The Reconstruction of Mandible Defects in War Injuries: Systematic Review and Meta-Analysis

Abstract

Study Design: Systematic Review and Meta-Analysis. Objective: There has been an increasing trend in maxillofacial injuries associated with combat trauma. Within the maxillofacial complex, the mandible is the most likely structure to be damaged during combat. The structural deficits as a result can be reconstructed with many options. These include vascularised bone grafts (VBGs), non-vascularised bone grafts (NVBGs), alloplastic implants, reconstruction bars and distraction osteogenesis. This study aimed to determine the common modality and efficacy of mandibular reconstruction in combat trauma-related defects. Methods: A literature search was conducted on Pubmed, Prospero, Dynamed, DARE, EMBASE, COCHRANE and BMJ databases. Results: A total of six articles met the inclusion criteria identifying 165 patients requiring mandibular reconstruction. Nonvascularised iliac bone graft (n = 137) was the most common method followed by ileac crest bone chips harvest using Dacron urethran osteomesh tray (n = 24) and frontoparietal grafts (n = 4). Meta-analysis of five out of six trials demonstrated an overall success rate of 85% (95% CI 79–90; I² = 59%). A total of 13% (n = 22) of reconstructions failed either completely or partially and 21% (n = 34) of patients suffered postoperative complications. Conclusions: NVBGs are a practical, cost-effective and favourable method of war zone management of mandibular defects with success rates comparable to those reported in the civilian literature. However, general trauma principles take precedence to rule out life-threatening injuries. Due consideration of patient factors, surgical factors, and available resources are required in the first-line management of combat-related mandibular defects.

Background

Mandibular defects have multifactorial aetiology. This can include trauma, resections for benign or malignant lesions, osteonecrosis and inflammatory disease [1]. There has been an increasing trend in maxillofacial injuries associated with combat [2]. Projectiles used in most combats and war zone settings often travel at over 2000–2500 feet per second and are regarded as high-velocity weapons. Consequently, extensive destruction and avulsion of soft tissue and bone can occur [3]. Combat injuries, therefore, present unique challenges to the maxillofacial surgeon to restore form and function [4].

Significant injuries that were once found to be unsurvivable are now making their way to combat hospitals due to improvements in body armour and damage control surgery [4].

Combat wounds are always contaminated and require thorough debridement [5]. The principles of good wound management for combat injuries include adequate wound excision and debridement of necrotic and contaminated tissues followed by haemostasis of bleeding tissues. Wounds are typically left open to allow for the drainage of exudate with delayed closure being adopted. Medical management is equally important with the use of tetanus vaccinations, antibiotics, analgesia and nutrition [6].

The mandible is the most likely structure of the maxillofacial complex to be injured during combat-related trauma [7]. The mandible provides a scaffold for key anatomical structures including the muscles of mastication, the tongue, the lower dentition and the floor of the oral cavity. It, therefore, plays a vital role in mastication, airway protection, articulation and deglutition. Facial aesthetics particularly the frontal and side view projections of the lower third face of the face and facial width are further dictated by the mandible [1]. There are various options available for the reconstruction of the mandible, although in combat injuries, the pattern of injury can vary compared to civilian trauma and therefore different modes of reconstruction may be applied. These include vascularised bone grafts (VBG), non-vascularised grafts (NVBG), alloplastic implants, reconstruction bars and distraction osteogenesis. Autogenous bone grafts, either vascularised or not are mostly used in reconstructive surgery of the mandible [8].

Aims

The primary aim of this study was to determine the common modality and efficacy of mandibular reconstruction in combat trauma-related defects.

Methodology

Literature Search

A literature search was conducted in November 2022 by two independent reviewers on Pubmed, Dynamed, DARE, EMBASE, Cochrane and British Medical Journal (BMJ) electronic databases for articles published between 1980 and 2022. The following MESH terms were used to retrieve the relevant articles: ‘war’, ‘reconstruction’, ‘mandible’, ‘mandibular’, ‘combat injuries’, ‘maxillofacial injuries’, ‘facial injuries’, ‘blast’, ‘blast injury’, ‘armed forces’, ‘ battle’, ‘battle injuries’ and ‘combat’. A full search strategy can be seen in

Table 1. MESH Search Strategy.

. A grey literature search was conducted looking at conference abstracts for the British Trauma Society, American Association of Trauma, the British Association of Plastic, Reconstructive and Aesthetics Surgeons and the British Association of Oral and Maxillofacial Surgeons.

Only original research studies published between 1980 and 2022 were considered. The following study types were reviewed: randomised control trials, prospective cohort studies, retrospective cohort studies, case-control studies and case series. Two independent reviewers screened titles and abstracts for eligibility and inclusion. The same reviewers then screened relevant full papers before inclusion.

Inclusion

For this article, all studies focusing on mandibular trauma with continuity defects requiring reconstruction secondary to combat/war injuries were included. Combatants and civilian combat injuries were included. All ages were included. Both vascularised and non-vascularised forms of reconstruction were included. Where maxillary and mandibular injuries were reported in a pooled format, these cases were included within the analysis.

Exclusion

For this article, studies focusing exclusively on the reconstruction of bony defects of the face not involving the mandible, facial transplantation and those where the full text was not available or not available in English were all excluded from the analysis. Those injuries focusing on noncombat-related trauma were also excluded.

Data Extraction

The data was extracted onto a standardised date extraction template relating to population, intervention, comparison and outcome (PICO). The population studied included patients with mandibular defects secondary to combatrelated trauma requiring mandibular reconstruction. The intervention used was non-vascularised bone grafting. The comparator was other forms of mandibular reconstruction primarily VBG. The success rate of intervention was the primary outcome and the secondary outcome included total complications. In addition, relevant articles were further screened to extract further outcomes including types of injuries, location of surgery, type of reconstruction, timing to mandibular reconstruction, number of debridements before reconstruction and antibiotic prophylaxis. Failure of reconstruction was defined as total or partial graft loss or those requiring a second procedure for reconstruction (excluding staged surgery).

Risk of Bias and Quality Assessment

Each study was reviewed individually for risk of bias associated with the selection, comparability and outcome reporting using the Newcastle Ottawa Tool for cohort studies. The results from the Newcastle Ottawa Tool were translated into the Agency for Healthcare Research and Quality (AHRQ) scores [9,10]. Of the studies included in this paper, five were of poor quality according to the AHRQ standards (

Table 2. Study Characteristics.

) with one study being of good quality. Five studies had evidence of selection and comparability bias. Three studies demonstrated evidence of outcome bias. The poor quality of evidence included is a limitation of this paper.

Statistical Analysis

Pooled proportional prevalence estimates and the corresponding 95% confidence intervals were calculated for outcomes of mandibular reconstruction success rate and total complications after reconstruction using both random and fixed models. Studies which did not specify values for outcomes of reconstruction success rate and total complications after reconstruction were not included in the proportional meta-analysis (n = 1). All statistical analysis was performed using R (version 4.2.2), package meta-version 6.0-0. To assess heterogeneity between the included studies, we used R (version 4.2.2), package meta-version 6.0-0 to determine Cochran’s Q value and I² statistic (in percentage).

Ethical Approval

The online Health Research Authority Medical Research Council (United Kingdom) tool was completed to assess whether ethical approval was required for this study. This demonstrated that ethical approval was not required.

Results

Literature Search

The number of studies screened, assessed for eligibility and included in the review, with reasons for exclusion are presented in the PRISMA flow diagram (Figure 1). Using the key search terms described earlier yielded a total of 6499 results across Pubmed, Dynamed, DARE, Cochrane and grey literature searches. Articles were initially reviewed by two independent reviewers and included/excluded based on the title and abstract. Next, the full text was reviewed for 142 articles. Reasons for the exclusion of full text included studies focusing on reconstructing head and neck defects aside from the mandible and those unavailable in English. A total of six articles fulfilled the inclusion criteria. Two articles had pooled their analysis for both mandibular and maxillary injuries and so were unable to isolate individual injuries [12,13]. The study characteristics can be seen in Table 2.

A total of 165 (1–91) patients were included with injuries requiring reconstruction of the mandible; countries of injury included Iran (n = 2), Iraq (n = 3) and Israel (n = 1). The cause of injury included gunshot wounds (n = 32), blast (n = 20), shrapnel (n = 3) and unable to extract injury data (n = 110). The average age of patients included was 34.4 (1–70). The size of mandibular defects was reported by two studies, and this was found to be 4–7 cm in 17 patients, >5 cm in 19 patients and <5 cm in 16 patients [1,15]. Time to reconstruction was reported in three studies and ranged from 20–3814 days [1,3,15]. Due to a lack of reporting individual values, a mean/median was not possible to calculate. The number of pre-reconstruction debridements was reported by no studies.

Fracture management of the mandible included steel wires (n = 93), maxillomandibular fixation (n = 11), locking plates (n = 27), non-locking plates (n = 6), mini plates (n = 2), ORIF (n = 5), screws (n = 1) and no fixation (n = 4).

Type of Mandibular Reconstruction Used

Non-vascularised iliac bone grafts were used in (n = 133), iliac crest bone chips harvesting using Dacron urethan osteomesh tray (n = 24). One patient required secondary reconstruction with a microvascular fibular flap following failed bone graft. Frontoparietal grafts were used in (n = 4); it was not documented whether these were pedicled and so it is not possible to determine whether these are vascularised or not vascularised bone grafts [13].

A total of 13% (n = 22) of mandibular reconstructions had either failed partly or completely within the studies. Moreover, 21% (n = 34) of patients suffered from postoperative complications.

Meta-Analysis

The overall proportion for the success rates of the assessed mandibular reconstruction using non-vascularised reconstructive methods was 85% (95% CI 79–90; I² = 59%; Figure 2). This suggests that overall, the current mandibular reconstruction methods from the analysed studies are likely to be successful for 85% of the population who suffer from conflict-related mandibular trauma.

Risk of Bias and Quality Assessment

Of the studies included in this paper, five were of poor quality according to the AHRQ standards (

Table 3. Study Quality Assessment Using Newcastle Ottawa Tool and AHRQ Rating.

) with one study being of good quality. Five studies had evidence of selection and comparability bias. Three studies demonstrated evidence of outcome bias. The poor quality of evidence included is a limitation of this paper.

Discussion

Mandibular reconstruction can be carried out immediately following trauma or as a delayed procedure. Injuries in combat are often seen as high risk for infection given the multitude of environmental pathogens present. Within this study, most patients (83%) underwent reconstruction using iliac bone grafts with a pooled overall reconstructive success rate of 85%.

Wounds relating to combat are grossly contaminated, and therefore, it is always necessary to effectively debride and decontaminate wounds before any reconstructive operative procedures [5,6,18]. Effective debridement is required for combat-related maxillofacial wounds before considering reconstruction; within this study, all studies did not comment on the time to first debridement nor the number of debridements which are both pivotal aspects of management [1,3,11,12,13,14].

Types of Flaps Used

Effective reconstruction of segmental mandibular defects is important in re-establishing function and aesthetics. The type of reconstruction chosen would depend on the characteristics of the defect including length, soft tissue status and shape.

In civilian trauma, the use of VBGs is widely favoured as the optimal method of reconstruction offering good restoration of oral function, cosmetic contour and quality of life for larger defects and composite hard/soft tissue defects [19,20,21,22,23,24]. NVBGs are advised for shorter defects <6 cm; however, in combat wounds, the ability to provide vascular grafts is not always possible due to scarce resources and equipment including monitoring and microscopes [16]. The size of the defects in the studies examined were from 4 cm and above, although this was not extensively reported. Hence, VBG could potentially be performed although this may not be practical in austere settings as they are time-consuming, associated with donor site morbidity, and require longer hospital stays and advanced equipment which is often not available in the combat trauma setting [15,19,25]. This may have all contributed to the reason only studies using NVBG were found within the existing literature for reconstructing combat-related mandibular defects.

In the studies reviewed, the graft of choice was NVBG iliac crest. The ileum is thought to be the most successful non-vascularised grafts in mandibular reconstruction as it contains a large amount of bone and a high concentration of osteocompetent cells for transfer [19]. The use of NVBG in mandibular repair involves less blood loss and shorter operating times which is often ideal for combat injuries [25].

Time From Injury to Reconstruction

The time from injury to reconstruction varied across the studies, from 20 to 3814 days. This is currently a topic which remains widely debated with no guidelines in place to suggest the optimum time for mandibular reconstruction. Studies on civilian mandibular reconstruction showed that infection rates are not thought to increase when delaying reconstruction by more than 72 hours [26,27].

It is important to note that in a combat setting, delayed reconstruction is inevitable due to the level of contamination of the wounds; hence, priorities include wound optimisation and debridement rather than rushing to reconstruction in the first instance [6]. In any case, management of life-threatening injuries takes precedence followed by limb salvage, sight salvage and visceral preserving interventions. Mandibular reconstruction should only occur after this initial critical stabilisation phase [28,29].

Success Rates

The overall success of mandibular reconstruction using NVBG was found to be 85%, a rate similar to that seen in civilian literature (67%–100%) [15,25,30,31,32]. The success rates seen here are lower than those seen in civilian defects repaired with vascularised fibular flaps (90%–93%) [33,34]. Although vascularised fibular flaps are not practical within the austere environment, they can be considered in patients who are stable for transfer to secondary facilities away from the combat zone. Al-Anee and Al Jarsha 2021 concluded similarly that NVBG are a good first option for the reconstruction of manbidle defects in regions where there is an absence of free flap facilities such as austere environments [17].

Limitations

All studies included within this review often focused on different aims; hence, not all studies included parameters that were of interest. The definition of reconstructive failure varied amongst the studies and there is currently no universal definition incorporated which often makes comparison difficult. The quality of the papers included in this review and the significant heterogeneity between the papers was major limitation. An additional limitation includes the fact that studies did not measure the return to work, functional abilities or need for future surgery as part of the longer-term outcomes. Future work should aim to incorporate longer-term follow-up and to assess patient outcomes, for example, functional ability, return to work and psychological well-being.

In comparison to the civilian population where the defects are primarily from the resection of tumours with resection of benign or malignant lesions, in the war zone, it is difficult to uniformly quantify exposure in a standardised way. The studies included do not provide further information on distance from the source of ballistic trauma at the time of injury. The use of body armour is assumed in the war setting but again not reported in the studies. It is therefore difficult to ascertain if there was a direct correlation between the extent of the ballistic source of trauma and the size of mandibular defects.

The defects in the combat zone are not ascribed to a formal classification system and no information was available from the studies to ascertain the pattern of mandibular defects and what was the preoperative change in facial projection, width and height and if the restoration of specific defects using NVBGs involved the restoration of the posterior ramus height. Two studies had pooled reconstruction of the maxillary and mandible regions with inability to isolate individual injuries and this is a limitation of the review.

There is a scarcity of research in the reconstruction of mandible defects in combat injuries; this may not be due to the lack of procedures performed but rather due to a lack of reporting and publishing of outcomes from the austere setting. Future work within conflict zones or conducted by armed forces should focus on reporting on outcomes to provide additional data to draw further meaningful conclusions. More robust reporting methods should be incorporated to provide higher quality research within the field.

Conclusions

NVBGs are commonly used in war zones, with success rates like those reported in the civilian literature. This procedure is likely favoured due to the reduced blood loss, the level of experience of the practitioners, the lack of microvascular equipment and the economic constraints in the cost of the equipment. The critical aspect is to ensure life-threatening injuries have been managed and the maxillofacial wounds have been adequately debrided to ensure an infection-free base for reconstruction. This by default would result in exceeding the ideal start time for the reconstruction of soft tissue as recommended in civilian trauma.