[1] Univ New South Wales, Fac Med, Sydney, NSW, Australia
[2] Prince Wales Private Hosp, NeuroSpine Surg Res Grp NSURG, Sydney, NSW, Australia
[3] Prince Wales Hosp, Dept Neurosurg, Randwick, NSW, Australia
[4] Univ Sydney, Fac Med, Sydney Med Sch, Sydney, NSW, Australia