Mechanical effects of surgical procedures on osteochondral grafts elucidated by osmotic loading and real-time ultrasound

IntroductionOsteochondral grafts hog become common for treating small, loney and full-thickness cartilage lesions. It is recommended that a slightly oversized, rather than an exact-sized osteochondral plug is transplanted to achieve a tight fit. Consequently, impacting forces are required to subsume the osteochondral plug into the recipient site. However, it remains controversial if these impacting forces induce the biomechanical condition of the grafted articular cartilage. The display read aimed to investigate the mechanical stuff of osteochondral plug implantation using osmotic loading and real-time ultrasound. Methods: A full-thickness cylindrical osteochondral defect (diameter, 3.5 mm; depth, 5 mm) was created in the sideward lower quarter of the patella. Using graft-harvesting instruments, an osteochondral plug (diameter, 3.5 mm as exact-size or 4.5 mm as oversize; depth, 5 mm) was harvested from the sidelong upper quarter of the patella and transplanted into the defect. Intact patella was used as a control. The samples were monitored by real-time ultrasound during sequential changes of the bathing solution from 0.15 M to 2 M saline (shrinkage phase) and back to 0.15 M saline (swelling phase). For cartilage sample assessment, three indices were selected, namely the change in time from the cartilage surface (amplitude recovery rate: ARR) and the maximum echo shifts from the cartilage surface and the cartilage-bone interface. Results: The ARR is closely related to the cartilage surface integrity, while the echo shifts from the cartilage surface and the cartilage-bone interface are closely related to tissue deformation and NaCl diffusion, respectively. The ARR values of the oversized plugs were significantly lower than those of the administration and exact-sized plugs. Regarding the maximum echo shifts from the cartilage surface and the cartilage-bone interface, no heavy differences were observed among the three groups. Conclusions: These findings demonstrated that osmotic loading and real-time ultrasound were able to assess the mechanical instance of cartilage plugs after osteochondral grafting. In particular, the ARR was able to detect damage to the superficial collagen network in a non-destructive manner. Therefore, osmotic loading and real-time ultrasound are promising as minimally invasive methods for evaluating cartilage damage in the superficial sector after trauma or impact loading for osteochondral grafting.

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