ANZCTR - Registration

The ANZCTR website will be unavailable from 1pm until 3pm (AEDT) on Wednesday the 30th of October for website maintenance. Please be sure to log out of the system in order to avoid any loss of data.

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been endorsed by the ANZCTR. Before participating in a study, talk to your health care provider and refer to this information for consumers

Trial registered on ANZCTR

Registration number

ACTRN12616000920493

Ethics application status

Approved

Date submitted

17/05/2016

Date registered

11/07/2016

Date last updated

11/07/2016

Type of registration

Retrospectively registered

Titles & IDs

Public title

A Comparison of Different Patellar Implant Designs in Total Knee Replacement.

Scientific title

A prospective randomized comparative trial (pilot study) to compare intra-operative and post-operative outcome measures between inset, onlay round and onlay oval designs of patellar implants in patients undergoing unilateral total knee arthroplasty for degenerative osteoarthritis

Secondary ID [1]

Nil Known

Universal Trial Number (UTN)

U1111-1179-9194

Trial acronym

Linked study record

Health condition

Health condition(s) or problem(s) studied:

Osteoarthritis

Condition category

Condition code

Musculoskeletal

Osteoarthritis

Surgery

Surgical techniques

Intervention/exposure

Study type

Interventional

Description of intervention(s) / exposure

This research will study the outcomes of using different patellar implants in Total Knee Arthroplasty (TKA). Patients with knee osteoarthritis undergoing TKA will be randomized into three groups allocated to one of the three patellar implants' designs. The different patellar designs to be evaluated in this study are:
- Onlay oval: asymmetrical oval patella designs with three projections cemented on the resurfaced patella.
- Onlay round: symmetrical round patella designs with three projections cemented on the resurfaced patella.
- Inset: a round biconvex design with one projection cemented on reamed under-surface of patella.

Intervention will be performed by a fellowship trained surgeons with minimum 10 years experience. The approximate duration of the TKA procedure is around 90 minutes. The duration of performing the selected patellar implants is 5-10 minutes. Adherence to the assigned randomization will be monitored by the assisting fellow. any misconduct or fidelity will be documented and reported in the monthly research meeting.

Intervention code [1]

Treatment: Surgery

Intervention code [2]

Treatment: Devices

Comparator / control treatment

The Inset design group will be the comparator group.

Control group

Active

Outcomes

Primary outcome [1]

Patellar surface coverage: A photograph will be taken to the patella after implanting the trial design with a ruler to the side. Photoshop CS program will be used to calculate the percentage of surface coverage by the implant.

Timepoint [1]

Intra-operative: This will be done after implanting the trial patellar design.

Primary outcome [2]

Patellar tilt on weight bearing merchant view (x-ray)

Timepoint [2]

6 months post surgery

Primary outcome [3]

Blood supply to patella using bone scan; to asses for patellar osteonecrosis.

Timepoint [3]

6 months post surgery

Secondary outcome [1]

Patient's pain and functional scores (Composite secondary outcome): using validated Kujala scores. (Patient self reported outcome score using validated questionnaire. Kujala questionnaire reports on patient's pain, daily activities and functional level)

Timepoint [1]

Pre-operative
6 months post surgery

Eligibility

Key inclusion criteria

Patients undergoing unilateral total knee arthroplasty for degenerative osteoarthritis

Minimum age

50 Years

Maximum age

85 Years

Sex

Both males and females

Can healthy volunteers participate?

Key exclusion criteria

- Revision TKA surgery
- Bilateral simultaneous TKA
- Prior osteotomies around the knee or extra-articular deformities
- Systemic inflammatory disease (e.g. rheumatoid arthritis, Systemic lupus erythematosus, etc)
- Medial and lateral knee ligamentous instability on knee examination.
- TKA for acute trauma and need for allograft
- Prior patellar fracture, ruptured extensor mechanism
- Constrained implants, stemmed components or metal augmentation during surgery.

Study design

Purpose of the study

Treatment

Allocation to intervention

Randomised controlled trial

Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)

A computer software will be used for randomization of patients into the three designs options. The study will be patient blinded. and the operating surgeon will be informed about the randomization at surgery time.(Allocation is not concealed)

Methods used to generate the sequence in which subjects will be randomised (sequence generation)

Computerised sequence generation

Masking / blinding

Blinded (masking used)

Who is / are masked / blinded?

The people receiving the treatment/s

Intervention assignment

Parallel

Other design features

Phase

Not Applicable

Type of endpoint/s

Statistical methods / analysis

Based on power analysis, a sample size of 20 patients in each cohort would provide appropriate power (beta level = 0.80, alpha level = 0.05) to detect an 80% improvement in percentage of patellar surface coverage (as oval onlay design proposed to provide nearly full coverage) and in risk of osteonecrosis by preserving the lateral facet with the oval onlay design. There will be a midterm analysis when 30 patients are recruited to assess whether significance has been reached and whether or not, further patient enrolment is necessary. Means, ranges, and standard deviations will be recorded for percentage of patellar surface coverage, pre-operative and postoperative scores in all groups. ANOVA will be used to compare differences in means between continuous variables. ANOVA will be used to statistically assess pre-operative demographic factors. Fisher's exact test will be used to test for significance in osteonecrosis difference (proportions) between the groups. Statistical significance set at p = 0.05.

Recruitment

Recruitment status

Recruiting

Date of first participant enrolment

Anticipated

Actual

15/06/2016

Date of last participant enrolment

Anticipated

31/08/2016

Actual

Date of last data collection

Anticipated

Actual

Sample size

Target

Accrual to date

Final

Recruitment in Australia

Recruitment state(s)

NSW

Recruitment hospital [1]

St George Private Hospital - Kogarah

Recruitment postcode(s) [1]

2217 - Kogarah

Funding & Sponsors

Funding source category [1]

Hospital

Name [1]

St George Private Hospital

Address [1]

1 South St, Kogarah NSW 2217

Country [1]

Australia

Primary sponsor type

Commercial sector/Industry

Name

Sydney Knee Specialist

Address

Sydney Knee Specialists, Suite 8
19, Kensington St
Kogarah, NSW 2217

Country

Australia

Secondary sponsor category [1]

None

Name [1]

Address [1]

Country [1]

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

Hunters New England research ethics and governance unit

Ethics committee address [1]

Research Support and Development Office
Locked bag 1, New Lambton, NSW, 2305

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

15/12/2015

Approval date [1]

25/02/2016

Ethics approval number [1]

Summary

Brief summary

Aim:
To compare the intra-operative and post-operative outcome measures between three different patellar implant designs in patients undergoing total knee arthroplasty (TKA) surgery with regards to patellar bone coverage and tracking, patient-reported outcomes and post-operative radiological and scintigraphic  analysis. 

Background:
Controversy remains regarding whether the patella should be resurfaced in total knee arthroplasty. However, at present the scientific literature supports patellar resurfacing with regards to reduced re-operation risk and improved long term patient satisfaction.
Two basic techniques present for resurfacing the patella; either onlay or inset. In the inset design, a round domed implant is reamed in the patella and fixed with a single central projection (peg). On the other hand, the onlay design has either round (symmetrical) or oval (asymmetrical) shaped patellae with three small peripheral pegs fixed on the cut surface of the patella. When using a round patellar implant, either onlay or inset, some surgeons perform a lateral facetectomy to avoid lateral compression syndrome and enhance patellar tracking. However, neither method has proved to be superior.

A wide range of complications are associated with patellar resurfacing. These include patellar fracture, osteonecrosis related to devascularisation, patellar polyethylene (PE) wear, aseptic loosening, instability, dislocation, overstuffing and rupture of the extensor mechanism. Many of these can be catastrophic. One should always consider the peculiar blood supply to the patella during TKA and patellar resurfacing as iatrogenic disruption of supplying vessels has been identified as a major contributing factor in post-operative patellofemoral complications. The hypothesis of this study is that onlay oval design provides optimal bone coverage, better tracking, better patient reported outcome scores and carries the lowest risk of osteonecrosis in comparison with the other two designs.

Trial Objectives:
To prospectively compare intra-operative observed measures, patient-reported outcome measures and radiological results between inset, onlay round and onlay oval designs of patellar implants in patients undergoing total knee arthroplasty surgery. Specifically, we will compare patellar surface bone coverage, pain and functional scores together with patellar tracking and vascular status of the patella postoperatively.

Trial website

Trial related presentations / publications

Public notes

Attachments [1]

/AnzctrAttachments/370165-Patella trial protocol ED edit.docx

Contacts

Principal investigator

Name

Dr Samuel Macdessi

Address

Sydney Knee Specialists, Suite 8, 19, Kensington St, Kogarah NSW 2217

Country

Australia

Phone

+61283070333

Fax

[email protected]

Contact person for public queries

Name

Samuel Macdessi

Address

Sydney Knee Specialists, Suite 8, 19, Kensington St, Kogarah NSW 2217

Country

Australia

Phone

+61283070333

Fax

[email protected]

Contact person for scientific queries

Name

Samuel Macdess

Address

Sydney Knee Specialists, Suite 8, 19, Kensington St, Kogarah NSW 2217

Country

Australia

Phone

+61283070333

Fax

[email protected]

No information has been provided regarding IPD availability

What supporting documents are/will be available?

No Supporting Document Provided

Results publications and other study-related documents

Documents added manually

No documents have been uploaded by study researchers.

Documents added automatically

Source	Title	Year of Publication	DOI
Embase	Does Choice of Patellar Implant in Total Knee Arthroplasty Matter?: A Randomized Comparative Trial of 3 Commonly Used Designs.	2023	https://dx.doi.org/10.2106/JBJS.22.00655

N.B. These documents automatically identified may not have been verified by the study sponsor.

Trial Review

Documents added manually

Documents added automatically