LIVRE JDG 2014

P. Erasmus, K.J. Cho, J.H. Müller

Robotic bone

preparation

Two types of robots are available; haptic and

autonomous [2]. In haptic or tactile systems,

the surgeon drives the cutting tool but the robot

will prevent him to go off the pre-planned depth

and position of the bone cuts. In the autonomous

systems, the surgeon will do the approach, set

up the robot and then stand back allowing the

robot to do the bone cuts by itself.

With the haptic systems, a preoperative

planning is done on 3D reconstructions from

the CT and MRI. At the surgery, a surgeon

would use the computer to determine the leg

alignment and “morph” the joint surfaces in the

same way as the CAD surgery. In contrast to

CAD surgery, the bone cuts are now made

under robotic control according to the

preoperative planning (fig. 4).

However, even in these robotic systems a best

fit is usually a compromise between a good

prosthesis articular transition; and an acceptable

axial and sagittal rotation of the prosthesis.

Patient-specific

prosthesis

In a study where we virtually implanted 4

different commercially available prosthesis in a

normal asymptomatic patellofemoral joint, it

was evident that not one of these prosthesis

restored the joint to normal [3]. All four

prosthesis;

the

Avon

Patellofemoral

Arthroplasty (Stryker, Kalamazoo, Michigan,

USA); the Competitor PFJ Oxinium (Smith &

Nephew, Inc. Memphis, Tennessee, USA); the

Vanguard

PatellofemoralReplacement System

(Biomet UK L

, South Wales, UK); and the

Kneetec, (Tornier, Fr) increased the medial A-P

dimension, decreased the lateral A-P dimension

and decreased the depth of the trochlea (fig. 5).

Fig. 4: Morphing the distal femur and planning the prosthesis position with the aid of a computer for

implanting the prosthesis using a haptic robot (Navio PFSTM surgical system, Blue belt technologies, INC).

Fig. 5: Virtual implantation of 4 different commercial off the shelve prostheses implantation shows raised

medial A-P dimensions relative to lateral A-P dimensions and decreased trochlear depth.