Bad Split Associated with High Bone Density in Sagittal Split Ramus Osteotomy-A New Postulation

An unfavorable and unanticipated split pattern of sagittal split ramus osteotomy (SSRO) is generally referred to as a ＂bad split＂. Bad split is a common complication which can lead to infection, delayed bone healing, and pseudoarthrosis. The correlations between bad splits, age, surgical techniques and previous third molar extraction wounds have been discussed in the literature. However, high bone density as a risk factor of bad splits have not been addressed in previous literatures. In this article, we aim to analyze the relationship between bone density and the occurrence of unfavorable fractures based on the experience of a rare and extensive bilateral bad splits in a 21 years old male with skeletal class III malocclusion. This was the most severe bad split that we've encountered in the past five years. We carefully reviewed the preoperative cone beam computed tomography (CBCT) images and found that there seemed to be extraordinarily high bone density with a thick cortex all over the osteotomy sites. In our study, 32 consecutive male patients who had undergone orthognathic surgery in our department on 2019 September to 2021 July and another 3 cases had bad splits were selected. We retrospectively measured the grayscale value (GSV) of 3 specific sites at the lower border of the mandibular body from preoperative CBCT images. The Wilcoxon signed-rank test was used to evaluate the differences between the groups. A P-value less than 0.05 was considered statistically significant. Therefore, it is advisable to conduct a routine and meticulous survey of bone density and cortical thickness preoperatively. This will facilitate precise bone cutting completely through the entire cortical layer and reduce bad splits during SSRO.

關鍵字

Orthognathic surgery ； Sagittal split ramus osteotomy ； Bad split ； Bone density

並列摘要

在下顎骨矢狀劈骨術中，非理想及非預期性的骨斷裂被我們稱為非預期骨裂。非預期骨裂作為一個矢狀劈骨術的併發症，容易造成術後傷口感染、骨癒合不良及顳顎關節相關症狀。許多文章針對造成非預期骨裂的風險因子有相當的著墨，例如患者年齡、手術的術式及是否於手術中移除下顎第三大臼齒，但是針對骨密度因素導致非預期骨裂的討論則鮮少被提及。本研究乃源自一個特別的非預期骨裂案例，讓我們試圖尋找骨密度以及非預期骨裂的關聯性。這是一個21歲患有骨性第三級咬合不正的男性患者，在進行下顎骨雙側矢狀劈骨術時，發生雙側嚴重的頰側非預期骨裂，這是本院近五年內發生過最嚴重的非預期骨裂。仔細檢視患者術前的電腦斷層影像發現此患者於截骨區的骨密度不管皮質骨或海綿骨都較沒有發生非預期骨裂的患者高。為此我們挑選了32位2019年9月至2021年7月於本院進行下顎骨矢狀劈骨術的男性患者，與另外3位有發生非預期骨裂的男性患者來進行分析。我們測量這些患者術前電腦斷層影像的三個下顎骨截骨區的骨密度，發現於發生非預期骨裂的患者，骨密度確實高於沒有發生非預期骨裂的患者，且具有統計上的顯著差異。藉由術前的骨密度分析，若患者的骨密度較高，我們可以於手術的術式或是骨切割方式進行修改，以減少術中發生非預期骨裂的機會。

並列關鍵字

正顎手術；下顎矢狀劈骨術；非預期骨斷裂；骨密度

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