» Articles » PMID: 36072553

Deriving Alpha Angle from Anterior-posterior Dual-energy X-ray Absorptiometry Scans: an Automated and Validated Approach

Overview
Date 2022 Sep 9
PMID 36072553
Authors
Affiliations
Soon will be listed here.
Abstract

Alpha angle (AA) is a widely used imaging measure of hip shape that is commonly used to define cam morphology, a bulging of the lateral aspect of the femoral head. Cam morphology has shown strong associations with hip osteoarthritis (OA) making the AA a clinically relevant measure. In both clinical practice and research studies, AA tends to be measured manually which can be inconsistent and time-consuming. We aimed to (i) develop an automated method of deriving AA from anterior-posterior dual-energy x-ray absorptiometry (DXA) scans; and (ii) validate this method against manual measures of AA. 6,807 individuals with left hip DXAs were selected from UK Biobank. Outline points were manually placed around the femoral head on 1,930 images before training a Random Forest-based algorithm to place the points on a further 4,877 images. An automatic method for calculating AA was written in Python 3 utilising these outline points. An iterative approach was taken to developing and validating the method, testing the automated measures against independent batches of manually measured images in sequential experiments. Over the course of six experimental stages the concordance correlation coefficient, when comparing the automatic AA to manual measures of AA, improved from 0.28 [95% confidence interval 0.13-0.43] for the initial version to 0.88 [0.84-0.92] for the final version. The inter-rater kappa statistic comparing automatic versus manual measures of cam morphology, defined as AA ³≥60°, improved from 0.43 [80% agreement] for the initial version to 0.86 [94% agreement] for the final version. We have developed and validated an automated measure of AA from DXA scans, showing high agreement with manually measuring AA. The proposed method is available to the wider research community from Zenodo.

Citing Articles

Reliability and agreement of manual and automated morphological radiographic hip measurements.

Boel F, Riedstra N, Tang J, Hanff D, Ahedi H, Arbabi V Osteoarthr Cartil Open. 2024; 6(3):100510.

PMID: 39262611 PMC: 11387701. DOI: 10.1016/j.ocarto.2024.100510.


Automated radiographic hip morphology measurements: An open-access method.

Boel F, de Vos-Jakobs S, Riedstra N, Lindner C, Runhaar J, Bierma-Zeinstra S Osteoarthr Imaging. 2024; 4(2):100181.

PMID: 39239618 PMC: 7616415. DOI: 10.1016/j.ostima.2024.100181.


A Genome-Wide Association Study Meta-Analysis of Alpha Angle Suggests Cam-Type Morphology May Be a Specific Feature of Hip Osteoarthritis in Older Adults.

Faber B, Frysz M, Hartley A, Ebsim R, Boer C, Saunders F Arthritis Rheumatol. 2023; 75(6):900-909.

PMID: 36662418 PMC: 10374163. DOI: 10.1002/art.42451.


High bone mass and cam morphology are independently related to hip osteoarthritis: findings from the High Bone Mass cohort.

Zucker B, Ebsim R, Lindner C, Hardcastle S, Cootes T, Tobias J BMC Musculoskelet Disord. 2022; 23(1):757.

PMID: 35933372 PMC: 9356486. DOI: 10.1186/s12891-022-05603-3.


Machine Learning-Derived Acetabular Dysplasia and Cam Morphology Are Features of Severe Hip Osteoarthritis: Findings From UK Biobank.

Frysz M, Faber B, Ebsim R, Saunders F, Lindner C, Gregory J J Bone Miner Res. 2022; 37(9):1720-1732.

PMID: 35811326 PMC: 9545366. DOI: 10.1002/jbmr.4649.


References
1.
McHugh M . Interrater reliability: the kappa statistic. Biochem Med (Zagreb). 2012; 22(3):276-82. PMC: 3900052. View

2.
Griffin D, Dickenson E, ODonnell J, Agricola R, Awan T, Beck M . The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. Br J Sports Med. 2016; 50(19):1169-76. DOI: 10.1136/bjsports-2016-096743. View

3.
Tannast M, Siebenrock K, Anderson S . Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know. AJR Am J Roentgenol. 2007; 188(6):1540-52. DOI: 10.2214/AJR.06.0921. View

4.
Faber B, Ebsim R, Saunders F, Frysz M, Lindner C, Gregory J . Osteophyte size and location on hip DXA scans are associated with hip pain: Findings from a cross sectional study in UK Biobank. Bone. 2021; 153:116146. PMC: 8503366. DOI: 10.1016/j.bone.2021.116146. View

5.
Hosnijeh F, Zuiderwijk M, Versteeg M, Smeele H, Hofman A, Uitterlinden A . Cam Deformity and Acetabular Dysplasia as Risk Factors for Hip Osteoarthritis. Arthritis Rheumatol. 2016; 69(1):86-93. DOI: 10.1002/art.39929. View