A novel polyglycolic acid (PGA)-collagen tube has been available in Japan since March 2013, and the development of high-resolution ultrasonography has recently allowed detailed evaluation of nerves. The purpose of this study was to report the clinical outcomes and evaluations of in-vivo changes under high-resolution ultrasonography for treatment using PGA-collagen tube for painful chronic nerve injury.Four patients underwent surgical management of peripheral nerve neuroma, with nerve defects after neuroma resection reconstructed using PGA-collagen tube. Mean duration of follow-up was 30 months. Patients were surveyed to determine visual analog scale scores for pain before surgery and at final follow-up. At final follow-up, sensory function was evaluated using the Semmes-Weinstein test, static 2-point discrimination (2PD), and moving 2PD. Furthermore, we performed ultrasonography for all patients every 1 month after surgery.In all cases, resting pain, radicular pain, and dysesthesia were improved immediately after the operation and remained improved until the last follow-up. At the time of final follow-up, the Semmes-Weinstein test was red in 2 cases and blue in 2 cases. Mean static 2PD was 15.5 ± 5.3 mm and mean moving 2PD was 11.5 ± 5.3 mm. Ultrasonography revealed that the PGA outer wall had disappeared by 3 months postoperatively, and a hypoechoic linear shadow bridged the proximal and distal stumps. Swelling of the junction between nerve and nerve conduits was revealed at 4 months after surgery and remained until last follow-up.All patients were very satisfied with pain relief, but recovery of sensory function was insufficient. Ultrasonographic evaluation after using PGA-collagen tube for painful chronic peripheral nerve injury was useful for observing in-vivo changes.Therapeutic IV.