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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.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Medacta Sphere | Other | Ball-and-socket |
|
| Medacta PS | Other | Cam-and-post |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Medacta GMK posterior stabilized prosthesis | Device |
| ||
| Medacta GMK Sphere prosthesis |
| Measure | Description | Time Frame |
|---|---|---|
| Oxford Knee Score (OKS) Pre-operative Through 2 Years Post-operative | Patient completed Oxford Knee Score questionnaire used to assess the patient's perspective of outcome following Total Knee Arthroplasty (TKA); score range is reported between 0-48 with improvement in outcomes reflected as a higher numerical value (e.g. a 'complete' return to pre-disease functionality would be reported as a score of 48) | Pre-operatively on day of surgery, 6 weeks, 3 months, 6 months, 12 months and 24 months post-operatively |
| Veteran's RAND 12 (VR-12) Mental Composite Score (MCS) Through 2 Years Post Operative | Veteran's RAND 12 Item Health Survey used to assess health-related quality of life, to estimate disease burden, and to evaluate disease-specific benchmarks. Scores for the Mental Composite Score (MCS) range from 5.2 to 76.3 and are evaluated as a summative T-score with population mean of 50 (Standard Deviation = 10);higher scores indicate improved mental wellness/function as reported by patients. | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
| Veteran's RAND 12 (VR-12) Physical Composite Score (PCS) Through 2 Years Post Operative | Veteran's RAND 12 Item Health Survey used to assess health-related quality of life, to estimate disease burden, and to evaluate disease-specific benchmarks. Scores for the Physical Composite Score (MCS) range from 6.3 to 71.8 and are evaluated as a summative T-score with population mean of 50 (Standard Deviation = 10);higher scores indicate improved physical wellness/function as reported by patients. | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
| PROMIS Computerized Adaptive Tests (CATs) for Physical Function Through 2 Years Post-operative | Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Physical Function domain higher scores indicated improved physical function as reported by the patient |
| Measure | Description | Time Frame |
|---|---|---|
| Assessing Knee Stability Using the KT-1000 Arthrometer (at 30 Degrees) | Used for grading the stability of the knee in various degrees of flexion according to section 4 of the International Knee Documentation Committee's Knee Ligament Standard Evaluation Form where normal (-1 to 2 mm); nearly normal (3 to 5 mm); abnormal (6 to 10 mm); severely abnormal (>10 mm) | 1 year post-operatively |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Northwestern Medicine Department of Orthopaedic Surgery | Chicago | Illinois | 60611 | United States |
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| ID | Title | Description |
|---|---|---|
| FG000 | Medacta Sphere | Ball-and-socket Medacta GMK Sphere prosthesis |
| FG001 | Medacta PS | Cam-and-post Medacta GMK posterior stabilized prosthesis |
| Title | Milestones | Reasons Not Completed | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Overall Study |
|
From the total 61 patients enrolled, 11 patients (7 sphere, 4 PS) were dropped from the study due to loss to follow-up. The remainder 50 had data collected.
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| ID | Title | Description |
|---|---|---|
| BG000 | Medacta Sphere | Ball-and-socket Medacta GMK Sphere prosthesis |
| BG001 | Medacta PS | Cam-and-post Medacta GMK posterior stabilized prosthesis |
| Units | Counts |
|---|---|
| Participants |
|
| Title | Description | Population Description | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Denominator Units Selected | Denominators | Classes |
|---|---|---|---|---|---|---|---|---|---|
| Age, Categorical | Count of Participants |
| Type | Title | Description | Population Description | Reporting Status | Anticipated Posting Date | Parameter Type | Dispersion Type | Unit of Measure | Calculate Percentage | Time Frame | Units Analyzed | Denominator Units Selected | Arm/Group Information | Denominators | Classes | Analyses | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Primary | Oxford Knee Score (OKS) Pre-operative Through 2 Years Post-operative | Patient completed Oxford Knee Score questionnaire used to assess the patient's perspective of outcome following Total Knee Arthroplasty (TKA); score range is reported between 0-48 with improvement in outcomes reflected as a higher numerical value (e.g. a 'complete' return to pre-disease functionality would be reported as a score of 48) | Posted | Mean | Standard Deviation | score on a scale | Pre-operatively on day of surgery, 6 weeks, 3 months, 6 months, 12 months and 24 months post-operatively |
|
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All-Cause Mortality, Serious, and Other (Not Including Serious) Adverse Events were not monitored/assessed
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| ID | Title | Description | Deaths (Affected) | Deaths (At Risk) | Serious Events (Affected) | Serious Events (At Risk) | Other Events (Affected) | Other Events (At Risk) |
|---|---|---|---|---|---|---|---|---|
| EG000 | Medacta Sphere | Ball-and-socket Medacta GMK Sphere prosthesis | 0 |
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| Title | Organization | Phone | Extension | |
|---|---|---|---|---|
| David W Manning | Northwestern Medicine | 3124726023 | David.Manning@nm.org |
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| Type | Includes Protocol | Includes SAP | Includes ICF | Document Label | Document Date | Document Uploaded Date | Document File Name |
|---|---|---|---|---|---|---|---|
| Prot_SAP | Yes | Yes | No | Study Protocol and Statistical Analysis Plan | Apr 8, 2016 | Mar 12, 2019 | Prot_SAP_000.pdf |
| ICF | No | No | Yes | Informed Consent Form | Mar 10, 2015 | Mar 12, 2019 | ICF_001.pdf |
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| ID | Term |
|---|---|
| D020370 | Osteoarthritis, Knee |
| ID | Term |
|---|---|
| D010003 | Osteoarthritis |
| D001168 | Arthritis |
| D007592 | Joint Diseases |
| D009140 | Musculoskeletal Diseases |
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| Device |
|
| Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
| PROMIS Computerized Adaptive Tests (CATs) for Pain Interference Through 2 Years Post-operative | Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Pain Interference domain an increased value indicates greater severity/frequency of pain reported by the patient. | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
| PROMIS Computerized Adaptive Tests (CATs) for Pain Behavior Through 2 Years Post-operative | Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Pain Behavior domain an increased value indicates greater severity/frequency of pain reported by the patient | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
| Total Score Calculated Using the Forgotten Joint Score in Order to Assess the Subject's Ability to Forget the Artificial Joint in Everyday Life | Patient completed questionnaire used to assess the patients' ability to forget about a joint as a result of successful treatment. Every question is scored 1 (never) to 5 (mostly) according to the selected response categories. Thus, the raw score ranges from 12 to 60 where a high score indicates an improved outcome. The raw score is linearly transformed to a 0-100 scale and then reversed to obtain the final score with higher scores indicating improved physical function/reduced impact of symptoms on activity: Final score = 100 - ((sum(item01 to item12) - 12)/48*100) | 12 months post-operatively |
| International Knee Documentation Committee (IKDC) Questionnaire Assessed Through 2 Years Post-op | The International Knee Documentation Committe (IKDC) Questionnaire is a subjective scale that provides patients with an overall function score based on a summative score for 3 sub categories (knee function, sports activities, pain/symptoms). A score between 0-100 is obtained as the sum of scores for each individual question, with increasing composite scores correlating positively with patient functional status/quality of life. | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
| Score for the Knee Society Score (KSS) Knee Component at 1 Year Post-operatively | Physician completed Knee Society Score questionnaire used to measure a patient's functional ability before and after total knee arthroplasty (TKA); score range is reported between 0-100 with improvement in outcomes reflected as a higher numerical value (e.g. a 'complete' return to pre-disease functionality would be reported as a score of 100) | 12 months post-operatively |
| Score for the Knee Society Score (KSS) Function Component at 1 Year Post-operatively | Physician completed Knee Society Score questionnaire used to measure a patient's functional ability before and after total knee arthroplasty (TKA); score range is reported between 0-100 with improvement in outcomes reflected as a higher numerical value (e.g. a 'complete' return to pre-disease functionality would be reported as a score of 100) | 12 months post-operatively |
| Assessing Knee Stability Using the KT-1000 Arthrometer (at 90 Degrees) | Used for grading the stability of the knee in various degrees of flexion according to section 4 of the International Knee Documentation Committee's Knee Ligament Standard Evaluation Form where normal (-1 to 2 mm); nearly normal (3 to 5 mm); abnormal (6 to 10 mm); severely abnormal (>10 mm) | 1 year post-operatively |
| Get-up-and-Go Test | Used to assess a person's mobility and requires both static and dynamic balance. It uses the time that a person takes to rise from a chair, walk three metres, turn around, walk back to the chair, and sit down. | Between 6 months and 1 year post-operatively |
| BG002 | Total | Total of all reporting groups |
| Participants |
|
| Age, Continuous | Mean | Standard Deviation | years |
|
| Sex: Female, Male | Count of Participants | Participants |
|
| Ethnicity (NIH/OMB) | Count of Participants | Participants |
|
| Race (NIH/OMB) | Count of Participants | Participants |
|
| Region of Enrollment | Number | participants |
|
| Body Mass Index (BMI) | Mean | Standard Deviation | kg/m^2 |
|
| Pre-Operative Ambulatory Status | Patient's ability to ambulate unassisted or assisted with a gait aid | Count of Participants | Participants |
|
| Hypertension | Patients with a medical history significant for hypertension | Count of Participants | Participants |
|
| Diabetes Mellitus | Patients with medical history significant for diabetes mellitus | Count of Participants | Participants |
|
| History of VTE | Patients with medical history significant for venous thromboembolism (VTE) | Count of Participants | Participants |
|
| Pre-operative Narcotic Use | Patients with recent history of narcotic use for pain management prior to surgery | Count of Participants | Participants |
|
| Tobacco Use | Patients with active or recent tobacco use prior to surgery | Count of Participants | Participants |
|
| Coronary Artery Disease | Patients with medical history significant for coronary artery disease | Count of Participants | Participants |
|
|
|
| Primary | Veteran's RAND 12 (VR-12) Mental Composite Score (MCS) Through 2 Years Post Operative | Veteran's RAND 12 Item Health Survey used to assess health-related quality of life, to estimate disease burden, and to evaluate disease-specific benchmarks. Scores for the Mental Composite Score (MCS) range from 5.2 to 76.3 and are evaluated as a summative T-score with population mean of 50 (Standard Deviation = 10);higher scores indicate improved mental wellness/function as reported by patients. | Posted | Mean | Standard Deviation | score on a scale | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
|
|
|
| Primary | Veteran's RAND 12 (VR-12) Physical Composite Score (PCS) Through 2 Years Post Operative | Veteran's RAND 12 Item Health Survey used to assess health-related quality of life, to estimate disease burden, and to evaluate disease-specific benchmarks. Scores for the Physical Composite Score (MCS) range from 6.3 to 71.8 and are evaluated as a summative T-score with population mean of 50 (Standard Deviation = 10);higher scores indicate improved physical wellness/function as reported by patients. | Posted | Mean | Standard Deviation | score on a scale | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
|
|
|
| Primary | PROMIS Computerized Adaptive Tests (CATs) for Physical Function Through 2 Years Post-operative | Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Physical Function domain higher scores indicated improved physical function as reported by the patient | Posted | Mean | Standard Deviation | score on a scale | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
|
|
|
| Primary | PROMIS Computerized Adaptive Tests (CATs) for Pain Interference Through 2 Years Post-operative | Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Pain Interference domain an increased value indicates greater severity/frequency of pain reported by the patient. | Posted | Mean | Standard Deviation | score on a scale | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
|
|
|
| Primary | PROMIS Computerized Adaptive Tests (CATs) for Pain Behavior Through 2 Years Post-operative | Patient-reported outcome (PRO) measures use answers that patients provide to questions to produce numeric values which indicate patients' state of wellbeing or suffering as well as their ability or lack of ability to function. Values are reported as T-scores with a reference population mean of 50 (SD=10); for the Pain Behavior domain an increased value indicates greater severity/frequency of pain reported by the patient | Posted | Mean | Standard Deviation | score on a scale | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
|
|
|
| Primary | Total Score Calculated Using the Forgotten Joint Score in Order to Assess the Subject's Ability to Forget the Artificial Joint in Everyday Life | Patient completed questionnaire used to assess the patients' ability to forget about a joint as a result of successful treatment. Every question is scored 1 (never) to 5 (mostly) according to the selected response categories. Thus, the raw score ranges from 12 to 60 where a high score indicates an improved outcome. The raw score is linearly transformed to a 0-100 scale and then reversed to obtain the final score with higher scores indicating improved physical function/reduced impact of symptoms on activity: Final score = 100 - ((sum(item01 to item12) - 12)/48*100) | Posted | Mean | Standard Deviation | score on a scale | 12 months post-operatively |
|
|
|
| Primary | International Knee Documentation Committee (IKDC) Questionnaire Assessed Through 2 Years Post-op | The International Knee Documentation Committe (IKDC) Questionnaire is a subjective scale that provides patients with an overall function score based on a summative score for 3 sub categories (knee function, sports activities, pain/symptoms). A score between 0-100 is obtained as the sum of scores for each individual question, with increasing composite scores correlating positively with patient functional status/quality of life. | Posted | Mean | Standard Deviation | score on a scale | Pre-operatively, 6 weeks post-operatively, 3 months post-operatively, 6 months post-operatively, 12 months post-operatively, and 2 years post-operatively. |
|
|
|
| Primary | Score for the Knee Society Score (KSS) Knee Component at 1 Year Post-operatively | Physician completed Knee Society Score questionnaire used to measure a patient's functional ability before and after total knee arthroplasty (TKA); score range is reported between 0-100 with improvement in outcomes reflected as a higher numerical value (e.g. a 'complete' return to pre-disease functionality would be reported as a score of 100) | Posted | Mean | Standard Deviation | score on a scale | 12 months post-operatively |
|
|
|
| Primary | Score for the Knee Society Score (KSS) Function Component at 1 Year Post-operatively | Physician completed Knee Society Score questionnaire used to measure a patient's functional ability before and after total knee arthroplasty (TKA); score range is reported between 0-100 with improvement in outcomes reflected as a higher numerical value (e.g. a 'complete' return to pre-disease functionality would be reported as a score of 100) | Posted | Mean | Standard Deviation | score on a scale | 12 months post-operatively |
|
|
|
| Secondary | Assessing Knee Stability Using the KT-1000 Arthrometer (at 30 Degrees) | Used for grading the stability of the knee in various degrees of flexion according to section 4 of the International Knee Documentation Committee's Knee Ligament Standard Evaluation Form where normal (-1 to 2 mm); nearly normal (3 to 5 mm); abnormal (6 to 10 mm); severely abnormal (>10 mm) | Posted | Mean | Standard Deviation | millimeters | 1 year post-operatively |
|
|
|
| Secondary | Assessing Knee Stability Using the KT-1000 Arthrometer (at 90 Degrees) | Used for grading the stability of the knee in various degrees of flexion according to section 4 of the International Knee Documentation Committee's Knee Ligament Standard Evaluation Form where normal (-1 to 2 mm); nearly normal (3 to 5 mm); abnormal (6 to 10 mm); severely abnormal (>10 mm) | Posted | Mean | Standard Deviation | millimeters | 1 year post-operatively |
|
|
|
| Secondary | Get-up-and-Go Test | Used to assess a person's mobility and requires both static and dynamic balance. It uses the time that a person takes to rise from a chair, walk three metres, turn around, walk back to the chair, and sit down. | Posted | Mean | Standard Deviation | seconds | Between 6 months and 1 year post-operatively |
|
|
|
| 0 |
| 0 |
| 0 |
| 0 |
| 0 |
| EG001 | Medacta PS | Cam-and-post Medacta GMK posterior stabilized prosthesis | 0 | 0 | 0 | 0 | 0 | 0 |
Not provided
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| D012216 |
| Rheumatic Diseases |
| 3 mo. VR-12 MCS |
|
| 6 mo. VR-12 MCS |
|
| 1 yr. VR-12 MCS |
|
| 2 yr. VR-12 MCS |
|
| 3 mo. VR-12 PCS |
|
| 6 mo. VR-12 PCS |
|
| 1 yr. VR-12 PCS |
|
| 2 yr. VR-12 PCS |
|
| 3 mo. PROMIS Physical Function |
|
| 6 mo. PROMIS Physical Function |
|
| 1 yr. PROMIS Physical Function |
|
| 2 yr. PROMIS Physical Function |
|
| 3 mo. PROMIS Pain Interference |
|
| 6 mo. PROMIS Pain Interference |
|
| 1 yr. PROMIS Pain Interference |
|
| 2 yr. PROMIS Pain Interference |
|
| 3 mo. PROMIS Pain Behavior |
|
| 6 mo. PROMIS Pain Behavior |
|
| 1 yr. PROMIS Pain Behavior |
|
| 2 yr. PROMIS Pain Behavior |
|
| 3 mo. IKDC Composite |
|
| 6 mo. IKDC Composite |
|
| 1 yr. IKDC Composite |
|
| 2 yr. IKDC Composite |
|