Hock Shearing Injuries

* physical cleaning and removal of foreign particles, * copious joint lavage, and * possibly culture and sensitivity.

These injuries should rarely, if ever, be closed primarily; all foreign material ground into the wound - such as gravel or dirt - cannot be removed and may be better removed by subsequent exudation of fluid form the exposed tissues. Also, some authors believe that the granulation tissue that develops in these open wounds is likely to be converted into stronger, and thus more supportive, scar tissue.

Antibiotics, possibly based on culture and sensitivity, should be continued for at least 3-4 weeks.

A retrospective study published in 1995 by Beardsley and Shrader indicated 85% of cases of joint instability due to shearing injury had a good or excellent outcome when treated with a splint alone: it is surprising how well these open wounds heal by second intention by filling with granulation tissue with the skin subsequently closing to leave a relatively narrow linear scar. It is best to put the splint on the opposite side to the wound - usually the lateral or outside of the leg. Subsequent surgical stabilisation may be indicated, however.

Management may be made easier with the use of external fixateurs applied trans-articularly, and the use of hinged linear fixateurs has recently been described: Jaeger, Wosar, Marcellin-Little & Lascelles (2005)described a retrospective study of the use of hinged trans-articular external fixation frames across the hock joint in 4 cats and 5 dogs (and also 5 stifles in 4 cats and 1 dog). The frames were composed of metal or epoxy connecting rods and a hinge. Measurements of range of motion of affected and contralateral joints and radiographs were made after fixator application and removal. Treatment duration ranged from 45 to 100 days (median, 57 days). Ranges of motion in affected stifle and tarsal joints were 57% and 72% of control while the hinged frame was in place and 79% and 84% of control after frame removal. Complications were encountered in 3 cats and 2 dogs and included breakage of pins and connecting rods, hinge loosening, and failure at the hinge-epoxy interface. They concluded that providing adjunctive joint stabilization during healing, protecting the primary repair, and maintained joint motion during healing, resulted in early weight bearing of the affected limb.

Some authors have advocated early removal of a non-hinged external fixateur - when the wound is covered by granulation tissue (usually at 3-4 weeks) - and then supporting the limb in an “elastic support” bandage for another 3-4 weeks. They advocate exercise not be allowed until the 8th to 12th weeks, depending on the stability achieved.

Screws and synthetic ligaments (monofilament suture, not wire) may be placed to mimic the eroded, normal structures. Replacing the short components of the collateral ligaments is difficult, however. Diamond, Besso, & Boudrieau (1999) reported on the use of surgical implants in 23 jonts in 20 affected dogs: 44% of implants placed in 15 of the 23 joints required removal at an average of 10.7 months post-operatively because of infection, pain, or lameness caused by broken or loose implants. Wire was used in 13/15 cases and braided polyester suture used in 2 cases, but 3 out of 4 cases with infection were associated with the polyester suture…

Arthrodesis may be necessary in the long term solution. Immediate arthrodesis has also been described (Benson & Boudrieau,2002).

Bandaging and handling the affected region is often painful for the patient for the first 5-7 days, but seems to become less so as granulation tissue covers the exposed tissues.

References

Beardsley SL & Schrader SC (1995). Treatment of dogs with wound of the limbs caused by shearing forces: 98 cases (1975-1993). J Am Vet Med Assoc; 207: 1071-5.

Benson & Boudrieau (2002). Severe Carpal and Tarsal Shearing Injuries Treated With an Immediate Arthrodesis in Seven Dogs. J Am Anim Hosp Assoc.38: 370-380.

Diamond DW, Besso J, & Boudrieau RJ (1999). Evaluation of Joint Stabilization for Treatment of shearing Injuries of the Tarsus in 20 Dogs. J Am Anim Hosp Assoc 35:147-53.

Jaeger GH, Wosar MA, Marcellin-Little DJ, Lascelles BD (2005). Use of hinged transarticular external fixation for adjunctive joint stabilization in dogs and cats: 14 cases (1999-2003). J Am Vet Med Assoc. 227(4):586-91.