Efficacy of spherical shaft rotary-hinge knee prosthesis in children with osteosarcoma of the distal femur

CHI Chen-shen; SHEN Jia-kang; ZUO Dong-qing; WANG Hong-sheng; SUN Wei

doi:10.3969/j.issn.2095-252X.2025.05.003

Abstract：Objective To modify the design of spherical axial knee prosthesis with retained physeal,and verify its clinical efficacy in treating osteosarcoma of the distal femur in children.Methods Retrospectively collected children who underwent knee replacement for distal femoral osteosarcoma in the Department of Bone Oncology of Shanghai First People's Hospital from April 2021 to September 2023.10 males and 5 females,with the mean age(11.3±1.7)years(range:8-15 years)and height(153.5±11.0)cm(range:138-173 cm),were examined on admission by X-rays,CT chest,MRI,full-length films of both limbs and CTA of lower limbs.Biopsy confirmed osteosarcoma of the distal femur,and after standardized neoadjuvant chemotherapy,all of them underwent spherical-axis knee prosthesis replacement with preservation of the epiphysis.At 1,3,6,and 12 months after surgery,full-length X-rays of both lower limbs and chest CT were performed,and limb function was measured using the American Musculoskeletal Tumor Society's MSTS 93 scoring standard and knee ROM.The tibia and lower limb lengths were obtained at the preoperative and the last follow-up,and the tibia growth lengths of the affected and the healthy sides were measured by the first and last difference,and the ratio of the growth lengths of the tibia was calculated bilaterally to evaluate the proximal tibia growth lengths.The growth potential of the proximal tibia was assessed.Postoperative complications were recorded at the last follow-up.Results Surgery was successfully completed in all 15 cases;operation time:120-240 min,mean(174.6±36.8)min;intraoperative bleeding:200-350 ml,mean(252.7±46.8)ml;resection length of tumor segment:9.9-21.0 cm,mean(13.6±3.4)cm;reconstruction length:10.0-21.4 cm,mean(15.9±3.1)cm;follow-up:8-24 months,mean(10.6±3.9)months;MSTS 93 score:21-28 points,mean(26.1±2.0)points;knee ROM measurement,active activity(AROM):100°-140°,mean(122.7±12.4)°;passive activity(PROM):100°-160°,mean(142.0±13.8)°;growth percentage of the proximal tibial epiphysis of the children:66.7%-100.0%,mean(88.7±10.6)%.Among them,6 cases were 100%.15 cases did not have tumor recurrence during the follow-up period,and no complications such as infection,aseptic loosening,or fracture of the prosthesis occurred.Conclusions The modified epiphyseal ball-and-socket knee prosthesis is a viable option for children with malignant tumors of the distal femur who have a good early follow-up outcome.It can effectively improve the LLD of the lower limb in children.