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Basics ⬇

Outline

BASICS

Definition!!navigator!!

ALD is an abnormal deviation from the normal axis of the limb in the frontal plane, usually accompanied by an additional degree of axial rotation. Valgus is the lateral deviation, while varus is the medial deviation of the limb to the location of the deformity. The deformity is named by the joint around which the deviation is centered.

Pathophysiology!!navigator!!

Perinatal Factors

  • Flaccidity of periarticular soft tissue structures and perinatal soft tissue trauma can lead to unstable joints, resulting in abnormal loading of the articular surfaces inducing ALD
  • Anything to jeopardize the intrauterine environment of the foal (i.e. placentitis, twin foal) and premature birth (<315 days) may result in incomplete ossification (carpus and tarsus) at birth

Developmental Factors

  • Unbalanced nutrition (i.e. “crib feeding” leading to excessive grain intake, unbalanced trace minerals) can result in disproportionate growth at the level of the physis, causing ALD
  • Frequently observed in rapidly growing foals
  • Can occur days to months after birth
  • Excessive exercise and trauma can result in microfractures and crushing of the growth plate leading to early closure in severe cases (i.e. Salter–Harris type V fracture)

Systems Affected!!navigator!!

Musculoskeletal—one or more joints may be involved in the front limbs and/or hindlimbs, including the fetlock, carpus, and tarsus.

Genetics!!navigator!!

N/A

Incidence/Prevalence!!navigator!!

  • Most foals are born with some form of angular limb deformity; however, most cases resolve within 4 weeks without intervention
  • Prevalence of thoroughbred foals with ALD requiring intervention may be as high as 4.7%

Geographic Distribution!!navigator!!

N/A

Signalment!!navigator!!

Most commonly encountered in neonatal foals.

Breed Predilections

Observed in all breeds, most commonly Thoroughbreds, Quarter Horses, and miniature horses.

Age and Range

May either be present at birth or develop days to months following birth.

Predominant Sex

N/A

Signs!!navigator!!

General Comments

  • Spontaneous correction of mild ALD may occur
  • Foals with ALD must be monitored closely, as there is a limited surgical window prior to various physis closures
  • Some degree of carpal valgus (up to 4°) is normal in foals. This will correct as the foal grows and the chest broadens

Historical Findings

  • Prematurity/dysmaturity
  • Placentitis or twinning in the mare
  • Witnessed or suspected trauma at the physis
  • Crib-feeding practices on the farm

Physical Examination Findings

  • A valgus deformity results in what is termed “splay foot,” which should not be confused with outward rotation of the entire limb (“toed out”)
  • A varus deformity results in what is termed “pigeon toed”

Causes!!navigator!!

Perinatal Factors

  • Prematurity/dysmaturity
  • Ligamentous laxity
  • Perinatal soft tissue trauma
  • Intrauterine malpositioning

Developmental Factors

  • Nutritional imbalances
  • External trauma to the physis
  • Overload of a limb

Risk Factors!!navigator!!

N/A

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Laxity of periarticular soft tissues
  • Incomplete ossification/collapse of the cuboidal bones
  • Diaphyseal curvature (MCIII/MTIII)

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Laboratory Tests!!navigator!!

N/A

Imaging!!navigator!!

Radiography allows for determination of the location and the degree of the deformity, as well as concurrent physitis or physeal crushing or cuboidal bone crushing. Radiographs should be centered over the joint of interest, including the mid-diaphysis of the bones proximal and distal to the deformity.

Other Diagnostic Procedures!!navigator!!

  • Examination of the limb in both a standing and a flexed position
  • Observation of the foal at a walk
  • Manipulation/palpation of the limb can help determine whether the deformity is related to soft tissue laxity or bony abnormality

Pathologic Findings!!navigator!!

  • Asymmetric early closure of either the medial or lateral physis due to injuries or inflammation
  • Delayed ossification

Treatment ⬆ ⬇

Outline

TREATMENT

Aims!!navigator!!

A straighter limb will allow for more even load-bearing and should reduce the incidence of athletic injury.

Appropriate Health Care!!navigator!!

N/A

Nursing Care!!navigator!!

Splints and Casts

  • The purpose is to maintain the limb in proper alignment and to facilitate adequate weight-bearing for foals with incomplete ossification of the cuboidal bones and laxity of periarticular soft tissue structures
  • Problems with casts and splints in foals include osteopenia and tendon/ligament laxity. Ending the cast/splint at the level of the fetlock can help prevent these problems
  • Commercial splints/braces are available and may be easier for the owner to change safely
  • Splints are contraindicated if the ALD is due to radial/tibial deformity rather than incomplete ossification or laxity of periarticular structures
  • Splints should be changed every 3–4 days
  • Casts should be changed every 10–14 days

Corrective Shoeing

  • Application of glue-on/composite materials with an extension on the medial aspect (valgus deformities) or the lateral aspect (varus deformities) may assist in correction of the deformity
  • Hoof trimming may also be performed—the outside of the hoof should be lowered for valgus deformity; the inside for varus deformity. It is important to not overtrim or create an abnormal hoof shape that will further alter normal weight-bearing. Corrective shoeing/trimming should only be attempted if the physis is still open; cosmetic farrierwork on a mature animal with an angular limb deformity will result in joint pathology

Activity!!navigator!!

Stall Rest

  • Effective treatment for newborn foals, specifically for incomplete ossification and straight limbs
  • Foals with ALD due to disproportionate growth at the level of the physis (>10°) and diaphyseal deformities should be stall rested for 4–6 weeks
  • Foals with laxity of the periarticular supporting structures require supervised exercise in addition to stall rest
  • It is important not to prolong stall rest beyond 4–6 weeks

Diet!!navigator!!

Balanced nutrition is very important.

Client Education!!navigator!!

The examination of a foal for ALD should begin shortly after birth, followed by examination once a week for 4 weeks, and once monthly for 6 months.

Surgical Considerations!!navigator!!

Growth Acceleration (Periosteal Transection and Elevation)

  • Periosteal transection is performed on the concave aspect of the limb (e.g. lateral aspect of the distal radial physis for a carpal valgus deformity) in order to accelerate growth
  • The timing of surgery depends on the site of abnormal growth
  • The maximum effect is observed within 2 months
  • Overcorrection of the deformity has not been observed
  • A bandage should be maintained for 10–14 days following surgery
  • Stall rest for 2–3 weeks after surgery

Growth Retardation (Transphyseal Bridging)

  • Performed in foals <3 months with severe ALD or foals with significant ALD following the rapid growth phase (MCIII/MTIII and proximal phalanx = 2 months, tibia = 4 months, and radius = 6 months)
  • The goal is to retard growth by bridging the convex side of the limb, allowing the shorter side of the affected limb to keep growing
  • Current techniques include 1 transphyseal screw across the physis or 2 screws with a figure-of-eight cerclage wire connecting the two. The one-screw transphyseal technique may result in more acceptable cosmesis, but carries an increased risk of physitis. Surgical staple techniques and small bone plates have also been described. Periosteal transection and elevation are often performed in combination with growth retardation techniques
  • A bandage should be maintained for 10–14 days
  • The foal should be stall rested for 2–3 days following surgery
  • Implants need to be removed as soon as the deformity has been corrected, as overcorrection can occur

Corrective Osteotomy

  • Osteotomies have been performed for correction of significant ALD in foals with closed growth plates
  • Current techniques—closing wedge or step osteotomy
  • Maintain a bandage and splint or cast for several weeks following surgery

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • For foals that require splinting or casting, conservative doses of NSAIDs may be beneficial
  • For surgical cases, NSAIDs and antibiotics may be given as needed perioperatively

Contraindications!!navigator!!

N/A

Precautions!!navigator!!

NSAIDs can have an ulcerogenic effect on foals. Ulcer prophylaxis may include omeprazole or ranitidine during NSAID administration.

Possible Interactions!!navigator!!

N/A

Alternative Drugs!!navigator!!

N/A

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Foals with splints and casts should be assisted to nurse if unable to do so on their own
  • Careful monitoring insures implant removal the instant correction has occurred in transphyseal bridging
  • Foals with incomplete ossification should be evaluated at 2 week intervals to assess ossification progress

Prevention/Avoidance!!navigator!!

Balanced nutrition is very important.

Possible Complications!!navigator!!

  • Nonsurgical management—pressure sores, osteopenia, and tendon/ligament laxity from cast/splint application
  • Surgical management—hematoma/seroma formation at surgery site, incisional infection, wound dehiscence, overcorrection
  • Failure of transfer of passive immunity may result if foals are unable to nurse due to ALD following birth

Expected Course and Prognosis!!navigator!!

  • Studies have indicated an improvement in approximately 80% of foals that have undergone a periosteal transection
  • No significant difference in sales price or racing performance was seen between foals that were treated with a transphyseal screw for ALD and maternal siblings without ALD
  • Foals with lameness or more than 30% collapse of the third and central tarsal bones associated with incomplete ossification have a poorer prognosis

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

N/A

Age-Related Factors!!navigator!!

Timing of intervention is important.

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Synonyms!!navigator!!

N/A

Abbreviations!!navigator!!

  • ALD = angular limb deformity
  • MCIII = third metacarpal bone
  • MTIII = third metatarsal bone
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Auer JA. Angular limb deformities. In: Auer JA, Stick JA eds. Equine Surgery. St. Louis, MO: WB Saunders, 2012:1201–1221.

Baker WT, Slone DE, Lynch TM, et al. Racing and sales performance after unilateral or bilateral single transphyseal screw insertion for varus angular limb deformities of the carpus in 53 thoroughbreds. Vet Surg 2011;40(1):124–128.

Carlson ER, Bramlage LR, Stewart AA, et al. Complications after two transphyseal bridging techniques for treatment of angular limb deformities of the distal radius in 568 thoroughbred yearlings. Equine Vet J 2012;44(4):416–419.

Author(s) ⬆

Authors: Alison K. Gardner and Shannon J. Murray

Consulting Editor: Margaret C. Mudge