非典型脂肪-血液界面征用于膝关节隐匿性骨折X线诊断价值

Evaluation of Atypical Fat-Blood Interface Sign in Diagnosing Occult Fracture of Knee Joint

目的探讨非典型脂肪-血液界面(FBI)征在膝关节隐匿性骨折X线诊断中的价值。方法回顾性分析99例膝关节外伤后X线检查阴性,经CT检查确诊膝关节隐匿性骨折和排除膝关节骨折患者的常规膝关节X线及CT资料。CT检查作为金标准,所有的检查均在3天内完成。结合CT描述积脂血症在X线侧位髌上囊的影像表现,作为非典型FBI征。统计隐匿性骨折和无骨折两组资料X线平片显示非典型FBI征的情况,并统计分析以X线侧位髌上囊非典型FBI征作为标准判定膝关节隐匿性骨折的准确度、灵敏度、特异度、阳性似然比、阴性似然比、阳性预测值、阴性预测值。结果 99例患者中,CT确诊隐匿性骨折57例,均存在不同程度的积脂血症,CT检查典型的FBI征见于13例(22.8%)隐匿性膝关节骨折病例,表现为液-液平面10例(17.5%),有时还可以出现三层3例(5.3%)。或者仅表现为关节积血、积液44例(77.2%)。其中51例于X线侧位髌上囊见密度增高,表现为卵圆形、长圆形、条样或斑片样等形态,可以作为FBI征的非典型表现。CT确诊膝关节隐匿性骨折者的X线非典型FBI征发生率为89.5%,明显高于CT排除膝关节骨折者的X线非典型FBI征发生率11.9%,(χ2=56.106,P<0.05)。由X线侧位髌上囊密度增高,即不典型FBI征提示膝关节隐匿性骨折的准确度88.9%,灵敏度89.5%,特异度88.1%,阳性似然比7.52,阴性似然比0.12,阳性预测值91.1%,阴性预测值86.1%。结论外伤后膝关节X线侧位髌上囊密度增高可以作为FBI征的非典型表现,对膝关节隐匿性骨折具有较高的提示作用,可作为诊断膝关节隐匿性骨折的间接征象。

Objective To investigate the clinical value of atypical fat-blood interface（ FBI） sign demonstrated on radiography in diagnosing occult fracture of knee.Methods A total of 99 cases with knee trauma were enrolled in this study.The patients underwent conventional radiography examination at the time of injury and the results were negative,then CT examination was carried out within three days to clarify the presence or absence of occult fracture of knee joint.The imaging materials were retrospectively analyzed.CT result was used as gold standard.Combined with CT description,the manifestation of fat-blood interface on the lateral radiograph was evaluated,which was regarded as atypical fat-blood interface sign.The radiographic appearances of atypical fat-blood interface sign in occult fracture group and non-fracture group were determined,and the accuracy,sensitivity,specificity,positive likelihood ratio,negative likelihood ratio,positive predictive value and negative predictive values of atypical fat-blood interface sign judged by lateral radiograph of knee joint were statistically analyzed.Results In the 99 cases,CT confirmed occult fracture of knee in 57 and different degrees of lipohemarthrosis could be found in all cases.Typical fat-blood interface sign on CT scan was observed in 13 cases（ 22.8%） with occult fracture of knee joint,fluid-fluid level was seen in 10 cases（ 17.5%） and three layers of fluid-fluid level was seen in3 cases（ 5.3%）.Hemarthrosis and joint effusion were found in 44 cases（ 77.2%）.In 51 cases,lateral film showed increased density of suprapatellar bursa,which presented as oval,oblong,stripped or patchy in shape,which were regarded as atypical fat-blood interface sign.The occurrence of atypical fat-blood interface sign in patients with CT-confirmed occult fracture of knee joint was 89.5%,which was significantly higher than that in patients with no fracture of knee joint（ 11.9%,χ2= 56.106,P 〈 0.05）.The accuracy,sensitivity,specificity,positive likelihood ratio,negative likelihood ratio,positive predictive value and negative predictive value of atypical fat-blood interface sign for the diagnosis of occult fracture of knee joint were 88.9%,89.5%,88.1%,7.52,0.12,91.1% and 86.1% respectively.Conclusion An increased density of patellar capsule displayed on the lateral film of the knee joint can be regarded as the atypical fat-blood interface sign; as an indirect sign,atypical fat-blood interface sign is highly suggestive of the presence of occult fracture of knee joint.