Development of an imaging technique using clinical CT-scans to detect osteochondritic-like lesions in femoral growth plates of growing pigs

Abstract Text: Lesions of terminal cartilage canals in growth plates, diagnosed as osteochondrosis (OC) are presumed to be induced by diet, but evidence to support dietary induction is limited in controlled trials. The energy source and density of diets in this experiment were altered to simulate formulations presumed to induce OC lesions in commercial pigs. The primary objectives were to assess dietary induction of OC lesions and to develop an imaging technique which allowed a rapid assessment of OC lesions with potential for use in live animals. Thirty crossbred (1/4 Landrace X 1/4 Large White X 1/2 PIC Line 19) gilts (initial BW = 16.4+0.35 kg) were fed 1 of 3 diets designed to induce differences in the incidence of OC lesions. Diets included a corn-SBM, 1% fat control (Ctl) diet, the Ctl plus 20% glucose with 4% fat (Glc), or the Ctl plus 20% starch with 4% fat (Str). Adjustments in amino acids, Ca, and P were made for differences in energy density. After a 30-d trial, femurs were collected for assessments of OC. Joint surfaces of femurs were visually examined and entire femurs were scanned by dual energy X-ray absorptiometry (DXA) and computed-tomography (CT). Images from CT scans of excised femurs were reconstructed using Mimics (Marterialize software 17.0). Suspected lesions on the distal growth plates were analyzed digitally for volume and surface area. Two observers analyzed each femur. No differences were detected between observers in lesion traits (P > 0.15) or within individual observers (P > 0.10). The CV for within observer error for lesion volume was 10.5% and for lesion number was 1.4%. Lesions > 10 mm³ tended (P < 0.10) to have an increased volume (39.8, 21.8 and 29.7 mm³) in Ctl vs Glc and Str groups. Lesion volumes were larger (P < 0.05) on the medial vs. lateral condyle (15.2 vs 3.8 mm³). Detection of lesions in the scanned images were validated by physical sectioning of bones to reveal defects in the growth plate at locations visualized in the scanned images. In conclusion, CT scan techniques provide a non-invasive, rapid procedure to investigate OC in growing pigs. Additional benefits of image analysis may be realized by histologists as a mean to target specific lesion locations for sectioning and preparation of slides.

Keywords: dietary energy, lameness, non-invasive imaging