跟骨内侧定位载距突螺钉导向器的研制与初步评价

目的　探讨从跟骨内侧定位、经载距突置入导向针后，由跟骨外侧壁置入载距突螺钉的可行性及精确度，为临床手术方案设计及导向器械的研发改进提供参考依据。 方法　选取10具20侧成人尸体标本，在跟骨外侧做“L”形延长切口，暴露跟骨外侧结构及距下关节，采用自主研发的“跟骨内侧定位载距突螺钉导向器”辅助载距突螺钉置入。首先，从内侧将“定位针”置入距下中关节，将导向器“内侧臂”的“定位孔”套牢定位针，调整“内侧臂”使“导向通道”位于载距突中心，安装“外侧臂”与“手柄”固定。调整“外侧臂”位置，经“导向通道”从内向外穿入跟骨一枚“导向针”，C臂透视提示“导向针”位置理想后，自跟骨外侧壁沿“导向针”用空心钻钻孔，测深后拧入合适的载距突螺钉。最后行CT扫描，利用CT图像评估置入螺钉的精确度。过程中采集相关数据，评估导向器的功能。 结果　肉眼观察标本，所有的导向针位于载距突内，其中65%位于载距突中心，25%偏下方，10%偏后方。在内侧，75%的导向针穿过胫后肌腱，15%位于胫后肌和趾长屈肌腱之间，10%穿经趾长屈肌腱上1/3。在外侧，导向针出针点与跟骰关节的距离为（38.03±5.60）mm，与后关节面的距离为（15.01±3.38）mm，螺钉平均长度为（44.80±3.59）mm。CT扫描图像可见，所有螺钉位于载距突内，有2例穿透上方骨皮质，无螺钉穿出载距突下方、前方及后方骨皮质。 结论　采用跟骨内侧定位法，在自主设计的导向器引导下，可提高载距突螺钉置入的准确性，降低螺钉进入关节、跟骨内侧皮质等并发症。

Development and preliminary evaluation of the calcaneal sustentaculum tali director using the method of positioning from the medial of the calcaneus

Objective To evaluate the feasibility and accuracy of the guide needle inserted through the calcaneal sustentaculum tali by locating from inside, while putting the screw from the outside. Methods The L-shaped extended incision was simulated to expose the lateral calcaneal structure and subtalar joints on 10 adult cadaveric specimens (20 sides). The self-designed calcaneal sustentaculum tali director was adopted. First, placed the "positioning needle" from the inside into the subtalar joint, made the “positioning hole” of the “inner arm” entangled the positioning needle, then placed and adjusted the "inner arm of the director" so that the latter "guiding channel" was located in the center of the sustentaculum tali, installed “the lateral arm” to fix “the handle”. Then, a "guide needle" was inserted to the calcaneal from inside to outside via the"guide channel", after C-arm fluoroscopy clarifiing the ideal position of the "guide needle", drilled with a hollow hole from the outside along the "guide needle", then screwed in the appropriate hollow pressure screw. Finally, the specimens were scanned under spiral CT and the accuracy of the insertion screw was evaluated using CT images. Collecting relevant data during the process to evaluate the function of the director. Results The guide needles of all the specimens were located in the sustentaculum tali, 65% of them were located in the center, 25% below and 10% behind. On the inside, 75% of the guide needles passed through the posterior tibia tendon, 15% lied between the posterior tibia tendon and the flexor digitorum longus tendon, and 10% passes through the upper 1/3 of the flexor digitorum longus tendon. On the outside, the distance between the needle outlet point of the guide needle and the calcaneocuboid joint was (38.03±5.60) mm, the distance from the posterior articular surface was (15.01±3.38) mm, the average length of screw was (44.80±3.59) mm. In the CT scan image, all the screws were located in the sustentaculum tali, two cases penetrated the upper bony cortex, no cases showed that screw pierced the inferior and anterior of the sustentaculum tali or lower bony cortex. Conclusions The guidance of the self-designed director which adopted the "medial-oriented method" can improve the accuracy of sustentaculum tali screw placement and reduce the complications such as screw entry into the joint and calcaneal medial cortex.