Ruptured human Achilles tendon has elevated metabolic activity up to 1 year after repair

Purpose Following Achilles tendon rupture, running is often allowed after 6 months. However, tendon healing is slow and the metabolic status of the tendon at this point is unknown. The purpose of this study was to investigate tendon metabolism (glucose uptake) and vascularization at 3, 6 and 12 months after Achilles tendon rupture as measured using PET and power Doppler ultrasonography (PDUS). Methods The study group comprised 23 patients with surgically repaired Achilles tendon rupture who were investigated at 3 months ( n = 7), 6 months ( n = 7) and 12 months ( n = 9) after surgery. The triceps surae complex was loaded over 20 min of slow treadmill walking while a radioactive tracer ( 18 F-FDG) was administered prior to PET. Vascularization was measured in terms of PDUS flow activity, and patient-reported outcomes were scored using the Achilles tendon rupture score (ATRS) and sports assessment (VISA-A) questionnaire. Results Relative glucose uptake ( 18 F-FDG) was higher in repaired tendons than in intact tendons at all time-points (6, 3 and 1.6 times higher at 3, 6 and 12 months, respectively; P ≤ 0.001), and was also higher in the tendon core than in the periphery at 3 and 6 months ( P ≤ 0.02), but lower at 12 months ( P = 0.06). Relative glucose uptake was negatively related to ATRS at 6 months after repair ( r = −0.89, P ≤ 0.01). PDUS flow activity was higher in repaired tendons than in intact tendons at 3 and 6 months ( P