Common peroneal palsy is a common nerve disease of the lower extremities. Most common peroneal palsy can be treated by nerve release. Samuel C. George et al. evaluated 28 studies (1577 cases of common peroneal nerve repair) through a review of extensive literature and found that 80% of patients undergoing common peroneal nerve release had a good prognosis, while 37% of patients undergoing direct nerve suture had a good prognosis. The proportion of patients who underwent nerve graft repair had a good prognosis (defined as muscle strength of M4 or above as measured by the MRC Muscle Strength Scale) of 36%. Dorsiflexion can be achieved by reconstructing the tibialis posterior muscle transposition, even if the prognosis is poor. Therefore, most scholars do not pay attention to the etiological research of common peroneal nerve palsy. There are a small number of patients with common peroneal nerve palsy in clinical practice, for whom no possible cause is found when their medical histories are queried. We call these patients spontaneous common peroneal nerve palsy. Regarding these patients and considering the proximal tibiofibular joint, a rare clinical injury that is often neglected and difficult to diagnose, we believe that spontaneous peroneal nerve palsy may be related to the proximal tibiofibular joint. Therefore, we conducted a retrospective study on the etiology of patients with spontaneous peroneal nerve palsy.
The earliest description of Peking Opera by Dubrueil Ogden's research on the proximal tibiofibular joint has been widely recognized. Ogden divided proximal tibiofibular joint dislocation into four main types: subluxation, anterolateral dislocation, posterometral dislocation, and superior dislocation. Nikolaides et al. suggested that the lower dislocation was considered as Type V for the upper tibiofibular joint dislocation. The lower dislocation is caused by high-energy trauma and is often associated with severe fractures and vascular and nerve damage, suggesting severe limb damage. The overall proportion of the 200 proximal tibiofibular joint dislocations reported by Ogden was as follows: 18% sucuxations, 69% anterolateral, 4% posterolateral, 7% superior lateral, and 2% inferior. Ogden divided the proximal tibiofibular joint into two types according to the inclination of the joint surface. Type I is horizontal: the shape of the joint surface is flat and round, and the angle between the joint surface and the horizontal plane is less than 20°, with relatively larger joint area and rotation. Type II is inclined: the angle between the articular surface and the horizontal plane is > 20°, with a variety of different shapes, structures, and degrees of tilt; the tilt angle is up to 76°, and more prone to instability and dislocation (Figure 6).
Acute dislocation can cause lateral swelling, pain, inability to load, and varying degrees of knee movement limitation. Temporary symptoms of common peroneal nerve injury may occur in some patients, especially those with posteromedial dislocation. For patients with acute dislocation, it is characteristic that almost no pain or instability is felt on the lateral side of the knee immediately after successful reduction. Subluxation of the proximal tibiofibular joint may present as unprovoked pain on the lateral side of the knee, with increased pain when the fibular head is pressed, or, in rare cases, as an external deformity caused by the protrusion of the fibular head without any discomfort. X-ray is used to diagnose the dislocation of the tibiofibular joint. Hey et al. studied 2984 knee radiographs and found that the anteroposterior radiographs of the fibular head always pointed to the outer margin of the lateral femoral condyle, and the lateral radiographs pointed to the top line of the intercondylar fossa of the femur, which was highly specific for the diagnosis of tibiofibular joint dislocation. The optimal anteroposterior radiographs of the knee should be under weight bearing, and the lateral radiographs should bend at least 20°. The knee contrast film is helpful for definite diagnosis, but this method is affected greatly by the angle of projection and sometimes is not accurate. Three-dimensional CT is the gold standard for definite diagnosis. MRI can be used to evaluate the soft tissue injuries around the capsule and joint and can also be used to distinguish chronic instability from meniscus injury.
Currently, diagnosis of proximal tibiofibular joint dislocation usually requires a history of trauma and CT examination. However, none of the 10 patients in this study had complaints of lower extremity trauma, and no obvious abnormalities were found in X-ray films of both lower extremities. CT results of lower limbs in three patients showed anatomic abnormalities of the proximal tibiofibular joint but did not meet the diagnostic criteria for proximal tibiofibular joint dislocation. When the proximal tibiofibular joint is anatomically abnormal, similar to the inferior or anterolateral dislocation of the proximal tibiofibular joint, the proximal fibula occasionally pulls on the common peroneal nerve, resulting in compression of the common peroneal nerve. During the intraoperative exploration, we found that although the proximal and distal parts of the common peroneal nerve were released, the tension of the common peroneal nerve remained high. When we removed the proximal part of the fibula, the tension of the common peroneal nerve was significantly reduced. This results confirms our hypothesis.
In clinical practice, patients with common peroneal nerve palsy, who have no history of trauma or cyst compression, often develop symptoms of common peroneal nerve palsy without obvious cause. In these patients, we speculate that the cause of common peroneal nerve palsy may be anatomic abnormality of the proximal tibiofibular joint or recessive dislocation of the old proximal tibiofibular joint (Figure 7). This may result in chronic compression of the common peroneal nerve, which remains stretched after the release of scar tissue around the nerve at the fibula head. Some patients are still not satisfied with the therapeutic effect after the release. Complete release of the common peroneal nerve can only be achieved if anatomic abnormalities at the proximal tibiofibular joint, such as a peroneal osteotomy, are resolved.
In this study, the etiology of common peroneal nerve palsy of unknown clinical origin was investigated. We found that the common peroneal nerve was compressed by the anatomic abnormality at the proximal tibiofibular joint. Part of the fibula should be removed during the operation to release the common peroneal nerve completely. The limitation of this study lies in the small number of such patients, which affects the reliability of the conclusion. However, the preoperative imaging evidence that we found and the fact that the common peroneal nerve recovered quickly after osteotomy verified our conclusion, which also provides some inspiration for the study of such etiology.