Femoral subsidence assessment after hip replacement: an experimental study.
BACKGROUND
In an experimental set up information is to be gained on the error of measurement for subsidence assessment of the stem after hip replacement.


METHODS
Subsidence was measured with a pencil and ruler for four different reference lines and with the computerized EBRA-FCA method. Hip flexion, rotation and abduction were simulated in a standardized way. In a second experimental set up, subsidence was simulated in defined steps.


RESULTS
In the tilt study, the maximum error of measurement was 7 mm with standard methods and 1.7 mm with the EBRA-FCA method. In the subsidence study, there was a maximum error of measurement of 1.9 mm with the standard methods. With EBRA-FCA, the maximum error of measurement was 0.2 mm when taking all radiographs into account.


CONCLUSIONS
The main error of subsidence measurement is caused by tilt of the femur for standard methods and partly can be reduced by EBRA-FCA. EBRA-FCA is more reliable than standard methods but might underestimate the actual subsidence in a clinical situation.
Ilchmann
Thomas
T
Department of Orthopedics, Kantonsspital, Liestal, Switzerland. thomas.ilchmann@ksli.ch
Eingartner
Christoph
C
Heger
Katharina
K
Weise
Kuno
K
D003198:Computer Simulation; D005270:Femur Head / Q000000981:diagnostic imaging; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D016059:Range of Motion, Articular