Initial stability of fully and partially cemented femoral stems.
OBJECTIVE
To test the initial stability of a newly designed partially cemented femoral stem in comparison with a fully cemented conventional stem.


METHODS
An in vitro study to determine the interface motion between femoral stem and bone as a response to loading.


BACKGROUND
The aim of the new prosthesis design is a proximal load transfer by a defined partial cement fixation in the proximal femur region and a slim prosthesis stem in the distal region. Before a clinical study can be started, the new stem has to show an initial stability comparable to that of fully cemented prostheses.


METHODS
Six paired fresh cadaveric femora were used for the testing of the new partially cemented stem (Option 3000, Mathys Orthopaedics, Bettlach, Switzerland) and a fully cemented stem (Weber Shaft, AlloPro, Baar, Swizerland). Under cyclic loading up to 1600 N hip joint forces, the interface motion between implants and bone was measured at six locations.


RESULTS
Both stems showed uncritical interface motions below 43 microm. However, the Option 3000 stem exhibited significantly smaller motions in the proximal region and slightly larger movements in the distal regions than the Weber prosthesis.


CONCLUSIONS
The new type of partially cemented stem provided a comparable initial stability to the fully cemented Weber prosthesis. Relevance The high initial stability of the Option 3000 stem justified the clinical use of the new implant. More than 100 implantations in the last three years, with very good preliminary clinical results, support the preclinical findings.
Claes
L
L
Institut für Unfallchirurgische Forschung und Biomechanik, Universität Ulm, Helmholtzstrasse 14, 89081, Ulm, Germany. lutz.claes@medizin.uni-elm.de
Fiedler
S
S
Ohnmacht
M
M
Duda
G N
GN
D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D001843:Bone Cements; D002102:Cadaver; D002484:Cementation / Q000379:methods*; D005269:Femur / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008875:Middle Aged; D009068:Movement; D011474:Prosthesis Design; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties; D014159:Transducers; D016474:Weight-Bearing / Q000502:physiology
D001843:Bone Cements