[Study on the surface quality of prosthetic hip joints].
To evaluate the quality of the joint surface of a prosthetic hip joint, such parameters were measured as roundness, sphericity and roughness of joint surfaces for conventional prosthetic hip joints. Roundness was measured at two cross-sections for spherical and semi-spherical parts; sphericity was deduced from measurements at 25 points using a coordinate measuring machine, and surface roughness was estimated from measurements at two points on the joint surface. The measured values were ranked in three levels, A (five marks), B (three marks) and C (one mark). The marks were totaled for a given prosthetic hip joint, and classified into the following 4 stages as a criterion for evaluation. The stages comprised A (more than 21 marks), B (20 to 18), C (17 to 15) and D (less than 14). The prosthetic hip joint evaluated as A has, on average, roundness, sphericity and roughness of the femoral head and acetabular cup, respectively of less than 0.1 and 20 microns, 5 and 50 microns, and 0.1 and 0.5 microns. (The maximum roughness of the acetabular cup was less than 5 microns.) Only a few products ranked A not only in individual measurements, but also in the total evaluation. This fact strongly supports the view that to be an effective product a prosthetic hip joint should meet at least the A criteria set up for evaluating the surface quality of its femoral head and acetabular cup.
Ogawa
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Department of Orthopaedic Surgery, Okayama University Medical School, Japan.
D005069:Evaluation Studies as Topic; D006622:Hip Prosthesis; D013499:Surface Properties