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Background: Activation of extracellular signal-regulated protein kinase (ERK), a member of mitogen-activated protein kinase (MAPK) family, has been proposed to mediate neurite outgrowthpromoting effects of several neurotrophic factors in vitro. However, the precise activity of ERK during axonal regeneration in vivo remains unclear. Peripheral axotomy has been shown to activate ERK in the cell bodies of primary afferent neurons and associated satellite cells. Nevertheless, whether ERK is also activated in the axons and surrounded Schwann cells which also play a key role in the regeneration process has not been clarified.

Lateral femoral cutaneous nerve (LFCN) generally emerges from the pelvis behind the inguinal ligament (IL) to the thigh. Because of its proximity to the anterior superior iliac spine (ASIS) and hip joint, the LFCN is prone to injuries during various procedures. Anatomy of this nerve is highly variable among studies. Moreover, measurement data regarding its branches including the differences between genders and sides are still lacking. This study was, therefore, done to clarify these issues. Eighty-five thighs from 43 cadavers of both genders were dissected at the inguinal region. Distances from each branch of the LFCN to palpable landmarks: the ASIS, pubic tubercle (PT) and femoral artery (FA) were measured along the IL. Up to four branches of the LFCN were found; however, the single trunk was the most common form (>65%). The common site of this pattern on the IL was within 2 cm medial to the ASIS but could be present at over 6 cm. The distances in case of bifurcation were mostly comparable to those of the single trunk. In contrast, the values varied considerably in the cases with three or more branches (three cases). Regarding side and gender, asymmetry in the branching pattern was found in one fourth of specimens. However, only some minor differences between genders or sides in the measurement data were seen. These findings suggest that asymmetry and multiple branches of the LFCN should be concerned. The measurement data are also useful for localizing the LFCN with higher accuracy.

The superficial peroneal nerve (SPN) is one of the two main branches of the common peroneal nerve, which become cutaneous nerve on the lateral side of distal leg and dorsum of foot. The use of SPN as nerve graft has been introduced; however, important data regarding the morphometric anatomy of this nerve and its branches, medial and intermediate dorsal cutaneous nerves (MDN and IDN, respectively) to support this application remain incomplete. Eighty-five legs of cadavers were dissected and the branching pattern was classified into Type 1 (penetration of the main trunk of SPN from the deep fascia) or Type 2 (separate penetration of the MDN and IDN). The length of SPN, MDN and IDN from the penetration points until before subsequent branching was measured. In addition, the penetration points were located by referring to the intermalleolar line and the lateral malleolus. Type 1 was found in the majority of specimens independent of gender (71.8%). Asymmetry in the branching pattern was observed in nine cases (20.9%). The average length of the SPN, MDN and IDN without branches was 7.7, 8.1 and 5.5 cm, respectively. The penetration points of the SPN, MDN and IDN were located 5.1, 7.6 and 5.5 cm above the intermalleolar line, respectively. These data are important for using the SPN as a graft.

The lateral antebrachial cutaneous nerve (LACN) is the terminal sensory branch of the musculocutaneous nerve supplying the lateral aspect of forearm. Because of its close proximity to the biceps brachii tendon (BBT), the lateral epicondyle (LE), and the cephalic vein (CV), surgery and venipuncture in the cubital fossa can injure the LACN. Measurement data regarding the relative anatomy of LACN are scarce. We, therefore, dissected 96 upper extremities from 26 males and 22 females to expose the LACN in the cubital fossa and forearm. The LACN consistently emerged from the lateral margin of BBT. It then pierced the deep fascia distal to the interepicondylar line (IEL) in 84.4% with mean distances of 1.8 ± 1.1 and 1.2 ± 0.9 cm (male and female, respectively). At the level of IEL, the LACN in all cases was medial to the LE (5.9 ± 1.1 cm male and 5.2 ± 0.9 cm female). Two types of branching were observed: single trunk (78.1%) and bifurcation (21.9%). Asymmetry in the branching pattern was observed in 6 males and 1 female. Concerning the relationship to the CV, the LACN ran medially within 1 cm at the level of IEL in 78.7%. Moreover, in 10 specimens, the LACN was directly beneath the CV. In the forearm, the LACN tends to course medial to the CV. Significant differences in the measurement data between genders but not sides were found in some parameters. These data are important for avoiding LACN injury and locating the LACN during relevant medical procedures.

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These results suggest the crucial role of ERK in nerve regeneration but not sensory neuronal loss after trauma.