Limits...
Mathematical evaluation of jumping distance in total hip arthroplasty: influence of abduction angle, femoral head offset, and head diameter.

Sariali E, Lazennec JY, Khiami F, Catonné Y - Acta Orthop (2009)

Bottom Line: The jumping distance was found to decrease as the cup abduction angle increased (0.25 mm each 1 degree for 32-mm head diameter).The JD decreased by 0.92 mm for each 1-mm increase in head offset, showing that head offset was the most important parameter influencing the JD.An increase in offset of the femoral head substantially reduces the jumping distance and it should therefore be avoided.

View Article: PubMed Central - PubMed

Affiliation: Hôpital Pitié Salpétrière, Paris, France. hedisari@yahoo.fr

ABSTRACT

Background and purpose: The jumping distance (JD) is the degree of lateral translation of the femoral head center required before dislocation occurs. The smaller the distance, the higher the theoretical risk of dislocation. The aim of our study was to evaluate this jumping distance and its variation according to the characteristics of the implant, and also the theoretical gain in using large head diameters of above 38 mm.

Methods: The JD was calculated as a function of the cup anteversion and abduction angles, the head diameter, and the head offset (defined as the distance between the center of the femoral head and the cup opening plane). Head diameters of 28, 32, 36, 40, 44 and 48 mm were analyzed. The abduction angle was increased from 0 degrees to 80 degrees with a 10 degree increment. The anteversion angle was increased from 0 degrees to 40 degrees with a 5 degree increment.

Results: The jumping distance was found to decrease as the cup abduction angle increased (0.25 mm each 1 degree for 32-mm head diameter). It increased by 0.05 mm for a 1 degree increase in the anteversion angle. The jumping distance increased as the head diameter increased (0.4 mm each mm diameter for a 45 degree abduction angle). The net gain obtained by increasing the diameter, however, decreased when abduction angle increased (0.25 each mm diameter for 60 degree abduction). The JD decreased by 0.92 mm for each 1-mm increase in head offset, showing that head offset was the most important parameter influencing the JD.

Interpretation: The theoretical gain in stability obtained by using a large femoral head (above 36 mm) is negligible in cases where there is a high cup abduction angle. An increase in offset of the femoral head substantially reduces the jumping distance and it should therefore be avoided.

Show MeSH

Related in: MedlinePlus

The jumping distance is the lateral translation (AB) of the center of the femoral head (t) before dislocation occurs. F is the load force and y is the planar cup inclination angle measured in the frontal plane.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2823207&req=5

Figure 0001: The jumping distance is the lateral translation (AB) of the center of the femoral head (t) before dislocation occurs. F is the load force and y is the planar cup inclination angle measured in the frontal plane.

Mentions: Large head diameter is an attractive option to reduce the dislocation risk after total hip replacement. In fact, Scifert et al. (2001) showed an increase in resisting moment to dislocation of 3.6% per mm increase in head diameter. However, the literature on the use of large head diameters in revision surgery (Beaule et al. 2002, Amstutz et al. 2004, Fricka et al. 2006, Kung and Riers 2007) still shows a failure rate of between 8% and 40%, with no statistically significant difference between standard femoral head sizes (28, 32 mm) and large ones (Kung and Riers 2007). Some authors have proposed the use of jumping distance as a predictive factor for dislocation (Lazennec et al. 2006). The jumping distance is the degree of lateral translation of the femoral head center required for dislocation to occur (Figure 1). The lower the jumping distance, the higher the theoretical risk of dislocation. We evaluated this jumping distance and its variation according to implant characteristics—in particular, the cup abduction, the femoral head diameter, and the head offset, in order to determine the net theoretical gain when using large femoral heads.


Mathematical evaluation of jumping distance in total hip arthroplasty: influence of abduction angle, femoral head offset, and head diameter.

Sariali E, Lazennec JY, Khiami F, Catonné Y - Acta Orthop (2009)

The jumping distance is the lateral translation (AB) of the center of the femoral head (t) before dislocation occurs. F is the load force and y is the planar cup inclination angle measured in the frontal plane.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2823207&req=5

Figure 0001: The jumping distance is the lateral translation (AB) of the center of the femoral head (t) before dislocation occurs. F is the load force and y is the planar cup inclination angle measured in the frontal plane.
Mentions: Large head diameter is an attractive option to reduce the dislocation risk after total hip replacement. In fact, Scifert et al. (2001) showed an increase in resisting moment to dislocation of 3.6% per mm increase in head diameter. However, the literature on the use of large head diameters in revision surgery (Beaule et al. 2002, Amstutz et al. 2004, Fricka et al. 2006, Kung and Riers 2007) still shows a failure rate of between 8% and 40%, with no statistically significant difference between standard femoral head sizes (28, 32 mm) and large ones (Kung and Riers 2007). Some authors have proposed the use of jumping distance as a predictive factor for dislocation (Lazennec et al. 2006). The jumping distance is the degree of lateral translation of the femoral head center required for dislocation to occur (Figure 1). The lower the jumping distance, the higher the theoretical risk of dislocation. We evaluated this jumping distance and its variation according to implant characteristics—in particular, the cup abduction, the femoral head diameter, and the head offset, in order to determine the net theoretical gain when using large femoral heads.

Bottom Line: The jumping distance was found to decrease as the cup abduction angle increased (0.25 mm each 1 degree for 32-mm head diameter).The JD decreased by 0.92 mm for each 1-mm increase in head offset, showing that head offset was the most important parameter influencing the JD.An increase in offset of the femoral head substantially reduces the jumping distance and it should therefore be avoided.

View Article: PubMed Central - PubMed

Affiliation: Hôpital Pitié Salpétrière, Paris, France. hedisari@yahoo.fr

ABSTRACT

Background and purpose: The jumping distance (JD) is the degree of lateral translation of the femoral head center required before dislocation occurs. The smaller the distance, the higher the theoretical risk of dislocation. The aim of our study was to evaluate this jumping distance and its variation according to the characteristics of the implant, and also the theoretical gain in using large head diameters of above 38 mm.

Methods: The JD was calculated as a function of the cup anteversion and abduction angles, the head diameter, and the head offset (defined as the distance between the center of the femoral head and the cup opening plane). Head diameters of 28, 32, 36, 40, 44 and 48 mm were analyzed. The abduction angle was increased from 0 degrees to 80 degrees with a 10 degree increment. The anteversion angle was increased from 0 degrees to 40 degrees with a 5 degree increment.

Results: The jumping distance was found to decrease as the cup abduction angle increased (0.25 mm each 1 degree for 32-mm head diameter). It increased by 0.05 mm for a 1 degree increase in the anteversion angle. The jumping distance increased as the head diameter increased (0.4 mm each mm diameter for a 45 degree abduction angle). The net gain obtained by increasing the diameter, however, decreased when abduction angle increased (0.25 each mm diameter for 60 degree abduction). The JD decreased by 0.92 mm for each 1-mm increase in head offset, showing that head offset was the most important parameter influencing the JD.

Interpretation: The theoretical gain in stability obtained by using a large femoral head (above 36 mm) is negligible in cases where there is a high cup abduction angle. An increase in offset of the femoral head substantially reduces the jumping distance and it should therefore be avoided.

Show MeSH
Related in: MedlinePlus