Key Observations Contact area for many TKR designs decreases with increased flexion >20° –Bourne, Clin Orthop 2003 Small areas and high contact stress increases potential for PE wear and delamination in vivo 6.6 years Retrieved LCS ( Harman, ISTA 2003)
Articular conformity impacts materials Larger contact areas optimize load distribution during patient activity Lower contact stresses decrease potential for polyethylene wear Why Pivoting TKA?
3D Knee Contact Area and Stress Evaluated Using Finite Element Models Activity Model of Gait, Stair, Squat –Morra & Greenwald, ORL, Cleveland OH –2.5 – 4.5 BW loads –Flexion angles 0° - 135° –Non-linear UHMWPe material properties –Measured actual manufactured implants
Competitive data from: Morra, Harman, Greenwald: Computational models can predict polymer insert damage in total knee replacements. Surgery of the Knee 4 th Edition (Eds. Insall & Scott), 1(13):271-83, 2006 Contact Area and Stress at Heel Strike 3D Knee vs. Fixed Bearing TKR Designs Contact Area Duracon PFC Sigma Curve GenesisII CR NKII Ultra 3D Knee Contact Area (mm2) Contact Stress Duracon PFC Sigma Curve GenesisII CR NKII Ultra 3D Knee Contact Stress (MPa) Stress Range
Competitive data from: Morra, Greenwald: Polymer insert stress in TKR designs during high flexion activities. AAOS 2005 Contact Area during High Flexion Activities 3D Knee vs. High Flexion TKR Designs Contact stresses < 20 MPa during stair climbing Legacy LPS- Flex Fixed PFC Sigma RPF 3D Knee Contact Area (mm2) Squat (135) Chair (90) Stair (60) Includes post/cam contact area 3D Knee TM has 32% - 61% greater contact area during stair climbing compared to other high flexion designs
3DKnee TM Wear Test Industry Contract Between DJO Surgical and Clemson University Clemson University BioTribology Laboratory Testing occurred between June - December 2007 III: 3DKnee TM Wear Test
Dynamic Wear Test Data Instron/Stanmore 4-station force-controlled knee simulator 25% bovine serum at 37°C 5 million cycle tests Avg. weight loss was less than other designs
Results: TKR Kinematics III: 3DKnee TM Wear Test Lateral Pivoting Observed During Walking PLAY VIDEO Simulator Video 2
Highly Cross-linked vs. Non-cross- linked IV: Comparisons to the Literature GUR % BS GUR % BS GUR 4150 ?% BS GUR % BS DJO Surgical 3DKnee TM
Force vs. Displacement driven testing IV: Comparisons to the Literature GUR % BS GUR 4150 ?% BS GUR % BS GUR 1050 ?% BS DJO Surgical 3DKnee TM
3D Knee – Retrieval Analysis year follow-up 4 retrieved UHMWPe inserts –1 Male, 3 Female –Age at Index: –BMI: Reasons for Revision –Infection (2) at 11 and 13 mos. –Hemarthrosis (1) at 7 mos. –Diabetic capsulitis (1) at 6 mos.
11 Mon. LMLM 6 Mon. LMLM 7 Mon. LMLM 13 Mon. LMLM UHMWPe Articular Damage Pattern Dominant wear mode is burnishing, with some scratching & pitting Damage consistent with observations from other designs with short functional duration Scratches Burnish Pits Creep Striations Delamination Emb. Debris Abrasion Indistinguishable
Conclusions Wear Testing Simulators at Clemson University Performed To ISO Force-Control Standards 3DKnee TM system exhibited very low wear rate 3DKnee TM simulation confirms lateral pivot design 3DKnee TM outperforms a majority of published competition V: Conclusions
Analysis of 3D Knee Results: Clinical Outcomes at 5 Years WA Hodge 1,2,3, MK Harman 2, A. Mori 2, SA Banks 2,3,4 1 Hodge BioMotion Orthopaedics, Good Samaritan Medical Center, West Palm Beach, FL, USA 2 Institute for Mobility & Longevity, West Palm Beach, FL, USA 3 Dept. of Mechanical & Aero Engineering, Univ. of Florida, Gainesville, FL, USA 4 Dept. of Orthopaedics & Rehabilitation, Univ. of Florida, Gainesville, FL, USA Research grants have been received in support of these studies. One or more authors are paid consultants and/or receive royalties from DJO Surgical (Encore Medical).
509 knees Nov 2001-Aug 2008 Nov 2001-Aug males, 274 females 235 males, 274 females Age: 73+9 (30-93) yrs Age: 73+9 (30-93) yrs Weight: (50-159) kg Weight: (50-159) kg BMI: 28+5 (19-55) BMI: 28+5 (19-55) 5 Year Clinical Outcomes of ACL substituting TKR Design using Standard Approach
ACL substituting TKR Patient Cohort operated by Dr. Hodge in West Palm Beach, Florida USA Patients ExcludedPatients Excluded –6 patients (7 knees) deceased 4 Re-operations4 Re-operations –Severe adhesive capsulitis secondary to diabetic episodes –Synovectomy and PE exchange for recurrent hemarthrosis –Late infection with debridement and polyethylene exchange –Patellar resurfacing secondary to patella maltracking,pain 1 Revision of all components, 2 patellar revisions in same patient1 Revision of all components, 2 patellar revisions in same patient –Late infection arising from complications of lumbar laminectomy –Patellar loosening (bilateral in 1 patient at 3 years) This study presents the first 100 TKR patients with 2-6 year follow up
100 knees in 88 patients100 knees in 88 patients –Avg. follow-up: 4.2 (3-6) years –surgery Nov – Aug –45 males, 55 females –Age: 73+8 (43-88) years –Weight: (51-121) kg –BMI: 28+5 (20-40) –Diagnosis OA - 90 kneesOA - 90 knees RA - 10 kneesRA - 10 knees Initial 100 ACL substituting TKR with Average 4 Year Follow Up
Knee Society Score (pain, function)Knee Society Score (pain, function) Range of motionRange of motion Digital Goniometer tool for computerized measurement of digital radiographsDigital Goniometer tool for computerized measurement of digital radiographs Outcome Measures JR090 at 2 yrs.
Knee Society Scores (Pain/Motion) Pre-Op mos year year Mean Knee Society Score (Pain/Motion) 5 years year 97+7
Knee Society Scores (Function) Pre-Op mos year year Mean Knee Society Score (Function) 5 years year 97+7
Passive Flexion Pre-Op mos year year Mean Passive Flexion (deg) 5 years year At last follow-up, 68% have > 120° of flexion At last follow-up, 68% have > 120° of flexion
Radiographic Results TKR radiolucent lines TKR radiolucent lines 4 TKR exhibited wide RLL at 5 years4 TKR exhibited wide RLL at 5 years All showed no progression from 3 yearsAll showed no progression from 3 years 3 patients had clinically recurrent effusions3 patients had clinically recurrent effusions Pre-Op (3:1 varus : valgus) Pre-Op (3:1 varus : valgus) Varus 183° (176°-196°)Varus 183° (176°-196°) Valgus 170° (156°-175°)Valgus 170° (156°-175°) Limb correction = 6° (0°-15°)Limb correction = 6° (0°-15°) Post-op avg. 4 yrs. Post-op avg. 4 yrs. AP Limb = 176°+3° valgusAP Limb = 176°+3° valgus Tibial Slope = 5°+4°Tibial Slope = 5°+4° Patellar Tilt = 3°+3°Patellar Tilt = 3°+3°