A couple of recent scientific papers have shown the challenges of veterinarians in making calls on x-rays at yearling sales as it relates to future soundness.
Up first was a very interesting paper on the relationship between sesamoiditis and suspensory branch injury. You can read the paper here, but the summary is that evidence of significant sesamoiditis implies a 5 times greater risk of developing clinical Suspensory Ligament Branch Injury with the onset of training. Basically, while the suspensory might be normal at the time of sale as a yearling, if they have significant sesamoiditis the chances of suspensory injury when they start training is real.
Somewhat juxtaposed to this study was a paper out of Australia titled "An assessment of intra- and inter-observer agreement of reporting orthopaedic findings on pre-sale radiographs of Thoroughbred yearlings". The study had four veterinary radiology specialists each examined twice 167 sets of radiographs for orthopaedic findings in the fore feet, fore and hind fetlocks, carpi, tarsi and stifles. The conclusion of the study was pretty amazing, but probably unsurprising for those that work with vets at sales.....
Observation of orthopaedic findings on yearling repository radiographs showed generally excellent agreement on absence of findings, but variable agreement on the presence of findings. Agreement was good for larger and easy to categorise radiographic findings. More accurate definitions and training need to be developed to improve agreement within and between observers for orthopaedic findings with poor or fair to good agreement.
When there was noting there, the veterinarians were in agreement, but if there was something there, they couldn't agree that there was! This was especially apparent in smaller and harder to categorize findings. This type of study is one that there needs to be more of, especially for commercial breeders who are heavily impacted by not only the quality of the x-rays that are taken of their horses (which has improved dramatically), but the clinical application of any adverse findings (which has not). Practically speaking, there are veterinarians that are significantly more experienced with x-rays and the analysis of these x-rays for subsequent soundness, but there is a no impetus for them to share this knowledge with other veterinarians. After all, when it comes down to it they are competing for clients and knowledge is power. This however is often to the detriment of commercial breeders where the experience of one veterinarian with a larger client can stymie a yearling making what it truly should.