The authors characterized the dynamic changes occurring in donor adipose-derived stromal cells and fat and recipient tissue by tracing these cellular components following cell-assisted lipotransfer. The authors' findings highlight the therapeutic value of cell-assisted lipotransfer in tissue transplantation.
Purpose: Various factors such as blood velocity, turbulent flow,and intimal injury are the most basic elements in free tissue transfers. However, how blood flow is reestablished, maintained, and changed after vascular anastomosis has rarely been studied.Methods: A 54-year-old male sustained an unreplantable severe crushing injury to his right hand. The middle finger was transferred to the thumb as an ectopic replantation using an anastomosis between the radial and digital arteries. However, secondary reconstruction for the first web space defect was inevitable and an anteromedial thigh free flap procedure was performed 2 months later using the previously anastomosed vessels. During the procedures, we noted morphologic changes in the microvessels and tried to explain those phenomena by applying the principles of hemodynamics.Results: Due to the discrepancy in vascular size between the radial and digital arteries, the velocity of the blood flow in the post-anastomotic site, which was the digital artery, must have been increased by Poiseuille’s law. Supposing that the velocity through the post-anastomotic site of the digital artery was increased, the pressure exerted by that flow decreased, resulting in more shrinkage of the vessel lumen of the digital artery by Bernoulli’s principle. Pascal’s law could also be applied in confined spaces with a static flow; where there is a constant pressure, as the radius of the post-anastomotic digital artery diminishes, the tension within the digital artery’s wall also simultaneously decreases. By Laplace’s law, the post-anastomotic digital artery’s wall thickens as less tension is exerted on the wall.Conclusion: Understanding these simple flow mechanics will enable microsurgeons to better avoid the risk factors causing thrombosis, which is related to flap failure.
The composite graft is the only surgical method that is able to maintain digital length and provide soft tissue coverage without donor site morbidities in microsurgically non-replantable fingertip amputations. This study aimed to explore the risk factors that determine the survival of composite grafts. Clinical characteristics associated with graft survival were retrospectively analysed by a comparison between the graft survival and failure groups. Of 94 patients who underwent a composite graft for fingertip amputation, the graft survived in 84 (89%). Surviving grafts showed reperfusion within 1 week. Multivariate analysis revealed that graft failure was independently associated with a crushing injury. Based on the risk factors from the comparison analyses and a review of previously published studies, a cutting injury, grafting the injured finger within 5 hours of injury, and being a non-smoker are associated with good results. In these circumstances, excellent outcomes with a high success rate can be achieved by composite graft in most adult patients as an alternative treatment to microsurgical replantation. Level of evidence: IV.
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