Subcutaneous emphysema secondary to autogenous bone grafting: a case report

Abstract

Background

Subcutaneous emphysema, a rare complication after dental procedures, involves localized tissue swelling caused by air trapped within subcutaneous tissues. Its occurrence following autogenous bone grafting is extremely rare, with limited cases reported.

Case presentation

This article describes delayed subcutaneous emphysema following autogenous bone grafting at both the donor site and the recipient site. The patient presented facial and labial swelling. Symptoms, clinical findings, and postoperative CBCT confirmed subcutaneous emphysema.

Conclusions

This case report highlights the rare occurrence of subcutaneous emphysema following autogenous bone grafting, with simultaneous involvement of donor and recipient sites. It emphasizes the need for heightened clinical awareness, timely diagnosis, and appropriate preventive measures to reduce the risk of SE in bone augmentation procedures.

Background

Oral implantation has a significant role in the rehabilitation of patients. Bone reconstruction techniques have been advanced in order to optimize the esthetic and functional outcome [1]. Autogenous bone grafting is widely recognized as the gold standard for alveolar bone augmentation [1]. Complications related to bone graft harvesting and placement, including graft contamination, wound dehiscence, infection and graft resorption, have been well documented in previous studies [2]. However, its potential complications, particularly rare ones like subcutaneous emphysema (SE), are underreported, leaving clinicians underprepared for such occurrences. SE involves local tissue swelling when air is trapped under the subcutaneous tissue, which usually presents with a characteristic “crackling” sensation when touched. Iatrogenic factors are now considered the primary cause of SE [3]. In dentistry, SE is an uncommon but potentially significant complication in dental procedures [3, 4] (tooth extraction [5, 6], restorative treatment [6, 7], sandblasting treatment [8, 9], root canal treatment [6], laser treatment [10] and surgery [11, 12]), particularly involving manipulation of soft and hard tissues. This condition is characterized by the infiltration of gas into subcutaneous tissues, leading to swelling and discomfort. However, there are no reported cases of subcutaneous emphysema associated with autologous bone grafting. Only 4 recorded SEs resulting from dental bone augmentation surgery have been reported, all of which are associated with sinus lift [13, 14], and there are no previous reports of SE after autogenous bone grafting [3, 15]. Unlike prior cases, SE in this instance simultaneously affected both the donor site (mandibular ramus) and the recipient site (maxillary anterior region) due to the anatomical region and surgical technique involved. This dual-site involvement highlights the multifactorial mechanisms of air entry and propagation, likely influenced by surgical techniques, anatomical variations, and tissue manipulation during the procedure. These features make this case particularly valuable for understanding the risk factors and preventive strategies in advanced bone grafting surgeries.

Case presentation

A 33-year-old, healthy, nonsmoking man presented to the Department of Prosthodontics with the chief complaint of a trauma-affected upper right incisor that was extracted 20 years ago. The patient’s medical history was unremarkable.

Clinical examination revealed a missing upper right incisor, reduced keratinized tissue at the ridge crest and bone deficiency in the labial region (Fig. 1). For a complete evaluation of the anatomy of the anterior maxilla and finalization of the treatment plan, cone-beam computed tomography (CBCT) analysis was performed. CBCT revealed that the buccal bone thickness was significantly reduced, and the height, width and length of the available bone at the edentulous site were 17.91 mm, 2.94 mm and 9.70 mm, respectively (Fig. 2). There is a clear indication for reconstructing the #11 alveolar ridge width to place implants of adequate dimensions. Importantly, CBCT also revealed an impacted third molar with buccal cortical bone in the right ramus of the mandible (Fig. 2). On the basis of the clinical examinations and CBCT results as well as the patient’s expectations, an integrated treatment plan was developed to simultaneously remove the right impacted third molar and harvest the mandibular ramus block graft for horizontal ridge augmentation of the #11 alveolar defects.

Fig. 1

Patient’s pretreatment intraoral photograph

Fig. 2

Patient pretreatment CBCT examination. (A and B) Patient pretreatment CBCT examination of the edentulous site. (C and D) Patient’s pretreatment CBCT examination of the impacted third molar on the right side of the mandible

Preoperatively, the patient was administered 2 mg of dexamethasone. All operations were performed with informed consent and under painless conditions. The first step involves exposing the edentulous site via a horizontal incision along the gingival margin and vertical relieving incisions extending distally from the mesial aspect of tooth #21 to the distal aspect of tooth #12 (Fig. 3A). The cortex at the recipient site is prepared with ultrasonic osteotomy to improve graft incorporation. Once the recipient site was ready, a full-thickness buccal triangular flap with a distal buccal release was used to expose the impacted third molar and the mandibular ramus. After tooth #48 was extracted, ultrasonic osteotomy was used in the ramus to harvest the graft. The graft was slightly trimmed for optimal adaptation, and a titanium fixation screw was used to fix the graft to the recipient site. Additionally, bone powder combined with autogenous bone debris was used to fill gaps between the block graft and the recipient bone to reduce surface resorption of the graft. After that, a resorbable collagen membrane was placed over the entire grafted area to enhance outcomes. The wound was closed via horizontal periosteal releasing incisions without any tension (Fig. 3).

Fig. 3

The autogenous bone graft surgical procedure. (A) The recipient site was prepared. (B) Harvesting the bone graft. (C) Bone graft fixed to the recipient site. (D) Bone powder and resorbable collagen membrane were used to cover the graft, and the wound was closed

Amoxicillin (3 × 1000 mg) for 7 days, dexamethasone (2 mg) for 3 days, and analgesics, as needed, were given to the patients after surgery. The patient was instructed to avoid coughing and sneezing, which might increase the intraoral pressure and increase the risk of further adverse events.

Three days after surgery, the patient complained of pain and swelling beginning on the second day after surgery. Clinical examination revealed that the patient’s face was asymmetrical, with a right-sided face and lip swelling, along with mild trismus; palpation revealed crepitus, and the patient felt pain; none of the donor sites or recipient sites experienced wound dehiscence or infection; and there were no breathing difficulties, dysphonia, or dysphagia (Fig. 4). CBCT revealed subcutaneous air densities in the subcutaneous tissue of the recipient site (maxillary anterior region) (Fig. 5A-C) and the donor site (right mandibular ramus) (Fig. 5G-I), further supporting the diagnosis of subcutaneous emphysema after the dental surgical procedure. It is worth noting that the subcutaneous emphysema in the anterior region was located predominantly near the right maxillary lateral incisor, which also corresponded to the area with the largest horizontal bone loss. In this region, the autogenous bone block placement was less tightly fitted, potentially increasing the presence of a potential gap (Fig. 5A-C). Moreover, CBCT also revealed that the graft was closely associated with the bone of the recipient site (Fig. 5D-F). Without signs or symptoms of serious complications, we instructed the patient to continue taking 3 × 1000 mg amoxicillin for 7 days to prevent infection and seek medical attention promptly if symptoms worsened [10, 16]. Ten days after surgery, the patient’s pain and swelling improved, and the sutures were removed (Fig. 6). Six months later, good incorporation of the bone graft and minimal resorption around the screw were observed via CBCT examination (Fig. 7). Eight months following the bone grafting procedure, the patient underwent an implant surgery at the grafted site. To prevent the recurrence of SE, adjustments were made to the surgical approach based on prior experiences. The flap design was modified to reduce its extent, with a trapezoidal incision limited to the mesial half of tooth #21 and the mesial half of tooth #12(Figure 7D). The surgical duration was also shortened, and no air-driven instruments were used. Postoperative care instructions were reinforced to prevent actions that could increase air pressure in the surgical area. No signs of SE were observed postoperatively, and the patient’s recovery proceeded smoothly (Fig. 7E-G).

Fig. 4

Patient condition 3 days postoperatively. (A) Postoperative facial photograph. (B) Postoperative intraoral photograph

Fig. 5

Postoperative CBCT after onlay bone grafting. (A-C) Subcutaneous air densities are present in the upper right incisor region near the right maxillary lateral incisor. (D-F) The graft and bone were closely connected. (G-I) Subcutaneous air densities are present in the right submandibular region

Fig. 6

Patient condition 10 days after onlay bone grafting. (A) Postoperative facial photograph. (B) Postoperative intraoral photograph

Fig. 7

(A-C) CBCT at 6 months after onlay bone grafting. (D) Flap Design for implant surgery at the grafted site. (E-F) Postoperative CBCT after implant surgery

Discussion

This case report presents a rare instance of s SE occurring simultaneously at both the donor and recipient sites during autogenous bone grafting, an unusual complication in existing literature. Previous reports have primarily described SE in association with maxillary sinus elevation, making this the first documented case linked to an onlay bone graft procedure [2]. The involvement of two anatomically distinct regions highlights the importance of exploring potential contributing factors, including surgical techniques, equipment used, and patient-specific conditions. We discuss the etiology and mechanisms of SE in the context of oral surgery, emphasize its occurrence in autogenous bone grafting in this case report, and provide guidance on its diagnosis, management, and prevention.

Etiology

In dental surgery, particularly procedures involving significant manipulation of both soft and hard tissues, SE may occur due to a combination of factors: In this case, the occurrence of SE at both the donor and recipient sites suggests a multifactorial origin, highlighting the need to analyze common etiological pathways in oral surgical procedures and their relevance to this unique presentation.

• Instrument Use and Air Pressure: SE in dental surgery often arises from the use of air-driven tools [3]. During procedures such as tooth extraction, onlay bone grafting, and sinus floor elevation, air may enter through the wound into subcutaneous spaces, particularly when high-speed air-turbine handpieces or air syringes are used. In certain bone augmentation procedures, the majority, as in this case, utilize ultrasonic osteotomy, which reduce the possibility of air entry into the surgical site. Previous case reports have indicated that ultrasonic devices, though less likely than air-driven devices, can still introduce air into surgical spaces, leading to SE [17,18,19].

• Surgical technique and flap management: Repeated movement of a tooth or a graft during dental surgical procedures can push air into adjacent tissues. In this case, owing to the patient’s dense bone, repeated elevation of the impacted tooth during extraction may increase the risk of air entering the bone donor site. Excessive force during elevation may create a deep pathway, especially in tooth extraction and sinus floor elevation, allowing air to travel through the damaged area into surrounding spaces and increasing SE risk. Additionally, prolonged surgical time, excessive soft tissue incisions, and extensive flap elevation can create potential pathways for air entry. Repeated retraction or slipping of buccal flaps during surgery can also trap air under the tissue, leading to SE.

• Patient oral activities: Postoperative activities such as coughing, rinsing, swallowing, spitting, and speaking can lead to air being forced into deep wound areas. These actions change the intraoral pressure and allow air to infiltrate the subcutaneous tissues through any exposed wound or flap. Although the patient was advised to avoid actions such as coughing and nose blowing in this case, the graft recipient site was #11, where speaking can easily impact the wound, potentially allowing air to enter the wound. Notably, patients are often advised to use a chlorhexidine mouthwash to prevent oral infections [20]. However, when prescribing mouthwash, clinicians should consider the possibility of subcutaneous emphysema and advise patients to rinse gently. Further research is needed to determine whether this increases the risk of subcutaneous emphysema.

• Potential gap at the wound site: Unlike other cases of SE, autogenous bone grafting procedures can create multiple potential spaces where air may become entrapped. In the recipient site, these include areas where cortical bone is trimmed, gaps between the bone graft and the defect, separations between the collagen membrane and underlying bone, and spaces between the soft tissue flap and the periosteum or bone. In the donor site, harvesting the graft from the lateral ramus, creating a postoperative gap at the wound site. In this case, the donor site differed from typical bone augmentation procedures as it involved the extraction of an impacted wisdom tooth. This extraction resulted in a larger mandibular bone defect, the loss of negative pressure around the tooth and alveolar socket can increase susceptibility to air entry, especially if periodontal tissues are loosened or detached [3](Fig. 8). Bone augmentation procedures involve complex surgical techniques and the manipulation of anatomical structures in both donor and recipient sites. This complexity creates more potential spaces for air entrapment compared to other oral surgeries, increasing the risk of SE.

• Local Anesthesia Techniques: Accidental injection of air into subcutaneous tissues during local anesthesia administration can introduce gas directly into the site under anesthesia [3].

Fig. 8

Potential gap in the recipient site and the donor site in autogenous bone grafting procedure

Diagnosis

SE typically presents with rapid-onset swelling immediately after surgery or within hours after surgery. Most patients report moderate facial or cervical local swelling, a “crackling” sensation on palpation, and discomfort. However, in some cases, the spread of larger volumes of air into deeper tissue spaces can lead to serious complications. If air extends to the sublingual and submandibular spaces, it may compress the airway, causing dysphagia, dysphonia, or respiratory difficulty [16, 21, 22]. Therefore, SE is an uncommon but clinically significant complication in bone augmentation procedures, with particularly limited reporting in cases involving autogenous bone grafting [2].

The clinical significance of this case lies in the challenges of distinguishing SE from more common postoperative complications, such as swelling and hematoma. In the anterior esthetic zone, symptoms of SE, including rapid swelling and crepitus, may closely mimic the typical postoperative edema or localized hematoma. Without a high index of suspicion, SE could be easily misdiagnosed, leading to delayed or inappropriate management. Early identification and differentiation are critical, as SE, if left untreated, can progress and result in severe complications such as mediastinal emphysema or airway compromise. The diagnosis of SE in surgical cases relies on palpation to detect crepitus, which is indicative of gas in the tissue, and imaging to confirm its extent. CBCT is the preferred imaging modality for accurately determining the scope of SE. Some researchers suggest that CBCT can be used to estimate the gas volume in patients with subcutaneous emphysema, allowing for better assessment of the patient’s condition [6]. Differential diagnosis must consider other conditions presenting with similar symptoms, such as allergic reactions, hematoma, and infections such as cellulitis. To aid in clinical practice, this report includes a differential diagnosis table, highlighting the distinguishing features of SE, swelling, and hematoma (Table 1).

Table 1 Differential diagnosis of subcutaneous emphysema [4, 7, 23, 24]

Prevention

• Surgical Technique: Employ ultrasonic devices for bone removal to minimize air entry instead of high-speed air-turbine handpieces.

• Flap Design and Handling: Ensure careful handling of mucosal flaps to reduce potential gaps through which air could enter.

• Gentle Instrumentation: When anesthesia is administered or syringes are used during bone augmentation, gentle pressure is applied to prevent air injection into subcutaneous tissues.

• Minimizing potential gaps: At the donor site, collagen-based materials, such as collagen sponges or bone collagen, can be used to fill the voids left after bone harvesting or tooth extraction. This not only aids in tissue healing but also reduces the likelihood of air entry. At the recipient site, CBCT imaging can be utilized to design a surgical guide, facilitating precise bone block shaping and ensuring a better fit with the defect area. Additionally, gaps can be filled with autogenous bone powder or other graft materials to enhance stability and minimize potential air pockets.

• Postoperative Care: Patients should be educated to avoid forceful actions, such as blowing their nose, sneezing with their mouth closed, or vigorously rinsing, which may increase pressure and promote air entry.

Management

In most SE cases following oral surgery, the condition is self-limiting and resolves within 3–10 days as the air gradually dissipates. The management of SE relies on a combination of supportive care and preventive measures. Conservative management involves monitoring for signs of progression, administering prophylactic antibiotics to prevent secondary infection, and educating patients about the expected symptoms. Severe cases, characterized by life-threatening symptoms such as rapid and extensive gas expansion occurs or acute respiratory distress, necessitate immediate hospitalization and advanced interventions, including high-flow oxygen therapy, needle decompression, or surgical drainage to prevent complications like compartment syndrome. Collaboration with respiratory specialists may be required for severe systemic involvement. Ultimately, early diagnosis, patient education, and tailored management are essential to ensuring effective treatment and minimizing risks [25].

In this case, prophylactic antibiotics and patient education played pivotal roles in mitigating risks of infection and recurrence. Notably, this case is unique in providing long-term follow-up data, a rarity in existing literature. Six months after bone augmentation, the grafted bone demonstrated stable volume and successful osseointegration.

SE is a rare but significant complication during autogenous bone grafting procedures. Understanding its prevention, accurate diagnosis, and effective management is crucial for optimizing patient outcomes. The following framework outlines key strategies to address SE in this context (Fig. 9).

Fig. 9

Framework for prevention, diagnosis, and management of SE during Autogenous Bone Grafting

This case is the first reported instance of SE associated with an onlay bone graft, with the simultaneous occurrence of SE at both the recipient site and donor sites, setting it apart from prior cases. Six months after the bone grafting procedure, the grafted bone remained stable with successful osseointegration, demonstrating no adverse effects from SE. Additionally, no recurrence of SE was observed during the subsequent implant placement, further validating the effectiveness of timely management and structured postoperative care. Preventive measures implemented during the procedure included reducing the flap elevation range, minimizing surgical time, employing gentle handling techniques, and reinforcing postoperative guidance for the patient.

Conclusion

The risk of SE is increased during bone graft harvesting and augmentation because of increased tissue handling and the creation of potential spaces. This case report significantly enhances the understanding of SE in dental procedures, particularly following onlay bone grafting. By documenting the simultaneous occurrence of SE at both donor and recipient sites, it underscores the multifactorial etiology of this rare complication. Dental professionals should be aware of the iatrogenic risk of SE associated with autogenous bone grafting to minimize intraoperative and postoperative occurrence. Early, accurate diagnosis and appropriate management are essential to prevent severe or potentially life-threatening complications, facilitating a smoother recovery. Proper surgical techniques, careful handling of instruments, and vigilant postoperative monitoring are essential for preventing SE. Enhanced awareness among dental professionals, along with preventive measures tailored to bone augmentation, can reduce the incidence of iatrogenic SE and promote safer patient outcomes. This report contributes to the limited literature on SE in dental surgery, offering guidance for the prevention and management of similar cases in clinical practice.