The device comprises a clamp secured to a cutting guide (4) and comprising two arms (1) and (2) articulated against an elastic return means (3). According to the invention, the device comprises a bespoke volumetric body (5) acting as a spacer, being shaped such as to be coupled to one of the arms (2), one of the 10 faces of the body (5), considered to be opposite to the coupling with the arm (2) has a recessed indentation that is married, in inverted form, with the posterior articular face of the patella positioned on the other arm (1), said indentation and the height of the volumetric body (5) being defined by means of form modeling software using scanner or MRI data from said patella, in order to give the 15 orientation and positioning of the prosthetic patella, the posterior cutting height and the drilling depth of a retention pin for the patellar implant, the volumetric body (5) acting as a spacer being coaxially drilled with a through hole of a diameter that is substantially equal to that of the patellar implant retention pin.
