The role of the lateral pterygoid muscle in the sagittal fracture of mandibular condyle (SFMC) healing process

A New Method in Dealing With Children's Condylar Fracture by Botulinum Toxin A Injection in Lateral Pterygoid Muscle

Condylar is one of the most vulnerable sites to be traumatized in pediatric mandible fracture, while temporomandibular joint ankylosis might be the most severe complication of condylar fracture in children. There exists a long-time controversy on the treatment of condylar fractures in children. Considering the risk of facial nerve injury and a certain probability of absorption or even ankylosis after open reduction and internal fixation (ORIF) of condylar fractures, a series of nonsurgical approaches are preferred in cases without severe malocclusion or shortening of the ramus. Our treatment plan was carried out through combining procedures of Botulinum toxin A injection in lateral pterygoid muscle with ORIF of para symphyseal fracture; subsequently, a conservative way of the occlusal splint with elastic traction was performed. Three patients of bilateral or unilateral condylar fractures, aged between 2 y and 6 y, were involved in this treatment. After more than 1 year's follow-up, the occlusion was satisfactory in all patients. Condylar remodeling was approximately complete in 3 months, and no unwanted complications were observed. We may expect this method to offer a new idea when dealing with children's condylar fracture.

Treatment for Adult Mandibular Condylar Process Fractures: A Network Meta-Analysis of Randomized Clinical Trials

PURPOSE

Using network meta-analyses (NMA) has become increasingly valuable as it enables the comparison of interventions that have not been directly compared in a clinical trial. To date, there has not been a NMA of randomized clinical trials (RCT) that compares all types of treatments for mandibular condylar process fractures (MCPFs). The aim of this NMA was to compare and rank all the available methods used in the treatment of MCPFs.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic search was conducted in 3 major databases up to January 2023 to retrieve RCTs that compared various closed and open treatment methods for MCPFs. The predictor variable is treatment techniques: arch bars (ABs) + wire maxillomandibular fixation (MMF), rigid MMF with intermaxillary fixation screws, AB + functional therapy with elastic guidance (AB functional treatment), AB rigid MMF/functional treatment, single miniplate, double miniplate, lambda miniplate, rhomboid plate, and trapezoidal miniplate. Postoperative complications were the outcome variables and included occlusion, mobility, and pain, among other things. Risk ratio (RR) and standardized mean difference were calculated. Version 2 of the Cochrane risk-of-bias tool and Grading of Recommendations, Assessment, Development, and Evaluations system were used to determine the certainty of the results.

RESULTS

The NMA included a total of 10,259 patients from 29 RCTs. At ≤6 months, the NMA revealed that the use of 2-miniplates significantly reduced malocclusion compared to rigid MMF (RR = 2.93; confidence interval [CI]: 1.79 to 4.81; very low quality) and functional treatment (RR = 2.36; CI: 1.07 to 5.23; low quality).Further, at ≥6 months, 2-miniplates resulted in significantly lower malocclusion compared to rigid MMF with functional treatment (RR = 3.67; CI: 1.93 to 6.99; very low quality).Trapezoidal plate and AB functional treatment were ranked as the best options in 3-dimensional (3D) plates and closed groups, respectively.3D-miniplates (very low-quality evidence) were ranked as the most effective treatment for reducing postoperative malocclusion and improving mandibular functions after MCPFs, followed closely by double miniplates (moderate quality evidence).

CONCLUSIONS

This NMA found no substantial difference in functional outcomes between using 2-miniplates versus 3D-miniplates to treat MCPFs (low evidence).However, 2-miniplates led to better outcomes than closed treatment (moderate evidence).Additionally, 3D-miniplates produced better outcomes for lateral excursions, protrusive movements, and occlusion than closed treatment at ≤6 months (very low evidence).

Traumatic temporomandibular joint bony ankylosis in growing rats

BACKGROUND

The pathogenesis of traumatic temporomandibular joint (TMJ) bony ankylosis remains unknown. This study aimed to explore the pathogenesis of traumatic TMJ bony ankylosis in a rat model.

METHODS

Twenty-four 3-week-old male Sprague-Dawley rats were used in this study. Excision of the whole disc, the fibrocartilage damage of the condyle and glenoid fossa, and narrowed joint space were performed in the left TMJ of the operation group to induce TMJ bony ankylosis (experimental side). The right TMJ underwent a sham operation (sham side). The control group did not undergo any operations. At 1, 4, and 8 weeks postoperatively, rats of the operation group were sacrificed and TMJ complexes were evaluated by gross observation, Micro-CT, histological examinations, and immunofluorescence microscopy. Total RNA of TMJ complexes in the operation group were analyzed using RNA-seq.

RESULTS

Gross observations revealed TMJ bony ankylosis on the experimental side. Micro-CT analysis demonstrated that compared to the sham side, the experimental side showed a larger volume of growth, and a considerable calcified bone callus formation in the narrowed joint space and on the rougher articular surfaces. Histological examinations indicated that endochondral ossification was observed on the experimental side, but not on the sham side. RNA-seq analysis and immunofluorescence revealed that Matrix metallopeptidase 13 (MMP13) and Runt-related transcription factor 2 (RUNX2) genes of endochondral ossification were significantly more downregulated on the experimental side than on the sham side. The primary pathways related to endochondral ossification were Parathyroid hormone synthesis, secretion and action, Relaxin signaling pathway, and IL-17 signaling pathway.

CONCLUSIONS

The present study provided an innovative and reliable rat model of TMJ bony ankylosis by compound trauma and narrowed joint space. Furthermore, we demonstrated the downregulation of MMP13 and RUNX2 in the process of endochondral ossification in TMJ bony ankylosis.

Lateral Pterygoid Muscle Ossification After Intraoral Condylectomy

PURPOSE

Lateral pterygoid muscle ossification has not been reported in condylectomy patients. This study aimed to explore the incidence, risk factors, and imaging characteristics of 38 cases with lateral pterygoid muscle ossification among 54 patients after condylectomy via intraoral approach.

METHODS

This retrospective study included 54 patients following simultaneous orthognathic surgery and condylectomy with coronoid process resection via intraoral approach. The authors evaluated the preoperative, 1 week, 6 months, and 1 year or more postoperative computed tomographic (CT) scans for the presence of lateral pterygoid muscle ossification and its characteristics. Sex, age at the time of surgery, disease course, affected side, preoperative alkaline phosphatase, pathology diagnosis, the height of the removed condyle, condylar shape, operator, preoperative temporomandibular joint movement, and clinical symptoms were assessed as risk factors for ossification.

RESULTS

No incidence of lateral pterygoid muscle ossification was found on preoperative CT images. Various small-size osseous masses were observed in the lateral pterygoid muscles on postoperative 6 months CT images in 38/54 patients (70.37%) after condylectomy. But no apparent enlargement of the osseous masses was found. No patients complained of clinical discomfort or functional disorder during the follow-up period (23.11 ± 13.16 months). No significant risk factors for ossification were found.

CONCLUSIONS

Lateral pterygoid muscle ossification is relatively common in patients after condylectomy via intraoral approach. However, its enlargement is self-limited and remains stable 6 months after surgery. it has no adverse effects on the temporomandibular joint functional movement.

Three-dimensional morphological analysis of neocondyle bone growth after fibula free flap reconstruction

The aim of this retrospective study was to verify the three-dimensional morphological change in neocondyle bone growth after fibula free flap (FFF) reconstruction. The independent variables were age, sex, and diagnosis. Outcome variables included the direction and volume of neocondyle bone growth, and the time to a stable neocondyle following bone growth. The outcome variables were measured on postoperative computed tomography scans using iPlan 3.0. Of the 35 patients included, 25 showed neocondyle bone growth. The direction of neocondyle bone growth included the direction of lateral pterygoid traction (DLPT) and the direction towards the glenoid fossa (DGF). The bone growth of the neocondyle showed three patterns: only DLPT (eight patients), only DGF (two patients), and a combination of DLPT and DGF (15 patients). The average volume of bone growth in the 25 patients was 0.479 ± 0.380 cm³. The average volume of neocondyle bone growth was significantly greater in patients aged <18 years (0.746 ± 0.346 cm³) than in patients aged >18 years (0.219 ± 0.191 cm³) (P < 0.001). The time to a stable neocondyle following bone growth was 5.6 months postoperatively. In conclusion, neocondyle bone growth after FFF reconstruction occurred in two different directions, DLPT and DGF. Osteogenesis of the lateral pterygoid muscle affects neocondyle growth with DLPT. Neocondyle bone growth is more marked in paediatric patients than in adults.

Pathogenesis of traumatic temporomandibular joint ankylosis: a narrative review

OBJECTIVE

To comprehensively review the literature and summarize the results from human and animal studies related to the possible causes and pathogenesis of traumatic temporomandibular joint ankylosis (TMJA).

MATERIALS AND METHODS

The Google Scholar, Embase, and Web of Science databases were used to search for articles related to traumatic TMJA from 2011 to 2020. All articles were screened according to the inclusion and exclusion criteria, collected, and analyzed.

RESULTS

Nineteen relevant articles were collected. These articles were classified into three groups: predisposing and etiological factors, cellular studies, and molecular studies.

CONCLUSION

The pathological mechanisms are similar between TMJA and nonunion hypertrophy. Aberrant structural and etiological factors as well as disordered cellular and molecular mechanisms might contribute to TMJA formation. Although preclinical and clinical data have provided new evidence on the pathogenesis of traumatic TMJA, the molecular mechanisms and biological events require further exploration.

Association between maximum mouth opening and area of bony fusion in simulated temporomandibular joint bony ankylosis

The aim of this study was to investigate the quantitative association between active/passive maximum mouth opening (AMMO/PMMO) and the severity of simulated temporomandibular joint (TMJ) bony ankylosis. Twenty-eight male sheep were divided randomly and equally into surgical and control groups. Surgical group animals underwent bilateral TMJ osteotomy during which left lateral pterygoid muscle function was blocked. Control animals did not undergo surgery. Body weight, AMMO/PMMO, and TMJ morphological features were evaluated preoperatively and at 12 and 24 weeks post-surgery. In the surgical group, only the right TMJ complexes with maintained lateral pterygoid muscle function developed TMJ bony ankylosis. The AMMO/PMMO and end-feel distance in the surgical group were significantly lower than those in the control group (P < 0.001, both) at 12 and 24 weeks post-surgery. Moreover, AMMO (r = -0.940 and -0.952, P < 0.001, both) and PMMO (r = -0.944 and -0.953, P < 0.001, both) were negatively correlated with the area (mm²) of bony fusion post-surgery. These findings may be useful for the clinical treatment of early mandibular condyle fracture, with the use of occlusal pads/open-mouth plates to relax the lateral pterygoid muscle and block its function. When bony ankylosis developed in the TMJ, the greater the area of bony fusion, the more limited were AMMO/PMMO.

The role of lateral pterygoid muscle in the traumatic temporomandibular joint ankylosis: A gene chip based analysis

Traumatic temporomandibular joint ankylosis (TMJA) is a common disease and disorder of the temporomandibular joint (TMJ); however, its pathogenesis has yet to be completely elucidated. In the authors' previous studies, the lateral pterygoid muscle (LPM) was confirmed to exert a function in distraction osteogenesis (DO) during the healing of a condylar fracture, which resulted in the formation of excess bone. The aim of the present study was to investigate alterations in the expression of any associated genes via an Affymetrix GeneChip method. The traumatic TMJA model was fabricated by a condylar fracture in the TMJ area of sheep with either a dissected LPM (LPD) or normal (LPN). The untreated sheep served as a control. At 4- and 12 weeks post-surgery, the condylar zone was isolated to perform the gene chip analysis, which was performed according to a standard Affymetrix protocol. The validated genes were further evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The gene chip analysis indicated that the LPN gene expression pattern was similar compared with the DO process, while LPD was similar to that of normal bone fracture healing. The validated genes were collagen type II α1 chain, C-type lectin domain family 3 member A, interleukin 1A, cartilage oligomeric matrix protein, chondromodulin (LECT1), calcitonin receptor (CALCR), transforming growth factor (TGF)-β1, Fos proto-oncogene (FOS), bone γ-carboxyglutamate protein and bone morphogenic protein (BMP)7, among which, BMP7, LECT1, CALCR and FOS were confirmed by RT-qPCR. In conclusion, the present study demonstrated that LPM exerts a DO effect during the pathogenesis of traumatic TMJA, which may provide a novel target for preventing TMJA.

Protrusive maxillomandibular fixation for intracapsular condylar fracture: a report of two cases

Clinical limitations following closed reduction of an intracapsular condylar fracture include a decrease in maximum mouth opening, reduced range of mandibular movements such as protrusion/lateral excursion, and reduced occlusal stability. Anteromedial and inferior displacement of the medial condyle fragment by traction of the lateral pterygoid muscle can induce bone overgrowth due to distraction osteogenesis between the medial and lateral condylar fragments, causing structural changes in the condyle. In addition, when conventional maxillomandibular fixation (MMF) is performed, persistent interdental contact sustains masticatory muscle hyperactivity, leading to a decreased vertical dimension and premature contact of the posterior teeth. To resolve the functional problems of conventional closed reduction, we designed a novel method for closed reduction through protrusive MMF for two weeks. Two patients diagnosed with intracapsular condylar fracture had favorable occlusion after protrusive MMF without premature contact of the posterior teeth. This particular method has two main advantages. First, in the protrusive position, the lateral condylar fragment is moved in the anterior-inferior direction closer to the medial fragment, minimizing bone formation between the two fragments and preventing structural changes. Second, in the protrusive position, posterior disclusion occurs, preventing masticatory muscle hyperactivity and the subsequent gradual decrease in ramus height.

Retromandibular reduction of medially dislocated condylar process fractures

Background

Condylar process fractures account for one-third of all mandibular fractures, and the distal fragment is prone to dislocate to the medial side due to the pulling of the lateral pterygoid muscle. Retromandibular approaches are commonly used, but the intraoperative view becomes limited in medially dislocated fractures. This study summarized a series of cases of retromandibular reduction for medially dislocated condylar process fractures and described our supplementary procedure to realign the dislocated condylar process.

Methods

Nine patients with medially dislocated condylar process fractures underwent surgical correction from January 2012 to December 2016. In 6 of them, it was possible to realign the fractures with a conventional retromandibular approach, but for 3 cases of severe dislocation to the middle cranial fossa, a supplementary transoral procedure was carried out. The angle difference between the ramus and condyle, ramus height, and maximal mouth opening (MMO) were evaluated.

Results

All 9 cases were restored to the proper anatomical alignment without any major complications, and postoperative images revealed successful union. The angle difference was 8.94°±4.11° preoperatively, and 0.99±0.49° at the 6-month follow-up. The pretreatment ramus height difference was 6.12±6.09 mm, and the postoperative difference was 0.18±0.10 mm. These changes after surgery were statistically significant. The MMO before surgery was 11.44±3.0 mm, and the postoperative MMO was 37.2±2.9 mm, reflecting a significant increase after reduction.

Conclusions

Retromandibular reduction is a useful method in medially dislocated condylar process fractures, and additional transoral assistance should be considered to realign condylar processes that severely dislocate to the middle cranial fossa.

[Extramedullary fixation combined with intramedullary fixation in the surgical reduction of sagittal mandibular condylar fractures]

OBJECTIVE

This study aimed to evaluate the clinical effect of extramedullary fixation combined with intramedullary fixation during the surgical reduction of sagittal mandibular condylar fractures.

METHODS

Twenty-four sagittal fractures of the mandibular condyle in18 patients were fixed by two appliances: intramedullary with one long-screw osteosynthesis or Kirschner wire and extramedullary with one micro-plate. The radiologically-recorded post-operative stability-associated com-plications included the screw/micro-plate loosening, micro-plate twisting, micro-plate fractures, and fragment rotation. The occluding relations, the maximalinter-incisal distances upon mouth opening, and the mandibular deflection upon mouth opening were evaluated based on follow-up clinical examination.

RESULTS

Postoperative panoramic X-ray and CT scans showed good repositioning of the fragment, with no redislocation or rotation, no screw/plate loosening, and no plate-twisting or fracture. Clinical examination showed that all patients regained normal mandibular movements, ideal occlusion, and normal maximal inter-incisal distances upon mouth opening.

CONCLUSIONS

Extramedullary fixation combined with intramedullary fixation is highly recommended for sagittal condylar fractures because of the anti-rotation effect of the fragment and the reasonable place-ment of the fixation appliances.

Influence of the lateral pterygoid muscle on traumatic temporomandibular joint bony ankylosis

BACKGROUND

The pathogenesis of traumatic TMJ ankylosis remains unclear. This study aimed to verify the role of the lateral pterygoid muscle in the pathogenesis of traumatic temporomandibular joint (TMJ) bony ankylosis.

METHODS

Eight 6-month-old male sheep were used in this study. Bilateral TMJ osteotomies were performed to induce sagittal fractures of the mandibular condyle. The lateral one-fourth segment of the disc was removed to establish a model of TMJ bony ankylosis. Subsequently, the function of the left and right lateral pterygoid muscles was blocked (experimental group) or maintained (control group), respectively. At 12 weeks postoperatively, animals were sacrificed and TMJ complex samples were evaluated by gross observation, spiral computed tomography (CT), micro-CT, and histological examinations.

RESULTS

Gross observation revealed bony ankylosis in the control TMJs and fibrous adhesions in the experimental TMJs. Spiral CT and micro-CT demonstrated that, compared to the experimental group, the control group showed calcified callus formation in the joint space and roughened articular surfaces after new bone formation, which protruded into the joint space. Maximum mediolateral and anteroposterior condylar diameters were significantly larger in the control group than in the experimental group. Micro-CT also showed that the primary growth orientation of new trabeculae was consistent with the direction of lateral pterygoid traction in the control group, but not in the experimental group. Histological examination showed fibro-osseous ankylosis in the control group, but not in the experimental group.

CONCLUSIONS

The lateral pterygoid simulates the effects of distraction osteogenesis, which is an important factor in the pathogenesis of TMJ bony ankylosis during the healing of sagittal condylar fractures.

Osteoclast Deficiency Contributes to Temporomandibular Joint Ankylosed Bone Mass Formation

Ankylosed bone mass in temporomandibular joint ankylosis (TMJA) is an important factor affecting mouth-opening limitation. However, the mechanism underlying the occurrence of ankylosed bone mass remains unknown. Research has shown that osteoblasts and osteoclasts maintain balance in bone remodeling. Thus, we hypothesized that aberrant osteoclastogenesis and osteogenesis may be involved in the occurrence of ankylosed bone mass in TMJA. In this study, we characterized the osteogenesis of bone marrow stem cells and the osteoclastogenesis of myelomonocyte in clinical specimens of TMJA and normal controls. Results showed that, compared with control bone marrow stem cells, TMJA bone marrow stem cells had lower proliferative and osteogenic capacities. The number of osteoclasts in the ankylosed bone mass group dramatically decreased, and myelomonocyte osteoclastogenic potential was impaired. The RANKL/OPG ratio of the ankylosed bone mass group was lower than that of the control group. Thus, our study suggests that osteoclast deficiency may be an important factor affecting bone mass ankylosis.

Evaluation of reference gene suitability for quantitative expression analysis by quantitative polymerase chain reaction in the mandibular condyle of sheep

Reference genes are commonly used as a reliable approach to normalize the results of quantitative polymerase chain reaction (qPCR), and to reduce errors in the relative quantification of gene expression. Suitable reference genes belonging to numerous functional classes have been identified for various types of species and tissue. However, little is currently known regarding the most suitable reference genes for bone, specifically for the sheep mandibular condyle. Sheep are important for the study of human bone diseases, particularly for temporomandibular diseases. The present study aimed to identify a set of reference genes suitable for the normalization of qPCR data from the mandibular condyle of sheep. A total of 12 reference genes belonging to various functional classes were selected, and the expression stability of the reference genes was determined in both the normal and fractured area of the sheep mandibular condyle. RefFinder, which integrates the following currently available computational algorithms: geNorm, NormFinder, BestKeeper, and the comparative ΔCt method, was used to compare and rank the candidate reference genes. The results obtained from the four methods demonstrated a similar trend: RPL19, ACTB, and PGK1 were the most stably expressed reference genes in the sheep mandibular condyle. As determined by RefFinder comprehensive analysis, the results of the present study suggested that RPL19 is the most suitable reference gene for studies associated with the sheep mandibular condyle. In addition, ACTB and PGK1 may be considered suitable alternatives.

Current concepts in the pathogenesis of traumatic temporomandibular joint ankylosis

Traumatic temporomandibular joint (TMJ) ankylosis can be classified into fibrous, fibro-osseous and bony ankylosis. It is still a huge challenge for oral and maxillofacial surgeons due to the technical difficulty and high incidence of recurrence. The poor outcome of disease may be partially attributed to the limited understanding of its pathogenesis. The purpose of this article was to comprehensively review the literature and summarise results from both human and animal studies related to the genesis of TMJ ankylosis.

Biomechanical analysis of fractures in the mandibular neck (collum mandibulae)

After treatment of fractures in the neck of the mandible by means of immobilization of the dentition, often more or less severe manifestations of malocclusion remain. It was hypothesized that this is caused by an altered articulation in the jaw joint on the affected side. Furthermore, it was hypothesized that an anteriorly displaced condyle, as observed frequently as a side effect of the treatment, is caused by pull of the lateral pterygoid muscle, despite maxillomandibular fixation. Intervention experiments were performed in silico to test these hypotheses. With a biomechanical model of the human masticatory system alterations were applied mimicking a fractured mandibular neck and configurations that had been observed after healing. It was predicted that the altered articulation in the jaw joint caused asymmetrical jaw movements despite symmetrical muscle activation. The jaw was predicted to close with an open bite similar to clinical observations. The predicted laterodeviations, however, were not in accordance with clinical observations. Despite maxillo-mandibular fixation the lateral pterygoid muscle was able to pull the mandibular condyle out of its fossa in anterior direction. Consequently, despite some methodological limitations, in general the predictions corroborated the hypotheses.

Current opinions on surgical treatment of fractures of the condylar head

Treatment of mandibular condyle fractures is still controversial, with surgical treatment slowly becoming the preferred option. However, fractures of the condylar head (diacapitular fractures) are still treated conservatively at many institutions. Recently, more and more surgeons have begun to perform open treatment for diacapitular fractures because it allows to restore the anatomical position of the fragments and disc, it allows an immediate functional movement of the jaw, and avoid the ankylosis of the temporomandibular joint induced by the trauma. Several techniques have been proposed to reduce and fix fractures of the condylar head, such as standard bone screws, resorbable screws, resorbable pins, and cannulated lag screws. Therefore, the aim of this article is to review the literature about the surgical treatment of fractures of the condylar head to resume the current knowledge about open treatment of such fractures.

Effect of surgical repair of the joint capsule in mandibular condyle fractures in adult rats

PURPOSE

The aim of the present study was to assess histologic changes in the temporomandibular joint (TMJ) of adult rats subjected to unilateral fracture of the mandibular condyle and soft tissue injury.

MATERIALS AND METHODS

The animals were divided into 2 groups: one had surgical treatment for soft tissue repair and the other had no soft tissue treatment. All histologic evaluations were performed according to the presence or absence of synovitis, vascularity, presence or absence of joint inflammation, and presence or absence of the articular disc. The contralateral TMJs also were evaluated.

RESULTS

The results showed few histologic changes in the synovial membrane and joint disc for the 2 groups and in the synovial membrane and disc of the contralateral side, where indirect trauma occurred in the unoperated joint.

CONCLUSION

This study showed that treating or not treating soft tissues does not change the treatment results of condyle fracture or interfere with TMJ pathosis.

Clinical and radiological outcomes after treatment of sagittal fracture of mandibular condyle (SFMC) by using occlusal splint in children

This study was designed to investigate the effects of occlusal splints in the treatment of sagittal fractures of the mandibular condyle in children. From January 1995 to December 2011, 37 sagittal fractures of the mandibular condyle in 30 patients aged 4-8 years old were included in this study. All the patients were treated with 1-2mm occlusal splints in the molar region. The mouths of the patients were kept slightly open by the occlusal splints for 3-6 months, and we reviewed the clinical and radiological remodelling of the affected condyles after treatment. Excellent (n=20) and good (n=10) clinical outcomes were achieved with full radiological remodelling seen in 19 and partial remodelling in 11. Treatment with occlusal splints is effective in delivering good results and function with minimal morbidity in children with sagittal fractures of the condyle, while permitting ongoing remodelling and growth in the short term.