New Technology in Total Hip Replacement: “The Modern Day Hula Hoop” Douglas E Padgett, MD Chief, Adult Reconstruction and Joint Replacement Hospital For Special Surgery New York, NY
Disclosures Consultant : – DJO Global Hip Product – Pixarbio: pharma company Research Support: Trump Institute Board Affiliations: – The Hip Society – American Joint Replacement Registry – Journal of Arthroplasty
The Hula Hoop: Some History Origins trace back to native americans A form of dance for storytelling: – Certain gyrations associated with different animals or symbols
The Hula Hoop: Hawaiian Influence This form of expression has roots in the cultures of Polynesia and Hawaii Said to be the forebearer of the “hula-dance”
Hula Hoop History Lost As the “new frontier” was settled, the culture of the hula hoop was lost
History Regained In the 1950’s, the “Wham-O” toy company began to re- market the hula hoop At its peak, plastic hoops were being made at 50k per day! I remember fondly the words my dad used to Padgett Front Yard circa 1964 say, “Douglas……”
History “Re-lost” By the late1960’s, the craze was dead ! The sex, drugs and rock and roll crowd weren’t into it !
The Hula Hoop Today The craft of the street performer Popular with the “senior crowd” at the Y
What have we learned ? Trends in life often come and go!
Wise old Indian Saying: “All things that are good, will endure!”
Total Hip Replacement: A Case Study in Behavior The Stendahl Effect
Hip Arthritis Pre-Modern day era treatment of disabling pain of arthritis: – Fusion Poor function – Resection Even worse – Just live with it ! Cane Crutches wheelchair
Sir John Charnley: Banished to Wrightington Recognized the need to transfer load across hip joint Understood concerns of wear Developed the concept of the “Low Friction Arthroplasty”
Sir John Charnley Oversaw directly the manufacturing of implants Detailed surgical technique Only way to obtain access was to personally visit Mr. Charnley Harris, Wilson, Stinchfield etc
Success of the Charnley Procedure (circa 70-80’s) Results of LFA: – Uniform relief of pain – Improved mobility WALKING !! Return to sport never recommended ! Long term studies: – Wroblewski – Wilson / Salvati – Richard Johnston THR 1976
LFA by the 1980’s: Problems Identification of Issues: – Stem fixation durable provided technique accurate – However, socket fixation started to deteriorate after about 10 yrs !
Results of cemented sockets Failures: bone resorption due to either polymeric / acrylic debris
Biologic Fixation in THR Branemark’s “accidental” observation of bone integration into a titanium chamber (1952) First clinical application: dental implant to correct a cleft palate (1965) – Pt died in 2005 with implant intact !
Orthopaedic Application Jorge Galante, M.D. saw opportunity to apply this technology to orthopaedics Numerous basic experiments to determine the requisites for success
Requirements for Success in Biologic Fixation Proper implant surface: – In-growth – On-growth Stable bone-implant interface: NO MOTION ! Intimate host bone- implant contact NO GAPS !
Process of Biologic Fixation
1 st Generation Uncemented Sockets: HGP 1 Implant: – Titanium alloy shell – C.P. titanium fiber mesh Technique: – Line-to-line reaming – Supplemental screw fixation
Outcomes Danish study Scripps Clinic: – 324 hips – 60 hips with15-20 year results (mean 17.5) – 10 year followup – 10 revisions – Revision: Eccentric wear 5 infection lysis 3 dislocation 4 loose (1%) MGH 10 year min: – 3 liner dissocation – 1 cup revised for lysis – None loose
EXPLOSION !!!!!!!!!
Next 2 Decades: The Heyday of Hip Surgery Implants: Techniques: – Shape – Minimally Invasive 1-incision – Modularity 2-incision – Fixation Anterior Approach Bearings: – Metal – Ceramic – Polymers
But….what about Stendahl ? Stendahl: French author Went to Florence in the early 1800’s Was overwhelmed by the seeming never ending variety of opulent art As a result, become tachycardia/tachypneic mixed with bouts of confusion /disorientation
The Stendahl Effect: Are we susceptible ?
The Stendahl Effect in Orthopaedics Surgeons presented (confronted) by the “must-haves!” Forces: – Industry – Peers – Public
The Stendahl Effect: Orthopaedic Lemmings
Personal Confession
Stendahl Trap #1: Cement Fixation It was observed that the “bond” between the cement and the stem was …. ? Despite rare clinical significance, “solutions” were suggested
Improved Cement Adherence Let’s roughen the upper part of the stem or Apply a coating of acrylic directly to the implant so the cement sticks better Advocates: – Designers /Industry
Impact of “Improved Fixation” Dramatic increase in early femoral revisions: – Coutts / Santore: J Arthroplasty 2001 – Padgett, Hip society 1997
“Improvements in Cement Fixation” Winners: Losers: – Industry – Patients – Designers – Surgeons – Institutions – Payors
Lesson Learned The “bond” between a stem and cement is NOT perfectly rigid! Cement is subject to creep and therefore, polished stem subsidence is not a bad thing !
Stendahl Trap #2: Cementless Fixation in THR Most predictable fixation in THR: cup ! Despite excellent clinical results, retrieval analysis reveals only about 30% ingrowth
Improvement in Prosthetic Fixation: Use of Bio-ceramics Bio-ceramics (i.e.- hydroxyapatite) felt to ramp up the biologic effect and improve fixation In theory, better fixation should yield improved results Orthopaedic community response: – Overwhelming adoption !
Effect of Bio-ceramics upon outcome of THR Randomized clinical trials: – Socket: No effect on loosening rates – Stem: An almost (but not quite) significant decrease in thigh pain at 6 weeks which was no different by 3 months
“Improved Fixation in Cementless THR “ Winners : Losers: – Industry – Designers – At least no patients were harmed – Institutions bear the financial burden of a technology that probably has limited indications
Lesson Learned The amount of “increased bone in- growth” with ceramic enhanced implants in animal models, while statistically significant…..was of little clinical relevance!
Stendahl Trap # 3: Bearings Greatest long term threat to success in joint replacement surgery are issues of wear !
Early Bearings Polyethylene: – Think of your kitchen cutting board – Adversely affected by: Way it was stored Way it was sterilized Way it was made
Option to Poly: Consider Ceramic on Ceramic Ceramics: – Wettable – Smooth – Appear biologically inert – Improved fracture resistance
What about squeakers ?
Option to Poly: Consider Metal-on-Metal While Charnley prosthesis was the “gold standard”, McKee-Ferrar implant was developed Avoided use of polyethylene Maybe a well lubricated MOM bearing would be Note: monobloc stem !! more durable
Metal-on-Metal Hip Bearings What evolved: – Re-birth of the hip resurfacing – To appease the hip replacers: large diameter modular metal heads were offered for most stems
Orthopaedic Response to Large Diameter Heads Almost universal adoption across all bearing couples: – Ceramic on ceramic – Metal on Metal – Metal on Polyethylene Due to: – “normal range of motion” – “Elimination of dislocation”
Outcome Entire new lexicon: – ALVAL – Adverse Local tissue reaction – Trunnionosis – Recall Several major products with product liability ongoing
Large Diameter Heads in THR: Winners: Losers: – Due to recall litigation, probably nobody ! – Designers – Surgeons – Patients – Institutions
Lessons Learned The rapid introduction of MOM-THR was based upon the 510k process: – “substantial equivalence” – The predicate device in 1976 was the Charnley THR – This is not what John Charnley designed !
Stendahl Trap #4: Implant Design Standard implants are tapered wedges. Why ? – Relatively modest array of sizes fit vast majority of pts. – No need for L vs R – Easy to use – They work !
Implant Design: Tapered Implants Load bone proximally Distal stem more for alignment than fixation Some latitude to adjust the versional alignment but admittedly, limited What if we could control version independently ?
Hello Modularity ! Developed to independently obtain fixation in the bone, and then adjust: – Version – Offset By use of modular neck Original version was a Titanium alloy neck and titanium body: – Fracture !
New (and improved) Modular Stem: The Good Cobalt-chrome alloy neck fit into a titanium body Bench-top testing: – Improved fracture resistance Fairly widespread adoption: – No fractures seen in 1 st year !
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