Obesity and the Latissimus Dorsi Flap: A Radiologic Study

Introduction: The increasing prevalence of obesity in patients with breast cancer has prompted a reappraisal of the role of the latissimus dorsi flap (LDF) in breast reconstruction. Although the reliability of this flap in obese patients is well-documented, it is unclear whether sufficient volume can be achieved through a purely autologous reconstruction (eg, extended harvest of the subfascial fat layer). Additionally, the traditional combined autologous and prosthetic approach (LDF + expander/implant) is subject to increased implant-related complication rates related to flap thickness in obese patients. The purpose of this study is to provide data on the thicknesses of the various components of the latissimus flap and discuss the implications for breast reconstruction in patients with increasing body mass index (BMI). Methods: Measurements of back thickness in the usual donor site area of an LDF were obtained in 518 patients undergoing prone computed tomography-guided lung biopsies. Thicknesses of the soft tissue overall and of individual layers (e.g., muscle, subfascial fat) were obtained. Patient, demographics including age, gender, and BMI were obtained. Results: A range of BMI from 15.7 to 65.7 was observed. In females, total back thickness (skin, fat, muscle) ranged from 0.6 to 9.4 cm. Every 1-point increase in BMI resulted in an increase of flap thickness by 1.11 mm (adjusted R² of 0.682, P < .001) and an increase in the thickness of the subfascial fat layer by 0.513 mm (adjusted R² of 0.553, P < .001). Mean total thicknesses for each weight category were 1.0, 1.7, 2.4, 3.0, 3.6, and 4.5 cm in underweight, normal weight, overweight, and class I, II, III obese individuals, respectively. The average contribution of the subfascial fat layer to flap thickness was 8.2 mm (32%) overall and 3.4 mm (21%), 6.7 mm (29%), 9.0 mm (30%), 11.1 mm (32%), and 15.6 mm (35%) in normal weight, overweight, class I, II, III obese individuals, respectively. Conclusion: The above findings demonstrate that the thickness of the LDF overall and of the subfascial layer closely correlated with BMI. The contribution of the subfascial layer to overall flap thickness tends to increase as a percentage of overall flap thickness with increasing BMI, which is favourable for extended LDF harvests. Because this layer cannot be separated from overall thickness on examination, these results are useful in estimating the amount of additional volume obtained from an extended latissimus harvest technique.