The fingernail is a specialized skin appendage that is essential to the appearance and function of the fingertip. Nail bed tissue is involved in shaping and attaching the advancing nail. Nail bed defects are repaired using the same tissue because the replacement of the nail bed by another tissue (eg, skin or dermis) rarely facilitates adherence of the nail.
Regardless of the donor tissue, the recipient site should be well-vascularized to support survival of the grafted tissue. Bone denuded of the periosteum is unsuitable for grafting because of its avascularity. Several authors[2,3] have reported that preparation of the injured area is necessary for graft survival in such circumstances; Matsuba and Spear decorticated the distal phalanx to induce granulation tissue growth and Yang et al used a vascularized fascial flap on the bare bone before grafting. Such preconditioning procedures are helpful to enhance graft survival on an avascular bed but are not without associated postoperative morbidities.
Postoperative cooling can be an alternative to preconditioning for salvaging a nail bed grafted to bare bone. As the distal phalanx devoid of periosteum is poorly vascularized, a nail bed grafted to bare bone heals by revascularization from the wound margin via a bridging phenomenon, whereby grafts on avascular beds are revascularized. In order to survive, a graft on an avascular bed must overcome poor vascular conditions until revascularization occurs from the margin. Cooling can facilitate graft survival by reducing the metabolic demands of the graft, thereby slowing its cellular degeneration and preventing irreversible damage. Therefore, the present authors suggest that postoperative cooling played a critical role in enhancing the survival of the nail bed grafted to bare bone in this case.
However, to the authors' knowledge, no guidelines regarding the optimum temperature and duration of cooling are available. Two mechanisms of graft revascularization on the vascular bed have been described: inosculation and neovascularization. Inosculation occurs 2 to 5 days after grafting, followed by capillary budding, which normally develops after 5 days. Considering that an avascular bed requires more time for neovascularisation than a vascular bed, the present authors suggest that postoperative cooling should be performed for more than 5 days to enhance graft survival on an avascular bed. As such, it is recommended that continuous ice cooling be performed for 7 days.
Cooling might cause some degree of vasoconstriction at the recipient site, but without a critical effect on graft survival. However, care should be taken not to make the tissue too cold or keep it cool for too long to prevent undesirable effects such as frostbite and poor revascularization. In the present case, no drugs were prescribed to prevent vasoconstriction caused by cooling; however, lipo-prostaglandin E1, which is used as a vasodilator in the treatment of peripheral vascular diseases, may be considered for such purposes. Further research is required to determine the proper temperature and duration of postoperative cooling to enhance graft survival on an avascular bed and to develop a monitoring tool to maintain the optimal temperature.
Wounds. 2021;33(4):E28-E30. © 2021 HMP Communications, LLC