Jake Hacker

Background:  Microfracture (MFx) is a minimally invasive surgical procedure used to treat focal chondral defects of the articular cartilage. The technique was developed in the 1980s and consists of drilling holes perpendicularly to the articular surface, through the periosteum to create a “marrow clot” which promotes healing of the defect.^{1, 2} MFx is commonly used as treatment for grade III and IV focal chondral lesions, however it has many shortcomings. Poor outcomes for lesions larger than 2 cm², low quality repair tissue, and high rates of long term osteoarthritis and total knee arthroplasty (TKA) have been reported.^3-5 Augmented microfracture (MFx+) has become an increasingly popular area of research to address shortcomings associated with traditional microfracture. Autologous matrix-induced chondrogenesis (AMIC) is a process in which a biologic collagen matrix is fixed over the lesion after microfracture, acting as a scaffold over the area. The current review examines the effectiveness of AMIC as an alternative treatment to MFx for femoral chondral defects.

Methods:  A literature review was conducted using PubMed. Search queries included: “knee microfracture,” “autologous matrix-induced chondrogenesis,” and “focal chondral defects.” Results were selected according to relevance to microfracture, AMIC, and direct comparison of the two treatments.

Results:  Evidence suggests that for focal chondral defects in the knee between the size of 2 and 8 cm², AMIC is superior to MFx alone.⁶ Although at 1-2 year follow up, clear superiority has not been demonstrated, long term clinical outcomes of AMIC show superiority over MFx alone.⁷ MFx patients experienced significant deterioration in Modified Cincinnati and VAS pain scores by year 5 and 10, while AMIC patients remained stable with 10-year responder rates of 83–88% for AMIC versus only 22% for MFx.⁷ Radiological outcomes, including MOCART scores and MRI defect filling, were also significantly better in AMIC patients at 2-year follow-up, with displacement of the fragile marrow clot proposed as the mechanism underlying inferior MFx tissue repair.⁷

Conclusion:  AMIC is a single-stage augmented microfracture procedure that is superior to MFx alone for focal femoral chondral defects of the knee between >2 cm². While short-term outcomes after 2 years are comparable between the two techniques, AMIC demonstrates significantly better long-term clinical, functional, and radiological outcomes. As research into augmented microfracture continues to advance, including structural scaffolds and other biologics, AMIC represents a well-supported option against which emerging cartilage repair technologies can be measured.

Works Cited

[1] Steadman JR, Rodkey WG, Briggs KK. Microfracture: its history and experience of the developing surgeon. Cartilage. 2010;1(2):78-86. doi:10.1177/1947603510365533.

[2] Steadman JR, Rodkey WG, Rodrigo JJ. Microfracture: surgical technique and rehabilitation to treat chondral defects. Clin Orthop Relat Res. 2001;(391 suppl):S362-S369. doi:10.1097/00003086-200110001-00033.

[3] Gopinatth V, Jackson GR, Touhey DC, et al. Microfracture for medium size to large knee chondral defects has limited long-term efficacy: a systematic review. J Exp Orthop. 2024;11(4):e70060. doi:10.1002/jeo2.70060.

[4] Cicek H, Tuhanioglu U, Cicek F. Comparison of the bioactivity and apoptotic responses of hyaline cartilage chondrocytes and fibrocartilage chondrocytes obtained by bone marrow stimulation in rats. Acta Orthop Traumatol Turc. 2024;58(5):250-254. doi:10.5152/j.aott.2024.22172.

[5] Gobbi A, Karnatzikos G, Kumar A. Long-term results after microfracture treatment for full-thickness knee chondral lesions in athletes. Knee Surg Sports Traumatol Arthrosc. 2014;22(9):1986-1996. doi:10.1007/s00167-013-2676-8.

[6] Volz M, Schaumburger J, Gellissen J, Grifka J, Anders S. A randomized controlled trial demonstrating sustained benefit of autologous matrix-induced chondrogenesis (AMIC) over microfracture: 10-year follow-up. Eur J Orthop Surg Traumatol. 2024;34(5):2429-2437. doi:10.1007/s00590-024-03948-0.

[7] Anders S, Volz M, Frick H, Gellissen J. A randomized, controlled trial comparing autologous matrix-induced chondrogenesis (AMIC) to microfracture: analysis of 1- and 2-year follow-up data of 2 centers. Open Orthop J. 2013;7:133-143. doi:10.2174/1874325001307010133.