University of Auckland PhD student Tom Lintern has built anatomical computer models of a baby’s head that can simulate the different motions generated from shaking associated with child abuse.
Mr Lintern (Ngāi Tahu) built the computer models to provide an objective way to estimate the motions that a baby experienced for a certain pattern of injury. His research is funded by an HRC Māori PhD Scholarship, and supervised by Professors Poul Nielsen and Martyn Nash, and Associate Professor Andrew Taberner at the university’s Auckland Bioengineering Institute (ABI).
The violent shaking of infants is the single most preventable cause of serious head injuries in babies under one year of age in New Zealand. Mr Lintern says the debate over the causes of brain damage during shaking has made it difficult for paediatricians to assess whether or not an infant’s injuries were the result of child abuse.
“In the literature, there’s controversy over the mechanisms of injury in shaken baby syndrome. A baby can present with bleeding on the brain or neurological issues, but what the paediatrician needs to decide is whether this was caused by an abusive incident or an accident,” says Mr Lintern.
“Much of the paediatricians’ analysis is subjective, relying on their experience. When they talk to parents and the injured child’s history doesn’t quite add up to what they’re seeing in the clinic, that’s a big red flag for them. With this computer model, I’m trying to add an objective measure to that.”
Mr Lintern began his research into the causal relationship between shaking of the torso and head motion by reproducing results from a pre-existing animal model. This animal model was developed by New Zealand’s leading expert on shaken baby syndrome, Dr Patrick Kelly from Starship Children’s Hospital, and Dr Frank Bloomfield from the Liggins Institute and Starship, both of whom provided valuable clinical support during Mr Lintern’s research.
Mr Lintern used a variety of instrumentation, including wireless inertial measurement sensors, developed by ABI researcher Mark Finch, to measure linear and angular accelerations and rotations of the head and torso.
These measurements were incorporated into computer models using OpenSim software, a musculoskeletal package developed at Stanford University to analyse how the skeleton moves in response to different stimuli. Mr Lintern also built an experimental dummy, replicating an infant’s geometry and other properties, as another form of model validation.
“Looking at the biomechanics of head motion during different types of shakes, I can see the importance of contact between the head and the torso. Although some people may think that shaken baby syndrome implies a non-impact motion, it’s quite clear that impact occurs between the head and other parts of the body.”
Mr Lintern says this impact produces big accelerations as the head goes fast and then stops at the torso, enough to possibly produce a similar response to if a head was hit against a hard surface such as a table.
“It might not be as big an acceleration, but it’s definitely much larger than what just the shaking motion alone would produce. That means there is a whole lot more to consider when building and analysing the models.”
To link this experimental work back to the human infant, Mr Lintern used CT and MRI images from infants to build anatomical models of babies’ heads that can move around. Another ABI PhD student will use these data to predict how the baby’s brain is affected for a given head motion and then relate that to injury.
Mr Lintern, who has presented his research at a number of international conferences, is currently writing up his thesis and plans to publish the results early next year.