Lascombes Pierre, Huber Hanspeter, Fay Renaud, Popkov Dimitri, Haumont Thierry, Journeau Pierre
Division of Paediatrics Orthopaedic, University of Geneva, Geneva, Switzerland.
J Pediatr Orthop. 2013 Jun;33(4):403-8. doi: 10.1097/BPO.0b013e318285c54d.
Postoperative axial deviations and delayed unions are possible complications after flexible intramedullary nailing (FIN). The goals of this study were to determine if a correlation exists between occurrence of the above complications and the ratio of the diameter between nail and medullary canal [nail diameter (ND)/MCD ratio], to study the interobserver variability in the measurement of MCD, and to define a threshold to be respected to optimize the results.
Eighty-one consecutive diaphyseal fractures treated by means of FIN were evaluated. The ND/MCD ratios were determined by 2 independent observers. Axial deviations were defined as 5-degree angulation or more observed before bone union. Absence of bone union at 3 months was considered as delayed union. Statistical analysis was made for interobserver variability of MCD, dependency between occurrence of complications and ND/MCD ratio and eventual confounding variables (age, weight, sex, and fracture location).
Of the 81 fractures, 14 presented with an axial deviation and 3 with a delayed union. Interobserver variability of MCD diameter was excellent (intraclass correlation: 0.96). Occurrence of the above complications was significantly associated with a low ND/MCD ratio (P=0.0002) but with none of the examined confounding variables. Receiver operating characteristic analysis showed absence of complications with a ND/MCD ratio >35% with a sensitivity of 100% and specificity of 89%. Related with the MCD measurements variability, a safe threshold of 40% can be suggested.
In FIN, ND>40% to the MCD should be chosen to avoid complications, besides respecting the technical principles. Measuring the medullary canal diameter in order to choose correct nail size is reproducible between different observers. In adolescents with a medullary canal diameter of >10 mm in femur or tibia fractures, alternative methods of osteosynthesis than FIN should be considered.
This work statistically confirms that a ND/MCD ratio of >40% must be respected to avoid some complications in FIN.
Level III.
弹性髓内钉固定术（FIN）后可能出现术后轴向偏差和延迟愈合等并发症。本研究的目的是确定上述并发症的发生与髓内钉直径与髓腔直径之比[髓内钉直径（ND）/MCD比值]之间是否存在相关性，研究观察者间在测量MCD时的变异性，并确定一个应遵循的阈值以优化结果。
对81例采用FIN治疗的骨干骨折患者进行评估。ND/MCD比值由2名独立观察者测定。轴向偏差定义为骨折愈合前观察到的成角5度或更大。3个月时未发生骨折愈合被视为延迟愈合。对MCD的观察者间变异性、并发症发生与ND/MCD比值之间的相关性以及可能的混杂变量（年龄、体重、性别和骨折部位）进行统计分析。
81例骨折中，14例出现轴向偏差，3例出现延迟愈合。MCD直径的观察者间变异性极佳（组内相关系数：0.96）。上述并发症的发生与低ND/MCD比值显著相关（P = 0.0002），但与所检查的混杂变量均无关。受试者工作特征分析显示，ND/MCD比值>35%时无并发症发生，敏感性为100%，特异性为89%。考虑到MCD测量的变异性，可建议安全阈值为40%。
在FIN中，除遵循技术原则外，应选择ND>40%的MCD以避免并发症。不同观察者间测量髓腔直径以选择正确的髓内钉尺寸具有可重复性。对于股骨或胫骨骨折髓腔直径>10 mm的青少年，应考虑采用FIN以外的其他骨固定方法。
本研究从统计学上证实，必须遵循ND/MCD比值>40%以避免FIN中的一些并发症。
三级。
