Background: Rectus femoris tendon transfer is performed in patients
with cerebral palsy to improve knee flexion during walking. This procedure
involves detachment of the muscle from its insertion into the quadriceps
tendon and reattachment to one of the knee flexor muscles. The purpose of the
present study was to evaluate the muscle-tendon geometry and to assess the
formation of scar tissue between the rectus femoris and adjacent
Methods: Magnetic resonance images of the lower extremities were
acquired from five subjects after bilateral rectus femoris tendon transfer. A
three-dimensional computer model of the musculoskeletal geometry of each of
the ten limbs was created from these images.
Results: The three-dimensional paths of the rectus femoris muscles
after transfer demonstrated that the muscle does not follow a straight course
from its origin to its new insertion. The typical muscle-tendon path included
an angular deviation; this deviation was sharp (>35°) in seven
extremities. In addition, scar tissue between the transferred rectus femoris
and the underlying muscles was visible on the magnetic resonance images.
Conclusions: The angular deviations in the rectus femoris
muscle-tendon path and the presence of scar tissue between the rectus femoris
and the underlying muscles suggest that the beneficial effects of rectus
femoris tendon transfer are derived from reducing the effects of the rectus
femoris muscle as a knee extensor rather than from converting the muscle to a
knee flexor. These findings clarify our understanding of the mechanism by
which rectus femoris tendon transfer improves knee flexion.
Level of Evidence: Therapeutic study, Level IV (case
series [no, or historical, control group]). See Instructions to Authors for a
complete description of levels of evidence.