Abstract
Introduction:
There is an increasing trend within the US for utilization of total knee replacement for patients who are still of working-age. Numerous causes have been suggested, ranging from greater participation in demanding sporting activities to the epidemic of obesity. A universal concern is that increased arthritis burden will lead to increased disabilty and unsustainable health-care costs both now and in the future with increasing rates of revision surgery in the years ahead. This raises the critical question: Are younger patients receiving knee replacement prematurely? To address this issue, we compared the severity of operative knee pain and functional status in younger versus older TKR patients, drawing upon a national research registry.
Methods:
A cohort of 3314 primary TKR patients was identified from the FORCE national research consortium from all surgeries performed between July 1st 2011 and March 30th 2012. This set of patients was derived from 120 contributing surgeons in 23 US states. Data characterizing each patient undergoing surgery was derived from patients, surgeons and hospitals, and included the SF 36 Physical Component Score (PCS), the Knee injury and Osteoarthritis Outcome Score (KOOS) and the Oswestry Low Back Pain Disability Questionnaire. WOMAC scores were also calculated from the KOOS data and transformed to a 0-to-100 scale with lower scores representing worse impairment. Using descriptive statistics, we compared the demographic and baseline characteristics of patients younger than 65 years of age (n = 1326) vs. those 65 years of age and older (n = 1988).
Results:
40.0% of the study poulation was younger than 65 years of age. These younger patients were less likely to be white (86.4% vs. 92.7%, p < 0.0001), had a greater body mass index (mean BMI 33.0 vs. 30.5, p < 0.0001), and included a larger percentage of smokers (9.4% vs. 2.6%, p < 0.0001). There was a striking prevalence of musculo-skeletal co-morbidities in both groups, with half of the total cohort (50.7%) reporting impairment of at least one joint in addition to the operated knee. Involvement of additional joints was more common in older patients (56.0%) compared to the younger group (42.9%; p = 0.0001). Younger patients reported greater pain (47.3 vs. 53.9, p < 0.0001) and stiffness (38.1 vs. 46.6, p < 0.0001) in the operative knee joint and poorer overall function as measured by the WOMAC and SF36 PCS (WOMAC 50.2 vs. 53.0, p < 0.0001; PCS 32.1 vs. 33.0, p = 0.001). Function levels in both groups reflect significant impairment at time of surgery.
Conclusion:
At the time of TKR, younger patients have fewer medical illnesses, but higher rates of obesity and smoking as well as lower mental health scores. In addition, younger patients have the same or greater functional impairment compared to older patients. This supports the view that there should be earlier and more definitive treatment in younger TKR patients to prevent progression of joint disease. Our data suggest that TKR may benefit at an even earlier stage than at present in patients younger than 65 years of age. While it is likely this would improve short term outcomes, the longer term consequences may outweigh the benefits.
