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Abstract Olecranon fractures are a common injury in fractures. The tension band technique for olecranon fractures yields good clinical outcomes; however, it is associated with significant complications. In many patients, implants irritate overlying soft tissues and cause pain. This is mostly due to protrusion of the proximal ends of the K-wires or by the twisted knots of the metal wire tension band. Below we described 2 cases of olecranon fractures treated with a unique technique using FiberWire without any metallic implants. Technically, the fragment was reduced, and two K-wires were inserted from the dorsal cortex of the distal segment to the tip of the olecranon. K-wire was exchanged for a suture retriever, and 2 strands of FiberWire were retrieved twice. Each of the two FiberWires was manually tensioned and knotted on the posterior surface of the olecranon. Bony unions could be achieved, and patients had no complaint of pain and skin irritation. There was only a small loss of flexion and extension in comparison with that of the contralateral side, and the patient did not feel inconvenienced in his daily life. Using the method described, difficulty due to K-wire or other metallic implants was avoided.

Schwann cell proliferation in peripheral nerve injury (PNI) enhances axonal regeneration compared to central nerve injury. However, even in PNI, long-term nerve damage without repair induces degeneration of neuromuscular junctions (NMJs), and muscle atrophy results in irreversible dysfunction. The peripheral regeneration of motor axons depends on the duration of skeletal muscle denervation. To overcome this difficulty in nerve regeneration, detailed mechanisms should be determined for not only Schwann cells but also NMJ degeneration after PNI and regeneration after nerve repair. Here, we examined motor axon denervation in the tibialis anterior muscle after peroneal nerve transection in thy1-YFP mice and regeneration with nerve reconstruction using allografts. The number of NMJs in the tibialis anterior muscle was maintained up to 4 weeks and then decreased at 6 weeks after injury. In contrast, the number of Schwann cells showed a stepwise decline and then reached a plateau at 6 weeks after injury. For regeneration, we reconstructed the degenerated nerve with an allograft at 4 and 6 weeks after injury, and evaluated functional and histological outcomes for 10 to 12 weeks after grafting. A higher number of pretzel-shaped NMJs in the tibialis anterior muscle and better functional recovery were observed in mice with a 4-week delay in surgery than in those with a 6-week delay. Nerve repair within 4 weeks after PNI is necessary for successful recovery in mice. Prevention of synaptic acetylcholine receptor degeneration may play a key role in peripheral nerve regeneration. All animal experiments were approved by the Institutional Animal Care and Use Committee of Tokyo Medical and Dental University on 5 July 2017, 30 March 2018, and 15 May 2019 (A2017-311C, A2018-297A, and A2019-248A), respectively., Competing Interests: None

We developed a honeycomb-shaped lyophilized Type I atelocollagen (Honeycomb Collagen: HC) with different pore sizes, and the effectiveness of the honeycomb shape on nerve regeneration was examined. We analyzed neurite outgrowth of dorsal root ganglion (DRG) explants on HC, both in vitro and, with direct implantation of HC into the defects of adult rat spinal cords, in vivo. The neurites of DRGs on HC extended linearly through the pores. HC with a 400 microm-pore size enhanced neurite extension, and YIGSR laminin peptide coating to the HC extended more neurites than fibronectin coating. The HC scaffolds coated with YIGSR were implanted into 2 mm-defects of spinal cords at the level of T8-9. Four weeks after implantation, the implants had degraded and been replaced with self-tissues, repairing the injured site. Neurofilament-positive fibers were observed in the implantation area and passed the borders between the HC and spinal cord stumps. Functionally, a motor-evoked potential was observed in the quadriceps femoris muscle 10 weeks after implantation. The electrophysiological examination showed reconstruction of axon tracts over the implant. This result indicates that our developed honeycomb shape is advantageous for host spinal cord compared to the random pored sponge shape, and that it promotes axonal regeneration after spinal cord injury.