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Are component positioning and prosthesis size associated with hip resurfacing failure?

Marker DR, Zywiel MG, Johnson AJ, Seyler TM, Mont MA - BMC Musculoskelet Disord (2010)

Bottom Line: Additionally, the cup and stem-shaft angles as well as component sizes were compared between the 31 hips that failed over the follow-up period and the surviving components to assess for any differences that might have been associated with an increased risk for failure.Surgeon experience was correlated with improved precision of the antero-posterior and lateral positioning of the femoral component.The failures had smaller mean femoral component diameters as compared to the non-failure group (44 versus 47 millimeters).

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Joint Preservation and Replacement, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, 2401 West Belvedere Avenue, Baltimore, MD, USA.

ABSTRACT

Background: Recent studies suggest that there is a learning curve for metal-on-metal hip resurfacing. The purpose of this study was to assess whether implant positioning changed with surgeon experience and whether positioning and component sizing were associated with implant longevity.

Methods: We evaluated the first 361 consecutive hip resurfacings performed by a single surgeon, which had a mean follow-up of 59 months (range, 28 to 87 months). Pre and post-operative radiographs were assessed to determine the inclination of the acetabular component, as well as the sagittal and coronal femoral stem-neck angles. Changes in the precision of component placement were determined by assessing changes in the standard deviation of each measurement using variance ratio and linear regression analysis. Additionally, the cup and stem-shaft angles as well as component sizes were compared between the 31 hips that failed over the follow-up period and the surviving components to assess for any differences that might have been associated with an increased risk for failure.

Results: Surgeon experience was correlated with improved precision of the antero-posterior and lateral positioning of the femoral component. However, femoral and acetabular radiographic implant positioning angles were not different between the surviving hips and failures. The failures had smaller mean femoral component diameters as compared to the non-failure group (44 versus 47 millimeters).

Conclusions: These results suggest that there may be differences in implant positioning in early versus late learning curve procedures, but that in the absence of recognized risk factors such as intra-operative notching of the femoral neck and cup inclination in excess of 50 degrees, component positioning does not appear to be associated with failure. Nevertheless, surgeons should exercise caution in operating patients with small femoral necks, especially when they are early in the learning curve.

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Plot of acetabular cup inclination angle standard deviation in consecutive rolling 50 patient groups.
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Figure 3: Plot of acetabular cup inclination angle standard deviation in consecutive rolling 50 patient groups.

Mentions: The precision of the placement of the femoral component in the coronal plane improved significantly with experience, with a decrease in the antero-posterior stem-neck angle standard deviation from 7 degrees to 5 degrees in the early and late cohorts, respectively (p = 0.012). There was a strong correlation between the number of cases performed by the operating surgeon and the precision of component placement (r = 0.64; p < 0.0001; Figure 1). The precision of the placement of the femoral component in the sagittal plane was similar between the early and late groups, with standard deviations of 7 and 6 degrees, respectively (p = 0.595). A moderate correlation was found between surgeon experience and an improvement in the precision of component placement in this plane (r = 0.37; p < 0.001; Figure 2). The precision of the acetabular cup placement in terms of inclination angle was similar between the early and late groups, with standard deviations of 8 and 7 degrees, respectively (p = 0.275). A weak and clinically insignificant inverse correlation was found between the surgeon's experience level and the precision of acetabular cup placement (r = 0.13; p = 0.027; Figure 3).


Are component positioning and prosthesis size associated with hip resurfacing failure?

Marker DR, Zywiel MG, Johnson AJ, Seyler TM, Mont MA - BMC Musculoskelet Disord (2010)

Plot of acetabular cup inclination angle standard deviation in consecutive rolling 50 patient groups.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2958984&req=5

Figure 3: Plot of acetabular cup inclination angle standard deviation in consecutive rolling 50 patient groups.
Mentions: The precision of the placement of the femoral component in the coronal plane improved significantly with experience, with a decrease in the antero-posterior stem-neck angle standard deviation from 7 degrees to 5 degrees in the early and late cohorts, respectively (p = 0.012). There was a strong correlation between the number of cases performed by the operating surgeon and the precision of component placement (r = 0.64; p < 0.0001; Figure 1). The precision of the placement of the femoral component in the sagittal plane was similar between the early and late groups, with standard deviations of 7 and 6 degrees, respectively (p = 0.595). A moderate correlation was found between surgeon experience and an improvement in the precision of component placement in this plane (r = 0.37; p < 0.001; Figure 2). The precision of the acetabular cup placement in terms of inclination angle was similar between the early and late groups, with standard deviations of 8 and 7 degrees, respectively (p = 0.275). A weak and clinically insignificant inverse correlation was found between the surgeon's experience level and the precision of acetabular cup placement (r = 0.13; p = 0.027; Figure 3).

Bottom Line: Additionally, the cup and stem-shaft angles as well as component sizes were compared between the 31 hips that failed over the follow-up period and the surviving components to assess for any differences that might have been associated with an increased risk for failure.Surgeon experience was correlated with improved precision of the antero-posterior and lateral positioning of the femoral component.The failures had smaller mean femoral component diameters as compared to the non-failure group (44 versus 47 millimeters).

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Joint Preservation and Replacement, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, 2401 West Belvedere Avenue, Baltimore, MD, USA.

ABSTRACT

Background: Recent studies suggest that there is a learning curve for metal-on-metal hip resurfacing. The purpose of this study was to assess whether implant positioning changed with surgeon experience and whether positioning and component sizing were associated with implant longevity.

Methods: We evaluated the first 361 consecutive hip resurfacings performed by a single surgeon, which had a mean follow-up of 59 months (range, 28 to 87 months). Pre and post-operative radiographs were assessed to determine the inclination of the acetabular component, as well as the sagittal and coronal femoral stem-neck angles. Changes in the precision of component placement were determined by assessing changes in the standard deviation of each measurement using variance ratio and linear regression analysis. Additionally, the cup and stem-shaft angles as well as component sizes were compared between the 31 hips that failed over the follow-up period and the surviving components to assess for any differences that might have been associated with an increased risk for failure.

Results: Surgeon experience was correlated with improved precision of the antero-posterior and lateral positioning of the femoral component. However, femoral and acetabular radiographic implant positioning angles were not different between the surviving hips and failures. The failures had smaller mean femoral component diameters as compared to the non-failure group (44 versus 47 millimeters).

Conclusions: These results suggest that there may be differences in implant positioning in early versus late learning curve procedures, but that in the absence of recognized risk factors such as intra-operative notching of the femoral neck and cup inclination in excess of 50 degrees, component positioning does not appear to be associated with failure. Nevertheless, surgeons should exercise caution in operating patients with small femoral necks, especially when they are early in the learning curve.

Show MeSH
Related in: MedlinePlus