Periprosthetic humeral fractures: mechanisms of fracture and treatment options.

In 20 patients, 21 periprosthetic humeral fractures were reviewed retrospectively. The mean follow-up time was 27.1 months. Mild osteopenia was present in 45% of the patients, whereas 30% had severe osteopenia. Five mechanisms of fracture were identified, including 3 intraoperative causes that are avoidable. Treatment with stable intramedullary fixation utilizing the humeral stem and cerclage wiring provided superior results in terms of time to union, adverse effect on rehabilitation, and occurrence and severity of surgical complications. Diaphyseal fractures that were treated with standard stem arthroplasty with or without supplemental fixation had a longer time to fracture union, a higher complication rate, and prolonged rehabilitation. Fractures of the proximal humeral metaphysis can be treated with standard stem arthroplasty and cerclage wiring if the stem extends distal to the fracture site by at least 3 cortical diameters. Anatomic reduction of fractures treated by surgical means results in shorter healing times. Cast or brace immobilization can be used for management of postoperative fractures that occur distal to a well-fixed and stable prosthetic stem. Cast or brace immobilization results in fracture union but rehabilitation may be greatly impaired, and there is an increased risk of complications associated with immobilization of the extremity. Long-stem intramedullary fixation with cerclage wiring is the preferred surgical option for treatment of unstable humeral shaft fractures.