Angular limb deformities: The straight scoop! (Proceedings)

Definitions

• Lateral or medial deviation to the long axis of the bone in the frontal plane

• Valgus: lateral deviation distal to the point of angulation (pivot point)

• Varus: medial deviation distal to the point of angulation (pivot point)

• Rotational deformity usually accompanies ALD

o Outward or inward rotation

Risk factors

• Age: foals of all ages, usually young foals

• Breed: occurs in all breeds and particularly rapidly growing foals

• Sex: occurs in both sexes, slightly higher incidence in colts

• Limb: most often in front limbs, unilateral or bilateral

• Site: affects carpus, fetlock, and tarsus

• Frequency: carpal valgus is most common fetlock varus is second most common.

Multifactorial and complex pathogenesis

• Asynchronous longitudinal growth of physis

• Ligamentous joint laxity

• Defects in endochondral ossification of the cuboidal bones and/or small metacarpal/metatarsal bones

• Traumatic luxation or fracture of the physis, epiphysis, or carpal/tarsal bones

Alterations of endochondral ossification

• Rapid growth

• Genetic capacity

• High energy intake

• Stunting early in life followed by increase feeding leading to growth spurt

• Trauma to endochondral ossification centers

• Axial compression beyond physiologic limits

• Physeal fracture luxation/infection

• Genetic predisposition

• Nutritional imbalance

o Excess energy

o Protein (excess or deficiency)

o Calcium:phosphorus ratio (excess or deficiency of ratio:1.6)

• Trace minerals

o copper deficiency

o zinc excess

o manganese deficiency

Congenital angular limb deformities

• Intrauterine malpositioning

• Over-nutrition of mare

• Joint laxity

• Incomplete ossification of cuboidal bones

• Premature/dysmature

• Hypothyroidism

• Osteochondrosis

• Incomplete development of MT/MC II and IV

Acquired angular limb deformities

• Excessive exercise

• Growth plate injury or infection

• Excessive weight bearing secondary to contralateral limb lameness

• Over-nutrition

• Improper trimming or poor foot care

• Poor conformation

• Congenital ALD that become worse

Diagnosis

• Visual exam

o Standing and walking

o Is it rotational or angular limb deformity?

• Rotational

• Due to lack of developed chest musculature and size

• Whole limb is rotated outward

• Toes and carpi should point in same direction

• May be combined with ALD

o Multiple limb involvement

o Multiple sites in one limb

o Rough estimate of degree and pivot point

o Lameness in affected limb or contralateral limb

o Look at mare's legs

• Physical exam

o Palpate for joint laxity

o Observe angulation when flexed

o Evaluate hoof balance

o Palpate both limbs for

o Heat

o Pain

o Swelling

o Crepitus

• Radiographic exam

o Technique

• AP and lateral views, wt bearing if possible

• Use long plates (7"x17")

• Pivot point: determine by bisecting long bones above and below joint note area of intersection

• Degree of angulation: measure above angle

• Mild < 5°, Severe > 15°

o Pathology

• Metaphysis

• Flaring and sclerosis

• Growth plate

• Indistinct physis

• Irregular width (convex side)

• Epiphysis

• Wedge-shaped flaring

• Cuboidal bone

• Abnormal shape

• Hypoplastic

• Collapsed

• Subluxated

• MT/MC II or IV

• Shorter or wider joint space

• Bone cortex

• Diaphyseal remodeling

Treatment for angular limb deformities

• Treatment goals

o Improve conformation

o Prevent secondary changes (DJD)

o Improve athletic performance

• Treatment

• Conservative

• Stall rest and re-evaluation

• Corrective trimming and shoeing

• Tube casts, splints or braces

• Very important to use when there is delayed ossification and laxity

• PVC

• Casting material

• Splints or tube casts

• Commercial

• Dynasplint

• Surgical correction

o Periosteal transection and elevation

o Transphyseal bridging

• Two screws with cerclage wire across the physis

• Single position screw across one side of the physis

o Wedge osteotomy

• Principles of surgical correction

o Stimulate growth on the concave surface

• Periosteal transection

o Retard growth on the convex surface

• Transphyseal bridging

o Reconstruction

• Corrective osteotomy / ostectomy

Transphyseal bridging

• Monitoring of the foal is critical

• Implants can become infected

• Local inflammation/infection due to angulation

• Bilateral or multiple TPBs may need to be removed at different times

• Overcorrection is possible with this technique!!!!

Prognosis

• The more distal the pivot point, the poorer the prognosis

• The older the foal, the longer the implant needs to stay in, and the less growth/straightening potential

• 83% of carpal valgus were corrected regardless of the pivot point and degree of angulation

• Carpal and tarsal bone collapse/crush carry a more guarded prognosis

• Fetlock deformities less likely to get corrected because of short time frame for intervention

Prevention / minimization

• Discussion with owners

• Good and consistent monitoring

• Proper feeding (avoid over-nutrition)

• Pay attention to mare/stallion conformation

• Good and consistent foot trimming

• Avoid excessive exercise

• Fetlock deformities need early treatment