The variation in hip stability measurements between supine and standing radiographs of dysplastic hips

Pelvis radiographs in children with cerebral palsy: effects of patient positioning on calculating migration percentages

BACKGROUND

Hip displacement in children with cerebral palsy (CP) is monitored by measuring migration percentage on anteroposterior pelvis radiographs. However, proper positioning for radiography in children with spasticity is difficult. The reliability and accuracy of migration percentage as a function of patient positioning is unknown.

OBJECTIVE

To determine the effects of patient positioning on migration percentage measurements in children with CP.

MATERIALS AND METHODS

We identified children with CP (≤18-year-old) with pelvis CT and anteroposterior pelvis radiograph obtained <6 months apart (10/2018-11/2021). Digitally reconstructed radiographs were generated from each pelvis CT, to simulate nine different patient positions: neutral; 10° and 20° lordosis and kyphosis; and 10° and 20° right rotation and left rotation. Two radiologists measured migration percentages from the simulated and real pelvis radiographs. We used Spearman's rho to assess inter-rater reliability, and Wilcoxon signed rank test to determine statistical significance.

RESULTS

We studied sixty-three children (male=41; median age=8 years; range=4-18 years). The two radiologists' migration percentage measurements were highly correlated with each other across all simulated and real radiographs (Spearman's rho=0.86-0.99, P<0.01). For both readers and hips, migration percentages measured from real radiographs were significantly different from those measured from neutral simulated radiographs (P<0.01), with median absolute difference=5-6 percentage points (PP) and interquartile range (IQR)=9-12 PP. When comparing migration percentage measurements from neutral simulated radiographs to those in kyphosis/lordosis and right/left rotations, median absolute differences were 2-4 PP (IQR=3-8 PP) and 4-15 PP (IQR=6-17 PP), respectively.

CONCLUSION

Inter-rater reliability of measured migration percentages is high, but accuracy decreases with patient positional changes.

Anterior Center-Edge Angle Is Less Reliable Than Anterior Wall Index to Predict Anterior Coverage of the Femoral Head

BACKGROUND

No consensus is available regarding which radiographic measurement most accurately correlates with anterior coverage of the femoral head.

PURPOSE

(1) To determine the correlation between 2 measurements of anterior wall coverage: total anterior coverage (TAC) calculated from radiographs and equatorial anterior acetabular sector angle (eAASA) calculated from computed tomography (CT) scans; (2) to define the correlation between anterior center-edge angle (ACEA) and anterior wall index (AWI) with TAC and eAASA; and (3) to investigate what other radiographic metrics may help predict anterior coverage.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 3.

METHODS

The authors retrospectively reviewed 77 hips (48 patients) for which radiographs and CT scans were obtained for reasons other than hip-related pain. Mean age of the population was 62 ± 22 years; 48 (62%) hips were from female patients. Two observers measured lateral center-edge angle (LCEA), AWI, Tönnis angle, ACEA, CT-based pelvic tilt, and CT-based acetabular version, with all Bland-Altman plots within 95% agreement. Correlation between intermethod measurements was estimated with a Pearson coefficient. Linear regression was used to test the ability of baseline radiographic measurements to predict both TAC and eAASA.

RESULTS

Pearson coefficients were r = 0.164 (ACEA vs TAC; P = .155), r = 0.170 (ACEA vs eAASA; P = .140), r = 0.58 (AWI vs TAC; P = .0001), and r = 0.693 (AWI vs eAASA; P < .0001). Multiple linear regression model 1 showed that AWI (β = 17.8; 95% CI, 5.7 to 29.9; P = .004), CT acetabular version (β = -0.45; 95% CI, -0.71 to -0.22; P = .001), and LCEA (β = 0.33; 95% CI, 0.19 to 0.47; P = .001) were useful to predict TAC. Multiple linear regression model 2 revealed that AWI (β = 25; 95% CI, 15.67 to 34.4; P = .001), CT acetabular version (β = -0.48; 95% CI, -0.67 to -0.29; P = .001), CT pelvic tilt (β = 0.26; 95% CI, 0.12 to 0.4; P = .001), and LCEA (β = 0.21; 95% CI, 0.1 to 0.3; P = .001) accurately predicted eAASA. Model-based estimates and 95% CIs using 2000 bootstrap samples from the original data were 6.16 to 28.6 for AWI in model 1 and 15.1 to 34.26 for AWI in model 2.

CONCLUSION

There was a moderate to strong correlation between AWI and both TAC and eAASA, whereas ACEA correlated weakly with the former measurements, thus not being useful to quantify anterior acetabular coverage. Other variables such as LCEA, acetabular version, and pelvic tilt may also help predict anterior coverage in asymptomatic hips.

Universal screening may reduce the incidence of late diagnosis of developmental dysplasia of the hip : a systematic review and meta-analysis

AIMS

We investigated the prevalence of late developmental dysplasia of the hip (DDH), abduction bracing treatment, and surgical procedures performed following the implementation of universal ultrasound screening versus selective ultrasound screening programmes.

METHODS

A systematic search of PubMed, Embase, The Cochrane Library, OrthoSearch, and Web of Science from the date of inception of each database until 27 March 2022 was performed. The primary outcome of interest was the prevalence of late detection of DDH, diagnosed after three months. Secondary outcomes of interest were the prevalence of abduction bracing treatment and surgical procedures performed in childhood for dysplasia. Only studies describing the primary outcome of interest were included.

RESULTS

A total of 31 studies were identified, of which 13 described universal screening and 20 described selective screening. Two studies described both. The prevalence of late DDH was 0.10 per 1,000 live births (95% confidence interval (CI) 0.00 to 0.39) in the universal screening group and 0.45 per 1,000 live births (95% CI 0.31 to 0.61) in the selective screening group. Abduction bracing treatment was performed on 55.54 per 1,000 live births (95% CI 24.46 to 98.15) in the universal screening group versus 0.48 per 1,000 live births (95% CI 0.07 to 1.13) in the selective screening group. Both the universal and selective screening groups had a similar prevalence of surgical procedures in childhood for dysplasia being performed (0.48 (95% CI 0.32 to 0.63) vs 0.49 (95% CI 0.31 to 0.71) per 1,000 live births, respectively).

CONCLUSION

Universal screening showed a trend towards lower prevalence of late DDH compared to selective screening. However, it was also associated with a significant increase in the prevalence of abduction bracing without a significant reduction in the prevalence of surgical procedures in childhood for dysplasia being performed. High-quality studies comparing both treatment methods are required, in addition to studies into the natural history of missed DDH.Cite this article: Bone Joint J 2023;105-B(2):198-208.

Imaging in Hip Arthroplasty Management-Part 1: Templating: Past, Present and Future

Hip arthroplasty is a frequently used procedure with high success rates. Its main indications are primary or secondary advanced osteoarthritis, due to acute fracture, osteonecrosis of the femoral head, and hip dysplasia. The goals of HA are to reduce pain and restore normal hip biomechanics, allowing a return to the patient’s normal activities. To reach those goals, the size of implants must suit, and their positioning must meet, quality criteria, which can be determined by preoperative imaging. Moreover, mechanical complications can be influenced by implant size and position, and could be avoided by precise preoperative templating. Templating used to rely on standard radiographs, but recently the use of EOS^® imaging and CT has been growing, given the 3D approach provided by these methods. However, there is no consensus on the optimal imaging work-up, which may have an impact on the outcomes of the procedure. This article reviews the current principles of templating, the various imaging techniques used for it, as well as their advantages and drawbacks, and their expected results.

Pelvic tilt from supine to standing in patients with symptomatic acetabular retroversion of the hip

AIMS

Acetabular retroversion is a recognized cause of hip impingement and can be influenced by pelvic tilt (PT), which changes in different functional positions. Positional changes in PT have not previously been studied in patients with acetabular retroversion.

METHODS

Supine and standing anteroposterior (AP) pelvic radiographs were retrospectively analyzed in 69 patients treated for symptomatic acetabular retroversion. Measurements were made for acetabular index (AI), lateral centre-edge angle (LCEA), crossover index, ischial spine sign, and posterior wall sign. The change in the angle of PT was measured both by the sacro-femoral-pubic (SFP) angle and the pubic symphysis to sacroiliac (PS-SI) index.

RESULTS

In the supine position, the mean PT (by SFP) was 1.05° (SD 3.77°), which changed on standing to a PT of 8.64° (SD 5.34°). A significant increase in posterior PT from supine to standing of 7.59° (SD 4.5°; SFP angle) and 5.89° (SD 3.33°; PS-SI index) was calculated (p < 0.001). There was a good correlation in PT change between measurements using SFP angle and PS-SI index (0.901 in the preoperative group and 0.815 in the postoperative group). Signs of retroversion were significantly reduced in standing radiographs compared to supine: crossover index (0.16 (SD 0.16) vs 0.38 (SD 0.15); p < 0.001), crossover sign (19/28 hips vs 28/28 hips; p < 0.001), ischial spine sign (10/28 hips vs 26/28 hips; p < 0.001), and posterior wall sign (12/28 hips vs 24/28 hips; p < 0.001).

CONCLUSION

Posterior PT increased from supine to standing in patients with symptomatic acetabular retroversion. The features of acetabular retroversion were less evident on standing radiographs. The low PT angle in the supine position is a factor in the increased appearance of acetabular retroversion. Patients presenting with symptoms of hip impingement should be assessed by supine and standing pelvic radiographs to highlight signs of acetabular retroversion, and to assist with optimizing acetabular correction at the time of surgery. Cite this article: Bone Joint J 2022;104-B(7):786-791.