Update on Cervical Disc Arthroplasty

Brian Su, MD John Ratliff, MD Associate Professor Departments of Neurosurgery and Orthopedic Spine Surgery Thomas Jefferson University

 Almost all published after 2001  34 in last year (2 prospective RCT)

 Becoming a billion dollar business

 CDR mandates a critical look  Background  Analysis of IDE studies of FDA cleared CDR  Bottom line results  How they compare to previous studies  CDR for myelopathy  Adjacent level disease and longest available follow up  CPT coding changes

Background

 First clinical report of CDR  Bristol-Cummins  22 implanted for myelopathy in endstage cervical disease  Evolved into Prestige I, II, and ST (Medtronic)

Current CDR

 As of 7/2009 FDA approved CDR  Prestige ST (Medtronic)  Bryan (Medtronic)  ProDisc-C (Synthes)  Several others under IDE

All IDE Studies

 Controls: Allograft and plate  2 year FU  Radiculopathy or myelopathy from single level disease  Exclusion criteria  Marked spondylosis/Facet joint arthrosis  <2 º motion at index segment  >50% disc space collapse  Segmental instability (>3 mm translation)  Cervical kyphosis

Prestige ST IDE

 Prestige ST stainless steel metal on metal ball and trough articulation  CDR (276 pts) vs. ACDF (265 pts) for single level disease

Prestige ST IDE

 NDI better in CDR group up to 3 mo only  Collar use?

 No difference in SF 36, neck or arm pain, or return to work status  In 2007 became first CDR FDA approved

Prestige ST IDE

 Only one other clinical study  First RCT of CDR  CDR (27 pts) vs ACDF (28 pts)  2 yr FU; no difference between groups

Bryan IDE

 Polyurethane nucleus between titanium shell  CDR (242 pts) vs. ACDF (221 pts)  Better SF-36 score and arm pain relief at 1 yr for CDR not significant at 2 yrs

Bryan IDE

 Lower neck pain score for CDR at all time points

Bryan IDE

 Lower NDI score for CDR at all time points  Difference may not be clinically significant

Bryan IDE

 Earlier return to work at 1.5 and 3 months in CDR group but not at 2 yrs  RTW 13 days sooner in CDR group

Bryan IDE

 2 other studies on Bryan CDR neither with control group

ProDisc-C IDE

 Metal on UHMWPE with CoCrMo alloy and midline keel  CDR (103 pts) vs. ACDF (106 pts)  No differences in any clinical outcome measures at 1 or 2 yrs

IDE ProDisc-C

 Significant differences at 2 yrs in favor of CDR  Secondary surgeries  9% ACDF vs 2% CDR  More patients on narcotics  19% ACDF vs 10% CDR  Unblinded surgeon discretion used to prescribe further treatments

IDE Pro-Disc C

 2 other studies on Pro-Disc C  Bertagnoli et al (no control group)  Nabhan et al prospective RCT vs ACDF

Conflict of Interest

Adjacent to Fusion

 PCM Disc: Unconstrained CoCr and UHMWPE press fit  Adjacent to prior fusion (26 pts) vs. primary CDR (126 pts)  Part of IDE study even though no ACDF control group

Adjacent to Fusion

 No differences in improvement in NDI and VAS scores between two groups

ROM

  Preserving ROM ↓ adjacent IDP/facet forces?

3 IDE studies with  7º ROM at treated segment   15% of patients with ↓ ROM or ankylosis

Adjacent Level Disease

 Prevention of ALD is main focus of CDR  Hilibrand et al repeatedly referenced in CDR papers regarding adjacent level disease

Adjacent Level Disease

 2.9%/yr symptomatic adjacent level disease  In agreement with progression in non-fusion procedures (

Henderson 1983 Neurosurgery

)

Adjacent Level Disease

 Only 1 clinical study on ALD in CDR vs fusion  Bryan vs. Affinity cage  2 yr FU  Patients from separate RCT trials  Cohort of patients 6 yrs apart

Adjacent Level Disease

 7% symptomatic in fusion group vs 0% in CDR  Radiographs not blinded  Posterior osteophytes not included  Not CDR vs ACDF

Long Term Results

 Potential

7 yr FU

of first RCT CDR not reported

Future Problems

 MRI imaging may be impossible in some devices  Sekhon, Duggal, et al. Spine 32: 2007  Non-titanium devices make MRI imaging impossible due to artifact  PCM, Prodisc C  Could not visualize either the operated upon nor adjacent levels  With titanium devices, imaging was feasible

Summary

 3 CDR currently approved  Know indications/exclusion criteria  IDE studies show early benefit but for the most part equivalent to ACDF  Bryan CDR less neck pain and NDI at 2 yrs   CDR ok for myelopathy and adjacent to fusion Benefits in ↓ ALD promising  No published reports longer than 2 yr FU

Conclusion

  Natural history is unclear Adjacent segment disease important  Arthroplasty rapidly evolving  Long term impact of cervical arthroplasty remains unclear