Mid-term results of 119 Taperloc Microplasty™ femoral stems after a mean 61 months (50-82) of follow-up.

INTRODUCTION: Short stems are not all the same and do not meet the same objectives in terms of shape, fixation and biomechanics. The Taperloc Microplasty™ is a shortened stem. In France, no articles have been published on this subject and very few articles are available in the international literature. We therefore decided to analyse results for this stem after a mean follow-up of 61 months, asking the following questions: (1) Is the survival of the Taperloc Microplasty™ at least equivalent to the best conventional cementless prostheses on the market, i.e. with a 10-year revision rate of less than 5% according to NICE criteria? (2) Have the expected benefits of short stems been confirmed?

HYPOTHESIS: The Taperloc Microplasty™ prosthesis meets the NICE criteria with a revision rate of less than 5% at 10 years.

MATERIALS AND METHODS: This is a retrospective single-surgeon study of 119 prostheses implanted between April 2013 and December 2015. The inclusion criteria were hip arthrosis or avascular necrosis of the femoral head in patients under the age of 70 regardless of height or weight, excluding Dorr type C femurs. The series consisted of 108 patients (11 bilateral total hip arthroplasties (THA)) with a mean age of 58.8±10 years [17-70]; 81 were men and 38 were women.

RESULTS: The results were assessed in 110 hips (103 patients since 9 hips (7 patients) were lost to follow-up) at a mean follow-up of 61±8 months [50-82]. At follow-up the Postel-Merle d'Aubigné (PMA) score was 17.8±0.8 [12-18] and the Oxford score 13.1±3.5 [12-41] (p<0.05 versus pre operative). On X-rays, we identified 9 pedestal signs (7.5%) below the distal end of the stem, 6 calcar atrophies (5%), but no cortical hypertrophy greater than 2 mm, no stem subsidence greater than 5mm, and no radiolucent line indicating the absence of integration. The survivorship at 61 months was 100% (95% CI: 0.905; 1.095), taking femoral revision as the end-point and 98.2% (95% CI: 0.887; 1.077) considering revision for any reason.

CONCLUSION: The Taperloc Microplasty™ stem is equivalent to the best conventional cementless prostheses on the market in selected surgical indications after a mean follow-up of 61 months. The follow-up is still not sufficient to confirm all the benefits expected from this type of implant.

LEVEL OF EVIDENCE: IV, retrospective cohort study.