Abstract
Introduction
The frequency of revision hip arthroplasty is increasing with the increasing life expectancy and number of individuals treated with joint replacement. Newer porous implants have been introduced which may provide better treatment options for revision arthroplasty. These may require cementation to other prosthesis components and occasionally to bone, however, there is currently no information on how these porous implants interface with cement.
Materials and Methods
Cylindrical bone (control group) and porous metal probes with a diameter and height of 10mm were created and subsequently cemented in a standardized setting. These were placed under tensile and torsional loading scenarios.
In this experimental study, 10 human femoral heads were used to create 20 cylindrical probes with a diameter and height of 10mm. One side was tapered to 6mm for cementation and interface evaluation. A further set of 20 probes of a porous metal implant (Trabecular Metal®) was created with the same geometry. After the probes were created and lavaged, they were cemented at the tapered surface using a medium viscosity cement at a constant cementation pressure (1.2N/mm2). The setup allowed for comparison of the porous metal/cement interface (group A) with the well-studied control group interface bone/cement (group B).
The maximal interface stability of groups A and B were evaluated under tensile and rotational loading scenarios and the cement penetration was measured.
Results
Group A showed a significantly decreased cement penetration under the same cementation pressure than group B, yet the interface showed a significantly more stable interface in the measured tests: larger maximum tensile force (effect size 2.7), superior maximum tensile strength (effect size 2.6), greater maximum torsional force (effect size 2.2), and higher rotational stiffness (effect size 1.5).
Discussion and Conclusion
The porous metal/cement interface displays substantially more stability than does the bone/cement interface. Although these tests evaluate initial stability in an in-vitro setting, they appear promising with regard to their cemented stability. As a result, a multicomponent porous metal construct with cement interdigitation should not compromise the overall implant primary stability.
