title: Micro-computed tomography of early lesions of osteochondrosis in the tarsus of foals.
abstract: BACKGROUND
  Osteochondrosis (OC) is an important developmental orthopedic disease of human and equine patients. The disease is defined as a focal disturbance in enchondral ossification. In horses, the disturbance can occur secondary to failure of the blood supply to growth cartilage. Diagnosis of the early, subclinical stages that can clarify the etiology is currently confined to cross-sectional histological examination. The potential for micro-computed tomography (micro-CT) with angiography to detect early lesions of OC has not yet been investigated.
  
  
  METHODS
  Nine Standardbred foals bred from parents with OC of the tarso-crural joint were sacrificed at weekly intervals from birth to 7 weeks of age. Permanent barium angiograms were created within one hind limb post mortem, and samples collected from two predilection sites for OC within the tarso-crural joint of the perfused hind limb. The resulting 18 sample blocks were scanned with a custom-built micro-CT equipment set-up, and analyzed as 2D slices and 3D volume rendered models before sectioning for conventional histological examination.
  
  
  RESULTS
  Histological examination identified eight early lesions in seven locations within six joints from the nine foals. Micro-CT with angiography was able to detect seven lesions in the same sites as histological examination. Lesions consisted of non-perfused foci within growth cartilage. No perfused vessels exited from subchondral bone deep to any lesion. Six of the seven lesions were associated with focal defects in the subchondral bone plate. Evidence of ongoing ossification was seen in three out of the seven lesions and included one separate center of ossification.
  
  
  CONCLUSIONS
  Micro-CT was a useful technique for examination of early lesions of OC. The results of micro-CT were compatible with failure of cartilage canal vessels at the point where they cross the ossification front. Resultant areas of ischemic chondronecrosis were associated with focal delay in enchondral ossification as visualized in 3D volume rendered models. Micro-CT combined with histology clarified the role of different forms of ossification in the secondary repair responses to lesions.
authors.affiliation: Norwegian School of Veterinary Science, Department of Companion Animal Clinical Sciences, Section for Equine Medicine and Surgery, Post box 8146 Dep., N-0033 Oslo, Norway. kristin.olstad@veths.no
authors.forename: Kristin
authors.initials: K
authors.lastname: Olstad
authors.forename: Veerle
authors.initials: V
authors.lastname: Cnudde
authors.forename: Bert
authors.initials: B
authors.lastname: Masschaele
authors.forename: Ragnar
authors.initials: R
authors.lastname: Thomassen
authors.forename: Nils Ivar
authors.initials: NI
authors.lastname: Dolvik
mesh_terms: D000792:Angiography / Q000379:methods; D000818:Animals; D000831:Animals, Newborn; D002356:Cartilage / Q000473:pathology; D049109:Cell Proliferation; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis; D006736:Horses; D007511:Ischemia / Q000473:pathology; D008297:Male; D009336:Necrosis; D010007:Osteochondritis / Q000175:diagnosis* / Q000662:veterinary*; D013639:Tarsal Bones / Q000000981:diagnostic imaging* / Q000473:pathology*; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*