Ruptured human Achilles tendon has elevated metabolic activity up to 1 year after repair
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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).
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 (18F-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.
Relative glucose uptake (18F-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 < 0.05 for both), but had normalized by 12 months.
These data demonstrate that the healing process as determined by metabolic activity and vascularization continues for 6 months after injury when large loads are typically allowed on the tendon. Indeed, metabolic activity remained elevated for more than 1 year after injury despite normalized vascularization. The robust negative correlation between tendon metabolism and patient-reported outcome suggests that a high metabolic activity 6 months after the injury may be related to a poor clinical healing outcome.
KeywordsHealing Power Doppler ultrasonography 18F-FDG Positron emission tomography Loading ATRS
We thank specialist technologist Eva Brødsgaard for excellent help with the PET procedures.
Compliance with ethical standards
Conflict of interest
The authors have no conflict of interest.
This study was supported by the Center of Healthy Aging, Danish Association of Rheumatism, IOC Sports Medicine Copenhagen, the Danish Medical Research Council and the Swedish Society for Medical Research.
The study was approved by the local ethics committee for experimental procedures (H-3-2012-060) and was performed according to the principles of the Declaration of Helsinki.
Informed consent was obtained from the patients.
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