Purpose. Platelet Rich Plasma (PRP) has been shown to have positive effect in tendon regeneration in in-vitro and limited in-vivo animal studies. We aim to study PRP use in acute Achilles tendon rupture (ATR) regeneration in a purposely designed clinical trial. Methods. This is a prospective double-arm patient-blinded randomized controlled trial. ATR patients were randomized into PRP treatment or control groups. Non-operatively treated patients received PRP or control injection in clinic. In operatively treated patients, PRP gel was applied in the ruptured gap during percutaneous repair. Standard rehabilitation protocol was used and patients were followed up for 24 weeks. ATR, VISA-A and FAOS scores were used as subjective outcome measures. Functional ultrasound Elastography (FUSE) was performed at each follow-up to assess the mechanical properties of tendons. PRP analysis and tendon needle-biopsy were performed to study the histological differences during healing in both groups. Results. 20 patients were recruited with mean age 37.5±8.8 (8males and 7 females). Rupture location was 4.8±2.1 cm from insertion. PRP platelet count 1044±320 × 1000/μL with average platelet CD62p activation 68.42±4.5%. Mixed linear regression analysis revealed PRP treated tendon achieved better ATR and VISA-A outcome scores (p<0.05). FAOS score analysis showed that PRP group had better pain, ADL and symptoms scores with significant difference apparent from week 3 onwards. Strain mapping using FUSE scan in 4 patients showed bigger harder tendons in PRP group. Analysis of the remaining patients is on the way. To achieve the desired statistical power in pragmatic settings, recruitment will continue in a multi-centre trial. Conclusion. Our preliminary findings show that PRP application in Achilles tendon rupture may lead to faster regeneration and return to function as supported by a combination of objective and subjective outcome measures

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