Management of Distal Limb Shearing Injuries in Cats

Dear Editors, — A review of shearing injuries in cats is long overdue, and the recent review by Sandra Corr, ‘Intensive, extensive, expensive … Management of distal limb shearing injuries in cats’, (JFMS 2009; 11: 747–757) is succinct and covers many of the important surgical and management issues of such injuries. I would like to draw attention to some species-specific aspects of the healing processes of superficial wounds in the cat that I feel are relevant to this discussion, along with the concept of the delay phenomenon as being a means by which long vascular flaps may be used in this species.

The work of Bohling's group,^1–3 and more recently the publication of Mitsui et al, ⁴ support the concept that the cat responds to cutaneous wounds differently than does the dog. Pseudohealing, marginal formation of granulation tissue and failure to epithelialise are just three aspects of this difference. Fascial abrasion will result in the denuded wound granulating, but the wound still heals by contracture rather than by epithelialisation. ⁴ Pseudohealing necessitates that support for approximated skin edges must be provided for longer than is usually employed in the dog. Failure of the base of denuded wounds to granulate in the feline species may result in large wounds failing to epithelialise or to heal by contraction. The failure of feline tissue, denuded of its native skin, to granulate makes skin grafting in this species unrewarding unless the technique of Mitsui et al is first employed. ⁴

There are, in addition, species-specific gross and microscopic differences in the cutaneous anatomy between the dog and the cat, ⁵ and between the vascular supply to the cutaneous tissue of the two species. ⁶ The difference in cutaneous distribution of the angiostomes and associated venostomes means that different axial based flaps need to be considered in the cat to those commonly used in the dog. ⁶

Secondary myocutaneous flaps, while having been studied in the dog, ⁷ apply to the cat provided the species differences in muscular angiostome distribution are accounted for. ⁶ These flaps have the potential of providing myocutaneous flaps to distal sites where denuding has left deep tissue exposed.

The delay phenomenon has clearly shown that choke (retiform) and true (inosculation) zones of reduced vessel calibre exist between adjacent angiostomes. ⁸ The choke type is dominant in the domestic species. ⁶ Ligation of the supply artery to one angiostome allows for these choke vessels to become functional. By staging the flap procedures, a very long flap may be created based on a single supply artery. Thus, a planned skin flap may be extended from a so-called ‘anatomical’ to a ‘dynamic’ and ultimately to a ‘potential’ flap depending on how many supply arteries are ligated. ⁹ This planned sequencing of the ligation of donor site arteries allows for a flap extension to cover any defect on the cat remote from its axial base.

Finally, I think it is worth highlighting the use of the omentum to revascularise distant wounds. Lascelles et al described the use of such a graft for axillary wounds in the cat. ¹⁰ Ross and Pardo have evaluated the use of omental pedicle extensions to distant sites in the dog, ¹¹ and I have successfully used their method for the revascularisation of hock wounds in the cat.