[1] Curtin Univ, Curtin Sch Allied Hlth, Perth, WA 6845, Australia
[2] Univ Auckland, Dept Surg, Auckland 1023, New Zealand
[3] Starship Child Hlth, New Zealand Cerebral Palsy Register, Auckland 1023, New Zealand
[4] Cerebral Palsy Soc New Zealand, Auckland 1023, New Zealand
[5] Auckland Dist Hlth Board, Newborn Serv, Starship Child Hlth, Auckland 1023, New Zealand
[6] Auckland Dist Hlth Board, Dept Paediat Orthopaed, Starship Child Hlth, Auckland 1023, New Zealand