Management of a Patient with Severe
Mandibular Atrophy:
A Case Study Using Inferior Cadaver Graft

Yen Chen, BS* , Brian Lambert, DDS, MD**; Shahid Aziz, DMD***; Howard Israel, DDS ****

ABSTRACT

A variety of surgical procedures have been derived for augmenting the atrophic mandible. The visor-sandwich osteotomy augmentation and onlay bone grafts are among the various methods used for rehabilitating the lower third of the face and restoring oral function. However, the morbidity and less than desirable results from these techniques have provided the impetus for finding a more ideal solution to the problem of mandibular augmentation. In patients with insufficient bone, the use of an inferior border graft using freeze-dried cadaveric mandible packed with autogenous cancellous iliac bone should be considered. This technique appears to maintain ridge height and have low morbidity. (Col Dent Rev 2:7, 1997)

INTRODUCTION

Bone resorption in the mandible and maxilla is a consequence of edentulism. As atrophy of the mandible progresses, the ability to maintain masticatory function may become significantly compromised. These functional disabilities may be morphological, due to the decreased area available for support and encroachment of surrounding mobile tissues onto the denture border thereby reducing the support, stability and physical retention of the denture.3,5

There are three important areas to consider when treating the severely atrophic mandible: the superior border, the body of the atrophic mandible itself, and the inferior border. Several methods of reconstruction have been used with variable results. These include: onlay bone grafts, visor-sandwich osteotomy augmentation, hydroxyapatite ridge augmentation, vestibuloplasty or lowering the

floor of the mouth, osseointegrated endosseous implants, subperiosteal implants, and transmandibular implants. A mandibular inferior border graft has the potential to add bone volume to an extremely atrophic mandible and to provide a viable site for osseointegrated implants.9,14

CASE REPORT

A 71 year-old Hispanic woman presented to Columbia University School of Dental and Oral Surgery with a chief complaint of inability to articulate and eat due to an ill-fitting denture.

The patient was examined by the Prosthetic Division and referred to the Division of Oral and Maxillofacial Surgery for possible surgical intervention. Upon completion of the evaluation, the treatment plan included a transmandibular implant. Important aspects taken into consideration in this treatment plan included the patient's physical, psychological and financial status, and parafunctional habits associated with her focal dystonia. The patient exhibited Meigel's syndrome, which is a combination of blepharospasm and oromandibular dystonia. These involuntary dystonic and dyskinetic movements made it difficult for her to wear conventional dentures.

In June 1996, the patient underwent placement of a transmandibular implant. Her post-operative course was complicated by an infection which developed 3 weeks postoperatively and subsequently resulted in bilateral pathological fractures of the mandible (Figure 1). The patient was admitted at this time with a draining fistulous tract from her submental region. Her hospitalization therefore included intravenous antibiotics, removal of the transmandibular implant and local debridement. An intraoral acrylic splint was placed with circumandibular wires to immobilize the segments of the mandible post-operatively. The patient's course was uneventful and the mandibular fractures healed without infection.

Figure 1: Pre-operatively panoramic radiograph of severely
atrophic mandible with bilateral non-union fractures.

Due to the severe atrophy, bilateral non-union fibrous tissues formed at the fracture sites. A CT scan and plain films were obtained to evaluate the mandible. The patient was then evaluated for a mandibular reconstruction utilizing a human cadaveric freeze-dried mandibular bone crib with autogenous iliac cancellous bone.

In October 1996, the patient underwent mandibular reconstruction. A visor flap was delineated extending from the mastoid region of the patient's right posterior neck to the contralateral mastoid region following Langer's lines, and was carried down to the mandible.

After adequately exposing the mandible, intervening soft tissue and fibrous tissue were observed in the area of the fracture sites. This tissue was debrided and sent for pathologic examination. The human cadaver mandible was shaped to create an inferior border bone crib (Figure 2). It was contoured to integrate into the soft tissue at the inferior border of the anterior mandible, thus, designed to permit stabilization on the two non-union fracture sites, as well as the proximal body of the mandible bilaterally. It was also prepared with relief in the area of the genial tubercles where the genioglossus muscle was left intact.

Figure 2: Prepared cadaver tray.

Iliac crest cancellous bone was then condensed and packed into the prepared cadaveric mandible. The cadaveric bone was stabilized to the patient's mandible with 26 gauge stainless steel wire ligature (Figure 3). Intraosseous wire ligatures were also used to provide fixation for the bilateral non-union fractures of the mandible. The wound was irrigated and closed in layers. Two drains were placed post-operatively at the wound bed in order to decrease the risk of a flap compromising hematoma. The post-operative hospitalization was without complication. Social services, home health services and physical therapy were arranged prior to discharge. The patient was seen at 3 and 6 months following the surgery and the mandible healed with bone and stabilization of the fracture sites. Since the mandibular ridge height was extended significantly, endosseous titanium implants will be placed (Figure 4).

Figure 3: Ligation securely fastened cadaver graft to the
mandible.

Figure 4: Panoramic radiograph of the grafted mandible
three months post-operatively.

DISCUSSION

Surgical rehabilitation of the lower third of the face for patients with severe mandibular atrophy has been attempted using hydroxyapatite ridge augmentation, visor-sandwich osteotomy, and onlay bone grafts with variable outcomes.

The onlay bone graft is indicated when severe resorption of the mandible results in inadequate height and contour and potential risk of fracture. The disadvantages of this technique are: 1) the need for secondary soft tissue surgery at a later date to provide an enlarged area of fixed tissue in the primary implant area, 2) the delay in wearing dentures for six to eight months after graft surgery and, 3) the possibility of significant post-operative resorption of the graft.

The visor-sandwich osteotomy has been reported to have minimal resorption, however, there is significant morbidity with this difficult operation. In this technique, the mandible is sectioned in an oblique direction and an iliac crest graft is placed between the fragments for augmentation of the atrophic mandible. If the absolute height of the mandible is less than 2 cm, this technique does not increase the mandibular height sufficiently. Other limitations are that there is a higher risk of lower lip paresthesia and the patient will be unable to wear a denture for 3 to 5 months. In addition, the resultant ridge has been reported to be minimally retentive.6,13,14

Treatment options such as vestibuloplasty or lowering the floor of the mouth are also available for mandibular reconstruction. These options are not applicable for extremely atrophic jaws because their success is dependent on many factors, including the presence of adequate residual alveolar height, width and contour.2,7

All of the above techniques use an intraoral approach for graft placement. The patient is at higher risk for dehiscence, contamination and secondary infection.14 These techniques also result in significant changes in anatomy which requires a reline, rebase or remake of the prosthesis if the patient desires to wear a prosthesis during the graft healing period.14

The use of osseointegrated implants has been shown to be an effective method for restoring the dentition.2,4 A minimum of 5 mm of bone height and 6 mm of bone width is recommended for endosseous implant placement.8,15 When less than 5 mm of bone height precludes the direct placement of implants, augmentation of the mandible inferiorly may be considered.1

A mandibular inferior border graft has the potential to add bone volume to an extremely atrophic mandible and to provide a viable site for osseointegrated implants. This extraoral approach and the use of cadaveric mandibles for restoration of defects have been reported by Marx et al.11,12 and Quinn.14 The patient is able to continue using an existing dental prosthesis with minimal modification during the post-operative healing period. After a healing period of 4 to 6 months, osseointegrated implants are placed in the augmented mandible.14

CONCLUSION

Facial and oral rehabilitation of the lower third of the face in patients with extreme mandibular atrophy has been attempted with a variety of treatments. Grafting procedures such as visor-sandwich and onlay bone grafts have met with variable results.

When bone height is less than 5 mm, augmentation of the ridge using an inferior border graft may be considered. This procedure requires a freeze-dried, gamma irradiated cadaveric mandible which has been hollowed out and packed with autogenous iliac cancellous bone, then secured to the inferior border of the atrophic mandible using an extraoral approach. An extended healing time of 4 to 6 months is necessary for the graft to ossify prior to the placement of implants.

Although initially stable, long term follow-up of patients treated with the inferior border graft is necessary. For the short term, it seems that the mandibular inferior cadaver graft has the potential to increase bone mass to a severely atrophic mandible and this, with the use of implants, can restore masticatory function to these patients.

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