Mathematical calculation of the difference in shortening length after two types of proximal femoral varus and an investigation of their applicable conditions: an own-pair design

Journal of Orthopaedic Surgery and Research

Correspondence

Jing Qu¹  Jian Sun¹  Feng Lian¹  Yong Cui¹ 

[1] Department of Orthopaedics, The Fourth Hospital of Harbin Medical University, 37 Yiyuan Street, Nangang District, Harbin City, Heilongjiang Province, China;

关键词: Developmental dysplasia of the hip;    Varus osteotomy;    Femoral shortening;    Bilateral lower extremity inequality;    Trigonometry;   

DOI  :  10.1186/s13018-022-03462-1

 received in 2022-08-31, accepted in 2022-12-19,  发布年份 2022

来源: Springer

【 摘 要 】

BackgroundThe shortening length of the lower extremity after the proximal femoral osteotomy is an important issue to be considered in preoperative planning of developmental dysplasia of the hip (DDH) in children. There is still a lack of research on shortening the length of the lower extremities in different proximal femoral osteotomy varus styles. We aimed to verify the relationship between the shortening length after “point-to-face” and “face-to-face” varus osteotomy and proposed a formula for calculating the difference in shortening length and verified its feasibility.MethodsFifty-five children with unilateral DDH were enrolled. The preoperative hip CT data were imported into mimics 21, 3-Matic 10 (Materialise, Leuven, Belgium) for femoral reconstruction and simulated osteotomy, and the difference (t) was calculated by directly measuring the length of the proximal femur after osteotomy. d* sinθ was measured in a three-dimensional environment to calculate the difference in femoral shortening length between the two osteotomy methods (t').ResultsThe results of the direct measurement method and the formula measurement method are shown in the table; the differences in the results of the femoral shortening length difference were not statistically significant (P > 0.05). The limits of agreement (95%) of the difference values using Bland–Altman analysis were between − 0.50 and 0.46 mm, with a mean of − 0.02 mm, indicating a high agreement between the two methods. r = 0.99 (P < 0.05) for the Pearson correlation analysis between the direct measurement method and the calculated method showed that the two methods were significantly correlated.ConclusionsThe derived formula can accurately calculate the difference in the shortening length of the proximal femur after “point-to-face” and “face-to-face” varus osteotomy in children with DDH, which is suitable for clinical application.

【 授权许可】

CC BY   
© The Author(s) 2022

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