Mandibular reconstruction, proposal of an innovative technique: preliminary study.

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P. Di Emidio1

1Neurochirurgia e Chirurgia Maxillo Facciale Ospedale “G. Mazzini” Teramo, Italy

 

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 ago when the non-revascularized autologous bone was used for the reconstruction of maxillofacial and mandibular defects. The set of technical and scientific knowledge of the time, some pathological conditions that compromised the periosteum, vascularization, infectious complications and the consequence of extensive fibrosis caused by the same operation precluded the post-oncological or post-traumatic reconstruction of the mandible1-2. Mandibular reconstruction with non-microsurgical tissues is used by 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 before implantation are required to allow the soft tissues to recreate the right vascularization that allows the survival of the bone fragment. However, these procedures are not free from severe complications2-3-4. In the past in the oncological surgery the tendency was to stabilize the residual bone stumps with metal reconstruction plates 4 and to delay the intervention at a second timing. 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 the reconstruction of the surgical defect in a single surgical time. In this study, we used alloplastic materials as a means of reconstruction of the surgical minus. N. Chanchareonsook et al. used in Macaca fascicularis a bone reconstruction technique that involves the use of a PLC scaffold (e-caprolactone) and coated with calcium phosphate (5). However, this last technique would not seem to be free from biomechanical problems.

 

Proposed innovative surgical technique: rational of the study

            The 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). The plaque is packaged in cad-cam after surgical demolition planning.

              The vitality of the method lies in the structure of the modified dental implants placed on the spherical part of the osteosynthesis plate (fig. 1). 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 sort of continuous solution is thus created between the inner part of some dental implants and the surface of the plate (spherical part) (Fig. 2a, 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 (eg recombinant P.M.R morphogenetic proteins, etc. ..) with the deep part of the bone graft.

            The rationale of the study is to allow the operator to have the already shaped surgical plate, the scaffold (3) the titanium plate and the fixtures (fig. 3) on the day of surgery. This method is also to refer to reconstructive needs in patients suffering from expansive bone formation.

 

DISCUSSION

 

            The reconstruction of bone segments has always been considered the primary target of all the methods. The means to achieve this goal has been to date 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 due to the use of these materials arises from the need to adapt bone fragments from osteocartilaginous structures different from those from 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 have sufficient dimensions to ensure adequate structural stability. This technique represents an improvement over the previous models reported in the international literature to date.

            The innovation introduced 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 standard of living.

 

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

 

 


Fig. 2a                                                                                   Fig. 2b

Fig. 2a, 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 sort of continuous solution is created between the internal part of the dental implant, the surface of the plate (spherical part) and the scaffold.

 

Fig. 3. Study model – Final fixation of the surgical plaque-scaffold system on the mandible (surgical phase).

 

REFERENCES

 

  1. Boyne PJ. Restoration of osseous defects in maxillofacial casualties. J Am Dent Assoc. 1969 Apr;78(4):767-76.
  2. Obwegeser HL. Primary repair of the mandible by the intraoral route after partial resection in cases with and without preoperative infection. Br J Plast Surg. 1968 Jul;21(3):282-9.
  3. Tidstrom KD, Keller EE: Reconstruction of mandibular discontinuity with autogenous iliac bone graft. J Oral Maxillofac Surg. 1990 Apr;48(4):336-46.
  4. Ardary WC. Reconstruction of mandibular discontinuity defects using autogenous grafting and a mandibular reconstruction plate. J Oral Maxillofac Surg. 1993 Feb;51(2):125-30.
  5. Chanchareonsook N, Tideman H, Feinberg SE, et al. Segmental mandibular bone reconstruction with a carbonate-substituted hydroxyapatite-coated modular endoprosthetic poly (ℰ-caprolactone) scaffold in Macaca fascicularis. J Biomed Mater Res B Appl Biomater. 2014 Jul;102(5):962-76.
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