Altered Tendon Characteristics and Mechanical Properties Associated With Insertional Achilles Tendinopathy

Abstract

A cross-sectional image was obtained 2 cm proximal to the tendon insertion. Echogenicity was quantified as the mean grayscale value for the central 1 cm of the entire depth of the tendon cross-section (FIGURES 1C and 1D). The grayscale value for a pixel could range from 0 (black) to 255 (white). The mean grayscale value for all pixels in the region of interest was quantified using ImageJ, with a lower value indicating greater pathology. All ultrasound images had the same gain setting of 56 and were collected at a 3-cm depth, so that differences in ultrasound settings would not influence the mean grayscale values between participants. Tendon Mechanical PropertiesThe combination of ultrasound imaging and dynamometry was used to measure tendon mechanical properties (strain, stiffness). Each participant's ankle was positioned and secured in a Biodex System 4 (Biodex Medical Systems, Inc, Shirley, NY) in sitting, with the seatback reclined to 45°, the chair height adjusted so that the tibia was parallel to the floor, and the hip in neutral adduction/abduction (FIGURE 2A). The participant's ankle was moved in the sagittal plane from 10° of plantar flexion to 10° of dorsiflexion at a rate of 5°/s, and the passive plantar flexion torque was recorded at a rate of 1000 Hz. Similar to previous studies, 5,8,18 ultrasound imaging was used to track the linear displacement of the gastrocnemius muscle-Achilles tendon junction (MTJ), with the probe at a fixed point on the calf (FIGURES 2B and 2C). A first set of 6 rotations was used for preconditioning, followed by a second set of 6 rotations, from which images were used to calculate tendon mechanical properties. B-mode ultrasound images were collected when the ankle was in (1) 10° of plantar flexion at the start and end of the second set and (2) 10° of dorsiflexion during the third, fourth, and fifth repetitions. The location of the MTJ in each ankle position was averaged, so that distance between the MTJ locations in 10° of plantar flexion and 10° of dorsiflexion could be calculated. A video was taken on the second repetition to confirm that the images captured the full range of MTJ displacement. Passive torque values from the third, fourth, and fifth repetitions of the second set were used for analysis. Participants were instructed to relax as the foot plate moved the ankle. To ensure that the condition was passive, the activity of the medial gastrocnemius and the anterior tibialis muscles was monitored by a 2-channel Bagnoli desktop electromyography system (Delsys Inc, Natick, MA). Single-differential surface electrodes (input impedance greater than 1015 Ω // 0.2 pF; common-mode rejection ratio, -92 dB; noise, 1.2 μV; preamplifier gain, 10 V/V  1%) were used. The contact material was 99.9% Ag, in the shape of 2 bars with contact dimensions of 10 × 1 mm and spaced 1 cm apart. The electrodes were placed over the motor point of the medial gastrocnemius and the anterior tibialis muscles. The raw electromyography signal was viewed using a 2-channel digitizing oscilloscope (Tektr...

Utility of Ultrasound for Imaging Osteophytes in Patients With Insertional Achilles Tendinopathy

“…Plus ultrasound has the added benefit of being able to assess soft tissue changes associated with tendinopathy. 9 …”

“…The VISA-A has been validated for use in persons with achilles tendinopathy, 8 and has been shown correlate with severity of tendon pathology in persons with IAT. 9 Participants quantified their worst pain in the past week using the Numerical Rating Scale (NRS). Reliability and validity of NRS has been demonstrated in a variety of chronic pain conditions.…”

“…The physical therapist who acquired the images was trained in musculoskeletal ultrasound and has experience obtaining reliable images of the foot and ankle. 9 Images were acquired using a Phillips HD11 Ultrasound machine with a linear array probe (L 12-3), which was used at a frequency of 10-12 MHz. Ultrasound images were stored and coded digitally by another research team member to de-identify the data prior to analysis by the physical therapist using Image J (http://rsbweb.nih.gov/).…”

Insertional achilles tendinopathy associated with altered transverse compressive and axial tensile strain during ankle dorsiflexion

“…In the clinic, treatment for IAT is commonly driven by the idea that it is an overuse injury with symptoms that are exacerbated by mechanical loading . This idea combined with findings of decreased tensile stiffness in Achilles tendinopathy suggest that excessive tensile strains may be present in patients with IAT. Alternatively, reduced strains and “stress shielding” are also theorized to contribute to tendinopathy .…”

Emerging Technological Advances in Musculoskeletal Ultrasound

“…For Achilles tendinopathy, combining grayscale US and sonoelastography improved diagnostic sensitivity (0.96) and specificity (0.95) with improved clinical correlation ( P < .001) compared to routine grayscale and color Doppler US (sensitivity 0.67, specificity 0.94) [22]. Another study found that Achilles tendon softening detected by sonoelastography at the start of the competitive season was predictive of subsequent development of Achilles tendon symptoms during the season in elite Australian Rules football players [30].…”