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 Several others under IDE 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