Biomechanical evaluation of acetabular cup implantation in cementless total hip arthroplasty

Vet Surg. 2010 Oct;39(7):818-23. doi: 10.1111/j.1532-950X.2010.00726.x. Epub 2010 Aug 12.

Abstract

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.

Study design: In vitro cadaveric study.

Animals: 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.

Clinical relevance: 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.

Publication types

  • Evaluation Study

MeSH terms

  • Acetabulum / surgery*
  • Animals
  • Arthroplasty, Replacement, Hip / methods
  • Arthroplasty, Replacement, Hip / veterinary*
  • Biomechanical Phenomena
  • Bone Cements
  • Dog Diseases / surgery*
  • Dogs
  • Fractures, Bone / surgery
  • Fractures, Bone / veterinary*
  • Hip Prosthesis / veterinary
  • Internal Fixators / veterinary*
  • Materials Testing / veterinary
  • Stress, Mechanical

Substances

  • Bone Cements