Overview of Feline Leg Deformities
An angular limb deformity is an abnormally shaped or crooked limb that results from abnormal growth of the bones. Angular limb deformities are most commonly seen in the forearm (radius/ulna), but can also be seen in the lower part of the hind leg (tibia/fibula).
Injury to young, growing bones can result in an angular limb deformity. These injuries can include being hit by a car, stepped on, dropped or getting a limb caught in the doorway. Abnormally shaped bones then put abnormal forces on the joints, which can lead to pain and arthritis.
Diagnosis of Angular Limb Deformities in Cats
Your veterinarian will ask you many questions to develop a complete history of the progression of the problem. These questions will include:
Your veterinarian will also examine your pet completely, including checking for a fever, listening to his heart and lungs, palpating your pet’s legs, checking for pain, checking the mobility of the joints and checking symmetry between the legs.
X-rays are usually taken of the affected leg and the opposite leg to compare the affected side with the normal side. If it is a recent injury, there might not be obvious X-ray findings early on. These initial X-rays should be used as a baseline to compare to future X-rays.
Treatment of Angular Limb Deformities in Cats
Early diagnosis and treatment is essential for the best chance for a successful outcome.
Surgery is often necessary to straighten bones affected by an angular limb deformity. The type of surgery performed depends on the individual injury, the bone(s) affected and the patient’s age and growth potential. Often, the abnormality in the limb is severe enough to warrant more than one surgery to repair it.
After corrective surgery, the pet should have rest and restriction from activity for about 4 to 8 weeks to allow the bones to heal. Frequent re-check examinations by your surgeon are necessary to identify potential problems and correct them as soon as possible.
Re-check X-rays are necessary to monitor the progress and assess the success of the corrective surgery. They are also important to see if the bone, which is often cut during the corrective surgery, has healed enough to allow unrestricted activity.
If your pet licks or chews at his incision, an Elizabethan collar may be necessary to keep him from opening or infecting the incision. If a bandage, splint or cast has been placed on the limb, it is important to keep the pet from chewing at it, and to keep the bandage clean and dry. A wet bandage or one that has been chewed up must be replaced as soon as possible. A chewed bandage loses most of its supportive qualities.
Follow your veterinarian’s instructions closely to get the best results. If you own a young, growing pet and he becomes injured, have your veterinarian examine him. Compare the length and straightness of the unaffected and affected leg, and contact your veterinarian as soon as possible if you notice a difference.
In-depth Information on Angular Limb Deformities in Cats
An angular limb deformity is an abnormally shaped, curved, or crooked limb. Angular limb deformities occur in young, growing animals after a traumatic event, such as being hit by a car, getting stepped on or dropped.
Bones grow lengthwise by elongation and multiplication of the cells at the growth plates or physes. There is a growth plate on each end of the bone.
Angular limb deformities most often occur in the forearm (radius/ulna), but can also occur in the lower hind limb (tibia/fibula). An injury to the growth plate causes crushing of the growing cells and stops their growth (premature closure of the physis). This type of crushing injury to the cells is not apparent on X-rays.
The crushed cells stop growing, while unaffected cells continue to grow. Often the damaged portion is on one side of the bone, causing one side to stop growing while the other side continues to grow. This makes the bone grow in a curved shape, similar to a plant that curves toward sunlight.
The forearm consists of a two-bone system: the radius and the ulna. If the growth plate in one of these bones is damaged, then that bone will stop growing. The other bone will continue to grow and is tethered by the damaged bone, causing a curvature or bowstring effect. Most often, the ulna is damaged after an injury to the forelimb because the shape of the physis is cone-shaped and can be injured in many different directions.
Unequal lengthening of the bones can also cause abnormal joint contact, or joint incongruity. This can result in pain, arthritis or abnormal mobility.
It can take a few weeks after an injury for an angular limb deformity to become apparent, depending on the growth rate of the pet. Some breeds are predisposed to premature closure of the growth plates, causing abnormally short, crooked legs.
The abnormality must be diagnosed as early as possible in order to have the best chance for success. Angular limb deformities require surgical correction, and the type of surgery depends on the patient’s age and the type of deformity. Often, more than one surgical procedure is necessary to correct the abnormality.
Generally, the damaged portion of the physis is removed, or the bone is cut near the damaged area to relieve the “tethering” effect it has on its paired bone.
In mature animals that are no longer growing, the curvature of the limb is either corrected at the time of surgery by cutting the bone and repositioning it straight. In patients that are young enough and have significant growth potential, the bone can be cut and allowed to straighten out as it grows.
The joint incongruity can be adjusted directly during surgery or allowed to adjust itself as the patient grows after surgery.
The cut ends of the bone can be fixed in position using either a bone plate and screws, pins or an external fixators, which is a device that has pins penetrating the bones and skin and are connected by bars on the outside of the skin. A bandage, splint or cast may also be added to provide support and/or decrease swelling.
If there is a large discrepancy in length between the affected leg and the opposite leg, then a bone lengthening procedure called distraction osteogenesis can be used. This entails application of an external fixator, which may encircle the leg with metal rings and bars. The bone ends are gradually spread apart over a period of weeks to months by having the owner turn a knob or nut on the apparatus a couple times each day. Bone fills in over the fibrous tissue that is spread apart during the distraction process and significant gains in length can be achieved.
Follow-up Care for Cats with Angular Limb Deformities
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve. Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your pet.
Follow your veterinarian’s instructions for incision and/or bandage care. Your pet may need an Elizabethan collar to prevent chewing or licking at the stitches or bandage.
Follow your veterinarian’s instructions for exercise restriction. The bones in your pet’s leg have been cut and need time (often 4 to 8 weeks) to mend before running and jumping can be allowed. Too much activity can cause the repair to fail, which can result in less than optimal results and most likely the need for more surgery.
Depending on the severity of the abnormality and the outcome of the surgery, your pet may require further surgery or treatment. A close working relationship with your veterinarian is critical to the success of the treatment. Frequent re-check examinations allow for early detection and treatment of any problems that may arise.
Abnormal forces placed on the joints can result in arthritis long-term. Arthritis may require medical management in the form of pain relievers and weight management; seek advice from your veterinarian before administering any pain relievers to your pet. Severely affected joints may require surgical fusion to eliminate the source of pain.
Angular limb deformities are complicated problems that require dedicated and observant owners.