Stability of the Medial Pivot Total Knee Prosthesis

NCT ID: NCT02577978

Last Updated: 2023-05-19

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 61 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2014-04-30
• Study Completion Date: 2017-06-30

Brief Summary

The purpose of this study is to compare objective and subjective measures of knee stability following total knee arthroplasty with a medial pivot design vs. a posterior stabilized design.

Detailed Description

Several different prostheses are available for use in total knee arthroplasty (TKA). These designs aim to replicate the normal kinematics of the knee joint while maintaining stability throughout a full range of motion. The posterior cruciate ligament (PCL) contributes to these functions in the native knee, and if preserved it can function similarly in the prosthetic knee. Prostheses in which the PCL is sacrificed, and its function not replaced by other means, have poorer outcomes. However, various problems with preserving the PCL, including PCL deterioration in arthritic knees and difficulties with proper tensioning, have led to the development of alternative ways to emulate normal femoral rollback and sagittal plane stability. These posterior-substituted (PS) designs substitute for the PCL with either a cam and post mechanism or a symmetrical ultra-congruent tibial insert.

The cruciate-retaining (CR) and PS designs, together with advances in surgical techniques and component materials, have achieved excellent implant survivorship with rates of > 90% at 20 years. Reports of functional outcomes, however, have been variable. One potential area for improvement in TKA is optimization of implant design to better approximate native knee kinematics. In the normal knee, the medial condyle remains stable in the sagittal plane, functioning like a ball-and-socket, whereas the lateral condyle translates anterior to posterior during flexion. The designs of the CR and PS knees do not allow for this medial-centered rotation. Analysis has revealed paradoxical anterior sliding of the femur during flexion, abnormal axial rotation, and condylar lift-off. Edge loading and increased sagittal plane motion may predispose to accelerated polyethylene wear. The posterior stabilized design uses a cam-and-post mechanism in which one piece of the prosthesis has a plastic post that fits into a slot in the other piece of the prosthesis.

A newer design that attempts to address these issues is the medial pivot knee (MP). This design is characterized by an asymmetrical tibial insert in which the medial compartment is ultra-congruent, providing antero-posterior stability and the lateral compartment allows for rollback around a medial axis of rotation i.e uses a ball-and-socket mechanism. This design more accurately recreates normal knee kinematics, reduces anteroposterior instability, and avoids condylar lift-off. Early studies indicate improved polyethylene wear characteristics. Midterm studies report excellent implant survivorship and clinical outcomes.

Several randomized trials have compared the MP knee favorably with other designs. Patients with bilateral TKAs with a different prosthesis on each side preferred their medial pivot knee to a PS, CR, or mobile-bearing (MB) design. A trial comparing the MP and PS designs found greater range of motion (ROM) and better patient-reported outcomes in the MP group at 2 years. There also exists literature reporting poorer outcomes with the MP design. A trial involving 96 patients who had received both an MP knee and an MB knee on contralateral sides found lower ROM, higher complication rates, and worse patient reported outcomes in the MP knee.

Given the lack of consensus in the literature, further investigation is warranted to determine the impact of the MP design on outcomes following TKA.

Conditions

Osteoarthritis of Knee

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: SINGLE_GROUP
• Primary Study Purpose: TREATMENT
• Blinding Strategy: SINGLE

Study Groups

Medacta Sphere

Ball-and-socket

Group Type: OTHER

Medacta GMK Sphere prosthesis

Intervention Type: DEVICE

Medacta PS

Cam-and-post

Group Type: OTHER

Medacta GMK posterior stabilized prosthesis

Intervention Type: DEVICE

Interventions

Medacta GMK posterior stabilized prosthesis

Intervention Type: DEVICE

Medacta GMK Sphere prosthesis

Intervention Type: DEVICE

Eligibility Criteria

Inclusion Criteria

• Age 18-85, regardless of gender, ethnicity, or pathology
• Must require a total knee arthroplasty
• All subjects must have given signed, informed consent prior to registration in study.

Exclusion Criteria

• Minors
• Any patients that are unable to consent
• Patients with active infection or osseous tumor of the operative extremity
• Patients undergoing revision surgery

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 85 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

Northwestern University

OTHER

Sponsor Role: lead

Responsible Party

David W. Manning

Associate Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

Northwestern Medicine Department of Orthopaedic Surgery

Chicago, Illinois, United States

Countries

United States

Provided Documents

Document Type: Study Protocol and Statistical Analysis Plan

View Document

Document Type: Informed Consent Form

View Document

Other Identifiers

STU00090745

Identifier Type: -

Identifier Source: org_study_id