A fracture of the distal radius with an associated injury to the ulnar nerve is rare. The management of the ulnar nerve lesion is unclear. We present a patient with a closed distal radius fracture related to an injury to the ulnar nerve associated with diminished sensation and a claw deformity. This was assessed by ultrasonography (US) that showed the nerve to be in continuity without any evidence of compression. The nerve was deviated towards the volar side at the distal end of the ulna and was enlarged at the same point. Open reduction and internal fixation was performed for the fracture. Emergent nerve exploration was not performed. The function of the ulnar nerve was completely restored at 16 weeks after injury. In cases presenting with ulnar nerve injury, we recommend US to evaluate the condition of the ulnar nerve. Nerve exploration should be performed when neurological deficits were found on US or symptoms did not recover over 4 months observation. Level of Evidence: Level V (Therapeutic)

Perineural hydrodissection is a minimally invasive technique using an injection of fluid to dissect the perineural plane and tissue space. This report describes a case of palsy of the descending branch of the posterior interosseous nerve (PIN) which was recovered by targeted ultrasound-guided perineural hydrodissection. Ultrasonographic examination was performed, and multiple stenotic lesions interrupted by hyperechoic bands within the fascicles of the PIN were found. Using ultrasonography, perineural hydrodissection was performed four times every other week. Fifteen weeks after the first hydrodissection, there was no restriction in the patient’s thumb and fingers movement, and ultrasonography revealed that multiple stenotic lesions had improved. Today, surgical treatment is recommended for patients with complete nerve constriction. However, there is no standardized approach for patients with incomplete or without nerve constriction. Ultrasound-guided perineural hydrodissection is a noninvasive and easy method. This procedure could be a useful diagnostic and therapeutic modality for the management of the disease.