R. E. Chen, S. P. Soin, R. El-Shaar, G. T. Nicandri, H. A. Awad, M. D. Maloney, I. Voloshin, Department of Orthopaedic Surgery and Rehabilitation, University of Rochester, Rochester, NY, USA.
Clin Orthop Relat Res. 2019 Dec;477(12):2726-2732. doi: 10.1097/CORR.0000000000000951.
Osteosynthesis of distal clavicle fractures can be challenging because of comminution, poor bone quality, and deforming forces at the fracture site. A better understanding of regional differences in the bone structure of the distal clavicle is critical to refine fracture fixation strategies, but the variations in BMD and cortical thickness throughout the distal clavicle have not been previously described.
/questions (1) Which distal clavicular regions have the greatest BMD? (2) Which distal clavicular regions have the greatest cortical thickness values?
Ten distal clavicle specimens were dissected from cadaveric shoulders. Eight specimens were female and two were male, with a mean (range) age of 63 years (59 to 67). The specimens were selected to match known epidemiology, as distal clavicular fractures occur more commonly in older patients with osteoporotic bone, and clavicular fractures in older patients are more common in females than males. The clavicles were then imaged using quantitative micro-CT to create 3-D images. The BMD and cortical thickness were calculated for 10 regions of interest in each specimen. These regions were selected to represent locations where distal clavicular fractures commonly occur and locations of likely bony comminution. Findings were compared between different regions using repeated measures ANOVA with Geiser-Greenhouse correction, followed by Bonferroni method multiple comparison testing. Effect size was also calculated to estimate the magnitude of difference between regions.
The four most medial regions of the distal clavicle contained the greatest BMD (anterior intertubercle space 887 ± 31 mgHA/cc, posterior intertubercle space 879 ± 26 mgHA/cc, anterior conoid tubercle 900 ± 21 mgHA/cc, posterior conoid tubercle 896 ± 27 mgHA/cc), while the four most lateral regions contained the least BMD (anterior lateral distal clavicle 804 ± 32 mgHA/cc, posterior lateral distal clavicle 800 ± 38 mgHA/cc, anterior medial distal clavicle 815 ± 27 mgHA/cc, posterior medial distal clavicle 795 ± 26 mgHA/cc). All four most medial regions had greater BMD than the four most lateral regions, with p < 0.001 for all comparisons. For the BMD ANOVA, η was determined to be 0.81, representing a large effect size. The four most medial regions of the distal clavicle also had the greatest cortical thickness (anterior intertubercle space 0.7 ± 0.2 mm, posterior intertubercle space 0.7 ± 0.3 mm, anterior conoid tubercle 0.9 ± 0.2 mm, posterior conoid tubercle 0.7 ± 0.2 mm), while the four most lateral regions had the smallest cortical thickness (anterior lateral distal clavicle 0.2 ± 0.1 mm, posterior lateral distal clavicle 0.2 ± 0.1 mm, anterior medial distal clavicle 0.3 ± 0.1 mm, posterior medial distal clavicle 0.2 ± 0.1 mm). All four most medial regions had greater cortical thickness than the four most lateral regions, with p < 0.001 for all comparisons. For the cortical thickness ANOVA, η was determined to be 0.80, representing a large effect size. No differences in BMDs and cortical thicknesses were found between anterior and posterior regions of interest in any given area.
In the distal clavicle, BMD and cortical thickness are greatest in the conoid tubercle and intertubercle space. When compared with clavicular regions lateral to the trapezoid tubercle, the BMD and cortical thickness of the conoid tubercle and intertubercle space were increased, with a large magnitude of difference.
Distal clavicular fractures are prone to comminution and modern treatment strategies have centered on the use of locking plate technology and/or suspensory fixation between the coracoid and the clavicle. However, screw pullout or cortical button pull through are known complications of locking plate and suspensory fixation, respectively. Therefore, it seems intuitive that implant placement during internal fixation of distal clavicle fractures should take advantage of the best-available bone. Although osteosynthesis was not directly studied, our study suggests that the best screw purchase in the distal clavicle is available in the areas of the conoid tubercle and intertubercle space, as these areas had the best bone quality. Targeting these areas during implant fixation would likely reduce implant failure and strengthen fixation. Future studies should build on our findings to determine if osteosynthesis of distal clavicular fractures with targeted screw purchase or cortical button placement in the conoid tubercle and intertubercle space increase fixation strength and decreases construct failure. Furthermore, our findings provide consideration for novel distal clavicular locking plate designs with modified screw trajectories or refined surgical techniques with suspensory fixation implants to reliably capture these areas of greatest bone quality.
由于粉碎性骨折、骨质量差以及骨折部位的变形力，锁骨远端骨折的内固定治疗颇具挑战性。更好地了解锁骨远端骨结构的区域差异对于完善骨折固定策略至关重要，但锁骨远端的骨密度（BMD）和皮质厚度的变化尚未得到描述。
（1）锁骨远端哪些区域的 BMD 最大？（2）锁骨远端哪些区域的皮质厚度值最大？
从尸体肩部解剖出 10 个锁骨远端标本。8 个为女性，2 个为男性，平均（范围）年龄为 63 岁（59 岁至 67 岁）。这些标本是根据已知的流行病学选择的，因为锁骨远端骨折在骨质疏松性骨折的老年患者中更为常见，而老年患者的锁骨骨折在女性中比男性更为常见。然后使用定量微 CT 对锁骨进行成像，以创建 3-D 图像。对每个标本的 10 个感兴趣区域计算 BMD 和皮质厚度。这些区域是根据锁骨远端骨折常见的位置和可能发生骨粉碎的位置选择的。使用重复测量方差分析（ANOVA）与 Geiser-Greenhouse 校正结合 Bonferroni 方法多重比较检验比较不同区域之间的发现。还计算了效应量，以估计区域之间差异的大小。
锁骨远端的四个最内侧区域包含最大的 BMD（前结节间空间 887 ± 31 mgHA/cc，后结节间空间 879 ± 26 mgHA/cc，前锥状突 900 ± 21 mgHA/cc，后锥状突 896 ± 27 mgHA/cc），而四个最外侧区域包含最小的 BMD（前外侧远端锁骨 804 ± 32 mgHA/cc，后外侧远端锁骨 800 ± 38 mgHA/cc，前内侧远端锁骨 815 ± 27 mgHA/cc，后内侧远端锁骨 795 ± 26 mgHA/cc）。四个最内侧区域的 BMD 均大于四个最外侧区域，所有比较的 p 值均小于 0.001。对于 BMD ANOVA，η 值确定为 0.81，代表大的效应量。锁骨远端的四个最内侧区域的皮质厚度也最大（前结节间空间 0.7 ± 0.2 mm，后结节间空间 0.7 ± 0.3 mm，前锥状突 0.9 ± 0.2 mm，后锥状突 0.7 ± 0.2 mm），而四个最外侧区域的皮质厚度最小（前外侧远端锁骨 0.2 ± 0.1 mm，后外侧远端锁骨 0.2 ± 0.1 mm，前内侧远端锁骨 0.3 ± 0.1 mm，后内侧远端锁骨 0.2 ± 0.1 mm）。四个最内侧区域的皮质厚度均大于四个最外侧区域，所有比较的 p 值均小于 0.001。对于皮质厚度 ANOVA，η 值确定为 0.80，代表大的效应量。在任何给定区域，前、后感兴趣区域之间的 BMD 和皮质厚度均无差异。
在锁骨远端，BMD 和皮质厚度在锥状突和结节间空间最大。与梯形突外侧的锁骨区域相比，锥状突和结节间空间的 BMD 和皮质厚度增加，差异程度较大。
锁骨远端骨折容易发生粉碎性骨折，现代治疗策略的重点是使用锁定钢板技术和/或在喙突和锁骨之间使用悬吊固定。然而，锁定钢板和悬吊固定的已知并发症分别为螺钉拔出或皮质按钮穿过。因此，似乎直观的是，在治疗锁骨远端骨折的内固定过程中，应利用最佳的可用骨。虽然没有直接进行骨合成研究，但我们的研究表明，锁骨远端最佳的螺钉固定位置在锥状突和结节间空间，因为这些区域的骨质量最好。在植入物固定过程中针对这些区域进行治疗可能会降低植入物失败和加强固定的风险。未来的研究应该在我们的发现的基础上进一步确定，针对锁骨远端骨折的骨合成治疗是否可以通过在锥状突和结节间空间进行靶向螺钉固定或皮质按钮固定来增加固定强度并减少结构失效。此外，我们的研究结果为新型锁骨远端锁定钢板设计提供了考虑因素，这些设计具有改进的螺钉轨迹或改进的悬吊固定植入物的手术技术，以可靠地捕获这些最佳骨质量区域。
