Introduction to Spine Arthroplasty

Ira Fedder, MD Scoliosis and Spine Center Towson, MD DePuy Spine confidential information. Do not duplicate. Do not distribute.

Spine Surgery at the Millennium   Posterolateral +/- Instrumentation Circumferential (“360°”)  PLIF (Posterior Lumbar Interbody Fusion)   ALIF (Anterior Lumbar Interbody Fusion) TLIF (Transforaminal Lumbar Interbody Fusion)

Paradox Can the same problem (discogenic pain) be treated effectively using interventions with the exact opposite technical goals?

Biomechanics 80% Anterior 20% Posterior The 80-20 rule of Spine loading

History of Lumbar TDR

Fernström – 1960’s

History of Lumbar TDR

Synthes ™

PRODISC ® I - 1987 PRODISC ® II - 1999

History of Lumbar TDR

Medtronic

™ Maverick ™ - 2001

History Karin Büttner-Janz

INVENTOR

DePuy Spine confidential information. Do not duplicate. Do not distribute.

History of Lumbar TDR

SB CHARITÉ ™

I - 1984 II - 1985 III - 1987

History Design Iterations Experimental Prototypes Never Commercially Available    Büttner-Janz SB Charité     ™ I 1984 13 patients, 14 Implants SB Charité ™ II 1985 36 patients, 44 Implants   Non-forged stainless steel No special instrumentation Data from The Artificial Disc, Buttner-Janz, 2003

History - Current Design CHARITÉ Artificial Disc   Refined design by Waldemar Link    Cast Cobalt Chrome Endplates Ultra High Molecular Weight Polyethylene (UHMWPE) Sliding Core Design unchanged since 1987 First released 1987   Thousands of implantations worldwide Same design used in U.S. IDE clinical study  17-year track record

Importance of Sizing

Proper Endplate Size Bone Density

Dr. Wolfgang Raushning - Uppsala University, Sweden 2000

David, TJ.

“Lumbar Disc Prosthesis: Five Years Follow-up Study on 147 Patients with 163 SB Charité Prosthesis.” EuroSpine 2003 Results related to surgeon experience  1989 - 1991  43 patients: 63% excellent/good   1992 - 1994  57 patients: 82% excellent/good 1995 - 1997  44 patients: 93% excellent/good

European Experience: Lessons Learned  Sizing  Positioning  Patient selection  Controlled distraction

Learning Objectives    Patient Selection Patient Selection Patient Selection

Radiographic Evaluation We ARE treating discogenic pain with TDR  Biggest challenge is to identify the pain generator  Start with plain x-rays, MRI  Studies have shown high false positive rate of MRIs  Discography can help distinguish between asymptomatic “dark discs” on MRI and those that are pain generators

Discography    Clinical pain provocation test Radiographic images Test is positive only if:   The disc is abnormal in appearance AND Patient’s clinical pain is provoked during injection

Clinical Indications    Chronic low back pain +/- leg pain  Persisting > 6 months  Associated with degenerative disc changes Leg pain   Radicular Pseudoradicular Foraminal stenosis  Secondary to disc space height loss  may be relieved indirectly by disc height restoration

Contraindications Osteoporosis or Osteopenia   Dexa-scan patients > age 50 or with more than 1 risk factor T< -1.0 is contraindicated

Contraindications Scoliosis >11º sagital deformity

Contraindications Instability including  isthmic spondylolysis  spondylolisthesis  retro or anteriolisthesis > 3mm

Contraindications Poor psychometric evaluation      Abnormal pain discogram Hz of Schizophrenia Bi-polar condition Severe depression Inability to comprehend procedure and risks

Facet Disease Mild Moderate Severe Contraindication:  Advanced Facet Disease   Severe Spinal Stenosis (canal space < 8mm) Use CT Myelogram to evaluate

Contraindications        Central Stenosis Tumor Arachnoiditis History of chronic steroid use Advanced facet disease Facet joint ankylosis Metal allergies      Pregnancy Single or bilateral leg pain (due to nerve compression) Non-contained herniated nucleus pulposus Infection/neoplasm Autoimmune disorders

Approach Related Contraindications  Anterior Vascular Calcification  Previous major vessel surgery  Obesity: BMI > 40 or 100lbs over ideal body weight  Previous retroperitoneal procedures

Effectiveness Results (All Randomized) Primary Hypothesis: Overall Success Rate Conclusion : The CHARITÉ Artificial Disc is at least equivalent in overall success to the BAK cage in treatment of DDD at one level (L4-S1).

Overall Success CHARITÉ BAK Cage Blackwelder’s Test P-Value*

N (completers) Yes 184 107 (58%) 81 44 (54%)

<.0173

No 77 (42%) 37 (46%) *Blackwelder’s test: delta=.10 Ho:Pbak = PBsb + delta, Ha:PBAK <= Psb + delta  Small P-value indicates high degree of certainty

Effectiveness Results (All Randomized) Primary Effectiveness Endpoints

Characteristic

N (completers) 15pt improvement in Oswestry Yes No Device failures* Success Failure Major complications** Success Failure Neurological deterioration Success Failure Overall Success Rate

CHARITÉ

184 117 (64%) 67 (36%) 175 (95%) 9 (5%) 182 (99%) 2 (1%) 167 (91%) 17 (9%) 107 (58%)

BAK Cage

81 47 (58%) 34 (42%) 74 (91%) 7 (9%) 80 (99%) 1 (1%) 77 (95%) 4 (5%) 44 (54%) * re-operation, revision, removal or additional fixation ** major vessel injury, neurological damage or nerve root injury

Implant Lateral X-Ray Final Center of rotation 2mm dorsal sagital midline maximum footprint coverage – proper lordotic angles

Implant A/P X-Ray Final Center spike positioned on A/P midline

Final Position

Final AP & Lateral Position