Obesity and Joint Replacement, Part 1: Are BMI Restrictions Ethical?

Should "obese" people be required to lose weight before being permitted to get joint replacement surgery? Or a kidney transplant? Or before receiving fertility treatment? Or to donate an organ?

The question of weight restrictions on access to healthcare is one of the most critical ethical questions in healthcare today. It is certainly one that causes great difficulties for many people of size as they seek the best medical care and quality of life possible. As one doctor notes:

We talk about racial disparities in care and gender disparities in care, but there's actually weight disparities in care because these patients aren't getting needed therapy because of their weight.

Many people of size are denied access to Total Knee Arthroplasty (TKA, a.k.a. knee replacement) or Total Hip Arthroplasty (THA, a.k.a. hip replacement), based solely on Body Mass Index (BMI). They are similarly denied access to many other procedures as well, but let's focus on joint replacements today.

It will come as no surprise to readers that I oppose such restrictions, but let's take a moment to discuss fairly the arguments for and against BMI cut-offs and weight loss counseling for joint replacement surgery.

Obesity and Joints

One risk associated with obesity that is pretty consistent between studies is the negative effect of a higher weight on joints like knees and hips.

For most risks, an association between obesity and a particular condition (diabetes, for example) is a correlation, not causation. Many type 2 diabetics are obese, for example, but fatness does not cause diabetes, or all fat people would be diabetic (they aren't), and no skinny person would have type 2 diabetes (many do). It may well be instead that fatness is merely a symptom of an underlying condition (like the insulin resistance of PCOS) and that condition predisposes towards diabetes, rather than fatness is an actual cause of diabetes.

But for joint issues, there is more evidence for a causal relationship. Extra weight creates extra stress on the joints, and the knees are especially vulnerable. As a result, fat people do get more arthritis, mostly in the knees but perhaps also in the hips, and this can create significant pain and mobility issues for some.

However, there may be more to the story, because fat people get more hand arthritis too, and that is not a weight-bearing joint. Some have speculated that there may be metabolic and/or inflammatory factors predisposing to arthritis in heavier people. Lipedema, an adipose tissue disorder which affects many people of size, has also been shown to increase risk for knee arthritis, independent of weight.

Whatever the relationship is, at some point many people of size experience joint pain and struggle to figure out how to deal with that, which at some point might include surgically replacing the joint.

Alternatives to Joint Replacement 

Of course, it's important to remember that joint replacement is not the only option for treating arthritic joints. It's always important to explore the least-invasive options available before resorting to surgery. Many doctors will require patients to do several of the following therapies before considering joint replacement surgery because they may help the patient delay or completely avoid joint replacement surgery:

• Physical therapy to strengthen and balance the muscles around the knees
• Stretching exercises to increase flexibility and loosen tight muscles
• Pilates, water exercise, or directed exercise programs to increase strength and flexibility
• Injections of various types into the joint to help reduce inflammation and improve viscosity 

In addition to these traditional therapies, many patients have found help with:

• Acupuncture to reduce pain and loosen tight muscles
• Chiropractic care to keep the pelvis and back in better alignment and reduce joint stress
• Focused bodywork, like medical massage, fascial release, etc. to reduce pain, loosen tight muscles, and release scar tissue and restrictions
• Orthotics for better arch support and improved gait
• Muscle re-education programs (like the Alexander Technique or Rolfing) to address muscle strength imbalance and gait issues
• Various nutritional supplements (glucosamine, bone broth/gelatin, chondroitin, etc.) to help repair cartilage in the joint area and reduce pain

Stories of people of size using these and other ideas can be found here and here.

However, despite all these measures, some people of size have to consider at some point whether or not to get a joint replaced.

Of course, surgery in larger people is more technically difficult and always carries more risk for anesthesia accidents and surgical site infections, so surgeons aren't wild about doing surgery on fat people. That is understandable.

But should these challenges mean they should completely DENY access to knee or hip replacement surgery to fat people? Is it ethical to deny patients access to medical procedures because of weight restrictions? Is it ethical to require obese patients to undergo weight loss treatment before they can even be considered for joint replacements?

These are the critical ethics questions faced by orthopedic care providers these days.

Ethics Questions

One orthopedic surgeon, interviewed for an article about the ethics of denying high-BMI people access to knee replacement surgery, stated:

Obesity often causes osteoarthritis of the knee at relatively young age and these patients present themselves at your out-patient clinic demanding a total knee replacement as a solution for their problem...Bariatric surgery can definitely be an important part of treatment, but only in a multidisciplinary context in which psychological treatment is also applied. 'Obesity is a disorder which will only pass after specific treatment by a whole team of specialists. On top of that, if the obesity remains, the other non-orthopaedic health risks stay as well...for multiple reasons, a TKR [total knee replacement] is not the appropriate solution for a morbidly obese patient and will not lead to weight reduction. It is important to address the root cause and not fight the symptoms. Morbid obesity should be seen as a life-event that requires a multidisciplinary approach and cannot be resolved just by an orthopaedic surgeon.

This shows this doctor's bias. Nothing else matters but weight loss and "resolving" obesity. He views obese patients as having psychological problems, so he believes they need treatment by a "whole team of specialists." He sees fat people as physically and psychologically sick, thinks they brought the problem on themselves, and doesn't believe they deserve a joint replacement unless they earn it by being "reforming" their lives. Since a knee replacement doesn't usually produce weight loss (and to him weight loss is the real goal), he sees no reason to do a joint replacement on obese people unless they agree to weight loss treatment first, and joint replacement is the blackmail he holds over patients' heads until they comply.

News flash! The main justification for doing joint replacements is not to solve an "obesity problem."

Yes, many studies about weight patterns after joint replacement show that joint replacement doesn't usually result in weight loss and is not justified as a way to help people lose weight. However, these studies miss the point.

Whether or not weight loss occurs after joint replacement is IRRELEVANT. Impaired mobility and major pain are a significant interference with quality of life. The purpose of joint replacements is to IMPROVE QUALITY OF LIFE.

Let's say that again. Weight loss should NOT be the goal of joint replacement for obese people. Instead, the main goal is to improve quality of life, reduce pain, and to regain function. 

That this question is even brought up reveals the bias in so much of health care. The focus is on weight loss and little else. If a procedure does not lead to weight loss, then its utility and appropriateness is questioned, even when it brings many improvements in function and pain. And if people of size decline weight loss treatment, then many health care providers believe we don't "deserve" access to the same level of health care as everyone else.

Shame and Blame Only for Fat People

Another ethical problem in joint replacement discussions is the issue of blame. Fat people are not seen as "deserving" a joint replacement because they are blamed for developing the joint issues in the first place. The article quoted above has a typical viewpoint:

A patient needs to take responsibility for the choices they make. By choosing for an unhealthy lifestyle, consuming junk food frequently and rarely exercising, your tendency to become overweight is greater than that of a healthy individual. The greater the load a joint has to carry, the sooner it wears out and the sooner a total knee replacement is required. 

Here is the typical assumption of most care providers, that obesity is a choice. In other words, fat people are only fat because they have bad habits and refuse to take responsibility for them.

Yet the issue of obesity is far more complicated, since many fat people do not have "bad" habits and yet still are fat. Genetics are highly relevant. In addition, many diseases (such as Polycystic Ovary Syndrome and Lipedema) and medications (such as steroids, birth control, or SSRIs) can result in weight gain and obesity. The bottom line is that what causes obesity is quite complex and that for many people, OBESITY IS NOT A BEHAVIOR.

Yet orthopedists routinely justify denying joint replacement surgery to fat people based on the idea that they have caused their own condition and don't "deserve" treatment.

Sadly, shame and blame are part of the joint replacement discussion only for fat people. Average-sized people are rarely held responsible for their own mobility challenges, even those who have caused or added to the issue by engaging in certain sports or by participating in extreme sports.

Few athletes are denied joint replacements or other surgeries even though their injuries may lead to joint issues at a relatively early age and a high rate of needing the artificial joint replaced. But fat people are felt to have caused their own disability and therefore are seen as not "deserving" treatment. Haven't devotees of extreme sports and over-exercising brought on their own joint issues? Yet they are rarely denied joint replacements.

Don't forget, fat people have accidents and injuries too. Weight can exacerbate an injury and speed the development of arthritis, yes, but is often not the original cause. As with thinner people, the original injury causes the problem; the weight may accelerate susceptibility to arthritis but does not cause it. Yet many fat people with a history of injury are denied access to joint replacements and told that they only developed arthritis because they were fat, completely ignoring the role of the intervening injury.

But does it really matter why the condition developed? Playing the blame game does not serve anyone. EVERYONE deserves to have maximum function, mobility, and relief of pain. In the end, it does not matter why the arthritis has developed, just that it has developed and that it needs to be treated.

Yet many high-BMI patients are often told that they must lose weight to a certain BMI, are referred for bariatric surgery, or must submit to hard-core weight loss counseling or medical weight loss programs (which is often condescending or which involve dubious very low calorie diets) in order to be considered for a joint replacement.

Ethically, physicians can present information about the possible benefits of weight loss and can offer assistance for those who wish to pursue weight loss. It is one form of treatment that can be considered, and some people will be interested in pursuing it.

However, informed consent means that patients need to be presented with information on the benefits AND the risks of a proposed treatment. Therefore, physicians should also have to be honest about the strong evidence that few people manage to lose to a reasonable BMI or keep the weight off for any meaningful length of time, that weight loss has its own risks, and that for many, weight loss often leads to weight cycling and greater rebound, and weight cycling also has risks.

People of size can be counseled about the potential benefits and risks of weight loss before joint replacement. But informed consent means that patients also have the right not to choose a particular therapy. To outright deny the surgery, or to blackmail people into weight loss counseling or risky bariatric surgery in order to have access to a procedure to regain a normal life is fraught with ethical problems. It is just plain WRONG.

Some doctors even deny access to pain relief medication unless fat patients show a certain amount of weight loss. The comments section of one blog post tells such a story:

Now the...doctor is telling a woman I know that she needs to lose large amounts of weight before he can sign her up for a pain management clinic. Yes, being unable to exercise for the past year due to serious knee issues has meant that she’s gained weight… but if she’s serious about getting pain-free, apparently she will miraculously become able to do heavy-duty exercise until she loses fifty pounds and is suddenly worthy to have her pain managed.

Sometimes fat patients are even denied medical treatments to lessen pain:

A colleague of mine told me today that he was denied a cortisone shot in his knee by the VA because of his weight. He was told that when he got down to 250 pounds, then he could have the shot. This seems so wrong to me. He wants to be more active, but cannot because of knee pain. This pain is treatable, and the treatment could enable him to be more active, which would improve his health. But, they will not treat his knee pain because of their pre-conceived notion of what is healthy.

This is another ethical lapse; pain relief should not be used as emotional and physical blackmail into weight loss compliance.

Inevitably, when weight loss fails, as research shows it almost certainly will, that leaves patients with no recourse for pain relief. As one care provider succinctly put it in an article about denying hip replacements to patients with a BMI over 30:

Relief of pain is a universal human right.

Denying fat people adequate pain relief simply because of their size is blatantly unethical. As another commentator in the article remarked, "The decision is perverse and appears to breach basic principles of healthcare."

What Happens When Joint Replacement Is Denied?

Another important ethics question ignored by many in the orthopedics field is what happens to obese people who are denied access to joint replacements?

One recent online article did look at this question (my emphasis):

Because of the increased risks of complications, it is common practice for some surgeons to restrict the use of TKA in patients with a BMI of 40 or higher. Based on the current available data, many surgeons and surgeon groups across the country withhold surgical intervention in morbidly obese patients until body weight is optimized and associated medical comorbidities are better controlled...The medical and societal implications of withholding TKA in morbidly obese patients are unknown. 

We posit three potential outcomes for patients who are denied TKA based on their having a BMI of 40 or higher and other associated comorbidities: 1) The patient chooses to seek a second opinion and have total joint arthroplasty performed at another institution. 2) The patient chooses to seek appropriate medical options such as medical weight management counseling, bariatric surgery, or both, and achieves successful weight reduction to meet the total joint arthroplasty healthy BMI threshold (BMI less than 40). 3) The patient chooses to seek appropriate medical options such as medical weight management counseling and/or bariatric surgery, but is unable to achieve successful weight reduction to meet the total joint arthroplasty healthy BMI threshold. 

We propose that this last group of patients is the cohort that is most concerning and may benefit most from a targeted care pathway and a multidisciplinary medical weight loss management team. This healthcare team should include an orthopedic surgeon, bariatric surgeon, registered dietitian, exercise specialist, and mental health provider who can in concert provide comprehensive support for the morbidly obese patient to safely achieve the target body weight and BMI required for a safe and effective TKA that can improve quality of life. We are in the initial stages of developing such a program at our institution.

It's great that this group of doctors are actually concerned about what happens to fat people who are denied joint replacement access. However, it's appalling that their answer is to simply pressure those people into ever more radical weight loss techniques (and apparently, bariatric surgery).

They refuse to relax their clinic's BMI restrictions on the premise that it is too risky for these patients to undergo surgery, yet it's perfectly fine for those same people to undergo bariatric surgery instead? Somehow they miss the irony in this protocol.

Furthermore, they COMPLETELY MISS what is the most likely outcome of denying fat people joint replacement ─ increasing disability and pain, accompanied by decreasing mobility and fitness.

These doctors assume that fat people denied surgery will either lose weight (despite low long-term success rates of even fairly small amounts of weight), undergo radical weight loss treatment (on the assumption that this will help improve outcomes), or go find another doctor who will do their surgery at their weight.

They are completely discounting the many, many fat people who will stop their search right there because they assume that all orthopedic surgeons will deny joint replacement to them. It also ignores the fact that many fat people live in areas where indeed, all orthopedic surgeons do deny joint replacement to fat people.

And in the meantime, the arthritis just gets worse (making it harder to operate on), and the person becomes increasingly disabled. As Dr. John Morton of Stanford University School of Medicine notes:

Not operating on obese patients to avoid risk or cost can backfire, Morton points out. "When you delay treatment of these patients, it gets worse," he says.

The result of denying joint surgery based on BMI is that many fat people will grow increasingly disabled, increasingly unfit, and increasingly immobile because they cannot access the procedures which could help them regain their mobility and decrease their pain.

Since fitness is the biggest key to wellness and longevity regardless of BMI, denying fat people joint replacement may well shorten their lives. 

This is why fat people often stop seeing doctors for years and years. The condescending and patronizing way they are treated, the unrelenting pressure for radical weight loss or bariatric surgery, the denial of access to pain relief or procedures to help improve quality of life...all this is why fat people have so little trust in doctors.

And it's typical that even well-meaning providers like the ones in this article simply do not have a clue how they actually often WORSEN fat people's health in their attempt to "help" them.

Summary

Sadly, even today, a lot of orthopedic surgeons still refuse to do knee replacements or hip replacements on anyone with a BMI over 35 or over 40 (or sometimes less). 

In many places in the U.K., for example, people with a BMI over 35 have been routinely denied joint replacements and other surgeries. Some even deny joint replacements to those with a BMI over 30.

They justify this by pointing out the short-term risks associated with orthopedic surgery in high-BMI people. They suggest that higher complication rates and somewhat lower functional outcomes justify denying surgery to this group.

However, while substantial research shows that obese patients have higher rates of short-term problems like infection, blood loss, surgical revisions, blood clots and slower recovery after joint replacement surgery, not all research shows increased risks.

Furthermore, obese patients often show greater overall improvements in function and pain relief than non-obese patients, or the differences are not clinically meaningful.

Although clearly obese patients should be counseled about the potential risks (particularly the risk for infection among diabetics with a BMI over 40), the magnitude of risk is relatively modest and not so great that it justifies precluding obese patients from this surgery.

Rather, the risks are a call to surgeons to further examine the long-overlooked issue of proper medication dosing, the use of surgical drains, and wound management in high-BMI patients. 

Although total function may be modestly less improved and more revisions may need to be done in larger patients, most obese patients have very good long-term results from the surgery, even when both knees are replaced.

Even in super-obese patients (BMI over 50), joint replacements last well, although total function may be somewhat impacted compared to average-sized people.

Similarly, despite some increase in short-term risks, obese people respond well to hip replacement surgery and do well in the long-term. One study which followed obese hip replacement patients for a mean of 14.5 years concluded:

Our findings suggest there is no evidence to support withholding total hip replacement from obese patients with arthritic hips on the grounds that their outcome will be less satisfactory than those who are not obese.

Furthermore, if overall health is the real priority, the advantages of joint replacement for obese people is obvious.

It's hard to work on fitness when exercising results in high levels of pain. Yet once the joint is replaced, mobility is greatly increased and pain levels are decreased. Whether or not joint replacement leads to weight loss post-operatively is irrelevant; better mobility and less pain is a significant gain in quality of life and may also lead to better fitness, independent of weight change.

And better fitness, regardless of BMI, improves health, life span, and often quality of life. As one study put it:

Performing TKA or THA on patients with high BMI may increase mobility leading to improved quality of life.

Bottom line, obese people should not be denied access to the potentially life-changing pain relief and functional improvement of joint replacement surgery.

Although some orthopedic surgeons still outright deny surgery or require that high-BMI people lose weight or undergo bariatric surgery before being considered candidates for a joint replacement, more surgeons are beginning to recognize that such restrictions are unethical and unfair. One study stated:

Withholding surgery based on the BMI is not justified. 

Another study's authors concluded:

Universal denial of surgery based on BMI is unwarranted.

Some surgeons do not withhold knee replacement surgery, but do require that patients be referred to weight loss specialists first before being able to access surgery, even if such referrals do not result in weight loss. One recent review states:

We believe that obese patients should be informed of the above-mentioned risks and should be advised to lose weight. Many patients will fail to achieve this goal without professional help, so we refer obese patients with osteoarthritis to a multidisciplinary obesity outpatient clinic. If this approach fails to result in weight loss, the patient at least benefits from a thorough analysis of existing comorbidity and optimization of his or her medical condition. We do not withhold a total knee arthroplasty from these patients, but we inform them extensively regarding the risk that their obesity poses with regard to this procedure.

This presents another ethical dilemma. It is of course reasonable to inform patients of their risk profile before surgery, and this includes the potential risks associated with obesity and surgery. However, is this "extensive" information about risk presented neutrally without judgment, or is it done with scare-mongering and emotional blackmail? Too many care providers err on the side of the latter instead of the former in hopes of scaring fat people into weight loss compliance. This is not ethical and is not good medicine.

Similarly, the potential benefits of weight loss can be presented as a therapeutic option ─ as long as the surgeon also gives full disclosure of the potential risks of weight loss/cycling and its poor long-term success rate. But rarely do doctors acknowledge both the pros and cons of weight loss, and many emotionally harass patients about losing weight or mandate weight loss treatment before surgery can be accessed.

Fortunately, there is some good news on this topic. In the last few years, more and more surgeons and organizations are speaking out against BMI restrictions on access to joint replacements. They recognize that the tremendous improvement in mobility, quality of life, knee function, and pain relief is worth the trade-off of a potentially increased risk for mild short-term morbidity. As one review put it:

The improvements in patient-reported outcome measures experienced by patients were similar, irrespective of body mass index. Health policy should be based on the overall improvements in function and general health gained through surgery. Obese patients should not be excluded from the benefit of total knee arthroplasty, given that their overall improvements were equivalent to those of patients with a lower body mass index.

Other care providers are not quite there yet but are at least beginning to recognize the ethical implications of such restrictions and are debating their merits, as in this article:

While obesity does raise the risks of surgical complications, those don't always outweigh the benefits of the procedure, says Dr. Michael Parks, an orthopedic surgeon at the Hospital for Special Surgery in New York City who chairs the American Academy of Orthopaedic Surgeons Workgroup on Obesity..."We have to weigh ... their improvement in quality of life versus the potential costs," he adds.

And some care providers are also now beginning to recognize that much short-term morbidity in obese people may be prevented with different medication dosing and re-evaluating standard surgical protocols.

IT'S ABOUT TIME.

Now it's time to ensure that those surgeons who are still resisting treating high-BMI people also get the memo.

*You can read more about one Health At Every Size activist's journey with knee replacements here. You can read more about doctors requiring weight loss surgery in order for high-BMI patients to access knee replacement here. 


References

Media Articles on Joint Replacement Restrictions on BMI

• http://www.hss.edu/newsroom_knee-replacements-morbidly-obese-individuals.asp#.U-rVcvldW4g - "Study Overturns Common Assumption About Knee Replacements in Morbidly Obese Individuals"
• http://www.drsharma.ca/bmi-does-not-affect-outcomes-in-knee-replacement-surgery.html - BMI Does Not Affect Outcomes in Knee Replacement Surgery
• http://bonesmart.org/forum/threads/bmi-calculator-what-to-do-when-the-surgeon-says-youre-too-heavy-for-joint-replacement-surgery.15969/ - What to Do When the Surgeon Says You're Too Heavy for Joint Replacement Surgery
• http://health.usnews.com/health-news/patient-advice/articles/2016-04-11/too-fat-for-surgery - "Too Fat for Surgery" 
• http://www.erasmusmc.nl/erasmusjournalofmedicine/2787834/6th/EJM06_PAG_54-57 - "Sorry, but you will have to lose weight before receiving your knee replacement"

BMI and Morbidity from Knee Replacement Surgery (positive and negative)

J Bone Joint Surg Br. 2006 Mar;88(3):335-40. Does obesity influence the clinical outcome at five years following total knee replacement for osteoarthritis? Amin AK1, Patton JT, Cook RE, Brenkel IJ. PMID: 16498007

A total of 370 consecutive primary total knee replacements performed for osteoarthritis were followed up prospectively at 6, 18, 36 and 60 months. The Knee Society score and complications (perioperative mortality, superficial and deep wound infection, deep-vein thrombosis and revision rate) were recorded...There was no statistically-significant difference in the complication rates for the subgroups studied. Obesity did not influence the clinical outcome five years after total knee replacement.

J Bone Joint Surg Am. 2012 Oct 17;94(20):1839-44. doi: 10.2106/JBJS.K.00820. The influence of obesity on the complication rate and outcome of total knee arthroplasty: a meta-analysis and systematic literature review. Kerkhoffs GM1, Servien E, Dunn W, Dahm D, Bramer JA, Haverkamp D. PMID: 23079875

...A search of the literature was performed, and studies comparing the outcome of total knee arthroplasty in different weight groups were included...twenty studies were included in the data analysis. The presence of any infection was reported in fourteen studies including 15,276 patients (I2, 26%). Overall, infection occurred more often in obese patients, with an odds ratio of 1.90 (95% confidence interval [CI], 1.46 to 2.47). Deep infection requiring surgical debridement was reported in nine studies including 5061 patients (I2, 0%). Deep infection occurred more often in obese patients, with an odds ratio of 2.38 (95% CI, 1.28 to 4.55). Revision of the total knee arthroplasty, defined as exchange or removal of the components for any reason, was documented in eleven studies including 12,101 patients (I2, 25%). Revision for any reason occurred more often in obese patients, with an odds ratio of 1.30 (95% CI, 1.02 to 1.67). CONCLUSIONS: Obesity had a negative influence on outcome after total knee arthroplasty.

Bone Joint J. 2016 Sep;98-B(9):1160-6. doi: 10.1302/0301-620X.98B9.38024. Does bariatric surgery prior to total hip or knee arthroplasty reduce post-operative complications and improve clinical outcomes for obese patients? Systematic review and meta-analysis. Smith TO, Aboelmagd T, Hing CB, MacGregor A. PMID: 27587514 

AIMS: Our aim was to determine whether, based on the current literature, bariatric surgery prior to total hip (THA) or total knee arthroplasty (TKA) reduces the complication rates and improves the outcome following arthroplasty in obese patients. METHODS: A systematic literature search was undertaken of published and unpublished databases on the 5 November 2015. All papers reporting studies comparing obese patients who had undergone bariatric surgery prior to arthroplasty, or not, were included. Each study was assessed using the Downs and Black appraisal tool. A meta-analysis of risk ratios (RR) and 95% confidence intervals (CI) was performed to determine the incidence of complications including wound infection, deep vein thrombosis (DVT), pulmonary embolism (PE), revision surgery and mortality. RESULTS: From 156 potential studies, five were considered to be eligible for inclusion in the study. A total of 23 348 patients (657 who had undergone bariatric surgery, 22 691 who had not) were analysed. The evidence-base was moderate in quality. There was no statistically significant difference in outcomes such as superficial wound infection (relative risk (RR) 1.88; 95% confidence interval (CI) 0.95 to 0.37), deep wound infection (RR 1.04; 95% CI 0.65 to 1.66), DVT (RR 0.57; 95% CI 0.13 to 2.44), PE (RR 0.51; 95% CI 0.03 to 8.26), revision surgery (RR 1.24; 95% CI 0.75 to 2.05) or mortality (RR 1.25; 95% CI 0.16 to 9.89) between the two groups. CONCLUSION: For most peri-operative outcomes, bariatric surgery prior to THA or TKA does not significantly reduce the complication rates or improve the clinical outcome. This study questions the previous belief that bariatric surgery prior to arthroplasty may improve the clinical outcomes for patients who are obese or morbidly obese. This finding is based on moderate quality evidence. 

Osteoarthritis Cartilage. 2014 Jul;22(7):918-27. doi: 10.1016/j.joca.2014.04.013. Epub 2014 May 13. The effect of body mass index on the risk of post-operative complications during the 6 months following total hip replacement or total knee replacement surgery. Wallace G, Judge A, Prieto-Alhambra D, de Vries F, Arden NK, Cooper C. PMID: 24836211

OBJECTIVE: To assess the effect of obesity on 6-month post-operative complications following total knee (TKR) or hip (THR) replacement. DESIGN: Data for patients undergoing first THR or TKR between 1995 and 2011 was taken from the Clinical Practice Research Datalink...RESULTS: 31,817 THR patients and 32,485 TKR patients were identified for inclusion. Increasing BMI was associated with a significantly higher risk of wound infections, from 1.6% to 3.5% in THR patients (adjusted P < 0.01), and from 3% to 4.1% (adjusted P < 0.05) in TKR patients. DVT/PE risk also increased with obesity from 2.2% to 3.3% (adjusted P < 0.01) in THR patients and from 2.0% to 3.3% (adjusted P < 0.01) in TKR patients. Obesity was not associated with increased risk of other complications. CONCLUSION: Whilst an increased risk of wound infection and DVT/PE was observed amongst obese patients, absolute risks remain low and no such association was observed for MI, stroke and mortality. However this is a selected cohort (eligible for surgery according to judgement of NHS GPs and surgeons) and as such these results do not advocate surgery be given without consideration of BMI, but indicate that universal denial of surgery based on BMI is unwarranted.

J Surg Res. 2012 May 1;174(1):7-11. doi: 10.1016/j.jss.2011.05.057. Epub 2011 Jun 25. Does BMI affect perioperative complications following total knee and hip arthroplasty? Suleiman LI1, Ortega G, Ong'uti SK, Gonzalez DO, Tran DD, Onyike A, Turner PL, Fullum TM. PMID: 21816426

BACKGROUND: Orthopedic surgeons are reluctant to perform total knee (TKA) or hip (THA) arthroplasty on patients with high body mass index (BMI). Recent studies are conflicting regarding the risk of obesity on perioperative complications. Our study investigates the effect of BMI on perioperative complications in patients undergoing TKA and THA using a national risk-adjusted database. METHODS: A retrospective analysis was performed using the 2005-2007 American College of Surgeons-National Surgical Quality Improvement Program ACS-NSQIP dataset. Inclusion criteria were patients between 18 and 90 y of age who underwent TKA or THA. Patients were stratified into five BMI categories: normal, overweight, obese class I, obese class II, and morbidly obese. Demographic characteristics, length of stay, co-morbidities, and complication rates were compared across the BMI categories. RESULTS: A total of 1731 patients met the inclusion criteria, with 66% and 34% undergoing TKA and THA, respectively. A majority were female (60%) and >60 y (70%) in age. Of the patients who underwent TKA, 90% were either overweight or obese, compared with 77% in those undergoing THA. The overall preoperative comorbidity rate was 73%. The complication and mortality rates were 7% and 0.4%, respectively. When stratifying perioperative complications by BMI categories, no differences existed in the rates of infection (P = 0.368), respiratory (P = 0.073), cardiac (P = 0.381), renal (P = 0.558), and systemic (P = 0.216) complications. CONCLUSIONS: Our study demonstrates no statistical difference in perioperative complication rates in patients undergoing TKA or THA across BMI categories. Performing TKA or THA on patients with high BMI may increase mobility leading to improved quality of life.

J Bone Joint Surg Am. 2012 Aug 15;94(16):1501-8. The association between body mass index and the outcomes of total knee arthroplasty. Baker P1, Petheram T, Jameson S, Reed M, Gregg P, Deehan D. PMID: 22992819

BACKGROUND: In the United Kingdom, organizations involved in health-care commissioning have recently introduced legislation limiting access to total knee arthroplasty through the introduction of arbitrary thresholds unsupported by the literature and based on body mass index. This study aimed to establish the relationship between body mass index and patient-reported specific and general outcomes on total knee arthroplasty. METHODS: Using national patient-reported outcome measures (PROMs) linked to the National Joint Registry, we identified 13,673 primary total knee arthroplasties performed for the treatment of osteoarthritis...The improvement...was compared for three distinct groups based on body mass index (Group I [15 to 24.9 kg/m(2)], Group II [25 to 39.9 kg/m(2)], and Group III [40 to 60 kg/m(2)]) with use of multiple regression analysis to adjust for differences in age, sex, American Society of Anesthesiologists grade, general health rating, and number of comorbidities. RESULTS: The preoperative and postoperative patient-reported outcome measures declined to a similar extent with increasing body mass index. The gradient of the linear regression equation relating to the change in scores was positive in all cases, indicating that there was a tendency for scores to improve to a greater extent as body mass index increased...Wound complications were significantly higher (p < 0.001) at a rate of 17% (168 of 1018 patients) in Group III compared with 9% (121 of 1292 patients) in Group I. CONCLUSIONS: The improvements in patient-reported outcome measures experienced by patients were similar, irrespective of body mass index. Health policy should be based on the overall improvements in function and general health gained through surgery. Obese patients should not be excluded from the benefit of total knee arthroplasty, given that their overall improvements were equivalent to those of patients with a lower body mass index.

Obes Surg. 2016 May 17. [Epub ahead of print] Does Obesity Influence on the Functional Outcomes of a Total Knee Arthroplasty? Torres-Claramunt R1,2, Hinarejos P3,4, Leal-Blanquet J3, Sánchez-Soler JF3, Marí-Molina R3, Puig-Verdié L3,4, Monllau JC3,4. PMID: 27189353

BACKGROUND: The objective of this study was to compare the total knee arthroplasty (TKA) functional outcomes and quality of life of obese and non-obese patients. METHODS: Prospective comparative study, including all patients underwent TKA in a single centre. Patients were divided into three groups: Group 1 (Gr.1) BMI <30 kg/m2, Group 2 (Gr.2) BMI ≥ 30 kg/m2 and <35 kg/m2 and Group 3 (Gr.3) BMI ≥35 kg/m2. The Knee Society score (KSS) and SF-36 scores were obtained preoperatively and at 5 years of follow-up. RESULTS: A total of 689 patients were included (72.2 ± 7 years, 76.3 % women)...CONCLUSIONS: Although non-obese patients obtained better functional and reported quality of life scores than obese patients, there were no differences in the gain of quality of life and knee functionality between both groups at 5-years of follow-up. This is one of the largest series in a single centre published in literature and confirms the results obtained by other authors. Taking into account the different outcomes obtained, surgery should not be denied to patients that are obese, given that they obtained similar benefit than non-obese patients.