Nanofracture is a procedure whereby a tiny 'pick' is used to make holes through the bone plate under the joint cartilage, to encourage stem cells to enter the area and repair the defect.
Comparison of nanofracture with microfracture
The pick is smaller than the microfracture pick. A 'needling' technique may also be used, passing a needle into the bone via a cannulated nanofracture pick.
Reviewing subchondral cartilage surgery: considerations for standardised and outcome predictable cartilage remodelling. Benthien JP and Behrens P. Int Orthop. 2013 Nov; 37(11): 2139–2145.