Trial Outcomes & Findings for Functionally Aligned vs Mechanical Axis Aligned Total Knee Arthroplasty (NCT NCT04748510)

NCT ID: NCT04748510

Last Updated: 2025-08-08

Results Overview

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

• Recruitment status: COMPLETED
• Study phase: NA
• Target enrollment: 100 participants
• Primary outcome timeframe: Preoperatively and 2 years postoperatively
• Results posted on: 2025-08-08

Participant Flow

Participant milestones

Measure	Functionally Aligned Total Knee Arthroplasty Knee arthroplasty performed using a functional alignment theory 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.	Mechanical Axis Aligned Total Knee Arthroplasty Knee arthroplasty performed using a mechanical alignment theory 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.
Overall Study STARTED	50	50
Overall Study COMPLETED	48	44
Overall Study NOT COMPLETED	2	6

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

Race and Ethnicity were not collected from any participant.

Baseline characteristics by cohort

Measure	Functionally Aligned Total Knee Arthroplasty n=50 Participants Knee arthroplasty performed using a functional alignment theory 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.	Mechanical Axis Aligned Total Knee Arthroplasty n=49 Participants Knee arthroplasty performed using a mechanical alignment theory 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.	Total n=99 Participants Total of all reporting groups
Age, Continuous	65 years STANDARD_DEVIATION 6.2 • n=50 Participants	65.4 years STANDARD_DEVIATION 7.3 • n=49 Participants	65.2 years STANDARD_DEVIATION 6.8 • n=99 Participants
Sex: Female, Male Female	28 Participants n=50 Participants	24 Participants n=49 Participants	52 Participants n=99 Participants
Sex: Female, Male Male	22 Participants n=50 Participants	25 Participants n=49 Participants	47 Participants n=99 Participants
Race and Ethnicity Not Collected	—	—	0 Participants Race and Ethnicity were not collected from any participant.
BMI	31.3 kg/m^2 STANDARD_DEVIATION 6.4 • n=50 Participants	31.0 kg/m^2 STANDARD_DEVIATION 5.2 • n=49 Participants	31.2 kg/m^2 STANDARD_DEVIATION 5.8 • n=99 Participants

PRIMARY outcome

Timeframe: Preoperatively and 2 years postoperatively

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

Outcome measures

Measure	Functionally Aligned Total Knee Arthroplasty n=48 Participants Knee arthroplasty performed using a functional alignment theory 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.	Mechanical Axis Aligned Total Knee Arthroplasty n=44 Participants Knee arthroplasty performed using a mechanical alignment theory 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.
Change in Forgotten Joint Score After 2 Years From Baseline	50.1 score on a scale Standard Deviation 28.3	46.4 score on a scale Standard Deviation 32.4

PRIMARY outcome

Timeframe: Preoperatively and 2 years postoperatively

Population: 11 patients did not provide responses for this outcome measure, resulting in missing scores. Some of these participants did complete other study questionnaires but were lost to follow-up for this specific assessment.

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.

Outcome measures

Measure	Functionally Aligned Total Knee Arthroplasty n=45 Participants Knee arthroplasty performed using a functional alignment theory 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.	Mechanical Axis Aligned Total Knee Arthroplasty n=43 Participants Knee arthroplasty performed using a mechanical alignment theory 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.
Change in Oxford Knee Score After 2 Years From Baseline	17.0 score on a scale Standard Deviation 7.5	17.2 score on a scale Standard Deviation 8.6

PRIMARY outcome

Timeframe: Preoperatively and 2 years postoperatively

Population: 18 participants were lost to in-person clinical follow-up, resulting in missing range-of-motion scores. Reasons for loss to follow-up included cancer diagnosis, relocation outside the Perth metropolitan area, appointment cancellations or refusals, and inability to contact the participants. However, some of these individuals completed the study questionnaires and were lost to follow-up only for the range-of-motion assessment.

Difference in relative change in range of motion via goniometry (2 years post-operatively compared to preoperatively) between FA and MA patients.

Outcome measures

Measure	Functionally Aligned Total Knee Arthroplasty n=40 Participants Knee arthroplasty performed using a functional alignment theory 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.	Mechanical Axis Aligned Total Knee Arthroplasty n=41 Participants Knee arthroplasty performed using a mechanical alignment theory 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.
Change in Range of Motion After 2 Years From Baseline	2.8 deg Standard Deviation 9.9	2.8 deg Standard Deviation 9.3

SECONDARY outcome

Timeframe: 3 Months post-operatively

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.

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: 6 weeks, 3 months, 1 year, 2 years

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

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: Preop, and post-operatively at 3 months, 1 year and 2 years

Determine whether alignment method utilized has an effect on the sagittal stability of the knee post replacement, as measure with an arthrometer "Lachmeter"

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: Preop, 3 months, 1 Year and 2 years

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.

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: Intraoperatively

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)

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: Measured Pre-operatively and at 3 month, 1 year and 2 years post operatively.

Difference in operated knee outcome on Koos JR scale between FA and MA patients. Scale 0-100 where higher scores mean better outcome.

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: Measured Pre-operatively and at 3 month, 1 year and 2 years post operatively.

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.

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: 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). Scale 0-100 with higher scores meaning worse outcome.

Outcome measures

Outcome data not reported

SECONDARY outcome

Timeframe: Measured Pre-operatively and at 3 month, 1 year and 2 years post operatively.

Difference in clinical outcomes as measured by Kujala score between FA and MA patients. Scale 0-100, with higher scores indicating better outcome.

Outcome measures

Outcome data not reported

Adverse Events

Functionally Aligned Total Knee Arthroplasty

Serious events: 1 serious events

Other events: 0 other events

Deaths: 0 deaths

Mechanical Axis Aligned Total Knee Arthroplasty

Serious events: 1 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Measure	Functionally Aligned Total Knee Arthroplasty n=50 participants at risk Knee arthroplasty performed using a functional alignment theory 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.	Mechanical Axis Aligned Total Knee Arthroplasty n=49 participants at risk Knee arthroplasty performed using a mechanical alignment theory 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.
Injury, poisoning and procedural complications MUA	0.00% 0/50 • Adverse events were monitored for each participant from the time of enrolment (baseline) through to their final study visit (2 years post-operative). Both methods of knee alignment are already being performed as standard of care for both surgeons. There are no additional risks to the patient stemming from either trial intervention, apart from routine risk of surgery.	2.0% 1/49 • Number of events 1 • Adverse events were monitored for each participant from the time of enrolment (baseline) through to their final study visit (2 years post-operative). Both methods of knee alignment are already being performed as standard of care for both surgeons. There are no additional risks to the patient stemming from either trial intervention, apart from routine risk of surgery.
Cardiac disorders Paroxsymal SVT post operative	2.0% 1/50 • Number of events 1 • Adverse events were monitored for each participant from the time of enrolment (baseline) through to their final study visit (2 years post-operative). Both methods of knee alignment are already being performed as standard of care for both surgeons. There are no additional risks to the patient stemming from either trial intervention, apart from routine risk of surgery.	0.00% 0/49 • Adverse events were monitored for each participant from the time of enrolment (baseline) through to their final study visit (2 years post-operative). Both methods of knee alignment are already being performed as standard of care for both surgeons. There are no additional risks to the patient stemming from either trial intervention, apart from routine risk of surgery.

Other adverse events

Adverse event data not reported

Additional Information

Dr Serene Lee, Orthopaedic Research Officer

Perth Hip & Knee

Phone: 64891720

Email: research@hipnknee.com.au

Results disclosure agreements

• Principal investigator is a sponsor employee
• Publication restrictions are in place