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. 2022 Oct;142(10):2935-2944.
doi: 10.1007/s00402-021-04176-5. Epub 2021 Sep 23.

High varus stem alignment in short-stem total hip arthroplasty: a risk for reconstruction of femoro-acetabular offset, leg length discrepancy and stem undersizing?

Matthias Luger  1   2   3 , Julian Stiftinger  4 , Jakob Allerstorfer  4 , Rainer Hochgatterer  4 , Tobias Gotterbarm  4 , Lorenz Pisecky  4
Affiliations

High varus stem alignment in short-stem total hip arthroplasty: a risk for reconstruction of femoro-acetabular offset, leg length discrepancy and stem undersizing?

Matthias Luger et al. Arch Orthop Trauma Surg. 2022 Oct.

Abstract

Purpose: Short stems are increasingly used in in total hip arthroplasty (THA) because of advantages in bone and soft tissue preservation and reconstruction of hip geometry. Short stems can be inserted in a more varus position compared to conventional straight stems. This poses the risk of final varus misplacement of the femoral component, which is not intended in all femoral short stems.

Methods: We wanted to evaluate the effect of a high varus stem positioning in MIS THA on hip offset, leg length and femoral canal fill index. A series of 1052 consecutive THAs with a singular cementless femoral short stem and press-fit cup was retrospectively screened for inclusion. One hundred six patients with unilateral THA and a contralateral healthy hip met the inclusion criteria. Measurements were carried out on preoperative and 3 months anterior-posterior postoperative radiographs. Patients were divided into Group A (varus stem alignment ≤ 3°) and Group B (varus stem alignment > 3°).

Results: Hip offset (HO) increased significantly in Group B by 4 mm (p = 0.013). No influence on leg length difference was detected in both groups. Preoperative CCD angle was significantly lower in Group B (p < 0.001). Canal Fill Indices (CFI) were significantly lower in Group B (CFI I: p < 0.001; CFI II p = 0.003; CF III p = 0.002).

Conclusion: High varus stem alignment > 3° leads to a statistically significant but minor increase in HO and poses the risk of stem undersizing. A preoperatively low genuine CCD angle pose a risk for varus stem positioning.

Keywords: Femoral offset; Hip offset; Leg length; Short stem; Total hip arthroplasty; Varus.

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Conflict of interest statement

We report personal fees paid to our institution during the conduct of the study from Zimmer Biomet, Europe and from Depuy Synthes Orthopädie Gmbh, Peter Brehm Gmbh outside the submitted work. We report research grants paid to our institution during the conduct of the study from Zimmer Biomet, Europe, Depuy Synthes Orthopädie Gmbh, Peter Brehm Gmbh, Germany, outside the submitted work. One co-Authors (R.H.) discloses an activity as a paid consultant for Zimmer Biomet, Europe, outside the submitted work.

Figures

Fig. 1
Fig. 1
Consort diagram
Fig. 2
Fig. 2
Preoperative measurements: both sides: femoral offset (FO), acetabular offset (AO), vertical position of the center of rotation (COR), leg length difference (LLD); affected hip: Centrum-Collum-Diaphyseal Angle (CCD angle), Cortical Index (CI), Canal Flare Index, Canal to Calcar ratio
Fig. 3
Fig. 3
Both sides: femoral offset (FO), acetabular offset (AO), vertical position of the center of rotation (COR), leg length difference (LLD); affected side: stem alignment, canal fill index I, II and III, cup inclination, cup anteversion
See this image and copyright information in PMC

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