DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY
REVIEW
Validity and reliability of radiological methods to assess proximal hip geometry in children with cerebral palsy: a systematic review CHRISTELLE PONS 1
| OLIVIER R EMY-N ERIS 2 | B EATRICE M ED EE 1 | SYLVAIN BROCHARD 2
1 Physical Medicine and Rehabilitation Department, University Hospital of Brest, Brest; 2 LaTIM INSERM UMR 1101, Brest, France. Correspondence to Christelle Pons at CHRU, H^opital Morvan, Service de Medecine Physique et de Readaptation, 2 avenue Foch, 29609 Brest Cedex, France. E-mail:
[email protected]
PUBLICATION DATA
Accepted for publication 19th March 2013. Published online 4th June 2013.
AIM The aim of this systematic review was to assess the current validity and reliability of radiological methods used to measure proximal hip geometry in children with cerebral palsy. METHOD A search was conducted using relevant keywords and inclusion/exclusion criteria of the MEDLINE, CINALH Plus, Embase, Web of Science, Academic Search Premier, The Cochrane Library, and PsychINFO databases. RESULTS The migration percentage using X-rays showed excellent reliability and concurrent validity with three-dimensional (3D) measurements from computed tomography (CT) scans. The acetabular index, measured using X-rays had good reliability but moderate concurrent validity with 3D CT measurements; 3D CT scan indexes had greater reliability. The measurement of the neck shaft angle using X-rays showed excellent concurrent validity with measurements from 3D CT scans and excellent reliability. Regarding femoral anteversion, one study found an excellent correlation between two-dimensional CT and clinical assessment and excellent reliability. Two others showed less evidence for the use of CT ultrasounds. INTERPRETATION Most of the X-ray-based measurements showed good to excellent metrological properties. More metrological evidence is needed for the assessment of femoral anteversion. Magnetic resonance imaging and ultrasound-based measurements have great potential although very little metrological evidence is available.
Hip deformities occur in over one-third of children with cerebral palsy (CP) and are the second most common musculoskeletal deformity after equinus.1–3 The femoral head frequently migrates relative to the acetabulum, which can lead to subluxation causing pain and functional limitations.4 Surveillance of hip deformity throughout growth is a challenge in this population.5–7 Hip migration has been shown to be mostly associated with acetabular dysplasia, increased femoral neck-shaft angle, and increased femoral anteversion.2,8–11 These parameters are used in clinical decision-making regarding interventions2,10,12 such as physical therapy, positioning, botulinum toxin injections or surgical interventions, such as adductor tenotomy, derotational, or varising osteotomy.13–15 Because clinical evaluation of proximal hip geometry is limited to the measurement of femoral anteversion and joint range of motion, radiologically-based measurements are required to provide a detailed assessment and to ensure a reliable follow-up throughout growth, pre- and post intervention, or in research studies. The metrological properties of such measurements have not been specifically reviewed with regard to the evaluation of hip deformities found in children with CP. Numerous techniques are described in the literature, in studies of varying quality, making analysis difficult. © 2013 Mac Keith Press
The main aim of this paper was to review the evidence of the metrological properties of image-based measurement of proximal hip geometry in children with CP, including hip migration, acetabular dysplasia, femoral neck shaft angle, and femoral anteversion. More specifically we aimed to (1) collect, evaluate, and report the data in studies that assessed the concurrent validity and reliability of imaging methods; (2) report the threshold for ‘real change’ when available; and (3) propose future research.
METHOD Database search and selection process Articles were identified through a comprehensive search of the following computerized bibliographic databases: MEDLINE (1949-07/2012), CINALH Plus (1937-07/2012), Embase (1947-07/2012), Web of Science (1898-07/2012), Academic Search Premier (1975-07/2012), The Cochrane Library, and PsychINFO (1967-07/2012). The search used the following Medical Subject Headings (MeSH) terms and text words, combining the keywords in order to achieve exhaustivity: (1) cerebral palsy; (2) (keywords relative to the hip or femur) ‘acetabular dysplasia’, ‘acetabular index’, ‘hip migration’, ‘hip subluxation’, ‘hip dysplasia’, ‘femoral anteversion’, ‘neck-shaft angle’, ‘coxa DOI: 10.1111/dmcn.12169
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valga’; (3) (keywords relative to the imaging type) ‘radiography’, ‘X-ray’, ‘tomography’, ‘CT scan’, ‘ultrasonography’, ‘ultrasound’, ‘echography’, ‘MRI’, ‘biplanar radiography’, ‘biplanar X-ray’; and (4) (keywords relative to metrological properties) ‘measurement’, ‘measure’, ‘validity’, ‘reliability’, ‘repeatability’. Two reviewers (BM and CP) independently assessed the papers by title and abstract with regard to the inclusion and exclusion criteria described below. Consensus for the inclusion/exclusion of relevant articles was reached by discussion. To be included, studies had to meet the following criteria: (1) original articles published in peer-review journals excluding conference proceedings; (2) studies including children or young adults below the age of 20 years with CP; (3) studies involving evaluation of imaging-based measurement of proximal femoral geometry (acetabular dysplasia, hip migration, neck-shaft angle or femoral torsion); and (4) studies reporting data regarding reliability and/or concurrent validity of imaging techniques. The exclusion criteria were (1) studies which were not in English; (2) studies including CP and other pathologies for which it was not possible to extract the data of the children with CP; (3) studies before 1980 were reviewed and were considered inappropriate because they involved radiological methods that are now unused;16,17 (4) studies showing concurrent validity between different measures measuring the same concept using the same material (e.g. migration percentage and centre-edge angle measuring hip migration in the same anteroposterior X-ray as in Reimers18) were also excluded on the basis that the other studies comparing the same concept with different devices provided more evidence. Studies that analysed correlations between the different measures of proximal hip geometry without carrying out a metrological evaluation were also excluded (e.g. Abel et al.8). The references of the selected articles were also searched in order to complete the selection process. Data items were extracted using a standardized form (see Tables I and III).
Quality and metrological assessment Since no standardized quality assessment tools are available for the evaluation of articles in this field, a customized quality assessment scale was developed based on the literature. The aim of this scale was to provide both an assessment of the intrinsic quality of each article (maximum score 28) and an assessment of the metrological evidence supporting the method evaluated (maximum score 10). The total score was named the Q-score and is out of 100 (Table SI, online supporting information). The first part of the scale was based on previously published quality checklists for systematic reviews or scales assessing the quality of studies included in systematic reviews. These scales included questions focusing on the study design and quality of the reporting of the methodology and results.19–22 The metrological part of the scale was based on evidencebased medicine in radiology23 and studies providing examples of scales to evaluate metrological articles.24,25 1090
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• • •
What this paper adds Most X-ray based measurements have good to excellent metrological properties. More metrological evidence is needed for the assessment of femoral anteversion. MRI- and ultrasound-based measurements have great potential but little metrological evidence is available regarding their use.
The metrological score reflects the amount of metrological evidence brought by an article for the method considered. The rating of the quality assessment was carried out by two observers (CP and SB) independently and disagreements were then resolved by consensus. In this review, an intraclass correlation coefficient (ICC) between 0 and 0.20 was considered as low, 0.21–0.40 fair, 0.41–0.60 moderate, 0.61–0.80 good and 0.81–1 as excellent. The r or K coefficient was considered as 0.21–0.40 fair, 0.41–0.60 moderate, 0.61–0.80 good, and 0.81–1 as excellent.26–28 Although we acknowledge the limits of using such simple definitions, we decided to use this system for clarity and to enable comparisons between studies.27,28 Because it was impossible to combine the results owing to the different statistical methods used, measurement errors estimating a statistical value for true change are reported as they were reported in each article.
RESULTS References and explanations of the measurements taken from images can be found in Table SII (online supporting information). Figures 1 and 2 provide a visual representation of the main measurements described below. Selection process After duplicates were removed, 962 articles were automatically extracted from the databases and 19 articles fitted the inclusion and exclusion criteria: 13 from the PubMed database, three from other databases, and three found during the reference check. The methodology of each study is summarized in Tables I and II and the results of each study in Tables III and IV. Five articles came from the same team29–33 and three came from another team.10,34,35 Quality assessment The quality rating scale is presented in Table SI. The principal aim of 13 out of the 19 studies was metrological. The mean Q-score was 65/100 (SD 14). Two articles had scores greater than 80, five articles had scores between 70 and 80, seven articles had scores between 60 and 70 and five articles had scores lower than 60/100. Measurement of hip migration The hip migration percentage as first proposed by Reimers in 198018 was evaluated in eight studies (mean Q-score 67).32,35–41 Except for the Gose et al.35 study (Q-score 55), the studies found only evaluated the use of anteroposterior X-rays for the assessment of femoral head migration. Gose et al.35 found excellent concurrent validity between
migration percentage and the degree of migration in the frontal plane using a three-dimensional (3D) model of migration based on 3D computed tomography (CT). The seven other studies examined the reliability of migration percentage, all showing that intra- and interrater reliability was good to excellent. Results for standard error of measurement (SEM) 9 1.96, mean + 2SD, and 95% confidence intervals were reported to be 5.8%, 10%, and 12.9% respectively, for one measurer and 11%, 11.5%, and 22% respectively, for different measurers depending on the study36,37,39 (Q-scores 74, 74, 71). Using the lateral edge of the acetabular roof was more reliable than using the ‘sourcil’ of the acetabulum, as described by Kim et al.38
Measurement of acetabular dysplasia The acetabular index, as proposed by Hilgenreiner,42 using anteroposterior X-rays, was evaluated in three studies (Q-scores 74, 61, 55, mean 63).35,39,41 The acetabular index showed moderate concurrent validity with measures carried out using 3D CT scans.35 The intrarater reliability of the acetabular index was found to be excellent39 and the interrater reliability good in two studies.39,41 Results for SEM*1.96 was reported to be 2.6° for a single assessor and 5.9° for different assessors.39 Morphological axial two-dimensional (2D) measurements of the acetabulum including anterior, posterior, and acetabular anteversion,33 showed moderate concurrent validity with 3D measures using reformatted slices from a 3D CT scan realized before osteotomy (r=0.45–0.49, p0.05). Intra- and inter-reliability of the different 2D measures were good to excellent (mean differences between 0.7° and 5.8°, Q-score 92). Three-dimensional CT was used to evaluate different measurements in four studies.29,31,34,35 Chung et al.31 visually assessed acetabular defects using 3D images and found moderate to good intra- and interrater reliability (Q-score 63). In a later study, the same team evaluated three directional indices of acetabular geometry calculated from reformatted slices from 3D CT scans and found excellent intra- and interrater reliability29 (Q-score 68). In two different studies, Gose et al.34,35 showed that the intra- and interrater reliability of using a best-fit plane of the active surface of the ilium to define the orientation of the acetabulum was excellent, and there was moderate concurrent validity with plain radiography (Q-scores 55, 74). Measurement of neck-shaft angle and head-shaft angle The neck-shaft angle was evaluated in three studies10,30,32 (Q-scores 55, 68, 89; mean 71) and the head shaft angle in two studies32,43 (Q-scores 53, 68; mean 61). The neck-shaft angle measured using anteroposterior X-ray showed an excellent correlation with the neck-shaft angle measured using 3D CT reformatted slices30 and a good correlation with the 3D models issued from segmentation.10 The intraand interrater reliability of X-rays for the measurement of neck-shaft angle was excellent;30,32 the intrarater reliability
for head-shaft angle was good and the interrater reliability was good to excellent.32,43 Chung et al.30 showed that 90% of the measurement of neck-shaft angle using X-rays for the same rater was within 10° (Q-score 89). The same authors reported the neck-shaft angle measured using 3D CT scans (reformatted slices) to be a highly reliable method.
Femoral anteversion Three studies evaluated in vivo measures of femoral anteversion in children with CP30,44,45 (mean Q-score 53). Chung et al.30 (Q-score 89) found an excellent correlation between measurements from 2D CT scans (a method using two slices through the femoral neck) and the trochanteric prominence angle test, even though the later overestimated the CT scan by a mean of 4.8° (SD 8.4). They reported excellent intra- and interrater reliability of the 2D CT scan measurement. Miller et al.44 (Q-score 42) evaluated the concurrent validity of two 2D CT scan methods (using measurements taken from a single slice or two laminated sections on the neck and flat surface) and two measurements using ultrasound (head-neck and flat-surface measure). The correlation of the two CT scans with ultrasound-based femoral head-neck measures was moderate, whereas with the ultrasound-based flat-surface measurements were good. Mahboubi et al.45 (Q-score 29) evaluated the concurrent validity of two methods based on two different CT scan slices: the first involved superimposition of a slice from the capital femoral epiphysis on a slice through the femoral neck and the second was Hernandez’s method46 using one slice. The correlation between the two methods was excellent even though the authors reported differences of more than 10° between the two measurements in some patients. The Robin and Graham classification Robin et al.47 developed a six-grade radiological classification for children with CP at bone maturity based on qualitative indices and the measurement of the migration percentage. This classification was assessed in three articles34,47,48 (Q-scores 63, 71, 74, mean 68). It was originally applied to children with CP at skeletal maturity (closure of triradiate cartilage). The intra- and inter-observer reliability were excellent in this ‘matured population’48 (Q-score 71). The agreement between ‘estimated’ hip grade and true hip grade based on migration percentage was good to excellent. The percentage of agreement between the four qualitative morphological features of the classification and the hip grading based on migration percentage was excellent47 (Q-score 63). More recently, a good correlation between the grades of classification and measurements from 3D CT scans was also found in a population of children aged between 2 years and 7 years.34 DISCUSSION The aim of this systematic review was to evaluate existing metrological evidence for image-based measurements of hip geometry in children with CP. The metrological Review
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Table I: Population and methodology of articles evaluating hip migration, acetabular morphology and of the Robin and Graham classification
Study
Type of study
Number of hips
Number of children
Mean Age/ range/SD
Hip migration Cliffe et al.36
P
40
20
30mo–10y
GMFCS level IV: 10 V: 10
Anteroposterior X-ray, two radiographs taken the same day
Pelvis and hips in neutral position
Migration percentage
Faraj et al.37
R
44
22
2–8y
–
Anteroposterior X-ray
Migration percentage
Kim et al.38
R
152
100
–
Anteroposterior X-ray
Pountney et al.40
R
20
–
7y 11mo (SD 1y 6mo) –
Hip joints in neutral position, without ab/adduction Coxae in neutral position
–
Anteroposterior X-ray
Pelvis and hips in neutral position
Population description
Radiological device
Posture control Y=yes N=not reported
Measure
Migration percentage Modified migration percentage Migration percentage (use of a drafting arm)
Acetabular morphology Chung et al.31 R 54
27
7y 2mo (SD 2y 4mo)
Spastic quadri:19 dipl: 6 mixed: 2
3D CT
N
Chung et al.29
P
17
12
8y 1mo (5y 11mo – 13y 2mo)
12 spastic quadri GMFCS III: 1 IV: 8 V: 3
3D CT
N
Park et al.33
P
22
16
8y 4mo (SD 2y 2mo)
Spastic quadri GMFCS III: 2 IV: 8 V: 6
3D CT
N
150 (102 for concurrent study) 91/20 (for reliability study of CT angles)
75
5y 5mo (2y 8mo– 6y 11mo) 5y 2mo (2y 7mo– 6y 10mo)
Spastic dipl: 60, quadri: 15 GMFCS II: 17 III: 34 IV: 16 V:8 Spastic dipl: 66, quadri: 25 GMFCS II: 9 III: 42 IV: 32 V: 8 Robin and Graham classification II: 4 III: 20 IV: 63 V: 4 GMFCS I: 146 II: 109 III: 69 IV: 42 V: 18 307 dipl and quadr, 77 hemi –
Anteroposterior X-ray, 3D CT
N
Migration percentage, acetabular index
Anteroposterior X-ray 3D CT
N
Robin and Graham classification
Anteroposterior X-ray
Supine position, hips in internal rotation
Migration percentage
Anteroposterior X-ray
Pelvis and hips in neutral position N
Migration percentage, acetabular index
Multiple evaluations R Gose et al.35
Gose et al.34
R
Lee et al.32
R
51 out of 384
51 out of 384
9y 1mo (3y – 17y)
Parrott et al.39
R
20
20
Segev et al.41
R
20
10
32mo (11mo– 8y 5mo) –
–
Anteroposterior X-ray
Hip classification Murnaghan R et al.48
42
42
14–19y
–
Anteroposterior X-ray
Robin et al.47
268
134
16y 4mo (14y –19y 1mo)
GMFCS level I: 29 II: 25 III: 27 IV: 24 V: 29
Anteroposterior X-ray
R
91/20 (3DCT)
Pelvis and hips in neutral position N
3D visual assessment of acetabular dysplasia (anterior, posterior or global defect) Three directional indexes (anterosuperior, superolateral, posterosuperior) From reformatted axial plane: anterior/posterior acetabular indexes and acetabular anteversion
Acetabular index, centre-edge angle, migration percentage Robin and Graham Classification Robin and Graham classification
R, retrospective; P, prospective; GMFCS, Gross Motor Function Classification System; quadri, quadriplegic; dipl, diplegic; hemi, hemiplegic; 3D, three-dimensional; ICC, intraclass correlation coefficient; SEM, standard error of measurement; MAD, median absolute difference; LA, limits of agreement; RMSE, root mean square error.
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Comparison with another technique
Examiners: qualifications and years of experience
Number of examiners
Number of trials by sessions/number of sessions
–
2
Paediatric radiologists
Interpretation by two radiologists of the two radiographs for each children twice
–
2
Orthopaedic trainees
2/2
–
2
Rehabilitation doctors
–
3
–
Assessment
Statistical analysis
Intra- and inter-reliability, assessment of the effect of positioning, interobserver error and variations in observer technique over time Intra- and inter-reliability within and between sessions
Mean, SD, Pearson’s correlation coefficient, ICC
1/3
Intra- and inter-reliability
ICC, SEM
–
2/2
Intra- and inter-reliability
Bland and Altman (LA)
4
20: 5y/4y/trainee
1/2
Intra- and inter-reliability
–
3
20: 5y/chief resident
1/2
Intra- and inter-reliability
Kappa,% of agreement (rate of people classifying the acetabulum in the same class) ICC, Mean difference (range)
Three-directional indexes (anterosuperior, posterosuperior) for pre- and post-osteotomy
4
20y/6y/5y/research assistant
1/2
Intra- and inter-reliability, concurrent validity
Sample size, ICC, Pearson correlation coefficients, Paired t test and Wilcoxon signed rank test
3D migration, lateral opening angle 3D migration, lateral opening angle, sagittal inclination angle
–
–
–
Concurrent validity
Spearman rank correlation coefficient
2 (for reliability study of CT angles)
–
1/2
Concurrent validity Intraand inter-reliability (CT angles)
Kruskal–Wallis, ICC, RMSE
–
2
8y/3y orthopaedic surgeons
1/1
Interrater reliability
Calculate sample size for reliability, ICC
–
5
1–3y research physiotherapists
1/2
Spearman, Wilcoxon, ANOVA, ICC, SEM
–
5
Senior orthopaedic surgeons
1/3
Intra- and inter-reliability within and between sessions Intra- and inter-reliability
–
4 surgeons, 4 physiotherapists
1/2
Intra- and inter-reliability, concurrent validity
ICC, asymptotic symmetry test
Migration percentage
2
2 residents/2 surgeons: 4–10y/physiotherapists 16–26y –
1/1
Concurrent validity
Agreement percentages
MAD, Kruskal–Wallis, Mann Whitney U
ANOVA: variances and standard deviations, ICC, paired t test
sional; ICC, inror.
Review
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Table II: Population and methodology of articles evaluating the neck-shaft angle, head-shaft angle, and femoral anteversion Type of study R=retro P=pro
Number of hips
Neck shaft angle, head shaft angle Foroohar R 10 for et al.43 reliability (out of 70)
Gose et al.10 R Lee et al.32
R
Femoral anteversion Mahboubi R et al.45
Miller et al.44
R
Number of children
Mean age (y)/ range /SD
Population description
Posture control (NR=not reported)
Radiological device
Anteroposterior Radiographs in external Group 1: 15 patients Group 1: 8y X-ray rotation excluded with spastic CP 1mo Group Group 2: 10 patients 2: 7y 8mo with spastic CP, need Group 3: 7y surgical intervention Group 3: control NR 73 dipl, 20 quadri GMFCS 3D CT X-ray 186 93 5y 4mo (2y level II: 20 III: 41 IV: 7mo – 6y 22 V: 10 10mo) Anteroposterior Supine, hips in internal 9y 1mo GMFCS: I: 146 II: 109 III: 384, 51 384, 51 X-ray rotation (3y – 17y) 69 IV: 42 V: 18 307 dipl (out of 384) (out of 384) and quadr, 77 hemi for the for the reliability reliability session session 39
18 (out of 30)
18 (out of 30)
3 – 15y
Patients with coxa valga, NSA>140°
CT
NR
80
40
7y 7mo (3y–16y)
–
Ultrasound CT
Ultrasound: supine, legs flexed over the end of the table and parallel to each other CT: NR
11y (5y – 20y)
GMFCS level I: 5 II: 11 III: 11 IV: 7 V: 2 6 hemi, 25 dipl, 5 quadri
Anteroposterior Supine, hips in internal X-ray rotation
Femoral anteversion and neck shaft angle Chung P 36 36 et al.30
CT
NR
CT
NR
R, retrospective; P, prospective; quadri, quadriplegic; dipl, diplegic; hemi, hemiplegic; 3D, three-dimensional, ICC, intraclass correlation coefficient.
evidence for the use of the four main parameters defining hip geometry in this population varied depending on the parameter and the imaging and measurement techniques used. After discussion of the evidence for each parameter, the main limitations of this review are discussed and perspectives are highlighted.
Hip migration Of all the parameters assessed, the metrological properties of the migration percentage have been the most studied. This parameter was shown to have good concurrent validity and good to excellent intra- and interrater reliability. The reliability of migration percentage measurement tends to 1094
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increase with the size of the femoral head and age.39 A threshold for true change has been defined between 5.8% and 11.5% depending on the article,36,39 however, this threshold is greatly increased if the measurer is inexperienced.37 The results of this review show that, to date, there is a lack of studies that have evaluated the use of 3D images to assess hip migration in children with CP. In the light of the current literature, migration percentage appears to be the most valid and reliable technique for the surveillance of hip migration in children with CP. Some suggestions have been made in the literature to improve reliability and to reduce errors: (1) reliability may be increased by providing more specific anatomical landmarks for measurements of the acetabulum,
Comparison with another technique
Measure
Number of examiners
Number trials by sessions/ number sessions
Qualifications and years of experience
Statistical analysis
Assessment
X-ray head shaft angle
–
3
Orthopaedic residents
1/3
Intra- and interrater reliability
ICC
3D CT neck shaft angle
X-ray neck shaft angle
–
–
–
Concurrent validity
Spearman rank correlation test
X-ray neck-shaft angle and X-ray head-shaft angle
–
2 for reliability
Orthopaedic surgeons 8/3y (reliability)
1/1
Interrater reliability
Calculate sample size for reliability, ICC for continuous data and kappa for categorical data; Pearson correlation coefficient
CT femoral anteversion, superimposition of two proximal slices Head-neck ultrasound or flat-surface ultrasound
CT femoral anteversion, (one proximal slice)
–
–
–
Concurrent validity
–
CT femoral anteversion CT flat-surface method
–
–
–
Concurrent validity
Correlation coefficient
X-ray neck-shaft angle
CT reformatted slices neck shaft angle
3
–
1/2
Sample size, ICC, Pearson rank correlation coefficient
CT reformatted slices neck-shaft angle CT femoral anteversion
–
2
–
1/2
Concurrent validity, intra- and interrater reliability Intra- and interrater reliability
Trochanteric prominence angle test, maximal hip internal and external rotation
2
8/7y
1/2
such as the lateral margin of the acetabular roof38 or the midpoint of the ‘gothic arch’, which frequently occurs in the case of acetabular dysplasia;39 (2) careful positioning of the patient may also limit measurement errors and increase reliability.18,49 Radiographs should be carried out as far as possible with the pelvis flat, horizontal, and with neutral abduction/adduction of the legs.50,51
Acetabular dysplasia The metrological properties of the acetabular index calculated from radiographs and measurements of acetabular morphology from 2D or 3D images have been evaluated for the assessment of acetabular dysplasia.
ICC, Pearson rank correlation coefficient
Concurrent validity, intra- and interrater reliability
The acetabular index calculated from radiographs showed moderate concurrent validity with measurements taken from 3D images, good to excellent reliability and a threshold of true change of 2.6° when one measurer is involved and 5.9° when there are several measurers. As for the calculation of migration percentage, care must be taken to reduce measurement errors.52,53 Use of the lateral margin of the sourcil rather than the lateral margin of the acetabular roof has been recommended by Agus et al.,54 although this has not been evaluated in children with CP. Using the midpoint of the ‘gothic arch’ when it is present may increase reliability.39 Finally, extra care must also be taken for young children with small femoral heads as errors can be greater.39 Review
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Anteroposterior X-ray 3D CT Anteroposterior X-ray
Anteroposterior X-ray Anteroposterior X-ray
Gose et al.35
Lee et al.32
Anteroposterior X-ray
Segev et al.41
3D CT
Gose et al.34
Gose et al.35
3D CT, reformatted slices Anteroposterior X-ray 3D CT
Chung et al.29
Acetabular morphology Chung et al.31 3D CT
Anteroposterior X-ray
Pountney et al.40
Parrott et al.39
Kim et al.38
Anteroposterior X-ray
Anteroposterior X-ray two radiographs taken the same day
Faraj et al.37
Hip migration Cliffe et al.36
Radiological device
SD range=3.31–7.91% SD range=4.81–5.04°
–
Centre-edge angle
Lateral opening angle, sagittal inclination angle
3D visual assessment of acetabular dysplasia Three directional acetabular indexes Acetabular index
ICC=0.93 RMSE=1.51°
ICC range=0.88–0.98 mean diff=2.1–4.1° –
– Correlation between lateral opening angle and acetabular index: r=0.58 (p
