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Team: Hussein M. Wahedally, Elena Kulinskaya and Alexander MacGregor

Project: Understanding longevity risks from hip replacement

Working paper 1. Short term excess mortality risk following total hip replacement and its duration (to be available by March 2017).
Working paper 2. Long term survival after primary total hip replacement: A retrospective study of 17,157 patients in the United Kingdom (to be available by March 2017).

Hip joint replacement surgery is one of the most common elective surgical procedures carried out in the UK [1]. According to a recent systematic review on mortality after total hip replacement (THR) [2], an excess post-operative mortality is associated with THR during the first 12 months following the procedure, while in the long term, advancements in lifestyle factors and surgical techniques for THR suggest an improvement in survival following the procedure. Mortality after primary THR is affected by many confounding variables each of which must be considered to enable valid interpretation. Routinely collected data by general practices can provide useful insights on variations in short and long-term mortality after primary THR procedure. The primary objectives of this research were to investigate how THR procedure affects the short and long-term mortality risk after the surgery given prior medical history of patients in the United Kingdom.

17,157 THR patients, born between 1987 and 2011, registered with general practices contributing to The Health Improvement Network (THIN) database, were used to develop two specific mortality models: to estimate odds of death during the first 24 months after the procedure and to estimate the long-term hazard of all-cause mortality following THR. Both mortality models were multilevel and included preoperative comorbidities, lifestyle and socio-demographic factors. These models produced accurate estimates of mortality risk after THR procedures that could inform professional healthcare on future medical management of THR patients and financial planning for retirement by patients, the actuarial industry, and the government.

This research found that in the first 24 months after THR, odds ratio (OR) for death after the surgery associated with THR cases, was higher than matched controls (OR=1.24 [95% CI: 1.11-1.36] for cemented procedures, OR=1.20 [95% CI: 1.04-1.38] for uncemented procedures and OR=1.02 [95% CI: 1.01-1.07] for other procedure types); while preoperative obesity, smoking and myocardial infarction increased OR for all types of THR procedures, compared to controls without these conditions.

In the long term, hazard ratio (HR) of all-cause mortality for THR cases was lower than controls for cemented procedures (HR=0.84 [95% CI: 0.72-0.97] for cemented procedures, HR=0.74 [95% CI: 0.66-0.83] for uncemented procedures and 0.92 [95% CI: 0.78-1.09] for other types of procedures); and was higher for patients with preoperative hypercholesterolemia and osteoporosis, relative to patients without these conditions. However overweight and obese THR cases before the surgery, had better survival prospects than patients with normal BMI. Furthermore, HR of patients increased to 1.26 [95% CI: 1.22-1.37] in highly deprived areas (Townsend score=5), compared to those from lowly deprived residential wards (Townsend score=1).

1. A. Judge, J. Chard, I. Learmonth, P. Dieppe. The effects of surgical volumes and training centre status on outcomes following total joint replacement: analysis of the Hospital Episode Statistics for England, J Public Health (Oxf), 28 (2) (2006), pp. 116-124, [Epub 2006/04/07]
2. Berstock, J. R., et al. "Mortality after total hip replacement surgery." Bone and Joint Research 3.6 (2014): 175-182.