Variation in the Distribution of the Middle Trunk: Potential Contraindication for C7 Harvest?

Experience with direct repairs of the opposite C7 with the lower trunk has made restoration of useful finger flexion a realistic objective in the management of total posttraumatic brachial plexus injuries, particularly in younger individuals. This entails a detailed exploration of the injured brachial plexus with certain essential maneuvers for proximal mobilization of the medial cord.[1] It is based on the premise that the lower trunk is discrete and communicates with the posterior cord via its posterior division alone. However, we have noted a distinct contribution from the middle trunk to the lower trunk on three consecutive occasions ([Fig. 1]). Further distal dissection revealed its continuity with the medial root of the median nerve. A similar anatomical distribution was anticipated on the uninjured side. The fear of potential deficit in the motor territory of the median nerve following harvest of the opposite C7 deterred us from using the technique in these three patients. The anomalies of the middle trunk have been reported by Woźniak et al in the cadaveric study in fetuses.[2] We communicated our observations to the original author of this technique (Dr. Shufeng Wang)[3] [4] who confirmed having had similar cases. However, in his experience, this branch of the C7 continued to the lateral root of the median nerve and sectioning it did not produce significant deficit.