Pubo-Femoral Distances Measured Reliably by Midwives in Hip Dysplasia Ultrasound

The pubo-femoral distance (PFD) has been suggested as an ultrasound screening tool for developmental dysplasia of the hip (DDH). The aim of this study was to examine if midwives undergoing minimal training could reliably perform pediatric hip ultrasound and PFD measurements. Eight recruited midwives performed two rounds of independent blinded PFD measurements on 15 static ultrasound images and participated in four supervised live-scanning sessions. The midwives were compared to a group of three experienced musculoskeletal radiologists. Reliability was evaluated using inter-rater correlation coefficients (ICC). Linear regression was used to quantify the learning curve of the midwives as a group. There was near complete intra- and inter-rater agreement (ICC > 0.89) on static ultrasound images across both rounds of rating for midwives and radiologists. The midwives performed a mean of 29 live hip scans (range 24–35). The mean difference between midwives and supervising radiologists was 0.36 mm, 95% CI (0.12–0.61) for the first session, which decreased to 0.20 mm, 95% CI (0.04–0.37) in the fourth session. ICC for PFD measurements increased from 0.59 mm, 95% CI (0.37–0.75) to 0.78 mm, 95% CI (0.66–0.86) with progression in sessions. We conclude that midwives reliably perform PFD measurements of pediatric hips with minimal training

Birthweight correlates to pubo-femoral distances and α angles in hip ultrasound of newborns at 6 weeks of age: a retrospective cohort study

Background and purpose: There is inconsistency in the literature regarding the relationship between increased birthweight and risk of developmental dysplasia of the hip (DDH). We aimed to investigate the correlation between birthweight and pubo-femoral distance (PFD), as well as Graf's α angle in newborns undergoing hip ultrasound examination at 6 weeks of age.Patients and methods: Basic newborn characteristics and ultrasound measurements were retrospectively collected during a 1-year study period. We excluded multiple births, newborns born at less than 37 gestational weeks, and incomplete information. Simple and multiple linear regression analyses were performed to evaluate the correlation of birthweight and PFD, and, second, birthweight and α angles including a stratified regression analysis investigating the potential effect modification of sex.Results: 707 newborns (1,414 hips) were included. Mean birthweight was significantly higher for male newborns (P < 0.001). Increased birthweight was positively correlated to PFD values (crude coefficient 0.21, 95% confidence interval [CI] 0.10-0.32) and the correlation was still present after adjusting for sex, family history, and breech presentation (adjusted coefficient 0.18, CI 0.07-0.29). The stratified α angle model for the males was significant for both the crude coefficient (-0.73, CI -1.28 to -0.19) and the adjusted (-0.59, CI -1.15 to -0.03), and also for the females (crude coefficient -1.14, CI -1.98 to -0.31 and adjusted coefficient -1.15, CI -1.99 to -0.31).Conclusion: We found that increased birthweight positively correlated to PFD, and negatively correlated to α angle, but this was not of clinical significance

What is the association between MRI and conventional radiography in measuring femoral head migration?

Background and purpose — Pelvic radiographs are traditionally used for assessing femoral head migration in residual acetabular dysplasia (RAD). Knowledge of the heightened importance of cartilaginous structures in this condition has led to increased use of MRI in assessing both osseous and cartilaginous structures of the pediatric hip. Therefore, we assessed the relationship between migration percentages (MP) found on MRI and conventional radiographs. Second, we analyzed the reliability of MP in MRI and radiographs. Patients and methods — We retrospectively identified 16 patients (mean age 5 years [2–8], 14 girls), examined for RAD during a period of 2½ years. 4 raters performed blinded repeated measurements of osseous migration percentage (MP) and cartilaginous migration percentage (CMP) in MRI and radiographs. Pelvic rotation and tilt indices were measured in radiographs. Bland–Altman (B–A) plots and intraclass correlation coefficients (ICC) were calculated for agreement and reliability. Results — B–A plots for MPR and MPMRI produced a mean difference of 6.4 with limits of agreement –11 to 24, with higher disagreements at low average MP values. Mean MPR differed from mean MPMRI (17% versus 23%, p < 0.001). MPR had the best interrater reliability with an ICC of 0.92 (0.86–0.96), compared with MPMRI and CMP with ICC values of 0.61 (0.45–0.70) and 0.52 (0.26–0.69), respectively. Intrarater reliability for MPR, MPMRI and CMP all had ICC values above 0.75 and did not differ statistically significantly. Differences inMPMRI and MPR showed no correlation to pelvic rotation index, pelvic tilt index, or interval between radiograph and MRI exams. Interpretation — Pelvic radiographs underestimated MP when compared with pelvic MRI. We propose CMP as a new imaging measurement, and conclude that it has good intrarater reliability but moderate interrater reliability. Measurement of MP in radiographs and MRI had mediocre to excellent reliability