We reviewed our initial seven-year experience
with a non-invasive extendible prosthesis in 34 children with primary bone
tumours. The distal femur was replaced in 25 cases, total femur
in five, proximal femur in one and proximal tibia in three. The
mean follow-up was 44 months (15 to 86) and 27 patients (79%) remain
alive. The prostheses were lengthened by an electromagnetic induction
mechanism in an outpatient setting and a mean extension of 32 mm
(4 to 80) was achieved without anaesthesia. There were lengthening
complications in two children: failed lengthening in one and the
formation of scar tissue in the other. Deep infection developed
in six patients (18%) and local recurrence in three. A total of
11 patients required further surgery to the leg. Amputation was
necessary in five patients (20%) and a two-stage revision in another.
There were no cases of loosening, but two patients had implant breakage
and required revision. The mean Musculoskeletal Tumor Society functional
score was 85% (60% to 100%) at last known follow-up. These early
results demonstrate that the non-invasive extendible prosthesis
allows successful lengthening without surgical intervention, but
the high incidence of infection is a cause for concern.