Implantation of a polycaprolactone scaffold with subchondral bone anchoring ameliorates nodules formation and other tissue alterations.

Purpose: Articular cartilage has limited repair capacity. Two different implant devices for articular cartilage regeneration were tested in vivo in a sheep model to evaluate the effect of subchondral bone anchoring for tissue repair.

Methods: The implants were placed with press-fit technique in a cartilage defect after microfracture surgery in the femoral condyle of the knee joint of the sheep and histologic and mechanical evaluation was done 4.5 months later. The first group consisted of a biodegradable polycaprolactone (PCL) scaffold with double porosity. The second test group consisted of a PCL scaffold attached to a poly(L-lactic acid) (PLLA) pin anchored to the subchondral bone.

Results: For both groups most of the defects (75%) showed an articular surface that was completely or almost completely repaired with a neotissue. Nevertheless, the surface had a rougher appearance than controls and the repair tissue was immature. In the trials with solely scaffold implantation, severe subchondral bone alterations were seen with many large nodular formations. These alterations were ameliorated when implanting the scaffold with a subchondral bone anchoring pin.

Discussions: The results show that tissue repair is improved by implanting a PCL scaffold compared to solely microfracture surgery, and most importantly, that subchondral bone alterations, normally seen after microfracture surgery, were partially prevented when implanting the PCL scaffold with a fixation system to the subchondral bone.