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目的:观察枢椎环骨折（axisring fractures, ARF）的损伤形态、提出新的三维CT分型，探讨可能的发生机制。方法:收集7个骨科中心前瞻性保存的有关枢椎骨折数据库，获得符合研究纳入与排除标准的ARF 202例临床资料，将枢椎环各解剖结构骨折分为关节损伤（axis arthrosis fracture，AAF）和骨性损伤（axis bony damage，ABD）。以椎弓根（关节突间部）前后缘为界，将枢椎环分为前环、中环和后环。根据ARF的损伤形态结合既往对不典型Hangman骨折的分型将其分为三型6类。观察各解剖结构骨折的发生特点，提出分型并探讨各型损伤的生物力学特征。结果:202例患者各解剖结构骨折501处，AAF共115例288处（占57%），ABD共178例213处（占43%）。前环骨折304处（占61%），中环骨折99处（占20%），后环骨折98处（占19%）。统计显示AAF发生率>ABD发生率，前环骨折发生率>中环≈后环。分型统计显示：A型，以椎弓根骨折为特征，共30例（15%），包括A1型，双侧椎弓根对称性或非对称性骨折，共12例（6%）；A2型，一侧椎弓根合并对侧下关节突或椎板骨折，18例（11%）。B型，以一侧上关节突和（或）椎体后壁骨折为特征，共136例（67%），包括B1型，合并对侧椎弓根骨折，57例（28%）；B2型，合并对侧下关节突或椎板骨折79例（39%）。C型，以双侧上关节突和（或）椎体后壁骨折为特征，共36例（18%），包括C1型，双侧骨折线基本对称，22例（11%）；C2型，双侧骨折线不对称或相互垂直，14例（8.3%）。结论:枢椎环骨折多是过伸压缩+旋转应力作用于单、双侧上关节突引起的多个解剖结构损伤。三型6类分型法概括了所有病例的损伤解剖和生物力学特征，有利于临床诊断和治疗。“,”Objectives:To observe the anatomical location and mechanism of axis ring fractures (ARF) using 3-D CT scans, and propose a new classification for such fractures.Methods:By reviewing prospectively maintained database collecting ARF from 7 medical centers in China, 202 patients were included in this study. According to anatomical location, ARFs were classified into axis arthrosis fracture (AAF) and axis bony damage (ABD). The axis ring was divided into anterior, middle, and posterior rings, based on the border of the pars interarticularis (or pedicle) of axis. According to the features of ARF and previous study, a new classification was proposed based on the anatomical features of different fracture patterns, which was divided into three types and six subtypes (A1, A2, B1, B2, C1 and C2). The incidence of AAF and ABD and their distribution in different location of axis ring and the new classification, were observed.Results:In 202 patients with ARF, 501 anatomical structures were involved. 288 AAFs were found in 178 patients (288/501, 57%), while 213 ABDs were found in 149 patients (213/501, 43%). In anterior ring, 304 structures (304/501, 61%) were involved in injury, with 225 AAF and 79 ABD. In middle ring, 99 structures (99/501, 20%) were involved in injury, and all of them were ABD. In posterior ring, 98 structures (98/501, 19%) were involved in injury, with 63 AAF and 35 ABD. The anterior ring injuries (61%) were more common than middle (20%) or posterior ring (19%). In anterior ring, AAF (84%) were morecommon than ABD (16%); In middle ring, all the injuries were ABD; In posterior ring, AAFs (64%) were more common than ABD (36%). Type A fractures were featured with pedicle fractures and were identified in 30 patients (30/202, 15%). Type A1 fractures were bilateral pedicle fracture lines symmetrically or asymmetrically and identified in 12 (6%) patients; Type A2 fractures were pedicle fracture lineson one side and inferior articular facet injuries or lamina fractures on the otherside and identified in 18 (9%) patients. Type B fractures were featured with superior articular facet injuries or posterior wall of C2 body fractures on one side and identified in 136 patients (67%). Type B1 fractures were superior articular facet injuries or posterior wall of C2 body fractures on one side and pedicle fracture on the other side and identified in 57 (28%) patients; Type B2 fractures were superior articular facet injuries or posterior wall of C2 body fractures on one side and inferior articular facet injuries or lamina fractures on the otherside and identified in 79 (39%) patients. Type C fractures were featured with bilateral superior articular facet injuries or posterior wall of C2 body fractures and identified in 36 patients (18%). Type C1 fractures were bilateral superior articular facet injuries or posterior wall of C2 body fractures symmetrically and identified in 22 (11%) patients; Type C2 fractures were bilateral superior articular facet injuries or posterior wall of C2 body fractures asymmetrically and identified in 14 (7%) patients.Conclusion:ARF could occur in different anatomical locations, and most of these fractures were caused by hyperextension and axial load on superior articular facet on one or two sides. The new CT classification of ARF with three types and six subtypes might provide all fracture patterns, which could be useful for the choice of proper diagnosis and treatment for such fractures.