Surgical induction, histological evaluation, and MRI identification of cartilage necrosis in the distal femur in goats to model early lesions of osteochondrosis

Abstract

Objective Identify and interrupt the vascular supply to portions of the distal femoral articularepiphyseal cartilage complex (AECC) in goat kids to induce cartilage necrosis, characteristic of early lesions of osteochondrosis; then utilize MRI to identify necrotic areas of cartilage. Design Distal femora were perfused and cleared in goat kids of various ages to visualize the vascular supply to the distal femoral AECC. Vessels located on the axial aspect of the medial femoral condyle and on the abaxial side of the lateral trochlear ridge were transected in eight 4-day-old goats to induce cartilage necrosis. Goats were euthanized 1, 2, 3, 4, 5, 6, 9, and 10 weeks post operatively and operated stifles were harvested. Adiabatic T1ρ relaxation time maps of the harvested distal femora were generated using a 9.4T MR scanner, after which samples were evaluated histologically. Results Interruption of the vascular supply to the medial femoral condyle caused lesions of cartilage necrosis in 6/8 goat kids that were demonstrated histologically. Adiabatic T1ρ relaxation time mapping identified these areas of cartilage necrosis in 5/6 cases. No significant findings were detected after transection of perichondrial vessels supplying the lateral trochlear ridge. Conclusions Cartilage necrosis, characteristic of early osteochondrosis, can be induced by interrupting the vascular supply to the distal femoral AECC in goat kids. The ability of high field MRI to identify these areas of cartilage necrosis in the AECC using the adiabatic T1ρ sequence suggests that this technique may be useful in the future for the early diagnosis of osteochondrosis.

Novel Application of Magnetic Resonance Imaging Demonstrates Characteristic Differences in Vasculature at Predilection Sites of Osteochondritis Dissecans

“…First and foremost, limited availability of human cadaveric specimen forced us to draw our conclusions from a low number of observations. Previous studies in pigs 25 , horses 14 , and goats 19 , however, have indicated that the vascular supply to epiphyseal cartilage is highly predictable within a species at a given site and age. This limitation also prevented us from more closely matching the ages of pigs, goats, and humans.…”

“…Given the large secondary center of ossification that was already present in the 1-day-old goat, it is likely that this transition occurs in goats prior to birth. In fact, this unique blood supply is likely to contribute to the goats’ lack of susceptibility for developing clinically apparent OCD even after surgical interruption of the vascular supply to the epiphyseal cartilage 19 , a procedure known to trigger the development of OCD like lesions in horses 14 . The shared predilection site of OC/OCD along with a nearly identical vascular architecture in pigs and humans provides an intriguing argument for utilizing pigs as a naturally occurring animal model of human OCD.…”

An Update on the Pathogenesis of Osteochondrosis

“…It is difficult to compare the results of different studies when different sets of diagnostic criteria are used. In Table 2, we have summarized the progression of lesions following experimental vascular transection because the fact that progression was so similar suggests that it may be valid to use a single set of diagnostic criteria in several species 15,78,110,130 The experimental studies strongly indicate what the histological criteria could be, and there are also studies available that indicate how the histological criteria listed in Table 2 correlate with changes in diagnostic imaging modalities that can be used in live animals such as radiography, 79 CT, 82 and MRI. 110 …”

“…Frontal slice, plain SWI MRI scan, reprinted with permission from Toth et al 111 by ex vivo MRI of the distal femur in goats. 110 Goats were chosen because they have not been reported to develop spontaneous osteochondrosis. Femurs were first imaged using a 3-dimensional gradient recalled echo sequence to identify the site of vessel transection.…”

“…18). 110 It is therefore highly likely that it will be possible to detect osteochondrosis latens lesions by in vivo MRI and adiabatic T1r mapping, and the technique is currently being evaluated using clinically available scanners.…”