Musculoskeletal injuries are the most common injuries in recreational, amateur, and professional sports. Approximately 64% of injuries in recreational sports are musculoskeletal related injuries. Approximately 2 million injuries, 500,000 doctor visits, and 30,000 hepatization in high school students are associated with sports injuries. The National Institute of Arthritis and Musculoskeletal and Skin Diseases has reported that 2.6 million children under 19 years old get treated for musculoskeletal injuries in emergency departments. Hootman et al. reported that more than 50% of sports injuries in college students are in lower extremities with additional injuries reported in upper extremities and back/neck. Historical data of American college football players show an increased number of upper shoulder and arm surgeries. Professional sports data is relatively discreet. Ekstrand et al. has reported that average soccer players sustained 2 injuries per season, leading to missing 37 days in a season. Furthermore, 92% of all muscle injuries are associated with lower limb: hamstring (37%), adductors (23%), quadriceps (19%), and calf muscles (13%). A recent study by Humprey et al. reported professional tennis players to sustain most of their injuries at muscles (24%), tendon (23.4%), and soft tissue bruising (6.5%). Detailed studies have shown that the overuse of musculoskeletal anatomy further adds to injuries and probabilities of the future of reinjuries.
The musculoskeletal healing process involves activation of the cascade of cellular and molecular pathways. The initial response to the injury is the activation of inflammatory cytokines. Acute inflammation is an essential part of the healing process, but chronic inflammation leads to the delayed healing process as well as further damage to the tissue; thus, it is necessary to remove inflammatory cytokines and initiate the regeneration of new tissue. Currently, to restrain the level of inflammation and enhance tissue healing, athletic trainers most commonly use rest, ice compression, and elevation (RICE) method. RICE reduces the inflow of the inflammatory factors, along with reducing the blood flow to the injury site. RICE has limited efficacy in reducing inflammation and improving the rate of tissue regeneration over the healing process. Still, there is a need for add-on therapies to expedite the healing process and tissue regeneration.
Post-injury, the most important concern for an athlete is when to "return to play"? This is a hard question to answer considering the multifactorial factors such as the site of injury, damage sustained, athletes' age, and the number of revised injuries along with other potential health concerns. Doctors and athletic trainers are advised to have a conservative approach, but at the same time, it important to minimize the athlete's off-field time. Thus, it is important to come with more advance, innovative, and non-invasive therapies to accelerate tissue healing.
Ultrasound therapy provides a mechanotransducive localized stimulus to the injury site resulting in increased blood flow, oxygenation, exchange of nutrition, and accelerated tissue healing resulting in inhibition of inflammation. Multiple studies have shown tissue regenerative properties of ultrasound. Ultrasound increases the rate of bone healing by decreasing initial infiltration of cytokines increasing, angiogenesis, chondrogenesis, and bone remodeling. Studies have concluded the application of ultrasound increases the rate of tendon-bone interface healing in preclinical models. Walsh et al. has shown similar trends in anterior cruciate ligament reconstruction.
Ultrasound is a non-invasive therapy with significant data supporting its regenerative efficacy in preclinical studies. The effectiveness of ultrasound is dependent on multiple factors such as duty cycle, intensity, duration, frequency, and energy. While ultrasound therapy has been around for a long time, its transformation to clinical practice has been limited due to the optimization of ultrasound parameters. Low-intensity continuous ultrasound (LICUS) has shown the potential to accelerate the tissue regeneration process significantly. Sustained Acoustic Medicine (SAM) uses LICUS to expedite the healing process and have shown encouraging results in clinical studies. SAM  has been approved for pain management by Food and Drug Management (FDA). Langer et al., in a clinical study (n=30) has shown that after use application of SAM (3MHz, 0.132W/cm2, 18720 Joules) for 4 hours reduced pain by 15% compared to 7% in the placebo group in Trapezium muscle spasm. They also showed 52% (p<0.05) improvement in the visual analog score (VAS) in rotator cuff pain, 40% (p<0.03) pain reduction in osteoarthrosis patients (N=47), and 4.28 point VAS (p<0.001) decrease in tendon pain relief and recovery (N=25) after 6 weeks of treatment. Lewis et al. has reported an up to 1point increase in Global Rating of Change (GROC) score and a 25% reduction in VAS reduction after 10 days of SAM treatment in chronic myofascial pain. The objective of this study is to evaluate the effects of SAM in sports-related injuries as an adjuvant therapy to athletes when conservative treatment fails.