Carpal Hyperextension in Cats
Dr. Nicholas Trout
Carpal hyperextension injuries in cats produce a breakdown of the ligaments that support the back of the carpal joint in the wrist resulting in collapse from the normal upright position. The injury can produce a non-weight bearing lameness that progresses to a point that demonstrates the broken-down appearance of the carpus. The lameness usually persists and leads to significant arthritic changes in the affected joints. Sudden onset of front leg lameness
There is no breed, age or sex predisposition. Most commonly, the disease is the result of landing on the front legs from a significant height such as a second story window.
What to Watch For
Swelling in the wrist
Change in gait and stance, such that the cat appears to be walking "flatter" on the wrist
Following a thorough discussion of your cat's medical history and a full physical examination, your veterinarian will perform an orthopedic evaluation.
In the early stage, the carpus is swollen and painful and may be accompanied by instability. If your cat can use the leg, the collapse of the wrist joint may be apparent.
Standard X-rays of the carpus may not show the area of the abnormality.
Full assessment of the level of the problem in the carpal joint requires stress radiographs. Under sedation or anesthesia, the carpus is overextended to highlight the level of the joint at which the instability has occurred.
The are no specific laboratory abnormalities with this disorder, but blood work and urinalysis may be obtained as part of a work up prior to a general anesthesia. In cases of known or suspected trauma, chest X-rays may also be obtained.
Medical management is often unrewarding, so carpal hyperextension injuries are best treated surgically. This involves making an incision over the damaged joint, removing the articular cartilage from the affected joint and other joints nearby to allow the bone across the joint to fuse. The bones can be held in place to allow this fusion to occur (arthrodesis) by a metal plate and screws, pins, or even placed in a cast alone.
Your cat will receive injectable pain-killers (analgesics) during the period of hospitalization, and will probably be sent home with oral medications to reduce pain and inflammation.
Home Care and Prevention
Your cat will usually be in a splint or cast, regardless of the surgical fixation technique. You will need to keep the bandage clean and dry. The toes at the bottom of the dressing should be checked daily for swelling, pain or discomfort.
If the bandage gets wet, creates sore spots at the top or bottom, begins to smell, or seems to bother your cat, it will need to be changed.
Strict rest is important for the first six to eight weeks following surgery. Follow-up X-rays of the surgery will be arranged with your veterinarian to assess the healing, to time removal of the cast or splint, and to set up a program for gradual increase in exercise.
Depending on the type of surgery performed, your cat will not have complete range of motion in the carpus or even no motion whatsoever.
Carpal hyperextension injuries are usually the result of a significant fall from a height. To prevent this, make sure that windows are secure in second floor rooms that your cat can access.