Abstract
Introduction
The use of short stems has been growing in THA for the past five years. As a result, a large number of short stem designs are available in the market place. However, fixation points differ for many of the designs resulting in different radiographic modeling creating confusion when trying to collate to clinical findings. We have created a classification system in an attempted to provide clarity in analyzing radiographic and clinical findings.
Method
Femoral implants described as “short stems” were evaluated. The range of lengths for stem type and the method of achieving initial implant stability was determined. The optimal radiographic position of each of these implants and type of bone remodeling associated with this placement was evaluated. Stems were defined as “short” if the tip reached or was proximal to the metaphyseal-diaphyseal junction. This location on the proximal femur was defined as the place at which the medial-lateral metaphyseal flare became parallel. Stems were then classified as: 1.) Metaphyseal Stabilized; 2.) Neck Stabilized; 3.) Head Stabilized. An analysis of radiographic with a minimum of one year follow up were reviewed and posted as to the classification system
Results
The range of stem lengths for stem type and the method of achieving initial implant stability was determined. A classification of short-stemmed components has been defined, making it possible to evaluate and differentiate both radiographic and clinical findings. Not all so-called short stems exhibit the same radiographic and clinical findings. It also became apparent that the different stabilization points require specific surgical techniques to ensure reproducible good results. Findings for neck stabilized present with different findings as compared to metaphyseal stabilized and head stabilized.
We are optimistic that this classification system will help to compare short-stemmed implants and how they performed to the more traditional convention cementless stems.
