Measurement of thoracic limb joint reference angles in purebred shih-tzu dogs by computed tomography

The purpose of this study was to establish normal values for the thoracic limb joint reference angles in Shih Tzu dogs and to describe the standardized CT methodology for measuring the joint reference angle of the humerus. Five pairs of thoracic limbs of Shih Tzu dogs were collected for the CT scans in this study. Three blinded observers measured the joint reference angle of the humerus and radius for each dog by using CT scans in the frontal, sagittal, and axial planes. The means (± SDs) for the average of the right and left humeral joint reference angles were as follows: mMPHA, 83.74 ± 3.95^o; mLDHA, 85.04 ± 2.57^o; mCaPHA, 46.75 ± 2.20^o; mCrDHA, 79.47 ± 1.97^o; and HTA, 19.16 ± 2.38^o. Means (± SD) for the average of right and left of the radial joint reference angles were as follows: aMPRA, 85.04 ± 1.58^o; aLDRA, 87.59 ± 1.37^o; aCrPRA, 84.60 ± 1.46^o; aCdDRA, 84.27 ± 1.79^o; and RTA, 20.91 ± 3.00^o. The intraclass correlation coefficients (ICCs) of the joint reference angles for the inter-and intraobserver reliability were good to excellent, except those for the mCrHA and HTA were moderate. Our results suggest that the method of measuring joint reference angles of other long bones by using CT can be applied to thoracic limbs and can extract valid values for one specific breed.