Maxilla Allograft for Transplantation: An Anatomical Study

Maxillofacial Bony Considerations in Facial Transplantation

Alloplastic facial transplantation has become a new rung on the proverbial reconstructive ladder for severe facial wounds in the past couple of decades. Since the first transfer including bony components in 2006, numerous facial allotransplantations across many countries have been successfully performed, many incorporating multiple bony elements of the face. There are many unique considerations to facial transplantation of bone, however, beyond the considerations of simple soft tissue transfer. Herein, we review the current literature and considerations specific to bony facial transplantation focusing on the pertinent surgical anatomy, preoperative planning needs, intraoperative harvest and inset considerations, and postoperative protocols.

Distribution of the maxillary artery in the deep regions of the face and the maxilla: Clinical applications

Composite tissue allotransplantation of the face has led to renewed interest in the vascularization of the maxilla. The maxillary artery, which is deep within the tissue and difficult to access, is considered the main artery of the maxilla. The objective of this study was to describe the distribution of the maxillary artery in the deep regions of the face and maxilla. Twenty-four maxillae were studied, of which 20 were injected with latex and four with India ink. The maxillary artery in the pterygopalatine fossa gave rise to the sphenopalatine artery, infraorbital artery, descending palatine artery, and posterior superior alveolar artery in all 24 cases. The posterior superior alveolar artery gave rise to a periosteal branch and an intraosseous branch (in the wall of the maxillary sinus) in 18 cases. The branch passed through part of the wall and the entire wall in eight and ten cases, respectively, and anastomosed at the anterior nasal spine and the infraorbital foramen. The descending palatine artery presented as a single trunk in four cases, a greater palatine artery and a lower palatine artery in 18 cases, and four branches in two cases. Intraosseous and periosteal anastomoses were found along with anastomosis through the incisive foramen, which were obstructed in three cases. The vascular territories were studied. The maxillary artery created an intraosseous and periosteal anastomotic network, explaining the supply pathways during different surgical procedures, risk of hemorrhage with orthognathic surgery (Le Fort type I) in a sinus lift for preimplant surgery, and the vascular territories.

A new total hemiface allotransplantation model in rats

INTRODUCTION

Vascularized composite allotransplantation (VCA), a new reconstructive option for patients suffering from extensive facial defects leads to superior functional and aesthetic outcomes compared to the standard autologous reconstruction. Among VCA recipients, each case involves different facial structures and tissues depending on the patient's injury, thus drawing conclusions on the mechanism of immune interactions between the donor and recipient is challenging. This study introduces a new total hemiface VCA model, including scalp, external ear, mystacial pad, premaxilla, upper/lower lids, nose, and upper/lower lips to evaluate the effect of transplantation of multitissue VCA on the recipient's immune response.

MATERIAL AND METHODS

Ten hemiface allotransplantations were performed in two groups between Lewis-Lewis (isograft) and LBN-Lewis (allograft) rats. Cyclosporine A (CsA) monotherapy was applied in the allograft group to prevent rejection.

RESULTS

All flaps survived up to 100 days post-transplant. The mean warm ischemia time was 45 minutes. Histological analysis revealed normal bone, cartilage (ear and nose), conjunctiva, palpebra, and eyelashes. Flow cytometry confirmed donor-specific chimerism for T cells (CD4/RT1(n) and CD8/RT1(n)) and B cells (CD45RA/RT1(n)) in the peripheral blood of all rats in the allotransplantation group. At post-transplant day 7, chimerism levels were at 1.68% for CD4/RT1(n) , 0.46% for CD8/RT1(n) and 0.64% for CD45RA/RT1(n). However, chimerism levels for CD4/RT1(n), CD8/RT1(n), and CD45RA/RT1(n) populations decreased at long-term follow-up (at post-transplant day 100) to 0.08%, 0.04%, and 0.23%, respectively.

CONCLUSION

The feasibility and long-term survival of the new hemiface VCA transplantation model was confirmed, donor-specific chimerism and post-transplant tissue changes were evaluated.

Anatomical study of the vascular territories of the maxilla: role of the facial artery in allotransplantation

BACKGROUND

Facial composite tissue allotransplantation has recently become a surgical option. The maxilla, which forms the upper jaw and plays an important role in facial allotransplantation, consists of the maxillary and facial arteries. The maxillary artery is located deep within the tissue and considered the main artery of the maxilla; however, the facial artery is easy to access. The objective of this study was to examine the territories of the maxillary and facial arteries within the maxilla.

MATERIALS AND METHODS

We excised and examined 22 maxillae. Of these, 18 were injected with latex and four with India ink.

RESULTS

We observed that the ascending palatine artery, which was collateral with the facial artery, vascularized the maxilla through its dorsal part. The facial artery vascularized the maxilla through its ventral part with the philtral and columellar branches of the superior labial artery. Therefore, the facial artery formed, through the nasal and palatine mucosa, an arterial circle with a dorsal and ventral pole. Angiosomes formed by both the facial and maxillary arteries were also observed. The India ink injected into the facial and maxillary arteries delineated specific territories for each artery.

DISCUSSION

This study allowed us to determine the anatomical structures that provide vascularization to the maxilla and describe their different forms. The whole of the maxilla was vascularized by the facial artery, despite the caution imposed by several studies on the removal of the facial artery alone. Indeed, the removal technique was found to be safer when it preserved the anastomoses between the facial and maxillary arteries. Therefore, previous clinical experience and our anatomical study definitively demonstrate that the facial artery vascularizes the maxilla.

Vascularization of the facial bones by the facial artery: implications for full face allotransplantation

BACKGROUND

The maxillary artery is recognized as the main vascular supply of the facial bones; nonetheless, clinical evidence supports a codominant role for the facial artery. This study explores the extent of the facial skeleton within a facial allograft that can be harvested based on the facial artery.

METHODS

Twenty-three cadaver heads were used in this study. In 12 heads, the facial, superficial temporal, and maxillary arteries were injected. In one head, facial artery angiography was performed. Ten facial allografts were raised. The soft tissues were dissected to show the arterial anastomotic connections. Radiographs and computed tomographic scans were obtained.

RESULTS

Constant anastomosis between the facial, inferior alveolar, and infraorbital arteries at the mental and infraorbital foramina were found. The facial artery vascularized the homolateral mandibular symphysis, body, and ramus. The condylar and coronoid processes were vascularized in 67 percent of the allografts. The homolateral maxilla was contrasted in all allografts. The alveolar and palatine processes contained the contrast in 83 percent of specimens. The maxillary process of the zygomatic bone was perfused in all allografts, followed by the body, frontal (83 percent), and temporal processes (67 percent). The nasal lateral wall and septum were vascularized in 83 percent of the allografts. The medial and lateral orbital walls and the orbital floor were stained in all specimens. The zygomatic process of the temporal bone was the least perfused bone.

CONCLUSION

A composite allograft containing 90 to 95 percent of the facial bones can be based on bilateral facial arteries.

Craniomaxillofacial reconstruction using allotransplantation and tissue engineering: challenges, opportunities, and potential synergy

The face is composed of an intricate underlying bony/cartilaginous framework that supports muscle, secretory organs, and sophisticated skin/subcutaneous structures. These components are attached through numerous ligaments and interact dynamically with a vast neurovascular network. The most sophisticated autologous reconstructive techniques, utilizing composite free-tissue flaps, are often inadequate to restore extensive maxillofacial defects. Massive craniomaxillofacial (CMF) defects resulting from trauma, oncologic resection, or congenital deformity present a unique challenge to reconstructive surgeons. Therefore, recent advances in craniofacial surgery and immunotherapy spurred the innovation of composite tissue allotransplantation (CTA), which permits reconstruction with tissue composed of all necessary components. However, CMF allotransplantation carries with it side effects of lifelong immunosuppression. Furthermore, the donor skeletal framework may not provide an ideal match, resulting in less than ideal occlusion and soft-tissue anthropometrics. An alternative to transplantation, tissue engineering, has provided hope for regenerating missing tissue and avoiding the need for immunosuppression. Many tissue subtypes, including bone and cartilage, have been successfully created, with sparse reports of clinical application. Tissue-engineered composite tissue required for complete CMF reconstruction continues to elude development, with vascular supply and tissue interactions posing the largest remaining obstacles. We report herein the current status and limitations of CTA and tissue engineering. Furthermore, we describe for the first time our vision of hybridization of CTA and engineering, utilizing the strengths of each strategy.

Vascular considerations in composite midfacial allotransplantation

BACKGROUND

Advances in microsurgery and immunosuppression have allowed for facial reconstruction at a qualitatively new level with facial composite tissue allografts. Although donor tissue recovery is unique for each patient, transplantation of the maxilla and overlying soft tissues will be a frequent indication. Vascularity of the maxilla and palate, supplied by facial arteries alone, has been a concern. Based on cadaver dissections and a clinical case, vascular considerations for transplantation of the entire midface are discussed.

METHODS

To prepare for central facial transplantation in an identified patient, a preclinical dissection was completed on four cadavers. In April of 2009, an extended midfacial allotransplantation was performed. The flap included the entire group of facial mimetic muscles with overlying skin, sensory and motor nerves, nose, upper lip, maxilla, teeth, and hard palate.

RESULTS

The preclinical study identified key anatomical structures for inclusion in the composite tissue allograft. Moreover, dissections showed that the facial and angular blood vessels were connected to branches of the maxillary vessels through an anastomotic network organized around the periosteum and bony canals of the midfacial skeleton. Transplantation of a central face allograft including the maxilla and palate was anticipated to be feasible. A technically successful clinical case was completed.

CONCLUSIONS

Anatomical and clinical observations elucidated several technical points related to composite tissue transplantation of the midface. Careful graft harvest, appropriate selection of donor and recipient vessels, complete allograft revascularization, and restoration of sensory and motor function are critical to making face transplant surgery safe and functional.