CT-derived indices of canine osteosarcoma-affected antebrachial strength

Computed tomography-derived structural analysis for the likelihood of pathologic fracture in canine antebrachial osteosarcoma

Determining the risk of pathologic fracture in dogs with a primary bone tumor would aid in case selection for in-situ treatment options. Prior research found strong relationships between in vitro strength of canine antebrachii with primary bone tumors and CT-derived metrics. This study assesses the prognosis for pathologic fracture in dogs with distal radial bone tumors using CT-derived structural analysis metrics. CT images of the antebrachium in dogs with aggressive osseous lesions of the radius were used to calculate structural rigidity and failure forces, including axial rigidity (AR), craniocaudal bending rigidity (BR), torsional rigidity (TR), and failure forces for a slightly-curved/asymmetric beam (Fs) or a curved beam (Fc). Metrics were compared with the clinical outcome of radial fracture. Eight of 19 dogs with CT-derived metrics developed a radial fracture. The prognostic potential of the metrics to discriminate fractured and nonfractured bones was analyzed using receiver operating characteristic curves (area under the curve), stepwise logistic regression, and classification regression (CART) analyses. Fc was the most sensitive and specific metric for prognosing fracture occurrence (AUC = 0.864). When dog body weight (BW) was included, all five metrics had AUC > 0.705. Fc was the best predictor of fracture using stepwise logistic regression and CART analysis, followed by BR. An indication of fracture probability can be determined by normalizing Fc or BR with dog BW or by using the logistic regression equation of either metric with dog BW. Results warrant further analysis of a larger cohort to evaluate fracture likelihood in dogs with antebrachial bone neoplasia.

Comparison of cross-sectional geometrical properties and bone density of the proximal radius between Saint Bernard and other giant breed dogs

OBJECTIVE

To compare the geometrical properties and bone mineral density (BMD) of the proximal radius between Saint Bernard and other giant breed dogs.

STUDY DESIGN

Observational, cross-sectional, descriptive study.

ANIMALS

Thirteen client-owned Saint Bernard dogs and 13 other client-owned giant breed dogs.

METHODS

Computed tomography (CT) studies of Saint Bernard and other giant breed dogs were reviewed. Multiplanar reconstruction of the CT images was used to determine cross-sectional variables at the proximal half of the radius, including mean cortical thickness (mCT) and moment of inertia (MOI). Cortical BMD was estimated from Hounsfield unit measurements at each cross-section and averaged per bone. One-way analysis of variance was used to detect differences between groups.

RESULTS

Proximal radii of Saint Bernard dogs had a lower cortical/medullary ratio (1.75 vs 2.2, P < .001), mCT (1.96 vs 2.64 mm, P < .001), and MOI in all planes (mediolateral [ML]: 2086.09 vs 2757.69 mm⁴ , P < .001; craniocaudal [CrCd]: 3736.36 vs 4370.28 mm⁴ , P = .025; and polar: 5852.45 vs 7127.97 mm⁴ , P = .002) compared with bones of other breeds. Cross-sectional BMD did not differ between groups of dogs, but the mean BMD of all cross-sections was lower in Saint Bernard dogs (1214.27 vs 1289.80 mg/mm³ , P = .029).

CONCLUSION

The proximal radii of Saint Bernard dogs had thinner cortices and lower CrCd, ML, and polar MOI compared with corresponding bones in giant breed dogs.

CLINICAL SIGNIFICANCE

The structural properties of the proximal radius of the Saint Bernard differ from those in other giant breeds and could reduce the ability of this region to sustain biomechanical loads. These properties could predispose Saint Bernard dogs to complications after surgical limb-sparing procedures.