Nanofractures are inferior compared to other one-step treatments for chondral lesions in the patella: a controlled preclinical experiment in New Zealand rabbits.

Introduction: Patellofemoral chondral injuries pose a significant challenge due to their functional impact and potential progression to osteoarthritis. Bone marrow stimulation procedures, such as nanofractures and bone marrow aspirate (BMA), as well as use of autologous cartilage fragments (ACF), may enhance cartilage repair. This study aims to evaluate the efficacy of four one-step procedures plus a control group, for patellofemoral cartilage repair in an animal model.

Methods: A randomized preclinical trial was conducted in 20 New Zealand rabbits. A central chondral defect was created in the patella without affecting the subchondral bone. Knees were randomly assigned to five treatment groups: control, nanofractures, nanofractures-plus (fibrin glue), BMA and ACF. Histological assessment of defect filling and cartilage quality were performed using the International Cartilage Repair Society (ICRS) II score.

Results: All rabbits completed the follow-up period (20 weeks). The highest defect filling percentage was observed in the BMA group (61%, SD 36%), followed by nanofractures-plus (53%, SD 33%) and ACF (52%, SD 41%), followed by the control group (37%, SD 26%) and nanofractures (30%, SD 22%). Regarding tissue quality, the best mean ICRS II score was found in both nanofractures-plus (64.2%) and BMA (64.2%), followed by ACF (59.1%). Significant inferior cartilage quality was observed in nanofractures group when compared with other groups in certain items of ICRS II score.

Conclusion: All treatment strategies promoted some degree of cartilage regeneration; however, none achieved complete defect filling. Nanofractures group demonstrated the poorest outcomes in terms of subchondral bone and tissue integration; nanofractures-plus, BMA and ACF exhibited the greatest regenerative potential in terms of quality. BMA showed the highest defect filling. Given the limited regenerative capacity of these lesions and the high cost and limited accessibility of some treatments, exploring cost-effective alternatives is essential.

Level of evidence: Not applicable.