The demand for hip and knee replacements is only increasing. It was predicted that from 2010 to 2030, the demand for hip replacements will increase 170% (1.7x) and the demand for knee replacements will increase 670% (6.7x)
The majority of hip replacements are for people in their 60s and 70s (average age about 70 years old). But people in their 40s & 50s, as well as people in their 80s & 90s get hip replacements. Lets take a look at how well these younger and older patients do.
Older patients (>80 years old).
Patients over 80 years old appear to have excellent outcomes after total hip or knee replacement. They achieve improved pain and improved function similar to younger patients undergoing these same surgeries.
In Total Hip, older patients showed long-term improved pain compared to younger patients, and the same functional improvements early after surgery, but by 5 years, the patients over 80 were showing worse function due to the effects of advanced age and their other medical conditions. Therefore, for hip replacement, pain is well treated but the effects of improved function are not as long lasting in general because the older age of the patients are associated with other factors that limit ability to use stairs and go on longer walks.
In Total Knee, older patients also showed long-term improved pain, and improved function, compared to younger patients getting a total knee, however they more commonly need a walker. Walkers were needed in about 72% of patients after total hip and in about 50% of patients after total knee replacement. The need for walkers highlights an important risk among these elderly patients: FALLS. People have a higher risk of falling as they get older and this does not change significantly after getting a joint replacement. Falling with a joint replacement can cause a fracture near the hip replacement, which typically requires a second surgery.
One study actually looked at people in their 90s and found that they too improved significantly with pain and function after a knee replacement, and therefore, age alone should not prevent people from getting a surgery that can improve quality of life.
As mentioned above, it is seen that older patients are more likely to have other medical conditions (such as atrial fibrillation, high blood pressure etc) that can complicate recovery from surgery. There are reports of higher complication rates after surgery due to these medical conditions. One study suggested that the risk of death after surgery was 3x higher, the risk of heart attach or other heart injury was 2.5x higher, and the risk of pneumonia was 3.5x higher. Another study looking 1 year mortality risk saw 5% in 90 year olds, 3% in 80 year olds and 0.8% in younger patients (not all of this is attributed to the surgery because the overall mortality rate for all 90 year olds is 12% at 1 year...which is actually higher than those undergoing surgery probably because those cleared for surgery are healthier). This significant increased risk is important to remember because a hip and knee replacement surgery is "elective", its life-improving but not life-saving...and therefore patients need to know that the surgery can be considerable more life-threatening in patients older than 80.
The length of hospitalization is also longer (3.4 days for 90s, 3.3 days for 80s, and 2.8 days for < 80).
The next question is whether we can look at the associated medical conditions of people in their 80s to predict who will have the highest risk for complication. Although one would assume that these co-morbidities would increase the number of complications, one study compared pre-operative medical conditions and looked at complications after surgery, and could not find a direct relationship.
Younger Patients (<60 years old)
The number of patients under 65 years old is the largest growing age group for needing hip and knee arthroplasty. They are fundamentally different patients than the 65 year old. These patients on average place greater demands on their replacements because they are more active. A hip or knee replacement is like getting a new set of tires. Tires typically last about 40,000 miles, and you can say the same thing about hip and knee replacements: they wear out over time, but its not about number of years rather about the number of miles. For this reason, it is believed that hip and knee replacements dont last as long in the younger population.
However, some studies looked at the activity level of total hip patients under the age of 50 years old and found that they were hardly more active then the older counterparts (these people wore pedometers which showed about 1.2 million gait cycles per year).
Similarly many studies have suggested that the wear rates for people under 50 years old are not considerably different (0.1 mm/year).
Other studies have looked at total knee and partial knee replacements. It appears that at 10 years after partial knee replacement 90% of people under 60 years old still have a functioning implant (compared to 96% in people over 60 years old).
For total knee replacements, some studies suggest that young patients (average age 50) are very happy with their knee replacement at 5 years (and very low risk of failed implants), while a recent study by Parvizi et al suggests that about 1/3 of patients reported residual symptoms and limitations of function.
Yet although many younger patients demonstrate persistence of some symptoms, the majority of implants last a long time. In the first 10 years after TKA, 90-98% of implants survived. In the second 10 years after TKA, 85-95% of implants survived.
Y.H. Kim, H.K. Kook, J.S. Kim. Total hip replacement with a cementless acetabular component and a cemented femoral component in patients younger than fifty years of age. J Bone Joint Surg Am, 84 (2002), p. 770
K.F. Orishimo, A.M. Claus, C.J. Sychterz, et al. Relationship between polyethylene wear and osteolysis in hips with a second-generation porous-coated cementless cup after seven years of follow-up. J Bone Joint Surg Am, 85 (2003), p. 1095
Activity level in young patients with primary total hip arthroplasty: a 5-year minimum follow-up. VF Sechriest et al. Journal of Arthroplasty 2007.
Oxford medial unicompartmental knee arthroplasty in patients younger and older than 60 years of age . AJ Price, CAF Dodd et al. Bone & Joint Journal. 2005
High level of residual symptoms in young patients after total knee arthroplasty. J Parvizi, RM Nunley, et al. CORR 2014.
What is the evidence for total knee arthroplasty in young patients?: a systematic review of the literature. Keeney JA et al. Clin Orthop Relat Res. (2011)
3. knee replacement in 90 year olds. Belmar CJ, Barth P, Lonner JH, Lotke PA: Total knee arthroplasty in patients 90 years of age and older. J Arthroplasty 1999;14(8):911–914
4. Berend ME, Thong AE, Faris GW, Newbern G, Pierson JL, Ritter MA: Total joint arthroplasty in the extremely elderly: Hip and knee arthroplasty after entering the 89th year of life. J Arthroplasty 2003;18(7):817–821
3. increasing demand for hip and knee replacements over the next few decades. Kurtz S, et al. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am 2007;89(4):780–785
6. study compared patient pre-operative medical conditions and looked at complications after surgery, and could not find a direct relationship. de Thomasson E, Caux I, Guingand O, Terracher R, Mazel C: Total hip arthroplasty for osteoarthritis in patients aged 80 years or older: Influence of co-morbidities on final outcome. Orthop Traumatol Surg Res 2009;95(4):249–253.
9. much higher risk of morbidity and mortality. Kreder HJ, Berry GK, McMurtry IA, Halman SI: Arthroplasty in the octogenarian: Quantifying the risks. J Arthroplasty 2005;20(3):289–293.
10. Miric A, Inacio MC, Kelly MP, Namba RS: Are nonagenarians told for total hip arthroplasty? An evaluation of morbidity and mortality within a total joint replacement registry. J Arthroplasty 2015;30(8):1324–1327