Biomechanical Effects of Femoral Component Axial Rotation in Total Knee Arthroplasty (TKA)

Transcription

1 Biomechanical Effects of Femoral Component Axial Rotation in Total Knee Arthroplasty (TKA) Mohammad Kia, PhD, Timothy Wright, PhD, Michael Cross, MD, David Mayman, MD, Andrew Pearle, MD, Peter Sculco, MD, Geoffrey Westrich, MD, Carl Imhauser, PhD

2 Disclosures Timothy Wright, PhD receives royalties from and owns stock in Exactech, Inc. Michael Cross, MD is a paid consultant for Exactech, Inc. Geoffrey Westrich, MD is a paid consultant and speaker for Exactech, Inc.

3 Total Knee Replacement (TKR) Osteoarthritis TKR After Femoral component Tibial insert

4 Patient Dissatisfaction Following TKR

5 Femoral Component Alignment Femoral cuts Femoral component

6 Femoral Component Rotation Tibiofemoral kinematics Patellofemoral kinematics Articular contact force Collateral ligament tension

7 Excessive Internal Rotation of the Femoral Component Qualitatively increases medial collateral ligament (MCL) tension Knee pain and stiffness Anouchi YS, et al. Clin Orthop Relat Res. Feb 1993

8 External Rotation medial sulcus lateral epicondyle TEA 3-4 PCA

9 Variability from Patient to Patient

10 Research Questions How does external rotation alter collateral ligament tensions and tibiofemoral contact forces across a subpopulation of knees? What anatomic factors of the femoral condyle explain variations in maximum MCL tension among knees?

11 Computational Model Kia et al. J Biomech Eng 2016

12 Role of Modeling in Ideation Apply Forces Control Ligament Properties Predict Loads -Contact -Ligament Sensitivity Femoral Component Rotation Ideation Implant Placement

13 Model Development recipe

14 Bony Geometries Three neutrally aligned, nonarthritic, male cadaveric legs Ages: 20,21, 42 Obtained from CT scans 0.6 mm slice thickness, 0.6x0.6 mm 2 in-plane pixel dimensions

15 Implant Design Optetrak Logic TM Posterior Stabilized (PS) Knee Exactech Inc. 8mm 9mm 8mm

16 Implant Placement via Measured Resection Proximal tibial cut Perpendicular to mechanical axis Max 9 mm bone resection Distal femoral cut Perpendicular to mechanical axis Max 8 mm bone resection

17 Posterior Femoral Cut Long axis 3 PCA

18 Model of Soft Tissue Envelope

19 Medial Collateral Ligament (MCL) Proximal Transverse Distal

20 Force Ligament Properties Slack length Toe region Linear region Elongation Kia et al. J Biomech Eng 2016

21 Contact Force F c = Ax b

22 Method to Address Question One Input Flexion Arc N Femoral component external rotation Output Force Collateral ligaments Contact

23 Representative Simulations 0 9 MCL LCL

24 MCL tension (N) Medial Collateral Ligament Knee 1 Knee 2 Knee 3 Flexion ( ) Flexion ( ) Flexion ( )

25 LCL tension (N) Lateral Collateral Ligament Knee 1 Knee 2 Knee 3 Flexion ( ) Flexion ( ) Flexion ( )

26 Medial Contact (N) Medial Compartment Contact Knee 1 Knee 2 Knee 3 Flexion ( ) Flexion ( ) Flexion ( )

27 Lateral Contact (N) Lateral Compartmental Contact Knee 1 Knee 2 Knee 3 Flexion ( ) Flexion ( ) Flexion ( )

28 Method to Address Question Two Posterior cut r p Medial sulcus TEA ratio = r p r d r d Distal cut

29 Max MCL Tension vs. TEA ratio

30 Method to Address Question Two Posterior cut r p Proximal MCL insertion MCL ratio = r p r d r d Distal cut

31 Max MCL Tension vs. MCL ratio

32 Discussion

33 Clinical Implications MCL tension = Subfailure damage Difference in compartmental contact forces = Patient satisfaction

34 Patent Pending

35 Acknowledgements Clark and Kirby Foundations Hospital for Special Surgery Adult Reconstruction and Joint Replacement Service Research Grant

36 Thank you

37 Appendix

38 External ( ) Internal/External Tibial Rotation Knee 1 Knee 2 Knee 3 Flexion ( ) Flexion ( ) Flexion ( )

39 Varus ( ) Varus/Valgus Rotation Knee 1 Knee 2 Knee 3 Flexion ( ) Flexion ( ) Flexion ( )

40 Ligament property Toe region Linear region F(l, l, l 0 ) = 1 n f l + c d lb 1 B 2 + K l l 0 + Δ t + f l 0 + Δ t + c d lb 1 B 3 B 1 = step l, 0, 0, l + 0.1, 1 B 2 = step l, l 0, 0, l , 1 step l, l 0 + Δ t, 1, l 0 + Δ t ,0 B 3 = step l, l 0 + Δ t, 0, l 0 + Δ t ,1

41 Optimization 9 a min F i,j m l, l, l F i e 4 i=1 j=1 a = number of fibers for each ligament with 9 ligaments included in the optimization F i m = ACL, smcl, LCL, FFL, OPL, POL, MPC, LPC, PCL PM F e i = 37, 4, 20, 1, 10, 18, 1, 4, 10 N a = 6, 6, 1, 1, 2, 3, 3, 3, 4 fibers l 0 = l e 100 x % 10 x +10

42 Ligament Force F Optimization Ligament force at full extension (F e )- from the experiment F e Ligament length at full extension (l e )- from the model l e l 0 Ligament length l

43 Ligament Force Optimization F e F Ligament force at full extension (F e ) Ligament length at full extension (l e ) l 0 l e Ligament length l

44 Ligament Force Optimization F Ligament force at full extension (F e ) F e Ligament length at full extension (l e ) 0. 9 l e l 0 l e 1. 1 l e Ligament length l

45 Lateral Contact (N) Medial Contact (N) Lateral vs. Medial Contact Force Knee 3 Knee 3 Flexion ( ) Flexion ( )

46 Method to Address Question Two Medial sulcus Posterior cut Medial sulcus r p stea ratio = r p r d r d Distal cut

47 Force (N) Contact Force Experiment Power function R 2 = Displacement (mm)

48 Method to Address Question Two r p Proximal MCL insertion r d MCL ratio = r p r d

49 Medial Collateral Ligament (MCL) MCL Proximal Transverse Distal