Reconstruction of mandibular “chop-off” defects resulting from gunshot injuries at University Maiduguri Teaching Hospital, Nigeria: A retrospective study

Abstract

Introduction: Mandibular injuries resulting from high-velocity projectiles often lead to extensive destruction of hard and soft tissues, a phenomenon typically described as “chop-off” wounds. These injuries pose unique challenges in presentation, emergency management, and definitive treatment due to complex anatomy and mechanisms. This study evaluates our clinical experience in managing such injuries at the University of Maiduguri Teaching Hospital (UMTH) Oral and Maxillofacial Surgery Department, which functions within a resource-limited setting.

Method: This retrospective study was a case series conducted at UMTH Borno State, during the peak of Boko Haram insurgency from January 2016 to January 2022. The sample included patients with mandibular “chopped off” gunshot injuries, defined as severe lower jaw tissue damage with loss of mandibular bone continuity. Patient files were reviewed for demographic data, wound characteristics, emergency airway management, diagnostic findings, treatment types, follow-up duration, and complications. Data were analyzed using the statistical software SPSS version 20.

Results: From January 2016 to January 1, 2022, 117 patients with Gunshot Injuries (GSI) were treated, with 13 sustaining “chop-off” gunshot injuries. The final analysis included the 12 survivors out of 13 initial patients. The mean defect size widest diameter was 4.7 ± 1.1 cm (range 3-6 cm). Seven patients (58.3%) had complete ‘chop-off’ injuries, while five (41.7%) had incomplete injuries. The tongue was involved in two patients (16.6%) with avulsion of the anterior one-third. Five patients (41.7%) required tongue traction for immediate airway management, and seven (58.3%) underwent tracheostomy. Reconstruction plate extrusion with mucosa breakdown occurred in two patients (16.7%), and four (33.3%) had donor site complications.

Conclusion: The reconstruction of severe mandibular gunshot injuries is complex. However, regional flaps combined with skeletal stabilization can yield acceptable results in the absence of free tissue transfer.

Keywords: mandibular reconstruction, chop-off injury, gunshot injuries, resource-limited setting.

Introduction

Severe mandibular injuries resulting from high energy/velocity gunshot to the face often lead to substantial loss of both hard and soft tissues.^[1,2] The term “chop off” describes these injuries to the mandible due to their distinct characteristic presentation.^[2] The mechanism of injury involves a perpendicular transection of tissues across the mandible with the severity of damage determined by the amount of kinetic energy transferred.^[2] These injuries are life-threatening and when seen at presentation the Advanced Trauma Life Support protocol must be followed starting with the primary survey: Catastrophic bleeding, Airway, Breathing, Circulation, and Disability (CABCD).^[2,5] They present challenges  for emergency care, and definitive treatment due to the mechanism of injury and the complex anatomy and function of the affected structures. Shakur et al. proposed incorporating chop-off injury into the classification of ballistic wounds, which currently includes penetration, perforation, and avulsion. ^[2,3]

Management of mandibular chop-off injuries requires a multidisciplinary approach to treatment involving a staged approach, beginning with initial stabilization and debridement, followed by careful planning and execution of reconstructive procedures to restore both form and function.^[2] The extensive tissue loss often necessitates complex reconstruction techniques in highly specialized centres.^[2,3] 

This study looks at our clinical experience at the Oral and Maxillofacial Surgery Department of the University of Maiduguri Teaching Hospital, a resource-constrained setting in the management of mandibular chop-off gunshot injuries after primary stabilization including antibiotic cover and tetanus prophylaxis by doctors in conflict zones of the state. It highlights the challenges and outcomes of surgical interventions employed during this period of insurgency in the state.

Method

This retrospective study was carried out at the Department of Oral and Maxillofacial Surgery, University of Maiduguri Teaching Hospital (UMTH), Borno State, the epicentre of the Boko Haram insurgency period in northeastern Nigeria, over  six years from January 2016 to January 2022. The sample was chosen from the hospital case records of patients with mandibular chop-off gunshot injuries, who presented to this tertiary hospital.

Mandibular chop-off injury was defined as massive lower jaw tissue injuries with some loss of hard and soft tissue mandibular bone continuity that had avulsed or chopped-off of the mandible. Usually, this involves a significant amount of avulsed mandibular bone, from the parasymphyseal or body regions. It may extend either unilaterally or bilaterally up to the angle or ramus level with varying degrees of soft and hard tissue preservation. Chop-off was categorized as incomplete, where teeth were present and can be used to stabilize the mandible or complete, when no teeth are left, and all are part of the avulsed mandible.

Patients’ files were reviewed for demographic characteristics, wound characteristics, emergency airway management, diagnostic findings, type of treatment provided, follow-up duration, and complications. Ethical approval for the study was waived for this retrospective study. However, written consent for the use of clinical photographs was obtained from the patients whose images were featured.

Data were entered in Microsoft Excel (20 version) and cleaned of errors. Statistical analyses were performed using statistical software SPSS version 20.0 for Windows (SPSS Inc.).

Results

Between January 2016 and January 1, 2022, 117 Gunshot Injury (GSI) patients received treatment, among whom 13 had sustained ‘chop-off’ gunshot injuries. Of these, 12 patients were included in the final analysis, as one did not survive the injuries sustained on the day of emergency presentation.

The mean defect size was 4.7 ± 1.1 cm, with a 3 to 6 cm range. Seven patients (58.3%) sustained a complete ‘chop-off’ injury, while five (41.7%) experienced an incomplete ‘chop-off’ injury. We recorded tongue involvement in two patients (16.6%) with avulsion of the anterior one-third of the tongue.

Concerning immediate airway management, five patients (41.7%) required tongue traction to maintain airway patency, and seven patients (58.3%) underwent tracheostomy. All 12 patients (100%) had conservative serial debridement and wound dressing . Additionally, six patients (50%) received initial fracture stabilization. All patients (100%) underwent delayed reconstruction of hard and soft tissues. Regarding subsequent interventions, six patients (50%) received residual deformity reconstruction and oral rehabilitation to address remaining deformities and enhance oral function. Finally, three patients (25%) participated in physical therapy post-surgery for recovery, and two patients (16.7%) required psychiatric assistance to manage the psychological impact of their injuries (Table 1).

Table 1. Wound characteristics, treatment, and complications N=12

Four patients (33.3%) experienced partial flap necrosis, necessitating revision surgery.  No patient suffered from total flap necrosis. Ten patients (83.3%) had microstomia. Additionally, three patients (25%) developed infections that required further surgical intervention. Dehiscence occurred in four patients (33.3%), and an equal number of patients encountered issues with saliva drooling and oral incompetence. Hardware extrusion was noted in two patients (16.7%), and four patients (33.3%) experienced donor site complications (Table 1).

Discussion

In this study, the authors observed delayed reconstruction across all participants. Mandibular GSI studies from UK and US mostly report securing the airway and reconstructing the mandible as the first stage.^[7,8] GSI involves significant tissue destruction, characterized by extensive bone loss, soft tissue avulsion, and contamination from foreign materials. Such wounds in the craniofacial region necessitate complex, multi-stage surgical interventions, including initial stabilization and subsequent reconstruction with vascularized or non-vascularized tissue transfer.^[4,5] Additionally, infection control, wound healing, maintaining airway patency, and expertise are critical variables that can significantly affect outcomes, especially when immediate or delayed reconstruction options are considered.^[13]

For mandibular reconstruction, we used a reconstruction plate for all patients to stabilize the segments of the mandible, which is the commonest used.  However, the use of Kirshner wires has been reported.^[2,4] The deltopectoral flap was used in almost all cases. (Figures 1 and 2)

Figure 1. Patient with chop-off mandibular GSI with spared tongue before and after reconstruction with a deltopectoral flap. CT scan shows mandibular bone loss. (Credit- Mohammed Adam Sheikh Abdullahi)

Figure 2. Patient with chop-off mandibular GSI with sparing of the tongue before and after reconstruction with deltopectoral flap. (Credit- Mohammed Adam Sheikh Abdullahi)

The deltopectoral flap has been traditionally utilized for reconstruction in the head and neck region.^[9] Although its popularity has waned in favour of free flaps it remains a reliable option due to its technical simplicity and consistent vascular supply.^[9,10] This flap represents a valuable choice for reconstructing gunshot wounds, backed by a well-documented complex head and neck reconstructions.^[7,9,10] 

Microvascular surgery has been shown to significantly improve mandibular reconstruction, enabling the transplantation of vascularized bone and soft tissue with high success rates.^[11] This treatment modality is commonly regarded as the preferred approach when available skills and resources  permit.^[11] Four of the patients had partial flap necrosis and required surgical intervention. Two cases had a reconstruction plate removed. In cases where inadequate bone or soft tissue repair following a chop-off occurs, the patient may exhibit a complication resembling the “Andy Gump deformity,” characterised by an absent chin, a retracted lower lip, and a significantly retrognathic lower jaw.^[12] This complication has not been extensively studied and  needs further research. 

In this study, the involvement of the tongue in chop-off wounds was observed in two patients (16.6%), with the anterior one-third being completely avulsed (Figure 3).  However, a study by Shuker et al.^[2] reported that the tongue remained intact in all their cases despite significant mandibular soft tissue loss. They attributed this occurrence to the dislodgement of the weak genioglossus muscle origin and its insertion on the hyoid bone. This dislodgement results from maximum stretching, which can occur without severing the muscle’s bulk. Consequently, the tongue’s primary mass can remain intact despite significant injury.^[2] However, while this mechanism is plausible, it is not universally applicable, as evidenced by our findings. 

Figure 3. Patient with chop-off mandibular GSI with avulsed anterior one-third of the tongue before and after reconstruction with a deltopectoral flap

In our study, 58.3% (n=7) of patients had a tracheostomy, while the remaining patients had tongue traction sutures placed as airway management prior to definitive treatment. Tracheostomy has been the mainstay of airway management in other mandibular chop-off GSI studies.^[2] Airway management is a lifesaving procedure in mandibular chop-off wounds, given that the detachment of the tongue musculature can cause the tongue to fall back, occluding the pharynx and leading to airway obstruction.^[2,5] Tracheostomy represents a frequently performed intervention for airway stabilization in patients presenting with multisystem trauma, particularly those afflicted by craniomaxillofacial injuries.^[5,6] It is acknowledged as a safe and effective method for managing airway complications in critical clinical scenarios.^[6] 

Conclusion

The main learning point from this study is that there is a critical need for comprehensive initial management and a tailored surgical plan that considers both patient and environment-specific factors such as available skill, manpower and resources. A multidisciplinary approach is essential to achieving successful outcomes in mandibular reconstruction following “chopped off” injuries of the mandible due to gunshot injuries, especially in resource constrained settings.

References

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10. Manfro G, Freiria De Oliveira GA, Fechine Feitosa RG. Use of the deltopectoral flap for reconstruction of a complex cervical defect: case report. Journal of Dermatology & Cosmetology. 2022 Jul 13;6(3):50–1.
11. Matros E, Schwarz GS, Disa JJ, Mehrara BJ, Cordeiro PG, Hu QY. Indications and Outcomes for Mandibular Reconstruction Using Sequential Bilateral Fibula Flaps. Plastic and Reconstructive Surgery. 2010 Nov 1;126(5):1539–47.
12. Lilly GL, Petrisor D, Wax MK. Mandibular rehabilitation: From the Andy Gump deformity to jaw-in-a-day. Laryngoscope Investigative Otolaryngology. 2021 May 29;6(4):708–20.

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