[Relations between degenerative changes in the femoral head and the radiologically determined biomechanical magnitude of effects]

40 femoral heads taken at hip arthroplasty are examined. The position and expansion of cartilage loss are determined and related to the preoperative X-rays. Femoral "bald heads" appear most frequently at the lateral ventral aspect. The angle phi formed by the hip resultant (Pauwels) and the longitudinal axis of the body is related to the CE-angle (Wiberg) as follows: Small CE-angles are associated with large phi and vice versa. Coxa valga (projected CCD-angles greater than 141 degrees) is associated with predominantly lateral location of areas of bone exposure. Low CCD-angles (less than 120 degrees) and large CE-angles (greater than 30 degrees) go along with larger "bald heads". In cases with overweight the expansion of bone exposures does not exceed the amounts found in "normal body weight". Thus bone exposing destruction of cartilage is mainly situated near the point of penetration of the resultant force through the weight bearing surface of the joint. Larger "bald heads" occur favourable at the "deep" acetabula revealing high CE-angles and at low CCD-angles.