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Hip replacement: needs and risks

Survey
Results
Mortality after hip replacement
Study
Results
Comment
We're getting older. Not just as individuals, but as a population. And not just in Britain, but across the world. Population pyramids showing the percentage of the population in successive age ranges used to be just that: pyramids that were bigger at the (younger) base and smaller at the (older) summit. That is changing, and in 30-50 years time we will talk of population cylinders. In 2050, about 11% of the population of the UK will be over 80 years old (Figure 1).

Figure 1: UK population 2050, by age



If you want to know more about age distributions of populations in the world, there is a great UN website ( http://www.un.org/esa/population/unpop.htm ). If you want to know how the population of the UK or any other county will change over the next 50 years, there's a terrific US website ( http://www.census.gov/ipc/www/idbpyr.html ).

This means that arthritis and the need for joint replacement surgery will increase. Do all those needing joint replacement surgery have the operation? In England, a survey in the 1990s suggested not [1].

Survey


North Yorkshire has about 210,000 persons aged over 55 years. In 1993 about 8% were mailed a questionnaire about activities of daily living, dependency, disability, and existing joint replacement. Also asked were questions about persistent joint problems. Those reporting a problem with hip and difficulty of daily living were sent a second questionnaire that included an index of severity of osteoarthritis of hip and knee. A score of 14 points out of a possible 24 was equivalent to extremely severe problems. Good responses were achieved for both postal questionnaires, minimising response bias.

Results


Women and men with existing hip replacements for different age ranges is shown in Figure 2. The overall estimate was 32/1000 people aged 55 and over, but rates were twice as high in women, and with older age.

Figure 2: Existing hip replacements



Rates of those who might benefit from hip replacement are shown in Figure 3. The overall rate was 14/1000 persons aged 55 years and older. Rates for women were higher than for men, and were higher with older age. Currently on a waiting list was 12% (as low as 3% for those over 75 years).

Figure 3: Requirement



Mortality after hip replacement


People undergoing hip replacement accept that their new hip will probably work very well, but also want to know the downside. Part of that downside, given that many will be older persons, is the risk of dying. A study from the USA [2] suggests that risk to be about 1 in 700.

Study


The Mayo Clinic performed a computer-assisted review of all 31,000 elective operations for hip replacement performed between 1969 and 1997. The records of patients who died were reviewed for relevant clinical information.

Results


Out of 30,714 operations, 90 patients died within 30 days. Four patients died during the operation (0.01%), and 86 during the 30-day follow up. Risk factors for mortality were increased age, being male, and a history of cardiorespiratory disease. Death rates were higher in the 1970s, and fell during the 1980s and 1990s (Figure 4). In the 1990s the mortality rate was 0.15%, about 1 in 700 operations.

Figure 4: Hip replacement - 30 day mortality



Comment


Elective hip replacement is an increasingly safe operation, a tribute to continuous improvement by orthopaedic surgeons, anaesthetists, and the primary care physicians keeping patients fitter for a serious operation. The problem is that we're probably not doing enough of them. Taking some average figures for the number of people aged 55 years and older in a population of 100,000 in England, the figures from the North Yorkshire survey translate into 379 hip replacements needing to be done (Table 1), of whom only 45 are likely to be on a waiting list.

Table 1: Projected hip operations in UK

Age

Number

Requirement
(per 1000)

Number of hip replacements needed

55-64 10,000 10.3 103
65-74 12,000 11.3 136
75+ 7,000 20 140

Total

379

There could be some quibbles over the accuracy of these figures from the 1990s compared with now, but they are not unrealistic. The average age of the population of the UK will soon reach 40 years for the first time. The demand for joint replacement is going to grow rapidly.

References:

  1. J Fear et al. Prevalence of hip problems in the population aged 55 years and over: access to specialist care and future demand for hip arthroplasty. British Journal of Rheumatology 1997 36: 74-76.
  2. J Parvizi et al. Thirty-day mortality after elective total hip arthroplasty. Journal of Bone and Joint Surgery 2001 83-A: 1524-1528.
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