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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
A Comparison of Kneeling Ability After Lateral or Midline Incisions In Total Knee Arthroplasty
Scientific title
A Comparison of Kneeling Ability After Lateral or Midline Incisions In Total Knee Arthroplasty
Secondary ID [1] 304887 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Osteoarthritis 323016 0
Condition category
Condition code
Musculoskeletal 320580 320580 0 0

Study type
Description of intervention(s) / exposure
Patients will be randomised to receive either a midline skin incision or a lateral skin incision. All patients will undergo total knee arthroplasty via a medial parapatellar approach. Total knee arthroplasty will take from 60 to 90 minutes, surgical duration, across all groups. Within the group of treating surgeons there will also be a distribution of patients receiving a total knee arthroplasty via navigated and non-navigated techniques, and receiving cruciate retaining or cruciate sacrificing knee replacements as per the surgeons’ preferred practice. These will not be specifically controlled for in the randomisation process as they are unlikely to affect kneeling tolerance and doing so will limit the external validity of the trial. Randomisation will be stratified based on patella resurfacing or no patella resurfacing, as this may impact kneeling tolerance. Adherence to the randomisation schedule will be monitored by audit of the operation notes. Post-operatively, all participants will undergo routine rehabilitation for total knee arthroplasty, involving full weight bearing and early active range of movement. Post-operative analgesia will consist of paracetamol and non-steroidal anti-inflammatories, with opioids for breakthrough pain as per routine clinical treatment.
Intervention code [1] 321283 0
Treatment: Surgery
Comparator / control treatment
Standard midline skin incisions will be assessed as the comparator.
Control group

Primary outcome [1] 328403 0
Kneeling test score will be used as the primary outcome measure. This is a previously validated test developed by the research team.
Timepoint [1] 328403 0
6-8 weeks, 6 months, 12 months (primary endpoint), and 24 months post-surgery
Secondary outcome [1] 398907 0
Forgotten Joint Score
Timepoint [1] 398907 0
6-8 weeks, 6 months, 12 months, and 24 months post-surgery
Secondary outcome [2] 399660 0
Knee Injury and Osteoarthritis Outcome Score
Timepoint [2] 399660 0
6-8 weeks, 6 months, 12 months, and 24 months post-surgery

Key inclusion criteria
- Age > 18 years
- Primary TKA (including bilateral)
- Undergoing a medial arthrotomy
- Not currently being treated for a psychiatric disorder, senile dementia, Alzheimer’s disease, presence of alcohol/substance abuse.
Minimum age
18 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
- Revision TKA (i.e. not primary surgery)
- Existing contralateral TKA with <110 degrees of flexion movement
- Poorly controlled diabetes or peripheral vascular disease
- Range of motion of 90 degrees or less pre-operatively
- Peripheral neuropathy or previous history of major spinal surgery
- Previous medial incision around the knee joint longer than 5 cm
- Previous major knee surgery (e.g. tibial tubercle transfer, tibial plateau fracture or open meniscus resection etc.)

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation by non-recruiting research assistant
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Computerised permuted block randomisation. Randomisation will be stratified based on patella resurfacing or no patella resurfacing.
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
An a priori sample size calculation estimated that 40 participants in each group, with four post-operative time points, will provide 80% power to detect an effect size of 0.5 SD with a=0.05. Due to the length of follow-up and potential for attrition a sample size of 45 per group will minimise the risk of inadequate power. It is anticipated that there will be an even distribution of patella resurfacing performed, and this will be included in covariate analysis to exclude it as a confounder. If implant subgroups are too small for meaningful analysis this will be noted in any subsequent publication; however, the inclusion of various implants in this study will increase the external validity of the study. Linear mixed models (with baseline value as a covariate and incision type as a fixed factor) will be used to evaluate the difference and 95% CI in kneeling tolerance, FJS and KOOS over the four post-operative time periods. Bootstrapped standard errors will be used in case of skewed distributions. A linear mixed model utilising repeated measures at all time-points will allow non-biased estimates of treatment effect in the presence of any potential missing cases, as the likelihood-based estimation procedure results in non-biased estimates, providing data are missing at random. Models will be adjusted for patellar resurfacing, and use of computer navigation.

Recruitment status
Not yet recruiting
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 20085 0
Hollywood Private Hospital - Nedlands
Recruitment hospital [2] 20086 0
St John of God Hospital, Midland - Midland
Recruitment postcode(s) [1] 34793 0
6009 - Nedlands
Recruitment postcode(s) [2] 34794 0
6056 - Midland

Funding & Sponsors
Funding source category [1] 309262 0
Name [1] 309262 0
Perth Orthopaedic and Sports Medicine Centre
Address [1] 309262 0
31 Outram Street
West Perth
WA 6005
Country [1] 309262 0
Primary sponsor type
Perth Orthopaedic and Sports Medicine Centre
31 Outram Street
West Perth
WA 6005
Secondary sponsor category [1] 310236 0
Name [1] 310236 0
Address [1] 310236 0
Country [1] 310236 0

Ethics approval
Ethics application status
Ethics committee name [1] 309103 0
Hollywood Private Hospital Ethics Committee
Ethics committee address [1] 309103 0
115 Monash Ave
WA 6009
Ethics committee country [1] 309103 0
Date submitted for ethics approval [1] 309103 0
Approval date [1] 309103 0
Ethics approval number [1] 309103 0

Brief summary
This is a prospective randomized controlled trial comparing the outcome of patients undergoing primary total knee arthroplasty with either a midline or a lateral skin incision. Patient outcomes will be collected and compared between the two surgical cohorts over a 24 month post-operative period, and will include a range of subjective and functional outcomes, and kneeling tolerance. It is hypothesised that there will be no difference in kneeling tolerance between midline or lateral skin incisions.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 112986 0
Prof Markus Kuster
Address 112986 0
Perth Orthopaedic & Sports Medicine Centre
31 Outram Street
West Perth WA 6005
Country 112986 0
Phone 112986 0
+61 8 9212 4264
Fax 112986 0
Email 112986 0
Contact person for public queries
Name 112987 0
Mr Nicholas Calvert
Address 112987 0
St John of God Hospital Bunbury
700 Robertson Dr, College Grove WA 6230
Country 112987 0
Phone 112987 0
+61 8 9722 1600
Fax 112987 0
Email 112987 0
Contact person for scientific queries
Name 112988 0
Prof Markus Kuster
Address 112988 0
Perth Orthopaedic & Sports Medicine Centre
31 Outram Street
West Perth WA 6005
Country 112988 0
Phone 112988 0
+61 8 9212 4264
Fax 112988 0
Email 112988 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
What data in particular will be shared?
Individual participant data underlying published results only, following de-identification
When will data be available (start and end dates)?
Beginning 3 months and ending 5 years following main results publication
Available to whom?
Case-by-case basis at the discretion of Primary Sponsor
Available for what types of analyses?
Only to achieve the aims in the approved proposal,
How or where can data be obtained?
Access subject to approvals by Principal Investigator (Prof Markus Kuster,
What supporting documents are/will be available?
No other documents available
Summary results
No Results