The Achilles tendon resting angle as an indirect measure of Achilles tendon length following rupture, repair, and rehabilitation

Background Rupture of the Achilles tendon may result in reduced functional activity and reduced plantar flexion strength. These changes may arise from elongation of the Achilles tendon. An observational study was performed to quantify the Achilles tendon resting angle (ATRA) in patients following Achilles tendon rupture, surgical repair, and rehabilitation, respectively. Methods Between May 2012 and January 2013, 26 consecutive patients (17 men), with a mean (standard deviation, SD) age of 42 (8) years were included and evaluated following injury, repair, and at 6 weeks, 3 months, 6 months, 9 months, and 12 months, respectively (rehabilitation period). The outcome was measured using the ATRA, Achilles tendon total rupture score (ATRS), and heel-rise test. Results Following rupture, the mean (SD) absolute ATRA was 55 (8)° for the injured side compared with 43 (7)° (p < 0.001) for the noninjured side. Immediately after repair, the angle reduced to 37 (9)° (p < 0.001). The difference between the injured and noninjured sides, the relative ATRA, was -12.5 (4.3)° following injury; this was reduced to 7 (7.9)° following surgery (p < 0.001). During initial rehabilitation, at the 6-week time point, the relative ATRA was 2.6 (6.2)° (p = 0.04) and at 3 months it was -6.5 (6.5)° (p < 0.001). After the 3-month time point, there were no significant changes in the resting angle. The ATRS improved significantly (p < 0.001) during each period up to 9 months following surgery, where a score of 85 (10)° was reported. The heel-rise limb symmetry index was 66 (22)% at 9 months and 82 (14)% at 12 months. At 3 months and 6 months, the absolute ATRA correlated with the ATRS (r = 0.63, p = 0.001, N = 26 and r = 0.46, p = 0.027, N = 23, respectively). At 12 months, the absolute ATRA correlated with the heel-rise height (r = -0.63, p = 0.002, N = 22). Conclusion The ATRA increases following injury, is reduced by surgery, and then increases again during initial rehabilitation. The angle also correlates with patient-reported symptoms early in the rehabilitation phase and with heel-rise height after 1 year. The ATRA might be considered a simple and effective means to evaluate Achilles tendon function 1 year after the rupture.