In an article published in the May 2017 edition of Journal of Arthroplasty, authors Fehring, et al, describe their experience with total knee tibial component loosening in obese individuals. What they found is that patients with a BMI greater than 35 placed increased strain on the bone in the proximal or top part of the shin bone (tibia). Due to the fact that the majority of these patients were female with an elevated BMI, the bone size does not match the weight of the patient. Therefore, the amount of stress placed on the bone exceeds the strength of the bone. This led to catastrophic loosening of the implant and need for revision. This is a situation that has been recognized over the last several years and led orthopedic surgeons to use longer stems on the implant that is placed in the shin bone. This is thought to be advantageous in individuals with elevated weight and smaller bone size to help offload the stress at the top of the bone.
The authors point out that these findings of increased failure rate in individuals with elevated weight and smaller bones sheds light on the need to optimize patients before surgery to get their weight to a more acceptable level, and, if this is not possible, using longer stemmed implants to try and dissipate the loads placed on the top part of the bone.
This is yet another example of the need to optimize patients physical and mental health prior to joint replacement surgery, and to also alter our surgical technique to try and accommodate some of these challenges.
Dr. Barrett is an orthopedic surgeon who performs over 500 joint replacement surgeries annually. For more information about total hip and knee replacements, contact Proliance Orthopedic Associates at 425.656.5060.