Functionally Aligned vs Mechanical Axis Aligned Total Knee Arthroplasty

NCT04748510 | Completed Results DMC

• 1 other identifier: ACTRN12621000060842
• Study Type: interventional
• Target: 100
• Locations: 1 country
• Sites: 2

Brief Summary

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).

Conditions

Osteoarthritis; Osteo Arthritis Knee

Keywords

OA; Arthritis; Knee; Osteoarthritis

Outcome Measures

Primary Outcomes (3)

• 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 Outcomes (9)

• Determine Lower Limb Alignment Achieved With Both Alignment Techniques

  3 Months post-operatively

• Difference in Analgesia Requirements Between Patients in Alignment Groups

  6 weeks, 3 months, 1 year, 2 years

• Difference in Sagittal Stability of the Knee Post Replacement

  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

  Preop, 3 months, 1 Year and 2 years

• Intra-operative Balance Achieved With Different Alignment Techniques.

  Intraoperatively

Study Arms (2)

Functionally aligned Total Knee Arthroplasty

ACTIVE COMPARATOR

Knee arthroplasty performed using a functional alignment theory

Procedure: Functionally Aligned Total Knee Arthroplasty

Mechanical axis aligned Total Knee Arthroplasty

ACTIVE COMPARATOR

Knee arthroplasty performed using a mechanical alignment theory

Procedure: Mechanically Aligned Total Knee Arthroplasty

Interventions

Functionally Aligned Total Knee Arthroplasty PROCEDURE

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.

Functionally aligned Total Knee Arthroplasty

Mechanically Aligned Total Knee Arthroplasty PROCEDURE

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.

Mechanical axis aligned Total Knee Arthroplasty

Eligibility Criteria

• Age: 45 Years - 75 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• 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

You may not qualify if:

• 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.

Sponsors & Collaborators

• Perth Hip and Knee: lead
• St John of God Private Hospital Subiaco: collaborator

Study Sites (2)

Perth Hip and Knee

Subiaco, Western Australia, 6008, Australia

Location

St John of God Private Hopsital

Subiaco, Western Australia, 6008, Australia

Location

Related Publications (1)

• 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.

  PMID: 34372888 DERIVED

MeSH Terms

Conditions

Osteoarthritis; Arthritis

Condition Hierarchy (Ancestors)

Joint Diseases; Musculoskeletal Diseases; Rheumatic Diseases

Results Point of Contact

• Title: Dr Serene Lee, Orthopaedic Research Officer
• Organization: Perth Hip & Knee

research@hipnknee.com.au

64891720

Study Officials

• Gavin Clark

  Principal Investigator

  PRINCIPAL INVESTIGATOR

Publication Agreements

• PI is Sponsor Employee: Yes
• Restrictive Agreement: No

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal investigator

Study Record Dates

• First Submitted: February 4, 2021
• First Posted: February 10, 2021
• Study Start: April 30, 2021
• Primary Completion: October 8, 2024
• Study Completion: November 14, 2024
• Last Updated: August 8, 2025
• Results First Posted: August 8, 2025

Record last verified: 2025-07

Data Sharing

• IPD Sharing: Will not share

Locations

AU (2)