Rico Vannini graduated 1981 from the University of Zürich. 1987 he completed his surgical residency at the Ohio State University. For nine years he was faculty surgeon and lecturer at the University of Zürich. 1994 he became Diplomate of the European College of Veterinary Surgeons. Since 1996 he is owner of Bessy's small animal clinic, one of the largest private clinics in Switzerland. He was president of AO and ESVOT. He maintains an active interest in continuing education among others being international speaker and international chairmen of the Education Commission of AOVET. His hobbies are agility, scuba diving and cooking. He is mobile cash machine for two young adults, master of 8 dogs and food provider of a cat.

Shearing injuries are usually the result of a car accident. The animal slides over the road surface while the rough pavement shaves the leg off. The distal extremities are most commonly affected with the medial side of the tarsus and carpus most commonly injured.

Depending on the severity of the injury, only skin may be grinded off or the entire side of the joint is destroyed. In the worst case, ligaments, tendons, joint capsule, bone and cartilage are abraded, resulting in an open, contaminated joint which is highly unstable. The wounds caused by a shearing injury are characterized by loss of tissue in face of heavy contamination.

Shearing injuries are surgical emergencies and treated very similar to grade 3 open fractures. The treatment includes administration of antibiotics at the time of hospital admission, thorough debridement of the wound, copious lavage, open wound therapy and immobilization of the soft tissue as well the injured joint. Goal of the primary therapy is to preserve vascularity, to prevent infection and to preserve joint function and thus ultimately maintain full limb function.

However with severe injuries this cannot always be achieved. Thus an early decision has to be made, whether the injured limb can be preserved or needs to be amputated. Amputation of the injured limb has to be considered, if the blood supply to the foot is destroyed and there are no vital footpads left.

If an open joint injury is present or suspected, exploration and careful debridement of the joint is mandatory. For full inspection of the joint an additional arthrotomy might be necessary. Alternatively, arthroscopy can be considered. Cartilaginous fragments, which cannot be rigidly stabilized, are removed. Stabilizing structures such as ligaments, tendons and joint capsule are preserved whenever possible. Closure of the joint capsule should always be attempted. A joint should only be left open if an incomplete debridement is suspected, an infection is present or suspected or if there is no joint capsule left to close. In this case the joint is covered with sterile moist gauze and managed similar to open wounds.

During the accident, road dirt may be ground into the exposed bone. For proper debridement, it might be necessary to scrape the bone with a curette. Scraping of the bone can also be used to promote granulation tissue formation over denuded bone. The blood clot being formed acts as a scaffold for fibroplasia and neovascularization. For the same purpose, multiple small holes can be drilled into the bone.

After debridement, the wound is lavaged with copious amounts of warm physiologic saline solution. The addition of an antiseptic is not really of benefit.

The skin wound should always be left open, even if there is enough skin available for closure.

Degloved skin can occasionally be converted to a full thickness skin graft if viability of the skin flap is uncertain and the wound is very fresh and the wound bed well is healthy and well vascularized. Otherwise delay any wound closure or skin grafting until granulation tissue has formed. After initial debridement and lavage, open wound management with appropriate bandaging techniques is still state of the art.

Recently wound management using negative pressure with a vacuum assisted device has gained popularity and might be advantageous in heavily infected open wounds.

Early stabilization of the joint is indicated in most cases. Ligament repair or augmentation should be attempted whenever possible. Ligament replacement is indicated if no ligament is left and loss of joint surface is less than 25%. Prognosis for the distal joints is best, if the joint surfaces of the malleoli or styloids remained intact. Braided suture can be used in face of contamination, provided the wound is left open to granulate. A large monofilament nylon suture might be preferred (fishing line). A temporary transarticular external skeletal fixator (ESF) is applied to immobilize the joint and to protect the repair.

Consider an arthrodesis if more than 25% of joint surface is lost, there is an irreparable fracture of the joint or infection is already established.

If infection is already present or likely to become a problem or if viability of the soft tissue and bone is critical, a transarticular ESF might be the best choice. This ESF can be left in place, until the joint is fused, or it can be used temporarily, followed later by an internal stabilization with a plate. The degree of stability provided by the ESF depends, whether it is used as a primary form of fixation for fusion or if it is only used for temporary stabilization until an internal form of fixation is used for arthrodesis.

If the contaminated wound can be converted to a clean one and there is enough viable soft tissue to cover the implant, the joint can occasionally be arthrodesed by an immediate internal fixation, such as a plate.

Once the joint is stabilized and immobilized (with this the soft tissues are immobilized as well) and healthy granulation tissue has covered large open wounds skin graft is used to close large skin defects. Secondary wound healing is not ideal as the skin defect will heal by contraction and epithelisation, covering the wound with very fragile scar tissue. This is not able to resist even minor injuries to which the skin of the distal extremity is commonly exposed.

References

1.  Ben-Amotz R, Lanz O. The use of vacuum-assisted closure therapy for the treatment of distal extremity wounds in 15 dogs. Vet Surg. 2007;36:684–690.

2.  Benson JA, Boudrieau RJ. Severe carpal and tarsal shearing injuries treated with an immediate arthrodesis in seven dogs. J Am Anim Hosp Assoc. 2002;38:370.

3.  Campell BG. Managing degloving and shearing Injuries. NAVC Clinician's Brief. 2011.

4.  Diamond DW, Besso J, Boudrieau RJ. Evaluation of joint stabilization for treatment of shearing injuries of the tarsus in 20 dogs. J Am Anim Hosp Assoc. 1999.