Preoperative volume estimation in transverse upper gracilis flap surgery: A pilot study.

[BACKGROUND] The transverse upper gracilis (TUG) flap provides a good alternative to the gold standard DIEP in breast reconstruction. However, flap volume estimates are subjective, making preoperative planning potentially challenging.

[STUDY AIM] To derive a reliable, accurate, and reproducible mathematical algorithm for the preoperative calculation of TUG flap volumes.

[MATERIALS AND METHODS] Nineteen consecutive patients with 30 TUG flaps were prospectively included. On the assumption that the TUG flap resembles two isosceles prisms, the formula of the volume of a prism was used to calculate their preoperative flap weights. These were then intraoperatively compared to the actual flap weights. A regression equation was calculated from the correlation analysis of 10 random flaps. This was then applied to the remaining 20 flaps to assess for improved reliability and weight prediction accuracy.

[RESULTS] The prism volume equation used to clinically calculate flap volumes was: Geometric flap weight = (hbT)/2+ (hbT)/2, (h = height, b = base, T = flap thickness); all in centimetres. Geometric and actual flap weights were found to be significantly correlated (r = 0.977) generating the following regression formula: predicted TUG weight = 0.924 × geometric weight + 26.601. When this was applied to the remaining 20 flaps, no significant difference was found (p = 0.625) between predicted and actual flap weights, demonstrating an increased accuracy of predicting flap volume.

[CONCLUSION] The proposed formula provides the clinician with a more accurate and reliable estimation of available TUG flap volume and may potentially aid with preoperative planning and patient consultations.