Abstract
Introduction
Bone marrow stimulation has been a successful treatment option in cartilage repair and microfracture was the procedure of choice since the late 1980s. Despite its success in young and active patients, microfracture has inherent shortcomings such as shallow channels, wall compression, and non-standardized depth and diameter. This in vitro study assessed bone marrow access comparing microfracture, 1 and 2mm K-Wires, 1mm drill, and a recently introduced standardized subchondral bone needling procedure (Nanofracture) that creates 9mm deep and 1mm wide channels.
Methods
An adult ovine model was used to assess access to bone the marrow spaces as well as effects on bone following microfracture, nanofracture, K-wire, and drilling following ethical clearance. All bone marrow stimulation techniques were conducted on a full thickness articular cartilage defect on the medial femoral condyles by the same surgeon. The same groups were repeated in vitro in 4 paired ovine distal femurs. MicroCT (Inveon Scanner, Siemens, Germany) was performed using 3D reconstruction and 25 micron slice analysis (MIMICS, Materialise, Belgium).
Results
Microfracture elicited shallow depth with bone compression surrounding the channels. Trabecular channel access was limited; the channel depth and diameter were non-standardized and highly user and instrument dependent. Nanofracture demonstrated deep cancellous bone perforation with a high number of open trabecular channels. K-Wire drilling with both diameters resulted in well-defined channel walls, outlined by fine osseous deposits. Trabecular channel access was limited. The diameter of bone perforation is standardized, but depth is defined by visual controls. 1mm drill bit reaming demonstrated better osseous evacuation, but still limited trabecular marrow access.
Discussion and Conclusion
Nanofracture resulted in thin, fragmented cancellous bone channels without rotational heat generation. Compared to microfracture, drilling and K-Wire stimulation, nanofracture showed superior bone marrow access with multiple trabecular access channels extending 9mm into subchondral bone.
