key: cord-0021675-z4o670ec authors: Szwedowski, Dawid; Ambroży, Jarosław; Grabowski, Radosław; Dallo, Ignacio; Mobasheri, Ali title: Diagnosis and treatment of the most common neuropathies following knee injuries and reconstructive surgery – A narrative review date: 2021-09-22 journal: Heliyon DOI: 10.1016/j.heliyon.2021.e08032 sha: f077a66acbe503dd8a2bf3bb1f101cc45964340f doc_id: 21675 cord_uid: z4o670ec The main nerves in the knee region are the tibial nerve, the common peroneal nerve, and the saphenous nerve. These three nerves innervate the lower leg and foot, providing sensory and motor function. The large sciatic nerve splits just above the knee to form the tibial and common peroneal nerves. The tibial nerve travels down in the posterior region, while the common peroneal nerve runs around the lateral side of the knee and runs down the front of the leg to the foot. Although all these nerves can be affected by injuries of the knee, the infrapatellar branch of the saphenous nerve (IPBSN) and the common peroneal nerve (CPN) are most affected. In this narrative review we focus on neuropathies associated with nerves located in the region of the knee joint in the context of their injuries and possible iatrogenic damage during reconstructive surgery. Knee injuries are increasingly common in adolescents and athletes [12] . Participation in high-impact sports increases the risk of knee injuries that can cause to early onset of osteoarthritis (OA) [34] . Nerves around the knee joint can be damaged by sport and occupational injuries leading to neuropathy. In addition, neuropathy may be caused by surgical treatment of sports injuries [5] . It is well-known that all knee surgeries can be associated with iatrogenic injury to the nerves. This is also true for less invasive procedures such as knee arthroscopy or subchodroplasty [678910] . This paper focuses on the diagnosis and treatment of neuropathies following knee injuries and reconstructive surgery. The saphenous nerve is an important anatomical structure that can vary in its anatomical course not only among individuals but also between sides. It is the cutaneous branch of the femoral nerve, which further bifurcates into two branches. The sartorial branch accompanies the great saphenous vein to the medial region of the foot, and the infrapatellar branch of the saphenous nerve (IPBSN), diverges from the trunk of the saphenous nerve and courses near the sartorius muscle (there are three anatomical variants of its emergence in relation to the sartorius muscle: anteriorly, posteriorly or perforating this muscle), piercing the fascia lata. IPBSN normally has three main branches, which provide sensory innervation to the anteromedial aspect of the knee [11] . Four types of disturbances after IPBSN trauma were described: hypoesthesia, dysesthesia, painful neuroma, and reflex sympathetic dystrophy [12] . The infrapatellar pain syndrome is often compared to a toothache. The correct diagnosis can be time-consuming and in many cases, it can be misdiagnosed or even overlooked by physicians. It may occur secondary to many factors, including post-traumatic and post-surgical ones. It may thus be caused by direct fall on the knee, as well as plenty of surgical procedures including arthroscopy, total knee replacement, and bone-patellar tendon-bone or hamstring tendon harvesting for anterior cruciate ligament (ACL) procedures [13] . Mochida et al. in their study concluded that the incidence of the IPBSN iatrogenic injury during knee arthroscopy that can be caused by medial portal placement is approximately 22% [14] . Noteworthy is the fact that the rate of injury to the IPBSN is higher when ACL reconstruction is performed during arthroscopy. The injury mainly occurs during tendon harvesting ( Figure 1 ). Moreover, it has been shown that the harvest of both gracilis and semitendinosus tendons compared to the harvest of semitendinosus tendon alone was associated with a higher rate of iatrogenic injury to the IPBSN (58.1% vs. 36.1%) [15] . This difference may be caused by the length of the incision. Moreover, one of the latest cadaveric studies on the anatomy of the IBSN found that an oblique incision resulted in the lowest nerve injury rate. The meta-analysis by Pękala et al. [9] concluded that the vertical incision for hamstring tendons harvest is not recommended as it was associated with a higher risk (51.4%) of iatrogenic injury compared to the oblique (26.0%) and horizontal (22.4%). Those findings have been confirmed by the cadaveric and clinical experimental studies [1617] . Ultrasonography can be very helpful to evaluate the nerve course and its possible anatomical variations. It may be utilized to plan the surgical treatment safely. In addition, ultrasonography allows to localize the nerve lesion and help to choose the appropriate treatment [18] . Moreover, during the diagnostic process of the neurotic pain in the area of the knee joint, it is crucial to remember about other important nerves supplying this region: the lateral femoral cutaneous nerve and anterior cutaneous branches of the femoral nerve. The reported prevalence of IBPSN injuries during knee arthroscopy is considered relatively high. Moreover, the low awareness of such iatrogenic complications among orthopedic surgeons may increase the chance to damage the nerve and delay proper diagnosis and treatment. The surgical excision (proceeded by careful dissection) of the IBSN neuroma is a simple and the most effective treatment method ( Figure 2 ). The common peroneal nerve (CPN) is a branch of the sciatic nerve that separates at the upper level of the popliteal space. In innervates the short head of the biceps femoris muscle (there is no other motor branch located proximally to the proximal fibula). The CPN travels superficially to the lateral head of the gastrocnemius and plantaris muscles as it provides the cutaneous innervation to the lateral aspect of the calf (by the lateral cutaneous nerve of the calf and a communicating branch that anastomoses with the sural nerve). At the level of the proximal fibula, the CPN runs through a fibro-osseous tunnel. The roof of the tunnel consists of the proximal part of the peroneus longus and the intermuscular septum. Then, it courses between the peroneus longus muscle and the fibula, where its' division into two main branches is located [19] . It was described that the normal (distal to the fibular neck) division of the CPN into two main branches can be observed in approximately eight out of ten limbs. However, in the rest of the population, the CPN may bifurcate either between the joint line and fibular neck or even proximal to the line of the joint [20] . It is important that the division of the CPN can be located even as high as in the popliteal fossa, which if not recognized during the surgical dissection cam cause serious iatrogenic injury [21] . First branch, the deep peroneal nerve, courses deep to the peroneus longus and innervates the anterior musculature of the crus. Namely it gives the motor branches to the tibialis anterior, extensor digitorum longus, peroneus tertius, and extensor hallucis longus muscles. It results in the foot dorsiflexion and toe extension. Additionally, it gives sensory innervation to the first interdigital space. The second branch, the superficial peroneal nerve gives the motor innervation to the peroneus longus and brevis muscles. Then, it pierces the deep (crural) fascia. The substantial anatomical variation in superficial peroneal nerve fascial penetration exists. In normal variant (type 1) the superficial peroneal nerve penetrates the fascia as a single trunk. However, in approximately 15% of lower limbs it first bifurcates into the medial dorsal cutaneous and intermediate dorsal cutaneous nerve and then, those branches pierce the crural fascia separately (type 2). In type 3, which is observed in less than 2% of the limbs, the superficial peroneal nerve pierces the fascia and has a course like the medial dorsal cutaneous nerve. In this rare variant, the intermediate dorsal cutaneous nerve is absent [22] . The branches of the superficial peroneal nerve provides sensory innervation to the anterolateral aspect of the distal calf and dorsal foot. It can be damaged during the fasciotomy, arthroscopic procedures, and flap formation. Noteworthy, there is variable branch of the superficial peroneal nerve, the accessory deep peroneal nerve, which may provide motor innervation to the extensor digitorum brevis muscle. The presence of this relatively common (almost 40% pooled prevalence in cadaveric studies) anatomical variant may complicate the diagnostic process of the peroneal neuropathy [19] . Anatomical variations of the biceps femoris muscle may be associated with CPN entrapment [23] . The CPN ran obliquely along the lateral side of the biceps femoris muscle and then superficial to the lateral head of the gastrocnemius muscle or within a tunnel between the biceps femoris and lateral head of the gastrocnemius muscle (Figure 3 ). This anatomical variation may have a clinical significance as an entrapment area of the CPN in the patients in which the pathomechanism is not understood. Pain can be the earliest symptom in peroneal neuropathy, usually preceding sensory changes in a similar distribution. A comprehensive sensory examination is crucial to locate the lesion. The skin of the lower extremity should be careful. Signs of trauma or vascular compromise may help to diagnose the etiology. A reliable bilateral evaluation of the muscle strength must be performed. Insufficiency of dorsiflexion and eversion of the ankle accompanied by the toe extension suggests the peroneal nerve pathology. This is commonly described as a foot drop. It is noteworthy that in some patients, such symptoms may be caused by lumbosacral plexopathy. Importantly, to cause the disturbances of the ankle inversion the tibial nerve must be involved as it innervates the tibialis posterior muscle. In addition, weakness observed in peroneal neuropathy can cause functional gait impairment. The most evident manifestation of peroneal neuropathy is a foot drop. The comprehensive evaluation of lower limb reflexes may contribute significantly to the diagnostic process. The case of pathologic reflexes, suggests the central origin of impaired foot dorsiflexion. The knee x-ray should be obtained to assess possible bone pathologies, tumors, or joint degeneration. As the intraneural ganglion cyst may be the most common etiology of the CPN neuropathy, magnetic resonance imaging (MRI) of the knee can further elucidate a soft tissue tumor [24] . The lumbar MRI can provide evidence of L5 radiculopathy if this diagnosis is suspected after physical examination. Another modality, which helps to visualize the soft tissues in the region of the proximal fibula is ultrasonography. It is inexpensive and easily available, however, requires a certain experience [25] . Electrodiagnostic studies are recommended to confirm the diagnosis of peroneal neuropathy, exclude alternative diagnoses, and determine prognosis. If there is an abnormality in the CPN motor innervation, other muscles supplied by the L5 nerve root must be examined to rule out a radiculopathy, lumbosacral plexopathy, or sciatic neuropathy [26] . Causes of peroneal nerve insufficiency can be grouped into two main categories. In the region of the knee joint, the CPN may be compressed. Such a phenomenon can be caused by normal or pathological structures. Anatomical structures can compress the CPN due to repetitive movements or specific limb positions. The common peroneal nerve can be compressed by the tendinous origin of the peroneus longus, especially in the region where it courses around the proximal fibula and runs via the fibrous tunnel [27] . Moreover, nerve entrapment in the region of the distal part of the biceps femoris was also reported [28] . The common peroneal nerve compression has been found due to kneeling, crossing legs when sitting, prolonged squatting, and lying on inflexible surfaces. Additionally, weight loss, malnutrition, and diabetes may predispose to this condition [28] . Interestingly, peroneal neuropathy has also been reported after weight loss surgery [29] . The hypothesized mechanism was a loss of adipose tissue previously protecting the CPN. In addition, patients who are subjected to long immobilization in the bed after surgical procedures can develop peroneal neuropathy due to the tendency of the lower limb to rest in external rotation of the hip, which predisposes to nerve compression near the fibular head. A preventative program should thus be instituted during hospitalization. The tumors are the second major cause of CPN neuropathy around the knee. Intraneural ganglion cysts are the most common mass lesion causing peroneal neuropathy. Other tumors producing such symptoms include: schwannoma, neurofibroma, osteochondroma, neurogenic sarcoma, focal hypertrophic neuropathy, desmoid tumor, and glomus tumor in order of decreasing frequency [30] . Although it is rare, CPN can be also injured during large surgical procedures, like posterolateral corner reconstruction or high tibial osteotomy [3132]. In patients subjected to the prolonged bed rest, prevention involves frequent repositioning and keeping the lower limbs in a neutral position. In the case of a subtle peroneal nerve injury, strengthening may help with functional recovery. On the other hand, in the case of a complete loss of muscle strength, passive exercises may help to maintain proper ankle range of motion and preclude contracture. An ankle foot orthosis could be useful by keeping the foot in a neutral position to prevent an equinovarus deformity and allowing for a normal gait pattern. If bracing is not effective, the tibialis posterior tendon can be transferred to the dorsum of the foot to restore active dorsiflexion. This is a salvage procedure performed in conjunction with the fusion of the subtalar joint. Elimination of an irritating agent, lesion, or activity is the treatment of choice of peroneal neuropathy. Fast recognition and correct diagnosis are crucial to preserving its maximum function [26] . The rehabilitation program should be planned from the begging of the symptoms. It is important especially in the pandemic situation [33] . If the neuropathy is caused by the presence of the tumor, the lesion should be excised to restore motor function and relieve the pain. Surgical exploration can be considered in an acute traction injury with progressive neurologic loss and pain. Hematoma formation in the nerve sheath or located outside it can also cause these symptoms [34] . The CPN is at risk during total knee arthroplasty especially in severe valgus knees. The pre-release was described as an effective method for CPN protection [35] . Jenkins et al. described a method to help avoid direct injury of the CPN intra-operatively [36] . The aim of this cadaveric study was to use the anatomical axis to determine the location of the peroneal nerve in relations to the tibial centre. In addition, the popliteus tendon was used as an additional point of reference that can be easily visualised during the surgery. In this paper, we have summarized the anatomy of the key nerves that innervate the knee joint and discuss the diagnosis and treatment of injuries and neuropathies associated with these nerves in the context of post-traumatic knee injuries and following reconstructive surgery. More emphasis should be placed on the prevention of such injuries to reduce the impact of long-term neuropathies. Epidemiology of knee injuries among adolescents: a systematic review The impact of knee injury history on health-related quality of life in adolescent athletes Sports, joint injury, and posttraumatic osteoarthritis Genetics in cartilage lesions: basic science and therapy approaches Dom_ zalski, M. 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This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. No data was used for the research described in the article. The authors declare no conflict of interest. No additional information is available for this paper.