Comparative Analysis of Hybrid Arch Bars Versus Erich Arch Bars for Maxillomandibular Fixation in the Management of Mandibular Fractures—A Prospective Randomized Clinical Trial

Abstract

Introduction:

Mandibular fractures, being the most common facial fractures, involve maxillomandibular fixation (MMF) in both closed and open reduction techniques utilizing techniques like Erich arch bars, which pose risks of injuries to the surgeon and the patient. Recent advancements like Hybrid arch bars (HB), combine the advantages of arch bars and bone-supported devices, offering improved safety. This study compares outcomes between traditional Erich arch bars and SMARTLOCK HAB in MMF, addressing challenges posed by traditional methods and exploring the benefits of the recent advancement.

Materials and Methods:

This single-center, unblinded randomized clinical trial enrolled 48 patients with mandibular fractures. The primary predictor variable was the device type used. EABs were secured with circumdental wires, while HABs were secured with self-drilling locking bone screws. Outcome variables included duration of device placement, glove perforation, prick injuries, gingival and periodontal health, root perforation, bone loss, pain assessment, and device removal duration. Devices were removed after six weeks under local anesthesia.

Results:

The mean age was 29.9 ± 8.3 years, and 91.7% were male. Primary outcome, duration of device placement, was significantly shorter for HAB (17.6 ± 14 minutes) than the Erich arch bar (EAB) group (41.4 ± 34.9 minutes), with removal duration also favoring the HAB system. Surgeon-related factors, glove perforation and prick injuries, were significantly lower with the HAB group. Patient-related factors showed lower pain scores and similar complications between groups.

Conclusion:

The HAB system offers an effective alternative with superior outcomes, with easier placement and removal, reduced risk of injury, and improved patient compliance.

INTRODUCTION

The primary objective of maxillomandibular fixation (MMF) or intermaxillary fixation is to provide indirect stabilization of bony segments, playing a crucial role in managing fractures of the maxillofacial region, as well as in orthognathic and reconstructive procedures.[1] With the key requirements being the establishment of occlusion, stability, and immobilization, various methods have evolved to meet these criteria. Mandibular fractures, being the most common facial fractures, involve MMF in both closed and open reduction techniques. Traditional techniques. Additionally, their application is complex, with an added risk of prick injuries. Recent advancements, such as bone-borne devices like IMF screws, are limited in their applicability to minimally displaced or favorable fractures due to their lack of exerting a tension band effect.[2]

The Stryker SMARTLOCK HAB system, introduced in 2013, combines the advantages of arch bars and bone-supported devices. In this system, arch bars are secured using self-drilling bone-borne screws, without affecting the dentition, thereby improving safety for the surgeon[3]. This study aims to compare the surgical outcomes between traditional EABs and SMARTLOCK HABs in the treatment of mandibular fractures with maxillomandibular fixation.

MATERIALS AND METHODS

After approval from the Institutional Review Board and IHEC (536/IHEC/10-21), a prospective, non-blinded, randomized clinical trial was conducted. Patients reporting to the Department of OMFS, Chettinad Dental College and Research Institute, from January to November 2022, with maxillomandibular fractures were screened. Those requiring mandibular fracture management were included. Procedures followed the 1964 Declaration of Helsinki (revised 2013). Eligible patients were informed, and written consent to use their records for research was obtained before surgery.

Adult patients (≥18 years) with fractures of the condyle, subcondyle, ramus, angle, parasymphysis, or symphysis requiring maxillomandibular fixation with arch bars were included. Eligibility required adequate dentition for arch bar placement, availability of pre- and postoperative imaging, and capacity to provide informed consent. Patients with comminuted, infected, dentoalveolar, or pediatric fractures, previously treated mandibular fractures, associated maxillary fractures, or gunshot injuries were excluded.

Study design

This uni-center, unblinded randomized clinical trial had parallel groups with a 1:1 allocation ratio. Forty-eight patients with mandibular fractures were included. After explaining risks and benefits, participants were randomized using computer-generated block randomization into either the Erich arch bar (EAB) group or the Stryker Hybrid Arch Bar (HAB) group.

Variables

The primary predictor variable was the device type—EAB or HAB—used during open reduction and internal fixation (ORIF) of mandibular fractures. Arch bars in both groups were placed the day before surgery under local anesthesia.

EABs were secured with 24-gauge stainless steel circumdental wires from right to left first molars in both arches, typically using 20–24 wires. HABs (Smartlock Hybrid) were secured from right to left first molars, aligned at the midline, and fixed using 10–12 self-drilling locking screws (midline plus right and left quadrants). Screw positions were planned using preoperative radiographs to avoid roots and placed with spacers to protect the mucosa. In the mandibular arch, HABs were split at fracture sites to aid reduction as shown in Figure 1.

Figure 1.

A case of angle fracture of mandible. (a) Hybrid arch bar fixed to the maxillary and mandibular arches prior to ORIF of left angle fracture. (b) One week after removal of the arch bars. (c) Postoperative radio-graph showing the arch bars and screw positions

ORIF was performed using monocortical plates along Champy’s line or lag screws for oblique fractures. Peri- and postoperative antibiotics were given. Follow-ups occurred at weeks 1, 3, and 6, with devices removed at 6 weeks under local anesthesia as shown in Figure 2.

Figure 2.

A case of bilateral condylar and left parasymphysis fracture of mandible. Hybrid arch bar system was effectively applicable in spite of multiple missing teeth and facilitated accurate intraoperative reduction. (a) Intraoperative MMF of the arches. (b) Six weeks postoperative examination before removal of the device. (c) After removal of the device

Outcome variables

• Primary outcome: Total duration for arch bar placement (start to completion), measured by stopwatch.

• Secondary outcomes: Glove perforation and prick injuries (observed by an independent assessor), gingival/periodontal health (Gingival Index, Periodontal Index), root perforation and bone loss (postoperative OPG), pain during application, MMF course, and removal (VAS score), duration of removal (stopwatch), and loose hardware (wires or screws movable with minimal force). Demographics, injury mechanism, fracture type/number, and teeth in fracture line were also recorded.

Statistical analysis

Data were organized in Microsoft Excel and analyzed with IBM SPSS Statistics v23. Descriptive statistics (frequency, percentage for categorical variables; mean ± SD for continuous variables) were used. Mann–Whitney U test assessed differences in independent groups. For categorical data with expected cell frequency <5 in 2 × 2 tables, Fisher’s exact test was applied. A P value <0.05 was considered statistically significant.

RESULT

Of 71 screened mandibular fracture patients, 48 were enrolled; 24 each randomized to the EAB and HAB groups, with no loss to follow-up. Mean age was 29.9 ± 8.3 years; 91.7% (n = 44) were male. Demographic and injury variables were similar between groups.

Placement time was significantly shorter for HAB (17.6 ± 14 min) vs. EAB (41.4 ± 34.9 min), as was removal time at 6 weeks (9.4 ± 7.4 min vs. 23.4 ± 9.3 min; P = 0.0005 for both). Surgeon-related factors showed markedly lower glove perforation (25% vs. 100%) and prick injuries (8.3% vs. 66.7%) with HAB (P = 0.0005).

Patient-related factors: Pain during application (VAS) was 6.2 ± 0.9 for HAB vs. 7.9 ± 1.1 for EAB (P = 0.01); during MMF, 3.8 ± 1.0 vs. 5.1 ± 0.8 (P = 0.006). Root damage occurred in 41.7% (n = 10) of HAB cases, none in EAB (P = 0.37, NS). Pulpal violation was 8.3% in HAB, 0% in EAB (NS). Periodontal damage and bone loss were comparable (HAB 75% and EAB 66.7%).

Localized gingival hyperplasia occurred in 10 patients per group, resolving post-removal. Screw loosening/instability occurred in 4 HAB cases; no EAB hardware failures were noted as shown in Figure 3.

Figure 3.

Complications observed at 6th week. (a) Mucosal overgrowth over the loops. (b) Screw loosening

DISCUSSION

This study compared the effectiveness and outcomes of Stryker’s SMARTLock HAB with traditional EAB in mandibular fracture management.

HAB placement time was 23 minutes shorter than EAB, aligning with the primary outcome. This reduction is due to self-drilling screws versus circumdental wires in EAB.[3] Kendrick et al.[4] note that bone-borne screws improve HAB versatility across fracture types, Studies by Bouloux, King, Kendrick, and Chao report reduced HAB application times.[2,3,4,5] Variations in reported times may relate to screw number, fracture complexity, surgeon experience, and anesthesia choice.[3] All studies consistently found faster HAB application. In our study, local anesthesia with patient comfort needs contributed to longer times than in prior reports. Bouloux et al.[5] emphasized HAB advantages for closed reduction, shortening surgical time and complexity.

HAB removal averaged 9.4 minutes, similar to Kendrick[4] and King[2] and shorter than EAB removal. King et al.[2] found EAB wiring discomfort increased follow-up visits, unlike HAB. In our study, no patients were lost to follow-up. HAB removal was better tolerated; supraperiosteal infiltration at screw sites sufficed, whereas EAB removal required field/nerve blocks.

Glove perforations and prick injuries were more common in EAB, consistent with other reports, due to greater wiring. HAB still showed 25% glove perforation. Literature notes 100% glove perforations in MMF or complex facial surgeries involving plates, wires, and screws, raising infectious disease concerns.[6] Schwimmer et al.[7] recommend double gloving to reduce perforations in EAB to 37%. Pieper et al.[8] advocate double latex gloves with a liner, preserving the inner glove in most cases; without liners, triple gloving is advised. However, triple gloving may reduce tactile sensation, affecting surgeon preference.

Injury to tooth roots occurred in 10 HAB cases, and pulpal violation in 2, versus none in EAB. Despite Orthopantomogram-based screw positioning, deflection in screw path can cause damage.[9] In thinner mandibular regions, 6 mm screws are preferred over 8 mm to avoid teeth injury.[3] Tooth pain was managed endodontically, leaving patients asymptomatic. Bone loss rates did not differ significantly. Pain scores were lower with HAB than EAB, improving comfort and acceptability, especially during prolonged IMF. This enhanced patients’ social coping post-surgery, as HABs did not adversely affect quality of life.

One HAB challenge was eyelet interference during intraoral incisions or plate/screw placement. Solutions included eyelet fixation, removal, or incision modification. Bouloux et al.[5] avoided interference by placing incisions farther in the vestibule, but this hampered alveolar-level reduction. Chao et al.[3] recommended anterior incisions or eyelet removal. For complex fractures, EAB’s circumdental wiring provided better segment handling, precise reduction, and stabilization.[10]

Complications included localized gingival hyperplasia in both groups, resolving after device removal. Screw loosening occurred in some HAB cases, raising stability concerns. Kendrick et al.[4] recommend orthogonal screw placement for improved stability. Lip irritation from arch bar components was managed with orthodontic wax.[11]

Partially edentulous ridges, especially lacking molars or canines, hinder MMF making EAB less suitable. Being bone-borne, HAB enables fixation without dental support, ideal for compromised arches.

Overall, the SMARTLock HAB system appears to offer an effective alternative to EAB for maxillomandibular fixation, with advantages including easier placement and removal,[12] reduced injury risk, potential tension band function,[13] and improved patient comfort and compliance. Drawbacks include higher cost, concerns over long-term stability, structural damage,[14] and hardware complications.[15] Further research with larger samples, varied fracture types, and long-term follow-up would clarify HAB’s role in broader clinical contexts.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.