[Validation of a new in vivo measurement method to measure subsidence of a cemented Exeter femoral stem].
OBJECTIVE
Total hip arthroplasty has become one of the most common procedures in orthopedic surgery. These patients must nevertheless be followed with care due to the risk of instability. Knowledge of early migration behavior can provide an indirect assessment of implant fixation. The purpose of this work was to develop a new measurement tool for early assessment of the femoral component.


METHODS
We analyzed the x-rays of ten Exeter stems (Stryker-Howmedica) implanted between 1996 and 2001 using a simple software designed to calculate the vertical subsidence of each implant. The technical precision and inter-observer reproducibility were checked.


RESULTS
The software provided a precision of 0.14-0.3 millimeters. The overall precision of the technique was 1.2 millimeters. There was no statistically significant inter-observer variability. We observed a mean subsidence of 1.3+/-0.7 millimeters at six Months, followed by no further migration.


CONCLUSIONS
This new method was found to be reliable. It is useful for identifying implant migration at different bone-cement-implant interfaces. The time course of subsidence appears to be important to determine threshold values for failure. This tool provides an easy-to-use method for both retrospective and prospective analysis. With minor modifications of the software program, this tool can be used for other types of implants.
Baillon
R
R
Cliniques Universitaires de Bruxelles, Hôpital Erasme, Bruxelles, Belgique. renaud.baillon@skynet.be
Batarilo
Z
Z
Hinsenkamp
M
M
Rooze
M
M
D000328:Adult; D000368:Aged; D001843:Bone Cements; D005260:Female; D005548:Foreign-Body Migration / Q000175:diagnosis; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012984:Software
D001843:Bone Cements