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Foreword: Obesity in Total Knee Arthroplasty
07 December 2012
16 December 2012
07 February 2013 (online)
Demographic studies have demonstrated a clear trend toward increased rates of obesity in the general population in the United States, which has become particularly prevalent in the past three decades. Several national as well as international organizations have drawn attention to what has been termed the “obesity epidemic” and have warned of the increased burden these patients will place on the health care system. In the United States, the Centers for Disease Control and Prevention have called for measures to prevent the increase in obesity and to potentially reverse its course. With an estimated 60% of the population in the United States either overweight or obese, and similar trends observed around the world, it is likely that these patients will be seen more frequently in physicians' offices, of which orthopedic surgeons are no exception.  
Obesity has also been long associated with decreased functional capacity and has been identified as a risk factor for developing osteoarthritis, distal extremity injuries, and poor surgical outcomes. Although the pathogenesis of osteoarthritis is multifactorial, mechanical overload secondary to obesity is one important factor that has been recognized as a condition that may contribute to the early development of arthritis in these patients. For total knee arthroplasty, which places patients at an increased risk for anesthesia, bleeding, or venous thromboembolic complications, obesity also increases the technical difficulty of the surgery. Normal anatomic landmarks may be difficult to visualize, which may make correct jig alignment or navigation pin placement less accurate. Some authors have reported worse short-term and long-term clinical and radiographic outcomes in these patients. 
However, there are further important considerations which are rarely discussed in the literature or at national meetings. Often, these patients are not able to lose a substantial amount of weight prior to any surgical procedure, which may make it difficult to find a physician who is willing to care for them. Furthermore, these patients may not be able to lose weight following total knee arthroplasty. A recent prospective trial by Dowsey and colleagues examined 529 obese patients and demonstrated that 13% of patients lost 5% or more of their preoperative body weight, whereas 21% of patients gained weight. The authors also noted that adverse events were much higher in morbidly obese patients (35%) than obese (23%) and nonobese patients (14%). The relative aversion in performing a total knee arthroplasty for obese patients due to these risks was affirmed in a recent survey of active members of the American Association of Hip and Knee Surgeons (AAHKS). Of the 1,142 practicing surgeons in the survey, 83% actively discouraged at least one patient from a lower extremity total joint arthroplasty because of a high body mass index. Furthermore, members stated that their major reason (84%) for discouraging surgery were concerns for postoperative complications.
Consequently, it is likely that these patients may visit several orthopedists before finding one who is willing to treat them. This very point was raised in a recent editorial in American Academy of Orthopedic Surgeons Now that put out a plea for compassionate care for these patients. Similar thoughts were echoed in another AAOS Now editorial by Adolph Y. Yates Jr., MD, who reminded readers that:
Obese patients rarely need to be reminded of their condition. Many overweight patients have suffered from the taunts of others since childhood and encounter recurring admonishments from health professionals on almost every visit. A surgeon's use of words such as “fat” or “morbidly obese” are [sic] not necessary and only confirm the patient's expectations.
Thus, obesity in orthopedics should be considered as not just a medical or surgical problem, but also a social problem where some patients may not be receiving adequate access to care on the grounds of surgeons wanting to avoid surgical complications or poor clinical results. Some observations, such as the inability for some patients to lose weight, and higher complications, such as periprosthetic infection, may have led to these valid concerns. However, total joint arthroplasty may be a true game changer in these patients. Apart from a subset of patients who are morbidly obese (BMI > 40 kg/m2) or superobese (BMI > 50 kg/m2), patients who are overweight or slightly obese are observed to have good clinical outcomes at long-term follow-up.
In this special issue on obesity in the Journal of Knee Surgery, we will examine these clinical outcomes, complications, and implant survivorship of obese patients. We will also review pearls and pitfalls in the treatment of these patients so that orthopedic surgeons may have a greater understanding of the challenges and rewards of treating this group of patients.
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