Does early micromotion of femoral stem prostheses matter? 4-7-year stereoradiographic follow-up of 84 cemented prostheses

TLDR

Roentgen stereophotogrammetry tracked femoral head centre migration in 84 cemented Lubinus SP I hip arthroplasties (58 primary, 26 revisions). After 4–7 years, seven prostheses were revised for painful loosening, and those revisions were preceded by greater subsidence, medial and posterior migration within the first two years, with subsidence >0.33 mm at 6 months or >1.2 mm at 2 years predicting a >50 % revision risk.

Abstract

Roentgen stereophotogrammetry was used to measure the migration of the centre of the femoral head in 84 cemented Lubinus SP I hip arthroplasties (58 primary operations, 26 revisions). Four to seven years later, seven femoral components had been revised because of painful loosening. These implants showed greater subsidence, medial migration and posterior migration during the first two postoperative years than did the hips which had not been revised. Six months after operation, subsidence of more than 0.33 mm combined with a total migration of more than 0.85 mm predicted an increased risk of subsequent revision; the amount of subsidence at two years was an even better predictor. The probability of revision was greater than 50% if the subsidence at two years was 1.2 mm or more.