lessons learned after nine-year follow-up on eight different lumbar total disc replacement devices

2
establish range of motion (ROM) values for each tested construct on a 6 de- gree of freedom spine motion simulator. Data was normalized to intact (Intact5100%) and analyzed. Significance was set at p ! 0.05. RESULTS: All the surgical constructs offered significant stability in all loading conditions compared to the intact condition. Mean ROM of differ- ent constructs trended as follows: DDS O DIS O SSS O MGT. Overall, the DDS construct provided 55%, 43%, and 60% additional stability, com- pared to SSS, DIS, and MGT, respectively. This was significant in flexion- extension compared to SSS and MGT. In lateral bending, no significant differences among the instrumented constructs were found. In axial rota- tion, DDS was found to be significantly stable compared to MGT. CONCLUSIONS: In the setting of total sacrectomy, double-rod double il- iac screw method provided the most rigid fixation, followed by double iliac screw fixation, single-rod single screw, and modified Galveston technique. In cases precluding double-rod double iliac screw, double iliac screw fix- ation method may provide enough stability while minimizing rod contour- ing and surgical incision. In spino-pelvic reconstruction, use of double iliac screws is recommended over single illiac screw fixation techniques when treating more unstable situations caused by total sacrectomy. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2012.08.096 56. The CoflexÒ Versus Fusion US FDA IDE Trial: An In Vivo Biomechanical Study of Adjacent Segment Motion Following Fusion William R. Sears, MD, FRACS 1 , Reginald J. Davis, MD, FACS 2 , Joshua D. Auerbach, MD 3 ; 1 Sydney, Australia; 2 Greater Baltimore Neurosurgical Associates, Baltimore, MD, US; 3 Brooklyn, NY, US BACKGROUND CONTEXT: Numerous in vitro biomechanical studies have reported increased motion and stresses at segments adjacent to a sim- ulated lumbar spinal fusion. However, some authors have questioned the methodology & hence, the findings of these cadaveric studies. Questions remain regarding the optimal methodology to replicate in vivo conditions; in particular, should in vitro models use displacement, load or hybrid con- trol? The recent FDA trial, which examined the CoflexÒ interlaminar de- vice, included an examination of overall lumbar spinal and segmental motion using digital quantitative motion analysis (QMAÔ). QMAÔ has been found to be accurate to within 0.5-1 . PURPOSE: To prospectively examine in vivo lumbar segmental motion before and after fusion to help resolve questions regarding: firstly, the af- fects of fusion on adjacent segment motion and secondly, the optimization of in vitro test methodology. STUDY DESIGN/SETTING: In vivo biomechanical study of patients participating in a multicenter, prospective, randomized FDA IDE trial. PATIENT SAMPLE: One hundred ninety patients randomized 2:1 to the investigational (decompression þ CoflexÒ interlaminar device) or control (decompression þ instrumented, posterolateral fusion) arms. Inclusion cri- teria: back pain (VAS O50) with neurogenic claudication. ODI O 40. Mod- erate or severe canal stenosis and up to Grade 1 degenerative spondylolisthesis. Mean age: 62.5 years 69(StDev). OUTCOME MEASURES: Individual lumbar segmental and overall (L1-S1) range-of-motion (ROM) in degrees. METHODS: Dynamic x-rays were examined pre-operatively and at regu- lar time-intervals for a minimum 24-months using QMAÔ. Total lumbar (L1-S1) range-of-motion (ROM ), motion at the index level(s) and motion at one level above, two levels above and one level below are reported in this study. Non-parametric statistics were used with significance set at p !0.05. Results are shown as means (6 Standard Deviation). RESULTS: In the 45 patients who underwent 1-level and 24 patients who underwent 2-level fusions, a trend toward increased ROM was evident at the segments immediately above the fused segments at 12-months: pre- operative ROM measured 3.4 (63.3 ) and 3.8 (62.8 ) in the 1- and 2- level fusions, respectively and measured 4.6 (64.6 , p50.08) and 5.2 (64.3 ,p50.18) at 12-months. By 24-months, ROM at these segments had increased further & significantly to: 4.9 (64.5 ,p50.035) above 1- level and 7.6 (64.8 ,p50.0005) above 2-level fusions. The mean increase in ROM above 2-level fusions at 24-months was 3.7 (95%CI:1.8 -5.6 ). A small but apparently significant increase in ROM was seen at 24-months at the level immediately below 1-level fusions (1.6 ,p50.02). Otherwise, no significant changes in ROM were observed at segments two-levels above or one-level below the fusions. In the 1-level fusion patients, ROM at the fused levels decreased by 2.8 at both 12- and 24-months. In the 2-level fusion patients, mean ROM at the fused segments reduced by 4.0 and 3.6 at 12 & 24-months, respectively (p !0.0001). Despite the reduction in mo- tion at the fused segments, total (L1-S1) ROM did not change over the pre-, 12- and 24-month time-points: 20.4 (613.1 ), 19.8 (613.2 , p50.62), 22.2 (613.3 ,p50.33), respectively. No significant changes were observed in any motion parameters in patients implanted with the CoflexÒ device. CONCLUSIONS: The current in vivo study has shown a trend, both over time and with more fused levels, towards increasing ROM at levels imme- diately above a spinal fusion – most apparent at 24-months, above 2-level fusions, where a two-fold increase in mean ROM was evident. While inter- and intra-patient variations were observed, likely related to factors such as patient effort or pain, analysis of mean values over 12 & 24-months showed no significant change in L1-S1 ROM, despite significant reduc- tions in motion associated with fused segments. This would appear to in- dicate that the presence of a fusion does not naturally lead to a reduction in patients’ subsequent L1-S1 ROM and that displacement or hybrid control in vitro methodology may be appropriate. Examination of x-rays at additional postoperative time points may confirm the apparent trend to- wards increasing motion, evident at segments above fusions, over time. If so, this finding may also require attention in in vitro experimental methodology. FDA DEVICE/DRUG STATUS: CoflexÒ (Investigational/Not approved) http://dx.doi.org/10.1016/j.spinee.2012.08.097 57. Lessons Learned After Nine-Year Follow-Up on Eight Different Lumbar Total Disc Replacement Devices Luiz H. Pimenta, MD, PhD, Luis Marchi, MD, Leonardo Oliveira, MD; S~ ao Paulo, Brazil BACKGROUND CONTEXT: Charit e prothesis has over than 20.000 pa- tients worldwide and has been implanted since the early 1980’s. Over these years, new prostheses have been developed, differing in disc materials, bio- mechanical features, indications and implantation approaches. Nowadays we can be supported by literature and clinical experience. PURPOSE: Here we show our experience in 8 different lumbar TDR de- vices up to 9 years follow up STUDY DESIGN/SETTING: The senior author’s wide clinical experi- ence was analyzed. PATIENT SAMPLE: More than 400 single or multi-level implanted pros- theses with up to 9 years of follow-up. OUTCOME MEASURES: We have evaluated the pitfalls in the lumbar arthroplasty history and how is possible to minimize this problems. METHODS: The clinical experience lay on different prostheses, including charit e, prodisc, mobidisc, triumph, maverick, physio-L, active-L and lat- eral disc. Patients had been prospectively monitored, using the clinical and imagining outcomes assessment. Complications and success have been recorded and related to pre-existing conditions, prostheses design, ap- proaches and indications. RESULTS: Overall clinical outcomes testify TDR benefits, but point out to long term complications appearance. Complications type depends on the prosthesis model, covering facet join pain, subsidence, bad positioning, core fracture, pedicle fracture, iatrogenic scoliosis, heterotopic ossification and CrCo allergy. Persistent back pain-9.1%; facet degeneration - 25%; 29S Proceedings of the NASS 27th Annual Meeting / The Spine Journal 12 (2012) 22S–44S All referenced figures and tables will be available at the Annual Meeting and will be included with the post-meeting online content.

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Page 1: Lessons Learned After Nine-Year Follow-Up on Eight Different Lumbar Total Disc Replacement Devices

29SProceedings of the NASS 27th Annual Meeting / The Spine Journal 12 (2012) 22S–44S

establish range of motion (ROM) values for each tested construct on a 6 de-

gree of freedom spine motion simulator. Data was normalized to intact

(Intact5100%) and analyzed. Significance was set at p!0.05.

RESULTS: All the surgical constructs offered significant stability in all

loading conditions compared to the intact condition. Mean ROM of differ-

ent constructs trended as follows: DDSODISO SSSOMGT. Overall, the

DDS construct provided 55%, 43%, and 60% additional stability, com-

pared to SSS, DIS, and MGT, respectively. This was significant in flexion-

extension compared to SSS and MGT. In lateral bending, no significant

differences among the instrumented constructs were found. In axial rota-

tion, DDS was found to be significantly stable compared to MGT.

CONCLUSIONS: In the setting of total sacrectomy, double-rod double il-

iac screw method provided the most rigid fixation, followed by double iliac

screw fixation, single-rod single screw, and modified Galveston technique.

In cases precluding double-rod double iliac screw, double iliac screw fix-

ation method may provide enough stability while minimizing rod contour-

ing and surgical incision. In spino-pelvic reconstruction, use of double iliac

screws is recommended over single illiac screw fixation techniques when

treating more unstable situations caused by total sacrectomy.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

http://dx.doi.org/10.1016/j.spinee.2012.08.096

56. The Coflex� Versus Fusion US FDA IDE Trial: An In Vivo

Biomechanical Study of Adjacent Segment Motion Following Fusion

William R. Sears, MD, FRACS1, Reginald J. Davis, MD, FACS2, Joshua

D. Auerbach, MD3; 1Sydney, Australia; 2Greater Baltimore Neurosurgical

Associates, Baltimore, MD, US; 3Brooklyn, NY, US

BACKGROUND CONTEXT: Numerous in vitro biomechanical studies

have reported increased motion and stresses at segments adjacent to a sim-

ulated lumbar spinal fusion. However, some authors have questioned the

methodology & hence, the findings of these cadaveric studies. Questions

remain regarding the optimal methodology to replicate in vivo conditions;

in particular, should in vitro models use displacement, load or hybrid con-

trol? The recent FDA trial, which examined the Coflex� interlaminar de-

vice, included an examination of overall lumbar spinal and segmental

motion using digital quantitative motion analysis (QMA�). QMA� has

been found to be accurate to within 0.5-1�.PURPOSE: To prospectively examine in vivo lumbar segmental motion

before and after fusion to help resolve questions regarding: firstly, the af-

fects of fusion on adjacent segment motion and secondly, the optimization

of in vitro test methodology.

STUDY DESIGN/SETTING: In vivo biomechanical study of patients

participating in a multicenter, prospective, randomized FDA IDE trial.

PATIENT SAMPLE: One hundred ninety patients randomized 2:1 to the

investigational (decompression þ Coflex� interlaminar device) or control

(decompression þ instrumented, posterolateral fusion) arms. Inclusion cri-

teria: back pain (VASO50) with neurogenic claudication. ODIO40. Mod-

erate or severe canal stenosis and up to Grade 1 degenerative

spondylolisthesis. Mean age: 62.5 years 69(StDev).

OUTCOME MEASURES: Individual lumbar segmental and overall

(L1-S1) range-of-motion (ROM) in degrees.

METHODS: Dynamic x-rays were examined pre-operatively and at regu-

lar time-intervals for a minimum 24-months using QMA�. Total lumbar

(L1-S1) range-of-motion (ROM�), motion at the index level(s) and motion

at one level above, two levels above and one level below are reported in

this study. Non-parametric statistics were used with significance set at

p!0.05. Results are shown as means (6 Standard Deviation).

RESULTS: In the 45 patients who underwent 1-level and 24 patients who

underwent 2-level fusions, a trend toward increased ROM was evident at

the segments immediately above the fused segments at 12-months: pre-

operative ROM measured 3.4�(63.3�) and 3.8�(62.8�) in the 1- and 2-

level fusions, respectively and measured 4.6�(64.6�, p50.08) and

All referenced figures and tables will be available at the Annual Mee

5.2�(64.3�, p50.18) at 12-months. By 24-months, ROM at these segments

had increased further & significantly to: 4.9�(64.5�, p50.035) above 1-

level and 7.6�(64.8�, p50.0005) above 2-level fusions. The mean increase

in ROM above 2-level fusions at 24-months was 3.7�(95%CI:1.8�-5.6�). Asmall but apparently significant increase in ROM was seen at 24-months at

the level immediately below 1-level fusions (1.6�, p50.02). Otherwise, no

significant changes in ROM were observed at segments two-levels above

or one-level below the fusions. In the 1-level fusion patients, ROM at

the fused levels decreased by 2.8� at both 12- and 24-months. In the 2-level

fusion patients, mean ROM at the fused segments reduced by 4.0� and 3.6�

at 12 & 24-months, respectively (p!0.0001). Despite the reduction in mo-

tion at the fused segments, total (L1-S1) ROM did not change over the

pre-, 12- and 24-month time-points: 20.4�(613.1�), 19.8�(613.2�,p50.62), 22.2�(613.3�, p50.33), respectively. No significant changes

were observed in any motion parameters in patients implanted with the

Coflex� device.

CONCLUSIONS: The current in vivo study has shown a trend, both over

time and with more fused levels, towards increasing ROM at levels imme-

diately above a spinal fusion – most apparent at 24-months, above 2-level

fusions, where a two-fold increase in mean ROM was evident. While inter-

and intra-patient variations were observed, likely related to factors such as

patient effort or pain, analysis of mean values over 12 & 24-months

showed no significant change in L1-S1 ROM, despite significant reduc-

tions in motion associated with fused segments. This would appear to in-

dicate that the presence of a fusion does not naturally lead to a reduction

in patients’ subsequent L1-S1 ROM and that displacement or hybrid

control in vitro methodology may be appropriate. Examination of x-rays

at additional postoperative time points may confirm the apparent trend to-

wards increasing motion, evident at segments above fusions, over time. If

so, this finding may also require attention in in vitro experimental

methodology.

FDA DEVICE/DRUG STATUS: Coflex� (Investigational/Not approved)

http://dx.doi.org/10.1016/j.spinee.2012.08.097

57. Lessons Learned After Nine-Year Follow-Up on Eight Different

Lumbar Total Disc Replacement Devices

Luiz H. Pimenta, MD, PhD, Luis Marchi, MD, Leonardo Oliveira, MD;

S~ao Paulo, Brazil

BACKGROUND CONTEXT: Charit�e prothesis has over than 20.000 pa-

tients worldwide and has been implanted since the early 1980’s. Over these

years, new prostheses have been developed, differing in disc materials, bio-

mechanical features, indications and implantation approaches. Nowadays

we can be supported by literature and clinical experience.

PURPOSE: Here we show our experience in 8 different lumbar TDR de-

vices up to 9 years follow up

STUDY DESIGN/SETTING: The senior author’s wide clinical experi-

ence was analyzed.

PATIENT SAMPLE:More than 400 single or multi-level implanted pros-

theses with up to 9 years of follow-up.

OUTCOME MEASURES: We have evaluated the pitfalls in the lumbar

arthroplasty history and how is possible to minimize this problems.

METHODS: The clinical experience lay on different prostheses, including

charit�e, prodisc, mobidisc, triumph, maverick, physio-L, active-L and lat-

eral disc. Patients had been prospectively monitored, using the clinical and

imagining outcomes assessment. Complications and success have been

recorded and related to pre-existing conditions, prostheses design, ap-

proaches and indications.

RESULTS: Overall clinical outcomes testify TDR benefits, but point out

to long term complications appearance. Complications type depends on the

prosthesis model, covering facet join pain, subsidence, bad positioning,

core fracture, pedicle fracture, iatrogenic scoliosis, heterotopic ossification

and CrCo allergy. Persistent back pain-9.1%; facet degeneration - 25%;

ting and will be included with the post-meeting online content.

Page 2: Lessons Learned After Nine-Year Follow-Up on Eight Different Lumbar Total Disc Replacement Devices

30S Proceedings of the NASS 27th Annual Meeting / The Spine Journal 12 (2012) 22S–44S

misplacements-8.5%; subsidence-7%; partial explantations-2%; bone frac-

tures-2% and retrievals-6.21%.

CONCLUSIONS: Our analyses can point out various lumbar arthroplasty

aspects, including its pros: better biomechanical results, better clinical re-

sults, restoration of global motion, no bone graft needed; and its cons: ex-

pensive technology, short follow up in comparison to fusion, important

adverse events, ideal prosthesis yet nonexistent. Constant patient monitor-

ing, data sharing, concept and technology adapting are essential for

achieve crescent success.

FDA DEVICE/DRUG STATUS: Charit�e (Investigational/Not approved),

XLTDR (Investigational/Not approved), Triumph (Investigational/Not ap-

proved), Phisio-L (Investigational/Not approved), Maverick (Investiga-

tional/Not approved), Prodisc (Investigational/Not approved), Mobidisc

(Investigational/Not approved), Active-L (Investigational/Not approved)

http://dx.doi.org/10.1016/j.spinee.2012.08.098

58. Five-Year Adjacent Level Degenerative Changes Comparing

Lumbar Total Disc Replacement to Circumferential Fusion in

Patients with Single-Level Disease in a Prospective Randomized

Cohort Analysis

Jack E. Zigler, MD1, Rick B. Delamarter, MD2; 1Texas Back Institute,

Plano, TX, US; 2Los Angeles, CA, US

BACKGROUND CONTEXT: Acceleration of degeneration at the seg-

ment adjacent to a spinal fusion is a concern. It was proposed that one po-

tential advantage of total disc replacement (TDR) for the treatment of

painful disc degeneration may be to reduce the occurrence of adjacent seg-

ment deterioration.

PURPOSE: The authors report the five year results of radiographic adja-

cent level degenerative changes seen in patients enrolled in a prospective

multicenter study in which they were randomized to either TDR or circum-

ferential fusion for single-level lumbar degenerative disc disease.

STUDY DESIGN/SETTING: Data were collected prospectively as part

of a multicenter FDA IDE trial.

PATIENT SAMPLE: Two hundred thirty six patients with single-level

lumbar degenerative disc disease were enrolled and randomly assigned

to two treatment groups: 161 in the total disc replacement (TDR) group

treated with the ProDisc-L (Synthes Spine) and 75 treated with circumfer-

ential fusion. Complete radiographic follow-up at 5 years was available for

123 TDR patients and 43 fusion patients.

OUTCOMEMEASURES: Theprimaryoutcomemeasurewas radiographic

assessment of adjacent level degeneration assessed by radiologists at an inde-

pendent facility. Range of motion (ROM) and translation were also evaluated.

METHODS: ALDwas characterizedbya composite score comprisedof disc

height loss, endplate sclerosis, osteophytes and spondylolisthesis. At 5 years,

changes in ALD (DALD) were compared to the pre-operative assessment.

RESULTS: At five years, no change in adjacent level degeneration was

observed in 90.8% of the TDR patients compared to 71.4% of the Fusion

patients (p50.004). For patients with no adjacent level disease pre-opera-

tively, new findings of ALD at five years were found in 6.7% of the TDR

patients and in 23.8% of the Fusion patients. Adjacent level surgery lead-

ing to secondary surgery was reported for 2.9% of the TDR patients and

4.0% of the Fusion patients (p50.6819). TDR patients had a mean pre-

operative, index level range of motion (ROM) of 7.2� that was maintained

at 5 years. Neither treatment group had significant changes at 5 years in

either ROM or translation at the superior level.

CONCLUSIONS: At five years following index surgery, TDR maintained

ROM and was associated with a significantly higher rate of no DALD com-

pared to results in prospectively randomized patients treated with circum-

ferential fusion. Fusion patients had a 4.5 times higher rate of DALD

compared to TDR patients. Even in the follow-up window of five years,

there is a significant radiographic protective effect of TDR on the adjacent

lumbar segment, particularly in patients with no adjacent level disease at

the time of the index surgery. It is anticipated that, over time, this may

be reflected in a lower rate of secondary surgery.

All referenced figures and tables will be available at the Annual Mee

FDA DEVICE/DRUG STATUS: ProDisc-L (Approved for this

indication)

http://dx.doi.org/10.1016/j.spinee.2012.08.099

59. New Strategy for Treatment of Lower Back Pain: Molecular

Restoration of Intervertebral Disc Using an Injection of Biomimetic

Aggrecan

Katsiaryna Prudnikova, PhD1, Edward J. Vresilovic, MD, PhD2,

Michele Marcolongo1; 1Drexel University, Philadelphia, PA, US;2Ardmore, PA, US

BACKGROUND CONTEXT: Early degeneration of the intervertebral

disc is accompanied by a decrease in aggrecan content in the nucleus pulpo-

sus. Aggrecan is composed of negatively charged chondroitin sulfate (CS)

bristles attached to a protein core. During degeneration, aggrecan is cleaved

along the protein backbone by enzymes, reducing the aggrecan content in the

nucleus and leading to a loss of hydration and disc height as well as mechan-

ical instability. We hypothesize that restoration of aggrecan to normal levels

will restore disc function, however, injection with natural aggrecan is

cost prohibitive and natural aggrecan would still be subject to enzymatic

degradation.

PURPOSE: We have synthesized a low-cost, enzymatically resistant bio-

mimetic analogue to natural aggrecan which can easily be injected into the

nucleus pulposus to molecularly engineer the matrix to restore the osmotic

pressure of the disc.

METHODS: Biomimetic aggrecan was synthesized by grafting CS bris-

tles to poly(acrylic acid) (PAA) (250 kDa MW) and poly(acryloyl chlo-

ride) (PAC) (10 kDa MW) cores (enzymatically resistant backbones).

Reaction was performed at different ratios (mol/mol) of CS molecules to

functional groups 1:10 (PAC-CS), 1:15 and 1:30 (PAA-CS). Reaction ki-

netics were monitored using a fluorescamine assay. Macromolecules were

purified and chemical structures were confirmed with 1H NMR. Biomi-

metic aggrecan was chjaracterized via rheometry and osmotic pressure.

Initial cytocompatibility of biomimetic aggrecan samples was assessed us-

ing L9292 fibroblasts.

RESULTS: Natural aggrecan has about 100 CS bristles, spaced 3-5 nm

apart along the length of the core with an overall molecular weight of

~2,000 kDa. The synthesized biomimetic aggrecan was shown to have

~85 CS bristles on the 250 kDa PAA core with bristles spaced at 4-8 nm

and a total estimated molecular weight of ~2,000 kDa. 1H NMR spectra

showed no degradation of CS with processing. Remarkably, an 8X increase

in osmotic pressure from CS alone and equal osmotic pressure to natural ag-

grecan was measured for our biomimetic analogue. The shorter 10 kDa

PAA results scaled to the length of the core. Biomimetic aggrecan was

cytocompatible.

CONCLUSIONS: Novel biomimetic aggrecan, which mimics the 3-D ar-

chitecture and osmotic properties of the natural aggrecan, was shown to

have comparable osmotic pressure of natural aggrecan and to be cytocom-

patible. Biomimetic aggrecan can be used as a low-cost augmentation to

molecularly engineer the nucleus pulposus matrix for mechanical stabiliza-

tion of the disc.

FDA DEVICE/DRUG STATUS: This abstract does not discuss or include

any applicable devices or drugs.

http://dx.doi.org/10.1016/j.spinee.2012.08.100

60. Biomechanical and Early Clinical Results of Stand-Alone

Anterior Cervical Fixation for Rotationally Unstable Facet

Fractures

Christopher D. Chaput, MD1, David M. Gloystein, MD2, Mark Rahm,

MD3, Aditya M. Muzumdar4, Mark Moldavsky5, Suresh Chinthakunta4,

Saif Khalil, PhD4; 1Scott & White Hospital, Temple, TX, US; 2Fort Hood

Orthopaedics, Harker Heights, TX, US; 3Texas A & M Scott & White

ting and will be included with the post-meeting online content.