Application of osteomucoperiosteal flap in large unicystic ameloblastoma to promote early bone healing: An alternative to primary bone grafting.

BACKGROUND: The unicystic variety of ameloblastoma is reported to be significantly less prone to recurrence in young patients than its conventional counterpart, and therefore can be treated conservatively. This paper describes a technique of using an osteoperiosteal flap to allow complete enucleation of a unicystic ameloblastoma. The technique maintains the continuity of the mandible and restores full thickness as well as strength of the mandible to promote early healing. It also maintains blood supply and proper facial contour so that esthetics is unimpaired.
MATERIALS AND METHODS: We describe two cases of unicystic ameloblastoma in which we used an osteoperiosteal flap. This flap was then infractured at the lower border to obliterate the dead space.
RESULTS: The sequential radiographs demonstrate early incorporation of the graft and complete filling of the defect by 3 months. At 5 years of follow-up in our first case, complete healing of bone was observed.
CONCLUSIONS: We believe that these procedures can be the treatment of choice in such cases, especially with larger lesions, as these rapidly restore the patient's facial contour to normal as well as reduce the healing time.

Introduction

Surgical removal of large cyst/tumor leaves behind large bony cavity which should be addressed to promote early regeneration and healing. This can be accomplished by special surgical techniques or by limiting the volume of the blood clot in the cavity.[1] The former may be accomplished by approximating the bony walls of the cavity[2] or by saucerization like procedures, while the latter requires grafting with bone and bone substitutes or implantation with a variety of alloplastic materials.[3-8] Although these techniques have met with varying degrees of success clinically, their application is sometimes limited by availability, cost and propensity for additional surgical morbidity. The osteomucoperiosteal flap, as described by Yih et al.,[9] has been used by us with some modifications in large mandibular lesions with gratifying results. This article presents our technique of employing the osteomucoperiosteal flap for unicystic ameloblastoma of the mandible.

Materials and Methods

An informed consent was obtained from the patients and the study conformed to the ethical guidelines of the 1975 Declaration of Helsinki.

Case 1

A 13-year-old boy reported to the Department of Oral and Maxillofacial Surgery, Subharti Dental College, Meerut, in April 2005, with a large unilocular, radiolucent lesion that occupied most of the left mandibular ramus and coronoid process extending from the neck of the condyle to the left 1st molar region. The lesion was well contained within the bone, with expansion of the lateral cortex but no clinical or radiological perforation of the bone. Associated with the lesion was an unerupted 2nd molar. There was resorption of the distal root of the 1st molar [Figure 1a].

Figure 1

(a) Panoramic radiograph showing unilocular ameloblastoma of the left side of the mandible; (b) immediate post–operative; (c) 3 months post-operative; (d) 5 years post-operative

An incisional biopsy of the lesion revealed it to be a unicystic follicular ameloblastoma.

Case 2

A 28-year-old man reported to the Department of Oral and Maxillofacial Surgery, Subharti Dental College, Meerut, in October 2008, with a large, infected unilocular, radiolucent lesion of the right mandibular body, part of the ramus and extending almost to the coronoid area. Associated with the lesion was an unerupted 3rd molar [Figure 2a].

Figure 2

(a) Panoramic radiograph showing unilocular ameloblastoma of the right side of the mandible; (b) immediate post-operative; (c) 3 months post-operative

A provisional diagnosis of unicystic ameloblastoma was made which was histopathologically reported as follicular ameloblastoma.

Technique

Under general anesthesia , an intraoral incision was made through mucosal and submucosal tissue, leaving the periosteum undisturbed over the bone surface. A flap was developed in this plane and reflected beyond the maximum bulge of the lesion [Figure 3a].

Figure 3

(a) Incision; (b) mucosal fl ap with osteoperiosteal incision; (c) refl ected osteoperiosteal flap by fracturing the inferior osseous portion of the flap; (d) placement of the osteoperiosteal flap into the cavity after removal of the tumor; (e) closure of the mucosal flap

The periosteum was then incised along the superior and anterior margins of the proposed osteotomy cut and reflected to about a centimeter from the bone. Careful undermining of this layer was done at the posterior margin in order to preserve continuity of the periosteum across the bony cut at this site. The osteotomy was then performed using a No. 8 round bur and a No. 701 fissure bur, keeping in mind that the lesion was not perforated and that the maximum bulk of the lesion was exposed [Figure 3b].

The inferior edges of the anterior and posterior osteotomy cuts were placed just above the lower or posterior border of the mandible so as to facilitate a clean fracture at the inferior margin. An osteoperiosteal flap was then developed and hinged laterally to expose the cystic wall [Figure 3c].

The lesion was then enucleated and the resultant surgical defect was treated with Carnoy's solution while preserving the inferior alveolar nerve. The osteoperiosteal flap was then infractured at the lower border by digital pressure so that the volume of the cavity was reduced [Figure 3d].

Any discrepancy of crestal height of the medial and lateral cortices was adjusted by trimming and the lateral cortex was stabilized with wire osteosynthesis in our first case, while the lateral cortex was kept in collapsed position in our second case. The mucosa and periosteum were sutured at the superior margin as one layer with the lingual tissues to achieve a primary closure [Figure 3e].

Results

Postoperative recovery was uneventful and healing by primary intention occurred in both cases. The patients were closely followed up for early signs of infection, pathological fracture, bone resorption or recurrence of lesion. None of these complications occurred in both of the patients and radiological signs of bone regeneration and remodeling were appreciable within 3 months [Figure 2b, c]. During the follow-up period of 5 years for the first case, satisfying degree of bone architecture and good facial contour were achieved [Figure 1b–d].

Discussion

In the past, attempts have been made to reduce the size of the bony cavity with a variety of materials.[2-8] However, none of them was found to be successful in routine clinical practice. To overcome this, the pathologic cavity was managed by packing the defect or turning a mucosal flap into it and then packing with iodoform gauze.[10] Healing in these cases is slow and accompanied by increased morbidity.

Brosch[11] in 1957 exposed the entire buccal cortex beyond the full extent of the cyst. Decortication and removal of the lateral cortical plate was performed and the cyst was enucleated in toto. The adjacent tissues were collapsed into the defect to reduce the dead space. Brosch procedure was modified by Hillel Ephros et al.[12] in 1991 in which the large Odontogenic Keratocyst, the attached impacted mandibular 3rd molar, entire coronoid process and lateral cortex of the posterior body and ramus were removed en bloc. Medial cortical bone in the areas of the perforation was removed, peripheral ostectomy was performed and the flap was sutured primarily.

Moose[13] used a muco-osteoperiosteal flap to reinforce the closure. Hong et al.[2] described a method for reducing the size of the cystic defect in which a muco-osteoperiosteal flap was developed and reflected by the removal of a strip of the mandible at the inferior aspect of the defect. After cystectomy, the dead space was obliterated by two means: firstly the space was implanted with bony chips obtained from the inferior aspect of the bony cavity and secondly by collapsing a muco-osteoperiosteal flap.

In 1991, Yung and Morita[9] described a technique of using an osteomucoperiosteal flap in the treatment of 13 cystic lesions which could obliterate large bony defects effectively. The advantages of this technique are that it 1) obliterates dead space and hence facilitates hemostasis; 2) facilitates healing and resists infection; 3) promotes bone regeneration; 4) preserves all vital tissues and 5) avoids the use of secondary grafting procedures.

It is a well-established fact that unicystic ameloblastomas involving the ramus of the mandible do not require resection and respond well to careful enucleation and chemical cauterization.[14] In a review by Samman and Lau,[14] it was found that large unicystic ameloblastomas are usually approached extraorally with decortication followed by enucleation and application of Carnoy's solution. The wound is then either closed primarily or packed with ribbon gauze to facilitate healing. Some of the problems that may occur with this procedure are hematoma formation and delayed healing, wound breakdown and infection, facial deformity and formation of a knife-edge ridge.

We have modified the technique for the large lesions involving the ramus and body region of the mandible by deliberately incising the periosteum at the superior and anterior margins so as to hinge the flap laterally without resistance. We find that it vastly improves access and visibility of the lesion which can then be easily enucleated. The second modification is to trim the superior margins to the same height, which prevents the development of a knife-edge ridge.

The rationale for our technique in which we used an osteoperiosteal flap was enucleation of the lesion with retention of the blood supply as the flap is pedicled. This facilitates healing and resists infection. Moreover, the flap has the potential for regeneration and obliterates the dead space. Also, it prevents collapse of the facial soft tissues and minimizes postoperative deformity. The sequential radiographs demonstrate early incorporation of the graft and complete filling of the defect by 3 months. At this time, there was normal trabecular pattern and normal facial contour with no signs of numbness of lips. At 5 years of follow-up in our first case, complete healing of bone was observed.

This technique is best suited for resection of the unilocular benign lesions in young individuals as the facial esthetics is better provided and chances of numbness of the lower lip are minimal with this technique. However, careful case selection and treatment planning is required, and patients with thinned out buccal cortex, and with the presence of aggressive lesions in which seeding of the tumor into the replaced bone is anticipated are excluded from this technique. Moreover, periosteal stripping and inadvertent fracturing of the buccal cortical plate is to be prevented for the success of the technique.

Conclusion

We believe that these procedures can be the treatment of choice in such cases, especially with larger lesions, as these rapidly restore the patient's facial contour to normal as well as reduce the healing time. Larger studies need to be pursued to provide better evidence of its effectiveness.