Computational Biomechanics in Orthopedics

Jeff Bischoff

Prepared for: Computational Biomechanics

Colorado School of Mines

TKA CUSTOMERS

Patients

Positive1. Reduction of pain2. Basic movement3. Restoration of active lifestyle4. No return visits

Negative5. A quick fix without the effort (contemporary culture?)6. A big pay day (see DePuy)

Health care providers

Positive1. Satisfied patients2. Easy revisions3. No infections4. Quick surgery5. Intra-op options6. iSurgery – use of IT / social media in managing patient experience and info

Negative7. Idiot-proof solutions8. No lawsuits

Hospitals

Positive1. Minimal inventory2. Fewer marketing folks around3. No conflict of interest4. Maximum throughput5. Green solutions v disposables

Negative6. Cheap solutions

Government / Insurance (“Payers”)

Positive1. Evidence-based medicine (and billing)2. Reduced costs (reduced margins)3. Quick and appropriate responsiveness to clinical issues

Negative4. More for less (faster / cheaper / better)

Return

TKR REQUIREMENTS

Design Controls

User needs

Design requirements

Clinical usage

Design outputs

Engineering process

Example 1

User need: Bone conserving implant → metal and plastic are small / thin (with sufficient strength to withstand physiological loading)

Design input: Reduce the thickness of the anterior flangeby 10% in order to conserve more bone

Design verification → Design output: can use CAD to simply measure flange thickness and how much bone is preserved, cadaver evaluation for bone conservation

Validation: function in patients (bone preservation, longevity, f/u surgery)

Note: you would need other design inputs related to fatigue strength

Example 2

User need: Increased stability of a posterior-stabilized(PS) knee

Design input: PS post that has 10% less varus/valgus(V/V) laxity (wobbles less side to side)

Design verification → Design output: Computationalanalysis (?) / physical testing to demonstrate V/V laxity

Validation: Cadaveric evaluation of perceived stability by surgeons, function in patients (probably subjective reports of comfort and stability)

Example 3

User need: Posterior cruciate ligament retaining (CR) kneewith increased longevity relative to clinically-successfulpredicate (the 510k pathway!)

Design input: Utilize advanced materials and articularsurface design with 20% reduced wear relative to predicate

Design verification → Design output: Computational analysis for contact, maybe a numerical wear model, physical wear testing to 10.0Mc and analysis of wear rates

Validation: longevity and wear evolution in patients for up to 20 years(possibly x-ray measures of wear)