English to Italian Medical Medical: Instruments

There are many features of a stem design that influence ROM, including the shape and diameter of the neck, neck/head ratio, the position of the rotation center ***relative to the opening plane of the cup***, and the specific design of the opening plane itself.

Si parla di uno stelo femorale e delle caratteristiche che influenzano l'ampiezza del movimento. Mi sfugge come questo opening plane of the cup.

Grazie
Chiara