Abstract
With dislocation, prevention is more optimal than treatment. Causes of dislocation include patient compliance, soft tissue tensioning, and component malpositioning problems. Dislocation can occur from bone impingement, component impingement, and spontaneously.
Most work on dislocation has evaluated the differences in the propensity for dislocation based on head size. The larger the head to neck ratio the more motion that can be obtained before cup neck impingement occurs. Skirted modular femoral heads decrease the head to neck ratio and in addition the modular necks must be wider because of strength issues. Because of modularity propensity for dislocation has been on the rise.
As wear has been associated with larger head sizes and thinner polyethylene when conventional polyethylene is used, use of larger head sizes was not considered an option for dislocation prevention and treatment. Constrained liners and bipolar components were used instead. If the newer hyper crosslinked polyethylene components do markedly reduce wear it will be possible to use larger head sizes to prevent dislocation. However, there may be problems with bony impingement associated with larger head sizes.
The abstracts were prepared by Mrs Dorothy L. Granchi, Course Coordinator. Correspondence should be addressed to her at PMB 295, 8000 Plaza Boulevard, Mentor, Ohio 44060, USA.
