In 59 patients, 86 hips with subluxation or hip dysplasia were examined to determine the natural course of the condition and select suitable treatment. Thirty-three percent of the joints (13/39 hips) developed early osteoarthritis from pre-osteoarthritis within an average term of 9.2 years, while the remaining, sixty-six percent (31/47 hips) developed advanced-stage osteoarthritis from early osteoarthritis within an average term of 7.8 years. Patients were classified into advanced and non-advanced groups according to radiographic analysis of the advanced groups according to radiographic analysis of the advance of the disease and statistical analysis was performed. In pre-osteoarthritis, centre-edge angle, slope of the acetabular roof, acetabular head index, acetabular depth ratio and Japanese Orthopaedic Association (JOA) hip score were significant predictors, while in early osteoarthritis, a broken Shenton's line, cranial joint space and JOA score were significant. On the basis of multiple parameters, formulas for predicting development in patients with pre-osteoarthritis, those with early osteoarthritis, and all patients together were established, with an accuracy of 87%, 71%, and 68%, respectively.

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Pitting failures of copper tubes in hot water were investigated in detail. Sample tubes from various tubing lines were collected at three buildings in Tokyo. Two cases of the three were similar and their results are summarized as follows; (1) Water was characterized by high levels of SO42and Cl-, and low ratio of HCO3-/SO42-in comparison with the averages of Japanese river water; (2) Pits were covered with mounds of greenish blue corrosion products containing Cu4SO4(OH)6; (3) Pits contained reddish brown products of Cu2O. Chloride was concentrated at the bottom of the pits, where crystalline CuCl was detected in some cases; (4) The pH value within the pits was 3 to 4. These characteristic features suggest that the pitting corrosion of above cases is classified Type II as many other cases experienced in Japan. It is considered that Cl-in water first forms CuCl as a corrosion product which may hydrolyze to develope an acid and Cu2O in the pit, and that SO42forms the mound of Cu4SO4(OH)6 on the pit, which hinders the acid solution to be washed away from the pit. The low level of HCO3-(low buffer capacity) is in favor of the ready decay of pH value in the pit. Pitting corrosion of the third case showed some different features, particularly with respect to water quality. Since this type of pitting has rarely been reported in Japan, it is difficult at this stage to explain its mechanism.