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

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.

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

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.

The prism volume equation used to clinically calculate flap volumes was: Geometric flap weight = (h₁bT)/2+ (h₂bT)/2, (h = height, b = base, T = flap thickness); all in centimetres. Geometric and actual flap weights were found to be significantly correlated (r² = 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.

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.