Abstract
Introduction
The healing of Achilles tendon rupture is slow and jogging is usually allowed already 6 months after injury. However, the metabolic status of the healing tendon is largely unknown at the time-points when increased loading is allowed. The purpose of this study was to investigate tendon metabolic response and blood flow at 3, 6 and 12 months after Achilles tendon rupture by positron emission tomography (PET) and ultrasound-Power Doppler (UPD).
Materials and Methods
23 patients that had surgical repair of a total Achilles tendon rupture (3 (n=7), 6 (n=7) or 12 (n=9) months earlier) participated in the study. The triceps surae complex was loaded during 20 min of slow treadmill walking. A radioactive tracer (FDG) was administered during this walking and glucose uptake was measured bilaterally by the use of PET. Blood flow was recorded by UPD and patient reported outcome scored by Achilles tendon rupture score (ATRS) and VISA-A. Non-parametric statistics were used for statistical analysis.
Results
Metabolic activity was higher in the healing tendon compared to intact tendon at all time-points, however the activity decreased over time (510%, 260% and 62% higher on the healing side compared to the intact side at 3, 6 and 12 months respectively, p<0.001). The metabolic activity was higher in the core than the periphery of the healing tendon, at 3 and 6 months (p<0.02), but lower at 12 months (p=0.06). Interestingly, metabolic activity was negatively related to ATRS, 6 months after rupture (r=−0.89, p<0.01). UPD was also 100-fold and 61-fold higher respectively in the healing than the intact healthy tendon at 3 months (p<0.05) and 6 months (p=0.06), but not at 12 months.
Discussion
These results demonstrate that the healing process measured by metabolic and blood flow activity still remains high 6 months after rupture when increased loading is allowed. In fact, PET determined metabolic activity remained elevated up to a year after injury when measures of hyper-vascularization were normalized. Although speculative, the strong negative correlation between tendon metabolism and patient reported outcome indicates that a high metabolic activity 6 months after the injury may be related to poor healing outcome.
