Mechanics Analysis of Patients Having a Sigma Mobile Bearing TKA

In Vivo Mechanics Analysis of Patients Having a Sigma Mobile Bearing TKA

Utilize previously developed mathematical model to determine in vivo knee mechanics (kinematics, forces, stresses, areas and sound) for subjects having a Sigma Posterior Stabilizing (PS) mobile bearing (MB) total knee arthroplasty (TKA). There are several hypotheses for this study, although the most prominent is: Subjects having a Sigma RP PS TKA will experience polyethylene bearing rotation at 10 years post-operative, similar to their previous evaluations at six months, two years and five years.

Additional hypotheses:

• Subjects having a Sigma RP PS TKA will experience full ideal femorotibial contact mechanics.
• Subjects having a Sigma RP PS TKA will experience optimal cam/post mechanics.
• Subjects having a Sigma RP PS TKA will experience continuous axial rotation in deep flexion.
• Subjects having a Sigma RP PS TKA will experience optimal distribution of tibio-femoral and cam/post contact forces over a broad area on the post.
• Subjects having a Sigma RP PS TKA will experience a smooth transition of the cam on the post, not an abrupt slide as seen with fixed bearing PS TKA.
• The use of the sound sensors will detect cam/post contact mechanics under in vivo conditions.

Inclusion Criteria:

• At least six months post-operative
• Between 40-85 years of age
• Have a body weight of less than 250 lbs.
• Judged clinically successful with a AKS greater than 90
• Have the DePuy Sigma mobile bearing TKA
• Good-to-excellent post-operative passive flexion
• Must be willing to sign the IC and HIPAA forms.

Exclusion Criteria:

• Pregnant females
• Those not willing to sign the IC and HIPAA forms