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Titel på arbejdet Association between Obesity and Outcome after Total Knee and Hip Replacement
Navn Anette Liljensøe
Årstal 2014
Afdeling / Sted Ortopædkirurgisk afd., Aarhus Universitetshospital
Universitet Aarhus Universitet
  • Hip and knee surgery
Abstract / Summary

In Denmark, about 15,000 primary total knee arthroplasty (TKA) and total hip arthroplasty (THA) are performed annually, and in all countries there seems to be a rapid increase in the number of TKAs and THAs. At the same time, the prevalence of overweight and obesity has increased markedly over the past 50 years, and today 47% of the adult Danish population are overweight or obese.

The main aim of this PhD thesis was 1. to investigate whether there was an association between the preoperative BMI of patients who underwent TKA and their QoL and physical function 3–5 years after surgery, 2. to investigate whether there was an association between the preoperative BMI of patients who underwent THA and their QoL, physical function, and body composition before surgery and 1 year after surgery, and 3. to investigate whether it was feasible and safe to implement an intensive weight loss program in order to reduce TKA patients’ preoperative body weight, before surgery.

197 patients who had undergone primary TKA participated in a 3–5 year follow-up study. The outcome measures were the patient-reported Short Form 36 (SF-36) and the American Knee Society score (KSS). The results were adjusted for age, gender, primary disease, and surgical approach and showed a statistically significant negative association between BMI and 9 of 14 endpoints. For all outcome measures, we found an odds ratio (OR) of <1. A difference in BMI of 1 kg/m2 increased the risk of 8% of obtaining a lower score for the person with the higher BMI. 98 consecutive THA patients were included in the study. Data were collected at baseline preoperatively and at follow-up 1 year after surgery. The outcome measures were SF-36, HOOS, and body composition measured with DXA. The results were adjusted for age, gender, and co-morbidities and showed that obese patients had a statistically significant increased risk of 84% of obtaining a poorer physical function and a 77% increased risk of obtaining a worse activity in daily living 1 year after THA, compared with normal-weight patients. In addition, the obese patient’s hospitalization was 1 day longer than that of the normal-weight patients. In contrast, the results suggest that the overweight group accomplished a larger improvement in scores from preoperative to 1 year after surgery, compared with patients with a normal weight. There were no clinically significant changes in patients’ body composition 1 year after THA. 77 consecutive TKA patients with BMI > 30 were randomized to either a control group following the standard treatment for TKA or an intervention group following a low-energy diet (810 kcal/day) (weight loss group) and nutritional education for 8 weeks before surgery. Outcomes were assessed: before intervention for the weight loss group, and within 1 week preoperatively for both the weight loss group and the control group. The average weight loss was 10.7 kg (10% of body weight), and a decrease in fat mass of 6.7 kg and 3 kg lean mass. However, there was an increase of 2.3% in lean%. There was no statistically significant difference in lean mass and lean% between the groups. In addition, cholesterol decreased and systolic blood pressure decreased by 12 mm/Hg. One serious adverse event presumably happened due to a too large dose of antihypertensive medication in a patient. 2 patients postponed their TKA with 6 months after their weight loss. All patients underwent surgery, and no perioperative complications were recorded in any of the groups.

In conclusion, our results suggest that obesity is a risk factor for outcome after both primary TKA and THA. A high BMI in primary TKA patients is a predictor of the outcome, and it increases the risk of poor QoL and the risk of low knee-related health 3 to 5 years after TKA, and poor improvement in QoL and knee-related health. Obesity in primary THA patients also increases the risk of poor QoL and hip-related health 1 year after THA, and obesity retards improvement in general-health and QoL during the first year after surgery. Moreover, the obese THA patients’ hospitalization was 1 day longer than that of patients with normal weight. However, the results indicate that the overweight THA group accomplished the largest improvement of physical and mental general health and hip-related health compared with normal-weight patients. The preoperative results in the intervention study suggest that it is feasible and safe to implement an intensive weight loss program shortly before primary TKA, and they also suggests that there are several advantages of using the waiting time for surgery to encourage weight loss in the obese patients

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