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J Orthop Sci. 2018 Dec 13. pii: S0949-2658(18)30331-2. doi: 10.1016/j.jos.2018.11.008. [Epub ahead of print]

The optimal combined anteversion pattern to achieve a favorable impingement-free angle in total hip arthroplasty.

Author information

1
Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan.
2
Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8641, Japan. Electronic address: tamonkabata@yahoo.co.jp.

Abstract

BACKGROUND:

There have been no studies on the differences in impingement-free angle that result from different combined anteversion (CA) patterns. The aim of this study was to find the optimal CA pattern for achieving a favorable impingement-free angle, including bony and prosthetic impingement, in total hip arthroplasty.

METHODS:

We evaluated 100 patients with no hip arthritis. We investigated the impingement-free angle (flexion, internal rotation with 90° flexion, extension, and external rotation) after changing the stem and cup anteversions to satisfy several CA patterns [cup anteversion + stem anteversion = 30°, 40°, 50°, and 60°; cup anteversion + 0.7 × stem anteversion = 37.3° (:Widmer's theory); and cup anteversion + 0.77 × stem anteversion = 43.3° (:Yoshimine's theory)] using 3-dimensional templating software.

RESULTS:

The impingement-free angle changed dramatically among the various CA patterns. The optimal CA was changed by various stem anteversion. Only CA: Widmer with stem anteversion of 20° satisfied daily-life range of motion (ROM) requirements (flexion ≥130°, internal rotation with 90° flexion ≥ 45°, extension ≥ 40°, external rotation ≥ 40°).

CONCLUSION:

Good impingement-free angle cannot be obtained with single fixed CA. Different CA patterns should be used, depending on the differences in the stem anteversion. A CA of 30° with 0° ≤ stem anteversion ≤10°; a CA:Widmer with 20° of stem anteversion; a CA of 40° or Widmer with 30° of stem anteversion. When stem anteversion is ≥40°, CA should be decided by each patient's state. Among them, a stem anteversion of 20° with cup anteversion of 23.3° was found to be the best CA pattern.

PMID:
30554937
DOI:
10.1016/j.jos.2018.11.008

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