Comment on “Computer-assisted surgery for replacement of the temporomandibular joint with customized prostheses: can we validate the results?” (original) (raw)

Oral and Maxillofacial Surgery, 2021

Abstract

To the Editor We would like to comment on the interesting article entitled “Computer-assisted surgery for replacement of the temporomandibular joint with customized prostheses: can we validate the results?” by Boccalatte et al. [1]. Even if the authors are to be appreciated for their research on the field of computer-assisted surgery, we would like to bring some topics into debate. First of all, we are grateful for citing our previous paper on the same issue, but more attention should be paid to its contents. The authors cannot state that they did not find reports in the literature validating TMJ replacement accuracy with absolute numbers because our work provided an equally reliable method to quantitatively measure the entity of deviation between planned prostheses position and postoperative results providing an overall accuracy estimation [2]. In our opinion, a criticism can be addressed to the method implemented by the authors because they did not specify how they performed the fusion between the preoperative planning model and postoperative result. This plays a crucial role in determining the precision of measurement and this is especially true in those cases where occlusal changes are planned by repositioning the maxilla and the mandible. For this reason, in our work, we decided to separately align the skull base for the fossa component and the mandible for the ramus component. Neglecting this particular for cases in which the mandible position has changed will introduce a systematic bias on the linear measure of screws inserted for the condylar component. The second topic that we would like to emphasize is the use of intraoperative navigation whose implementation in craniomaxillofacial surgery should be encouraged but in TMJ replacement shows several limitations. This technique bears intrinsically an imprecision of about 1 mm furthermore magnified by the fact that the mandible is not a fixed bone. Even a minimal mistake during prostheses positioning might result in undesirable malocclusion. Therefore, we suggest the use of surgical cutting/ positioning guides to provide extreme precision when performing osteotomies and to facilitate the inset of the prostheses. Although the purpose of the article is to validate a system to measure accuracy, results achieved by the authors have to be taken into account, as they do not appear to be completely satisfactory. In fact, there is substantial difference between the virtual planning and the final outcome. Therefore, we can state that in the analyzed cases TMJ replacement was not accurate and the authors should enquiry the underlying reason. On the contrary, our group showed very good results in terms of accuracy of TMJ replacement [2]. Our belief is that accuracy is the result of a cascade of events planned and realized with maximum attention: (1) Ct scan with appropriate protocol for 3D reconstruction; (2) virtual planning; (3) design of cutting/positioning guides useful during surgery; (4) appropriate design of implants; (5) quality control of 3D printed manufacts; (6) precision surgery. In this regard, we have developed a cutting/positioning guide made of titanium to ensure a precise fitting with the underlying bone which allows for precise bone cutting and univocal prostheses insetting using predrilled holes and an * Massimo Robiony massimo.robiony@uniud.it

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