TISSUE PREFABRICATION OF COMBINED SCAPULA FLAPS FOR MICROSURGICAL RECONSTRUCTION IN ORO-MAXILLOFACIAL DEFECTS

A NEW METHOD

Vinzenz K, Holle J, Würinger E, Kulenkampff KJ

SUMMARY

Nowadays, in congenital or aquired large oro-maxillo-facial defects microsurgical reconstruction is mainly performed by revascularized osseous, osteocutaneous, or osteomyocutaneous distant flaps.

The aims of reconstruction include not only restoration of stable continuity and esthetic contour, but also the restoration of a functioning "chewing organ". Beside the bulkyness of flaps, the stepwise surgical procedure (microvascular reconstruction, osseointegration of implants, secondary correction of flaps including preprosthetic surgery, etc.) is preventing physiological oral function for a long time, and gives some implications for creating an alterative method of microsurgical reconstruction with new designed flaps.

For reconstruction in maxillary and midface defects we preferably use the scapula flap.

Since modern diagnostic methods allow a comprehensive planning defining all relevant anatomical and functional factors in advance, now the "at one time " microvascular reconstruction by prefabricated scapula flaps becomes possible and offers some advantages:

The tissue prefabrication results in osseointegrated implants and and thin mucosal linings with stable periimplantory soft tissue conditiones at time of microsurgical reconstruction.

Postoperatively after immediate dental restoration full oral function is given.

The "at one time" reconstruction improves the psychosocial situation of the patient considerably.

INTRODUCTION

In large oro-maxillo-facial defects microsurgical reconstruction is performed by revascularized osseous, osteomyocutaneous or osteocutaneous distant flaps, resp., from various donor regions (Reuther, 1980; Taylor, 1982; Swartz, et al. 1986; Riediger, 1988; Manktelow, 1990; Reuther, 1992.). Subsequent to an established continuity of the skeleton, further surgical intervention is planned step by step and carried out in order to provide a functioning "chewing organ". This is, first, done by scondary correction of the transplanted flaps, including preprosthetic surgery (Hoffmeister and Ewers, 1986; Betz, et al., 1992), implant surgery (Neukam, 1989; Haßfeld, et al., 1992; Ericsson and Branemark, 1994;), and subsequent the establishment of stable periimplantory soft tissue conditiones .(Betz, et al. ,1992; Reuther, 1992)

In contrast to the above described stepwise surgical procedure modern diagnostic measurements allow in advance the exact definition of all requirements before starting surgery.

New imaging methods such as 3D-visualisation and interactive manipulation of CT data as well as operation planning using stereolithographic organ models (Andersson, 1988; Kärcher,1991; Elliot, et al., 1991; Ono, 1992; Stoker, 1992; Solar, et al.,1992; Altobelli, et al.1993.) are used for.

In contrast to reconstructions of the mandible and the mouth floor region (Daniel, 1978; Flemming, et al.1990; Reuther, 1992) the reconstruction of the maxilla and/ or midface represents one of the most crucial challenges (Ericsson and Branemark, 1994.)

The anatomy of this region is characterized by subtle bony and dental structures surrounding pneumatized cavities (e.g..paranasal sinuses). Particularly the reconstruction of the alveolar ridge with its tense oral and nasal mucosal linings has certain demands to the selected donor site. Various donor regions are mentioned in literature (Swartz, et al.1986; Boyd, et al.,1990; Flemming, et.al., 1990; Hidalgo, 1991.)

For reconstruction of the maxilla we use preferably the scapula flap.

Osteomyocutaneous flaps in the midface region are always too bulky preventing oral function, and, additionally, this bulkiness comes second among the causes for loss of the flap. Furthermore they are too heavy and also functional unphysiological for filling pneumatised cavities. Moreover, during operation the difficulties caused by the lack of space are increased by the relatively large size of the flaps, by the at the same time performed osteosynthesis for flap fixation and by microsurgery in an extremely limited area.

For these reasons, the aim has to be the use of an as subtle as possible combined flap with a subtle soft tissue coverage and to fix it in the least space-consuming way. The availability of tense oral and nasal mucosal linings as well as osseointegrated implants at time of maxillary reconstruction require necessarily a flap prefabrication at the donor site, since both the setting of mesh grafts and the stable osseointegration of the implants take some time.

Implants can be used for flap fixation minimizing the use of titanium miniplates.

In order to achieve a higher standard of reconstruction too, an improvement of the flap design during prefabrication is necessary.

MATERIAL AND METHOD

Clinical cases

Case 1

A 58 years old female patient was left with a hemimaxillectomy following resection of a protruding meningeoma of the skull 13 years ago.

Case 2

27 years old male patient with loss of the right maxilla, the right zygoma including the orbital floor, the eye, the cheek and the right side of the nose, following radiotherapy of a maxillary tumor 5 years before.

Diagnostic methods

Preoperative diagnosis and visualisation with three-dimensional reconstruction by an high speed image operation system with complete interactive 2D and 3D possibilities of visualisation and manipulation (ARRI Voxel Flinger) of CT data (HIQ Siemens thickness of slices 1-2 mm, reconstructed in high resolution mode). The system provides - after saving the sections from the CT or MR device - manifold interactive image manipulations via graphic work station and appropriate software. With this system the bony defect in the face and the appropriate place of the lateral border of the scapula can be correlated. In complex clinical cases stereolithographic models (Laserform) of both the maxilla and the scapula were performed for preoperative planning. Both, Kärcher (1992) and Lambrecht (1995) have described the transfer from three dimensional model to clinical surgery, using milled Styrodur models (Endoplan). In the same way we also adjuste individual (stereolithographic) organ models in combination with SAM apparatus by using the face bow. The plaster and/ or acrylic models of teeth and maxillary alveolar process were used to obtain precise occlusal information and for preliminary calculation of the transplants position. In our procedure the stepwise operation planning is then continued by positioning the stereolithographic model of the scapula flaps after tissue prefabrication into the skull model, which is especially important in reconstruction by combined flaps as shown in case two.

Cephalometric measurements are used and relevant gnathological parameters were transferred into 3D-CT visualisation (ARRI Voxel Flinger) via graphic work station. The preoperative calculated inclination of the implants during prefabrication can be transferred to the scapula using anatomical landmarks and is exactly controlled postoperatively after flap prefabrication by use of stereolithographic models of the thus anatomically shaped scapula flap and before maxillary reconstruction.

Surgical concept

In all cases the surgical procedure was performed in two stages. First, the tissue prefabrication of the scapula flap was done at the donor site. The microvascular reconstruction in the maxillofacial area was performed about 3 months later.

Flap prefabrication (Fig.1)

According to the preoperative analysis the appropriate part of the lateral border of the scapula was selected, the vascular bundle to the scapula in a distance of 2-3 cm dissected and the implants placed into position according to the preoperative planning.(Fig.2,3) Now the selected piece was freed from almost all attached tissues and osteotomized in the selected dimension. This bony piece, being in connection only with the vascular bundle of the circumflex scapula vessels, was covered with split skin grafts (Fig.4) and encapsulated with Goretex 1 mm sheets.(Fig.5) Muscles, subcutaneous tissue and skin was closed in layers and the prepared flap left in this position for 3 months.

Implants

Branemark implants MK II dim. 3.75 x 10/13/15.

Titanium miniplates and screws (Synthes) dim 1,5/ 2 mm. resp.

Microvascular reconstruction

After this healing period the implants are osseointegrated. The split skin attached to the bone has changed to a mucosa-like stable structure. Now the microsurgical transfer of the flap into the face was performed. Simultaneously the surgical procedure in the maxillofacial region and the harvesting of the prefabricated scapula flap (Fig.6) together with its vascular pedicle were performed by two teams. The Goretex membrane was removed, and the abutements and impression copings were attached to the implants before the flap was transferred into the maxillofacial region.(Fig.7a) According to the preoperative planning the flaps were first put into the correct position,(Fig.12a,b) and fixed with miniplates or by metal bars with methacrylate splints to the osseointegrated implants (Fig.11b,12c).

Venous grafts have been used to anastomose the vessel of the flap with the facial vessels and the iugularis vein (Fig.8a,b).

At this time the prefabricated scapula flap can be further combined with other flaps in complex midface reconstructions (Fig.7b,8b,11b,c).

RESULTS

Two patents with maxillofacial defects of different extensions were selected for the demonstration of our surgical concept. In case one a 58 years old female patient was left with a hemimaxillectomy following resection of a protruding meningeoma of the skull 13 years ago. (Fig.9a,b). The preoperative planning before reconstruction was done by using stereolithographic models (Fig.9c) together with 3D imaging and interactive manipulation of CT datas including orthognathic and gnathological aspects as described above (not shown in detail).

Additional to case one a second case of a 27 years old male patient with a huge maxillary and midface defect is reported: Following radiotherapy of a maxillary tumor 5 years before, the patient lost his right maxilla, anterior parts of the left maxilla, the right zygoma, his right eye, soft tissues of the cheek and the right side of the nose (Fig.10 a-c).

In both cases the reconstruction of the alveolar crest with implants and the hard palate was successfully performed with a prefabricated scapula flap.

Nurished by the same vascular pedicle, in case two, a second scapula bone flap together with the teres major muscle and a scapula skin flap (Fig.7b.) was transfered to reconstruct the corpus maxillae and apertura piriformis and the missing soft tissue of the right cheek. A nonvascularized bony piece served for the reconstruction of the nose. The schematic drawing of Figure 8b. illustrates our surgical procedure. For preoperative planning two stereolithographic models from the skull as well as from the scapula (CT controls after flap prefabrication) were used (Fig. 11a-c).

Flap fixation happened in the same way as in case 1 using titanium miniplate osteosynthesis. Here we fixed the miniplates to the osseointegrated implants of the prefabricated scapula flap. (seen in Fig. 11b).

In both cases the transplanted flaps healed nicely. Secondary procedures for flap fittening, debulking of soft tissues and preprosthetic surgery were not necessary.The split skin graft placed directly onto the bony flap during prefabrication changed to a sort of oral pseudomucosa which hardly can be distinguished from the surrounding real mucosa. (Fig.13.)

Furthermore the shape of the transplanted scapula flap imitates the alveolar ridge and the vault of the palate in an excellent way. (Fig.13)

The implants in a correct anatomical position and inclination served for dental rehabilitation by bone anchored bridges, avoiding mucosa supported and implant retained prosthesis in the reconstructed area. (Fig.13).

In case two the midface reconstruction was fully successful, (Fig.14a) and every transplanted vascularized tissue healed without complication. The patient 4 months later is demonstrated in Fig .14 b. For eye reconstruction a conventional implant fixed maxillofacial prostesis is under process.

DISCUSSION

Up to now, a stepwise reconstruction of the maxillary stability, esthetic contour and dental rehabilitation in the facial region has been favoured by many authors, and the achievement of several goals in a "at one time reconstruction" with prefabricated flaps in the maxillofacial region seemed to be technically not feasible. (Reuther, 1992; Haßfeld, et al., 1992; Betz, et al., 1993.)

In contrast, in 1995, Jacques Baudet reported on his ten years experience with prefabricated cutaneous flaps, offering a quite new perspective in plastic reconstructive surgery.

In the present paper we demonstrate our diagnostic and surgical method of flap prefabrication.

Our concept of creating a stable thin layer of soft tissue coverage in connection with an improved flap design already in the donor region, prevents a bulky intraoral mass that impairs oral function. Therefore a lot of preprosthetic surgery which is necessary to reach function after conventional stepwise reconstruction (Hoffmeister and Ewers, 1986), can be avoided.

In contrast to dermal and jejunum flaps e.g. this during prefabrication created "neogingiva" is less susceptible to infections around the implant.

Histological investigations of our good clinical results are under way with special emphasis on the histological changes of the split skin graft during prefabrication and after reconstruction, and on osseointegration of implants in prefabricated flaps. (These results which will be published separately.)

In conventional surgical methods periimplantory inflammations appear nearly always in form of long-lasting chronic proliferative granulations and-/ or abscesses often leading to loss of implants and resorption of the skeletal transplant.

Beyond the established use of implants, their application in microsurgical reconstruction is demonstrated for the first time both for the entire flap prefabrication and flap fixation.

As a ultimative perequisite for a correct anatomical tissue prefabrication a comprehensive preoperative planning by three-dimensional imaging and interactive manipulation of CT data, including cephalometric, gnathological and functional aspects, is necessary. In addition the use of stereolithographic organ models e.g. allow planning with a touchable object.

Obviously only the preoperative definition of all relevant factors by all these diagnostic measurements makes the "at one time reconstruction" possible at all.

The clinical approach i.e. operation planning, bony and soft tissue reconstruction, implant placement, flap fixation and osteosynthesis as well as microsurgical revascularisation, can only be performed in a close interdisciplinary cooperation.

Our surgical concept offer several advantages:

1. The tissue prefabrication together with the comprehensive diagnosis mentioned above results in a higher precision of reconstructive surgery due to a improved flap design, which is a absolute prerequisite for the "at one time "reconstruction in the maxillofacial area.
2. Osseointegrated implants can be used either for flap fixation, and/or immediate dental rehabilitation after reconstruction; the "neogingiva" offer stable periimplantory soft tissue conditiones soon postoperatively.
3. Moreover this "at one time"-reconstruction improves the psychosocial situation of the patients who frequently had to live with unsatisfying results of stepwise surgery in the face.

In our view a prefabricated flap has to comprise all components of the maxillofacial region to be reconstructed (bony flap, soft tissue lining, implants, vascular bundle etc.) The reconstruction in the maxillofacial area has to be done without major modifications of the prefabricated flap during surgery.

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Legends to figures

Pictures are available on request kurt.vinzenz@vienna.at