The use of a 3D navigation system in the treatment of mandibular angle fractures by minimally invasive insertion of Herbert screws for osteosynthesis

A comparative evaluation of parasymphyseal fracture fixation in edentulous patients performed using dynamic navigation systems and Herbert screws with the conventional two-plate method: A study on models

PURPOSE

The investigators performed this study to compare the rigidity outcomes for minimally invasive fixation of edentulous mandibular parasymphyseal fractures without flap creation using Herbert screws with a dynamic navigation system and the conventional two-plate method.

METHODS

The investigators implemented an in-vitro study design, and 20 polyurethane edentulous mandibular models covered with flexible plastic to simulate the gingiva were used. Parasymphyseal fractures were created in all models using a reciprocal saw. In the study group, the fracture segments in each model were planned to be fixed using two 30-mm Herbert screws. The Herbert screws were placed using a screwdriver with the dynamic navigation system guiding the process. In the control group, to simulate open reduction, the fracture fragments were fixed using two 4-hole straight titanium plates and 6-mm titanium screws. All mandibular models on the prepared platform were attached to the biomechanical testing machine. They were subjected to a continuous linear compression until plastic deformation occurred. Displacement resistance was measured once for every model when the displacement reached 1, 3, 5, 10, and 15 mm. Furthermore, the maximum breaking forces that the models could withstand before deformation were measured. Data were analyzed using independent samples t-test. A value of p < .05 was considered statistically significant.

RESULTS

Manual examination of the models did not reveal any mobility between the fragments. In all evaluated displacement steps, the models fixed using Herbert screws showed significantly higher resistance to mechanical loading compared to the models fixed using parallel miniplates.

CONCLUSION

In present study, parasymphyseal fracture of edentulous mandible models were fixed successfully using Herbert screws with the dynamic navigation system. The results of this study may encourage future clinical studies.

Herbert Cannulated Bone Screw Osteosynthesis in Anterior Mandibular Fracture Treatment: A Comparative Study With Lag Screw and Miniplate

PURPOSE

The Herbert bone screw (HBS) is a successful and minimally invasive method of fracture fixation that is used routinely in orthopedic surgery. The aim of this study was to evaluate the clinical and radiographic performances of the HBS in the treatment of anterior mandibular fractures and compare it with the common and established treatment modalities, the lag screw (LS) and the 2.0-mm miniplate (MP).

MATERIALS AND METHODS

This study implemented a randomized clinical trial and enrolled a sample of patients with anterior mandibular fractures. The primary predictor variable was treatment group categorized as HBS, LS, or MP fixation of the fracture. Primary outcome variables were the presence of interfragmentary mobility and radiodensitometric appraisal of fracture healing progression. The secondary outcome was the postoperative clinical evaluation. Other variables collected were grouped into demographic, fracture location, and intraoperative clinical data. All recorded data were documented, tabulated, computed, and analyzed. Statistical significance was set at the 5% level.

RESULTS

Twenty-one patients were selected and randomly allocated to 1 of 3 groups based on the fixation modality used. There were no relevant differences in demographic data for the 3 groups. There were no statistically relevant differences in clinical evaluation outcomes. However, there was a statistically significant difference in the gain of mean postoperative bone density between the HBS and MP groups (P = .012) and between the LS and MP groups (P = .045), but not between the HBS and LS groups.

CONCLUSION

Cannulated HBS osteosynthesis provides a successful and minimally invasive treatment modality for the management of anterior mandibular fractures.

Osteosynthesis using cannulated headless Herbert screws in mandibular angle fracture treatment: A new approach?

INTRODUCTION

Fractures of the mandibular angle are a common type of facial skull fracture. Although operative treatment includes a wide range of fixation techniques, a definite gold standard method has yet to be established. Headless, cannulated Herbert screws, often used in many forms of minimally invasive trauma surgery, provide functional and stable fracture fixation.

MATERIALS AND METHODS

In a prospective, double-randomised, controlled, parallel-group - designed, in vitro trial, the biomechanical behaviour of the Herbert bone screw system was compared to that of a conventional locking plate system in 40 mandibular angle fractures of human mandible cadaver phantoms.

RESULTS

The mean stress values were 250 (±68.0) N in the plate subgroup and 200 (±61.0) N in the screw subgroup. The respective mean strain values were 7.90 (±2.7) mm and 6.90 (±2.2) mm, and the respective mean stiffness were values 1.10 (±0.61) N/m and 0.78 (±0.40) N/m. The differences in the results obtained using the two treatments were not significant (p = 0.55).

CONCLUSIONS

The biomechanical behaviour of the two fixation systems within the tested loads did not significantly differ with respect to postoperative parameters clinically relevant in osteosynthesis. Both systems met the mandibular angle assessment criterion, which is considered to be sufficient for clinical use. The results indicate the potential clinical utility of these two systems, and recommend further testing.

Fixation of mandibular angle fractures: in vitro biomechanical assessments and computer-based studies

PURPOSE

The purpose of this study was to review the literature regarding the evolution of current thoughts on fixation of mandibular angle fractures (MAFs), based on in vitro biomechanical assessments and computer-based studies.

METHODS

An electronic search in PubMed was undertaken in August 2012. The titles and abstracts from these results were read to identify studies within the selection criteria. Eligibility criteria included studies from the last 30 years (from 1983 onwards).

RESULTS

The search strategy initially identified 767 studies. Thirty-one studies were identified without repetition within the selection criteria. Two articles showing significance in the development of treatment techniques was included. Additional hand searching yielded five additional papers. Thus, a total of 38 studies were included.

CONCLUSIONS

The osteosynthesis positions as well as the plating technique play important roles in the stability of MAF repair. The only in vitro study evaluating the use of wire osteosynthesis concluded that wires placed through the lower border approach would provide greater stability than those at the upper border. Many studies indicate that the use of two miniplates avoids (or decreases) lateral displacement of the lower mandibular border and opening of the inferior fracture gap. Some studies even suggest that the use of two miniplates may be considered a more "rigid" fixation technique for MAFs than the use of a reconstruction plate. When using two miniplates, the biplanar plate orientation provides greater biomechanical stability than the monoplanar one. However, despite its greater biomechanical stability, the two-miniplate technique has some disadvantages that should also be taken into account. Studies with biodegradable plates suggest the use of at least two plates for each MAF. There are few studies with compression plates, and they have not yet reached a consensus. The solitary lag screw proved to withstand the functional loading of the mandible; however, only few biomechanical assessments were performed. In vitro studies have shown good biomechanical stability with the use of 3-D grid plates. The use of malleable miniplates alone is not sufficient to withstand the early postoperative bite force. Some studies suggest that the segment of the tension band miniplate located at the distal fragment of the MAF should be fixed with three screws. The studies also showed some limitations. None considered the stabilization of the fracture site afforded by the masseter-pterygoid muscle pouch. Most of the studies did not evaluate plating system strength in the long term and therefore did not observe the effect of resorption on the strength of the different biodegradable plating systems. Another limitation of many studies is the absence of a control group. A confounding factor that could not be tested in in vitro investigations is the additional resistance to displacement of jagged fracture margins present in the human fracture.