# Is Microfracture Alone Enough?
## 5 Microfracture Plus Cell-Free Injectable Scaffolds
Due to its stable crystalline composition, chitosan is usually insoluble in aqueous solutions over pH 7. The polymer has been broadly researched for industrial use, based on film and fiber formation. Given the significance of glycosaminoglycans and their analogs in inducing chondrogenesis, their use as constituents of cartilage tissue scaffolds seems to be a rational approach for improving this process. Chitosan is a partially de-acetylated derivate of chitin, extracted from the exoskeletons of arthropods. Chitosan has a linear polysaccharide structure, consisting of beta (1-4) linked D-glucosamine residues, with a varying number of randomly located N-acetyl-glucosamine groups (Figure 1). Chitosan's standard molecular weight can vary from 50 to 1000 kDa, depending on the origin and the preparation procedure. Commercially available preparations have levels of de-acetylation that range from 50 to 90% [39]. [PERSON] et al. described the procedure of applying CBS in hip chondral lesions after MFX. The CBS mixture is prepared according to the manufacturer's instructions. The mixture volume administered per subject varies according to the size of the lesion. Traction should be applied in order to access the central compartment of the femoroacetabular joint. The fluid irrigation is stopped and the articular fluid is aspired. After that, complete drying of the chondral lesion is performed with small swabs, and CBS is inserted with bent 18-gauge needles until the defect is coated. Traction is released after 15 min [40,41]. [PERSON] et al. published the most recent systematic review dealing with various treatments for enhancing MFX, including CBS, in 2020. Out of 10 studies, two included BST-CarGel(r) (Smith & Nephew, Andover, MA, USA) as an adjunct to microfracture. The imaging outcomes revealed that one-quarter of patients presented complete full-defect filling, integration of border area, and an intact repaired surface. No adhesions were reported, and significantly better defect filling and lower T2 relaxation times than MFX were obtained. They also noticed that CBS treatment was associated with knee pain in 11% of subjects. Overall, MFX + techniques improved patient-reported outcomes over MCID, but offered inconsistent imaging results [42]. Other individual results of CBS as an adjunct to microfracture are explained in Table 3.  
Research has revealed that scaffolds made from dehydrated cartilage can stimulate adult stem cells to differentiate down a chondrogenic pathway, producing cells that show morphologic, molecular, and biochemical characteristics that resemble those of articular cartilage cells. The scaffolding allows for hyaline-like cartilage to regenerate within the defect, which enables better structural support for the defect and improved longevity of the repair [43]. Figure 1: Chemical structure of chitin ([PERSON] 22 August 2007). [PERSON] et al. conducted a study where they evaluated the short-term outcomes of microfracture augmented with a micronized allograft cartilage matrix (BioCartilage) and PRP for symptomatic focal femoral condyle or trochlea cartilage defects. MRI investigations were performed 1 year after the intervention. At 2 years, the outcomes were evaluated through patient-reported outcome measures (PROMs) and the rates of return-to-work and return-to-sport. They concluded that focal condral lesions treated with the adjuvant therapy were associated with significant improvements in PROMs 2 years postoperatively [48]. A multicenter randomized controlled trial performed by [PERSON] et al. compared 46 patients divided into two equal groups, one treated with MFX alone and one with MFX plus atelocolagen augmentation. After 2 years of follow-up, the quality of the regenerated cartilage was superior after the augmentation technique. Although all clinical outcomes evaluated were superior in patients who underwent arthroscopic MFX with atelocolagen augmentation, the differences were not statistically significant [49].