Biomechanical evaluation of acetabular cup implantation in cementless total hip arthroplasty.
OBJECTIVE
To report biomechanical properties of the Biologic Fixation System (BFX) acetabular cup impacted into a normal canine pelvis and to compare the effect of implant positioned to and beyond the medial acetabular wall.


METHODS
In vitro cadaveric study.


METHODS
Hemipelves of mature, large-breed dogs (n=6).


METHODS
For each dog, 1 hemipelvis was reamed to the depth of the acetabular wall (group A) and 1 was reamed an additional 6 mm after penetration of the medial cortex of the acetabulum (group B). The hemipelves were implanted with acetabular cups and loaded in compression through a matching femoral prosthetic component until failure. Specimen stiffness, and failure displacement, load, and energy were determined from load and displacement data and results between groups compared with a paired t-test.


RESULTS
Mean failure load was greater in group A (3812 ± 391 N) than group B (2924 ± 316 N; P<.014). No other differences (P>.05) were observed between groups. Bone fracture (n=5) and cup displacement (1) occurred in group A whereas in group B there were 3 fractures and 3 cup displacements.


CONCLUSIONS
Although medial placement of the BFX cup affected compressive failure loads, failure loads for both groups exceeded normal physiologic loads.


CONCLUSIONS
Medial positioning of the acetabular cup does not appear to compromise acetabular implant-pelvic stability under normal physiologic loads. Because arthroplasty candidates often have abnormal acetabular architecture, mechanical properties of the cup placed in acetabula without a dorsal rim should be investigated.
Margalit
Kate A
KA
Veterinary Specialty Hospital, San Diego, CA, USA.
Hayashi
Kei
K
Jackson
Josh
J
Kim
Sun Young
SY
Garcia
Tanya C
TC
Wiggans
K Tomo
KT
Aiken
Sean
S
Stover
Susan M
SM
D000077:Acetabulum / Q000601:surgery*; D000818:Animals; D019644:Arthroplasty, Replacement, Hip / Q000379:methods / Q000662:veterinary*; D001696:Biomechanical Phenomena; D001843:Bone Cements; D004283:Dog Diseases / Q000601:surgery*; D004285:Dogs; D050723:Fractures, Bone / Q000601:surgery / Q000662:veterinary*; D006622:Hip Prosthesis / Q000662:veterinary; D016268:Internal Fixators / Q000662:veterinary*; D008422:Materials Testing / Q000662:veterinary; D013314:Stress, Mechanical
D001843:Bone Cements