Computational Biomechanics in Orthopedics Jeff Bischoff Prepared for:Computational Biomechanics Colorado School of Mines

TKA CUSTOMERS

Patients Positive 1.Reduction of pain 2.Basic movement 3.Restoration of active lifestyle 4.No return visits Negative 1.A quick fix without the effort (contemporary culture?) 2.A big pay day (see DePuy)

Health care providers Positive 1.Satisfied patients 2.Easy revisions 3.No infections 4.Quick surgery 5.Intra-op options 6.iSurgery – use of IT / social media in managing patient experience and info Negative 1.Idiot-proof solutions 2.No lawsuits

Hospitals Positive 1.Minimal inventory 2.Fewer marketing folks around 3.No conflict of interest 4.Maximum throughput 5.Green solutions v disposables Negative 1.Cheap solutions

Government / Insurance (“Payers”) Positive 1.Evidence-based medicine (and billing) 2.Reduced costs (reduced margins) 3.Quick and appropriate responsiveness to clinical issues Negative 1.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 flange by 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: Computational analysis (?) / 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) knee with increased longevity relative to clinically-successful predicate (the 510k pathway!) Design input: Utilize advanced materials and articular surface 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)