Wound tension and 'closability' with keystone flaps, V-Y flaps and primary closure: a study in fresh-frozen cadavers

Previous publications have implied that the keystone flap provides mechanical benefits compared to primary closure. This has not been objectively demonstrated.

Elliptical defects were created in 'fresh-frozen' cadaveric specimens. Two approaches were used to investigate the potential mechanical benefits of keystone flaps. Experiment 1 (wound closure): 18 defects were incrementally enlarged until they could not be closed primarily either with a single 'midpoint' suture or with a continuous suture. Attempts were then made to close these wounds with island flaps: 13 keystone flaps (seven 'type IIA' and six 'Sydney Melanoma Unit (SMU) modification') and five V-Y flaps. Experiment 2 (tension reduction): 28 defects were fashioned to be 'closable' under high tension. The 'pre-flap tension' was measured with a single midpoint suture and tensiometer. Fourteen keystone flaps (seven type IIA and seven SMU modifications) and seven V-Y flaps were then developed and mobilized with no flap constructed on the remaining seven 'primary closure' wounds. The secondary defects resulting from flap mobilization were closed leaving the primary defect unsutured. The primary defect 'post-flap tension' was then measured using the same technique.

For Experiment 1, V-Y flaps enabled closure in four of five 'unclosable' defects. Keystone flaps did not enable closure in any of the 13 cases (P < 0.001). For Experiment 2, the V-Y flap (n = 7) was the only group that produced a significant drop in wound tension across the primary defect (mean 'pre-flap' to 'post-flap' tension change: -53%, 95% CI: -67 to -39%, P < 0.001).

The data raise questions about the biomechanical benefits of keystone flaps.