Differences at the Achilles Insertion Between Adults with Insertional and Midportion Achilles Tendinopathy as Observed Using Ultrasound

The purpose of this study was to determine structural and pathological differences of Achilles tendon insertion between insertional Achilles tendinopathy (IAT) and midportion Achilles tendinopathy (MidAT) in both injured and uninjured sides. Patients (n=34; 58.8% male) with unilateral Achilles tendinopathy (50% with IAT; 50% with MidAT) were recruited. Median age 52 years and Victorian Institute of Sport Assessment - Achilles (VISA-A) score mean 59, and 17 (12 male) had MidAT, median(range) age of 58(48)years, and VISA-A score mean(SD) 59.1(19.7). Ultrasound imaging was used to evaluate structural measurements at the insertion (insertional length, bone-to-insertion length, and tendon insertion angle), tendon length (calcaneus to soleus), tendon thickness at the calcaneal edge, and the presence of pathological changes (boney deformity and/or calcification). A 2×2 mixed Analysis of Variance (group by side) was used to compare IAT and MidAT groups and injured and uninjured sides. Tendon thickness at the calcaneus on the injured side was significantly greater than the uninjured side in the IAT group but not in the MidAT group (P=.001). VISA-A score was 59.9(18.7) in IAT group and 59.1(19.7) for MidAT group (P=.909). There were no significant group-by-side interactions for structural measurements at insertion site. Calcaneal edge tendon thickness was the only significant structural difference observed between involved and uninvolved sides in IAT, although this was not found in in MidAT.