Spanish to English Medical Medical (general) Surgery report, neurosurgery, craniectomy

Hi all,

I came across the phrase in a surgical report (informe quirúrgico). The procedure that was carried out was a craniectomy ("craniectomía descompresiva izquierda", to be exact) and the phrase appears in this context:

"Técnicas:
BAG. IOT (procedente de UCI). Profilaxis antibiótica con Cefazolina 2gr. IV. Decúbito supino con cabeza lateralizada hacia la derecha. Incisión en 'signo de interrogación' FTP izquierdo. Craniectomía FTP izquierda con 5 trépano de apoyo. Apertura dural en 'cruz'. Salida con mucha presión de material hemático, protrusión de parénquima cerebral sobre todo a nivel temporal izquierdo con importante áreas de contusión. "

My thoughts are that it may be a piece of drilling equipment, and perhaps the 5 is referring to the size of it? I would appreciate your suggestions.

The report was issued in Spain and the target audience is in the UK.

Thanks in advance!

Nisah