoperative outcome parameters and to identify early predictors of late outcome following TDR.

Materials and Methods: Data were accumulated prospectively and included VAS and ODI scores. The subjective outcome evaluation was based on a 3-scale grading system (´highly satisfied´, ´satisfied´, ´not satisfied´). An analysis was performed to ascertain whether the late and final outcome following TDR can be prediced based on preoperative and early postoperative data from the 3 and 6 month follow-up (FU).

Results: The overall results from 161 patients with an average FU of 4 years (mean 45.5 months, range 24.1 - 94.4 months) revealed a significant and maintained improvement of VAS and ODI scores (p<0.0001). The most pronounced changes occurred within the early postoperative period (p<0.0001) with no significant changes thereafter (p>0.05). Baseline ODI levels were significantly correlated with VAS / ODI scores and patient satisfaction rates at the final FU (p<0.0001). postoperatively, early and late ODI levels were highly significantly correlated with each other (r=0.84, p<0.0001). Similar associations were observed between early and late VAS scores and patient satisfaction rates (p<0.006). The individual patients subjective outcome evaluation revealed stable postoperative results. An improvement or a deterioration by 2 classes on a 3-scale grading system was only observed in 3.1% (n=5/161) of all cases overall. Patients with an early ´highly satisfactory´ result (n=83) maintained either a satisfactory (15.7%, n=13/83) or a highly satisfactory outcome (79.5%, n=66/83) in 95.2% of all cases (n=79/83). Conversely, the probability that patients with an ´unsatisfactory´ outcome would still achieve a ´highly satisfactory´ result after the early postoperative period was 5.0%.

Conclusion: Baseline ODI and early postoperative outcome parameters (<= 6 months) revealed significant and strong associations with the final results following TDR. Whilst the vast majority of patients with an early highly satisfactory outcome maintained satisfactory results at later FU stages, any significant improvement considered as ´highly satisfied´ is unlikely in a group of patients which reported early unsatisfactory results. In summary, any clinically relevant changes are unlikely to occur after the early postoperative period. The current findings offer a foundation for weighing both the patients and the spine surgeons expectations against possible realistic achievements. Whilst the data show that the mid-term outcome is predictable following TDR, the long-term results of lumbar disc replacements still need to be established.


P 144
Impact of implantation technique on sagittal and frontal alignment after total lumbar disc replacement:
Comparison of anterior versus oblique implantation
R. Schmidt1, B. Cakir2
1 Orthopädisch-Unfallchirurgisches Zentrum, Uniklinikum Mannheim, Mannheim;
2 Uniklinikum Ulm, Orthopädie, Ulm

Introduction: The concept of total lumbar disc replacement (TDR) is gaining acceptance due to good clinical short-term outcome. Standard implantation is strict anterior, which poses especially above the segment L5/S1 sometimes difficulties due to the vessel configuration. Therefore oblique implantable TDR have been invented. In oblique implantation the anterior longitudinal ligament (ALL) is only partially resected, with additional partial resection of lateral annulus fibers. This could have an impact on biomechanical properties, which has not been evaluated until now.

Material/Methods: We therefore compared the standing ap and lateral x-rays pre- and postoperative after anterior and oblique implanted TDR in segment L4/5 concerning segmental and total lordosis, as well as segmental and total ap balance.

Results: Significant differences between the groups were not found. In both, the anterior and oblique group segmental lordosis showed a significant increase, wheras total lordosis as well as ap balance was unchanged. The absolute segmental lordosis increase was nearly double in the anterior group.

Conclusion: In conclusion both anterior and oblique implanted TDR significantly increase segmental lordosis while retaining total lordosis and ap balance. The segmental increase is lower in the oblique implanted group which is probably due to the remaining ALL. Further studies should evaluate whether this finding has any implication for the long-term outcome, e.g. lower incidence of facet joint arthrosis after lumbar disc replacement.



P 147
Results of Pilot Study with a Viscoelastic Lumbar Total Disc Replacement – Freedom Lumbar Disc (FLD)
B. Rischke 1,2, R. Ross 3, B. Jöllenbeck 4
1 Spine-Center-Rischke, Klinik Lindberg, Winterthur, Schweiz;
2 DRK Klinikum Westend, Klinik für Orthopädie und Unfallchirurgie, Berlin;
3 BUPA Hospital, Orthopaedic Surgery, Manchester, UK;
4 Universität Magdeburg, Neurochirurgie, Magdeburg


Background: Lumbar fusion and first generation total disc replacements (TDRs) have been used for the treatment of symptomatic degenerative discs with equivalent outcomes. A viscoelastic TDR designed to mimic the native function of the disc, including three dimensional motion, dynamic stiffness, load sharing capability, and proper maintenance of lordosis may provide a more promising alternative to fusion than first generation TDRs.

Purpose: To evaluate the safety of a novel viscoelastic one-piece TDR.

Design of prosthesis: The one-piece viscoelastic disc prosthesis demonstrates stiffness within the ranges of stiffness of the natural disc in flexion, extension and compression: 2 Nm/degree in flexion and extension, and 0.5 to 3.5 kN/mm in compression. The compressive stiffness increases with increasing load, as does that of the natural disc.

Study Design: Fifty patients with back pain who were unresponsive to non-operative strategies were enrolled in a three site clinical trial and underwent L4/L5 or L5/S1 disc replacement. All 50 patients were assessed clinically and radiographically at 6 weeks and 3, 6, 12 and 24 months.

Results: The operative level was L5/S1 in 37 and L4/L5 in 13. There were no intraoperative complications, but there was one revision 17 months post-operatively. Quantitative x-ray assessment indicates that the viscoelastic disc maintains lumbar lordosis, restores and maintains a physiologic disc height, and provides flexion/extension range of motion and translation similar to the native disc. Mean preoperative ODI scores decreased from 48% pre-operatively to 24% at two years. Mean VAS scores decreased from 7.1 to 2.7 cm for back pain. SF-36 physical and mental component scores also improved significantly.

Conclusions: This viscoelastic TDR (Freedom Lumbar Disc) appears to be safe and performs as intended in the treatment of symptomatic lumbar degenerative discs. The implants maintained alignment and motion of the spine.


P 157
Treatment of discogenic low back pain by total disc arthroplasty using the Prodisc Prosthesis:
Analysis of a prospective cohort study with five-year clinical follow-up
G. Maestretti1, N. Reischl1, B. Titus2, F. Balague2
1 Hopital Cantonal Fribourg, Orthopädie, Fribourg, Schweiz;
2 Hopital Cantonal Fribourg, Rhumatology, Fribourg, Schweiz

Introduction: Few studies are available of the long term outcome of discal arthroplasty using the prodisc prostheses. The goal of this study was to independently evaluate weather the total disc arthroplasty using the Prodisc Prosthesis can fulfil the expectations as a reliable treatment option for disabling low back pain, and weather a long lasting improvement of quality of life can be achieved.

Material/Methods: An analysis of a prospective cohort study with a mean of 5-year follow-up, clinical control, done by non involved rheumatologists should give us a data that is not influenced by the surgeon bias. Included were all patients (N39) undergoing discal replacement between May 2002 and July 2004. A total of 52 levels from L2 to S1, of those 28 single 9 double and 2 three levels were treated. Clinical independent evaluation by non involved rheumatologists was done preoperatively, at 1, 2 and 5 years after surgery. The Visual Analogue Score for leg and lumbar pain intensity, the Oswestry low back pain disability scale, the Short Form-36, the Patient satisfaction and the Return to work were assessed.

Results: The analysis showed a significant amelioration of the Visual Analogue Score for back and leg pain, as well as for the Oswestry low back pain disability scale and the short-Form 36 (SF-36). The Visual analogue score for back pain a decrease from 7,4 (mean) before surgery to 4,6 after 1 year, 4,6 after 2 years and 4,4 (P< 0.0001) after 5 years. The Visual analogue score for the leg decreased from 6,3 (mean) before surgery to 3,6 after 1 year, 4,2 was seen after 2 years and 3,4 (P< 0.0001) at the 5 years control. The Oswestry low back pain disability scale was at 52,6% (mean) before surgery. We found a significant decrease to 30,7 % after 1 year. The 2 year control showed a mean of 34,0% and the 5 year results showed the stable significant decrease of 31% ( P < 0,0001 ). The evaluation of the short-Form 36 (SF-36), showed a mean of 38,5% measured before surgery. An increase to 63,9% was seen at the 1 year control. After 2 years a decrease to 57,3% was observed. The 5 year control showed a SF-36 of 54,7%.

Conclusion: Our data give us the signal that total disc arthroplasty using the prodisc prosthesis is a good treatment option for disabling discogenic low back pain. The improvement achieved after one year could be conserved at the 2 and 5 year follow up.


P 174
Total lumbar disc replacement with a 6 degrees freedom prosthesis LPESP®: 5 years clinical experience, effects on kinematic, sagittal balance and clinical outcomes
H. Afshar1, J.Y. Lazennec2
1 Klinikum Leer, Klinik für Wirbelsäulenchirurgie, Leer
2 Universitätsklinik, Klinik für Orthopädie, Paris, Frankreich

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. The LP.ESP® disc is the first bi-composite polymeric implant achieving 6 degrees of freedom (DOF), including shock absorption and elastic return. The authors report their 5 years pioneering experience including more than 400 implantations.
Material and Methods: The LP.ESP II ® is a one piece deformable implant made of silicon gel with micro voids and surrounded by polycarbonate polyurethane securely fixed to titanium endplates. The endplates have five anchoring pinches to provide primary fixation and are covered by hydroxyapatite to provide optimal bone ingrowth. This geometry allows limited rotation and translation with elastic return. The concept is to authorize more liberty to the rotation centre and a growing resistance in each direction of solicitation to avoid hyper solicitation on posterior facet joints. The prosthesis was implanted through a anterior retroperitoneal or transperitoneal approaches for L4L5 and L5 S1 levels. Medical data and radiographs were prospectively analyzed and compared using a paired t test.

Results: Mean range of motion in flexion-extension averaged 5.0 degrees (Range 0 to 21.6°) with 4.8 degrees of standard deviation. If we consider that prosthesis with a ROM under 2° have no motion, 68 % had a motion, the mean ROM is 7.5° with 4.5 degrees of standard deviation. The mean centre of rotation was in a usual area in 87.5%. The coordinate of the MCR LP.ESP prosthesis seems similar to those of natural disc described in literature. The MCR location tends to normalize itself during the first year. On sagittal balance, pelvic tilt, sacral tilt and segmental lordosis were significantly improved with respectively 16.7±7.8, 36.5±1O.6 and 19.4±6.7 degrees preoperatively and 12.9±6.5, 40.1±9.8 and 27.8±7.8 degrees at last follow-up. Disc height was fully restored after implantation. ROM, MCR, disc height of the adjacent upper level did not change during the follow-up. No intraoperative complication occurred. There was no device related complication. Clinical scores were all significantly improved, respectively 4. 8 points for the back pain visual analogue scales (VAS), 33.8 points for the Oswestry disability index (ODI), 3.8 points for the SF36 and 17 points for the GHQ28.

Conclusion: Elastic one device prosthesis is a different concept than low friction prosthesis usually used in lumbar spine; it allows 6 degree of freedom to not constrain the instantaneous axis of rotation and reduce facet forces. Despite the limitation of our study due to the follow-up duration , it appears that LP.ESP® prosthesis is able to recreate a function to the lumbar spine similar to the healthy disc in terms quality of movement, effect on sagittal balance and absence of modification in the kinematics of the upper adjacent level.


P 176
Activ® L vs. Prodisc® L: A Comparison Study of Minimum 3-Year Follow-up
J. Feil1
1 ATOS Klinik, Zentrum für Endoprothetik, Heidelberg

Introduction: A number of LDR devices are proposed for the treatment of debilitating discogenic low-back pain. While the Charité LDR utilizes an unconstrained floating polyethylene core the semi-constrained Prodisc L allows no translation in any direction. The Activ L is designed for a controlled flexion/extension as well as translation. We retrospectively evaluated and compared radiological and clinical outcomes of LDR with Activ L and Prodisc L.

Material/Methods: From 8/2003 till 5/2009 in 148 patients 177 Prodisc L and from 5/2005 till 5/2009 in 187 patients 258 Activ L LDRs were implanted minimally invasive via transperitoneal approach by one surgeon. 141 patients were followed and enrolled in this study. There were 61 females and 80 males. Activ L was used in 73 and Prodisc L in 68 patients. 96 patients underwent single-level and in 45 patients two levels were replaced. In 88 patients MRI follow-up was performed at minimum 36-months postoperative. Facet degeneration was evaluated by Fujiwara grading system and adjacent disc degeneration by Pfirrmann classification. All patients were evaluated by standardized questionnaires (VAS, ODI) and range of motion (ROM) using standard radiographic methods.

Results: Demographics were not different among patient populations. The average ages (years) was 45.8 for Activ L and 43.4 for Prodisc L. The gender was 55% male for Activ L vs.57% for Prodisc L. There was no significant difference in mean operative time (1-level: Activ L 125 min. vs. Prodisc L 133 min.; 2-levels: Activ L 183 min. vs. Prodisc L 192 min.) or blood loss for a single (Activ L: 98 ml vs. Prodisc L 112 ml) and double level (Activ L 182 ml vs. Prodisc L 205 ml). All LDRs were performed by the same surgeon by a minimally invasive approach. The mean operative ODI and VAS score were 85.1% and 8.9 of the Activ L-group. These improved after LDR in the 3-year follow-up to 8% and 1.4. In the Prodisc L-group ODI and VAS improved from preoperative 79.2%and 8.8 to 9% and 1.9 in the 3-year follow-up. The improvement rate of ODI and VAS wee not statistically significant between the two groups (p=0.931, p=0.12). Among the 64 segments replaced with Activ L and 56 segments with Prodisc L there was no facet joint degradation in the 3-year MRI follow-up in the index level an adjacent motion segments. Degradation of adjacent disc degeneration was seen in 4 segments of the Prodisc L-group and no degradation in the Activ L-group. There was no significant difference in the mean F/E Rom at L4/5 between Activ L (6.4° preoperatively and 11.4° postoperatively) and Prodisc L (6.5 ° preoperatively and 10.7 ° degree postoperatively) with 10 mm PE inlay. Postoperative mean F/E ROM at L5/S1 of the 8,5 mm Activ L (7.6 °) was statistically significant higher than the 10 mm Prodisc L (5.5 °). Device subsidence was observed in one patient in the Activ L- as well as in the Prodisc L-group. One Prodisc L inlay dislocation required revision.

Conclusion: Clinical outcomes of both Activ L and Prodisc L are fairly good. In the minimum 3-year follow-up there was in discrepancy to the literature no significant aggravation of facet joints of the index level or adjacent motion segments. Adjacent disc degeneration was seen in 4 out of 56 Prodisc L patients. ROM increased significantly postoperatively for both groups. There was a greater increase in FE ROM at L5/S1 with the mobile 8.5 mm core Activ L compared to the 10 mm semi-constrained Prodisc L. Long-term review of dynamic radiographs as well as MRI will be needed to track motion preservation as well as facet joint and adjacent disc degeneration.




P 179
Influence of total lumbar disc replacement on intervertebral disc space height, facet joint articulation and neuroforamen and correlation of these parameters with patients subjective outcome

T. Herold1, A. Stäbler2, U. Szeimies2, C. Siepe1, J. Kneißl3 H.M. Mayer1, A. Korge1

1 Orthopädische Klinik München Harlaching, Wirbelsäulenchirurgie, München;
2 Radiologie in München Harlaching, München;
3 Qualitätsmanagement, Schön Klinik Verwaltung GmbH, Prien


Introduction: Total lumbar disc replacement (TLDR) has shown beneficial results for the treatment of lumbar discogenic low back pain in the majority of patients. However, a certain number of patients remains with unsatisfactory postoperative results. The purpose of the present study was to assess and analyse quantitative changes of disc space height (DSH), facet joint articulation and neuroforamen height after TLDR. These parameters were correlated with patients´ subjective outcome.

Material and Methods: The current study resembles a prospective CT scan analysis of 17 prostheses which were implanted in 15 patients. All prostheses were implanted either at the levels L4/5 and L5/S1. Surgery was performed between 04/05 and 03/06 using a keel- designed prosthesis (Prodisc, Synthes). Preoperative and postoperative measurements of lumbar DSH, facet joint articulation and neuroforamen height were established using a custom made computer software which was designed to determine angles and distances (medigration GmbH, the digital company, image vision, version 2.8.1). For statistical analysis the data were correlated with the prospective clinical outcome parameters Oswestry-Disability-Index (ODI). In addition two sided t-tests were conducted with respect to the subjective patient satisfaction at the 3 month FU examination.

Results: Mean anterior DSH increased from 5,9 mm to 15,8 mm and the posterior DSH from 2,7 mm to 8,9 mm. This increase resembles a difference of the intervertebral DSH of 6,2 mm and 10,0 mm (SD anterior +/- 3,0mm and SD posterior +/- 2,0mm). Overlapping of the right facet joints was reduced from 15,8 mm to10,9 mm, and the left facet joints from 15,4 mm to 10,6 mm. The delta was 4,9 mm for the right side and 4,8 mm for the left side (SD right +/- 4,3mm and SD left +/-4,0 mm). The right neuroforamen changed from 13,6 mm to 18,4 mm, and the left neuroforamen changed from 13,3 mm to 18,1 mm with an identical delta of the neuroforamen of 4,8 mm on both sides (SD right +/- 1,3 mm and SD left +/-1,2 mm). A significance difference was observed between the subjective satisfaction rate and the difference of the left neuroforamen: a smaller delta of the neuroforamen was associated with a higher patient´s satisfaction. According to the subjective satisfaction rate, no more additional differences were detected between the radiological parameters and the clinical outcome. According to the Oswestry score, results after TLDR were less satisfying in those patients with a high preoperative disc space. This could also be confirmed by the correlation between the delta of the disc space height and the Oswestry score.

Discussion: This study shows, that total lumbar disc replacement leads in the index level to an enlargement of the disc space height and the neuroforamen and to a reduction of the overlapping of the facet joints. A correlation could be shown between high preoperative DSH and rather worse subjective outcome (Oswestry score).


P 197
Biomechanical investigation of an anulus sealing device
F. Heuer1, L. Widmann1, S. Rath1, H.-J. Wilke1
1Universität Ulm, Institut für Unfallchirurgische Forschung und Biomechanik, Ulm

Introduction: The surgical standard for the treatment of herniated, displaced or ruptured intervertebral discs (IVD) is the fragmental or total removal of the nucleus tissue. This procedure is mostly performed without the reconstruction of the anular wall.

Potential risks are a reherniation or disc degeneration due to disc flattening. Only a few technical possibilities were developed to keep the remaining nucleus inside the IVD. One potential annulus closure method the Barricaid ARD (Anulus Reconstruction Device) was developed by Intrinsic Therapeutics Inc., recently. The aim of this study was to evaluate whether the ARD is able to prevent a herniation of the nucleus from inside the IVD during a cyclic loading test.

Methods: In vitro testing was performed on 12 human lumbar spinal units. The specimens were evenly distributed to form two groups. The spines were dissected into segments of L2-L3 and L4-L5. In each specimen, the posterior bony parts covering the lamina were removed. A box defect of 6 x 10 mm (height x width) was created in the posterior anulus. In the control group, the defect remained untreated, whereas the second group was treated with the ARD implant. The ARD consists of two components, a metal anchor and a mesh (figure). The anchor will be fixed to the vertebral body and the mesh blocks the annulus defect. Flexibility was assessed in a spine tester (intact, defect and implanted). Subsequently, specimens were exposed to cyclic loading using a hydraulic loading frame. Specimens were excentrally loaded in a sinus waveform with 4-24 Nm at 5 Hz while specimens rotated with 360°/min. Disc height was measured for each state. To estimate the degree of disc degeneration, intradiscal pressure measurements were taken in the intact situation.

Results: Generally, the posterior defect reduced disc heights. Implantation could almost compensate this loss. Comparing both groups the cyclic loading decreased the disc heights. The control group resulted in a higher disc height decrease as compared to the implanted group. The defect also caused an increase of the flexibility, being similar for both groups. Implantation of the ARD showed a trend to reduce the range of motion (RoM). Although, it was not capable to restore these values back to the intact condition. A nucleus herniation was observed in a specimen belonging to the control group that had the highest intradiscal pressure. However, we could not see an extrusion for the implanted group.

Discussion: The defect scenario did not produce a nucleus extrusion in each specimen of the control group, as expected. Horizontal cuts of the IVDs after testing showed that most specimens had already a fibrous nucleus. This may have been the reason for the low nucleus extrusion rate. Furthermore, these specimens also yielded a lower intradiscal pressure compared to the extruded specimen. No extrusion was produced in the implanted group. However, it cannot be guaranteed that the implant always avoids a herniation concerning the used specimens. A further study is planned with the aim of producing a nucleus herniation on specimens that are less degenerated. After the extrusion the ARD will be implanted. Subsequently, specimens will be exposed to cyclic loading. This should better allow estimating the reherniation risk of the implant.

Acknowledgement: This study was supported by Intrinsic Therapeutics Inc.


P 207
The biomechanical performance of a silicon gel implant introduced by a transsacral approach
H.-J. Wilke1, P. Zelenkov1, K. Werner1
1Universität Ulm, Institut für Unfallchirurgische Forschung und
Biomechanik, Ulm

Introduction: Replacement of the nucleus with an implant often requires a large defect in the annulus, which can increase both the flexibility of a spinal segment and the extrusion risk for the implant. Implantation through a transsacral approach may preserve biomechanical important anatomical structures and prevent extrusion of the implant. The purpose of this study was to investigate the biomechanical behavior of the transsacral in situ formed silicone nucleus replacement device (PNRTM), which may be implanted even after a conventional microdiscectomy has been performed (figure).

Methods: Six fresh frozen human lumbar spine specimens (L2-S1) were split in two groups: monosegmental L2-3 segments and bisegmental L4-S1 specimens. In the monosegmental group, microdiscectomy was carried out through interlaminar approach to represent a worst case scenario. Transsacral nucleus replacement with an in situ formed silicone implant was performed in the bisegmental group into the segment L5-S1. Both groups were exposed to cyclic loading (100-600 N) for 100,000 cycles. Segment flexibility was tested in the intact state, after microdiscectomy, transsacral nucleoectomy, implantation and 100,000 cycles of loading under pure bending moments (7.5 Nm) in the three main motion plane. After testing, all specimens were dissected and underwent macroscopic investigation.

Results: Nucleotomy, either transsacral alone or transsacral combined with a conventional microdiscectomy increased the range of motion by 20% in flexion/extension and lateral bending, and 15% in axial rotation. A transsacral nucleus replacement (PNRTM) implant provided a restoration of the biomechanical behavior of the intact segment. In treated and non-treated segments, there was a decrease in stiffness due to cyclic loading. No expulsion of the implant could be observed, even with a posterior defect in the annulus fibrosus. Macroscopic inspection revealed no visible endplate damage or implant migration.

Discussion: Transsacral nucleus replacement with PNRTM implant provided a restoration of the biomechanical behavior of the intact segment. The PNRTM seems to be an interesting alternative with low risk of extrusion.


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