In total hip arthroplasty (THA), altering the original offset can lead to poor outcome or even complications or revision when the changes are too great. The aim of the present study was to compare femoral offset between short and standard stems. The hypothesis was that the short stems studied provide better control of post-operative femoral offset.
We retrospectively reviewed 100 consecutive THAs using uncemented optimys™ short stems (Mathys, Bettlach, Switzerland), matched to 100 standard stem THAs performed during the same period. The primary endpoint was femoral offset; secondary endpoints were the limb length and cervico-diaphyseal angle.
The mean femoral offset increased by 6.0 ± 7.2 mm overall (p < 0.0001), 4.7 ± 6.7 mm in the short-stem group (p < 0.0001), and 7.2 ± 7.5 mm in the standard stem group (p < 0.0001), with a significant inter-group difference (p = 0.0152). Limb length showed no significant inter-group difference (p = 0.8425). Cervico-diaphyseal angle was increased by surgery overall, and more by standard than by short stems (p < 0.05).
Measurement of femoral offset revealed significant lateralization. It is critical that offset should be maintained in THA. The technique we use increases femoral offset, but the present study showed less increase using short than standard stems. These findings must be borne in mind to achieve good clinical outcome.