Obesity and Joint Replacement, Part 2: Does Losing Weight First Improve Outcomes?

We have been discussing obesity and joint replacement operations, specifically knee replacements and hip replacements, and the common practice of denying these to people of size.

In Part One, we discussed the highly questionable ethics behind denying "obese" people joint replacement operations or requiring that they undergo weight loss counseling or bariatric surgery first. These practices keep many people of size from accessing joint replacements and improving their functional abilities and pain levels, sentencing many larger people to the difficulties of dealing with mobility challenges and a poorer quality of life.

Today, we discuss the data on whether losing weight before joint replacement actually improves long-term outcome, as so many doctors insist it will. Up till now it has been assumed that it will, but a closer look at longer-term research calls this assumption into question. Indeed, several recent studies that suggest that losing weight before knee replacement surgery does NOT improve outcome and might even result in worse outcomes.

Does Weight Loss Before Knee Replacement Help?

Of course, some readers will be asking, why not consider weight loss? If it will reduce the physical load on the joint and lessen pain and wear, why not pursue weight loss?

The answer is complicated.

It certainly seems logical that it would be advantageous to lose weight before an operation to replace a weight-bearing joint. There would be less weight and therefore less force on the joint, right?

And to be fair, there's definitely research that shows modest improvements in functionality, joint force load, and pain levels with weight loss in patients with knee pain.

However, like most weight-loss research, these studies usually follow patients only short-term so the usual weight rebound effect is conveniently overlooked or minimized.

Even studies that promote weight loss for knee osteoarthritis admit (my emphasis):

Whether substantial weight loss can delay or even reverse the symptoms associated with osteoarthritis remains to be seen.

In other words, they do NOT have long-term proof that weight loss improves outcomes; they just assume it does because short-term studies (often just a few months) suggest some improvement.

This is the problem with nearly all weight-loss research; it only follows the patients long enough to show some benefits of a quick loss, but rarely follow patients long-term because many of the benefits are lost and most of the weight is regained (and often more), and doctors don't want to acknowledge that.

Even the usual recommendation to "lose just 5-10%" of a person's weight is problematic. While some research indicates modest benefits, research is actually quite limited on the long-term effects of such a loss. And most dieters do not manage or just barely manage that 5-10% weight loss over time.

Reviews of long-term research shows that for most people, few maintain the weight loss over time, most of the weight loss is regained with time, and many people rebound to higher weights or greater abdominal fat than they began with. There are biological reasons for this weight regain; it's not just about willpower.

Furthermore, weight loss can present risks as well as benefits, frequent weight fluctuation can be detrimental to health, and intentional weight loss/"dietary restraint" is one of the strongest predictors of long-term weight gain.

As a result, some care providers are now recommending that obese patients strive for weight stability rather than weight loss, and that the emphasis be placed on improving health habits and health measures instead of reducing a number on a scale.

Unfortunately, because short-term research shows modest improvements in joint function with weight loss, doctors have extrapolated this to assume that significant weight loss will improve long-term outcomes for joint replacement surgeries. As a result, some deny joint replacement to people above a certain BMI, practically mandate attendance at weight loss programs first, browbeat their patients about weight loss, or strongly push for bariatric surgery instead.

But does weight loss before joint replacement improve outcomes?

Weight Loss Before Joint Replacement 

In two recent new studies, the common assumption that having patients lose weight before having knee replacement surgery will automatically improve outcomes is questioned.

In a California study, only 12.4% of more than 10,000 knee replacement patients studied and 18% of more than 4000 hip replacement patients  managed to lose at least 5% of their starting weight in the year before their surgery. Around 75% of both groups stayed stable. Those who did manage to lose weight before knee replacement surgery did no better than those who did not lose weight before surgery. They had similar rates of surgical site infections and re-admissions for complications.

This certainly calls into question how helpful weight loss supposedly is before knee replacement.

In a companion study, those who lost weight before joint replacement surgery and managed to keep it off afterwards actually did worse than those whose weight stayed stable. The weight loss knee replacement group had more hospital re-admissions than those who did not lose weight. Furthermore, the hip replacement group who lost weight had more deep-site surgical infections. The authors noted:

These findings raise questions about the safety of weight management before total replacement of the hip and knee joints.

Why this increase in infections occurred is not clear. One theory is that when people are placed on a significantly low-calorie diet, nutrition can be impaired. It is difficult to get the proper amounts of all the nutrients when caloric intake is too low, and diets for these mobility-impaired people are often quite low-calorie because increasing exercise is difficult. As a result, some people with significant weight loss or chronic dieting histories develop nutrient deficiencies, and these may impair immune function. Research confirms that people with nutrient deficiencies have a greater risk for infections and other complications after joint surgery.

So while weight loss may reduce stress on the joint, nutrient deficiencies from this weight loss may affect immune function and ability to "bounce back" after surgery, negating any potential benefits of weight loss.

Furthermore, many people who lose substantial weight before joint replacements gain back that weight and more after the surgery. The end result of weight loss before joint replacement may be that the patient ends up weighing MORE later on, as one study found:

A patient with [hip replacement] had increased risk of important post-surgical weight gain of 12% (OR = 1.12, 95% CI, 1.08, 1.16) for every kilogram of pre-operative weight loss...Patients less than 60 years and who have lost a substantial amount of weight prior to surgery appear to be at particularly high risk of important post-surgical weight gain.

Ironically, requiring or strongly encouraging patients to lose a substantial amount of weight prior to joint replacement may backfire and ultimately add to the patient's weight, not lessen it. Yet most doctors continue to demand weight loss before joint replacement. Only now the emphasis is on weight loss via bariatric surgery instead.

Quote from Ragen Chastain, found here.

What About Bariatric Surgery First?

Because bariatric surgery is one of the only ways to lose weight in the long term (though it comes with many other complications and ususally involves some weight regain), many orthopedic surgeons are forming de-facto partnerships with bariatric surgeons.

As a result, many people of size are effectively blackmailed into weight loss surgery by BMI restrictions on joint replacements. 

One study from the Mayo Clinic states, "Morbidly obese individuals with severe degenerative joint disease who are considered unsuitable for arthroplasty because of excess weight should be considered for bariatric surgery."

Another surgeon reports that he accepts patients for knee replacements up to a BMI of 50, but after that he refers them for bariatric surgery first. (Because it makes SO much sense for someone too "at-risk" for one type of surgery to undergo a different type of surgery instead.)

Yet the common assumption that bariatric surgery should be promoted because it would surely improve outcomes in "morbidly obese" patients with significant osteoarthritis should also be questioned.

Some research does indicate improved outcomes in those who had bariatric surgery before joint replacement. And one recent study that looked only at short-term (90 days!) complications found lower rates of complications in those who had had bariatric surgery. Of course, the media was all over this study and it has been widely cited to justify requiring weight loss surgery.

However, other research does not support better outcomes with bariatric surgery, yet the press conveniently ignores that. In one study, complications were actually higher in the group with recent bariatric surgery (less than 2 years). The authors concluded:

Bariatric surgery prior to TJA [Total Joint Arthroplasty] may not provide dramatic improvements in post-operative TJA surgical outcomes. 

In another study from a major research hospital, researchers found an increased rate of joint replacements in bariatric patients who had experienced large or very rapid weight loss. They noted, "These results contradict the tenant that weight loss is universally protective against arthritis and merit larger prospective investigations."

Another recent study did not find improved outcomes in those who had had bariatric surgery before joint replacement. Indeed, many had worse outcomes instead, needing more revision surgeries afterwards.

This was echoed in a recent large retrospective cohort study that found worse outcomes in the group that had bariatric surgery first, compared to high-BMI people who did not. The WLS group had more infection, pneumonia, blood clots, heart issues, revisions, and manipulations of the prosthetetic.

A recent meta-analysis found no significant benefit from bariatric surgery before joint replacement. The authors concluded:

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.

It may be that the potential benefits of reducing the load on the joint via weight loss from bariatric surgery may be outweighed by the nutrient deficits that are so common after weight loss surgery, even non-restrictive procedures. It may also be that the stresses on the body from rapid weight loss cause long-term damage to the body's ability to repair itself.

While some bariatric surgery patients have good outcomes and health improvement from the WLS, others have terrible outcomes, with significant nutritional deficits (sometimes despite supplements) and physical health problems. Some even die from the surgery or its after-effects. The problem is that you don't know which outcome group you are going to be in until after you've had the surgery. To strongly pressure joint replacement patients into bariatric surgery first means doctors are engaging in a high-stakes gamble with their patients' lives and quality of life.

And if joint replacement surgery at larger sizes is "too dangerous," why isn't weight loss surgery at larger sizes also too risky? Funny how patients are too fat for one surgery but surgeons can't wait to usher them into the Operating Room for WLS.

There are good reasons to question the common recommendation to have bariatric surgery before joint replacement. WLS is dangerous in and of itself, it often results in significant long-term nutrient deficits and other health problems, and it may not improve long-term outcomes for joint replacement.

However, as always, every person gets to make their own health decisions. Some people choose to have bariatric surgery before joint replacement and they have the right to do that. Others choose not to, and they also should have the right to do that. It's a choice with many pros and cons but one that should not be forced upon someone, which many doctors are essentially doing by denying joint replacement without bariatric surgery first.

In the past, care providers rarely studied whether or not bariatric surgery actually improved outcomes; they just assumed it will because it seems logical. But recent research shows there is good reason to question whether bariatric surgery really improves long-term outcome after all.

Mitigating Risk Through Better Management

Critics will no doubt point out that the risk for blood clots and post-operative infection are higher in obese patients and this is why they are concerned about operating on this group. This is true, and obese patients should be counseled about this fact. For example, one study found 6.7x the risk for infection in obese knee replacement patients, and 4.2x the risk for infection in obese hip replacement patients. The risk for infection is particularly strong among diabetics with a BMI over 40.

However, remember the dangers of using relative risk to discuss risk/benefit ratios; it can distort one's perception of risk. It is more helpful to use absolute numerical values so the magnitude of risks patients are assuming is more clear. One very large British study found that for knee replacements, risk for blood clots was increased from 2.0% to 3.3% and risk for infection from 3.0% to 4.1%, in obese patients with total knee replacements. For hip replacements, the risk for blood clots was increased from 2.2% to 3.3% and the risk for infection from 1.6% to 3.5% in obese patients. The authors noted (my emphasis):

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, the most important thing to point out is that an increased infection and clotting risk may be at least partly due to mismanagement of obese patients. Re-examining and changing the management protocols of these patients may improve outcomes independent of weight loss. 

For example, research shows that obese patients are chronically under-dosed with many medications. This is particularly relevant in antibiotics for preventing and treating infections, and in thromboprophylaxis medications for preventing blood clots after surgery. In other words, the two biggest risks of surgery in high-BMI patients may actually be largely preventable.

Obese patients, especially "morbidly-obese" (BMI 40+) and "super-obese" (BMI 50+) patients, are at particular risk for infections and may require larger initial antibiotic doses, extended or more frequent dosing regimens, use of more than one type of antibiotic, and perhaps topical infusions of antibiotics during surgery. This may help reduce their increased risk for infection after joint replacement surgery.

One recent study on infection in obese joint replacement patients strongly raised this issue of antibiotic underdosing. The authors found that above 100 kg (~220 lbs.), the rate of infections rose strongly. They noted that most patients in the study, regardless of BMI, were treated with a uniform dose (1.5g) of pre-op antibiotics and speculated that an increased antibiotic dose would help lower the rate of infections in this group. They stated:

The link between obesity and infection may be explained by several factors, but under-dosing of antibiotics is probably the most important to consider.

They also noted that noted that research examining the question of proper antibiotic dosage for obese patients undergoing joint replacement surgery was lacking. The problem of underdosing antibiotics in obese patients has been acknowledged in obstetric and bariatric surgery for several years. Why is it only NOW being brought up in orthopedic surgery?

Underdosing issues go beyond antibiotics. Research suggests that many obese patients are under-dosed with anti-clotting agents like heparin. One study found that weight-adjusted dosing cut the rate of blood clots in obese patients after surgery from 2.0% to 0.54% without increasing the risk for bleeding. Another study found that an extended prophylaxis period of anti-clotting agents lowered the risk for clots significantly, also without increasing bleeding.

Other surgical management protocols for obese patient need review as well. Some research suggests that surgical drains, often placed prophylactically in obese patients, have no benefit or may actually do more harm than good. Although further research is needed, one research review suggested omitting routine surgical drains in obese patients during joint replacement surgery.

As noted previously, another very interesting set of recent studies suggests that "morbid obesity" is less important that serum albumin levels on major complications like mortality and infections in joint replacement surgery. Serum albumin levels are an indicator of liver and kidney function but can also indicate nutrition status; obese people may be more at risk for malnutrition because of chronic dieting, highly restrictive intakes, or malabsorptive procedures like gastric bypass. Improving joint replacement outcomes might need to focus on measuring and fixing albumin levels and other nutrient deficits before surgery.

Bottom line, if the real concern is preventing poor outcomes, then perhaps the best approach is not to deny all high-BMI patients access to this surgery, but rather to lower morbidity by improving care for them instead via:

• Utilizing weight-based dosing more uniformly in antibiotics and blood clot prevention drugs 
• Using extended, adjunctive or more frequent antibiotic dosing regimens 
• Avoiding routine prophylactic surgical drains 
• Screening for and optimizing albumin and other nutrient levels before surgery

Ironically, a lot of the research on improving surgical outcomes in very obese patients is only done with bariatric surgery. It is past time to improve outcomes in high-BMI people in other types of surgery as well, including joint replacement surgery, instead of having to just extrapolate from bariatric surgery studies.

We need to know through evidence-based trials what the best protocols are for obese people undergoing joint replacement surgery. And in order to do that, we need for people of size to actually be given access to this surgery.

Summary

Sadly, even today, many orthopedic surgeons 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 do this because surgery is more technically challenging in very heavy people and because they view obesity as a voluntary condition brought on by poor lifestyle choices. They feel that losing weight is mostly a matter of willpower and choices, despite plenty of evidence to the contrary, and they feel they are doing their patients a favor by making them lose weight.

Surgeons also justify BMI restrictions 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 and/or requiring weight loss or even bariatric surgery before joint replacement.

However, other surgeons are questioning the ethics of denying joint replacement surgery to high-BMI patients. They note that even very fat patients usually have good long-term outcomes from the surgery.

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. Many are willing to proceed with joint replacement surgery in high-BMI patients as long as they have been given informed consent about the benefits and risks.

It is reasonable to counsel obese patients about the potential risks of a higher weight before surgery, especially if they have co-morbidities like diabetes. However, the counseling should cover both risks and benefits. It should acknowledge that the magnitude of risk is relatively modest in most obese patients and that most have very good long-term results from both knee replacement surgery and hip replacement surgery.

Patients can also be counseled about the potential benefits of weight loss before joint replacement surgery, as long as the data used is realistic and the potential risks of weight loss are also covered. But weight loss should not be required in order to access such surgery because research is contradictory on whether this is helpful. Short-term research shows some benefits, but longer-term research shows little benefit and sometimes even harm. Furthermore, the risks of weight loss, yo-yo dieting, and bariatric surgery should not be overlooked. More research is needed, but requiring weight loss before surgery is certainly not evidence-based. The truth is that the evidence is mixed and the choice should be left to the patient.

Joint replacement surgery in very obese patients is technically harder and does carry risks. However, the magnitude of this risk is modest and the potential for improvement in quality of life is very strong. Restricting high-BMI people from joint replacement surgery or requiring them to lose weight in order to access this surgery is NOT justified or ethical.

Rather, the risks are a call to surgeons to further examine the long-overlooked issue of how they manage obese patients. Risks can most likely be mitigated by proper medication dosing and more optimal surgical management of high-BMI patients.

Instead of restricting joint replacement or requiring weight loss in high BMI patients, orthopedic surgeons should be focusing on how they can improve outcomes in this group through modifications to surgical management protocols.


References

General Information about Joint Replacement

• http://orthoinfo.aaos.org/topic.cfm?topic=a00389 - knee replacement info
• http://orthoinfo.aaos.org/topic.cfm?topic=a00377 - hip replacement info

Weight Loss Before Joint Replacement

Bone Joint J. 2014 May;96-B(5):629-35. doi: 10.1302/0301-620X.96B5.33136. The risk of surgical site infection and re-admission in obese patients undergoing total joint replacement who lose weight before surgery and keep it off post-operatively. Inacio MC, Kritz-Silverstein D, Raman R, Macera CA, Nichols JF, Shaffer RA, Fithian DC. PMID: 24788497

This study evaluated whether obese patients who lost weight before their total joint replacement and kept it off post-operatively were at lower risk of surgical site infection (SSI) and re-admission compared with those who remained the same weight. We reviewed 444 patients who underwent a total hip replacement and 937 with a total knee replacement who lost weight pre-operatively and sustained their weight loss after surgery. After adjustments, patients who lost weight before a total hip replacement and kept it off post-operatively had a 3.77 (95% confidence interval (CI) 1.59 to 8.95) greater likelihood of deep SSIs and those who lost weight before a total knee replacement had a 1.63 (95% CI 1.16 to 2.28) greater likelihood of re-admission compared with the reference group. These findings raise questions about the safety of weight management before total replacement of the hip and knee joints.

J Arthroplasty. 2014 Mar;29(3):458-64.e1. doi: 10.1016/j.arth.2013.07.030. Epub 2013 Sep 7. The impact of pre-operative weight loss on incidence of surgical site infection and readmission rates after total joint arthroplasty. Inacio MC, Kritz-Silverstein D, Raman R, Macera CA, Nichols JF, Shaffer RA, Fithian DC. PMID: 24018161

This study characterized a cohort of obese total hip arthroplasty (THA) and total knee arthroplasty (TKA) patients (1/1/2008-12/31/2010) and evaluated whether a clinically significant amount of pre-operative weight loss (5% decrease in body weight) is associated with a decreased risk of surgical site infections (SSI) and readmissions post-surgery. 10,718 TKAs and 4066 THAs were identified. During the one year pre-TKA 7.6% of patients gained weight, 12.4% lost weight, and 79.9% remained the same. In the one year pre-THA, 6.3% of patients gained weight, 18.0% lost weight, and 75.7% remained the same. In TKAs and THAs, after adjusting for covariates, the risk of SSI and readmission was not significantly different in the patients who gained or lost weight pre-operatively compared to those who remained the same.

Osteoarthritis Cartilage. 2013 Jan;21(1):35-43. doi: 10.1016/j.joca.2012.09.010. Epub 2012 Oct 6.
Clinically important body weight gain following total hip arthroplasty: a cohort study with 5-year follow-up. Riddle DL, Singh JA, Harmsen WS, Schleck CD, Lewallen DG. PMID: 23047011

...DESIGN: We used multi-variable logistic regression to compare data from one of the largest US-based THA registries to a population-based control sample from the same geographic region. We also identified factors that increased risk of clinically important weight gain specifically among persons undergoing THA. The outcome measure of interest was weight gain of ≥5% of body weight up to 5 years following surgery. RESULTS: ...A patient with THA had increased risk of important post-surgical weight gain of 12% (OR = 1.12, 95% CI, 1.08, 1.16) for every kilogram of pre-operative weight loss. CONCLUSIONS: While findings should be interpreted with caution because of missing follow-up weight data, patients with THA appear to be at increased risk of clinically important weight gain following surgery as compared to peers. Patients less than 60 years and who have lost a substantial amount of weight prior to surgery appear to be at particularly high risk of important post-surgical weight gain. 

Arthritis Care Res (Hoboken). 2013 May;65(5):669-77. doi: 10.1002/acr.21880. Clinically important body weight gain following knee arthroplasty: a five-year comparative cohort study. Riddle DL, Singh JA, Harmsen WS, Schleck CD, Lewallen DG. PMID: 23203539

...METHODS: We used one of the largest US-based knee arthroplasty registries and a population-based control sample from the same geographic region to determine whether knee arthroplasty increases the risk of clinically important weight gain of ≥5% of baseline body weight over a 5-year postoperative period. RESULTS: Of the persons in the knee arthroplasty sample, 30.0% gained ≥5% of baseline body weight 5 years following surgery as compared to 19.7% of the control sample. The multivariable-adjusted (age, sex, body mass index, education, comorbidity, and presurgical weight change) odds ratio (OR) was 1.6 (95% confidence interval [95% CI] 1.2-2.2) in persons with knee arthroplasty as compared to the control sample. Additional arthroplasty procedures during followup further increased the risk for weight gain (OR 2.1, 95% CI 1.4-3.1) relative to the control sample. Specifically, among patients with knee arthroplasty, younger patients and those who lost greater amounts of weight in the 5-year preoperative period were at greater risk for clinically important weight gain. CONCLUSION: Patients who undergo knee arthroplasty are at an increased risk of clinically important weight gain following surgery. The findings potentially have broad implications to multiple members of the health care team. Future research should develop weight loss/maintenance interventions particularly for younger patients who have lost a substantial amount of weight prior to surgery, as they are most at risk for substantial postsurgical weight gain.

Bariatric Surgery Before Joint Replacement 

Bone Joint J. 2015 Nov;97-B(11):1501-5. doi: 10.1302/0301-620X.97B11.36477. Bariatric surgery does not improve outcomes in patients undergoing primary total knee arthroplasty. Martin JR, Watts CD, Taunton MJ. PMID: 26530652

Bariatric surgery has been advocated as a means of reducing body mass index (BMI) and the risks associated with total knee arthroplasty (TKA). However, this has not been proved clinically. In order to determine the impact of bariatric surgery on the outcome of TKA, we identified a cohort of 91 TKAs that were performed in patients who had undergone bariatric surgery (bariatric cohort). These were matched with two separate cohorts of patients who had not undergone bariatric surgery. One was matched 1:1 with those with a higher pre-bariatric BMI (high BMI group), and the other was matched 1:2 based on those with a lower pre-TKA BMI (low BMI group). In the bariatric group, the mean BMI before bariatric surgery was 51.1 kg/m(2) (37 to 72), which improved to 37.3 kg/m(2) (24 to 59) at the time of TKA. Patients in the bariatric group had a higher risk of, and worse survival free of re-operation (hazard ratio (HR) 2.6; 95% confidence interval (CI) 1.2 to 6.2; p = 0.02) compared with the high BMI group. Furthermore, the bariatric group had a higher risk of, and worse survival free of re-operation (HR 2.4; 95% CI 1.2 to 3.3; p = 0.2) and revision (HR 2.2; 95% CI 1.1 to 6.5; p = 0.04) compared with the low BMI group. While bariatric surgery reduced the BMI in our patients, more analysis is needed before recommending bariatric surgery before TKA in obese patients.

J Arthroplasty. 2016 Sep;31(9 Suppl):207-11. doi: 10.1016/j.arth.2016.02.075. Epub 2016 Mar 15. Lingering Risk: Bariatric Surgery Before Total Knee Arthroplasty. Nickel BT, Klement MR, Penrose CT, Green CL, Seyler TM, Bolognesi MP. PMID: 27179771

...METHODS: A total of 39,014 patients were identified in a claim-based review of the entire Medicare database with International Classification of Diseases, Ninth Revision codes to identify patients in 3 groups. Patients who underwent BS before total knee arthroplasty (group I: 5914 experimental group) and 2 control groups that did not undergo BS but had either a body mass index >40 (group II: 6480 bariatric control) or <25 (group III: 26,616 normal weight control)...RESULTS: ...Medical and surgical complication incidences were greatest in group I including: 4.98% deep vein thrombosis; 5.31% pneumonia; 10.09% heart failure; and 2-year infection, revision, and manipulation rates of 5.8%, 7.38%, and 3.13%, respectively. These values were significant elevation compared to III and slightly greater than II. CONCLUSIONS: This study demonstrates that BS before total knee arthroplasty is associated with greater risk compared to both nonobese and obese patients. This is possibly due to a higher incidence of medical or psychiatric comorbidities determined in the Medicare BS patients, wound healing difficulties secondary to gastrointestinal malabsorption, malnourishment from prolonged catabolic state, rapid weight loss before surgery, and/or age.

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...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. 

Other Possible Factors

Clin Orthop Relat Res. 2015 Oct;473(10):3163-72. doi: 10.1007/s11999-015-4333-7. Epub 2015 May 21. Low Albumin Levels, More Than Morbid Obesity, Are Associated With Complications After TKA. Nelson CL1, Elkassabany NM, Kamath AF, Liu J. PMID: 25995174

BACKGROUND: Morbid obesity and malnutrition are thought to be associated with more frequent perioperative complications after TKA. However, morbid obesity and malnutrition often are co-occurring conditions. Therefore it is important to understand whether morbid obesity, malnutrition, or both are independently associated with more frequent perioperative complications...METHODS: The National Surgical Quality Improvement Program (NSQIP) database was analyzed from 2006 to 2013. Patients were grouped as morbidly obese (BMI ≥ 40 kg/m(2)) or nonmorbidly obese (BMI ≥ 18.5 kg/m(2) to < 40 kg/m(2)), or by low serum albumin (serum albumin level < 3.5 mg/dL) or normal serum albumin (serum albumin level ≥ 3.5 mg/dL)...RESULTS: Mortality was not increased in the morbidly obese group (0.14% vs 0.14%; p = 0.942)...The group with low serum albumin had higher mortality than the group with normal serum albumin (0.64% vs 0.15%; OR, 3.17; 95% CI, 1.58-6.35; p =0.001)... CONCLUSIONS: Morbid obesity is not independently associated with the majority of perioperative complications measured by the NSQIP and was associated only with increases in progressive renal insufficiency, superficial surgical site infection, and sepsis among the 21 perioperative variables measured. However, low serum albumin was associated with increased mortality and multiple additional major perioperative complications after TKA. Low serum albumin, more so than morbid obesity, is associated with major perioperative complications. This is an important finding, as low serum albumin may be more modifiable than morbid obesity in patients who are immobile or have advanced knee osteoarthritis.

HSS J. 2017 Feb;13(1):66-74. doi: 10.1007/s11420-016-9518-4. Epub 2016 Aug 16. Hypoalbuminemia Is a Better Predictor than Obesity of Complications After Total Knee Arthroplasty: a Propensity Score-Adjusted Observational Analysis. Fu MC, McLawhorn AS, Padgett DE, Cross MB. PMID: 2816787

...METHODS: TKA cases were identified from the National Surgical Quality Improvement Program from 2005 to 2013... Malnutrition was defined as hypoalbuminemia (<3.5 g/dL). Patients were classified by BMI as follows: non-obese (18.5-29.9), obese I (30-34.9), obese II (35-39.9), or obese III (≥40). Postoperative complications were compared across obesity and nutritional statuses. Multivariable propensity-adjusted logistic regressions were performed to determine associations between malnutrition, obesity, and 30-day outcomes. RESULTS: There were 71,599 cases identified, with 34,800 (48.6%) having albumin measurements...Malnutrition prevalence increased with BMI (6.1% in obese III vs. 3.7% in non-obese). With propensity-adjusted multivariable analysis, obese III was the only obesity class associated with any complication, wound complication, and reoperation. Hypoalbuminemia was a stronger and more consistent independent risk factor, for any complication, wound, cardiac, or respiratory complications, and death. CONCLUSIONS: Hypoalbuminemia is a more consistent independent predictor of complications after TKA than obesity. Strategies for medical optimization of these conditions should be investigated.

Antibiotic Dosing and Surgical Infections

Acta Orthop. 2016;87(2):132-8. doi: 10.3109/17453674.2015.1126157. Epub 2016 Jan 5. Body mass and weight thresholds for increased prosthetic joint infection rates after primary total joint arthroplasty. Lübbeke A1, Zingg M1, Vu D2, Miozzari HH1, Christofilopoulos P1, Uçkay I1,2, Harbarth S3, Hoffmeyer P1. PMID: 26731633

...We included all 9,061 primary hip and knee arthroplasties (mean age 70 years, 61% women) performed between March 1996 and December 2013 where the patient had received intravenous cefuroxime (1.5 g) perioperatively. The main exposures of interest were BMI (5 categories: < 24.9, 25-29.9, 30-34.9, 35-39.9, and ≥ 40) and weight (5 categories: < 60, 60-79, 80-99, 100-119, and ≥ 120 kg). Numbers of TJAs according to BMI categories (lowest to highest) were as follows: 2,956, 3,350, 1,908, 633, and 214, respectively. The main outcome was prosthetic joint infection. The mean follow-up time was 6.5 years (0.5-18 years). RESULTS: 111 prosthetic joint infections were observed: 68 postoperative, 16 hematogenous, and 27 of undetermined cause. Incidence rates were similar in the first 3 BMI categories (< 35), but they were twice as high with BMI 35-39.9 (adjusted HR = 2.1, 95% CI: 1.1-4.3) and 4 times higher with BMI ≥ 40 (adjusted HR = 4.2, 95% CI: 1.8-9.7). Weight ≥ 100 kg was identified as threshold for a significant increase in infection from the early postoperative period onward (adjusted HR = 2.1, 95% CI: 1.3-3.6). INTERPRETATION: BMI ≥ 35 or weight ≥ 100 kg may serve as a cutoff for higher perioperative dosage of antibiotics.

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"
• https://www.peerwell.co/blog/2017/05/11/have-to-lose-weight-before-joint-replacement/ - "Told to Lose Weight Before a Joint Replacement Surgery? Here's Why"