Proposal of an innovative technique for mandibular reconstruction: preliminary study.

Author: P. Di Emidio

Affiliation: Department of Neurosurgery and Maxillofacial Surgery, “G. Mazzini” Hospital, Teramo, Italy

Mailing address:

Dr P. Di Emidio,

Department of Neurosurgery and Maxillofacial Surgery,

“G. Mazzini” Hospital, Teramo, Italy

e-mail: paolodiemidio@gmail.com

Introduction

The reconstruction of large mandibular defects, especially if secondary to demolition for oncological processes, represents the main target in maxillo-facial reconstructive surgery. The need for a considerable quantity and quality of osteoplastic material to be grafted, the particular shape and the correct alignment with the upper jaw, impose a wide variability in the application of a precise surgical technique that restores morphology, function and, as much as possible, the facial aesthetics. The first attempts at mandibular reconstruction date back more than forty years when non-revascularized autologous bone was used for the reconstruction of maxillofacial and mandibular defects. The technical and scientific knowledge of the time, as well as some pathological conditions that compromised the periosteum, vascularization, infection complications and the consequence of extensive fibrosis caused by the same operation all precluded the post-oncological or post-traumatic reconstruction of the mandible (1-2). Mandibular reconstruction with non-microsurgical tissues is used in preprosthetic, post-traumatic surgery and subsequently to minimal mandibular resections for benign tumors. Unfortunately, after resection of the lesion (with intra and exra-oral approach), at least 6 to 8 weeks are required before implantation to allow the soft tissues to recreate the appropriate vascularization to allow the survival of the bone fragment. However, these procedures are not free from severe complications (2-4). In the past, in oncological surgery the tendency was to stabilize the residual bone stumps with metal reconstruction plates  and to delay the intervention to a later date. Only after the patient was judged free of disease did the mandibular reconstruction proceed.

Currently, many operators prefer, when conditions permit, to carry out the demolition of the area affected by neoplasia and to reconstruct the surgical defect in a single operating time. Other authors have used alloplastic materials as a means of reconstruction of the surgical minus. Chanchareonsook et al. used in Macaca fascicularis a bone reconstruction technique that involves the use of a PLC scaffold (ε-caprolactone) coated with calcium phosphate (5). However, this technique would not seem to be free from biomechanical problems (6-7).

Proposed innovative surgical technique: rationale of the study

The  proposed method involves the use of a special reconstructive plate, formed by spheres and cylinders, contained in a PLC scaffold (5). (Patent US20020193796 – Anti-trauma surgical plate used to fix …). The plaque is packaged in cad-cam after surgical demolition planning (Fig. 1a-1b).

The novelty of the method lies in the structure of the modified dental implants placed on the spherical part of the osteosynthesis plate (Fig. 2a). Once the implants are screwed to the plate, they are put in contact with the spherical part of the plate itself, also micro-perforated with a laser technique (holes of 0.2 mm) over its entire surface. A kind of continuous dynamic is therefore created between the inner part of the dental implants and the surface of the plate (spherical part) (Fig. 2b).  In this way, a route of administration is created which runs through the internal part of the dental implant and crosses the spherical part of the osteosynthesis plate (Fig. 2a-2b). This allows the contact of therapeutic substances (e.g. recombinant P.M.R morphogenetic proteins, etc.) (8) with the deep part of the bone graft (9).

The rationale of the study is to allow the operator to have the pre-formed surgical plate, the scaffold (Fig. 3) the titanium plate and the fixtures (Fig. 4) on the day of surgery (10). This method also refers to reconstructive needs in patients suffering from expansive bone formation (11).

Conlusions

The reconstruction of bone segments has always been considered the primary target of all the different methods (12). To date, the means to achieve this goal have been the use of autologous and/or heterologous grafts that include the collection of bone fragments, vascularized and otherwise, to be implanted at the site of injury. The limitation of the use of these materials arises from the need to adapt bone fragments from osteocartilaginous structures different from those of the destination site. The success of these interventions depends on the ability of the graft to integrate with the receiving structures and on the size of the defect to be filled, hence, the need to use ad hoc systems that adapt to the shape of the receiving site and which are of sufficient dimensions to ensure adequate structural stability.

This technique represents an improvement over the previous models reported in the international literature to date. The proposed innovation would allow a reduction in the number of surgical operations with less stress for the patient and for the tissues of the oral cavity. All this would be reflected in an early rehabilitation of the masticatory apparatus, with an improvement in the patient’s quality of life.

Fig. 1a. Study model.  Detail of surgical plate with threaded spherical insert and modified dental implants. Surgical plate shaped in the laboratory.

 Fig. 1b. Study model – Surgical plate obtained by scanning.

a                                                                                             b
Fig. 2. a, b) Once the implants are screwed to the plate, they are put in contact with the spherical part of the plate itself, also micro-perforated with a laser technique. Thus, a kind of continuous dynamic is therefore created is created between the internal part of the dental implant, the surface of the plate (spherical part) and the scaffold.

Fig. 3. Scaffolds in poly-e-caprolactone (PCL) and hydroxyapatite with 75% porosity. Microfori with a diameter of 1200 micrometers interconnected.

Fig. 4. Study model. Final fixation of the surgical plaque-scaffold system on the mandible (surgical phase).

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