Robotic Assisted Surgery Comparing Personalized Alignment Versus Mechanical Alignment of Total Knee Arthroplasty - A Randomized Controlled Trial
Phase: NA
Conditions: Knee Osteoarthritis
Sponsor: Helse Møre og Romsdal HF

Frank-David Øhrn                                                                                                             the personalKNEE Trial                              
 
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Robotic assisted surgery comparing personalized alignment versus 
mechanical alignment of total knee arthroplasty – A randomized 
controlled trial 
 
the personalKNEE Trial 
 
Protocol author Frank-David Øhrn 2024-03-14 
 
 
 
Co-authors in random order  
XXXXX (unknown PhD candidate) 1 Tommy Frøseth Aae (MD, PhD) 1,2 Øystein Bjerkestrand 
Lian (MD, PhD) 1, 2 Otto Schnell Husby (MD, PhD) 1, 2 Kirsti Sevaldsen 1,2,  Stephan Maximillian 
Röhrl (MD, PhD) 3, 4 Frank-David Øhrn (MD, PhD) 1,2  
 
1Møre and Romsdal Hospital Trust, Kristiansund Hospital, Norway  
2Department of Neuromedicine and Movement Science, NTNU Norwegian University of 
Science and Technology, Trondheim, Norway  
3Institute of Clinical Medicine, University of Oslo, Oslo, Norway  
4Division of Orthopaedic Surgery, Oslo University Hospital, Oslo, Norway 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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Project leader 
Frank-David Øhrn 
Introduction 
Mechanical alignment (MA) has for many years been the most used surgical alignment 
technique in total knee arthroplasty (TKA). This means that regardless of constitutional 
native anatomy (i.e. valgus or varus), one strives to achieve a neutral coronal knee axis on 
postoperative x-rays (Hip-Knee-Ankle angle, HKA). To achieve MA, the cuts are made 
perpendicular to the mechanical axes, and subsequent soft tissue balancing is performed if 
necessary. However, many patients do not have a neutral knee alignment before they 
develop osteoarthritis (1). Several authors therefore advocate the personalized alignment 
(kinematic, KA or functional alignment, FA), where the aim is to restore the patient's original 
pre-arthritis anatomy and joint line (2). This means that tibial component placement in varus 
or valgus is accepted, despite the possible result of a postoperative non-neutral HKA axis (3, 
4). Studies indicate that good clinical results can be achieved in terms of range of motion 
(ROM) and patient reported outcome measures (PROMs) with these techniques, but it has 
not been tested properly in terms of activity measurements, strength testing or migration of 
implants (5). There is diversity in the literature regarding whether tibial component with too 
much deviation from a neutral axis can lead to increased migration and eventually aseptic 
solution (6, 7). To date, only a few trials, with diverging results, have assessed migration of 
the implants implanted with KA or FA.  The methods are so far perceived as controversial, 
despite the widespread use (6-8). 
KA or FA can be performed by manual conventional surgery; however, the newly introduced 
robotic assisted surgery probably yields higher accuracy and precision of the cuts during 
surgery (9). This makes robotic assisted surgery well suited for personalized surgery. Yet, it is 
claimed that because of diversity of the different features for planning and executing the 
surgery, each system should be evaluated separately, and not as a group (10). We therefore 
planned this study to assess the efficacy of robotic assisted surgery comparing MA and 
personalized alignment (PA) techniques.  
Aims of the trial 
1. Evaluate the clinical outcomes of patients who have had TKA with PA and compare it with 
conventional MA. 
2. Analyse and compare the in vivo stability over time of TKA operated with PA vs. MA using 
CT- based radiostereometric analysis (CT-RSA). 
3. Evaluate the postoperative position of the implants using two different alignment 
philosophies. 
Objective 
Perform TKAs on patients using ROSA® Knee System (Zimmer Biomet, Warsaw, Indiana USA, 
Figure 2) robotic assisted surgery and randomize the patients to either PA or MA. 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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Material and methods 
A multiple blinded randomized controlled parallel superiority trial will be performed, where 
the patients, study nurse, statistician and physiotherapists are blinded to the surgical 
method (PA or MA). The study will include 152 patients (Figure 1). The study adheres to the 
consort statement (11).  
Inclusion criteria 
Patients aged 18-80 years with femoro-tibial or patello-femoral osteoarthritis (Kellgren-
Lawrence, K-L) grade 2-4 with persistent pain, referred to Kristiansund Hospital for primary 
TKA will be included in the study.  
Exclusion criteria 
Patients with serious psychiatric disorders, dementia, drug abuse or patients not able to 
speak and read Norwegian language making them noncompliant or unable to perform an 
informed consent. Patients with ongoing cancer therapy and or ASA classification >3 (12).  
Knee implant 
Medial Pivot (MP) and Medial Congruent (MC) prostheses seek to render the patient's 
constitutional kinematics (13, 14). Because of this, they are believed to be particularly well 
suited to PA, whom which also seeks to achieve natural knee axes for the patient. We 
therefore aspire to perform the study with the Persona ® MC (Zimmer Biomet, Warsaw, 
Indiana USA) prosthesis. The Persona MC TKA is a well-documented implant through both 
clinical and RSA studies (15-17). In addition, the implant is well known previously for several 
of the study surgeons. All TKAs will be performed with patella resurfacing.  
Robot assisted surgery 
The interventions will be carried out with the ROSA Knee robot-assisted surgery (Figure 2), 
with high accuracy and precision in the cuts (18). This is important because we want great 
agreement between the planned procedure and the achieved result in terms of alignment of 
the extremity and placement of the implant. The interventions will be performed at 
Kristiansund Hospital. A special protocol for the robotic MA and PA surgery will be made, 
whom to all the surgeons are obliged to adhere to.  
Randomization 
Prior to surgery, the patients will be randomized to either MA or PA using stratification on 
surgeon and gender. The randomization will be performed using the eFORSK Web Clinical 
Report Form (CRF, HEMIT, Norway).  
Analytical methods 
Work package 1 (WP1) - Patient reported outcome measures (PROMs) and clinical scores 
All patients will be examined with PROMs and clinical score preoperatively and 3, 12, 24 and 
60 months postoperatively. PROMs used are the Forgotten Joint Score (FJS) (19), Knee injury 
and Osteoarthritis Outcome Score (KOOS) (20), Visual Analogue Scale (VAS) (21) and the 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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generic Eq-5D (EuroQol Research Foundation) (22). Clinical testing will be performed 
including flexion, extension, range of motion (ROM) and clinical stability. 
WP2 - Daily physical activity 
ActivePalTM (activePal Technology, UK), an accelerometer-based activity monitor 
preoperatively, after 3, 12, 24 and 60 months postoperatively will be used. Of interest are 
the number of steps per day, the number of hours of activity per day, sit-to-stand transitions 
etc.  
WP 3 – Clinical testing and strength testing 
Maximum strength knee extension will be tested using a knee extension device 
preoperatively and after 3, 12 and 24 months postoperatively.  Voluntary activation with 
interpolated twitch will also be used (23). Other clinical tests such as 6 minutes walk test 
(6MWT), treadmill test, stair climbing and descent test, balance test and sit-to –stand test 
(24, 25). 
WP4 - CT-RSA for implant stability 
CT-RSA (Figure 3) has high precision of evaluating tibial implants (26) and will be used to 
assess implant stability. We will also perform migration analysis of femoral and patellar 
implants. Bone models of the femur, tibia and patella and implant models (femur and tibia) 
will be created in the CT based micromotion analysis software (CTMA, Sectra, Linköping, 
Sweden). A total of 8-9 tantalum markers of size 0.8-1 mm will be implanted in the 
polyethylene patella and the surrounding patella bone, and will be used to analyse implant 
migration (27, 28). CT-RSA will be performed postoperatively and after 3 , 12, 24 and 60 
months, with double acquisitions of at least 25 % of the patients (29).  
WP5 - Body composition 
CT images taken of the thigh and calf of the patient with soft tissue reconstruction will be 
analysed using artificial intelligence (AI) technology to assess the muscle and fat distribution 
in the relevant part of the thigh (30). This is to contribute to an alternative method for 
clinical endpoints. The change of muscle volume postoperatively at 3, 12 and 24 months will 
be correlated to other clinical data including muscle strength, PROMs and activity measures. 
WP 6 - Implant position 
Postoperative CT images from hip to ankle are used to calculate the coronal, axial and 
sagittal position of the femoral and tibial implants (31). 
WP 7 - Conventional radiology 
Preoperative conventional images of the knee for inclusion, postoperatively and after 2 
years. Preoperative HKA images, and after 3 months and 2 years for assessment of knee 
axes. 
 
 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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WP 8 - Miscellaneous 
 All blood loss during surgery will be estimated and registered.  
WP 9 - Knee kinematics 
Fluoroscopic footage during step up, step down or lunging of up to 60 patients will be 
performed with a flat panel fluoroscope, in order to assess the difference of the kinematics 
of the 2 groups (32). 
 
Statistical analysis  
Baseline data 
Baseline data such as gender, age, body mass index (BMI), American Society of 
Anaesthesiologists (ASA) classification, operation side, operation time (knife-to-skin time), 
total time spent in operating room (OR), type of anaesthesiology (i.e. general, or regional 
and femoral blocks) performing surgeon, implants used (including size), length of stay or day  
care surgery will be registered. During surgery, stability will be tested in 90 degrees flexion 
and full extension with by the robot. Normally distributed baseline data will be presented as 
means with 95 % confidence intervals (CI) unless otherwise stated. Non-normally distributed 
data will be presented with medians and interquartile ranges.  
Sample size 
All sample size calculations uses an alpha level of 5 % and a power of 80 %. 
WP1 - Patient reported outcome measures (PROMs) and clinical scores  
If we assume a standard deviation of KOOS of 20, and a clinical meaningful difference to be 
10, we need at least 126 patients. To account for potential dropouts, we add 10-20% 
therefore include 150 patients, 75 in each group.  
WP2 - Daily physical activity  
The activity level will be calculated by the use of the primary outcome measure mean steps 
per day preoperatively and 3, 12 and 24 months postoperatively. Linear mixed model 
analysis will be performed for calculation of group differences using a fixed (MA vs. PA) and 
random (patient id) factor (33). Secondary outcome measures are time spent lying, sitting, 
standing, and transitions between sitting and standing. Assuming a clinical meaningful 
difference in number of steps is a 1000 steps per day, with an anticipated SD of 2200, at 
least 76 patients in each group will be needed, using a 2-sided Student T-test (34).  
 
 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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WP 3 - Strength testing 
A difference in strength of 15 kg is considered clinically relevant. With an anticipated SD of 
20, we need at least 28 patients in each group (35). To account for dropouts, we therefore 
include 70 patients. 
WP4 – CT-RSA for implant stability 
In migration studies of the knee, the maximal total point motion (MTPM) of the tibial 
implant is usually the main outcome variable (36). Suppose a difference in continuous 
migration of 0.1 mm in order to be clinically relevant. A standard deviation of 0.2 and with a 
significance level of 95% and a power of 80% would require 16 cases in each group. In clinical 
studies, it is generally advised to include at least 50 patients in order to achieve balanced 
groups (37). To account for potential dropouts, we will include 60 patients in the migration 
study. The statistical analysis of the MTPM will include a linear mixed model analysis with a 
fixed (MA vs. PA) and random factor (patient id).  
Ethics 
No patients will be included unless they have signed an informed consent. The trial is 
approved by the Regional Ethical Committee of Norway (REK, id 738578), but will not 
commence until approval of the local data access committee (DAC) and data protection 
officer (PVO) of Møre and Romsdal Hospital Trust. The protocol follows the Helsinki 
declaration and will be registered in Clinicaltrials.gov. The trial adheres to the Consort 
statement (11).  
Funding 
The trial is funded through Møre and Romsdal Hospital Trust, an we will apply for regional 
and national research and innovation grants.  
Adverse events 
Complications of TKA are rather rare. All potential complications like readmissions, wound 
problems, infections, fractures, vessel and nerve damages, cerebral and cardiac incidents, 
thromboembolism, pneumonia or respiratory complications etc., will be accounted for. 
Collaborators 
Norwegian collaborating institutions include the Center for Implant Related Research Oslo 
(CIRRO, Oslo, Norway), Norwegian University of Science and Technology (NTNU, Trondheim, 
Norway) and Molde University College (Molde, Norway). We also aspire to collaborate with 
several universities in the EU.  
 
 
 
 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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Risks and measures for safety precaution 
Surgery 
All surgeons involved in the trial are experienced knee surgeons. The surgeons have received 
thorough tutoring in the use of the ROSA Knee System and the Persona TKA, and both 
alignment techiques have now been adopted in our standard treatment of end stage OA 
(38). The learning curve of robotic assisted surgery is probably very small, and more related 
to time spent on the procedure rather than placement of the implants (39, 40). The 
placement of the tibial implant will be restricted in the coronal plane to maximum 5 degrees 
of varus and 2 degrees of valgus. In sagittal plane, the slope will be limited to between 0-10 
degrees.  
The Persona TKA implant although contemporary, is a well-documented implant with very 
low migration (15, 16).  
The MA and PA techniques are well known and already used in a widespread fashion all 
around the world. Several clinics in Norway have also adopted the methods.  
Implantation of tantalum markers in bone and polyethylene has been performed for more 
than 40 years in numerous studies without any known complications (27, 41, 42).  
Known but rare complications to robotic surgery are fractures at the site of insertion of the 
bone pins, and pin site infections. In elderly or osteoporotic patients, we will consider using 
unicortical engagement of the pins. Concerning infections, all the default precautions in the 
OR will be taken, such as preoperative and postoperative administration of antibiotics, strict 
sterile procedures etc.  
Radiation 
CT-RSA utilizes low dose CT protocols. Previous studies show that this method uses less than 
0.08 mSv of effective doses per acquisition (26, 43). A special CT protocol will be created in 
order for as low as possible ED, still with sufficient precision to perform CT-RSA analyses. For 
the patients in the CT-RSA group of the patients, the total ED of the whole study will not 
exceed 3mSv. The patients not in the CT-RSA group will all receive well below 1 mSv. 
Protection and storage of data 
The randomization key will be stored in a locked cupboard in a closed envelope in the 
research room at Kristiansund Hospital. Only the surgeons and the scrub nurses will know 
the code. The data will otherwise be stored in the eFORSK system requiring safe log-in 
procedures via BankID (BankID BankAxept AS, Norway). Any export of data from this will be 
in Excel or SPPS sheets pseudo anonymized. Pseudo anonymized images for CT-RSA analyses 
will be exported to the server of Sectra located in Sweden. A data protection agreement 
(DAP) that follows the GDPR regulations will be signed prior to export of the images. A risk 
and vulnerability analysis (ROS analyse) was executed for this purpose by the safety officer 
of Møre and Romsdal Hospital Trust (Risikovurdering SECTRA).The CT images for 
BodyComposition analysis will also be exported to Ullevaal Hospital in Oslo via a safe tele- 
radiology line in the same manner as clinical images are exported (with full name and person 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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id). A special data transport agreement (DTA) will be signed for this purpose. These images 
will be stored in a safe research server at Oslo University Hospital, Oslo. CT images and 
fluoroscopic footage may also be exported too international collaborators in the EU/EEC 
after pseudo-anonymization. The latter will not be performed without special application to 
the REK, Data Access Committee (DAC) of Møre and Romsdal Hospital Trust and PVO (Data 
protection officer) in advance. 
User involvement 
The trial has been discussed with the user group of Møre and Romsdal Hospital Trust, and by 
Kristiansund Revmatikerforening, a regional user group of osteoarthritis. A local user 
representative will eventually be appointed to the trial.  
Articles planned from the trial  
 
1. Maximum strength of thigh after TKA assessing personalized versus mechanical 
alignment-1 yr. results  
a. Primary outcome variable: Strength of leg extension 
b. Secondary outcome variables: PROMs, sit-to –stand test, balance test, stair 
climbing and descent test, 6MWT 
2. Change of muscular volume up to 1 year after TKA in a study comparing personalized 
versus mechanical alignment-1 year  
a. Primary outcome variable 
b. Secondary outcome variables 
3. Walking distance 1 year after TKA in a study assessing personalized versus 
mechanical alignment-1 yr. results 
a. Primary outcome variable: Mean steps per day 
b. Secondary outcome variables: Time spent standing, sitting, laying. Number of 
sit-to stand transitions etc. 
4. Kinematics of personalized versus mechanical alignment evaluated using fluoroscopy 
5. Stability  of tibial implant using personalized versus mechanical alignment-2 
yrs.results 
a. MTPM 
b. Secondary outcome variables: Migration and rotation in 6 degrees of freedom 
(in mms and degrees) 
6. Clinical results of personalized versus mechanical alignment-2 yrs. results  
a. Primary outcome variables: KOOS5 
b. Secondary outcome variables: FJS, Eq-5d, steps/day, muscle strength 
7. Stability of a patella polyethylene implant-2 yrs. Results 
8. Clinical results of personalized versus mechanical alignment-5 yrs. Results 
a. Primary outcome variable: KOOS5 
b. Secondary outcome variables: FJS, Eq-5d, steps/day, muscle strength 
 
 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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9. Stability of tibial implant using personalized versus mechanical alignment-5 yrs. 
Results 
a. Primary outcome variable MTPM 
b. Secondary outcome variables: Migration and rotation in 6 degrees of freedom 
(in mms and degrees) 
 
Articles arising from this project will be published in highly ranked orthopaedic journals. 
Clinical data are to be published after 1 year, 2 years, 5 years and 10 years, and CT-RSA data 
after 2, 5 years and 10 years. 
 
Figure 1 Flowchart of the study 
 
 
 
WP4 n=60 CT-
RSA 
WP6 n=152 
ConvRAD 
WP5 n=60 BCA 
1 Yr Results publications 
3 mths results 
5 Yrs results publications 
N=152 
2 Yrs results publications 
WP2 n=152 
activPAL  
WP1 n=152 
PROMs 
WP3 n=70 
Strength 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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Modality 
Preoperative Postoperative 3 
mths 
12 
mths 
2 
yr. 
5 yr. 
10 
yr. 
CT scan (incl CT-
RSA) 
 
xx 
x 
x 
x 
x 
x 
BodyComposition 
 
x 
x 
x 
x 
x 
x 
HKA 
x 
 
x 
 
x 
x 
 
X-ray knee 
x 
x 
 
 
x 
x 
x 
PROMs 
x 
 
x 
x 
x 
x 
x 
activePAL 
x 
 
x 
x 
x 
x 
x 
VAS 
x 
x 
x 
x 
x 
x 
x 
Strength testing 
x 
 
x 
x 
x 
x 
x 
Walk and stairs 
x 
 
x 
x 
x 
x 
x 
Gait 
x 
 
x 
x 
x 
x 
x 
ROM 
x 
 
x 
x 
x 
x 
x 
Kinematics 
 
 
 
x 
 
 
 
Table 1 Table indicating time schedule for the patients. PROMs includes KOOS, FJS, EQ-5D and Knee Score.  
 
 
 
Figure 2 ROSA® Knee System already located in Kristiansund Hospital 
 

The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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Figure 3 CT-RSA model of tibial and femoral implants in a T 
 
 
 
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The personalKNEE Trial                                                                                                Frank-David Øhrn 
 
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