Article

Rotationplasty (Borggreve-Van Nes operation) is a rare limb salvage procedure,
most often applied to children presenting with sarcoma of the distal femur. In
type A1 operation, the distal thigh is removed and the proximal tibia is axially
rotated by 180 degrees , remodeled, grafted onto the femoral stump, and then
prosthetized. The neurovascular bundle is spared. The rotated ankle then works as
a knee. The foot plantar and dorsal flexors act as knee extensors and flexors,
respectively. Functional results may be excellent. Cortical neuroplasticity was
studied in three men (30-31 years) who were operated on the left lower limb at
ages between 7 and 11 years and were fully autonomous with a custom-made
prosthesis, as well as in three age-sex matched controls. The scalp stimulation
coordinates, matching the patients' brain MRI spots, were digitized through a
'neuronavigation' optoelectronic system, in order to guide the transcranial
magnetic stimulation coil, thus ensuring spatial precision during the procedure.
Through transcranial magnetic stimulation driven by neuronavigation, the cortical
representations of the contralateral soleus and vastus medialis muscles were
studied in terms of amplitude of motor evoked potentials (MEPs) and centering and
width of the cortical areas from which the potentials could be evoked. Map
centering on either hemisphere did not differ substantially across muscles and
participants. In the operated patients, MEP amplitudes, the area from which MEPs
could be evoked, and their product (volume) were larger for the muscles of the
unaffected side compared with both the rotated soleus muscle (average effect size
0.75) and the muscles of healthy controls (average effect size 0.89). In
controls, right-left differences showed an effect size of 0.38. In no case did
the comparisons reach statistical significance (P>0.25). Nevertheless, the
results seem consistent with cortical plasticity reflecting strengthening of the
unaffected leg and a combination of cross-education and skill training of the
rotated leg.

Langue : ANGLAIS