Functionally Aligned vs Mechanical Axis Aligned Total Knee Arthroplasty (FATKAvsMATKA)

A Prospective Randomised Control Trial Comparing the Effect of Functional Alignment With Mechanical Axis Alignment on Outcomes After Total Knee Arthroplasty.

The objective of this study is to compare clinical and radiological outcomes in robotic-arm assisted TKA using mechanical alignment (MA TKA) versus robotic-arm assisted TKA with functional alignment (FA TKA).

These outcomes will be used to determine if patient recovery is better with functionally aligned Mako robotic-assisted total knee arthroplasty (FA TKA) or mechanically aligned Mako robotic-assisted total knee arthroplasty (MA TKA).

Study Overview

• Status: Completed
• Conditions: Osteoarthritis; Osteo Arthritis Knee
• Intervention / Treatment: Procedure: Functionally Aligned Total Knee Arthroplasty; Procedure: Mechanically Aligned Total Knee Arthroplasty

Detailed Description

This project is being conducted by Perth Hip and Knee Clinic. The objective of this study is to compare clinical and radiological outcomes in robotic-arm assisted TKA using mechanical alignment (MA TKA) versus robotic-arm assisted TKA with functional alignment (FA TKA). Both FA TKA and MA TKA are performed through similar skin incisions, robotic-guidance, and use identical implants. In MA TKA, bone is prepared and implants positioned to ensure that the overall alignment of the leg is in neutral. In FA TKA, the bone is prepared and implants positioned to restore the natural alignment of the patient's leg. Both of these surgical techniques provide excellent outcomes in TKA but it is not known which of the two techniques is better for patient recovery. Mako robotic-assisted TKA is an established treatment for arthritis of the knee joint. The positions of the implants and overall alignment of the leg are important as they influence how quickly the implants wear out and need replacing. The aim of this study is to determine if patient recovery is better with functionally aligned Mako robotic-assisted total knee arthroplasty (FA TKA) or mechanically aligned Mako robotic-assisted total knee arthroplasty (MA TKA).

• Study Type: Interventional
• Enrollment (Actual): 100
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Australia
  • Western Australia
    • Subiaco, Western Australia, Australia, 6008
      • Perth Hip and Knee
    • Subiaco, Western Australia, Australia, 6008
      • St John of God Private Hopsital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 45 years to 75 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Patient has symptomatic knee osteoarthritis requiring primary TKA
• Patient and surgeon are in agreement that TKA is the most appropriate treatment
• Patient is fit for surgical intervention following review by surgeon
• Patient is between 45-75 years of age at time of surgery, computer literate, and able to complete patient-reported outcome measures independently.
• Patient must be capable of giving informed consent and agree to comply with the postoperative review program.
• Patient must be a permanent resident in an area accessible to the study site
• Patient must have sufficient postoperative mobility to attend follow-up clinics and allow for radiographs to be taken
• Patient has tried non-pharmacologic therapies including: patient education, self-management programs, aerobic exercise, weight loss, physiotherapy and occupational therapy
• Patient has tried appropriate pharmacologic therapies including: regular paracetamol and NSAIDS if appropriate

Exclusion Criteria:

• Patient is not suitable for routine primary TKA. E.g., patient has ligament deficiency that requires a constrained prosthesis
• Interoperative requirement for a more constrained implant.
• Intraoperative requirement for the Posterior Cruciate Ligament to be released. These patients will be still included in the study, but analyzed with an intention-to-treat principle.
• Patient has bone loss that requires augmentation
• Patient requires revision surgery following previously failed correctional osteotomy or ipsilateral TKA (e.g., post-high tibial or distal femoral osteotomy)
• Patient requires a polyethylene inset of 13mm or greater.
• Patient is immobile or has another neurological condition affecting musculoskeletal function
• Patient is less than 44 years of age or greater than 76 years of age
• Patient is a compensable patient. I.e., Worker's compensation claim or motor vehicle accident.
• Patient is already enrolled in another concurrent clinical trial
• Patient is unable or unwilling to sign the informed consent form specific to this study
• Patient is unable to attend the follow-up program
• Patient is non-resident in local area or expected to leave the catchment area postoperatively
• Patients who lacks capacity to provide consent, or the ability to understand the study protocol due to a cognitive condition (e.g., Dementia)
• Patient is unable to communicate effectively in English.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Functionally aligned Total Knee Arthroplasty; Knee arthroplasty performed using a functional alignment theory	Procedure: Functionally Aligned Total Knee Arthroplasty; Femoral + tibial osteotomy planned for equal resection of femoral condyles to replicate patient anatomy. In coronal plane, distal femoral resection of 6.5mm subchondral bone from medial + lateral condyles, adjusted 1-3mm for compensation of wear. Proximal tibia, 7mm resection from subchondral bone from medial + lateral tibial plateau. Sagittal plane, resection angle determined intraoperatively to closely match native femoral flexion + tibial slope. Axial plane: posterior femoral resection 6.5mm from the subchondral bone of medial and lateral posterior condyles. Tibial rotation aligned to Akagi's line. Adjustments will be made to bony alignment to balance soft tissues within boundaries of 6° varus/3° valgus HKA alignment. Femoral component alignment limited to 6° valgus/3° varus in coronal plane. Tibial alignment limited 6° varus/3° valgus in coronal plane. Combined flexion of components limited to 10° flexion. Soft tissue release if balance within boundaries not achieved.
Active Comparator: Mechanical axis aligned Total Knee Arthroplasty; Knee arthroplasty performed using a mechanical alignment theory	Procedure: Mechanically Aligned Total Knee Arthroplasty; Tibial and femoral osteotomies in the coronal plane will be planned perpendicular to the tibial and femoral mechanical axes respectively to achieve neutral overall alignment. Soft tissue balance will be assessed and minor adjustments to bony alignment made to balance the knees with a maximal adjustment of two degrees valgus and two degrees varus of coronal alignment from neutral. Femoral rotation will be planned to surgical epicondylar axis and adjustments to rotation made to allow equal flexion and extension balance (to within 1mm). If balance can not be achieved within these boundaries then soft tissue release will be undertaken. In the sagittal plane, 0-3° degrees of posterior tibial slope and 0-5° of femoral component flexion will be used to optimise implant sizing whilst preventing notching. In the axial plane, the tibial component aligned to Akagi's line, which connects the medial border of the patellar tendon attachment to the middle of the posterior cruciate ligament.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Forgotten Joint Score After 2 Years From Baseline	Difference in relative change in Forgotten Joint Score (2 years post-operatively compared to preoperatively) between FA and MA patients. Scale 0-100 with higher scores being a better outcome	Preoperatively and 2 years postoperatively
Change in Oxford Knee Score After 2 Years From Baseline	Difference in relative change in Oxford Knee Score (2 years post-operatively compared to preoperatively) between FA and MA patients. Scale 0-48 with higher scores being a better outcome.	Preoperatively and 2 years postoperatively
Change in Range of Motion After 2 Years From Baseline	Difference in relative change in range of motion via goniometry (2 years post-operatively compared to preoperatively) between FA and MA patients.	Preoperatively and 2 years postoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Determine Lower Limb Alignment Achieved With Both Alignment Techniques	Lower limb alignment as assessed using standing long leg x-rays performed postoperatively at 3 months. Measurements of the hip-knee-angle (HKA), medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA). Also evidence of imbalance with implant lift off will be measured.	3 Months post-operatively
Difference in Analgesia Requirements Between Patients in Alignment Groups	Determine if there are any differences in analgesic requirements based on alignment method used. Inpatient medical records will be utilised to obtain analgesia requirements as inpatient Questionnaires will be used to obtain analgesia usage at remaining timepoints. Analgesia usage will be converted to morphine equivalent dosages for comparison	6 weeks, 3 months, 1 year, 2 years
Difference in Sagittal Stability of the Knee Post Replacement	Determine whether alignment method utilized has an effect on the sagittal stability of the knee post replacement, as measure with an arthrometer "Lachmeter"	Preop, and post-operatively at 3 months, 1 year and 2 years
Difference in Functional Outcomes (Measured as Maximal Voluntary Contraction) of Knee Flexion and Extension Between Alignment Groups	Determine whether alignment method utilized has an effect on functional outcomes. Measured as Maximal voluntary isometric knee flexion and extension forces as measured via hand-held dynamometry.	Preop, 3 months, 1 Year and 2 years
Intra-operative Balance Achieved With Different Alignment Techniques.	Surgeon blinded measurement of intraoperative balance achieved with Verasense sensor (smaller cohort) Secondary outcome [6] To determine if there is a difference in knee kinematics between the two techniques. Measurement of knee kinematics with Verasense sensor to assess presence or absence of medial pivot (smaller cohort)	Intraoperatively
Difference in Clinical Outcomes as Measured in Knee Injury and Osteoarthritis Outcome Score for Joint Replacement Score (KoosJR)	Difference in operated knee outcome on Koos JR scale between FA and MA patients. Scale 0-100 where higher scores mean better outcome.	Measured Pre-operatively and at 3 month, 1 year and 2 years post operatively.
Difference in Clinical Outcomes as Measured in European Quality of Life Questionnaire With 5 Dimensions for Adults (EQ-5D-5L).	Difference in overall by Visual Analogue Scale for overall health (VAS). Scale: Five dimensions combined into a 5-digit number lower numbers represent better outcomes. Addition of overall health VAS Scale 0-100 with higher score being better outcome.	Measured Pre-operatively and at 3 month, 1 year and 2 years post operatively.
Difference in Operated Knee Pain as Measured by Visual Analogue Scale for Pain (VAS)	Difference in operated knee pain as measured by Visual Analogue Scale for pain (VAS). Scale 0-100 with higher scores meaning worse outcome.	Measured Pre-operatively and at 3 month, 1 year and 2 years post operatively.
Difference in Clinical Outcomes as Measured by Kujala Score- a Measure of Anterior Knee Pain and Best Clinical Score for Patellofemoral Function	Difference in clinical outcomes as measured by Kujala score between FA and MA patients. Scale 0-100, with higher scores indicating better outcome.	Measured Pre-operatively and at 3 month, 1 year and 2 years post operatively.

Collaborators and Investigators

• Sponsor: Perth Hip and Knee
• Collaborators: St John of God Private Hospital Subiaco
• Investigators: Principal Investigator: Gavin Clark, Principal Investigator

Publications and helpful links

General Publications

• Steer R, Tippett B, Khan RN, Collopy D, Clark G. A prospective randomised control trial comparing functional with mechanical axis alignment in total knee arthroplasty: study protocol for an investigator initiated trial. Trials. 2021 Aug 9;22(1):523. doi: 10.1186/s13063-021-05433-z.

Study record dates

Study Major Dates

• Study Start (Actual): April 30, 2021
• Primary Completion (Actual): October 8, 2024
• Study Completion (Actual): November 14, 2024

Study Registration Dates

• First Submitted: February 4, 2021
• First Submitted That Met QC Criteria: February 8, 2021
• First Posted (Actual): February 10, 2021

Study Record Updates

• Last Update Posted (Actual): August 8, 2025
• Last Update Submitted That Met QC Criteria: July 22, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Keywords: Arthritis; Osteoarthritis; Knee; OA
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Joint Diseases; Rheumatic Diseases; Arthritis; Osteoarthritis; Osteoarthritis, Knee
• Other Study ID Numbers: ACTRN12621000060842

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Not shared - for confidentiality of participants

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No