Successful Grafting with Allogenic Bone Following Benign Pediatric Mandibular Tumor Removal

Summary:

The reconstruction of mandibular defects in pediatric patients presents a significant surgical challenge due to the unique anatomic and developmental considerations of the growing mandible. Advancements in bone tissue engineering have introduced the use of bone graft substitutes and osteoinductive materials such as demineralized bone matrix (DBX), recombinant human bone morphogenetic proteins (BMP), and freeze-dried bone chips (FDBC). Although the current literature using allogenic bone grafts for mandibular defects is limited, existing studies have demonstrated its efficacy in the immediate reconstruction of mandibular defects following benign tumor ablation. In this case series, we evaluate the outcomes of immediate mandibular reconstruction using a combination of DBX, rhBMP-2, and FDBC following 6 benign mandibular tumor removals. At 6 months postoperatively, we achieved no graft failures with 4 (67%) graft sites achieving 100% graft take and 2 (33%) defects achieving approximately 80% graft take. Our results indicate that bone grafting with DBX, BMP, and FDBC could potentially represent a valuable reconstructive technique for pediatric mandibular defects, offering a low-morbid and cost-effective alternative to traditional autologous grafting methods.

The reconstruction of mandibular defects in pediatric patients presents a significant surgical challenge due to the unique anatomic and developmental considerations of the growing mandible. Although benign mandibular tumors are relatively rare in children, their treatment often involves resection, resulting in continuity defects that require reconstruction.¹ Traditional approaches, including autologous vascularized free flaps and autografts, have demonstrated success, but are associated with prolonged operative times and significant donor-site morbidity.²

Advancements in bone tissue engineering have introduced the use of bone graft substitutes and osteoinductive materials such as demineralized bone matrix (DBX), recombinant human bone morphogenetic proteins (BMPs), and freeze-dried bone chips (FDBCs). These substitutes offer new options in mandibular reconstruction, providing osteoinductive and osteoconductive properties that promote bone regeneration and integration while avoiding the need for autologous grafts.³ However, data using these materials specific to pediatric populations is limited.⁴

In this case series, we evaluate the outcomes of immediate mandibular reconstruction using a combination of DBX, rhBMP-2, and FDBC in 4 pediatric patients following resection of benign mandibular tumors. This study aims to contribute to the growing body of evidence supporting the use of bioimplants in pediatric mandibular reconstruction, highlighting their potential to minimize morbidity and optimize outcomes.

METHODS

Study Participants

A retrospective chart review was conducted to identify all patients who underwent removal of benign mandibular tumors, followed by immediate bone grafting using DBX, rhBMP-2, and FDBC from January 2024 to December 2024 by a single surgeon (B.G.). These patients had no history of chemotherapy or radiation. Patients and patient guardians were counseled on the relative risks, benefits, and alternative treatment options, including a discussion on how BMP use is not Food and Drug Administration–approved in children and carries a potential risk of malignant transformation or heterotopic ossification. All families elected to undergo mandibular reconstruction using our grafting technique. At our institution, we have implemented a standardized computed tomography (CT) protocol at approximately 6 months postoperatively to evaluate graft take in this cohort of patients. Patient characteristics, including age at surgery; sex; relevant comorbidities; follow-up from procedure; and tumor diagnosis, quantity, and size were collected and analyzed.

Surgical Technique

After obtaining informed consent, the patient was taken to the operating room and placed in supine position. All resections and mandibular reconstructions were performed using a similar technique. Following infiltration with local anesthetic, an incision was made intraorally at the level of the lower buccal mucosal sulcus, exposing the involved mandibular bone. A piezoelectric bone cutter was used to make incisions in the outer cortex of the mandible over the tumor. The entire tumor was removed with aggressive curettage, ensuring that no residual tumor remained. Injury to the remaining normal bone at the level of the excision cavity was performed using an osteotome to promote healing. To address the remaining defect, a combination of cadaveric FDBC (MTF, Edison, NJ), BMP-2 (Infuse Medtronic Sofamor Danek), and DBX (Inject, Depuy Synthes, Solothurn, Switzerland), in an approximate 80:10:10 ratio, respectively, was placed as a bone graft. Closure was performed over the graft in layers using interrupted Vicryl sutures (Ethicon, Inc., Somerville, NJ).

RESULTS

A total of 6 mandibular tumors (4 patients) were included in the study. All patients were female, with a mean age of 10.5 years. Tumor diagnoses included ameloblastic fibroma (1 tumor, 17%), odontogenic keratocyst (4 tumors, 67%), and fibro-osseus lesions secondary to cherubism (1 tumor, 17%). Mean defect size was 2.6 cm × 1.3 cm (34.2 cm²). Following resection, all mandibular defects were grafted using a combination of DBX, rhBMP-2, and FDBC. Additional patient characteristics are included in Table 1.

Table 1.

Patient and Tumor Characteristics with Corresponding Outcomes

	Sex	Age, y	Comorbidity	Tumor Diagnosis	No. Tumors	Tumor Size on Aixal CT (cm)	Graft Take, %	Follow-up, mo
1	Female	7	None	Ameloblastic fibroma	1	1.6 cm × 1.1 cm	100	6
2	Female	15	Gorlin syndrome	Odontogenic keratocyst	3	4.7 cm × 1.2 cm	80	6
						3.2 cm × 1.1 cm	80
						1.0 cm × 0.6 cm	100
3	Female	13	Basal cell nevus syndrome	Odontogenic keratocyst	1	2.6 cm × 1.7 cm	100	6
4	Female	7	Cherubism	Fibro-osseus lesion	1	3.0 cm × 2.2 cm	100	7

No postoperative complications were observed. All patients were evaluated with a thin-cut CT scan at 6 months postoperatively with a mean follow-up period of 6.3 months. Graft take was evaluated via axial and coronal plane CT scans (Fig. 1). (See figure, Supplemental Digital Content 1, which displays [A] preoperative axial CT view of large mandibular ameloblastic fibroma involving the mandibular body with an uninterrupted molar tooth bud in a 7-year-old girl. B, Six-month postoperative axial CT view demonstrating 100% bone graft take at the level of the previous mandibular tumor site, https://links.lww.com/PRSGO/E86.) Of the 6 mandibular defects grafted, 4 (67%) graft sites achieved 100% graft take and 2 (33%) defects achieved approximately 80% graft take.

Fig. 1.

Axial CT of a mandibular keratocyst with postoperative outcome. A, Preoperative axial CT view of large parasymphaseal mandibular keratocyst in a 13-year-old girl. B, Six-month postoperative axial CT view demonstrating 100% bone graft take at the level of the previous mandibular tumor site.

DISCUSSION

Pediatric mandibular defects following benign tumor resection pose numerous reconstructive challenges. Allogenic bone grafts have the potential to revolutionize maxillofacial reconstruction, offering a promising alternative to traditional autologous bone grafting and free flap techniques for mandibular reconstruction. Compared with conventional autologous grafting, engineered bone substitutes eliminate donor site morbidity, decrease postoperative pain, and reduce overall hospital costs.⁵ Although the current literature using allogenic bone grafts for mandibular defects is limited, existing studies have demonstrated its efficacy in immediate reconstruction of mandibular defects following benign tumor ablation.^3,6–8

Initially, we used autologous bone grafting with successful outcomes for reconstructing these mandibular defects; however, limited bone stock in larger defects posed significant challenges, promoting our transition to allografts. The use of DBX, rhBMP-2, and FDBC was selected as the graft material based on our institutional experience using this combination for alveolar cleft repair.⁹ This bone graft mixture demonstrated consistent bony consolidation in the alveolar cleft, regardless of defect size. As a result, allografts become our preferred method, and we adopted this bone grafting technique for the patients in this series. Of note, theoretical risks have been raised about rhBMP-2 potentially inducing malignant transformation or heterotopic ossification. A meta-analysis in patients receiving rhBMP-2 in spinal fusion found a slight increase in cancer rates; however, it was determined inconclusive as the finding did not reach statistical significance.¹⁰

Our results indicate that mandibular grafting with DBX, rhBMP-2, and FDBC is a versatile and reliable reconstructive option for bony defects of the mandible with success rates that are comparable to other described allogenic grafting methods.^3,6–8 We experienced no graft failures, although 2 defect sites demonstrated an 80% graft take. This was likely due to the tumor being near the mandibular neurovascular bundle, resulting in soft-tissue interposition at the graft site and inadequate surface area for bony consolidation. However, in cases where our grafting material was placed directly on the bone within the encapsulated defect, graft take was 100%. Although this series represents a limited sample size, these findings suggest that placing the graft mixture directly onto the bone achieves successful bony consolidation at 6 months postoperatively. Inclusion of more patients and further longitudinal follow-up is needed to evaluate long-term outcomes of the primary graft.

CONCLUSIONS

Bone grafting with DBX, BMP, and FDBC may serve as an effective reconstructive approach for pediatric mandibular defects, potentially providing a low-morbid and cost-efficient alternative to traditional autologous grafting methods.

DISCLOSURE

The authors have no financial interest to declare in relation to the content of this article.