In vivo and ex vivo measurement of polyethylene wear in total hip arthroplasty: comparison of measurements using a CT algorithm, a coordinate-measuring machine, and a micrometer.
BACKGROUND
Determination of the amount of wear in a polyethylene liner following total hip arthroplasty (THA) is important for both the clinical care of individual patients and the development of new types of liners.


METHODS
We measured in vivo wear of the polyethylene liner using computed tomography (CT) (obtained in the course of regular clinical care) and compared it to coordinate-measuring machine (CMM) readings. Also, changes in liner thickness of the same retrieved polyethylene liner were measured using a micrometer, and were compared to CT and CMM measurements. The distance between the centers of the acetabular cup and femoral head component was measured in 3D CT, using a semi-automatic analysis method. CMM readings were performed on each acetabular liner and data were analyzed using 3D computer-aided design software. Micrometer readings compared the thickest and thinnest regions of the liner. We analyzed 10 THA CTs and retrievals that met minimal requirements for CT slice thickness and explanted cup condition. RESULTS - For the 10 cups, the mean difference between the CT readings and the CMM readings was -0.09 (-0.38 to 0.20) mm. This difference was not statistically significant (p = 0.6). Between CT and micrometer, the mean difference was 0.11 (-0.33 to 0.55) mm. This difference was not statistically significant (p = 0.6). INTERPRETATION - Our results show that CT imaging is ready to be used as a tool in clinical wear measurement of polyethylene liners used in THA.
Harris Orthopaedic Laboratory , Massachusetts General Hospital, Boston MA USA.
Dov
D
Goldvasser
Viktor J
VJ
Hansen
Marilyn E
ME
Noz
Gerald Q
GQ
Maguire
Michael P
MP
Zeleznik
Henrik
H
Olivecrona
Charles R
CR
Bragdon
Lars
L
Weidenhielm
Henrik
H
Malchau
D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D020878:Device Removal; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006622:Hip Prosthesis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008422:Materials Testing / Q000379:methods*; D008875:Middle Aged; D020959:Polyethylene; D012086:Reoperation; D014057:Tomography, X-Ray Computed / Q000379:methods
D020959:Polyethylene