Standardization of the dorsal rat flap model.

In an effort to standardize use of the dorsal rat flap model originally described by McFarlane, we determined the following. The effect of delay is readily demonstrated but does not prevent necrosis entirely. Almost all flaps showed some necrosis, but delayed flaps showed approximately 15% less necrosis. Measurement of surviving flap length is simpler and as reliable as the calculations of flap area. Flap survival shows little change after fifteen days, making longer periods of observation unnecessary. The simplest landmarks for flap length are the scapular tips and the palpable hip joint. No difference in survival is demonstrated by repositioning the flap's base 1 cm caudally. A one-week delay was found to be as effective as a two- or three-week delay. These observations are offered to encourage use of the dorsal rat flap model and to lessen the cost, time, and effort needed for flap research.