Cartilage Reparability by the Second Microfracture
Objects: Articular cartilage has some limitations in healing ability. Microfracture (MF) is considered as the first-line treatment for full- thickness cartilage lesion. But in the long-term follow-up after MF, failure rate was increased because MF was influenced by many factors such as capacity of mesenchymal stem cells (MSCs) frequency, clinical factors, loading history and constitution of the patient. Therefore, the aim of this study is to evaluate whether the second MF could stimulate bone marrow effectively in the recurrent cartilage defect lesion after MF.
Materials and methods: Sixteen-weeks-old male New Zealand white rabbits were used for this study. In the patellar groove of unilateral knees, the full-thickness chondral defect with 5-mm-diameter and 0.2-mm-depth was created by a biopsy punch. In which, the MF holes were created by using a 3-mm-length awl which was optimized based on the bleeding volume and the defect depth observed with a micro-computed tomography (micro-CT) image. Thirty rabbits were divided into 3 groups. The first group was the negative control group with untreated full-thickness chondral defect. The second group was the control group treated with MF. The third group was the experimental group treated with MF and the second MF again at 8 weeks after the first MF. At the end of 8 weeks, the rabbit in the negative and the control group were sacrificed and the specimens were collected for confirmation healing ability of MF newly developed for this study. The regeneration of new tissues was evaluated based on the histological changes in defect and morphological changes in subchondral bone area by histological staining images and micro-CT images, respectively. The number of colony in colony-forming unit-fibroblasts (CFU-F) test after the re-MF would be compared with the first MF in order to evaluate the number of MSCs derived from bone marrow.
Results: MF awl with 3 mm length was a proper surgical tool for present study. At 8 weeks after the first MF, the new bony tissue was observed in subchondral bone plate. Moreover, the average of MSC number was about 120 cells/1 ml bone marrow from the first MF, and there were 150 cells/1 ml bone marrow isolated from second MF. There was no significant difference in the colony formation between the first MF and second MF. The bony repair after the second MF was confirmed. It was observed in subchondral bone plate but it was incomplete. The subchondral bone plate observed at 8 weeks after the second MF was thicker than at 8 weeks after the first MF.
Conclusions: Surgical technique and awls designed for this study were well developed and could be widely used for the animal studies about MF. The second MF could be a useful treatment to restore the failed resurfacing of cartilage after MF. Further systematic study will be needed to evaluate the repair of defects made by MF and the differentiation abilities of MSCs came from bone marrow by the second MF.
Key Words: Mesenchymal stem cell, Bone marrow stimulation, Second microfracture.