Mandible reconstruction with patient-specific pre-bent reconstruction plates: comparison of a transfer key method to the standard method--results of an in vitro study.

PURPOSE: Patient-specific mandible reconstruction plates may be pre-bent to facilitate the surgical procedure. A method using transfer keys (TK) for repositioning pre-bent plates was compared with the standard method on mandibular models to evaluate its feasibility.
METHOD: Ten mandible models were used to pre-bend reconstruction plates. After plate fixing on the models, TK were fabricated. Plates and TK were removed and segmental resections were performed. The plates were replaced on the models by the standard method of determining the plate position using previous screw holes. Plates were removed and then relocated by use of the TK. To compare the accuracy of both methods, the distances between four corresponding points of the condyles and the mandibular rami were measured.
RESULTS: The mean deviation of the absolute values from the initial values for the models between the condyles and the rami was 0.964 mm for the standard method and 0.821 mm for the TK method. To determine whether there was enlargement or shrinkage between the rami or the condyles, we analysed the relative values of the data. For the standard method, the mean deviation from the initial values was +0.178 mm; for the TK method, it was +0.080 mm. In both cases, the differences were not significant.
CONCLUSION: Pre-bent reconstruction plates using patient-specific 3D models can be useful in mandible reconstruction. The TK method was tested in vitro and shown to be as accurate as the standard method. The TK method may shorten the procedure and may be useful for secondary cases and cases where the pathology involves the outer corte of the mandible.