Quantitation of the Postoperative Vascular Response in Four Dorsal Bipedicle Flaps in the Rat

  • Thu, 9/4/08 - 11:52am
  • 0 Comments
  • 3723 reads
Author(s): 
Anna M. Parker, MD; Adam Katz, MD; Lisa Salopek, LVT; Angela Pineros-Fernandez, MD; George Rodeheaver, PhD

Poor perfusion and chronic tissue ischemia are common clinical scenarios particularly among older patients. Inciting pathologies ranging from peripheral vascular disease, venous congestion, and diabetes result in a compromised tissue bed with poor wound healing capacity, greater susceptibility to ulceration, and increased rates of infection. Efforts to better understand this ischemic condition have long employed the use of surgical flaps in the rat. In a classic paper, McFarlane et al1 described a 4-cm x 10-cm cranially based flap designed to produce varying amount of necrosis at the tip. Modified versions of this flap have been used to investigate everything from wound bed interactions to therapeutic anticoagulant therapy with outcomes assessed based on the ratio of surviving and necrotic tissue.2–8
Most clinical scenarios involving compromised blood flow do not lead directly to necrosis. Bipedicle flaps have been used to induce a less severely ischemic tissue bed without subsequent full-thickness necrosis. This lesser ischemic insult has been used to investigate the induction of the delay phenomena2 as well as incisional9–11and excisional12–14 wound healing. Quirinia et al9–11 investigated incisional wound healing in the setting of ischemia using his unique H flap model in the rat. By creating an incision, which transected a bipedicle flap at its center, they were able to test healing wounds created in an ischemic, but not necrotic environment. Similar bipedicle models have been used to test the healing of full-thickness biopsy wounds, with conflicting results. An initial paper by Schwartz et al12 reported that wounds created within a bipedicle flap showed no signs of healing over 12 days. However, in a similar study by Chen et al,13 wound healing curves demonstrated an early delay in the healing of ischemic wounds which appeared to normalize rapidly. In a third study, Gould et al14 found delayed wound healing in bipedicle flaps 2 cm in width, but not in flaps 2.5 cm wide.
The variability inherent in these results prompted the authors’ lab to attempt to quantify the perfusion dynamics along the flap and over time in 4 distinct bipedicle configurations. Each flap had 2-cm pedicles at either end with 2 flaps oriented vertically parallel to the spine, and 2 transverse across the spine. Traditional rectangular shaped flaps created from 2 straight incisions were tested as well as a modified version of each in which curvilinear incisions were used. Curved incisions resulted in elliptical shaped flaps with substantially increased area, but constant 2-cm pedicles. Flap perfusion was documented serially with a scanning Doppler as well as fluorescein dye distribution. This study attempts to better characterize the dynamic changes in perfusion kinetics based on both the location within and the geometry of 4 distinct bipedicle flaps over time. This study highlights the remarkable resilience against acute insult seen in young healthy laboratory animals as well as the continuing challenges encountered when using them to model chronic clinical conditions, such as ischemia.

Methods

References: 

1. McFarlane RM, DeYoung G, Henry RA. The design of a pedicle flap in the rat to study necrosis and its prevention. Plast Reconstr Surg. 1965;35(2):177–182.
2. Suzuki S, Isshiki N, Ogawa Y, Goto M, Hayashi O. The minimal requirement of circulation for survival of undelayed and delayed flaps in rats. Plast Reconstr Surg. 1986;78(2):221–227.
3. Hammond DC, Brooksher RD, Mann RJ, Beernink JH. The dorsal skin-flap model in the rat: factors influencing survival. Plast Reconstr Surg. 1993;91(2):316–321.
4. Dibbell DG, Hedberg JR, McCraw JB, Rankin JH, Souther SG. A quantitative examination of the use of fluorescein in predicting viability of skin flaps. Ann Plast Surg. 1979;3(2):101–105.
5. Alizadeh N, Pittet B, Tenorio X, et al. Active-site inactivated FVIIa decreases thrombosis and necrosis in a random skin flap model of acute ischemia. J Surg Res. 2004;122(2):263–273.
6. Fukui A, Tamai S, Williams HB. The importance of venous drainage in rat flaps: an experimental study. J Reconstr Microsurg. 1989;5(1):19–30.
7. Angel MF, Kaufman T, Swartz WM, Ramasastry SS, Narayanan K, Futrell JW. Studies on the nature of the flap/bed interaction in rodents—Part I: Flap survival under varying conditions. Ann Plast Surg. 1986;17(4):317–322.
8. Angel MF, Ramasastry SS, Narayanan K, Zerbe A, Swartz WM, Futrell JW. Studies on the nature of the flap/bed interaction in rodents—Part II: Morphological and fluorescein kinetic data. Ann Plast Surg. 1986;17(5):434–439.
9. Quirinia A, Jensen FT, Viidik A. Ischemia in wound healing. I: Design of a flap model—changes in blood flow. Scand J Plast Reconstr Surg Hand Surg. 1992;26(1):21–28.
10. Quirinia A, Viidik A. Ischemia in wound healing. II: Design of a flap model—biomechanical properties. Scand J Plast Reconstr Surg Hand Surg. 1992;26(2):133–139.
11. Quirinia A, Viidik A. Effect of delayed primary closure on the healing of ischemic wounds. J Trauma. 1996;41(6):1018–1022.
12. Schwarz DA, Lindblad WJ, Rees RR. Altered collagen metabolism and delayed healing in a novel model of ischemic wounds. Wound Repair Regen. 1995;3(2):204–212.
13. Chen C, Schultz GS, Bloch M, Edwards PD, Tebes S, Mast BA. Molecular and mechanistic validation of delayed healing rat wounds as a model for human chronic wounds. Wound Repair Regen. 1999;7(6):486–494.
14. Gould LJ, Leong M, Sonstein J, Wilson S. Optimization and validation of an ischemic wound model. Wound Repair Regen. 2005;13(6):576–582.
15. Taylor GI, Minabe T. The angiosomes of the mammals and other vertebrates. Plast Reconstr Surg. 1992;89(2):181–215.
16. Yang D, Morris SF. An extended dorsal island skin flap with multiple vascular territories in the rat: A new skin flap model. J Surg Res. 1999;87(2):164–170.
17. Silverman DG, LaRossa DD, Barlow CH, Bering TG, Popky LM, Smith TC. Quantification of tissue fluorescein delivery and prediction of flap viability with the fiberoptic dermofluorometer. Plast Reconstr Surg. 1980;66(4):545–553.
18. Myers B, Donovan W. An evaluation of eight methods of using fluorescein to predict the viability of skin flaps in the pig. Plast Reconstr Surg. 1985;75(2):245–250.
19. Milton SH. Pedicled skin-flaps: the fallacy of the length: width ratio. Br J Surg. 1970;57(7):502–508.
20. Dunn RM, Mancoll J. Flap models in the rat: a review and reappraisal. Plast Reconstr Surg. 1992;90(2):319–328.

image description image description