A proposal for the study of cementless short-stem hip prostheses.

BACKGROUND: With the recent evolution of hip arthroplasty, new models of short stems have emerged. So far, we do not have a clear strategy to analyze their outcomes, since there is confusion around the definition of short stem and there is no consensus for their classification.

PURPOSES: The purpose of this study was to review the current state of the art of cementless short stems considering the main design characteristics; it provides a definition of short stem and proposes a classification, grouping them into families by means of a nomenclature that describes them accurately.

MATERIAL AND METHODS: We conducted a search in the PubMed and Scopus databases and consulted various implant manufacturers, foundations devoted to research on joint arthroplasty, organizations of independent experts on medical device analysis, and national arthroplasty registries. The stems studied were classified according to a new nomenclature system.

CONCLUSIONS: We identified 44 different models that share 84 design variables and may be grouped into three types and 16 generic families. The stems were manufactured by 20 different companies. Short stems are those occupying the neck, metaphysis and the proximal aspect of the limit between the metaphysis and diaphysis, regardless of the geometric type of endosteum present. A wide variety of models was identified, with multiple design variables. In order to classify them, it was necessary to design a whole new nomenclature capable of describing them in an unequivocal, unique and distinctive way.