Effect of limb rotation on radiographic alignment measurement in mal-aligned knees

Abstract Purpose Long-leg-radiography (LLR) is commonly used for the measurement of lower limb alignment. However, limb rotations during radiography may interfere with the alignment measurement. This study examines the effect of limb rotation on the accuracy of measurements based on the mechanical a...

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Autores principales:	Xiaoshu Sun, Bin Yang, Shengzhao Xiao, Yichen Yan, Zifan Liu, Liang Yuan, Xiaohua Wang, Bin Sun, Jie Yao, Yubo Fan
Formato:	article
Lenguaje:	EN
Publicado:	BMC 2021
Materias:	Alignment measurement Long-leg radiography Knee flexion Knee coronal deformity Medical technology R855-855.5
Acceso en línea:	https://doaj.org/article/a51f1a8dcfa04dfca78199d1e58e0bc7
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spelling	oai:doaj.org-article:a51f1a8dcfa04dfca78199d1e58e0bc72021-11-28T12:13:25ZEffect of limb rotation on radiographic alignment measurement in mal-aligned knees10.1186/s12938-021-00956-71475-925Xhttps://doaj.org/article/a51f1a8dcfa04dfca78199d1e58e0bc72021-11-01T00:00:00Zhttps://doi.org/10.1186/s12938-021-00956-7https://doaj.org/toc/1475-925XAbstract Purpose Long-leg-radiography (LLR) is commonly used for the measurement of lower limb alignment. However, limb rotations during radiography may interfere with the alignment measurement. This study examines the effect of limb rotation on the accuracy of measurements based on the mechanical and anatomical axes of the femur and tibia, with variations in knee flexion and coronal deformity. Methods Forty-five lower limbs of 30 patients were scanned with CT. Virtual LLRs simulating five rotational positions (neutral, ± 10 $$^{\circ }$$ ∘ , and ± 20 $$^{\circ }$$ ∘ internal rotation) were generated from the CT images. Changes in the hip–knee–ankle angle (HKA) and the femorotibial angle (FTA) were measured on each image with respect to neutral values. These changes were related to knee flexion and coronal deformity under both weight- and non-weight-bearing conditions. Results The measurement errors of the HKA and FTA derived from limb rotation were up to 4.84 ± 0.66 $$^{\circ }$$ ∘ and 7.35 ± 0.88 $$^{\circ }$$ ∘ , respectively, and were correlated with knee flexion (p < 0.001) and severe coronal deformity (p < 0.001). Compared with the non-weight-bearing position, the coronal deformity measured in the weight-bearing condition was 2.62 $$^{\circ }$$ ∘ greater, the correlation coefficients between the coronal deformity and the deviation ranges of HKA and FTA were also greater. Conclusions Flexion and severe coronal deformity have a significant influence on the measurement error of lower limb alignment. Errors can be amplified in the weight-bearing condition compared with the non-weight-bearing condition. When using HKA and FTA to represent the mechanical axis and the anatomical axis on LLR, limb rotation impacts the anatomic axis more than the mechanical axis in patients with severe deformities. Considering LLR as the gold standard image modality, attention should be paid to the measurement of knee alignment. Especially for the possible errors derived from weight-bearing long-leg radiographs of patients with severe knee deformities.Xiaoshu SunBin YangShengzhao XiaoYichen YanZifan LiuLiang YuanXiaohua WangBin SunJie YaoYubo FanBMCarticleAlignment measurementLong-leg radiographyKnee flexionKnee coronal deformityMedical technologyR855-855.5ENBioMedical Engineering OnLine, Vol 20, Iss 1, Pp 1-13 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Alignment measurement Long-leg radiography Knee flexion Knee coronal deformity Medical technology R855-855.5
spellingShingle	Alignment measurement Long-leg radiography Knee flexion Knee coronal deformity Medical technology R855-855.5 Xiaoshu Sun Bin Yang Shengzhao Xiao Yichen Yan Zifan Liu Liang Yuan Xiaohua Wang Bin Sun Jie Yao Yubo Fan Effect of limb rotation on radiographic alignment measurement in mal-aligned knees
description	Abstract Purpose Long-leg-radiography (LLR) is commonly used for the measurement of lower limb alignment. However, limb rotations during radiography may interfere with the alignment measurement. This study examines the effect of limb rotation on the accuracy of measurements based on the mechanical and anatomical axes of the femur and tibia, with variations in knee flexion and coronal deformity. Methods Forty-five lower limbs of 30 patients were scanned with CT. Virtual LLRs simulating five rotational positions (neutral, ± 10 $$^{\circ }$$ ∘ , and ± 20 $$^{\circ }$$ ∘ internal rotation) were generated from the CT images. Changes in the hip–knee–ankle angle (HKA) and the femorotibial angle (FTA) were measured on each image with respect to neutral values. These changes were related to knee flexion and coronal deformity under both weight- and non-weight-bearing conditions. Results The measurement errors of the HKA and FTA derived from limb rotation were up to 4.84 ± 0.66 $$^{\circ }$$ ∘ and 7.35 ± 0.88 $$^{\circ }$$ ∘ , respectively, and were correlated with knee flexion (p < 0.001) and severe coronal deformity (p < 0.001). Compared with the non-weight-bearing position, the coronal deformity measured in the weight-bearing condition was 2.62 $$^{\circ }$$ ∘ greater, the correlation coefficients between the coronal deformity and the deviation ranges of HKA and FTA were also greater. Conclusions Flexion and severe coronal deformity have a significant influence on the measurement error of lower limb alignment. Errors can be amplified in the weight-bearing condition compared with the non-weight-bearing condition. When using HKA and FTA to represent the mechanical axis and the anatomical axis on LLR, limb rotation impacts the anatomic axis more than the mechanical axis in patients with severe deformities. Considering LLR as the gold standard image modality, attention should be paid to the measurement of knee alignment. Especially for the possible errors derived from weight-bearing long-leg radiographs of patients with severe knee deformities.
format	article
author	Xiaoshu Sun Bin Yang Shengzhao Xiao Yichen Yan Zifan Liu Liang Yuan Xiaohua Wang Bin Sun Jie Yao Yubo Fan
author_facet	Xiaoshu Sun Bin Yang Shengzhao Xiao Yichen Yan Zifan Liu Liang Yuan Xiaohua Wang Bin Sun Jie Yao Yubo Fan
author_sort	Xiaoshu Sun
title	Effect of limb rotation on radiographic alignment measurement in mal-aligned knees
title_short	Effect of limb rotation on radiographic alignment measurement in mal-aligned knees
title_full	Effect of limb rotation on radiographic alignment measurement in mal-aligned knees
title_fullStr	Effect of limb rotation on radiographic alignment measurement in mal-aligned knees
title_full_unstemmed	Effect of limb rotation on radiographic alignment measurement in mal-aligned knees
title_sort	effect of limb rotation on radiographic alignment measurement in mal-aligned knees
publisher	BMC
publishDate	2021
url	https://doaj.org/article/a51f1a8dcfa04dfca78199d1e58e0bc7
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Effect of limb rotation on radiographic alignment measurement in mal-aligned knees

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