Effect of Additional Treatment With NMES After Achilles Tendon Rupture

BACKGROUND:

There is limited knowledge about how calf muscle performance and tendon elongation affect the patient's discomfort or ability to return to previous activity levels after an Achilles Tendon rupture. Tendon elongation can cause a changed recruitment pattern of the different parts of the muscle complex triceps surae. There is some evidence that treatment with Neuromuscular Electrical Stimulation (NMES) can improve postural balance by stimulating the calf muscles in elderly people with impaired balance. A newly published study concluded that NMES treatment the first 12 weeks after an ATR, did not have any impact on calf circumference or patient-reported outcome the first 12 weeks after the injury.

Studies have shown that only 20-40% of patients are able to return to the same level of physical activity as before the injury. Although patients return to full participation in sports, their level of performance is often adversely affected. Obviously, there can be different reasons for this. In a newly published study, it was concluded that joint power distribution during a drop countermovement jump was affected by fear of reinjury as long as 2 years after an ATR. However, there is still a lot to explore about if an improved physical function in the injured calf muscle may decrease the fear of re-injury and therefore positively affect the ability to return to previous physical activity level after an ATR. Therefore, new treatments with the goal to increase the possibility to return to the same physical level as before the injury are very much needed.

An ATR can lead to reduced strength development in the ankle with simultaneous increased load development in the knee joint in the injured leg for as long as 6 years after the injury. Reduction in strength and endurance in the calf muscle has been shown to persist long after the injury. Exhaustion of the lower leg muscles affects the valgus moment in the knee as well as kinematic variables in athletes during vertical jumps, which may affect the risk of knee injury. However, there is a lack of knowledge about how lower leg function, biomechanics and muscle recruitment are affected in patients after an ATR. It is also unknown how this injury affects the healthy limb and perhaps increase the risk of overload injuries in other parts of the body.

HYPOTHESIS:

Additional treatment with NMES in early stages after an Achilles Tendon rupture have a positive impact on lower leg function both in the short and long term.

PURPOSE AND SPECIFIC GOALS:

An overall aim of the project is to, in a randomized controlled trial, explore what impact a new treatment method with NMES in the early stages after an ATR may have on calf muscle performance, tendon length, jumping ability, biomechanical variables and patient reported outcome both in the short and long term after the injury.

There will also be focus on how the non-injured limb may be affected of an Achilles tendon rupture. This new knowledge can be helpful in the clinical setting to

1. individualize and optimize patients' treatment and rehabilitation
2. avoid overuse injuries, both in the injured and healthy limb The goal will be to guide the patient return to the same, or higher level of physical activity as before the injury.

OBJECTIVES:

• To explore if additional treatment with NMES during the first 3-8 weeks after an ATR can improve calf muscle function, biomechanical variables, tendon lengthening and patient-reported outcome both in short an long term. The design of this study is a Randomized Controlled Trial (RCT).
• To evaluate the biomechanics of the ankle, knee and hip during walking, running and jumping in both limbs in two groups of patients one year after an ATR. One group has been treated with NMES 3-8 weeks after the injury and the other group has not.

METHOD The design of this study is a randomized controlled trial. A power calculation (p <0.05, power 80%) showed that 28 patients who receive and 28 who do not receive treatment with NMES are needed to be able to show a clinically important difference of 10% in heel-rise height. A total of 70 patients with ATR will be included and randomized to receive or to not receive additional therapy with NMES during the first 3-8 weeks after their ATR.

Four electrodes connected with the NMES equipment will be attached on the patients ́ calf on the injured leg and they will use the equipment in their home two times a day á 15 minutes for six weeks, that is 3-8 weeks after the injury.

Primary outcome will be the heel-rise height during the heel-rise work test. Standardized seated heel-rise as well as single-leg standing heel- rise will be evaluated 3, 6 and 12 months after the injury in both the injured and the healthy limb. The heel-rise work test will be evaluated with a linear encoder connected to the software MuscleLab®.

Tendon length will be evaluated with ultrasound 8 weeks and 3, 6 and 12 months after the injury. The measurement is found to be reliable and valid. The tendon length will be evaluated with ultrasonography with extended field of view using a wideband array linear probe (5.0- 13.0 MHz). The B- mode at 10 MHz and a depth of 3 cm will be used to record the images.

One year after the injury, kinematic and kinetic variables together with EMG will be evaluated during walking, running and jumping. For collection of the biomechanical data, 16 7+ cameras and 4 force plates will be used. This new equipment is available in a new motional analysis lab at our research unit. Fifty-five reflectors will be attached on the patients´ body to be able to detect segmental movements. EMG electrodes on the medial and lateral Gastrocnemius, Soleus and Tibialis anterior muscles will also be attached on the patient in order to measure how the muscles are recruited in the different activities. Both healthy and injured sides will be analyzed.