OsteoarthritisNCT03391323
Medacta GMK Sphere® vs. Medacta GMK PS Post-Market Outcomes Study
A study testing Medacta GMK Sphere® Medial-Pivot Knee Prosthesis and Medacta GMK PS Posterior Stabilized Knee Prosthesis in people with Osteoarthritis and Osteoarthritis, Knee, run by David F. Scott, MD at 1 site in United States.
Trial summary
The study is a prospective, randomized comparison of total knee arthroplasty with the Medacta GMK Sphere® knee compared to the Medacta GMK PS knee, with comparison to data from previous trials of similar study design. Read more about this study
- Who is it for?
- Ages 21 to 80 yearsHealthy volunteers can take part
- Conditions the study is for
- Osteoarthritis, Osteoarthritis, Knee, Joint Disease
- What is being tested?
- Medacta GMK Sphere® Medial-Pivot Knee Prosthesis and Medacta GMK PS Posterior Stabilized Knee Prosthesis
- Type of treatment
- Medical device
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 218 participants
- Where
- 1 siteUnited States
- Study dates
- Apr 2015to 27 Nov 2023
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 21 to 80 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Patients willing to sign the Informed Consent.
- Patients able to comply with follow-up requirements including postoperative weight bearing restrictions and self-evaluations.
- Male and non-pregnant female patients ages 21 - 80 years of age at the time of surgery.
- Patients requiring a primary total knee replacement.
- Patients with a diagnosis of osteoarthritis (OA), traumatic arthritis (TA), or avascular necrosis (AVN).
- Patients with intact collateral ligaments.
Who cannot join
- Patients with inflammatory arthritis.
- Patients that are morbidly obese, body mass index (BMI) > 40.
- Patients with a history of total or unicompartmental reconstruction of the affected joint.
- Patients with neuromuscular or neurosensory deficiency, which would limit the ability to assess the performance of the device.
- Patients with a systemic or metabolic disorder leading to progressive bone deterioration.
- Patients that are immunologically compromised, or receiving chronic steroids (>30 days), excluding inhalers.
Show all 12Show fewer
- Patients bone stock is compromised by disease or infection, which cannot provide adequate support and/or fixation to the prosthesis.
- Patients with knee fusion to the affected joint.
- Patients with an active or suspected latent infection in or about the knee joint.
- Patients whose surgery will utilize computer-assisted surgical navigation (CAOS) techniques.
- Patients whose surgery will utilize minimally invasive surgical techniques.
- Patients that are prisoners.
Trial locations and contacts
1 site in 1 country.
United States1 site
Spokane Joint Replacement Center
Spokane, Washington, 99218
About this study
Official title: Medacta GMK Sphere® Medial-Pivot, Cruciate Substituting vs. Medacta GMK PS Posterior Stabilized Kne vs. OMNI Apex Knee Ultracongruent vs. Triathlon® Posterior Stabilized & Cruciate Substituting Outcomes Study
The study is a prospective, randomized comparison of total knee arthroplasty with the Medacta GMK Sphere® knee compared to the Medacta GMK PS knee, with comparison to data from previous trials of similar study design.
Read the detailed description
There is no consensus within the Arthroplasty community as to whether a traditional post and cam-style PS total knee device is superior to a medial-pivot, more congruent device. However, the majority of surgeons seem to prefer the former, though there is a minority that uses the latter device with great success.
To date, there have been few prospective trials directly comparing these devices, and none with the latest generation of TKA implants. Almost all such studies have been retrospective, and/or non-randomized, and/or utilizing older generation devices.
The primary objective of this study is to compare the average Forgotten Knee Score (FJS) of those patients receiving the Medacta GMK Sphere knee with the average FJS of those receiving the Medacta GMK PS knee at the two and five year time points. It is expected that those subjects implanted with the Medacta GMK Sphere knee will show significantly better Forgotten Joint Scores at two and five year follow-up when compared with those receiving the Medacta GMK PS knee. The FJS was not collected in the prior comparison studies, and so cannot be evaluated across the knee systems.
- Conditions
- Osteoarthritis, Osteoarthritis, Knee, Joint Disease
- Being tested
- Medacta GMK Sphere® Medial-Pivot Knee Prosthesis, Medacta GMK PS Posterior Stabilized Knee Prosthesis
- Medical subject headings
- Osteoarthritis, Osteoarthritis, Knee, Joint Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Medacta GMK Sphere® Medial-Pivot Knee ProsthesisDevice
Medacta GMK PS Posterior Stabilized Knee ProsthesisDevice
| Study group | Role | What they receive |
|---|---|---|
| Medacta GMK Sphere® Medial-Pivot Knee Prosthesis | Other | Research subjects in this arm received GMK Sphere. Receives: Device: Medacta GMK Sphere® Medial-Pivot Knee Prosthesis |
| Medacta GMK PS Posterior Stabilized Knee Prosthesis | Other | Research subjects in this arm received GMK PS. Receives: Device: Medacta GMK PS Posterior Stabilized Knee Prosthesis |
What is being measured
The primary outcome is the main question the study is designed to answer.
Forgotten Joint Score (FJS)
The average Forgotten Joint Score (FJS) of those patients receiving the Medacta GMK Sphere® knee prosthesis will be compared with the average FJS of those receiving the Medacta GMK PS knee prosthesis.
The FJS total score range is 0-100, with higher scores indicating a higher degree of "forgetting" the artificial joint, that is, a lower degree of awareness.
Measured: Change from baseline at 2 years and 5 years post-operative
Secondary outcomes (3)
Total Knee Society Score (KSS)
Clinical outcomes will be evaluated via the Knee Society Score (KSS). The KSS is subdivided into a Knee Assessment score which rates only the knee joint itself, and a Functional Assessment score which rates the subject's ability to walk and climb stairs. Both scores range from 0-100, with a higher score indicating a better outcome.
Measured: Pre-operative, 6 weeks, 6 months, 1, 2, 3, 4, and 5 years post-operative
Lower Extremity Activity Scale (LEAS)
Clinical outcomes will be evaluated via the Lower Extremity Activity Scale (LEAS). The LEAS scale range is 1-18, with a higher value indicating a higher level of activity.
Measured: Pre-operative, 6 weeks, 6 months, 1, 2, 3, 4, and 5 years post-operative
Radiographic Analysis
Radiographs will be assessed for radiolucency, migration and subsidence. An AP Longstanding view will be obtained pre-operatively, and at 6 weeks and 1 year post-operatively to determine degree of Varus or Valgus.
Measured: Pre-operative, 6 weeks, 6 months, 1, 2, 3, 4, and 5 years post-operative
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted5 Jan 2018
- Study startApr 2015
- Primary completion27 Nov 2023
- Study completion27 Nov 2023
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for OsteoarthritisStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 218 participants (actual)
Sponsor and investigators
- Lead sponsor
- David F. Scott, MD
- Sponsor type
- University, hospital or other
- Collaborators
- Medacta USA
- Responsible party
- Sponsor-investigator, David F. Scott, MD, Spokane Joint Replacement Center
- Investigators
- David Scott, MD, Principal investigator, Spokane Joint Replacement Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03391323
- Sponsor's protocol ID
- SJRC-GMK
- Status last verified
- Apr 2026
- First submitted
- 11 Dec 2017
- Last updated
- 29 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- Yes
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 29 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Medacta GMK Sphere® Medial-Pivot, Cruciate Substituting vs. Medacta GMK PS Posterior Stabilized Kne vs. OMNI Apex Knee Ultracongruent vs. Triathlon® Posterior Stabilized & Cruciate Substituting Outcomes Study
- ClinicalTrials.gov ID
- NCT03391323
- Acronym / sponsor ID
- SJRC-GMK
- Conditions
- Osteoarthritis, Osteoarthritis, Knee, Joint Disease
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 218 participants (actual)
- Lead sponsor
- David F. Scott, MDUniversity, hospital or other
- Collaborators
- Medacta USA
- Study start
- Apr 2015 (actual)
- Primary completion
- 27 Nov 2023 (actual)
- Study completion
- 27 Nov 2023 (actual)
- First posted
- 5 Jan 2018 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The study is a prospective, randomized comparison of total knee arthroplasty with the Medacta GMK Sphere® knee compared to the Medacta GMK PS knee, with comparison to data from previous trials of similar study design.
Detailed description
There is no consensus within the Arthroplasty community as to whether a traditional post and cam-style PS total knee device is superior to a medial-pivot, more congruent device. However, the majority of surgeons seem to prefer the former, though there is a minority that uses the latter device with great success.
To date, there have been few prospective trials directly comparing these devices, and none with the latest generation of TKA implants. Almost all such studies have been retrospective, and/or non-randomized, and/or utilizing older generation devices.
The primary objective of this study is to compare the average Forgotten Knee Score (FJS) of those patients receiving the Medacta GMK Sphere knee with the average FJS of those receiving the Medacta GMK PS knee at the two and five year time points. It is expected that those subjects implanted with the Medacta GMK Sphere knee will show significantly better Forgotten Joint Scores at two and five year follow-up when compared with those receiving the Medacta GMK PS knee. The FJS was not collected in the prior comparison studies, and so cannot be evaluated across the knee systems.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (participant)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Medacta GMK Sphere® Medial-Pivot Knee Prosthesis | Other | Device: Medacta GMK Sphere® Medial-Pivot Knee ProsthesisResearch subjects in this arm received GMK Sphere. |
| Medacta GMK PS Posterior Stabilized Knee Prosthesis | Other | Device: Medacta GMK PS Posterior Stabilized Knee ProsthesisResearch subjects in this arm received GMK PS. |
Who may qualify
- Ages
- 21 to 80 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- Patients willing to sign the Informed Consent.
- Patients able to comply with follow-up requirements including postoperative weight bearing restrictions and self-evaluations.
- Male and non-pregnant female patients ages 21 - 80 years of age at the time of surgery.
- Patients requiring a primary total knee replacement.
- Patients with a diagnosis of osteoarthritis (OA), traumatic arthritis (TA), or avascular necrosis (AVN).
Key exclusion criteria (12 listed)
- Patients with inflammatory arthritis.
- Patients that are morbidly obese, body mass index (BMI) > 40.
- Patients with a history of total or unicompartmental reconstruction of the affected joint.
- Patients with neuromuscular or neurosensory deficiency, which would limit the ability to assess the performance of the device.
- Patients with a systemic or metabolic disorder leading to progressive bone deterioration.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Medacta GMK Sphere® Medial-Pivot Knee Prosthesis | Device | Medacta GMK Sphere® Medial-Pivot Knee Prosthesis |
| Medacta GMK PS Posterior Stabilized Knee Prosthesis | Device | Medacta GMK PS Posterior Stabilized Knee Prosthesis |
Primary outcome
Forgotten Joint Score (FJS)
Time frame: Change from baseline at 2 years and 5 years post-operative
The average Forgotten Joint Score (FJS) of those patients receiving the Medacta GMK Sphere® knee prosthesis will be compared with the average FJS of those receiving the Medacta GMK PS knee prosthesis. The FJS total score range is 0-100, with higher scores indicating a higher degree of "forgetting" the artificial joint, that is, a lower degree of awareness.
3 secondary outcomes
Total Knee Society Score (KSS)
Time frame: Pre-operative, 6 weeks, 6 months, 1, 2, 3, 4, and 5 years post-operative
Lower Extremity Activity Scale (LEAS)
Time frame: Pre-operative, 6 weeks, 6 months, 1, 2, 3, 4, and 5 years post-operative
Radiographic Analysis
Time frame: Pre-operative, 6 weeks, 6 months, 1, 2, 3, 4, and 5 years post-operative
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Apr 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
David Scott, MD principal investigator
Spokane Joint Replacement Center
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Medacta GMK Sphere® Medial-Pivot Knee Prosthesis and Medacta GMK PS Posterior Stabilized Knee Prosthesis in people with Osteoarthritis and Osteoarthritis, Knee, run by David F. Scott, MD at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 12 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 29 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Forgotten Joint Score (FJS) (time frame: Change from baseline at 2 years and 5 years post-operative). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 29 Apr 2026.