Too Heavy for a Joint Replacement?

One of the most difficult conversations orthopedic surgeons have with patients is telling them they are too big for joint replacement surgery. This is becoming far more common as nearly 1 in 3 adults are overweight. Because of this, many surgeons have adopted a Body Mass Index (BMI) to evaluate a patient’s potential for this type of surgery. BMI is a tool used to compare an individual's height and weight and is calculated by a person's weight in kilograms divided by the square of height in meters. In recent years, many surgeons have adopted a cut off of a BMI of 40 joint replacements. For some, this is a surgeon's personal choice, but for others the choice is made by their hospital system, insurance companies, or local standard of care. 

You can use the following chart to determine your own BMI:

Recently BMI has come under criticism. The reason is it is not always accurate in depicting someone’s composition. For example, a muscular person may be considered overweight by BMI measure. Just look up the BMI of your favorite all-pro linebacker and they would likely be considered overweight due to muscle mass even with minimal body fat. Race also plays a role in skewing BMI measurements as certain races may be heavier due to increased bone density or muscle mass. Additionally, there are social implications linked to a higher BMI such as lack of proper nutrition, less opportunities for fitness, and high levels of stress. 

Although these criticisms are valid, they are not necessarily relevant to the joint replacement surgeon. The reason is that a BMI of 40 is at the extreme end of the obesity scale. Theoretically, it could be possible to be so muscular you reach this level, but it is an unlikely scenario in the ordinary orthopedic patient. For reference, a BMI of 30-35 is considered obese, a BMI of 35-40 is considered severe obesity, and a BMI above 40 is considered morbid obesity. Before continuing this discussion, I would like to point out that even a patient at their ideal weight who undergoes joint replacement surgery is accepting the risk of a bad outcome. Research shows that only 80-90% of patients are happy with their knee replacement. The risk of surgery increases slightly with a BMI over 30 but increases significantly with a BMI over 40. At a BMI above 40 the risk may outweigh the benefits. According to the OKU 14 (Orthopedic Knowledge Update), the increased complications occur throughout the perioperative period which is the 3-6 months after surgery, but could be longer until full recovery is reached. Obesity leads to increased sleep apnea and decreased lung volumes which increases the chance of respiratory complications. Obese patients are at a higher risk for deep venous thrombosis (blood clots) which can lead to dangerous or fatal pulmonary embolism. The increased size of the patient makes regional anesthesia more difficult for the anesthesiologist. This means the nerve blocks to numb the extremity are more likely to fail which results in increased postoperative pain. This results in a higher need for pain medicine which could lead to further complications. The extra soft tissue presents surgical challenges that could result in malalignment of the prosthesis which leads to a poor surgical outcome. The increased soft tissue also causes an increased risk of wound healing issues including increased bleeding and drainage. Ultimately this leads to an increase in infection rates. Infections often lead to resection of the joint replacement and prolonged antibiotics followed by a revision replacement. In some individuals the infection can only be eradicated with an amputation. Despite the increased comparative risk, heavier patients can still have great results from joint replacement. If you do your own research you will find some who argue that using a BMI cutoff of 40 is arbitrary and unfair. 

A simple YouTube or google search will show you information that reports you do not need to lose weight before joint replacement surgery.

What is a patient to do with this conflicting data? First, you simply need to be aware of the increased risk of medical complications in the perioperative period due to your weight. Second, you need to be aware of the potential for surgical issues which include infection, malalignment or loosening of the prosthesis due to your weight. Finally, you need to be aware that revision surgery is far more complicated than your original joint replacement. Far too many patients think a revision surgery is like changing a part in a car engine. In reality, it is much more complicated. When you remove the first joint, the surgeon has less bone to work with when they put in the second joint. This makes performing a “perfect” surgery more difficult which increases the chance of further complications. The second surgery thus has a higher chance of infection which would result in removing the joint once again, having to place the patient on antibiotics, and starting over with trying a third joint replacement. These could lead to a patient spending years trying to recover from an infected joint arthroplasty. Another factor you should be aware of is that many regions have surgeons who specialize in revision joint replacement. This is a subspeciality of joint arthroplasty. These surgeons actually prefer these difficult or often called “disaster revision cases”. Some of the best and busiest joint replacement surgeons do not do revisions. In reality, a good joint surgeon would have very few patients who need revisions. In this case they may feel you are better off being transferred to a surgeon who specializes in revisions and therefore does many. If your surgeon does revisions he may only need to do one every few years versus putting you in the hands of someone who does several a week. In other words every joint surgeon in your region may funnel most of their patients who need a revision to a handful of subspecialists who usually work at large medical centers. 

Why is this important? From the surgeon's perspective, if the regional revision specialist does not do joint replacements in patients with a BMI over 40 your surgeon will likely feel obligated to stick with this same cutoff. In this way your surgeon is self policing. Your local hospital system may or may not have a firm BMI cutoff, but they certainly track complications and length of stay. Many joint replacements now go home the day of surgery, but each patient with an elevated BMI is less likely to be able to go home safely the same day. As discussed these patients are more likely to have complications. If a surgeon has a high length of stay or high levels of complications the hospital will encourage them to change the way they practice. The surgeon could even lose their privilege to work at the hospital. The surgeon is also tracked by insurance companies, and a higher complication rate could result in a decrease in referrals. Many of these factors restricting joint replacement have become more important in recent years. This can be frustrating for patients who know others who are heavy but happy with their surgical result. 

Taking all these factors into account, my opinion is you should make an exhaustive effort to lose weight before proceeding with joint replacement. Although you may benefit from a new joint at your current weight you will significantly decrease your chance of a complication at a lower BMI. In addition, you will make the job easier not only for your surgeon but the anesthesiologist, nurses, and physical therapists as well. Most importantly, if you are unfortunate and need a revision you will make things easier on the revision specialist which gives you an increased chance of a successful outcome. I mentioned at the beginning that this is a difficult conversation to have with patients. The reason is because most physicians are aware the patient has had many factors going against them that led to their obesity. As physicians, we are presented with a patient who has likely struggled with weight the majority of their life and is now in severe pain and we are denying them the one thing that could help relieve this pain. Many patients are convinced at this point that nothing will help them lose weight. On the other hand the surgeon likely sees many patients in the same situation including patients who have lost 100 pounds or more. If those patients succeeded in losing the weight they may believe you can as well.

“ Those who say it can’t be done are usually interrupted by others doing it.”
- James Baldwin

Life is a team game. If you have tried and failed to lose weight you need a team. My hope is all joint centers will soon have teams to help patients who are too heavy for joint replacement surgery. Until that time comes, you will need to make your own team. Start with your primary care physician to determine if there's anything medically that could be causing your weight gain such as a slowed metabolism and if there is anything to combat it. Additionally, you need a nutritionist to make sure you are eating the right things. So many of us are stuck with the eating habits we learned as a child when nutritional information was limited. You need a physical therapist who can help design a fitness program around your physical limitations and you may need a personal trainer to help implement them. A psychologist or therapist would be critical  if stress, mental health, or past trauma is interfering with your weight loss.

Finally, as orthopedic surgeons we need to make sure our patient populations are aware that elevated BMI is a concern when considering joint replacement. I prefer to let patients know at the onset of conservative care that joint replacement could be in their future. It is never an absolute however. We see many patients with damaged joints who have great success with conservative care and never need surgery. Our goal should be to avoid waiting until a patient decides they would like to proceed with surgery to inform them they need to lose weight. This denies them the opportunity to work on their weight while their joint pain is controlled by conservative care. Medical, nutritional, and fitness science is always evolving. No patient should be without hope that they can get a great result from joint replacement surgery. The goal of every patient and physician should be to wait until the patient's health, including weight, is optimized before proceeding with what is hopefully definitive care.