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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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Related in: MedlinePlus

Stem subsidence and compressive force at the cement-bone interface. Stem subsidence in each period was defined as the mean of values in the two consecutive files (20,000 data sets) after the start of each period. The compressive force in each period was defined as the mean of the collected 960 maximum values of sine waves in the two consecutive files after the start of each period. 57 (3 periods x 19 days) averaged values were used for analysis of stem subsidence and the compressive force, respectively. Simple regression analysis, significances, and correlation coefficients (r): P2; y = 369.44x – 3.5987, R2 = 0.935, p < 0.001, r = 0.9667. P3; y = 191.92x + 66.66, R2 = 0.536, p < 0.001, r = 0.7322. R2; y = –347.08x + 128.55, R2 = 0.779, p < 0.001, r = 0.8837. R3; y = –244.51x + 138.91, R2 = 0.8633, p < 0.001, r = 0.9291. y: force; x: stem subsidence, R2 = r2.
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Figure 0005: Stem subsidence and compressive force at the cement-bone interface. Stem subsidence in each period was defined as the mean of values in the two consecutive files (20,000 data sets) after the start of each period. The compressive force in each period was defined as the mean of the collected 960 maximum values of sine waves in the two consecutive files after the start of each period. 57 (3 periods x 19 days) averaged values were used for analysis of stem subsidence and the compressive force, respectively. Simple regression analysis, significances, and correlation coefficients (r): P2; y = 369.44x – 3.5987, R2 = 0.935, p < 0.001, r = 0.9667. P3; y = 191.92x + 66.66, R2 = 0.536, p < 0.001, r = 0.7322. R2; y = –347.08x + 128.55, R2 = 0.779, p < 0.001, r = 0.8837. R3; y = –244.51x + 138.91, R2 = 0.8633, p < 0.001, r = 0.9291. y: force; x: stem subsidence, R2 = r2.

Mentions: A statistically significant regression was observed between the stem subsidence and compressive force at the proximal medial site with all stems. A significant positive correlation was found between stem subsidence and compressive force in the polished stems while a significant negative correlation was found in the rough stems. This suggests that subsidence of the polished stem may lead to an increase in compressive force at the bone-cement interface while subsidence of the rough stem may induce a decrease in compressive force (Figure 5).


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)

Stem subsidence and compressive force at the cement-bone interface. Stem subsidence in each period was defined as the mean of values in the two consecutive files (20,000 data sets) after the start of each period. The compressive force in each period was defined as the mean of the collected 960 maximum values of sine waves in the two consecutive files after the start of each period. 57 (3 periods x 19 days) averaged values were used for analysis of stem subsidence and the compressive force, respectively. Simple regression analysis, significances, and correlation coefficients (r): P2; y = 369.44x – 3.5987, R2 = 0.935, p < 0.001, r = 0.9667. P3; y = 191.92x + 66.66, R2 = 0.536, p < 0.001, r = 0.7322. R2; y = –347.08x + 128.55, R2 = 0.779, p < 0.001, r = 0.8837. R3; y = –244.51x + 138.91, R2 = 0.8633, p < 0.001, r = 0.9291. y: force; x: stem subsidence, R2 = r2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0005: Stem subsidence and compressive force at the cement-bone interface. Stem subsidence in each period was defined as the mean of values in the two consecutive files (20,000 data sets) after the start of each period. The compressive force in each period was defined as the mean of the collected 960 maximum values of sine waves in the two consecutive files after the start of each period. 57 (3 periods x 19 days) averaged values were used for analysis of stem subsidence and the compressive force, respectively. Simple regression analysis, significances, and correlation coefficients (r): P2; y = 369.44x – 3.5987, R2 = 0.935, p < 0.001, r = 0.9667. P3; y = 191.92x + 66.66, R2 = 0.536, p < 0.001, r = 0.7322. R2; y = –347.08x + 128.55, R2 = 0.779, p < 0.001, r = 0.8837. R3; y = –244.51x + 138.91, R2 = 0.8633, p < 0.001, r = 0.9291. y: force; x: stem subsidence, R2 = r2.
Mentions: A statistically significant regression was observed between the stem subsidence and compressive force at the proximal medial site with all stems. A significant positive correlation was found between stem subsidence and compressive force in the polished stems while a significant negative correlation was found in the rough stems. This suggests that subsidence of the polished stem may lead to an increase in compressive force at the bone-cement interface while subsidence of the rough stem may induce a decrease in compressive force (Figure 5).

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
Related in: MedlinePlus