Influences of fit and fill following hip arthroplasty using a cementless short-stem prosthesis.

INTRODUCTION: The purpose of this study consisted in examining the effects of fit and fill ratio of the Metha prosthesis (BBraun, Aesculap, Tuttlingen, Germany) on radiological and clinical outcomes at a follow-up of 1 year.

METHODS: 40 patients were included. Fit and fill ratio measurements, radiological and clinical examinations were performed preoperatively and postoperatively. Correlations were established between fit and fill ratio, and potential factors like sex, age, body mass index, Harris Hip Score and changes of radiological signs.

RESULTS: The whole cohort (100%) had a tight fit and fill ratio (>0.8) at the proximal level and at each follow-up. "Champagne-flute" configuration provoked high distal tight-fit and fill ratio. Poor distal fit and fill ratio compared to the proximal and the mid-stem level was measurable at each follow-up (p < 0.05). Correlations between fit and fill ratio and preoperative femur configurations were detectable.

CONCLUSIONS: Implanting the Metha prosthesis induces tight fit and fill ratio at the proximal and coated sections. Preoperative femur configuration should be considered to achieve best fit and fill situation and therefore excellent primary stability. In most cases "normal" and "stove-pipe" configurations provide good proximal fit and fill. Since "champagne-flute" configuration induces undesirable tight distal fit and fill ratio the size of the Metha (®) stem should be adequately increased to achieve a more proximal load transmission.