Developmental dysplasia of the hip: A computational biomechanical model of the path of least energy for closed reduction.

This study utilized a computational biomechanical model and applied the least energy path principle to investigate two pathways for closed reduction of high grade infantile hip dislocation. The principle of least energy when applied to moving the femoral head from an initial to a final position considers all possible paths that connect them and identifies the path of least resistance. Clinical reports of severe hip dysplasia have concluded that reduction of the femoral head into the acetabulum may occur by a direct pathway over the posterior rim of the acetabulum when using the Pavlik harness, or by an indirect pathway with reduction through the acetabular notch when using the modified Hoffman-Daimler method. This computational study also compared the energy requirements for both pathways. The anatomical and muscular aspects of the model were derived using a combination of MRI and OpenSim data. Results of this study indicate that the path of least energy closely approximates the indirect pathway of the modified Hoffman-Daimler method. The direct pathway over the posterior rim of the acetabulum required more energy for reduction. This biomechanical analysis confirms the clinical observations of the two pathways for closed reduction of severe hip dysplasia. The path of least energy closely approximated the modified Hoffman-Daimler method. Further study of the modified Hoffman-Daimler method for reduction of severe hip dysplasia may be warranted based on this computational biomechanical analysis. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1799-1805, 2017.

Review of MRI wrist examination since introduction of Medicare item number.

INTRODUCTION: The Australian Health Department provided extended rebatable requesting rights to general practitioners in 2012 for magnetic resonance imaging (MRI) examinations in patients less than 16 years of age for a small set of clinically appropriate indications. Included item numbers 63522 and 63523 'referral by a medical practitioner (excluding a specialist and consultant physician) for a scan of wrist following radiographic examination where scaphoid fracture is suspected'. The aim of this study is to evaluate MRI examinations of suspected scaphoid fractures in the paediatric population following the Medicare item number introduction. METHODS: Review of 60 consecutive MR wrist examinations requested by general practitioners and performed between 30 November 2012 and 16 July 2014 for a rebatable magnet in a private clinical setting. The indication for all studies was to exclude a clinically suspected fractured scaphoid following a normal radiograph. All patients were less than 16 years of age at time of examination. RESULTS: Sixty examinations were performed; 51 revealed pathology (85% of cases) with nine normal examinations (15%). Twenty-nine studies revealed one of more fractures involving the carpals, metacarpals or distal radius. In total, 41 fractures were identified on MRI examination with 29 carpal bone fractures, six distal radius fractures and six metacarpal fractures. CONCLUSIONS: The results highlight the sensitivity of MR wrist examination and its diagnostic benefit in clinically suspected paediatric scaphoid fractures. In addition, it reflects the prudent referral nature of general practitioners.

Case-control single-marker and haplotypic association analysis of pedigree data.

Related individuals collected for use in linkage studies may be used in case-control linkage disequilibrium analysis, provided one takes into account correlations between individuals due to identity-by-descent (IBD) sharing. We account for these correlations by calculating a weight for each individual. The weights are used in constructing a composite likelihood, which is maximized iteratively to form likelihood ratio tests for single-marker and haplotypic associations. The method scales well with increasing pedigree size and complexity, and is applicable to both autosomal and X chromosomes. We apply the approach to an analysis of association between type 2 diabetes and single-nucleotide polymorphism markers in the PPAR-gamma gene. Simulated data are used to check validity of the test and examine power. Analysis of related cases has better power than analysis of population-based cases because of the increased frequencies of disease-susceptibility alleles in pedigrees with multiple cases compared to the frequencies of these alleles in population-based cases. Also, utilizing all cases in a pedigree rather than just one per pedigree improves power by increasing the effective sample size. We demonstrate that our method has power at least as great as that of several competing methods, while offering advantages in the ability to handle missing data and perform haplotypic analysis.