Obesity is a known risk factor for developing osteoarthritis and is also associated with an increased risk of developing complications post total hip replacement (THR). This study investigated the association between obesity and the risk of undergoing THR in Australia.

From July 2017 to June 2018 a National Health Survey was conducted by the Australian Bureau of Statistics to collect height and weight data on a representative sample of patients across urban and rural areas across the country. This study examined a cohort of patients undergoing primary THR utilising data from the Australian Orthopaedic Association National Joint Replacement Registry from the same time period. Obesity classes were determined according to WHO criteria.

Body mass index (BMI) for patients undergoing THR were obtained and the distribution of THR patients by BMI category was compared to the general population, in age and sex sub-groups.

Generalised linear models assuming a binomial distribution and a log link were used to generate relative risks. Data from underweight categories, and age categories 34 years and younger, were excluded from further analyses because of small numbers.

Data from the health survey showed there were 35.6% of persons overweight and 31.3% obese. During the same period, 32,495 primary THR were performed for osteoarthritis in Australia on patients who had a BMI recorded. Of these patients 37.1% were overweight and 41.7% were obese. Compared to the general population, there was a higher incidence of Class I, II, and III obesity in patients undergoing THR in both sexes aged 35 to 74 years. Class III obese females and males aged 55–64 years were 2.9 and 1.7 times more likely to undergo HR, respectively (p<0.001). Class III obese females and males underwent THR on average 5.7 and 7.0 years younger than their normal weight counterparts, respectively.

Obese Australians are at increased risk of undergoing THR, and at a younger age. A national approach to address the prevalence of obesity, and possible prevention strategies, is needed.

Aims

Several different designs of hemiarthroplasty are used to treat intracapsular fractures of the proximal femur, with large variations in costs. No clinical benefit of modular over monoblock designs has been reported in the literature. Long-term data are lacking. The aim of this study was to report the ten-year implant survival of commonly used designs of hemiarthroplasty.

Total Hip Arthroplasty (THA) is a successful operation for the management of end stage hip osteoarthritis (OA) but long term success is limited by wear of the polyethylene bearing surface. The aim of this study was to compare the rate of revision at 15 years in patients <55 who had a THA for OA, and received either cross-linked (XLPE) or conventional non cross-linked polyethylene (non-XLPE).

The study population was all patients with primary THAs undertaken for OA from 1999 to 31 December 2016. Outcomes were determined for all procedures, comparing THA performed with non-XLPE and XLPE and including the effect of age, sex, and reason for revision. The principal outcome measure was time to first revision using Kaplan-Meier estimates of survivorship.

There were 17,869 procedures recorded for younger patients <55 years of age undergoing THA for OA and using either non XLPE or XLPE. There was a fivefold increase in the rate of revision for procedures using non-XLPE after seven years. The 15 year cumulative percent revision of primary THA performed for OA in patients <55 with non XLPE was 17.4% (95% CI 15.5,19.5) and for XLPE was 6.6% (95%CI 5.5,7.8) HR >7 years =5.3, p<0.001. Non-XLPE and XLPE were combined with three different femoral head bearing surfaces: ceramic, metal and ceramicised metal. Within each bearing surface, XLPE had a lower rate of revision than non-XLPE. For the most common head size of 28mm XLPE had a lower rate of revision.

The use of XLPE has resulted in a significant reduction in the rate of revision for younger patients undergoing THA for OA at 15 years. This evidence suggests that longevity of THA is likely to be improved and may enable younger patients to undergo surgery, confident of a reduced need for revision in the long term.