Abstract
Objectives:
Treatment of some cartilage tears in the knee can be reliably treated with an osteochondral autograft transfer (OAT) procedure. A cylinder plug of donor cartilage and bone is extracted from one region of the knee and impacted into place of a recipient region where there is a void of hyaline cartilage. During this procedure, care must be taken when impacting the donor plugs into place. The cartilage on the donor plug is prone to cracking or fracturing if it is impacted with excessive force. The objective of this study was to analyze different donor OAT regions to determine if any area is more resistant to fracture or cracking than other donor sites.
Methods:
Four donor site regions of the knee were tested where the OAT plugs could be harvested for transplant. The four donor regions were the lateral trochlea (LT), medial trochlea (MT), lateral intercondylar notch (LIN), and medial intercondylar notch (MIN). Using eight cadaver distal femurs, a total of 75 cartilaginous plugs were taken from each donor. This resulted in a total of 300 donor OAT plugs from all four donor sites. To harvest the plugs, a 6mm OAT harvest kit (Arthrex, Naples, FL) was used to obtain each donor plug. Each harvested plug was then impacted into a 6 mm hole that was previously created in a sawbones bone surrogate block. The hole in the bone block was created to mimic a cartilaginous defect found in the knee. The tested plugs were impacted with a standardized anvil type system with pre-determined heights that were recoded as heights 1-4. These increasing heights were set to simulate increasing forces applied during impaction. Each plug was only used one time and for only one height. After impaction of each sample, the cartilage of the plug was analyzed. The cartilage was considered intact or cracked based on visual inspection. A chi-square analysis was used to compare the rates of cartilage damage for each donor region and impaction height.
Results:
Seventy-five plugs were tested for each donor region. The specific donor regions had a fracture rate of 40%, 62.5%, 28% and 52.5% for the LIN, MIN, LT, and MT, respectively. There was a significant difference in fracture rate between each donor site (p<0.001). The LT region had the overall lowest rate of fracture at all heights during impaction. The lowest impaction height had an overall fracture rate of 16%, while the highest impaction height had a fracture rate of 50%. With increasing impaction force there was an increase in OAT chondral fracture (p<.001). At the lowest impaction force, the percentage of fractured cartilage was 17.4%, 35.7%, 4.0%, and 6.7% for the LIN, MIN, LT, and MT, with a difference between them (p=.04).
Conclusions:
This study found that the LT donor site provided the overall lowest rate of fracture and withstood the highest forces of impaction of the four donor sites. At lower impaction forces, both the MT and LT had low chondral fracture rates. The OAT procedure is a great option for cartilage tears of the knee. Damage to donor plugs is very possible with high forces during impaction and must be taken into consideration during surgery. The study shows that the LT seems to be more resilient to damage and should be considered when choosing donor sites for patients that may require high impaction forces.
