Critical time for neovascularization/angiogenesis to allow free flap survival after delayed postoperative anastomotic compromise without surgical intervention: A review of the literature.

BACKGROUND: The aim of this study is to determine the minimal postoperative time required that may allow free flap survival after occlusion or ligation of the microsurgical anastomosis without surgical intervention.
METHODS: All reports describing free flap survival and failure after delayed postoperative vascular compromise (after postoperative day 3); including thrombosis and ligation, without revision of the microsurgical anastomoses were reviewed. The type of flap, recipient site, vessel of occlusion, postoperative compromise day, and nonsurgical treatment were analyzed.
RESULTS: 22 reports (32 flaps) detailed 16 arterial, 6 venous, and 10 simultaneously arterial and venous (vascular pedicle) compromise in 16 head and neck, 10 lower extremity, 4 breast, and 2 upper extremity free tissue transfers. 12 flaps survived without any intervention, 6 survived with conservative therapy (anticoagulation or leeches), and 14 survived despite pedicle ligation. The range of critical day of occlusion did not differ significantly among vessel types. 75% of arterial compromise occurred between 6 and 15 days. 75% of vascular pedicle compromise occurred between 8.5 and 18 days. When compared to jejunal flaps, skin flaps survived after earlier postoperative occlusion (10.2 vs. 20.8 days; P = 0.01).
CONCLUSION: This analysis suggests that free flaps compromised by vascular thrombosis or pedicle ligation may survive with only conservative therapy when the event occurs after a minimal critical time period. Flap survival is more probable when arterial occlusion or pedicle ligation occurs after postoperative day 12, but this minimal critical period may be as low as 6 days for arterial occlusion.