A comparative biomechanical evaluation of different osteosynthesis techniques used for intracapsular condylar head fractures

Application of Crus of Helix Incision Through the Posterior Parotid Gland Approach in the Mid-Level or High-Level Mandibular Condylar Fractures

OBJECTIVE

This study is to explore the clinical effect of crus of helix incision through the posterior parotid gland approach in the treatment of Mid-or High-Level mandibular condylar fractures.

METHODS

From September 2020 to June 2023, we performed incision reduction internal fixation of 23 patients with mid-level or high-level fractures of the mandibular condylar through the approach of the posterior parotid gland, and observed the effect of the operation.

RESULTS

After a follow-up period of 6 to 12 months, all patients showed no signs of postoperative facial paralysis or salivary gland fistula. In addition, satisfactory scars were observed in the operation area, and the occlusion function had recovered well.

CONCLUSION

The approach of using a crus of helix incision through the posterior parotid gland proved to be an effective method for treating mid-level or high-level fractures of the condylar fractures. This technique offers several advantages, including adequate exposure, minimal facial nerve injury, ease of incision and reduction, inconspicuous scarring, and a more concealed incision.

Current Frequency of Mandibular Condylar Process Fractures

There are significant discrepancies in the reported prevalence of condylar process fractures among all mandibular fractures (16.5-56%) in the available literature. In addition, it seems that the actual number of difficult-to-treat fractures of the mandibular head is unknown. The purpose of this study is to present the current incidence of the different types of mandibular process fractures with a special focus on mandibular head fractures. The medical records of 386 patients with single or multiple mandibular fractures were reviewed. Of the fractures found, 58% were body fractures, 32% were angle fractures, 7% were ramus fractures, 2% were coronoid process fractures, and 45% were condylar process fractures. The most common fracture of the condylar process was a basal fracture (54% of condylar fractures), and the second most common fracture was a fracture of the mandibular head (34% of condylar process fractures). Further, 16% of patients had low-neck fractures, and 16% had high-neck fractures. Of the patients with head fractures, 8% had a type A fracture, 34% had a type B fracture, and 73% had a type C fracture. A total of 89.6% of the patients were surgically treated with ORIF. Mandibular head fractures are not as rare as previously thought. Head fractures occur twice as often in the pediatric population than in adults. A mandibular fracture is most likely related to a mandible head fracture. Such evidence can guide the diagnostic procedure in the future.

A Novel Screw Drive for Allogenic Headless Position Screws for Use in Osteosynthesis-A Finite-Element Analysis

Due to their osteoconductive properties, allogenic bone screws made of human cortical bone have advantages regarding rehabilitation compared to other materials such as stainless steel or titanium. Since conventional screw drives like hexagonal or hexalobular drives are difficult to manufacture in headless allogenic screws, an easy-to-manufacture screw drive is needed. In this paper, we present a simple drive for headless allogenic bone screws that allows the screw to be fully inserted. Since the screw drive is completely internal, no threads are removed. In order to prove the mechanical strength, we performed simulations of the new drive using the Finite-Element method (FEM), validated the simulations with a prototype screw, tested the novel screw drive experimentally and compared the simulations with conventional drives. The validation with the prototype showed that our simulations provided valid results. Furthermore, the simulations of the new screw drive showed good performance in terms of mechanical strength in allogenic screws compared to conventional screw drives. The presented screw drive is simple and easy to manufacture and is therefore suitable for headless allogenic bone screws where conventional drives are difficult to manufacture.

Evaluation of internal fixation techniques for condylar head fractures: A finite element analysis and comparison

OBJECTIVES

This study evaluated optimum stability of different screw techniques for condylar head fractures (CHF) (P close to an M fracture with the lateral pole preserved according to AO classification 2014) by finite element analysis (FEA) and provided a biomechanical basis for clinical treatment.

STUDY DESIGN

Four CHF fixation models were evaluated: (A) single bicortical screw, (B) 2 bicortical screws, (C) 1 bicortical screw and 1 monocortical screw (used as a positional screw) inserted via a 2-hole titanium plate, and (D) 2 bicortical screws inserted via a titanium plate. Stresses were calculated (FEA) to measure mechanical properties.

RESULTS

The displacement for A and C was larger than for B and D. The maximum stress on the screws for A and C exceeded their breaking limit but was safe for B and D. The stress on the titanium plate for C and D was safe. The stress on bone for A and C was larger than for B and D.

CONCLUSIONS

The 2 bicortical screw fixation reduced the stress on implanted materials and surrounding bone tissue. Titanium plates further alleviated the lever action. Two bicortical screw fixation was more reliable for CHF, and early postoperative loading and functional training can be expected.

Volumetric Evaluated Bone Resorption After Open Reduction and Internal Fixation of Condylar Head Fractures of the Mandible

PURPOSE

Decision making in the management of condylar head fractures remains difficult due to its dependency on multiple factors like fracture type, degree of dislocation, patient`s age and dental condition. As open reduction and internal fixation (ORIF) of condylar head fractures (CHFs) becomes more popular, the question of osteosynthesis removal is controversial. So far, information on volumetric changes after ORIF are available for a short-term period (<6 months) only. This study, therefore, was performed to assess bone resorption after condylar head fractures and to follow-up intermediate-term (>1 year) remodelling after removal of metallic osteosynthesis material. Furthermore clinical outcome was measured using Helkimo Index and put in relation with bone resorption.

MATERIALS AND METHODS

A retrospective analysis of 19 patients who underwent open reduction and internal fixation of condylar head fractures at the University Hospital of Zürich between January 2016 and April 2018 using intraoperative cone-beam computed tomography repositioning control was conducted. The bone resorption on the condylar head was measured in the course after removal of osteosynthesis material by segmenting and superimposing of the postoperative 3D radiologic follow-up exam (T2) over the initial intraoperative cone-beam computed tomography (T1) using iPlan-CMF software. Complementary Helkimo index was assessed to put resorption rate in relation to clinical outcome.

RESULTS

A total of 19 patients fulfilled the inclusion criteria. The mean follow-up time was 15.6 months and the mean bone resorption on the condylar head was -0.348cm³ or -15.29% of segmented condylar head. There was no correlation of clinical outcome and bone resorption.

CONCLUSIONS

Helkimo index showed satisfying results; therefore, ORIF of condylar head fracture proves as a feasible treatment option. The mean bone resorption rate of -15.29% in the intermediate-term follow-up time (mean 15.6 months) is comparable to findings of other studies with short-term follow-up time (< 6 months). Thus, postinterventional remodeling activity and resorption seems highest in the first 4 to 6 postoperative months with little further resorption. In prevention of negative sequelae of protruding implants, timing of osteosynthesis material removal after this period of high bone remodeling activity is recommended. The resorption rate showed no correlation to clinical outcome.

Change in Pull-Out Force during Resorption of Magnesium Compression Screws for Osteosynthesis of Mandibular Condylar Fractures

BACKGROUND

Magnesium has been used as degradable fixation material for osteosynthesis, but it seems that mechanical strength is still a current issue in these fixations. The aim of this study was to evaluate the axial pull-out force of compression headless screws made of magnesium alloy during their resorption.

METHODS

The tests included screws made for osteosynthesis of the mandible head: 2.2 mm diameter magnesium alloy MgYREZr (42 screws) and 2.5 mm diameter polylactic-co-glycolic acid (PLGA) (42 pieces, control). The screws were resorbed in Sørensen's buffer for 2, 4, 8, 12, and 16 weeks, and force was measured as the screw was pulled out from the polyurethane block.

RESULTS

The force needed to pull the screw out was significantly higher for MgYREZr screws than for PLGA ones (p < 0.01). Within eight weeks, the pull-out force for MgYREZr significantly decreased to one third of its initial value (p < 0.01). The dynamics of this decrease were greater than those of the pull-out force for PLGA screws (p < 0.05). After these eight weeks, the values for metal and polymer screws equalized. It seems that the described reduction of force requires taking into account when using magnesium screws. This will provide more stable resorbable metallic osteosynthesis.

Application of CAD/CAM technology for surgical treatment of condylar head fractures: A preliminary study

Objectives

The aim of the present study was to improve the accuracy and reliability of ORIF in patients with condylar head fractures (CHFs) by developing a design for patient specific fixators, navigation and repositioning guides, as well as the algorithms of their clinical application.

Materials and methods

14 patients with 16 CHFs were treated by ORIF with the use of CAD/CAM technology. After virtual reduction of the bony fragments, the appropriate length and diameter of the screws was chosen. In biomechanically unfavorable cases (type p) patient specific reinforcement plates were used together with the positional screws for reinforcement of the bone-fixator system. And in cases of severely comminuted fractures patient specific 3-D plate was applied.

Results

The CT data, obtained immediately after the operation revealed the good anatomical reduction. Any deviations of the small fragments noted were near 1 mm in all cases. Postoperative clinical examination at 3 months follow up showed good occlusion and mouth opening not less than 3 cm in all patients. The lateral and anterior mobility of the mandible was restored with small limitations of protrusive mobility in 1 case. All the patients were satisfied with the outcomes.

Conclusions

The application of the CAD/CAM technologies and the new design of the surgical guides and patient specific reinforcement plates for CHFs helps to improve the accuracy and quality of fragments reduction and stability of fixation with minimal risks of intraoperative complications.

Clinical relevance

CAD/CAM technologies improve the clinical effectiveness of treatment patients with the CHFs.

Open Reduction Effects of Digitally Treating Zygomaticomaxillary Complex Fractures With Bio-Resorbable Materials

PURPOSE

The application of bio-resorbable plates in craniomaxillofacial surgery is increasing because of the advantage of avoiding secondary surgery. This study aimed to evaluate the effects of osteosynthesis with prebent bio-resorbable plates for treating zygomaticomaxillary complex (ZMC) fractures.

MATERIALS AND METHODS

We implemented a prospective case series composed of patients with ZMC fractures who underwent treatment at the School of Stomatology at China Medical University. Bio-resorbable plates were used for fracture fixation. The fractures were stabilized with bio-resorbable plates prebent on a 3-dimensionally printed skull model with the fractures reduced using virtual simulation. The primary outcome variable was the stability rate of reduced bone segments. Other study variables were mouth opening, occlusion, paresthesia or anesthesia in the infraorbital nerve region (PAIN), and diplopia. Outcome variables were determined by calculating stability rates of reduced bone segments, resolution rates of postoperative restricted mouth opening, malocclusion, PAIN, and diplopia.

RESULTS

The sample was composed of 11 patients recruited between November 2016 and September 2018. All surgical procedures were successful, with no severe complications. The stability rate of reduced bone segments from different mechanical buttress regions was 100%. Satisfactory postoperative stability of bio-resorbable plates was obtained in all cases. The resolution rates of postoperative restricted mouth opening and malocclusion were 75 and 100%, respectively. PAIN and diplopia symptoms resolved in 50 and 100% of cases, respectively.

CONCLUSIONS

The results suggest that osteosynthesis with bio-resorbable plates prebent on a 3-dimensionally printed skull model, designed by virtual simulation, works well for patients with ZMC fractures. Future studies should focus on the broader applications of these findings in the practice of oral and maxillofacial surgery.