Limitations of artificial hip joint mobility due to wear and ceramic cup design

Insufficient range of motion (ROM) of total hip prostheses can lead to impingement, which may result in dislocation, creep and wear of polyethylene cups. Due to wear, polyethylene cups can be penetrated by the femoral head. When using ceramic cups or ceramic cup inserts brittle fracture may occur. Certain designs features and polyethylene wear may restrict joint mobility. In a three-dimensional computer simulation, maximum joint movements of different ceramic cup designs and effects of head penetration into the polyethylene cup were investigated. The range of motion is reduced by increasing head penetration in polyethylene and inadequate ceramic cup design. Modular ceramic cups with non-recessed inserts or inserts protected by a polyethylene ring, and mushroom-shaped ceramic heads should not be used. Total hip arthroplasty should provide sufficient joint mobility, precise positioning of components and low wear bearing couples.