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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. An illustration of the tester. The measuring rod (R1 and R2) penetrating the fixator and the femur was placed at the cement-bone interface. Compressive force was measured with the load cell (Lc) via the upper rod (R1) in each site. The amount of cement creep was measured via the lower rod (R2). Stem subsidence was measured with the digital dial gauge (DG) contacting the upper end of the stem. B. The actual tester. The inside was inclined 15 degrees from the base on the coronary plane so that the load was applied to the femur head attached to the top of the stem from 15 degrees inside.
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Figure 0003: A. An illustration of the tester. The measuring rod (R1 and R2) penetrating the fixator and the femur was placed at the cement-bone interface. Compressive force was measured with the load cell (Lc) via the upper rod (R1) in each site. The amount of cement creep was measured via the lower rod (R2). Stem subsidence was measured with the digital dial gauge (DG) contacting the upper end of the stem. B. The actual tester. The inside was inclined 15 degrees from the base on the coronary plane so that the load was applied to the femur head attached to the top of the stem from 15 degrees inside.

Mentions: Stem subsidence, and compressive force and cement creep at the cement-bone interface were measured (Figure 3). Stem subsidence was measured using a digital displacement gauge (DTH-A-5, 5 mm; Kyowa Electronic Instruments Co., Ltd., Tokyo, Japan) applied to the proximal lateral aspect of the stem. A positive value represented stem displacement in the distal direction. A load cell (TR20 I 500N/fs, TR20 I 200N/ fs; Kyowa) placed in the inner tube of the rod contacting the cement-bone interface was used to measure compressive force on the cement at this site. A positive value represented a horizontal force from the cement to the cortex.


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. An illustration of the tester. The measuring rod (R1 and R2) penetrating the fixator and the femur was placed at the cement-bone interface. Compressive force was measured with the load cell (Lc) via the upper rod (R1) in each site. The amount of cement creep was measured via the lower rod (R2). Stem subsidence was measured with the digital dial gauge (DG) contacting the upper end of the stem. B. The actual tester. The inside was inclined 15 degrees from the base on the coronary plane so that the load was applied to the femur head attached to the top of the stem from 15 degrees inside.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0003: A. An illustration of the tester. The measuring rod (R1 and R2) penetrating the fixator and the femur was placed at the cement-bone interface. Compressive force was measured with the load cell (Lc) via the upper rod (R1) in each site. The amount of cement creep was measured via the lower rod (R2). Stem subsidence was measured with the digital dial gauge (DG) contacting the upper end of the stem. B. The actual tester. The inside was inclined 15 degrees from the base on the coronary plane so that the load was applied to the femur head attached to the top of the stem from 15 degrees inside.
Mentions: Stem subsidence, and compressive force and cement creep at the cement-bone interface were measured (Figure 3). Stem subsidence was measured using a digital displacement gauge (DTH-A-5, 5 mm; Kyowa Electronic Instruments Co., Ltd., Tokyo, Japan) applied to the proximal lateral aspect of the stem. A positive value represented stem displacement in the distal direction. A load cell (TR20 I 500N/fs, TR20 I 200N/ fs; Kyowa) placed in the inner tube of the rod contacting the cement-bone interface was used to measure compressive force on the cement at this site. A positive value represented a horizontal force from the cement to the cortex.

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