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Why do young males have a poorer outcome following knee replacement?

A 2018/2019 Summer Studentship research project

Identifying the reason for early revision in this group would allow surgeons to work with patients to avoid early revision which would obviously have a major impact on the outcomes for this group as well as having a profound socio-economic effect.

Student: Greer Mahoney
Supervisors: Professor Gary Hooper, Dr Debbie Snell
Sponsor: TBC

Project brief


Total knee replacement is ranked worldwide as one of the best surgical procedures to return patients with disabling osteoarthritis back to near normal function. The number of knee replacements is increasing throughout the world and the projections for New Zealand are up to a 150% increase by 2030. Failure of the knee replacement with a subsequent revision procedure is not only traumatic for the patient but also on average is x4 the cost of the primary operation and therefore has a profound impact on health funding in an environment which is already struggling to meet health needs.

The New Zealand joint registry (NZJR) was initiated in 1999 and has registered all knee replacements implanted in our country over that time. One of its primary roles is to record revision procedures and to identify areas of concern where premature revisions are required and to help analyse the potential reasons for these early failures. Males under the age of 55 years have been identified as a group that perform the poorest and are most likely to require early revision.

Since 2006 the Christchurch  Orthopaedic database  (COBRA) has recorded all knee replacements implanted at Burwood hospital with patient demographic data as well as preoperative and postoperative Patient Recorded Outcome Measures (PROMS). It can be linked with the NZJR to identify those that have failed early and gives preoperative PROMS which can be compared to outcomes at  months, 1, 5 and 10 years.


The aim of this study is to compare males <55 years who have had a knee replacement with those >75 years and to look at the patterns of failure within the 2 groups in an attempt to identify a cause for this early failure rate.


This study will cross match two prospective data bases, the NZJR to get the national perspective and the COBRA data base to examine the local trends. Demographic data will be examined in age and gender bands comparing: 1 the co-morbidities, 2 the reason for early revision (<1 year), 3 the reason for late revision and 4 the functional outcomes as recorded from the PROMS data.

The data will be analysed statistically to look for significant trends and outcomes in order to identify a potential reason for poorer results.

Student researcher’s component of the study

The student will be expected to:

  1. Complete a literature review on the subject
  2. Work with the data inputters of both databases to record and organize the data
  3. Work with the statistician to look for possible trends and outcomes, and
  4. Complete a draft paper outlining the methodology and results