模拟手术法研究髓腔内螺钉加压固定Jones骨折时的理想螺钉长度及其影响因素

Morphological characteristics of the medullary canal of the fifth metatarsal and their influence on the fixation of Jones fractures with intramedullary screws

目的通过虚拟手术法研究髓腔内螺钉加压固定Jones骨折时螺钉的理想长度及影响因素。方法回顾性分析2020年1月至2020年5月江苏省人民医院创伤骨科采集的44例患者(44侧足)的影像学资料。男26例,女18例;年龄(29.5±5.6)岁。正位X线片上测量第5跖骨髓腔峡部直径、第5跖骨长度,斜位X线片上测量第5跖骨弧度高度。采用Mimics软件在第5跖骨3D模型上确定跖骨粗隆尖和髓腔中心线,以两者为基础按特定规则生成一组虚拟4.5 mm螺钉模拟固定Jones骨折,其中固定效果最佳的为理想髓腔内螺钉(oIS)。将患者按照oIS长度分为长螺钉组(oIS长度≥40 mm,26例)和短螺钉组(oIS长度<40 mm,18例),比较两组患者间年龄、影像学参数的差异。Pearson相关性分析确定年龄、影像学参数与oIS长度间的关系。结果44侧足的oIS长度为(42.2±7.1)mm,占第5跖骨长度的56.1%±8.3%。短螺钉组第5跖骨髓腔峡部直径(4.4±0.9)mm显著小于长螺钉组(4.9±0.7)mm,差异有统计学意义(P=0.040)。两组患者的年龄、第5跖骨长度、第5跖骨弧度高度比较差异均无统计学意义(P>0.05)。第5跖骨髓腔峡部直径(r=0.651,P<0.001)、第5跖骨长度(r=0.507,P<0.001)与oIS长度呈正相关,而年龄、第5跖骨弧度高度与oIS长度无显著相关。结论使用4.5 mm髓腔内螺钉加压固定Jones骨折时可以安全地置入长度≥40 mm的oIS,且oIS长度主要受正位X线片上髓腔峡部直径和第5跖骨长度的影响。

ObjectiveTo investigate the optimal length of an intramedullary screw(IS)and its influencing factors in the fixation of Jones fractures through simulated operations.MethodsA retrospective study was conducted to analyze the imaging data of 44 cases(44 lateral feet)which had been collected at Department of Orthopaedic Trauma,The People’s Hospital of Jiangsu Province from January 2020 to May 2020.There were 26 males and 18 females,with an age of(29.5±5.6)years.The diameter of the medullary isthmus and the length of the fifth metatarsal bone were measured on the anteroposterior view of the foot;the height of the fifth metatarsal arc was measured on the oblique view.Software Mimics was used to reconstruct 3D models of the fifth metatarsal bone and the centerline of the medullary cavity.A set of virtual 4.5 mm IS were generated using the lines connecting the metatarsal tuberosity and specific points on the centerline as the axis to simulate screw compression fixation for Jones fracture.The screw with the largest length and no contact with the metatarsal cortex was taken as an optimal IS(oIS)which could provide the maximum pressure at the broken ends.The patients were divided into a long screw group of 26 cases(oIS length≥40 mm)and a short screw group of 18 cases(oIS length<40 mm)according to their oIS length.The differences in age and image parameters were compared between the 2 groups.Pearson correlation analysis was conducted to identify the relationships between age,imaging parameters,and oIS length.ResultsThe oIS length of the 44 lateral feet was(42.2±7.1)mm,accounting for 56.1%±8.3%of the length of the fifth metatarsal bone.The diameter of the medullary isthmus in the short screw group[(4.4±0.9)mm]was significantly smaller than that in the long screw group[(4.9±0.7)mm](P=0.040).There was no statistically significant difference in age,the length of the fifth metatarsal bone,or the height of the fifth metatarsal arc between the 2 groups(P>0.05).The diameter of the medullary isthmus(r=0.651,P<0.001)and the length of the fifth metatarsal bone(r=0.507,P<0.001)were positively correlated with the oIS length,while age or the height of the fifth metatarsal arc were not significantly correlated with the oIS length.ConclusionsAn oIS greater than 40 mm in length can be safely placed during compression fixation of a Jones fracture using a 4.5 mm intramedullary screw.The oIS length is mainly affected by the diameter of the medullary isthmus and the length of the fifth metatarsal bone on an anteroposterior image.