Instrumented hip joint replacements, femoral replacements and femoral fracture stabilizers

The cyclic variation in both the load and speed experienced during walking was considered in an elastohydrodynamic lubrication (EHL) analysis for artificial hip joint replacements in this study. A general numerical procedure was developed to take both the entraining and squeeze-film actions into the solution of the Reynolds equation in the spherical ball-in-socket coordinate, simultaneously with the elasticity equation, using the Newton-Raphson method. The numerical procedure developed was then applied to an example of hip joint replacements employing an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup against either a metallic or ceramic femoral head under simplified cyclic load and speed conditions. The predicted minimum film thickness was found to stay remarkably constant, despite a large change in the angular velocity and the load. This was attributed to the combined effect of entraining and squeeze-film actions in generating, replenishing and maintaining the lubricating film in artificial hip joint replacements. Furthermore, it was pointed out that the average transient minimum film thickness predicted throughout one cycle was very close to that under quasi-static conditions based upon the average angular velocity and load.

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EVALUATION OF THE APPROPRIATENESS OF HIP JOINT REPLACEMENT TECHNIQUES

International Journal of Technology Assessment in Health Care ◽

10.1017/s0266462300161148 ◽

2000 ◽

Vol 16 (1) ◽

pp. 165-177 ◽

Cited By ~ 10

Author(s):

José M. Quintana ◽

Jesús Azkarate ◽

J. Ignacio Goenaga ◽

Inmaculada Aróstegui ◽

Ignacio Beldarrain ◽

...

Keyword(s):

Avascular Necrosis ◽

Hip Joint ◽

Expert Panel ◽

Group Differences ◽

Indications For Surgery ◽

Hip Joint Replacement ◽

Joint Replacements ◽

Patient Variables ◽

Hip Joint Replacements ◽

Explicit Criteria

Objective: To evaluate the appropriateness of the use of hip joint replacements (HJRs) using explicit criteria developed by an expert panel.Methods: Observational study. Nine hundred ninety-seven patients from five hospitals with a diagnosis of osteoarthritis, avascular necrosis, hip fracture, or revision who were undergoing HJR were consecutively included in the study during a 1-year period. The appropriateness of the indication was judged by explicit criteria. Complications were recorded at the time of the intervention and 3 months postoperatively.Results: Of the 1,030 interventions, 604 were for osteoarthritis, 31 avascular necrosis, 191 fractures, and 204 revisions. No differences were found among the hospitals for the main clinical and patient variables. Indications for surgery were considered appropriate in 59% of cases, uncertain in 32%, and inappropriate in 8%, mainly in the osteoarthritis group. Differences were found in the rates of appropriateness among some centers. The complication rate did not differ among the groups based on the level of appropriateness of the procedure.Conclusions: The appropriate use of HJR, as measured by the criteria established by the panel, identified a moderate percentage of inappropriate indications. Those equivocal and inappropriate cases demand further studies to identify patients with an adequate risk-to-benefit ratio from this procedure.

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