3D Knee3D Knee™™ Longevity & WearLongevity & Wear

Why Knees Fail?Why Knees Fail?• 212 consecutive revised TKA, 1997-

2000Sharkey et al., CORR, 404, 2002

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)

3D Knee™ Articular 3D Knee™ Articular DesignDesign

• Fully congruent lateral compartment

• Widened medial condyle

• Constant sagittal profile > 70° flexion

3D Knee™ Contact Area and 3D Knee™ Contact Area and Stress Evaluated Using Finite Stress Evaluated Using Finite Element ModelsElement 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 4th Edition (Eds. Insall & Scott), 1(13):271-83, 2006

Contact Area and Stress at Heel Contact Area and Stress at Heel StrikeStrike

3D Knee™ vs. Fixed Bearing TKR DesignsContact Area

0 100 200 300 400

Duracon

PFC SigmaCurve

GenesisIICR

NKII Ultra

3D Knee

Contact Area (mm2)

Contact Stress

0 10 20 30 40

Duracon

PFC SigmaCurve

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 Contact Area during High Flexion ActivitiesActivities

3D Knee™ vs. “High Flexion” TKR Designs

Contact stresses < 20 MPa during stair climbing

0 100 200 300 400 500

Legacy LPS-Flex Fixed

PFC SigmaRPF

3D Knee

Contact Area (mm2)

Squat (135)Chair (90)Stair (60)

Includes Includes post/cam post/cam

contact areacontact area3D KneeTM has 32% - 61% greater contact area

during stair climbing compared to other “high flexion” designs

3DKneeTM Wear Test• Industry Contract Between

DJO Surgical and Clemson University

• Clemson UniversityBioTribology Laboratory

• Testing occurred between June - December 2007

III: 3DKneeTM Wear Test

Dynamic Wear Test Dynamic Wear Test DataData

• Instron/Stanmore 4-station force-controlled knee simulator

• 25% bovine serum at 37°C

• 5 million cycle tests

Avg. weight loss Avg. weight loss was less than was less than other designsother designs

Results: TKR Kinematics

III: 3DKneeTM Wear Test

• Lateral Pivoting Observed During Walking

PLAY VIDEOSimulator Video 2

Highly Cross-linked vs. Non-cross-

linked

IV: Comparisons to the Literature

GUR 4150100% BS

GUR 105050% BSGUR 4150?% BS

GUR 102050% BS

DJO Surgical 3DKneeTM

3D Knee™ – Retrieval 3D Knee™ – Retrieval AnalysisAnalysis

• 100 knees @ 2-5 year follow-up• 4 retrieved UHMWPe inserts

– 1 Male, 3 Female– Age at Index: 58-72– BMI: 27-33

• Reasons for Revision– Infection (2) at 11 and 13 mos.– Hemarthrosis (1) at 7 mos.– Diabetic capsulitis (1) at 6 mos.

11 Mon.

L M

6 Mon.

L M

7 Mon.

L M

13 Mon.

L M

UHMWPe Articular Damage UHMWPe Articular Damage PatternPattern

Dominant wear

mode is

burnishing, with

some scratching &

pitting

Damage consistent

with observations

from other designs

with short

functional duration Scratches

Burnish

Pits Creep

StriationsDelamination

Emb. DebrisAbrasion

Indistinguishable

Conclusions

• Wear Testing Simulators at Clemson University Performed To ISO Force-Control Standards

• 3DKneeTM system exhibited very low wear rate

• 3DKneeTM simulation confirms lateral pivot design

• 3DKneeTM outperforms a majority of published competition

V: Conclusions

Analysis of 3D Knee™ Results: Analysis of 3D Knee™ Results: Clinical Outcomes at 5 YearsClinical Outcomes at 5 Years

WA Hodge1,2,3, MK Harman2, A. Mori2, SA Banks2,3,4 1Hodge BioMotion Orthopaedics, Good Samaritan Medical Center, West Palm Beach, FL,

USA 2Institute for Mobility & Longevity, West Palm Beach, FL, USA

3Dept. of Mechanical & Aero Engineering, Univ. of Florida, Gainesville, FL, USA4Dept. 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 knees509 knees• Nov 2001-Aug 2008 Nov 2001-Aug 2008 • 235 males, 274 females235 males, 274 females• Age: 73Age: 73++9 (30-93) yrs9 (30-93) yrs• Weight: 83+18 (50-159) Weight: 83+18 (50-159) kgkg• BMI: 28BMI: 28++5 (19-55)5 (19-55)

5 Year Clinical Outcomes of5 Year Clinical Outcomes of

“ACL substituting” TKR Design “ACL substituting” TKR Design

using Standard Approachusing Standard Approach

• 100 knees in 88 patients 100 knees in 88 patients – Avg. follow-up: 4.2 (3-6) yearsAvg. follow-up: 4.2 (3-6) years– surgery Nov. 2001 – Aug. 2004surgery Nov. 2001 – Aug. 2004– 45 males, 55 females45 males, 55 females– Age: 73Age: 73++8 (43-88) years8 (43-88) years– Weight: 81Weight: 81++16 (51-121) kg16 (51-121) kg– BMI: 28BMI: 28++5 (20-40)5 (20-40)– DiagnosisDiagnosis

• OA - 90 kneesOA - 90 knees• RA - 10 kneesRA - 10 knees

Initial 100 “ACL substituting” TKR Initial 100 “ACL substituting” TKR with Average 4 Year Follow Upwith Average 4 Year Follow Up

• Knee Society Score Knee Society Score (pain, function)(pain, function)

• Range of motionRange of motion

• ““Digital Goniometer” tool Digital Goniometer” tool for computerized measurement for computerized measurement of digital radiographsof digital radiographs

Outcome MeasuresOutcome Measures

JR090 at 2 yrs.

Knee Society Scores (Pain/Motion)Knee Society Scores (Pain/Motion)

Pre-OpPre-Op4747++1111

3 mos3 mos9292++1111

1 year1 year9696++77

2 year2 year9898++44

00

2020

4040

6060

8080

100100

Mean Knee Society Score (Pain/Motion)Mean Knee Society Score (Pain/Motion)

5 years5 years9797++55

3 year3 year9797++77

Knee Society Scores (Function)Knee Society Scores (Function)

Pre-OpPre-Op5151++1212

3 mos3 mos8585++2020

1 year1 year9595++1111

2 year2 year9595++1010

00

2020

4040

6060

8080

100100

Mean Knee Society Score (Function)Mean Knee Society Score (Function)

5 years5 years9595++12123 year3 year

9797++77

Passive FlexionPassive Flexion

Pre-OpPre-Op107107++88

3 mos3 mos113113++1212

1 year1 year119119++1010

2 year2 year121121++1010

8080

9090

100100

110110

120120

130130

Mean Passive Flexion (deg)Mean Passive Flexion (deg)

5 years5 years

121121++10103 year3 year

121121++1010

At last follow-up, At last follow-up, 68% have 68% have >> 120 120°° of flexion of flexion

Radiographic ResultsRadiographic Results

TKR radiolucent linesTKR radiolucent lines• 4 TKR exhibited “wide” RLL at 5 4 TKR exhibited “wide” RLL at 5

yearsyears

• All showed no progression from All showed no progression from 3 years3 years

• 3 patients had clinically 3 patients had clinically recurrent effusionsrecurrent effusions

Pre-Op (3:1 varus : Pre-Op (3:1 varus : valgus)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 Alignment @ Post-op Alignment @ avg. 4 yrs.avg. 4 yrs.• AP Limb = 176°AP Limb = 176°++3° valgus3° valgus

• Tibial Slope = 5°Tibial Slope = 5°++4°4°

• Patellar Tilt = 3°Patellar Tilt = 3°++3°3°

Thank You

West Palm Beach, Florida USA