Abstract
Obesity has been associated with degenerative osteoarthritis of knee joint The over all incidence of osteoarthritis of the knee is also more in patients with obesity. Increasing obesity leads to faster progression of OA, which is due to increased joint load. Body mass index (BMI), dividing an individual’s weight (in kg) by his or her height (in square meters). BMI: Normal = 18.5 to 24.9, Overweight BMI −25–29.9 Obese=30 to 39.9, Morbidly Obese BMI 40 or Greater. Recent article focused on the thigh girth of obese patients and opined that if thigh girth > 55cms, subvastus approach should not be utilized, as it is difficult to evert the patella. We believed that obesity should not really cause a problem for the patients undergoing a TKA with the mini subvastus approach as the anatomy of the quadriceps in the obese and the non-obese patient population is the same. We decided to evert the patella only after osteotomy of tibia and the femur.
All patients who underwent primary total knee arthroplasty with minisubvastus approach between January 2006 to July 2007 and who were obese (BMI> 30) were included in our study. Out of 425 primary Total knee arthroplasty were performed during this period. Out of these, there were total 97 obese patients with 109 knees which form the part of the study.
There were 81 females and 16 males and 12 patients had staged bilateral knee arthroplasty. The weight varied from 63 to 125 kgs. 91 patients had varus deformity of < 15 degree, 15 patients had varus deformity of > 15 degree, 3 patients had valgus deformity. The thigh girth in obese group (BMI: 30–40) ranged from 45 to 58 cms with average of 50.17. The thigh girth in morbidly obese (BMI > 40) group ranged between 55 to 67 with average of 61.01 cms.
Mini-subvastus approach provided satisfactory exposure in all knees that were operated. In no case was this approach abandoned.
The average surgical time was 90 minutes with range. The average blood loss was 400 cc. The patellar tracking was immaculate in every case and in fact it was difficult to displace patella laterally after 30 degrees of knee flexion. Our 89 patients had flexion of > 120 0,and 20 patients had flexion of > 90 but < 120. The knee society score improved from average 42 (range 17–62) preoperatively to 89 (range 72–95) post operatively. The Knee Society functional score improved from 48 (range 15–60) pre operatively to 65 (range 50–80) post operatively.
Mini subvastus approach offers adequate intraoperative exposure even in obese and morbidly obese patients. It did not result in increased complications in our hands even in morbidly obese patients with higher thigh girth. It is extremely patient friendly and its wider use is recommended.
Correspondence should be addressed to Diane Przepiorski at ISTA, PO Box 6564, Auburn, CA 95604, USA. Phone: +1 916-454-9884; Fax: +1 916-454-9882; E-mail: ista@pacbell.net
