Young foals can commonly have crooked legs (either front, hind or both), otherwise known as Angular Limb Deviation or Deformity (ALD).
- Perinatal factors: premature birth, twin pregnancy, placentitis, perinatal soft tissue trauma and flaccidity of the soft tissue structures surrounding the joints
- Developmental factors: unbalanced nutrition, excessive exercise and/or trauma
Most foals will be born with some degree of limb deviation, mostly due to ligament laxity and muscle weakness which usually will correct itself as the foal exercises. However if the cuboidal bones are not fully formed (Figures 1a and 1b), they run the risk of being crushed from exercise and the uneven load that is placed on the joint due to the laxity. Once the bones have fully formed/calcified, an ALD will result due to the abnormally shaped cuboidal bones.
There are two general terms used to describe these deviations:
- Valgus refers to an outward deviation of the limb (Figure 2)
- Varus refers to inward deviation of the limb (Figure 3)
The most common deviation seen in young foals is in one or both of the front limbs and is called: Carpus Valgus (outward deviation from the knee) (Figure 2).
Angular Limb Deviations are usually easily diagnosed by looking at the limbs standing directly in front of, directly behind and/or from the side of the foal. You can also observe the foal while walking in a straight line on a hard, level surface. From one or more of these vantage points, you should draw an imaginary plumb line from the top of the leg to the ground. If you cannot draw a straight line from top to bottom, then there is a deviation. The area that is the cause of the deviation is where the straight line breaks and turns.
Examination of foal’s conformation should start early in life. Decision making regarding treatments is time sensitive because response to treatment is greatly affected by the presence of an open growth plate and the phase of growth (rapid growth). Your primary care veterinarian and veterinary surgeon will recommend the appropriate timing for conformational evaluations.
The affected limb(s) may show:
- Variable amounts of joint swelling +/- palpable heat
- Inflammation of a growth plate (physitis) (Figure 4)
- Excessive ligament laxity
- Excessive wearing of the inside (for valgus deviation) or outside (for varus deviation) of the hoof wall
- Incomplete bone formation of the carpus (knee) or tarsus (hock) +/- bone collapse within these joints (only seen with an X-ray) (Figures 1a and 1b)
Your primary care veterinarian may recommend some of the following diagnostic tests:
- Physical examination (including manipulation of the limbs) of the foal
- Radiographs (Figure 5) to assess:
- The location of the deviation
- The angular degree of deviation from normal
- To evaluate the condition of the bones within the affected joint
- Appearance of the growth plates
- Response to treatment over time
- Conservative management
- Surgical treatment
Restrictions following treatment depends on the procedure performed and severity of deviation, but may include:
- Stall rest +/- short amounts of controlled handwalking
- Daily monitoring of the affected limb(s) for heat, swelling, lameness on a daily basis
- Regular bandage changes until skin suture removal
- Skin suture removal 10-14 days after surgery
- Repeat radiographs to verify complete correction of the deviation
- Screw or screws and wires must be surgically removed as soon as a visual correction of the deviation has occurred
Minor post-op complications can include:
- Incisional infection
- Seroma (an accumulation of fluid under the incision)
Major post-op complications can include:
- Overcorrection is possible with growth retardation (transphyseal bridging, transphyseal screw) procedures if the implants are not surgically removed at the appropriate time (or at all)
- Bone infection if incision, screws and/or wires become infected
The outcome varies greatly, depending on the limb affected (front vs. hind), underlying condition, degree of deviation, joint affected, and future use of the horse.