Clinical Monograph Nanofracture: Bone Marrow Stimulation in Cartilage Repair Comparing Microfracture, Nanofracture, and K-Wire Perforations Subchondral Response to Marrow Stimulation W.R. Walsh, Ph.D. N. Bertollo, Ph.D. D. Schaffner, M.D. R. Oliver, Ph.D. C. Christou, B.ScVet Surgical & Orthopaedic Research Laboratories (SORL) Prince of Wales Clinical School The University of New South Wales Sydney, Australia 2031
Figure 1A,B,C: Color coded Microfracture awl (diameter: ~2.5mm) (left), Nanofracture (diameter: 1mm) (center), K-Wire (diameter: 1mm) (right)
Introduction: • Attracting precursor cells into the defect of cartilage lesions through bone marrow stimulation has been a successful treatment option in cartilage repair. Since the late 1980s, microfracture has developed into the primary procedure of choice due to its low cost nature, relative low morbidity, and encouraging results as a primary cartilage procedure, especially in young and active patients (1-3). • Renewed interest into subchondral bone shed light into microfracture’s limitations: Shallow channels, wall compression, and an increase in trabecular thickness and density have been demonstrated on microCT and histology (4-6). Chen et al. reported that deeper subchondral bone stimulation yielded better cartilage fill, higher collagen Type II content and less Type I when compared to shallow bone marrow access (5).
Figure 2A,B: Low in-vivo response with moderate bone marrow flow after microfracture
• Combined with non-standardized depth, diameter, and perforation density, microfracture’s limitations gave rise to the development of a new subchondral bone needling procedure (nanofracture) that reaches to a standardized depth of 9mm deep at a width of 1mm. • A recent investigation in an ethics approved adult ovine model shed light into the subchondral behavior of three marrow stimulation methods and their effects on the trabecular channel structure.
3A Figure 3A,B: High in-vivo response with significant bone marrow flow after nanofracture
Clinical Monograph Figure 4 A,B,C: open trabecular channels; closed trabecular channels, microCT comparison: Axial (top), Sagittal (bottom).
4A Microfracture (4A): Bone compression extending into cancellous bone; limited trabecular channel access, channel borders with high regularity. Microfracture Channel Margin (right): Dense, compressed bone deposit
4B Nanofracture (4B): Trabecular wall thickness and density appears normal; large number of open trabecular channels; channel borders with low regularity. Nanofracture Channel Margin (right): Irregular, course, fragmented
4C 1mm K-Wire (4C): Fine cancellous bone deposit surrounding the channel with limited bone marrow access; channel borders with high regularity. 1mm K-Wire Channel Margin (right): Fine, dense osseous deposit
• Microfracture elicited shallow depth with bone compression extending into cancellous bone. Trabecular channel access is limited; the channel depth and diameter are highly variable and highly user and instrument dependent. Lesion access is facilitated through various awl tip angle configurations.
Kreuz PC, Steinwachs MR, Erggelet C, Krause SJ, Konrad G, Uhl M, Sudkamp N (2006) Results after microfracture of full-thickness chondral defects in different compartments in the knee. Osteoarth Cart 14:1119-1125. doi:10.1016/j.joca.2006.05.003
Mithoefer K, Williams RJ, Warren RF, Potter HG, Spock CR, Jones EC, Wickiewicz TL, Marx RG (2005) The microfracture technique for the treatment of articular cartilage lesions in the knee. A ;prospective cohort study. J Bone Joint Surg ;87A:1911-1920. doi:10.2106/JBJS.D.02846
• Nanofracture demonstrated deep cancellous bone perforation with a high number of open trabecular channels. The procedure is standardized with stop controlled 9mm deep marrow access at a diameter of 1mm. Defect access is improved by 15 degree tip angle. • K-Wire drilling 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. Lesion access is limited by perpendicular joint access.
Conclusion Nanofracture resulted in thin, fragmented cancellous bone channels without rotational heat generation. Compared to microfracture and K-Wire stimulation, nanofracture showed superior bone marrow access with multiple trabecular access channels extending 9mm into subchondral bone.
3. Steadman JR, Briggs KK, Rodrigo JJ, Kocher MS, Gill TJ, Rodkey WG (2003) Outcomes of microfracture for traumatic chondral defects of the knee: Average 11-year follow-p. Arthroscopy 19(5):477-484. doi:10.1053/jars.2003.50112 4.
Chen H, Sun J, Hoemann CD, Lascau-Coman V, Ouyang W, McKee MD, Shive MS, Buschmann MD. Drilling and microfracture lead to different bone structure and necrosis during bone-marrow stimulation for cartilage repair. J Orthop Res. 2009 Nov;27(11):1432-8. doi: 10.1002/ jor.20905. PubMed PMID: 19402150.
Chen H, Hoemann CD, Sun J, Chevrier A, McKee MD, Shive MS, Hurtig M, Buschmann MD. Depth of subchondral perforation influences the outcome of bone marrow stimulation cartilage repair. J Orthop Res. 2011 Aug;29(8):1178-84. doi:10.1002/jor.21386. Epub 2011 Feb 24. PubMed PMID: 21671261.
6. Fortier LA, Cole BJ, McIlwraith CW. Science and animal models of marrow stimulation for cartilage repair. J Knee Surg. 2012 Mar;25(1):3-8. PubMed PMID: 22624241.
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