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Stem subsidence of polished and rough double-taper stems: in vitro mechanical effects on the cement-bone interface.

Kaneuji A, Yamada K, Hirosaki K, Takano M, Matsumoto T - Acta Orthop (2009)

Bottom Line: There was also a statistically significant relationship between compressive force on the cement and cement creep for the polished stems, but no significant relationship was found for rough stems.Stem subsidence in polished stems resulted in compressive force on the cement and cement creep.The mechanical effects that polished taper stems impart on cement at the cement-bone interface probably contribute to their good long-term fixation and excellent clinical outcome.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Kanazawa Medical University, Kahokugun, Japan. kaneuji@kanazawa-med.ac.jp

ABSTRACT

Background and purpose: Many clinical reports have indicated that polished hip stems show better clinical results than rough stems of the same geometry. It is still unknown, however, what the mechanical effects are of different surface finishes on the cement at the cement-bone interface. We compared mechanical effects in an in vitro cemented hip arthroplasty model.

Methods: Two sizes of double-taper polished stems and matt-processed polished stems (rough stems) were fixed into composite femurs. A 1-Hz dynamic load was applied to the stems for 1 million cycles. An 8-h no-load period was set after every 16 h of load. Stem subsidence within the cement, and compressive force and horizontal cement creep at the cement-bone interface, were measured.

Results: Compared to rough stems, stem subsidence, compressive force and cement creep for polished stems were a maximum of 4, 12, and 7-fold greater, respectively. There was a strong positive correlation between stem subsidence and compressive force for polished stems. In contrast, a strong negative correlation was found between stem subsidence and compressive force for rough stems. There was also a statistically significant relationship between compressive force on the cement and cement creep for the polished stems, but no significant relationship was found for rough stems.

Interpretation: This is the first evidence that different surface finishes of stems can have different mechanical effects on the cement at the cement-bone interface. Stem subsidence in polished stems resulted in compressive force on the cement and cement creep. The mechanical effects that polished taper stems impart on cement at the cement-bone interface probably contribute to their good long-term fixation and excellent clinical outcome.

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A composite femur fixed in the tester. Rods were set at the cement-bone interface.
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Figure 0002: A composite femur fixed in the tester. Rods were set at the cement-bone interface.

Mentions: A fixator constructed of machine-structural-use carbon steel and epoxy resin was made, to secure the composite femur during testing. The epoxy resin was formed to the contours of the composite femur. Holes were positioned on the fixator so that they were aligned with those in the composite femur during testing. Thus, the rod protecting the measuring equipment could penetrate both the fixator and the composite femur, enabling measurement at a constant site. The rod that passed through the inner tube was fixed to the face of the medullary canal of the composite femur (Figure 2) and vacuum-mixed cement (Osteo-bond; Zimmer) was injected with a cement gun.


Stem subsidence of polished and rough double-taper stems: in vitro mechanical effects on the cement-bone interface.

Kaneuji A, Yamada K, Hirosaki K, Takano M, Matsumoto T - Acta Orthop (2009)

A composite femur fixed in the tester. Rods were set at the cement-bone interface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2823200&req=5

Figure 0002: A composite femur fixed in the tester. Rods were set at the cement-bone interface.
Mentions: A fixator constructed of machine-structural-use carbon steel and epoxy resin was made, to secure the composite femur during testing. The epoxy resin was formed to the contours of the composite femur. Holes were positioned on the fixator so that they were aligned with those in the composite femur during testing. Thus, the rod protecting the measuring equipment could penetrate both the fixator and the composite femur, enabling measurement at a constant site. The rod that passed through the inner tube was fixed to the face of the medullary canal of the composite femur (Figure 2) and vacuum-mixed cement (Osteo-bond; Zimmer) was injected with a cement gun.

Bottom Line: There was also a statistically significant relationship between compressive force on the cement and cement creep for the polished stems, but no significant relationship was found for rough stems.Stem subsidence in polished stems resulted in compressive force on the cement and cement creep.The mechanical effects that polished taper stems impart on cement at the cement-bone interface probably contribute to their good long-term fixation and excellent clinical outcome.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Kanazawa Medical University, Kahokugun, Japan. kaneuji@kanazawa-med.ac.jp

ABSTRACT

Background and purpose: Many clinical reports have indicated that polished hip stems show better clinical results than rough stems of the same geometry. It is still unknown, however, what the mechanical effects are of different surface finishes on the cement at the cement-bone interface. We compared mechanical effects in an in vitro cemented hip arthroplasty model.

Methods: Two sizes of double-taper polished stems and matt-processed polished stems (rough stems) were fixed into composite femurs. A 1-Hz dynamic load was applied to the stems for 1 million cycles. An 8-h no-load period was set after every 16 h of load. Stem subsidence within the cement, and compressive force and horizontal cement creep at the cement-bone interface, were measured.

Results: Compared to rough stems, stem subsidence, compressive force and cement creep for polished stems were a maximum of 4, 12, and 7-fold greater, respectively. There was a strong positive correlation between stem subsidence and compressive force for polished stems. In contrast, a strong negative correlation was found between stem subsidence and compressive force for rough stems. There was also a statistically significant relationship between compressive force on the cement and cement creep for the polished stems, but no significant relationship was found for rough stems.

Interpretation: This is the first evidence that different surface finishes of stems can have different mechanical effects on the cement at the cement-bone interface. Stem subsidence in polished stems resulted in compressive force on the cement and cement creep. The mechanical effects that polished taper stems impart on cement at the cement-bone interface probably contribute to their good long-term fixation and excellent clinical outcome.

Show MeSH