Plain English Summary
Background and study aims
Osteoarthritis of the knee is a common condition that affects ~25% of the population over the age of 50. It occurs when there is damage to the knee joints that the body isnt able to repair. The exact cause is not known, but there are a number of factors thought to increase the risk of developing the condition. Symptoms include pain while walking (particularly when climbing the stairs or walking uphill), knees giving way or difficulties in straightening the legs. The most common treatment option for osteoarthritis of the knee is a knee replacement. There are currently two main forms of knee replacement used, total knee replacement and unicompartmental knee replacement (used when only one side of the knee joint is damaged). Total knee replacement involves replacing both sides of the knee joint with metal implants separated by a plastic spacer or bearing. Unicompartmental knee replacement involves replacing only the side of the knee joint that is damaged, with smaller metal implants used to replace that side. Total knee replacement successfully provides pain relief in around 80% of cases, but the knee joint never feels normal and patients often find that they cant do more physically demanding activities. Several studies have shown that 10-20% of patients are dissatisfied with the results of their total knee replacement surgery. In comparison, patients who undergo unicompartmental knee replacement surgery tend to have more normal walking patterns and a more normal feeling knee with better function than if they had had a total knee replacement. However, it is estimated that only 25% of patients have osteoarthritis on only one side of the knee and are therefore eligible for the surgery and, as its a complex procedure, many surgeons do not offer it as an option. Recently robotic assistive technology has been introduced to help surgeons perform unicompartmental knee replacement. The team at Glasgow Royal Infirmary have used this technology and found that implants are placed more accurately using it and that patients recover from surgery faster and, at least initially, have better outcomes. A natural extension of the unicompartmental knee replacement technique would be to use two unicompartmental knee replacements implanted at the same time on either side of the same knee joint this is called bi-unicompartmental knee replacement. This technique would allow surgeons to leave knee ligaments intact and replace only the damaged parts of the joint rather than removing the whole knee joint as occurs with total knee replacement. We believe that this surgical option would allow patients to walk more normally (a normal gait) and give them a significantly more normal feeling and acting knee than with a conventional total knee replacement. The purpose of the study is to determine if robotically assisted bi-unicompartmental knee replacement allows patients to walk with a more normal gait than is achieved with a traditional total knee replacement.
Who can participate?
Patients that have osteoarthritis on both sides of the knee but have intact knee ligaments.
What does the study involve?
Patents are randomly placed into one of two groups. Those in group one undergo standard total knee replacement surgery while those in group two undergo robotically assisted bi-unicompartmental knee replacement. The progress of each patient will then be followed up after 3 months, and then after 1, 2, 5 and, finally, ten years, after surgery.
What are the possible benefits and risks of participating?
Robotic assisted bi-unicompartmental knee replacement is a new technique and only around 20 cases have been undertaken using this technology worldwide. We therefore cannot tell how well this surgery will perform in the long term. The most significant risks for patients undergoing knee replacement surgery are infection within the new joint and in the longer term wearing out of the implant. We do not think that the risk of infection will be any higher for patients who receive robotic assisted bi-unicompartmental knee replacement. We cannot predict how long robotic bi-unicompartmental knee replacement knee implants will last as the technique is too new. In addition, patients that take part in this study will have at least one CT scan of their knee (some patients will have two CT scans). This will involve additional exposure to X-rays.
Where is the study run from?
Glasgow Royal Infirmary, Scotland, UK
When is the study starting and how long is it expected to run for?
August 2014 to August 2027
Who is funding the study?
Medical Research Council (UK)
Who is the main contact?
Dr Iain Anthony
Dr James Doonan (added 04/10/2019)
Mr Mark Blyth
Orthopaedic Research Unit
Glasgow Royal Infirmary
Dr James Doonan
Glasgow Royal Infirmary
82 Castle street
1.1 18th Sept 2013
Explanatory comparative study of conventional total knee arthroplasty versus robotic assisted bi-unicompartmental knee arthroplasty
We hypothesise that robotic assisted Bi-UCKA surgery undertaken in appropriately selected patients can offer improved knee kinematics and proprioception in comparison to that afforded by TKA. Furthermore we hypothesise that accurate positioning of implants by robotic assistive technology will improve implant survivorship in Bi-UCKA to the levels achieved with TKA and UKA.
West of Scotland Research Ethics Committee 4 approval pending
Randomised Controlled Trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Not available in web format, please use the contact details below to request a patient information sheet
Osteoarthritis of the knee
Patients will be randomised to receive either a standard total knee replacement or a robotically assisted bi-unicompartmental knee replacement. Randomisation will be via an online web interface and we will stratify by surgeon. Follow- will occur over a 10 year period at the following intervals (3 months, 1,2,5 and 10 years).
Primary outcome measure
Percentage of patients with a bi-phasic (normal) moment curve during gait (level walking) measured at 1 year.
Secondary outcome measures
1. Biomechanical performance: Gait during stair climb/descent and lunge, functional activity assessment (using electrogoniometers) at 1 year
2. Activity: Overall daily activity levels, maximum sport/physical activity, functional activity test times (stair climb, timed up and go) 1,2,5 and 10 years
3. Impairment: Range of motion, proprioception, quadriceps strength (short term outcome) and progression of OA in contralateral knee (long term outcome) at 1,2,5 and 10 years
4. Clinical Outcomes: Clinical knee scores (Oxford Knee Score and American Knee Society Score), pain, analgesic use, complications, implant fixation and satisfaction at 1,2,5 and 10 years
5. Safety profile: Determined by revision rate, adverse events, robotic system errors and accuracy of implantation at 1,2,5 and 10 years
6. Accuracy of surgical implantation, determined by post-op CT analysis, at 1 year
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Patients with medial and lateral compartment osteoarthritis of the knee with intact cruciate ligaments
2. Patients willing and able to give informed consent
Target number of participants
Participant exclusion criteria
1. Patients with osteoarthritis limited to one compartment of the knee
2. Patients with rheumatoid arthritis
3. Patients with medial or lateral subluxation of the tibia on the femur
4. Patients with a varus or valgus deformity greater than 15º
5. Patients with a flexion contracture greater than 10º
6. Patients with rupture of either the ACL or PCL
7. Active or recent local infection
8. Patello-femoral OA greater than Kellgren and Lawrence grade III
9. Patients who have had previous surgery to the knee which may impact on the outcome of TKA or bi-unicompartmental knee arthroplasty
10. Patients with significant disease in other joints which might impact on their gait
11. Patients unable to give informed consent
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Orthopaedic Research Unit
Medical Research Council (MRC) (UK) MRC EME (12/12/12)
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Planned publication in a high-impact peer-reviewed journal
Intention to publish date
Participant level data
Not provided at time of registration
Basic results (scientific)