Clinical trial NCT02577978: Stability of the Medial Pivot Total Knee Prosthesis
Official title: Stability of the Medial Pivot Total Knee Prosthesis
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Osteoarthritis of Knee
Lead sponsor: Northwestern University
Sponsor class: OTHER
First posted: 2015-10-16
Enrollment: 61
Sex: ALL
Minimum age (years): 18
Maximum age (years): 85
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: SINGLE_GROUP
Primary purpose: TREATMENT

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.

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

Primary outcomes:
measure: Oxford Knee Score (OKS) Pre-operative Through 2 Years Post-operative
timeFrame: Pre-operatively on day of surgery, 6 weeks, 3 months, 6 months, 12 months and 24 months post-operatively
measure: Veteran's RAND 12 (VR-12) Mental Composite Score (MCS) Through 2 Years Post Operative
timeFrame: Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.
measure: Veteran's RAND 12 (VR-12) Physical Composite Score (PCS) Through 2 Years Post Operative
timeFrame: Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.
measure: PROMIS Computerized Adaptive Tests (CATs) for Physical Function Through 2 Years Post-operative
timeFrame: Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.
measure: PROMIS Computerized Adaptive Tests (CATs) for Pain Interference Through 2 Years Post-operative
timeFrame: Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.
measure: PROMIS Computerized Adaptive Tests (CATs) for Pain Behavior Through 2 Years Post-operative
timeFrame: Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.
measure: Total Score Calculated Using the Forgotten Joint Score in Order to Assess the Subject's Ability to Forget the Artificial Joint in Everyday Life
timeFrame: 12 months post-operatively
measure: International Knee Documentation Committee (IKDC) Questionnaire Assessed Through 2 Years Post-op
timeFrame: Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively.
measure: Score for the Knee Society Score (KSS) Knee Component at 1 Year Post-operatively
timeFrame: 12 months post-operatively
measure: Score for the Knee Society Score (KSS) Function Component at 1 Year Post-operatively
timeFrame: 12 months post-operatively
Secondary outcomes:
measure: Assessing Knee Stability Using the KT-1000 Arthrometer (at 30 Degrees)
timeFrame: 1 year post-operatively
measure: Assessing Knee Stability Using the KT-1000 Arthrometer (at 90 Degrees)
timeFrame: 1 year post-operatively
measure: Get-up-and-Go Test
timeFrame: Between 6 months and 1 year post-operatively
Other outcomes:
Locations:
city: Chicago
country: United States
facility: Northwestern Medicine Department of Orthopaedic Surgery
state: Illinois
Study officials:
References: