To determine the gross structural alterations of the nailed bone (femur or tibia) after the removal of an intramedullary nail (IMN).Prospective, consecutive, patient series.Academic, level 1 trauma center.Eighteen patients (14 patients with a femoral and 4 patients with a tibia nail) underwent an IMN removal from their femur or tibia.Every patient had a spiral computed tomography scan and a plain X-ray study, immediately after the nail removal and also at their latest follow-up (24-30 months). The 4 patients with a tibia nail were additionally examined using a peripheral quantitative computed tomography study at their latest follow-up.Structural alterations of the nailed bone (femur or tibia) after the removal of the IMN in asymptomatic patients.An intramedullary shell of compact bone was demonstrated around the nail track. This new bone was apparent on plain radiographs in all of the patients. Peripheral quantitative computed tomography study revealed that the density of the bony ring was similar to that of subcortical bone. The histologic examination of the intramedullary shell of one of our patients suggested that the bony ring was made of cortical bone.Intramedullary nailing may enhance new cortical bone formation within the bone marrow cavity. This 'cortical bone' still exists more than 2 years after implant removal. Nail insertion also causes thickening of the normal cortex at the sites of nail-cortex contact where loads are transferred from the nail to the cortex.