Reddy Chandan G, Amrami Kimberly K, Howe Benjamin M, Spinner Robert J
Department of Neurosurgery, University of Iowa Carver College of Medicine, Iowa City, Iowa; and.
Departments of 2 Neurologic Surgery and.
Neurosurg Focus. 2015 Sep;39(3):E8. doi: 10.3171/2015.6.FOCUS15125.
OBJECT Knee dislocations are often accompanied by stretch injuries to the common peroneal nerve (CPN). A small subset of these injuries also affect the tibial nerve. The mechanism of this combined pattern could be a single longitudinal stretch injury of the CPN extending to the sciatic bifurcation (and tibial division) or separate injuries of both the CPN and tibial nerve, either at the level of the tibiofemoral joint or distally at the soleal sling and fibular neck. The authors reviewed cases involving patients with knee dislocations with CPN and tibial nerve injuries to determine the localization of the combined injury and correlation between degree of MRI appearance and clinical severity of nerve injury. METHODS Three groups of cases were reviewed. Group 1 consisted of knee dislocations with clinical evidence of nerve injury (n = 28, including 19 cases of complete CPN injury); Group 2 consisted of knee dislocations without clinical evidence of nerve injury (n = 19); and Group 3 consisted of cases of minor knee trauma but without knee dislocation (n = 14). All patients had an MRI study of the knee performed within 3 months of injury. MRI appearance of tibial and common peroneal nerve injury was scored by 2 independent radiologists in 3 zones (Zone I, sciatic bifurcation; Zone II, knee joint; and Zone III, soleal sling and fibular neck) on a severity scale of 1-4. Injury signal was scored as diffuse or focal for each nerve in each of the 3 zones. A clinical score was also calculated based on Medical Research Council scores for strength in the tibial and peroneal nerve distributions, combined with electrophysiological data, when available, and correlated with the MRI injury score. RESULTS Nearly all of the nerve segments visualized in Groups 1 and 2 demonstrated some degree of injury on MRI (95%), compared with 12% of nerve segments in Group 3. MRI nerve injury scores were significantly more severe in Group 1 relative to Group 2 (2.06 vs 1.24, p < 0.001) and Group 2 relative to Group 3 (1.24 vs 0.13, p < 0.001). In both groups of patients with knee dislocations (Groups 1 and 2), the MRI nerve injury score was significantly higher for CPN than tibial nerve (2.72 vs 1.40 for Group 1, p < 0.001; 1.39 vs 1.09 for Group 2, p < 0.05). The clinical injury score had a significantly strong correlation with the MRI injury score for the CPN (r = 0.75, p < 0.001), but not for the tibial nerve (r = 0.07, p = 0.83). CONCLUSIONS MRI is highly sensitive in detecting subclinical nerve injury. In knee dislocation, clinical tibial nerve injury is always associated with simultaneous CPN injury, but tibial nerve function is never worse than peroneal nerve function. The point of maximum injury can occur in any of 3 zones.
膝关节脱位常伴有腓总神经（CPN）的牵拉伤。其中一小部分损伤也会影响胫神经。这种联合损伤的机制可能是CPN的单一纵向牵拉伤延伸至坐骨神经分叉处（及胫神经分支），或者是CPN和胫神经在胫股关节水平或在比目鱼肌吊索和腓骨颈远端的单独损伤。作者回顾了涉及膝关节脱位合并CPN和胫神经损伤患者的病例，以确定联合损伤的定位以及MRI表现程度与神经损伤临床严重程度之间的相关性。
回顾了三组病例。第1组为有神经损伤临床证据的膝关节脱位患者（n = 28，包括19例CPN完全损伤）；第2组为无神经损伤临床证据的膝关节脱位患者（n = 19）；第3组为轻度膝关节创伤但无膝关节脱位的病例（n = 14）。所有患者在受伤后3个月内均进行了膝关节的MRI检查。由2名独立的放射科医生在3个区域（I区，坐骨神经分叉处；II区，膝关节；III区，比目鱼肌吊索和腓骨颈）对胫神经和腓总神经损伤的MRI表现进行评分，严重程度分为1 - 4级。对3个区域中每条神经的损伤信号按弥漫性或局灶性进行评分。还根据医学研究委员会对胫神经和腓总神经分布区力量的评分计算临床评分，并结合可用的电生理数据，与MRI损伤评分进行相关性分析。
第1组和第2组中几乎所有可见的神经节段在MRI上均显示出一定程度的损伤（95%），而第3组中神经节段的损伤率为12%。第1组的MRI神经损伤评分相对于第2组显著更严重（2.06对1.24，p < 0.001），第2组相对于第3组也显著更严重（1.24对0.13，p < 0.001）。在两组膝关节脱位患者（第1组和第2组）中，CPN的MRI神经损伤评分显著高于胫神经（第1组为2.72对1.40，p < 0.001；第2组为1.39对1.09，p < 0.05）。临床损伤评分与CPN的MRI损伤评分具有显著的强相关性（r = 0.75，p < 0.001），但与胫神经的相关性不显著（r = 0.07，p = 0.83）。
MRI在检测亚临床神经损伤方面高度敏感。在膝关节脱位中，临床胫神经损伤总是与CPN损伤同时存在，但胫神经功能从不比腓总神经功能差。最大损伤点可出现在三个区域中的任何一个。
