In Vivo kinematics of a rotationally unconstrained, medially stabilized total knee Replacement

1. Mohamed A. Imam, Amanda Eifert, Richard Field, Vera
Pinskerova, John Skinner, Gareth Scott, Scott Banks
In Vivo kinematics of a rotationally unconstrained,
medially stabilized total knee Replacement
EFORT 2015, Prague

2. • Surgeons: Richard Field, Gareth Scott and John
Skinner
• We would like to acknowledge the efforts of L.
Kanouse, K. Steiner, E. Isaac, J. Buly, J. Curtis, J.
Hisole, C. Pearce, J. Stammers, A. Hartfield and J.
Gray for their efforts in carrying out this study
• This study was conducted under research
contract between the University of Florida,
the Elective Orthopaedic Centre and
Medacta.
Acknowledgments
Disclosures

3. Historical Background

4. • 1904- The Four Bar Concept
Historical Background
Brantigan OC, Voshell AF. The mechanics of the ligaments and menisci of the knee joint. J
Bone Jt Surg Am 1941;23(1):44–66.
• 1941- MC < LC movement
Zuppinger H. Die aktive Flexion im unbelasteten Kniegelenk. Zuricher Habil Schr 1904;703–
63.
• 1960s- The Cylinder-in-Cylinder
• 1994s- The Medial Pivot Rotating TKR

5. Background
- Bourne RB et al: Comparing patient outcomes after THA and TKA: is there a
difference? Clin Orthop Relat Res 2010;468:542-6.
- TKRs Vs THRs
- Native Knee
Kinematics
- Freeman MAR, Pinskerova V. The movement of the normal tibio-femoral joint. J.
Biomech. 2005:197–208.

6. • GMK Sphere™ implant design
– Medially stabilized articulation
– Laterally unconstrained articulation
• Goal – Provide stable medial
compartment and allow lateral
motion according to the patient’s
soft-tissues, implant alignment and
loads in activity.
Background

7. The purpose of the present paper is to
examine the movements of living knees
replaced with the GMK sphere
prosthesis to determine the extent to
which it succeeds or fails to replicate
those of the natural knee
AIM

8. • 16 knees with GMK Sphere TKA in 15 subjects
• 6 months or more post-surgery (RF, JS, GS)
• 66 years (53-76 years)
• 30 ± 3 BMI
• 40 ± 3 Oxford Knee Score (19 ± 7 pre-op)
• 87 KSS, 0.83 EQ5D, 85 Health Status
• 108° ± 8° Supine Active ROM
Subjects

9. • Lateral fluoroscopic imaging
during several activities
• Step-up/down on 22 cm step
• Lunge
• Kneel
• others …
• 3D knee kinematics
from model-image
registration
Methods and Measurements

10. • Lunge to maximum
flexion
– Flexion 120° ± 12°
– Tibial Rot 8° ± 6°
– Med AP -1mm ± 4mm
– Lat AP -6mm ± 4mm
Results

11. • Step-up/down
• ~2° tibial internal
rotation with flexion
• very little medial
translation
Results
• Very consistent
• ~1mm posterior lateral
translation with flexion
• lat. translation and tib.
rotation linked

12. Medially the condyle hardly moves antero-posteriorly from 0!
to 120 degrees
Laterally the femoral condyle and the contact area move
posteriorly but to a variable extent in the mid-range causing
tibial internal rotation to occur with flexion around a medial
axis.

13. Discussion
Does GMK Sphere provide translation comparable to
normal knee?
Study Cohort Flexion Tib Rot Med AP
Morooka1 Healthy 120° Kneel 13° -
Hamai 2 Med OA 120° Kneel 14° -
Current GMK Sphere
120° Kneel
120° Lunge
8° ± 6°
8° ± 6°
-2mm
-2mm
1- J Orthop Res (2008) 26:428-434
2- J Orthop Res (2009) 27:1555-1561

14. Exhibit tibial rotations that are:
Similar however less than observed in healthy normal
knees
CONCLUSIONS
GMK Sphere TKRS

15. Show Condylar Translations
that:
are intrinsically AP stable
over a range of activities,
(no “paradoxical” anterior
translation with flexion)
Similar in pattern, but
smaller in magnitude,
compared to healthy
normal knees.
Knees

16. Appear to function in vivo in a manner
consistent with the goals of the design.
Knees with GMK SPHERE

17. Thank You
Mohamed.Imam@aol.com