Is a hollow centralizer necessary when using a polished, tapered, cemented femoral stem?

Figures & data

Figure 1. Left: MS-30 with hollow centralizer; right: MS-30 with solid centralizer. Both stems were fitted with tantalum marker towers at the tip and in the proximal section, supplied by the manufacturer.

Figure 2. Left: the solid, 3-winged, peg-fitted asymmetrical centralizer; right: the hollow, 4-winged open-ended centralizer. The centralizers were available in 2 sizes for each stem size (large and small) and were selected depending on the width of the femoral canal.

Table 1. Patient characteristics

Variable	Hollow	Solid	Total
No. of patients	30	30	60
Mean age, years (range)	69 (55–85)	71 (60–82)	70 (55–85)
Sex (male/female)	17/13	10/20	27/33
Mean BMI (SD)	29.0 (5.9)	27.0 (3.7)	28.0 (5.0)

BMI: body mass index.

Figure 4. Graph showing mean retroversion (Y-rotation) measured with RSA technique, including confidence intervals (bars).

Table 2. Precision of the RSA measurements^a

Axis	Translation, mm	Rotation, degrees
Transverse (X)	0.14	0.24
Longitudinal (Y)	0.08	0.34
Sagittal (Z)	0.14	0.14

a The precision is based on 60 double examinations of the patients in the study. The value given represents the smallest migration that is considered statistically significant and is based on 2 standard deviations of the error obtained. This therefore corresponds to the 95% confidence limit.

Figure 5. Graph showing mean stem subsidence (Y-translation) measured with RSA technique, including confidence intervals (bars).