Bone remodeling in shoulder prosthesis

Aim: The aim of this paper was to try to identify bone remodeling process around stem of uncemented shoulder prosthesis using radiographical indices. Methods: Twenty patients’ radiographs were retrospectively analyzed. Using GIMP, flare index and cortical index were measured on pre-operative radiographs; cortical index, filling index and number of radiolucency lines were measured on postoperative and follow-up radiographs. Two statistical analysis were performed: cross sectional analysis and longitudinal analysis. Results: Cross-sectional analysis showed that cortical index and filling index average values didn’t change over time and there were radiolucency lines in some follow-up radiographs; longitudinal analysis showed that filling index in metadiaphysis was found reversely related to cortical index in the same area and that an increase of filling index at diaphysis was related with an increase of cortical index at metadiaphysis. Conclusion: Indices used in hip prosthesis analysis can be used in shoulder prosthesis analysis too. They show that around the stem, there is a bone remodeling process, similar to what happens in hip prosthesis: if stem exceeds in filling the metadiaphyseal channel there is, at the same level, a bone deposition caused by reaction of integration of the prosthesis; if stem exceeds in filling the diaphyseal channel, there is a bone reabsorption in the metadiaphysis.