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[Short Stem, Straight Stem or Anatomical Stem: Free Decision or Recommendations?]

The main goal of total hip arthroplasty is to reduce pain. But function, stability, and longevity are also of major importance. Since the inauguration of modern total hip arthroplasty by Charnley, the designs of stems has undergone many changes. The following paper concerns the straight stem, the anatomical stem and the short stem in total hip arthroplasty. It attempts to answer the question as to whether there is a recommendation for the use of a special stem. The straight stem is the oldest of these stem types. Depending on the particular design, the anchorage of these stems may lie in the metaphyseal or the diaphyseal parts of the femur. The closer the contact of the stem is to the diaphyseal part, the greater is the risk of stress shielding. The anatomical stem attempts to match the geometry of the proximal femoral endosteal. This can be helpful to reconstruct the natural load bearing but has also limitations in fitting. The short stem was designed to achieve an anatomical pattern of stress distribution, resection of less bone and reduction in thigh pain. There are additional differences between the designs. But not only the stem design has to be considered. The proximal part of the femur exhibits a great variety of morphologies. Whereas younger patients mostly have secondary osteoarthritis due to deformities, elderly patients may have changes in morphology due e.g. osteoporosis. Depending on these patient-specific factors and bearing biomechanical aspects in mind, the surgeon must choose the stem design. This may require different stem designs with different mechanisms of fixation.