Abstract
The best surgical choice for distal femur osteosarcoma in skeletally immature patients
remains controversial. A fixed hinged knee prosthesis has been designed to preserve
the growth plates in the adjacent tibia, expecting tibial growth to be continued.
This study aims to report the (1) clinical outcomes after prosthetic replacement,
(2) postoperative complications, and (3) length of discrepancy of the operative tibia
with the unaffected tibia. Thirty-four skeletally immature patients (averaged 9 years
at surgery; range, 5–12 years) with distal femoral osteosarcoma underwent placement
of this hinged knee prosthesis between January 2015 and August 2018. Postoperative
function and complications were assessed. Length discrepancy was measured using a
series of full-length standing anteroposterior radiographs of the bilateral lower
extremity. The average follow-up duration was 34 months (2.8 years). In the last follow-up,
four patients expired because of pulmonary metastasis. Two patients presented with
local recurrence of the soft tissue. Postoperatively, the flexion range of the knee
joint range was between 100 and 130 degrees, with an average of 115.2 degrees. The
mean functional score of living patients evaluated using the Musculoskeletal Tumor
Society scoring system was 89.2% (range, 76.7–100%). Types 1 (three patients), 2 (one
patient), 3 (two patients), and 5 (two patients) complications exist. Among them,
three patients received revision surgery. The proximal tibial physis still grew after
surgery, with an average of 74.3% (range, 30–100%) growth potential compared with
the unaffected proximal tibial physis. Moreover, 27 children exhibited tibial length
discrepancy compared with the contralateral tibia, and the mean discrepancy in tibial
length was 1.1 cm (range, 0.2–3.1 cm). This hinged knee prosthesis can keep the growth
potential in the adjacent tibia, provides satisfying functional outcomes, and has
a lower postoperative complication rate. Thus, it could serve as an alternative intervention
for distal femoral osteosarcoma in skeletally immature patients.
Keywords
osteosarcoma - tumor prosthesis - limb salvage - children
