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Publication - Professor Ashley Blom

    The association of body mass index with long term revision rates and 90-day mortality rates following primary total hip replacements

    findings from "The National Joint Registry of England, Wales, Northern Ireland and the Isle of Man"

    Citation

    Mouchti, S, Whitehouse, M, Sayers, A, Hunt, L, MacGregor, A & Blom, A, 2018, ‘The association of body mass index with long term revision rates and 90-day mortality rates following primary total hip replacements: findings from "The National Joint Registry of England, Wales, Northern Ireland and the Isle of Man"’. Journal of Bone and Joint Surgery (American edition), vol 100., pp. 2140-2152

    Abstract

    BackgroundThe influence of obesity on outcome following total hip replacement (THR) is unclear. Restriction to THR on the basis of body mass index (BMI) has been suggested. The purpose of this study was to assess the influence of BMI on the risk of revision and 90-day mortality.MethodsThis study is a population-based longitudinal cohort study of the National Joint Registry (NJR). Using data recorded from April 2003 to December 2015, linked to Office for National Statistics data, we ascertained revision and 90-day mortality rates following primary THR by BMI category. The probability of revision was estimated using Kaplan-Meier methods. Associations between BMI, revision and mortality were explored using adjusted Cox proportional hazards regression models.ResultsWe investigated revision and 90-day mortality in 415,598 and 413,741 operations, respectively. Each dataset accounts for approximately 58% of the total number of recorded operations in the NJR. 38% of patients were obese. At 10 years, obese class III patients had the highest cumulative probability of revision (6.7%;95%CI:5.5,8.2), twice that of the underweight group (3.3%;95%CI:2.2,4.9). When adjusted for age, gender, ASA grade, year of operation, indication and type of operation and compared to normal BMI, significantly higher hazard ratios for revision were observed in obese class I (1.14;95%CI:1.07,1.22;p<0.0001), II (1.30;95%CI:1.19,1.40;p<0.0001) and III (1.43;95%CI:1.27,1.61;p<0.0001) patients.Underweight patients had a substantially higher 90-day mortality (1.17%;95%CI:0.9,1.6) than normal. The hazard ratio of 90-day mortality was significantly higher in underweight (2.09;95%CI:1.51,2.89;p<0.0001) and significantly lower in overweight (0.70;95%CI:0.61,0.81;p<0.0001), obese class I (0.69;95%CI:0.59,0.81;p<0.0001), and II (0.79;95%CI:0.63,0.98;p=0.049) patients.ConclusionsAlthough revision rates in the long term following THR are higher in obese patients, the rates remained acceptable by contemporary standards and are balanced by a lower risk of 90-day mortality. Level of Evidence: Level II 

    Full details in the University publications repository