Developmental Orthopaedic Disorders

Angular Limb Deformities and Flexural Limb Deformities (ALD & FLD)

Inter membranous growth is outwards growth and endochondral is longitudinal growth.

Definition of ALD and FLD is a deviation of the limb away from the sagittal plane caused by abnormalities in joints. Lateral deviation being valgus and medial deviation being varus. Valgus is more common as more weight travels down the inside.

FLD is an abnormality in position or angle of foal or yearling when viewed from the side. It can be classed as flexor laxity. Seen more in front limbs and usually bilateral. Sometimes congenital, which is before birth, caused by miss-positioning in the womb or a vitamin deficiency. Alternatively, it can be acquired through pain response leading to abnormal flexing of joints. Flexor laxity means hyperextension, the muscles are strong enough to hold the bone column, and the toe will lift of the ground. Auto correct system in horses means it sometimes corrects itself. This comes in the way of a caudal extension. Cuboidal growth plates in the knee failing to ossify are a problem. If misshaping begins to occur then a tube cast needs to be placed to keep the limb straight.

ALD is caused by parental or developmental factors. ALD exists due to muscle laxity or cuboidal bone issue. Most foals are born with some sort of ALD. This is because most foals are born with soft flexible cartilage in joints rather than hard bone. So, to stabilize itself it shall stand base wide. The chest is very narrow as there is no muscle yet so straight legs would cause base narrow conformation and be very wobbly. Because of this more weight travels down the medial aspect causing carpal valgus as the medial side of the bones ossify first to harden up. Foals do have an auto correct system in place to aid this. When this happens, the limb can start to straighten rather than continue and get worse. Muscle is constantly getting stronger as well helping the problem. If correction is not occurring then a tube cast should be applied to keep leg straight. Do this after 2 weeks if horse has not corrected itself, doing so any earlier may cause more damage than good. Remember growth closure plates. After a month, these deformities will struggle to correct. Foal extensions such as a medial extension can be used to straighten carpal valgus. If this still doesn’t correct then surgical operations can be done but only if there is enough time left in growth plates to heal. Screw and wire attaches a screw to two bones and a wire in between them both tying them together. Tighten the wire and it should straighten. Removing of screws will heal as it is still a young animal. Prognosis is good and shouldn’t cause any issues unless the deformity is left way to long before being corrected. This is such a common thing and often so easily resolved that this shouldn’t be a worry.