Radiographic Risk Factors For Interprosthetic Femur Fractures.

PURPOSE: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are among the most common orthopaedic procedures performed in the United States annually. As the number of patients undergoing these procedures increases so too does the incidence of periprosthetic femur fractures. A number of these periprosthetic fractures occur between two ipsilateral implants, so-called interprosthetic fractures. Recent biomechanical data has challenged the importance of these interprosthetic distances, relating that cortical width and osteoporotic bone are more closely correlated with fracture than interprosthetic distance. The purpose of the current study is to further define the presence of osteoporosis, cortical width (CW) and medullary diameter (MD) as potential predictive factors for interprosthetic femur fractures.

METHODS: Current Procedural Terminology (CPT) codes were used to identify a cohort of patients undergoing operative treatment for periprosthetic femur fractures. A review of the medical records identified 23 patients (5 male / 18 female) with a femur fracture between two intramedullary implants. CPT codes were also used to identify a second cohort of 25 patients (8 male / 17 female) having undergone ipsilateral THA and TKA. The intact femoral isthmus was identified radiographically and the MD and CW (mm) were measured. A ratio of MD to CW was also determined. Chart review was undertaken and any diagnosis of osteoporosis was recorded. An independent sample T-test was performed comparing the mean MD, CW, and the ratio of MD:CW for these groups. Significance was set at p.