Above Knee Amputation Incisions Can Be Accurately Defined With Circumference and Diameter Measurements
Dhiren Patel, MD1, John Blebea, MD, MBA2.
1University of Oklahoma College of Medicine, Tulsa, OK, USA, 2Central Michigan University College of Medicine, Saginaw, MI, USA.
Objective(s): Selection of incision locations for above-knee amputations (AKA) has been more of a surgeon's clinical judgement and has not been objectively evaluated. The incised muscle flaps must be long enough to cover the cut end of the thigh but not too long that redundant skin remains and the incision is disfiguring. We performed quantitative measurements on CT images to define optimal incisional lengths.
Methods: The most common type of AKA flap is the anterior/posterior (AP) “fish mouth”. To decide where the incisions will be made, the thigh circumference is measured with a surgical suture. Half of this circumference is used to mark the base of the incisional flaps. Thereafter, the AP diameter of the thigh is measured and divided in half to determine the radius of the thigh. This radius distance is used for the length of each flap. Mathematically, the combined surface areas of these two flaps should adequately cover the cut end of the AKA.
We examined the CT cross-sectional images of 80 thighs of 40 vascular surgery patients. There were 24 males (60%) and 16 females (40%) with an average age of 64 + 10 years, weight of 86 kg and BMI of 30 kg/m2. Most of them were hypertensive (93%), smokers (75%) and had diabetes (53%). The AP and medial/lateral (ML) diameters were digitally measured 10 centimeters above the patella. Using imaging software, we quantified the surface area of the thigh at this site and compared this to the calculated clinical incisional measurements derived from the thigh circumference and diameters.
Results: The measured cross-sectional surface area of the thigh at the AKA level was 159 + 8 cm2 (mean + SEM). Utilizing flaps based on the averaged AP and ML radius produced flaps with a nearly identical calculated area of 156 + 8 cm2, (2% difference). The average of the AP and ML measurements was more accurate that either one individually; 182 + 7 cm2and 133 + 9 cm2, respectively; (P < 0.0001).
Conclusions: Incisional flaps for above knee amputations can be accurately measured based on thigh circumference and diameter and is best utilizing the average of the AP and medial-lateral diameters.
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