A press-fit tibial smooth stem may preserve proximal tibial physeal growth after expandable prosthesis reconstruction following resection of distal femur in children with bone sarcoma

Purpose The distal femoral and proximal tibial physes contribute to more than two-thirds of the total longitudinal growth of the lower limb. Reconstruction with expandable prosthesis after primary bone tumor resection of the distal femur in children aims to restore limb length of the femur due to the sacrifice of the distal femur physis. However, distal femur expandable prosthesis may also lead to disturbance in the proximal tibial physeal growth due to the potential impact of the tibial stem on the proximal tibial physis. Few studies investigated whether an uncemented press-fit tibial smooth stem can preserve proxi-mal tibial physeal growth, but their findings are controversial and limited. Therefore, we analyzed if a press-fit tibial smooth stem may preserve proximal tibial physeal growth after expandable prosthesis reconstruction following primary bone tumor resection of the distal femur in children. Methods We retrospectively analyzed 14 children with distal femur sarcoma who underwent reconstruction with an expand-able prosthesis and a press-fit tibial smooth stem: 7 males and 7 females, with a median age of 9 years (range, 5 to 15 years). Proximal tibial physeal growth was measured on immediate postoperative and standing panoramic radiographs of both lower limbs, comparing the treated tibia with the contralateral tibia. Outcomes included absolute growth of the proximal tibial physis (mm), relative growth (%) versus the contralateral side, and final tibial asymmetry (mm). Results All 14 children showed measurable growth of the proximal tibial physis after reconstruction with an expandable prosthesis and a press-fit tibial smooth stem. The mean proximal tibial growth was 40.9 mm (median, 49.2 mm; range, 3.1-77.0 mm). The median tibial asymmetry length between the treated and contralateral tibia was 16.0 mm (range, 1.2-24.7 mm), and the mean tibial asymmetry was 12.7 mm. The mean proximal tibial physeal relative growth was 81% (range, 27%-160%) compared to the contralateral tibia. Only three of 14 children (21%) developed a tibial length asym-metry >= 20 mm. The mean duration of proximal tibial physeal growth was 4.9 years (range, 2.0-12.8 years), with a median of 4.4 years. Conclusions The use of a press-fit tibial smooth stem in children with primary bone tumors who underwent distal femoral resection and reconstruction with an expandable prosthesis allowed continued proximal tibial physeal growth. Based on these findings, we may suggest the use of press-fit tibial smooth stems to preserve tibial physeal growth potential and reduce the risk of limb discrepancy in children treated with distal femur expandable prostheses.