One year outcome of ultrasound (US)-guided percutaneous treatment of Achilles tendinopathy: results of a randomized controlled trial

PURPOSE: Achilles tendon (AT) is the largest tendon of the human body. It originates from the junction of gastrocnemius and soleus muscles' distal tendons in the middle of the calf to and runs distally, gradually assuming a crescent shape, and inserts on the calcanear posterior tuberosity ( Fig. 1 ). It is provided with a fibrous sheath called paratenon. Its lenght can vary from 3 to 15 cm. With the muscular contraction, the AT promotes the plantar flexion of the foot necessary to stand on the toes, walking, running and jumping. During locomotion this structure is continuously stressed: with running or sprinting, each Achilles tendon undergoes to significant load transfer, from 7 up to 12,5 times the body weight. An important feature is that the middle third of the AT presents a hypovascular area from 2 to 6 cm above the calcanear insertion, thus being more exposed to repetitive microtraumas that can lead to cronic degenerative changes without signs of peritendinous inflammation. This pathological condition, if untreated, can lead to major tendinous injuries and rupture. Achilles tendinopathy (also called Achilles tendinosis) is a common cause of lower calf pain, affecting 2.35/1000 in the adult population (21-60 y). In 59% of cases the etiology is sport-related, while among all sports running is involved in 53%. Male sex is most commonly involved, from 4 to 9 times more than females. Natural history of Achilles tendinopathy remains unclear: at 8 years, 29% of patients undergo surgery. Several risk factors are implied in the development of this condition: drugs assumption (corticosteroids and fluoroquinolone antibiotics), systemic diseases (hypertermia, autoimmune or inflammatory conditions, collagen abnormalities), and mechanical factors. Among the last ones, intrinsic or extrinsic factors are recognized ( Fig. 2 ); excessive loading of tendons during vigorous physical training is regarded as the main pathological stimulus for degeneration. The cardinal symptom of Achilles tendinopathy is pain, referred as stabbing or burning. Generally it occurs at the beginning and end of a training session, with a period of diminished discomfort in between. As the pathological process progresses, pain may occur during exercise, and, in severe cases, it can interfere with activities of daily living. In the acute phase, the tendon is diffusely swollen and oedematous, and on palpation tenderness is usually greatest 2–6 cm proximal to the tendon insertion ( Fig. 3 ). A tender, nodular swelling is usually present in chronic cases and is believed to signify tendinosis. The diagnosis of Achilles tendinopathy is based mainly on history and detailed clinical examination. However, diagnostic imaging may be required to verify a clinical suspicion or, occasionally, to exclude other musculoskeletal disorders. Ultrasonography is commonly employed to examine tendon disorders, being readily available, quick, safe and inexpensive. However, it is operator-dependent, offers limited soft-tissue contrast and is less sensitive than MRI. In a longitudinal US scan ( Fig. 4 ), a normal Achilles tendon appears a hyperechoic, ribbon-like structure contained within two parallel hyperechogenic bands corresponding to the paratenon. Tendon fascicles appear as alternate hypoechogenic and hyperechogenic bands. In an axial US scan ( Fig. 5 ), the AT appears round- or oval-shaped, and is characterized by several homogeneously-scattered spotty echoes. In chronic cases, peritendinous adhesions may be shown by thickening of the hypoechoic paratenon with poorly defined borders. A simple grading system has been devised for tendinopathy, measuring its anterior-posterior diameter through an axial US scan: grade 1 represents a normal tendon; grade 2 an enlarged tendon >7 mm; and grade 3 a tendon containing a hypoechoic area. High-frequency probes allow for the visualization of areas with loss of fibrillar echostructure and hypoechoic areas ( Fig. 6 ), which can be nodular, diffuse or multifocal, and correlate well with macroscopic findings at surgery. MRI ( Fig. 7 ) provides extensive information on the internal morphology of tendon and the surrounding structures, and is useful to evaluate various stages of chronic degeneration and for differentiation between peritendinitis and tendinosis. A large variety of treatments have been proposed (stretching, night splints, weight loss, decrease of sport activity, orthotics supports, NSAIDs, shockwaves, steroid injection or surgical debridement), but no standard of care has yet been established. The purpose of our work is to compare the short- and long-term outcome of US-guided percutaneous treatment based on dry needling and peritendinous steroid injection in these patients, compared with similar patients treated with simple steroid injection or dry needling.