SLR - September 2018 - Johnny C. Huang

The Role of the Vascular and Structural Response to Activity in the Development of Achilles Tendinopathy: A Prospective Study

Reference: Wezenbeek E, Willems T, Mahieu N, Muynck MD, Bossche LV, Steyaert A, Clercq DD, Witvrouw E. The Role of the Vascular and Structural Response to Activity in the Development of Achilles Tendinopathy: A Prospective Study. Am J Sports Med. 2018 Jan 26; 46(4):947–954.

Scientific Literature Review

Reviewed By: Johnny C. Huang, DPM
Residency Program: Montefiore Medical Center, Bronx, NY

Podiatric Relevance: One of the most common conditions treated by foot and ankle specialists is Achilles tendinopathy (AT). Despite high prevalence, the risk factors suggested in current literature are not well studied, and it remains unclear if they will predict future symptoms. Recent studies, such as those using techniques like ultrasound tissue characterization (UTC), have shown mixed results in identifying structural risk factors. This study investigates the validity and provides prospective study of Achilles tendon thickness, vascular response to activity, foot posture and UTC tendon structure as potential risk factors for AT.

Methods: In this level II prospective cohort study, 250 freshman students at Ghent University were analyzed for blood flow, Achilles tendon thickness, UTC and Foot Posture Index (FPI) on both Achilles tendons in randomized order from 2013–2014 and 2014–2015 academic years. Blood flow measurements and ultrasound exam were performed after the subjects performed physical activity. The participants all had the same 29-week sports program as part of their curriculum, and average weekly sports participation was recorded (this was used as a time at risk for every subject). The time at risk was recorded from the study start time until an injury or until the end of the study period for students who did not develop any injury.

Results: Twenty-seven of the 250 participants developed Achilles tendinopathy, and 223 did not sustain any injury. Cox regression analysis risk model isolated sex, increase in blood flow after running, timing of blood flow measurements and foot posture as relevant variables. Female sex and increase of blood flow after running were significant predictive factors. A hazard ratio showed risk of developing AT increased by 3 percent if the blood flow increase after running was lowered by 1 atmospheric unit.

Conclusions: Female sex and blood flow after running were found to be significant risk factors for developing Achilles tendinopathy. The results showed that the lower the increase in blood flow after running, the higher the risk of developing AT, thus confirming previous studies. However, this finding may suggest that a lower increase in blood flow after running can cause delayed regeneration of the tendon, thus making insufficient recovery time a problem that could influence risk for AT. This was the first prospective study to identify female sex as a risk factor for AT. However, it may be difficult to generalize this conclusion because there are possible sex differences in reporting injuries, seeking care or the types of physical activities. From this study at least, we can presume in a young adult population, females are at higher risk of developing AT versus males when performing similar activities. Interestingly, tendon structure and thickness were not identified as significant risk factors, but this was likely due to study population and design. Furthermore, relationship between foot posture and risk for AT was not able to be made in this study. Limitations include inability to measure blood flow real-time, UTC incapacity to detect small structural changes in tendon and chosen study population. 

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