Angular Limb Deformities (ALD) Quiz

Angular Limb Deformities (ALD)

• ALD is a deviation of the limb from its normal frontal axial axis.
• Valgus deformity is a lateral deviation of the limb distal to the deformity location.
• Varus deformity is a medial deviation of the limb distal to the problem location.
• Locations for ALD include carpus (valgus), fetlock (varus), and tarsus (valgus).
• Valgus describes distal limb turning outwards, varus describes distal limb turning inwards.
• Carpal valgus and varus are specific to carpus deformities.
• Toed-out rotation is often seen with valgus deformities (pigeon-toed).
• Toed-in rotation is often seen with varus deformities.
• Distal radial growth slows at 12 months of age and stops at 18 months.
• Radiographic closure of growth plates occurs between 2-3 years of age.
• Surgical intervention is best performed between 3-4 months of age, but often occurs before yearlings' sale.
• ALD can be congenital or acquired.
• Congenital ALD is categorized by the primary site of abnormality, including carpal joint laxity and hypoplasia of cuboidal carpal bones (defective ossification).
• In newborn foals with carpal laxity, surrounding soft tissues are not strong enough to support the carpus.
• Condition improves within the first week of life as muscle tone increases.
• Carpal incomplete ossification is a condition characterized by incomplete bone development, often appearing round and small on x-rays.

Clinical Signs

• Obvious clinical signs exist for valgus or varus deformities.
• Angulation varies between weight-bearing and non-weight-bearing.
• Joint laxity or cuboidal bone hypoplasia may be involved.
• Palpation reveals instability during manipulation of the distal portion of the limb.
• The distal portion feels stable if asymmetrical growth isn't the cause.
• Radiographic changes in the shape of carpal bones include incomplete ossification (round, small), wedging, fractures, and subluxation.
• Radiographic indicators for diagnosing ALD include long dorsopalmar views that identify changes in the physeal area. Signs include flaring of metaphysis and epiphysis, sclerosis of metaphysis, widening of the physis, ill-defined margins to the physis, and wedging of epiphysis.
• To identify the center of deviation (pivot point), radiographs employ two bisecting lines; their intersection indicates the deviation point.
• The angle of angulation is measured. More than 5 degrees is clinically important; 10 degrees or more is moderate; and more than 15 degrees is severe.
• Growth plate issues (asynchronous metaphyseal or epiphyseal growth), or carpal joint/cuboidal bone hypoplasia/laxity may also need to be considered.

Etiology

• Congenital forms include carpal joint laxity, hypoplasia of cuboidal carpal bones, which can result from abnormal loading or injuries that cause compression and wedging of the cartilage that forms the cartilage of the bones, resulting in the deformity. This is often seen in premature or immature foals.
• Acquired forms are caused by asynchronous longitudinal growth, potential trauma to the growth plate, excessive pasture exercise, or severe contralateral lameness. Over-nutrition or mineral imbalances can also contribute.

Treatment

• For minor congenital deformities, no treatment may be necessary, as they often spontaneously correct within the first week of life.
• For mild to moderate deformities, stall confinement, trimming the hoof, and dietary adjustments are typical practices.
• Shoe extensions are used if the deformity is lateral (varus) or medial (valgus).
• Conservative treatment needs improvement within 4 weeks. If not, surgical procedures become necessary.
• For manually reducible joint instability, external support is provided.
• Applying a tube cast on the straightened limb, keeping the foot and fetlock exposed prevents bone loss and laxity.
• The cast is replaced approximately every 10-14 days.
• Surgical intervention involves a stable limb that hasn't been manually straightened. This occurs between 3-6 months of age. Surgery may be done for unresponsive/severe deformities.
• Post-operative management includes corrective trimming and confinement.
• Procedures like hemi-circumferential periosteal release and elevation (HCPE), also known as periosteal stripping (PS), are options.
• Periosteal stripping may stimulate vascularization and growth but its efficacy is debated.
• Needle fenestration of the growth plate may deliver similar results to the periosteal procedures but is less well-established.
• Temporary transphyseal bridging may be used to interrupt longitudinal growth on the convex side of the physis to allow the concave site to catch up in growth.
• Staple or screw/wire techniques are options for the treatment of growth retardation.
• Use of staples requires placement through the growth plate and may cause trauma.
• Screw techniques are more easily removed than staples.

Complications

• Carpal collapse can be a complication of some surgical procedures.
• Physitis or metaphyseal collapse is a possible disadvantage.

Other Information

• The carpus and its associated Angular Limb Deformities (ALDs) manifest with varus being more common than valgus; trimming and shoeing are effective for treatment of this type of deformity; early intervention is vital; same treatment options are used in comparison to other ALDs.
• The text mentions "wing-swept hock" as another form of leg deformity.
• Incomplete ossification of the tarsus is also of concern for this type of deformity.
• Tarsal collapse is a concern regarding tarsal deformities.

Test your knowledge on Angular Limb Deformities (ALD), including the definitions and differences between valgus and varus deformities. Explore the various locations affected by ALD and the significance of growth plate closure. This quiz will cover both congenital and acquired forms of ALD and their treatment options.