Non-prosthetic peri-implant fractures: classification, management and outcomes.

INTRODUCTION: Non-prosthetic peri-implant fractures (NPPIFs) are an under-reported entity. Management is challenging because of alterations in anatomy, the presence of orthopaedic implants and phenomena such as stress shielding, disuse osteopenia and fracture remodeling. The aims of this paper were to review patterns of injury, management and outcomes and to propose a classification system to aid further research.

MATERIALS AND METHODS: This study is a multi-centered retrospective case series. Patients were identified from the orthopaedic department trauma databases of public hospitals in Singapore and individual surgeon case series of members of the Singapore Orthopaedic Research Collaborative (SORCE) group.

RESULTS: We collected a series of 60 NPPIFs in 53 patients. 38 fractures involved the femur, 12 the radius/ulna, 5 humeri, 3 tibia/fibula and 1 clavicle. 39 patients had fractures around plates and screws, 12 around nails, and 3 around screws. Fractures were managed with a variety of surgical techniques. Six patients had surgical complications with refracture in four and non-union in two cases. Two patients had multiple refractures (total 12 additional fractures). All surgical complications required further surgery. Three patients had deep vein thrombosis and one patient died of post-operative pneumonia. Fractures were classified according to the initial implant (plate or nail), the position of the new fracture relative to the original implant (at the tip or distant) and the status of the original fracture (healed, not healed or failing). Surgical strategies for common subtypes were reviewed.

CONCLUSIONS: This study represents the largest series in the literature. NPPIFs are a challenging clinical problem with a high rate of post-operative complications. They are distinct from peri-prosthetic fractures and should be understood as a separate entity. We, therefore, propose a novel classification system. Further research is needed to determine the optimal treatment for the various subtypes.

LEVEL OF EVIDENCE: Therapeutic Level IV-case series.