ALD - Angular Limb Deformities PDF

KSVM ALD Angular Limb Deformities Gal Kelmer DVM, MS, DACVS, DECVS  Angular Limb Deformity Deviation of the limb from its normal frontal axial axis Valgus deformity- lateral deviation of the limb distal to the location of the...

KSVM ALD Angular Limb Deformities Gal Kelmer DVM, MS, DACVS, DECVS  Angular Limb Deformity Deviation of the limb from its normal frontal axial axis Valgus deformity- lateral deviation of the limb distal to the location of the deformity Varus deformity- medial deviation of the limb distal to the location of the problem ALD- locations Carpus (valgus) Fetlock (varus) Tarsus (valgus) ALD- deviations Valgus= Distal limb turning outwards Varus= Distal limb turning inwards Angular Limb Deformities of the Carpus Carpal varus  Carpal valgus  Angular Limb Deformities of the Carpus With either type, Windswept there is usually some rotational deviation Toed-out  w/ valgus deformity Or Pigeon toed  w/ varus deformity Toed in Toed-out Angular Limb Deformities of the Carpus Considerations Distal radial growth slows at 12 mo & stops at 18 mo Radiographic closure of physis does not occur until 2 to 3 years of age Surgical interference w/ growth is best performed between 3 -4 mo of age BUT: Practically surgery often performed just before yearlings sale… and still succeeds Angular Limb Deformities of the Carpus Etiology Can be congenital or acquired Congenital forms according to site of primary abnormality:  Carpal joint laxity  Hypoplasia of cuboidal carpal bones  (defective ossification) Angular Limb Deformities of the Carpus Etiology Congenital forms: Carpal joint laxity  In these newborn foals, surrounding soft tissues are not strong enough to support carpus  Condition improves dramatically w/in 1st week of life, as muscle tone increases Carpal Incomplete Ossification  Angular Limb Deformities of the Carpus Etiology Congenital forms: Hypoplasia of cuboidal carpal bones  Often seen in immature or premature foals  Abnormal loading & trauma can lead to compression & wedging of cartilaginous part of these bones, resulting in angular deformity  Leads to crushing of the cuboidal bones & permanent damage Angular Limb Deformities of the Carpus Etiology Acquired form Foal is born w/ straight limbs, but angulation starts to develop w/in first weeks of life  Cause is asynchronous longitudinal growth  Contributing factors may be:  Direct trauma to the growth plate  Excessive pasture exercise  Severe contralateral lameness  Over-nutrition  Mineral imbalances Angular Limb Deformities of the Carpus Clinical Signs Clinical signs of valgus or varus deformity are obvious Angulation that varies between weight- bearing & non weight-bearing must involve a degree of joint laxity or cuboidal bone hypoplasia  Palpation of instability during manipulation of distal portion of limb indicates presence of joint laxity, or cuboidal bone hypoplasia Distal portion of limb feels stable if the cause is asymmetrical growth  Angular Limb Deformities of the Carpus Clinical Signs Radiography: Long Dorsopalmar Identification of changes to physeal area:  Flaring of metaphysis & epiphysis  Sclerosis of metaphysis  Widening of the physis  Ill-defined margins to the physis  Wedging of epiphysis  Angular Limb Deformities of the Carpus Clinical Signs Radiography: Changes in shape of carpal bones: Incomplete ossification (round, small) Wedging Fracture Subluxation  Angular Limb Deformities of the Carpus Clinical Signs Radiography: To identify center of deviation (pivot point): Draw 2 bisecting lines on radiograph. Point of intersection between these 2 lines forms point of deviation. Measure degree of angulation >5* is clinically important >10 moderate >15 severe  Angular Limb Deformities of the Carpus Clinical Signs Radiography: Pivot point At growth plate: asynchronous metaphyseal or epiphyseal growth At carpal joint: cuboidal hypoplasia or laxity  What is most accurate ?regarding carpal ALD 1. Carpal varus is typically benign and not necessitate treatment 2. Carpal valgus over 12-15* needs close monitoring after ~6m of age 3. Lateral and flexed lateral are the most informative radiographic views 4. If the cuboidal bones are not fully formed a CT is required for close monitoring 5. The pivot point indicates were is the origin of the deformity Angular Limb Deformities of the Carpus Treatment 4 general options: Rest & altered nutrition Tube cast support Surgical growth stimulation Surgical growth retardation Angular Limb Deformities of the Carpus Treatment  For minor congenital deformities, no Tx may be necessary  Often spontaneously correct w/in 1st week of life  Angular Limb Deformities of the Carpus Treatment  For mild to moderate deformity:  Stall confinement  Trimming longest side of hoof & squaring toe:  Restores balanced foot placement  Dietary changes (Calories Copper )  Angular Limb Deformities of the Carpus Treatment  For mild to moderate deformity:  Lateral (varus) or medial (valgus) shoe extensions:  Balanced foot placement; increases base of support in line w/ bony column of limb.  Nutritional management:  Reduce concentrate intake  Provide adequate Angular Limb Deformities of the Carpus Treatment  For mild to moderate deformity:  Conservative Tx must result in visible improvement of condition in 4 wks.  If improvement fails to occur surgical interference is necessary Angular Limb Deformities of the Carpus- Treatment  For manually reducible joint instability  Provide external support  To avoid asymmetrical loading of cuboidal bones  Application of tube cast on straightened limb:  Leave foot & fetlock exposed. Avoids osteoporosis & laxity Angular Limb Deformities of the Carpus Treatment  Remove/Replace cast in 10-14 d to avoid pressure sores  Maturation of hypoplastic cuboidal bones & tightening of periarticular soft tissues should occur w/in 4 to 6 wks Angular Limb Deformities of the Carpus Treatment  Surgery (for a stable limb- NOT manually straightened!!)  Tx for unresponsive &/or severe deformities  Best performed between 3-6 m of age  Post-op management:  Corrective trimming  Confinement  Angular Limb Deformities of the Carpus Treatment  HemiCircumferential Periosteal release and Elevation – HCPE,(Periosteal Stripping-PS):  Theory One: Periosteum acts as a collar around bone, restraining its growth as part of an autoregulatory system of longitudinal growth  Mechanical release of periosteal cuff restraint on 1 side of growth plate results in differential stimulation of Angular Limb Deformities of the Carpus Treatment Theory 2: Cutting the periosteum stimulates vascularization and growth There is marked controversy regarding the procedure’s efficacy:  A study in foals showed no dif. between nothing & PS  Considerable evidence of the PS effect on growth  An experimental study in lambs J Pediat. Ortho 2009:  Periosteal resection increased growth Angular Limb Deformities of the Carpus Treatment Periosteal Stripping: Technique:  Approach over concave side of physis.  Make an inverted T-shaped incision proximal to physis  Both flaps of periosteum are Angular Limb Deformities of the Carpus Treatment Periosteal Stripping: Advantages over growth retardation: Absence of implants No risk of over correction Simplicity of technique Disadvantages: Less predictable than growth retardation Controversy over the positive effects  Angular Limb Deformities of the Carpus Treatment Needle fenestration of the growth plate Fanning a needle through the growth plate Similar results to HCPE Less EBM than HCPE Advantages : Minimally invasive No general anesthesia Easy to repeat Can be done in the field Angular Limb Deformities of the Carpus Growth Retardation Temporary Transphyseal Bridging Longitudinal growth is interrupted across convex side of physis, until concave site has caught up Relies on potential for longitudinal growth Methods Staples Screws and wire Single screw Angular Limb Deformities of the Carpus  Staple technique:  Locate physis w/ needle  Insert 1 or 2 staples  Disadvantages :  Staple breakage  Trauma of introduction  Spreading of staple legs during growth  No initial compression  Staples must be removed when limb is straight Staple Placement  Angular Limb Deformities of the Carpus Treatment  Screw & wire technique:  Bone screw on either side of physis  Twist 1 or 2 wires around screw heads & tighten  Angular Limb Deformities of the Carpus Treatment  Screw & wire technique:  Advantages over staples:  Ease of removal  Ability to place screws irrespective of one another  Immediate compression across physis  Disadvantage:  Implants must be removed when limb is straight  High risk for wound complications  Blemish  Angular Limb Deformities of the Carpus Treatment Severe or combined angular deformity may benefit from combination of Tx techniques Severe angulations: transphyseal bridging & periosteal stripping combined Single Screw Technique  Single Screw Disadvantages for Carpal ALD Physitis Metaphyseal Collapse Uncommon  regarding treatment of ?carpal ALD 1. Carpal varus necessitates ~4-6 months of sleeve cast 2. Valgus is best treated by rest and lateral hoof extensions unless it is unresponsive by 12-14 months 3. Single screw is a last resort if all else failed 4. Sleeve cast is useful for deviations over 15 degrees 5. Screws and wires is helpful for valgus but useless for varus due to technical limitations Angular Limb Deformities of the Carpus Prognosis Generally favorable Unfavorable factors are: Delayed diagnosis Incomplete ossification of cuboidal bones Severe deformity Diaphyseal pivot point  Diaphyseal Deformity Wedge Ostectomy Step Osteotomy  Step Osteotomy Carpal Collapse Complications Angular Limb Deformities of the Fetlock Varus >> Valgus Often compensatory for carpal valgus Trimming & shoeing more helpful than for carpus Early intervention is essential Same treatment modalities Physeal Stimulation Single Screw TF Wing swept hock Tarsal Incomplete Ossification Tarsal Incomplete Ossification Tarsal Collapse Single Screw for Tarsal Varus Diaphyseal deformity Ostectomy & Osteosynthesis Rare lesion Step/Wedge Ostectomy- Extreme measure