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. 2010 Oct;81(5):579-82.
doi: 10.3109/17453674.2010.524596.

Stem torsion in total hip replacement

Ernst Sendtner  1 , Schuster Tibor, Roman Winkler, Michael Wörner, Joachim Grifka, Tobias Renkawitz
Affiliations

Stem torsion in total hip replacement

Ernst Sendtner et al. Acta Orthop. 2010 Oct.

Abstract

Background and purpose: The clinical results of THR may be improved by correct femoral torsion. We evaluated the stem position by postoperative CT examination in 60 patients.

Methods: 60 patients requiring total hip arthroplasty were prospectively enrolled in this study. Minimally invasive THR was performed (anterior approach) in a lateral decubitus position and each patient underwent a postoperative CT examination. The position of the stem was evaluated by an independent external institution.

Results: Stem torsion ranged from – 19° retrotorsion to 33° antetorsion. Normal antetorsion (i.e 10–15° according to Tönnis) was present in 5 of 60 patients, so the prevalence of abnormal stem antetorsion was 92% (95% CI: 82–97). We found a stem antetorsion outside the range of 0–25° in 21 of 60 hips. Women had a higher mean stem antetorsion (8.0° (SD 11)) than men (1.5° (SD 10)).

Interpretation: Postoperative stem antetorsion shows a high variability and is gender-related. We suggest precise assessment of stem antetorsion intraoperatively by means of computer navigation, preparing the femur first. In abnormal stem antetorsion, the cup position can be adjusted using a combined anteversion concept; alternatively, modular femoral components or stems with retroverted or anteverted necks ("retrostem") could be used.

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Figures

Figure 1.
Figure 1.
Stem antetorsion measurement. The mechanical axis was defined by 2 points: the center of the femoral head and the center of the caudal contact points of the femoral condyles. “Antetorsion plane” was defined by a third point on the prosthesis representing the direction of the neck. A caudal condylar plane was created orthogonal to the mechanical axis. The angle between the condylar axis projected on this plane and the normal to the “antetorsion plane” subtracted by 90° gave the torsion angle.
Figure 2.
Figure 2.
Range of stem torsion in 60 hips.
Figure 3.
Figure 3.
Distribution of stem torsion in 60 hips. The 10–15° of antetorsion shown in green is considered to be the normal stem antetorsion.
See this image and copyright information in PMC

Comment in

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