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Incomplete Ossification of Tarsal and Carpal bones in Foals

Incomplete Ossification of Tarsal and Carpal bones in Foals. Christina Copple, DVM Radiology Resident NCSU CVM-VTH Accession #s: 109113. Skittles. 12 hours old at 316 days gestation Stood, suckled, passed meconium, but not seen to urinate

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Incomplete Ossification of Tarsal and Carpal bones in Foals

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  1. Incomplete Ossification of Tarsal and Carpal bones in Foals Christina Copple, DVM Radiology Resident NCSU CVM-VTH Accession #s: 109113

  2. Skittles • 12 hours old at 316 days gestation • Stood, suckled, passed meconium, but not seen to urinate • Fluctuant swelling around umbilicus and prepuce, irregular, well circumscribed mass that was increasing in size • Dribbling from prepuce, small skin defect (necrotic area) at prepuce and petechia at sight of mass • Mild laxity of both hind limbs, slight dome-shaped head • Blood work unremarkable

  3. Skittles cont’d • US of preputial area: patent urachus up to but not including the body wall, no abdominal fluid noted • Swelling gradually decreased with evidence of skin sloughing in affected area • Began urinating normally • Carpal and tarsal radiographs

  4. Left Carpus- Incomplete ossification Grade 3+ Accession #109113

  5. OssificationCarpal and Tarsal bones • Begins in last 2 months of gestation • Usually rapid in last 2 weeks of gestation and continues for ~ 1 month after birth • Ossification center is spherical, surrounded by cartilaginous precursors; ossification occurs radially until it reaches the cartilaginous extremity • Degree of ossification at birth is varied, regardless of gestational age • Carpal ossification precedes tarsal ossification http://img.dailymail.co.uk/i/pix/2007/05_02/FoalsSolent_468x572.jpg Dutton et al, JAVMA1998

  6. Skeletal Ossification Index • Adams and Poulos, Veterinary Radiology, 1988 • 52 neonatal foals and fetuses, reviewed radiographs of carpi and tarsi as well as postmortem findings • Evaluated shape and degree of ossification of cuboidal bones • Index created consists of four grades • Applied index to 24 neonatal foals of various gestational ages, radiographed within first 3 days of life • Two high risk groups of foals: <320 days gestation or “small for gestational age” • Degree of ossification is thought to be incomplete in these foals • Recommend radiographic assessment of ossification

  7. Grade 1 Some of the cuboidal bones had no radiographic evidence of ossification Grade 2 Some radiographic evidence of ossification of all cuboidal bones Did not include 1st carpal or 1st tarsal bones Proximal epiphysis of 3rd MC or MT were present and physis open Lateral styloid process of distal radius and/or malleoli of tibia were absent or barely visible

  8. Grade 3 All cuboidal bones ossified but are small with rounded edges Joint spaces appear overly wide Lateral styloid process and malleoli are distinct Proximal physes of 3rd MC and MT are radiographically closed Grade 4 - Normal Most advanced degree of ossification Met criteria of grade 3 but shape of bones were that of an adult and joint space width was normal

  9. Incomplete Ossification-Causes and Associated Risks • Congenital hypothyroidism? • Aseptic necrosis due to infarction? • Skeletal immaturity at birth-current thought • Premature = gestation <320 days • Dysmature • Twins • Can lead to deformation of bones (excess load on immature bones compresses cartilage canal vessels = ischemia, chondromalacia, dystrophic calcification and irregular-shaped centers of ossification) • May develop degenerative joint disease and angular limb deformities-poor prognosis for athletic performance Dutton et al, JAVMA1998

  10. Incomplete Ossification of Tarsal Bones • Retrospective, 22 foals between 1 day to 10 months of age • Severity of radiographic lesions were associated with outcome • Tarsal bones most often affected were central or 3rd tarsal bones Dutton et al, JAVMA1998

  11. Incomplete Ossification of Tarsal Bones • Type I: incomplete ossification with <30% collapse of affected bones • Type II: incomplete ossification with >30% collapse of and pinching or fragmentation of affected bones • Guarded prognosis for athletic soundness • Continued collapse can be decreased with early recognition and treatment • Treatment aimed at maintaining true longitudinal axis = ossification continues without further distortion of cartilaginous models • Stall rest vs splint or tube cast Dutton et al, JAVMA1998

  12. References • Dutton, David M., DVM, Jeffrey P. Watkins, DVM, MS, Michael A. Walker, DVM, and Clifford M. Honnas, DVM. Incomplete Ossification of the Tarsal Bones in Foals: 22 cases (1988-1996). JAVMA 1998 (213):11 1590-1594. • Adams, Ragan, MA, DVM and Paul Poulos, DVM, PhD. VetRadUS 1988 (29):29 217-222.

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