A novel method of assessing shoulder and elbow movement in children with obstetric brachial plexus palsy

Investigators: Dr Andrea Bialocerkowski, Prof Mary Galea, Mr Tim Wrigley

Obstetric brachial plexus palsy (OBPP) is a frequently occurring complication of childbirth, having a prevalence rate comparable to that of Down's Syndrome and Cerebral Palsy. Traction or compression of the brachial plexus is considered the primary mechanisms of injury   and this may occur whilst the fetus is in utero , during its descent through the birth canal or during delivery. This results in a spectrum of injuries that vary in severity (from neuropraxia to nerve root avulsion) and extent of damage (from one nerve root to all roots of the brachial plexus). Thus the physical signs of OBPP range from temporary upper limb dysfunction to a lifelong impairment and deformity in one arm.

Outcome measurement is integral in the management of a child with OBPP. The aim of measurement is to document the magnitude of function of the affected upper limb joints and frequently this is assessed as joint range of movement against gravity. Longitudinal measurements, which determine the presence and degree of recovery over time, are subsequently used to select the most appropriate management strategy for each child. However, many types of outcome measures exist for children with OBPP and there is no consensus regarding a gold standard measurement tool. This makes it difficult to compare the results obtained in different pediatric centres and in studies of intervention. Moreover, many of the tools used in clinical practice rely on visual observation, which is known to be less accurate than direct measurement.

In this study we used the v-scope to quantify shoulder and elbow movements in young children with OBPP. The v-scope system consists of three transmitting towers (180 x 80 x 40 mm), which beam infrared signals to small buttons (25 x 25 x 15mm). The buttons receive these signals, transduce them and emit ultrasonic pulses back to the towers. Each tower measures the lag time between the infrared pulse transmission and ultrasonic signal recognition, which is used, in conjunction with the temperature-corrected velocity of the sonic pulse, to provide a measure of the distance of each button from the tower. This measurement is accurate to 0.1mm. The towers are linked to a computer which allows storage and manipulation of data.

We showed that the v-scope is feasible to use in the clinical setting to assess the maximum range of elbow flexion and extension, shoulder abduction and flexion in young children with OBPP.

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