Mr Cullen has a pure sub-specialist interest in Foot and Ankle surgery.
He is widely published in peer review journals Orthopaedic textbooks. He lectures at meetings and conferences nationally and internationally and has an ongoing interest in research within his department.
Mr Cullen is a member of learned Foot and Ankles Societies (BOFAS, EFAS). He is very involved in teaching and lectures to students and orthopaedic and higher surgical trainees on Orthopaedic rotations nationally.
He is the co-convener of the Stanmore Foot and Ankle course, an internationally renowned advanced surgical course based at the RNOH.
Mr Cullen has developed a keen interest in sports and dance foot and ankle injuries, having been a keen sportsman himself, he spent time in the medical team for Premiership rugby, he now enjoys treating all manner of sports from beginners to elite athletes. He is the Foot and Ankle surgeon at the National Institute of dance medicine and science (NIDMS) based at the RNOH.
He works closely with the physiotherapy department, podiatrists and orthotists to provide a comprehensive service of care tailored to each patients needs.
Mr Cullen was appointed as a consultant at the RNOH in 2005.