Thoracic Limb Alignment in Healthy Labrador Retrievers: Evaluation of Standing Versus Recumbent Frontal Plane Radiography

Abstract

Limb alignment values are significantly different when determined from standing versus recumbent radiographs in healthy Labrador Retrievers.

The Effect of Sliding Humeral Osteotomy (SHO) on Frontal Plane Thoracic Limb Alignment: An Ex Vivo Canine Cadaveric Study

“…A 25 mm spherical calibration tool (Akucal, J2 Medical, Pittsburgh, PA) was attached to the radiographic table and positioned adjacent to the lateral epicondyle of the elbow. Two caudocranial radiographs (1 proximal and 1 distal) were obtained of each limb as previously described . First, a proximal segment radiograph was obtained with the beam centered on the distal diaphysis of the humerus, including the shoulder and elbow joints.…”

“…To obtain recumbent images, each limb was removed from the limb press and placed in mediolateral recumbency on an elevated foam support. The proximal and distal aspects of the limb were manually tensioned to maximally extend the joints of the thoracic limb, simulating the technique used for recumbent horizontal beam radiography in a previous in vivo study . After positioning the calibration tool, 2 caudocranial radiographs (proximal and distal) were obtained as described above.…”

“…The proximal and distal radiographs from standing, pre‐SHO limb positions were digitally merged as previously described using computer‐imaging software (Adobe Photoshop CS6, Adobe Systems, Inc, San Jose, CA) to create a full‐length thoracic limb digital montage . Briefly, image magnification was normalized by adjusting image size until the 2.5 cm spherical calibration tool was of identical size on proximal and distal radiographic projections.…”

“…A digital block was placed over the humeral diaphysis in each montage to blind for the presence or absence of the humeral osteotomy and SHO implants. All images were analyzed by 1 resident investigator (AHB) (eFilm version 3.3, Sound™, Carlsbad, CA) to determine 12 frontal plane limb alignment values for each radiographic montage using the CORA method as previously reported …”

“…Although the CORA method has been successfully adapted to canine orthopedics, many of these studies have been performed with limbs in recumbent positions . To mimic the standing radiographic position used in people, we previously developed a technique to obtain thoracic limb frontal plane radiographs in standing and recumbent dogs . The CORA method was used to report reference ranges for 12 thoracic limb alignment values in healthy Labrador Retrievers and document significant differences in limb alignment values in standing and recumbent limb positions …”