Die Erprobung zementloser Stufenschaftprothesen im Hüft- und Schultergelenk des Hundes

Abstract

In 6 dogs the hip joint was experimentally replaced using a ceramic stepped-stem prosthetic device implanted in the thigh bone. In six other dogs V4A steel stepped-stem prosthetic devices inserted in the arm bone was used for replacing shoulder joint. The six devices replacing the shoulder joint healed up without complications and proved to be mechanically stable. From six devices replacing the hip joint only one was successful; the remaining five implants did not heal up due to fractures of the stem, loosening in the thigh bone and osteomyelitis. We suggest that these different results are based not on the different material, but on the different conditions characteristic for each implantation sites. The devices implanted in the arm bone of the dog, corresponding to the conditions in man, were stressed mainly by pressure and pull. In such conditions the newly formed bone tissue anchoring in the steps on the stem stabilized the device. On the other hand, the biomechanical load on the hip joint replacing device in the dog is represented mainly by rotation at stress, for which the devices are not conceived. The stepped profile of the stem can not work; it twists in the thigh bone and remains unstable causing consequences such as fractures, osteomyelitis and loosening. For experimental testing of bone and joint replacing prosthetic devices of cementless anchoring systems replacing human hip joint and thigh bone we recommend the shoulder joint of the dog instead of hip joint, because of the comparable biomechanics.