Magnetic Resonance Imaging of Skeletal Muscle Geometry and Motion After Surgery

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Abstract

The goal of this dissertation was to evaluate the in vivo function of muscles in persons with cerebral palsy after surgical transfer of the rectus femoris. Rectus femoris transfer is frequently performed in persons with cerebral palsy who walk with a stiff-knee gait. In this surgery, the rectus femoris muscle is detached from its insertion into the quadriceps tendon and is reattached to one of the knee flexor muscles behind the knee. Rectus femoris transfer is performed to convert the rectus femoris muscle from a knee extensor to a knee flexor thereby allowing the muscle to assist knee flexion during walking. However, outcomes of this procedure are variable, and it is not known if the surgery successfully converts the muscle to a knee flexor.

We hypothesized that scar tissue may form after surgery and adhere the rectus femoris to surrounding tissues in some patients. To test this hypothesis dynamic and static magnetic resonance imaging was used to study the motion and geometry of the rectus femoris muscle in 10 unimpaired control subjects (10 limbs) and 6 subjects (10 limbs) after rectus femoris transfer. The motion of muscle tissue within the rectus femoris and vastus intermedius was measured during knee extension using cine phase contrast magnetic resonance imaging. Displacements of the vastus intermedius during knee extension were similar between control and tendon transfer subjects. In the control subjects, the rectus femoris muscle consistently moved in the direction of the knee extensors and displaced more than the vastus intermedius. The rectus femoris also moved in the direction of the knee extensors in the tendon transfer subjects; however, the transferred rectus femoris displaced less than the vastus intermedius. These results suggest that the rectus femoris is not converted to a knee flexor after its distal tendon is transferred to the posterior side of the knee, but its capacity for knee extension is diminished by the surgery.

Three-dimensional muscle paths reconstructed from magnetic resonance images showed unexpected angulation and distal atrophy in the rectus femoris muscle after transfer. Further, assessment of the images demonstrated that scar tissue was present to some extent in all subjects after rectus femoris transfer. Despite these findings, several subjects demonstrated post-operative improvements in knee flexion during walking. The measurements of muscle displacements, angular deviation of the rectus femoris muscle path after transfer, and scar tissue visible on magnetic resonance images in these subjects suggest that scar tissue tethers the rectus femoris to the underlying vastus medialis postoperatively.

This dissertation demonstrates that magnetic resonance imaging techniques can be used to advance our understanding of muscle motion and geometry in healthy subjects and subjects with cerebral palsy after surgery.

Cited Works (6)

Year	Entry
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