Summary
Achilles tendon rupture (ATR), a common injury that affects active individuals, has increased 10-fold in the past
few decades. Lower-leg functional deficits include decreased heel-rise height, heel-rise work, concentric strength
power, reduced plantar flexion strength, and decreased ability of the ankle to generate power. These deficits
persist as far out as 14 years after injury. The cause of long-term functional deficits remains unclear and is
thought to be multifactorial. Structural changes in the tendon-muscle unit after ATR are strongly related to deficits
in plantarflexion function. Specifically, ATR results in long-term tendon elongation, increased tendon area,
altered mechanical properties, and reduced calf muscle volume. These structural changes rapidly develop over
the first weeks of recovery, slowly progress for a few months after injury, and change very little thereafter. The
rapid initial development of muscle and tendon abnormalities coincides with the period of no weight bearing or
partial weight bearing of current rehabilitation protocols. In this study, we propose to use neuromuscular electrical
stimulation (NMES) to provide muscle activity and mechanical stimulus to the healing tendon during the first
weeks of recovery to minimize the large initial decline. NMES can positively impact several of the factors affecting
recovery from ATR, and has been successfully applied as part of rehabilitation protocols for knee surgery to
preserve muscle volume and strength. Therefore, NMES can attenuate muscle atrophy during the first weeks of
recovery after ATR repair surgery. Early controlled loading improves mechanical properties of the Achilles tendon
after rupture. Additionally, NMES significantly reduces the risk of deep vein thrombosis, a possible complication
during the recovery from ATR.
The objective of this study is to develop and evaluate a NMES rehabilitation protocol for surgically-treated
Achilles tendon ruptures. This study is divided into two aims. Aim 1 will determine parameters of the NMES
protocol based on measurements of tendon mechanical properties. Aim 2 will evaluate the feasibility and
preliminary efficacy of NMES protocol as a self-applied intervention.
Functional deficits after ATR are common and persist long after the injury. The majority of the abnormal
changes in muscle and tendon properties occur during the first weeks of recovery. The purpose of this protocol
is to supplement muscle activity and provide mechanical stimulation to the tendon for 6 weeks after repair. The
fundamental concept of the proposed protocol is to stimulate small portions of the calf muscles to induce
significant contraction in that region, while applying moderate loading to the tendon. We will evaluate the effect
of proposed protocol in early functional outcomes that are predictive of longer-term outcomes. NMES is a
technology widely available in physical therapy and rehabilitation centers. Consequently, the proposed protocol
can be easily adopted and incorporated as part of routine care for ATR.