W e studied the morphometry of 35 femora from 31 female patients with developmental dysplasia of the hip (DDH) and another 15 from 15 age-and sex-matched control patients using CT and three-dimensional computer reconstruction models. According to the classification of Crowe et al 15 of the dysplastic hips were graded as class I (less than 50% subluxation), ten as class II/III (50% to 100% subluxation) and ten as class IV (more than 100% subluxation). The femora with DDH had 10 to 14° more anteversion than the control group independent of the degree of subluxation of the hip. In even the most mildly dysplastic joints, the femur had a smaller and more anteverted canal than the normal control. With increased subluxation, additional abnormalities were observed in the size and position of the femoral head. Femora from dislocated joints had a short, anteverted neck associated with a smaller, narrower, and straighter canal than femora of classes I and II/III or the normal control group. We suggest that when total hip replacement is performed in the patient with DDH, the femoral prosthesis should be chosen on the basis of the severity of the subluxation and the degree of anteversion of each individual femur.

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We investigate the difference in atomic resolution images between the Si(100)2×1 reconstructed surface with a dangling bond and the Si(100)2×1:H monohydride surface without a dangling bond using noncontact atomic force microscopy. On the Si(100)2×1 surface, the distance between bright spots is 3.2 ±0.1 Å, which is larger than that between silicon atoms. On the Si(100)2×1:H surface, the distance between bright spots is 3.5 ±0.1 Å, which is in good agreement with that between hydrogen atoms. For the first time, individual hydrogen atoms are resolved. This means that the distance between measured bright spots forming dimers is increased by the hydrogen termination.

We performed a modified, rotational acetabular osteotomy through a lateral transtrochanteric approach on 19 hips in 18 patients with a dysplastic joint. Six hips in six patients were operated on using the original approach. The mean age at operation was 28 years (14 to 54) and the mean period of follow-up 2.3 years (1 to 4.4).Clinical evaluation using the Merle d'Aubigné score showed excellent or good results in 76%. Radiologically, 15 hips showed good acetabular remodelling and no signs of progressive osteoarthritis. In ten hips (40%) there was chondrolysis and collapse of the transferred acetabulum or both within one year, although this gave only mild pain in some patients. Factors which were significantly associated with the grade of outcome included age at the time of operation, the thickness of the transferred acetabulum, failure to use a bone graft, and a transtrochanteric approach.