Sabharwal Sanjeev, Zhao Caixia
Department of Orthopedics, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Doctor's Office Center, 90 Bergen Street, Suite 7300, Newark, NJ 07103, USA.
J Bone Joint Surg Am. 2008 Jan;90(1):43-51. doi: 10.2106/JBJS.F.01514.
While a full-length standing anteroposterior radiograph of the lower extremity provides the best radiographic method for assessing limb alignment, other methods must be used intraoperatively. We have employed intraoperative fluoroscopy with use of an electrocautery cord to assess limb alignment in the supine patient.
We retrospectively compared the measurements of lower limb alignment that were obtained with use of supine intraoperative fluoroscopy with those that were obtained with use of a full-length standing anteroposterior radiograph of the lower extremity. A single examiner compared 102 sets of supine fluoroscopy images and full-length standing anteroposterior radiographs of the lower extremity to assess mechanical axis deviation and the joint line convergence angle. For the intraoperative fluoroscopic examination, an electrocautery cord was positioned overlying the center of the femoral head and the tibial plafond and an anteroposterior radiograph of the knee was made. The effect of age, gender, diagnosis, body mass index, pelvic height difference, joint line convergence angle, and the magnitude and direction of malalignment (varus or valgus) on the discrepancy in the observed mechanical axis deviation with use of the two methods was assessed.
The mean absolute difference between the two techniques was 13.4 mm for the measurement of mechanical axis deviation (p < 0.0001) and 2.8 degrees for the joint line convergence angle (p < 0.0001). The correlation coefficient (r) for the measurement of mechanical axis deviation with use of the two radiographic methods was 0.88. An increase in body mass index was associated with a greater magnitude of discrepancy in the measurement of mechanical axis deviation between the two techniques (p = 0.0014). Age, gender, pelvic height difference, and the direction of malalignment had no effect on the discrepancy in the measurement of mechanical axis deviation. Limbs with >2 cm of mechanical axis deviation and those with a joint line convergence angle of >3 degrees on the standing radiograph were significantly more likely to have >10 mm of discrepancy in the measurement of mechanical axis deviation with use of the two imaging techniques (p < 0.005).
Intraoperative fluoroscopy with use of the electrocautery cord method is a useful tool for assessing lower limb alignment in patients with a normal body mass index and </=2 cm of mechanical axis deviation and </=3 degrees of joint line convergence angle on the standing anteroposterior radiograph. However, the results obtained with fluoroscopy should be interpreted with caution in patients who are obese or who have substantial residual mechanical axis deviation or pathologic laxity of the knee joint.
虽然下肢全长站立位前后位X线片是评估肢体对线的最佳影像学方法，但术中必须使用其他方法。我们采用术中透视并利用电灼线来评估仰卧位患者的肢体对线情况。
我们回顾性比较了仰卧位术中透视与下肢全长站立位前后位X线片所获得的下肢对线测量结果。由一名检查者比较102组下肢仰卧位透视图像和全长站立位前后位X线片，以评估机械轴偏差和关节线汇聚角。对于术中透视检查，将电灼线置于股骨头和胫骨平台中心上方，并拍摄膝关节前后位X线片。评估年龄、性别、诊断、体重指数、骨盆高度差、关节线汇聚角以及对线不齐的程度和方向（内翻或外翻）对两种方法观察到的机械轴偏差差异的影响。
两种技术测量机械轴偏差的平均绝对差值为13.4 mm（p < 0.0001），关节线汇聚角为2.8°（p < 0.0001）。两种影像学方法测量机械轴偏差的相关系数（r）为0.88。体重指数增加与两种技术测量机械轴偏差的差异幅度增大相关（p = 0.0014）。年龄、性别、骨盆高度差和对线不齐的方向对机械轴偏差测量的差异无影响。站立位X线片上机械轴偏差>2 cm以及关节线汇聚角>3°的肢体，使用两种成像技术测量机械轴偏差时差异>10 mm的可能性显著更高（p < 0.005）。
使用电灼线法的术中透视是评估体重指数正常且站立位前后位X线片上机械轴偏差≤2 cm、关节线汇聚角≤3°患者下肢对线的有用工具。然而，对于肥胖患者或膝关节存在明显残余机械轴偏差或病理松弛的患者，透视结果的解释应谨慎。
