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

Abstract

BackgroundThe 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.MethodsEight 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.ResultsGross 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.ConclusionsThe 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.

Pathogenesis of traumatic temporomandibular joint ankylosis: a narrative review

“…Nineteen articles that investigated the pathology of traumatic TMJA were finally included. 4 – 22 These articles were classified into three groups: predisposing factors and etiological factors, cellular studies, and molecular studies ( Table 1 ).…”

“…Furthermore, Deng et al. 21 and Liu et al. 22 found that the size of the ankylosed bone mass was reduced after blocking the lateral pterygoid muscles during ankylosis model surgery.…”

“…A sagittal or comminuted fracture of the condyle may result in medial and downward displacement of the cracked condyle due to stretching of the lateral pterygoid muscle. Furthermore, Deng et al 21 and Liu et al 22 found that the size of the ankylosed bone mass was reduced after blocking the lateral pterygoid muscles during ankylosis model surgery. However, the lateral pterygoid muscles' distraction osteogenesis, which might be related to horizontal osteogenesis, does not seem to be associated with vertical bone formation of the condyle and thickening of the temporal bone.…”

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

“…The animals were fed with a standard diet and had free access to water. The traumatic TMJA model was constructed according to the protocol outlined in previous publications (9,11,12). Briefly, the bilateral TMJ capsule was exposed from an incision to the anterior tragus.…”

“…Based on the anatomy of the lateral pterygoid muscle (LPM), it can be inferred that the contraction of the LPM will generate sufficient distraction force to the condyle neck during the opening of the mouth and confirm the ‘distraction osteogenesis (DO) effect of LPM’ hypothesis, which is that the LPM may exert a DO effect during the healing of the fractured condyle (7). In addition, the LPM exerts an important function in the reconstruction of the sagittal fractured condyle (8) and a previous study has reported that TMJA will be significantly alleviated if the LPM is dissected (9). Furthermore, the study of Dai et al (10) also suggested that local injection of botulinum toxin A would temporarily block impulses from the LPM's and may effectively prevent the occurrence of traumatic TMJA.…”