Update on Cervical Disc Arthroplasty

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Update on Cervical Disc Arthroplasty

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

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

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• Becoming a billion dollar business

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• 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

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Background

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

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Current CDR

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

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All IDE Studies

• Controls Allograft and plate
• 2 year FU
• Radiculopathy or myelopathy from single-level
  disease
• Exclusion criteria
• Marked spondylosis/Facet joint arthrosis
• lt2 º motion at index segment
• gt50 disc space collapse
• Segmental instability (gt3 mm translation)
• Cervical kyphosis

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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

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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

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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

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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

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Bryan IDE

• Lower neck pain score for CDR at all time points

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Bryan IDE

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

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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

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Bryan IDE

• 2 other studies on Bryan CDR neither with control
  group

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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

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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

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IDE Pro-Disc C

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

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Conflict of Interest
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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

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Adjacent to Fusion

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

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ROM

• Preserving ROM ? adjacent IDP/facet forces?
• 3 IDE studies with ? 7º ROM at treated segment
• ? 15 of patients with ? ROM or ankylosis

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Adjacent Level Disease

• Prevention of ALD is main focus of CDR

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Adjacent Level Disease

• 2.9/yr symptomatic adjacent level disease

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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

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Adjacent Level Disease

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

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Long Term Results

• Potential 7 yr FU of first RCT CDR not reported

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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

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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

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Conclusion

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