gms | German Medical Science

Objectives: The pig is an often used animal model for many medical studies since pigs share similarities with humans. For orthopedic experiments, mature animals are required and hence, usually minipigs are used. The topographical anatomy of the knee joint of a novel minipig line, especially breaded for experimental conditions, the "Aachener minipig" was analyzed to provide information for its application as an orthopedic animal model in cartilage, ACL or meniscus repair studies.

Methods: Eight knee joints of four adult female Aachener minipigs (>1 year) were dissected and dimensions of typical anatomical landmarks were measured using a digital caliper. Two hybrid pig knee joints (8-10 month) and three human knee joints (dissection course) were used for comparison. In addition, cartilage-bone samples of the Aachener minipig were assessed histologically.

Results and Conclusion: In comparison to human conditions we found the following peculiarities of the Aachener minipig and pigs in general: (1) The tibia plateaus had convex medial surfaces in the pigs. The lateral tibial plateau was significantly longer and wider than the medial counterpart. The lateral meniscus was significantly longer and thicker than the medial one. (2) The size differences could be explained by the fact that the upper surface of the fibula head was covered by fibrocartilage and completely integrated into the joint surface formed by the lateral tibia plateau in contrast to human conditions. (3) The cartilage thickness of joint areas usually used for cartilage repair studies (middle trochlear groove, central parts of the medial and lateral condyles) were 0.77±0.08 mm thick and hence, might allow chondral cartilage defect models. The overall dimensions of these areas allow the creation of critical sized defects (6 mm in pigs).(4) The ACL of the Aachener minipig and hybrid pig has two individualized attachment sites, completely separated from each other by the lateral anterior meniscotibial ligament. This topography was not comparable to the human anteromedial and posterolateral ACL bundles. The intercondylar notch was in average 6.12±0.61 mm, the anterior intercondylar area 16.25±0.94 mm. (5) No transverse genicular and anterolateral ligaments could be detected in the pig. Several other investigated structures resembled human conditions and we found a comparable zonality of articular cartilage. The dimensions of the AC minipig knee joints might allow also challenging experimental procedures. The peculiarity of the porcine ACL and the size relation of both menisci should be considered using the pig as a model for ACL reconstruction and meniscus repair.