Hypothesis
An osteochondral implant combining a melt-electrowritten polycaprolactone chondral framework with an extrusion-printed bioceramic bone anchor — the anchor already proven osteoregenerative at a non-load-bearing site in the same species — would repair articular cartilage defects in ponies, more so when seeded with cartilage progenitor cells.
What failed
Six months after implantation in Shetland pony stifle joints, biochemical and histological analysis showed minimal glycosaminoglycan and type II collagen in the chondral compartment for both cell-seeded and cell-free implants, and micro-CT showed the bone anchor had collapsed with little mineralised new bone.
Broken assumption
A bone component proven to regenerate bone at a non-load-bearing site will hold up as the anchor of a load-bearing joint implant.
Why
The authors attribute the outcome to collapse of the osteal anchor, which removed mechanical support from the chondral compartment and precluded any evaluation of whether the BMP-9-stimulated cells helped — even though the cells had produced abundant matrix during 28 days in vitro.
From the published paper: Diloksumpan et al. Journal of Trial and Error, 2021. ↗CC BY