New Technology in Total Hip Replacement: The Modern Day Hula Hoop - - PowerPoint PPT Presentation

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 say, “Douglas……”

Padgett Front Yard circa 1964

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

• f 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”

• bservation 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

1st 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

– 324 hips – 10 year followup – Revision:

5 infection 3 dislocation 4 loose (1%)

MGH 10 year min:

– 3 liner dissocation – 1 cup revised for lysis – None loose

Scripps Clinic:

– 60 hips with15-20 year results (mean 17.5) – 10 revisions

Eccentric wear lysis

EXPLOSION !!!!!!!!!

Next 2 Decades: The Heyday of Hip Surgery

Implants:

– Shape – Modularity – Fixation

Techniques:

– Minimally Invasive

1-incision 2-incision 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”

Losers:

– Patients – Surgeons – Institutions – Payors

Winners:

– Industry – Designers

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

• utcome 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 :

– Industry – Designers

Losers:

– 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 more durable

Note: monobloc stem !!

Metal-on-Metal Hip Bearings

What evolved:

– Re-birth of the hip resurfacing – To appease the hip replacers: large diameter modular metal heads were

• ffered 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

• ngoing

Large Diameter Heads in THR:

Losers:

– Designers – Surgeons – Patients – Institutions

Winners:

– Due to recall litigation, probably nobody !

Lessons Learned

The rapid introduction

• f 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 1st year !

Modular THR: The Bad

Within 2 years, many centers began to

• bserve pt’s with

atypical pain:

– Low grade ache – Limp – Decline in function

Infection was unlikely! Cross sectional imaging: adverse tissue response

Modular THR: The Ugly !

Massive soft tissue destruction Bone loss Difficult revision Outcomes of revision:

– Not good !

Dual Modular Necks: Impact of Corrosion

Alloy mismatch Impact of bending moments at neck- body taper causing fretting All in an aqueous environment

The Dual Modular Neck

Dual Modular Necks: HSS Series

– >200 stems implanted – 125 revised (and counting) – < 5% were either anteverted necks (basically, didn’t even need the modularity)

Modular THR:

Losers:

– Surgeons – Patients – Institutions

Winners:

– Due to recall litigation, probably nobody !

Yeah, that was then, this is now ! Should we be concerned ?

Maybe, past decade:

– Surgical approach ? – Outpatient Joint Replacement – “newer bearings”

Polyethylene additives Modular bearings

– Bioactive coatings

At what price ?

What can we take from this ?

4 Lessons to Avoid The Stendahl Effect

Lesson #1: Be Skeptical

Anything that seems “too good to be true” is probably exactly that ! Who benefits from this new idea ?

– Patients – Surgeons – Other 3rd Parties

Lesson #2: Be Logical: Use your brain !

Lesson #2: We are all scientists at heart !

Is the topic being presented, logical in thought ? Does, what is being promoted, answer a clinically relevant question ? How was the solution derived ?

Couldn’t we have predicted corrosion ?

Sometimes, it is so simple !

Lesson #3: Be Critical of Research Studies: Efficacy of Parachutes

Do we really to perform a RCT to confirm the efficacy of parachutes in jumping from an airplane ? Do we have any volunteers ? Statistical significance versus clinical relevance !

Lesson #3: Be Critical (skeptical)

• f the Regulators (eg. UK)

“The scandal of medical device regulation” BMJ 2012

– Reporters from the Telegraph – Submitted fictitious hip implant application

MODELLED AFTER A RECALLED IMPLANT !

– After review by a “notified body” (a third party independently charged with reviewing applications), device was approved pending factory visit !

Lesson #3: Be Critical What about the US ?

The 510(k) Process:

– 1976 law which established this implant as the predicate

Lesson #3 AAOS and Academic Centers

Challenge the academy to do the right thing.

– ASTM standards

Challenge academic centers to be as unbiased and fair in validating any new product or technique

– Honestly manage conflict !!

Lesson #4: Stick Together

Lesson #4: Be Loyal Don’t be tempted by fame or $$

Lesson #4: Look out for one another !

Orthopaedics is a team sport Learn from one another. Support one another If something doesn’t work, let others know!

Closing Thoughts

Leadership: Don’t be a lemming ! Volunteerism: Make a difference Education: A lifelong commitment Humility: Critical analysis Do the right thing!

Thank You

Thank You