Rotational stability of different hip revision systems

The authors present an experimental investigation that compares the primary rotational fixation of 4 revision stems. Methods: Each stem was implanted into 4 synthetic femora. Micromotion of stem and bone was measured at defined sites under torque application. Femoral neck osteotomy and AAOS type I and III defects were simulated by reproducible saw lines. Results: Up to a type I defect, all implants are capable of bridging the substance loss in a rotationally stable manner. The relative movements show a dependence both on the bone defect and on implant design. Even within the basic design types clear differences (p < 0.0001) are partially observable. Major differences were seen in type III defects. Whereas the conical stem designs had the ability to bridge the extensive defect the cylindric shapes showed no rotationally stability. Conclusion: As the major fixation area the femoral isthmus plays a decisive role for all tested stems. Due to enormous and partly selective load transmission of the conical stems the cylindrical designs is good for type I defects. In case of an extensive substance loss the decision should be a conical implant

Ротационная стабильность различных ревизионных систем

The authors present an experimental investigation that compares the primary rotational fixation of 4 revision stems. Methods: Each stem was implanted into 4 synthetic femora. Micromotion of stem and bone was measured at defined sites under torque application. Femoral neck osteotomy and AAOS type I and III defects were simulated by reproducible saw lines. Results: Up to a type I defect, all implants are capable of bridging the substance loss in a rotationally stable manner. The relative movements show a dependence both on the bone defect and on implant design. Even within the basic design types clear differences (p < 0.0001) are partially observable. Major differences were seen in type III defects. Whereas the conical stem designs had the ability to bridge the extensive defect the cylindric shapes showed no rotationally stability. Conclusion: As the major fixation area the femoral isthmus plays a decisive role for all tested stems. Due to enormous and partly selective load transmission of the conical stems the cylindrical designs is good for type I defects. In case of an extensive substance loss the decision should be a conical implant.Цель - сравнить первичную ротационную стабильность четырех ревизионных бедренных компонентов. Методы. Каждую из четырех ножек имплантировали в синтетические бедренные кости, после чего измеряли момент вращения, который вызывал микроподвижность между ножкой и костью в определенных участках. С помощью пилы были смоделированы воспроизводимые остеотомии шейки бедренной кости и дефекты I и III типа по классификации AAOS. Результаты. До I типа дефекта включительно все имплантаты выдерживали потерю вещества кости и демонстрировали ротационную стабильность. Относительная нестабильность зависела как от типа костного дефекта, так и от конструкции имплантата. Даже между основными типами конструкций имелись четкие различия (