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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
Date results information initially provided
Type of registration
Retrospectively registered

Titles & IDs
Public title
A Study to Assess the Changes in Bone Around Cementless Knee Replacements
Scientific title
Use of the iDXA to Evaluate Prosthesis Effectiveness in Orthopaedic Subjects Who Undergo An Oxford Uni-Compartmental Knee Replacement
Secondary ID [1] 295177 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Knee osteoarthritis 309173 0
Condition category
Condition code
Musculoskeletal 308051 308051 0 0

Study type
Patient registry
Target follow-up duration
Target follow-up type
Description of intervention(s) / exposure
The intervention being studied prospectively is an Oxford cementless unicompartmental knee replacement in subjects with osteoarthritis of the knee. A DXA scanner will be used to evaluate the change in bone mineral density (BMD) around these knee implants postoperatively over a 5 year period.
A DXA scanner is a diagnostic machine that measures bone density and body composition. DXA stands for dual-energy x-ray absorptiometry, and is a well-validated and widely used technique that provides an accurate and precise quantitative assessment of BMD. The rationale behind using a DXA scanner pre and post operatively in this study is as follows. Bone loss around the knee prosthesis is an important factor in assessing long-term implant stability and survival. Post-transplantation bone loss is generally caused by a phenomenon known as stress shielding, or loss of bone density, which leads to less dense and weaker bones. Current practise post unicompartmental knee replacements is to follow up with a protocol of clinical evaluations including outcome scores and X-rays at regular intervals. However visual analysis of these radiographs provides no means of quantifying bone loss, and is unreliable with low precision of around 30% accuracy. In the past the only accurate method of assessing the bone in this area has been with a CT scan which exposes the subject to a significant dose of radiation. The uncemented Oxford unicompartmental knee replacement has been introduced in the last 5 years, with X-rays 2 years post-operatively showing good remodelling around the implant. Historically, uncemented unicompartmentatl knee replacements have poor survival results on international Joint registries. No studies on bone density/bone remodelling around unicompartmental knee replacements have been done, which is why we are proposing using iDXA, the latest bone density machine and software, in order to record bone quality around the implants. This bone density machine exposes the subject to approximately 1/10th of the radiation of a routine knee x-ray. Our hypothesis is that evaluating the bone quality beneath the tibial components will indicate whether the bone has bonded to the implant and also whether the observed x-ray changes are actually related to the functional outcomes. We believe that if the quality of the scan is good enough it may then supersede the normal x-ray as a method of evaluating the status of a knee replacement.
Use of the iDXA orthopaedic knee application is investigational and has not yet been cleared for general use, so the measurement will be done under investigator supervision and IRB approval.
The staff performing the DXA scan come from a Registered Nurse background, have completed the Australia, New Zealand Bone Mineral Society (ANZBMS) Clinical Bone Densitometry Training Course, and each have a minimum of 4 years experience in using the DXA BMD scanner.
Before the participants enter the study they will be provided with a Participant Information Sheet and Consent Form that explains what their participation in the study will involve including study procedures, potential risks and benefits, who is responsible for costs, compensation for injury during the study, and how the study information will be stored and used.
The participants will undergo an iDXA scan throughout the study at the following timepoints:
Up to 7 days pre operatively: Hip, spine and affected knee (the hip and spine are only scanned once pre operatively to identify if osteoporosis is present, and the knee is scanned as a baseline)
Post operatively: Operated knee at 6 weeks, 6 months, 12 months, 18 months, 2 years and 5 years post operatively
Standard clinical assessments will be performed during the study, and will include a radiograph of the operated knee, assessment of the participants Knee Society Score, and completion of the Total Knee Replacement questionnaire by the participant.
The standard clinical assessments will take place up to 7 days pre operatively and at the 6 month, 12 month, 18 month, 2 year and 5 year timepoints (ie. this excludes the 6 week timepoint).
Participants will have individualised appointment dates for the above activities, which will be performed at the local hospital where both the DXA scanner and X-ray departments are located. The participant will be routinely assessed by the surgeon in their rooms located in the same hospital. Once the DXA technician has completed the scan, they will have the participant complete the questionnaires, and report any changes in medications and any adverse events that have occurred since their last visit. Each of these visits should take 20-30 minutes to complete, plus the extra time needed for the routine X-ray and surgeon followup assessment.
Each participants involvement in the study will end once the final iDXA scan and other activities for the 5 years postoperative visit are performed.
Intervention code [1] 312333 0
Diagnosis / Prognosis
Comparator / control treatment
No control group
Control group

Primary outcome [1] 307342 0
Bone remodelling and stress sheilding following an uncemented Oxford unicompartmental knee replacement, as assessed using the DXA bone mineral density scanner.
Timepoint [1] 307342 0
At 6 weeks, 6 months, 12 months, 18 months, 2 years [primary timepoint] and 5 years [primary timepoint] postoperatively.
Secondary outcome [1] 351526 0
Participants operated knee pain and function will be assessed using the Total Knee Replacement questionnaire.
Timepoint [1] 351526 0
At 6 months, 12 months, 18 months, 2 years and 5 years postoperatively.
Secondary outcome [2] 351527 0
The degree of flexion, stability, function and pain in participants operated knee will be assessed using the 2-part Knee Society Score.
Timepoint [2] 351527 0
At 6 months, 12 months, 18 months, 2 years and 5 years postoperatively.

Key inclusion criteria
1. Adult (>30 years) males and females with anteromedial unicompartmental knee osteoarthritis.
2. Sufficient bone quality to allow insertion of a uni knee prosthesis.
3. Scheduled to undergo an Oxford cementless uni-compartmental knee replacement
3. Patello-femoral osteoarthritis is not a contraindication if person does not have symptoms from the patello-femoral joint.
4. Able to provide informed consent.
5. In good general health.
Minimum age
30 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
1. Neuromuscular or vascular disease in the affected leg
2. Found to be unsuitable for uncemented unicompartmental Oxford knee replacement before or at surgery
3. Preoperative extensions defect greater than 15 degrees
4. Preoperative maximal flexion of less than 100 degrees
5. Symptomatic patello-femoral osteoarthritis
6. Insufficiency of the anterior-cruciate ligament
7. Fracture sequelae (intraarticular fracture and all tibial condyle fractures)
8. Previous osteotomy
9. Previous extensive knee surgery
10. Metabolic bone disease
11. Rheumatoid arthritis
12. Postmenopausal women on systemic hormone replacement therapy
13. Long-term treatment with oral corticosteroids
14. Inability to give consent (such as history of Alzheimers disease)
15. History of misuse of drugs or alcohol
16. Serious psychiatric disease
17. Disseminated malignant disease and treatment with radiotherapy or chemotherapy
18. Serious systemic disease
19. Inability to complete the questionnaires in English
20. Women of childbearing age who are pregnant or who have not had a negative pregnancy test just prior to the examination
21. Orthopaedic deformity that prevents an iDXA scan of either knee

Study design
Natural history
Defined population
Statistical methods / analysis
A sample size of 100 patients will enable correlations between functional and BMD measures > approximately 0.3 (R-square>10%) to be detected as statistically significant p<0.05 with 80% power. Further, it is anticipated that no less than 60% of the sample will be re-assessed at 5 years and this sample size will enable correlations > about 0.35 to be detected as statistically significant with 80% power. A sample size of 60 means that the 95% confidence interval on the percentage showing stress shielding at five years will be no more than +/ - 13% and more likely +/- about 8%.
Standard descriptive statistics will be used to summarise the demographic and clinical features of the subject population. The BMD measures from the seven tibial regions and three femoral regions, and the functional scores will be summarised on each sampling occasion as means, medians, ranges and standard deviations. The frequency (percentage) of those with stress shielding on each post-operative occasion will be tabled with 95% confidence intervals.
BMD and Functional measures will be related and also compared to radiograph interpretations and the presence of stress shielding using Pearson’s and, Spearman’s correlation coefficients and ANOVA as appropriate.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 20826 0
New Zealand
State/province [1] 20826 0

Funding & Sponsors
Funding source category [1] 299764 0
Name [1] 299764 0
New Zealand Orthopaedic Association (NZOA) Wishbone Trust
Address [1] 299764 0
Level 12
Ranchhod Tower
39 The Terrace
Wellington 6011
Country [1] 299764 0
New Zealand
Funding source category [2] 300719 0
Self funded/Unfunded
Name [2] 300719 0
Dr Nigel Gilchrist
Address [2] 300719 0
C/O Burwood Hospital
300 Burwood Road
Christchurch, 8083
New Zealand
Country [2] 300719 0
New Zealand
Primary sponsor type
Professor Gary Hooper
Leinster Orthopaedic Centre
Leinster Chambers
165 Leinster Road
Christchurch 8014
New Zealand
Secondary sponsor category [1] 299104 0
Name [1] 299104 0
Dr Nigel Gilchrist
Address [1] 299104 0
C/O Burwood Hospital
300 Burwood Road
Christchurch, 8083
New Zealand
Country [1] 299104 0
New Zealand
Secondary sponsor category [2] 300261 0
Name [2] 300261 0
Mr Rod Maxwell
Address [2] 300261 0
Leinster Orthopaedic Centre
Leinster Chambers
165 Leinster Road
Christchurch 8014
Country [2] 300261 0
New Zealand
Secondary sponsor category [3] 300262 0
Name [3] 300262 0
Mr Ian Penny
Address [3] 300262 0
Forte Orthopaedics
Ground floor, Forte Health
132 Peterborough Street
Christchurch Central
Christchurch 8013
Country [3] 300262 0
New Zealand

Ethics approval
Ethics application status
Ethics committee name [1] 300655 0
Upper South A Regional Ethics Committee
Ethics committee address [1] 300655 0
Ministry of Health Health
4th Floor, 250 Oxford Tce
PO Box 3877
Ethics committee country [1] 300655 0
New Zealand
Date submitted for ethics approval [1] 300655 0
Approval date [1] 300655 0
Ethics approval number [1] 300655 0

Brief summary
The primary purpose of this study is to gather valuable information on how the tibia responds to an uncemented Oxford Unicompartmental Knee (UK) implant. Historically, uncemented unicompartmental knee replacements have had poor survival rates compared to cemented types. And the known phenomenon of stress shielding, or bone loss, post implant can jeopardize long-term implant stability and survival. As the relatively new Oxford UK implant has so far showed good bone growth around the prosthesis at the 2 year postoperative mark, it is hypothesized that the results of this study will show that Oxford uncemented UK replacements demonstrate good remodelling of the underlying bone with an absence of stress shielding. There will be good in-growth around the prosthesis and over time the bone density under the prosthesis will be maintained or improved.
Trial website
Trial related presentations / publications
1) Gilchrist N, Hooper G, Frampton C, Maguire P, Heard A, March R, Maxwell R, & Penny I. (2013) Measurement of bone density around the Oxford medial compartment knee replacement using iDXA. A precision study. Journal of Clinical Densitometry 16 (2), 178-182.

2) Hooper G, Gilchrist N, Maxwell R, March R, Heard A, & Frampton C. (2013) The effect of the Oxford uncemented medial compartment arthroplasty on the bone mineral density and content of the proximal tibia. The bone & joint journal 95 (11), 1480-1483.

3) Hooper G, Maxwell R, Wilkinson B, Mathew J, Woodfield T, Penny I, Burn P, & Frampton C. (2012) The Radiological Results Of The Uncemented Oxford Medial Compartment Arthroplasty. A Prospective Independent Study. Orthopaedic Proceedings 95 (SUPP_29), 25-25.

4) Hooper G, Gilchrist N, Frampton C, Maxwell R, Heard A, & Mcguire P. (2018) Bone Mineral Density and the Uncemented Oxford Medial Compartmental Arthroplasty. Orthopaedic Proceedings 94 (SUPP_XLI), 42-42.
Public notes

Principal investigator
Name 84358 0
Dr Nigel Gilchrist
Address 84358 0
CGM Research Trust
C/O Burwood Hospital
300 Burwood Road
Burwood, 8083
Country 84358 0
New Zealand
Phone 84358 0
+64 3 3377820
Fax 84358 0
+64 3 3377991
Email 84358 0
Contact person for public queries
Name 84359 0
Dr Nigel Gilchrist
Address 84359 0
CGM Research Trust
C/O Burwood Hospital
300 Burwood Road
Burwood, 8083
Country 84359 0
New Zealand
Phone 84359 0
+64 3 3377820
Fax 84359 0
+64 3 3377991
Email 84359 0
Contact person for scientific queries
Name 84360 0
A/Prof Gary Hooper
Address 84360 0
Leinster Orthopaedic Centre
Leinster Chambers
165 Leinster Road
Christchurch 8014
Country 84360 0
New Zealand
Phone 84360 0
+64 3 355 3302
Fax 84360 0
+64 3 355 3216
Email 84360 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No/undecided IPD sharing reason/comment
What supporting documents are/will be available?
No other documents available
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary