BSSROとUSSOで治療した非対称性下顎前突症が顎関節に及ぼすバイオメカニクス的影響：3次元有限要素解析

Biomechanical effect of asymmetric mandibular prognathism treated with BSSRO and USSRO on temporomandibular joints: a three-dimensional finite element analysis.

• H Li
• N Zhou
• X Huang
• T Zhang
• S He
• P Guo

抄録

非対称性下顎前突症は、臨床的によく見られる骨格性歯顎顔面奇形である。片側矢状突起分割骨切り術(USSRO)は、患者によっては両側矢状突起分割骨切り術(BSSRO)に代わる有効な術式である。しかし、顎関節のバイオメカニクス的影響については十分な研究がなされていない。本研究では、BSSRO/USSROによる治療を受けた非対称下顎前突症患者の顎関節における応力分布の変化を評価し、USSROの臨床的有用性を検証することを目的としている。BSSRO（n=12）とUSSRO（n=7）で治療を受けた下顎前突症患者19名を対象に，術前と術後のCTスキャンを行った．BSSRO患者1名とUSSRO患者1名を対象に、機能的顎関節運動の術前・術後3次元有限要素解析（FEA）を行った。すべての患者において、術後にANB角度と下顎偏位が有意に改善された。術後のANB角度と下顎偏位は、BSSRO群とUSSRO群で有意差はなかった。術前の2つのFEAモデルにおいて、機能的動作時に非偏位側の顎関節構造物の最大応力が偏位側よりも大きくなっていた。BSSRO/USSROの両FEモデルにおいて、術後にアンバランスな応力分布が修正された。BSSRO/USSROともにANB角度と下顎偏位を改善することができた。非対称性下顎前突症患者の両側顎関節構造はアンバランスなストレスを有しており，BSSROと同様にUSSROで有意に改善することができた．

Asymmetric mandibular prognathism is a clinically common skeletal dentomaxillofacial deformity. Unilateral sagittal split ramus osteotomy (USSRO) is an effective alternative procedure to bilateral sagittal split ramus osteotomy (BSSRO) for some patients. However, the biomechanical effect of temporomandibular joint (TMJ) of USSRO has not been fully studied. This study aims to evaluate the stress distribution changes in the TMJ of asymmetric mandibular prognathism treated with BSSRO/USSRO, to validate the clinical feasibility of USSRO. Nineteen patients with mandibular prognathism patients who were treated with BSSRO (n=12) and USSRO (n=7) had preoperative and postoperative computed tomographic scanning. Preoperative and postoperative 3-dimensional finite element analysis (FEA) of functional TMJ movements were made on one BSSRO patient and one USSRO patient. In all patients, the ANB angle and mandibular deviation were significantly improved postoperatively. There was no significant difference in the postoperative ANB angle and mandibular deviation between the BSSRO group and the USSRO group. In two preoperative FEA models, the maximum stresses of non-deviation side TMJ structures were greater than the deviation side during functional movements. The unbalanced stress distribution was corrected postoperatively in both BSSRO/USSRO FE models. Both BSSRO/USSRO can improve the ANB angle and mandibular deviation. The bilateral TMJ structure in patients with asymmetrical mandibular prognathism had unbalanced stress, which could be significantly improved with the USSRO as effectively as BSSRO.

Copyright © 2020 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.