Abstract
Objectives:
Addressing cartilage lesions is challenging due to the limited regenerative capacity of articular cartilage. Osteochondral allograft transplantation (OCA) provides a viable solution by transferring mature, viable hyaline cartilage to treat full-thickness osteochondral defects. The success of OCA heavily depends on effective cartilage harvesting due to the tissue’s delicate nature. This study aimed to evaluate techniques related to the emerging use of BioUni® and manual impaction for plug harvesting. Traditionally, these methods were reserved for smaller plugs used in OATS and mosaicplasty procedures. Specifically, the study compared the effects of thermal and mechanical damage on chondrocytes and osteocytes during osteochondral allograft harvesting using manual impaction versus a more traditional coring reamer.
Methods:
Osteochondral grafts were harvested from four porcine knees, resulting in a total of 16 grafts. Both a standard 19.5 mm OATS manual punch device and a 21.5 mm powered trephine device (BioUni® OATS System, Arthrex, Munich, Germany) were used. For consistency, the extraction zones (medial or lateral femoral condyle) were matched to the contralateral knee (Figure 1). Uniformity in extraction sites was maintained, considering that bone mineral density can vary between the medial and lateral condyles. The workstation included force sensors and two thermocouples: one at the cartilage surface and the other at the bone-cartilage interface. Cartilage sections were stained with a live/dead cell stain, and multiple fluorescent images were captured to create mosaics of the cut edges (Figure 2).
Results:
The powered drill caused a significantly higher average surface temperature change (18.53°C) compared to the OATS punch (1.86°C), and the maximum surface temperature change was also greater with the drill (31.62°C vs. 5.62°C) (Tables 1 and 2). Additionally, drill samples exhibited a larger zone of dead cells and more substantial edge tear-out. The OATS punch did not significantly impact the force required for extraction or the extraction time, with OATS procedures averaging 4-6 seconds versus 7-20 seconds for the powered drill. Despite similar maximum force levels, the drill applied force for a longer duration, potentially contributing to a larger zone of dead chondrocytes (2.062 mm2 vs 1.938 mm2).
To mitigate thermal damage to chondrocytes and osteocytes caused by the drill, it is effective to immediately immerse the hemicondyle plug in cool saline after removal. Temperature graphs indicated that heat diffusion through bone and cartilage occurs over time, underscoring the importance of prompt cooling to preserve cellular viability. Our findings contradict previous literature that reports a smaller dead periphery with drill devices. This discrepancy may be due to differences in tool diameters (10 mm for punch devices vs. 16 mm for powered trephines). In our study, comparable sizes (19.5 mm punch vs. 21.5 mm drill) were used, with consistent extraction size and technique.
Conclusions:
Powered drills generate more heat and require longer procedure times compared to OATS punches. OATS punches do not significantly affect the force required or the duration of the extraction process. Therefore, OATS punches are a viable alternative for osteochondral plug extraction, potentially minimizing thermal damage and improving efficiency.
