Is diaphyseal fixation of short neck-retaining stem prostheses related to the size of the implant?

Abstract

Short-stem hip prostheses present variable proximal femoral bone radiological findings. The aims of this study were to analyse, in our patients with implanted collum femoris-preserving (CFP) stems, cancellous bone remodelling, cortical distal hypertrophy and pedestal formation, and the relationship between those radiological changes that suggest distal fixation with the size of the stem. From October 2001 to December 2012 a total of 199 consecutive primary total hip arthroplasties in 180 patients were performed at our department using the CFP stem and followed up for a minimum of 5 years until December 2017. Stress shielding was present in 74% of oversized stems cases, but in normal or undersized stems, stress shielding was present in 8.5%. Cortical hyperthrophy was observed in 49% of the oversized stems and in 6% of the normal or undersized ones. Finally, non-statistically significant differences (p = 0.089) in pedestal formation were found, present in 16.3% of the oversized stems and in 6% of normal or undersized ones. Oversized stems cause more stress shielding and distal cortical hypertrophy in the distal part of the stem, which indicates distal fixation in bigger sizes of stem.