Obesity, my friends, is on the rise and we are going to see
more and more such patients in the near future. Obesity means arthritis,
especially of the knee, is going to happen at an earlier age.
‘A morbidly obese
patient posted for a TKR’ – just the idea causes anxiety. It doesn’t require a
genius to figure out that such a surgical exercise is hugely difficult. But as
I was going through literature I realised that there are so many more issues with
obesity than just technical hardship. It is imperative that we as surgeons are
aware of these issues and it is our duty to warn our patients of these concerns
before we take on this humongous challenge.
I always thought that obese patients with bad knees would
have a tough time losing weight. Once the knee had been replaced then they
would be able to lose it. But Pritchett JW et al have shown that TKR does not
facilitate weight reduction.
Though an improvement in knee score does occur after TKR in
morbidly obese, it is less than in non obese patients. In short even though
morbidly obese patients benefit from TKR, we cannot expect the fantastic
results that we see in thinner patients. Foran JR et al reported in 2004 that
any degree of obesity (defined as BMI > or = 30) compromised the result of
TKR.
Obesity results in
more technical errors during knee replacement surgery. I found some technical
tips while reviewing literature. I invite comments on more technical tips
from my readers. There is little place for MIS in the morbidly obese. One should
use large incisions. Patella eversion is often not possible. It is better to
just subluxate the patella. A tourniquet may be difficult to apply and may fail
to work. One should be prepared to do the surgery without tourniquet. Fractures
occur more commonly while operating on these patients. One should keep a set of
screws and stemmed implants ready to deal with such an eventuality. Similarly
ligament injuries are more common especially to the medial collateral ligament.
One should be ready with a semiconstrained option.
An excellent review by Samson et al from Australia opened my
eyes on the complications faced by this patient population. These patients are
at a higher risk for wound complications. This has been attributed to poor
oxygenation of adipose tissue, increased wound tension and underlying endocrine
disorders like diabetes. These patients also have a 3 to 9 times greater risk
of deep prosthetic infection. And we all
know what that means. To add to this is the increased risk of damage to MCL and
introp fractures as already mentioned.
And last but not the
least, TKR in the morbidly obese results in reduced survival of the prosthesis and earlier revision (not conclusively proven)
In view of so many problems, some centres advocate bariatric surgery before undergoing knee replacement. Even though there is no conclusive
data, early results are very encouraging for this approach.
To conclude, TKR in obese and definitely in morbidly obese
is a different ball game. Functional results and prosthesis survival are poorer and complications are higher. We need
to discuss these issues in detail with the patient. We also need to better prepared
for controlling co morbidities preoperatively, for handling intraoperative
complications and for anticipating and managing postoperative issues. We may be
forced to think of bariatric surgery before TKR in this patient group in the near
future.
