Clinical screening of developmental dysplasia of the hip in neonates by acoustical technique

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Clinical screening of developmental dysplasia of the hip in neonates by acoustical technique


Author: Huang, Xiaolin
Title: Clinical screening of developmental dysplasia of the hip in neonates by acoustical technique
Degree: Ph.D.
Year: 2001
Subject: Infants (Newborn) -- Abnormalities
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Rehabilitation Sciences
Pages: xvi, 233 leaves : ill. ; 30 cm
Language: English
InnoPac Record:
Abstract: Early screening of the developmental dysplasia of the hip in neonates still presents problem, especially in developing countries. This study attempts to develop an acoustical technique for the screening of DDH in neonates with the hope that early intervention would prevent disability resulting from this defect. This acoustical technique based on a system analysis approach was applied to examine the acoustic transmission in the hip joints. Special experimental instrumentation has been set up to measure the acoustic signals transmitted along a path from the driving point at the sacrum to the greater trochanters on both sides. A random vibratory force (pink noise) up to 800 Hz was applied to the sacrum in the antero-posterior direction at S2, while acoustic signals were picked up by a pair of adult-size stethoscope-microphone assembly held by a compressive force at the greater trochanters on both sides. A dual-channel signal analyser was employed for data acquisition. The acoustical technique was shown to be reliable and repeatable in quantifying the transmitted sound signals across both hips, and in performing a comparative measurement to identify asymmetry of the anatomical configuration of the hip joints. Two key parameters have been identified. The high coherence confirmed the validity of a model proposed for the sacrum-pelvis-hip complex. Discrepancy defined from a modified form of transfer function was found useful in the identification of structural asymmetry between both hips. The baselines for the groups of normal adults, pre-school children and neonates have been established. The most optimal and effective testing frequencies were found in the frequency bands of 200, 250 and 315 Hz, in which there was a high coherence (y2> 0.9) of signals and a small discrepancy (D < 3 dB) between both hips. The results obtained from 90 normal neonates showed a more reliable baseline in which there was the highest coherence (y2 > 0.94) and the smallest discrepancy (D < 2 dB) in the frequency range of interest, which can be used for clinical reference. Seventeen patients with unilateral DDH were examined by the acoustical technique. The results suggested that the coherence consistently below 0.8 in at least one of the frequency bands of 200, 250 and 315 Hz was definitely indicative of structural asymmetry between both hips. The discrepancy estimated for the patients were found to be clearly different from the normal figures. It was confirmed that any structural changes in joint congruity, concentricity and coverage of the femoral head would result in an asymmetrical acoustic transmission across the hip joints. Discriminative analysis has shown a significant difference between the groups of normal neonates and patients with unilateral DDH in the frequency bands of 200, 250 and 315 Hz. By setting the cut-off discrepancy at 2.0 dB, the best sensitivity of 100% and specificity of 75% would be achieved. Based on these figures and the baseline of the normal neonates, the acoustical technique could be used as a screening tool for DDH in neonates. The technique has served the purpose of a screening test for DDH in neonates by meeting the basic requirements of any screening tool. The objective measurement of discrepancy was also in good agreement with the clinical findings. The findings from this study suggest that the acoustical technique can be developed further to a non-provocative, objective and non invasive screening tool for early detection of DDH, or asymmetry in the bone and joint configuration. A screening protocol has been established for DDH. An integrated system has been proposed for dedicated use in routine screening of dysplastic hips in a wider-scale application.

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