None listed
Conditions
Brief summary
Total knee arthroplasty (TKA) is regarded as a successful surgical procedure that alleviates the morbidity associated with end-stage osteoarthritis (OA). Despite this, around 15-20% of people are dissatisfied with their result and surgeons are striving to understand the reasons why. One thought is that the more traditional, mechanical alignment (MA) principle, changes the natural joint kinematics by altering the joint line obliquity and altering its rotational axes. Implanting a prosthesis in this manner may place undue stress on the soft tissue causing pain and dysfunction. More recently, surgeons have strived to attain a more natural alignment to respect an individual’s joint obliquity and rotational axes so that the soft tissue envelope and surrounding musculature is not at odds with the implanted prosthesis hereby, reducing the kinematic conflict. This philosophy is referred to by knee arthroplasty surgeons as kinematic alignment (KA). Great interest in the kinematic doctrine has been prompted by a handful of level 1 trials with some demonstrating promising results. Ten randomised control trials (RCT) comparing MA with KA in unconstrained prostheses of which five showed a mild improvement in mid-term functional outcomes and five demonstrated no difference. In the period 2017 to 2019, four systematic reviews and meta-analyses have reported comparable functional outcomes in the medium follow-up. Implant design is also implicated in trying to recreate a more natural knee kinematics. The medial pivot (MP) design attempts to mimic natural medial pivot and lateral femoral rollback during flexion that has been observed in the native, non arthritic knee. On the medial side the implant is a ball and socket design, whereas the lateral compartment is relatively flat allowing the femur to slide posteriorly during flexion. To date, only one non randomised trial has investigated a medial pivot prosthesis in the setting of KA principles demonstrating superior function compared to a cruciate retaining TKA at 2 years. We hypothesised that combining a medial pivot design implant with the principle of KA may improve patient functional outcomes. This study aims to 1) compare medium term functional outcomes between mechanically and kinematically aligned TKA when using a MP prosthesis, and 2) evaluate TKA kinematics when a medial pivot designed prosthesis is used for both alignment principles and how these might compare with the native, non arthritic knee
Interventions
Patients will receive their total knee replacement according to kinematic alignment principles. A CT scan 3-4 weeks prior to surgery will be used to manufacture patient specific guides. These guides are positioned on the patients' femurs and tibias to make bone resections according to KA. The control group will also have a CT scan to manufacture their PSI.
Kinematic principles position the knee replacement in a way that respects the natural joint line and rotational axis of the knee. Each surger
Patients will receive their total knee replacement according to kinematic alignment principles. A CT scan 3-4 weeks prior to surgery will be used to manufacture patient specific guides. These guides are positioned on the patients' femurs and tibias to make bone resections according to KA. The control group will also have a CT scan to manufacture their PSI. Kinematic principles position the knee replacement in a way that respects the natural joint line and rotational axis of the knee. Each surgery will take approximately 2 hours. No difference between groups is expected as both use patient specific instrumentation to determine bone cuts for the femur and the tibia. The surgeons performing the surgeries have a minimum of 6 and 20 years of experience as orthopaedic consultants. To monitor compliance/fidelity to the protocol of each group's alignment principles, the amount of bone resection from the tibia and femur will be measured using a validated caliper, recorded and cross checked with the 'expected' bone resections. This is the standard method for checking resections using this particular implant.
Sponsors
Whangarei Hospital
Study design
Allocation
Randomised controlled trial
Intervention model
Parallel
Primary purpose
Treatment
Masking
Blinded (masking used) (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
45 Years to No maximum
Healthy volunteers
No
Inclusion criteria
Patients with end-stage osteoarthritis (Kellgren-Lawrence grade 3 or 4) deemed suitable for total knee arthroplasty and have exhausted non operative management
Exclusion criteria
Coronal > 15 degrees and sagittal deformity of >20 degrees Mechanical lateral distal femur angle of 85-95 degrees and mechanical medial proximal tibia angles of 85-95 degrees Patients who had previous open knee surgery that involved infection, osteotomy or fracture fixation Patients with significant concomitant hip or spinal pathology making functional assessment of the knee replacement inaccurate Contralateral knee pathology Patients unable to complete or understand patient reported outcome assessment BMI > 40kg/m2 History of previous knee infection Patients with neurological disease or neurosensory deficiency inflammatory arthritis
Outcome results
None listed