[First results with a resorbable MgYREZr compression screw in unstable scaphoid fractures show extensive bone cysts].

Osteosynthesis with headless compression screws is an established treatment option for unstable scaphoid fractures. Common implants are made of titanium alloy or steel and usually remain in place. Due to implant density and ferromagnetic properties, artefacts are common in postoperative imaging procedures, e.g. MRI. Now resorbable implants made of magnesium alloy (MgYREZr) have become available. They have biomechanical properties equivalent to human bone and may be used as an alternative to the nonresorbable screw systems.5 patients with acute scaphoid fractures were treated with a double-threaded screw made of MgYREZr. The fractures included three type A2 fractures, one type B2 fracture, and one type B3 fracture. All patients underwent clinical and radiological follow-up postoperatively, 6 weeks, 3 and 6 months and 1 year after surgery. ROM, gross grip strength and pain (VAS) were documented. The Modified Mayo Wrist Score was used. Standard X-rays of the wrist were taken preoperatively and at all follow-up visits. A CT scan was performed at least before and three months after surgery. In all X-rays malunion, resorption of the implant, implant loosening, cysts and bone healing (bridging trabecular structures) were described.All patients had a very good wrist score (95-100 points) after one year. There were no clinical complications. However, the X-rays revealed extensive resorption cysts in 3 out of the 5 patients. It was only after 6 months that the fractures were consolidated enough to allow physical work. Due to this considerable osteolysis, we did not include any further patients. Due to the observed extensive bone cysts and the long time period for bone healing, MgYREZr compression screws are currently not recommended for clinical use in scaphoid fractures. Further fundamental research is necessary.