In-vivo quantification of the morphomechanical recovery among Achilles subtendons following total rupture.

• Applicant: Dr. Andreas Brand
• Subject Area: Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 552605231

The Achilles tendon, as a union of several tendon aspects of the calf muscles, plays a crucial biomechanical role in human motion. In particular, the complex anatomy and interaction (different relative length changes) of the individual tendon components (Achilles subtendons) of the gastrocnemius and soleus muscles play a decisive role in the efficient transmission of force from the calf muscles towards the foot. A complete rupture of the Achilles tendon usually causes a significant limitation in mobility in affected patients, who clinically show an unsatisfactory outcome in foot function even during long-term rehabilitation after surgical treatment. Morphological and biomechanical adaptations within the Achilles tendon, which form the basis for the observed functional changes, have been insufficiently studied. In particular, the impact of injury on the important mechanism of subtendon interaction has not yet been investigated in the clinical setting of an Achilles tendon rupture. Therefore, the aim of this study is to accurately explore the structural adaptations of the Achilles tendon after complete rupture, by considering the complex anatomy. The morphological-biomechanical movement behaviour of the subtendons will be investigated during dynamics (gait function and active plantarflexion) initially and over a healing course of one year postoperatively. For this purpose, a combined measurement method of marker-based motion analysis and portable diagnostic ultrasound will be applied to a representative patient collective with unilateral traumatic Achilles tendon rupture and a healthy control group. Complementary investigations of the tissue quality and mechanics of the ruptured Achilles tendon will be performed by analyzing gray scale levels in the ultrasound image (echointensity analysis) and by using digital palpation of the tendon surface (myotonometry). These data will then be transferred to the dynamic measurements to identify correlations between tissue properties of the entire tendon and the dynamic interaction of single subtendons. By precisely quantifying the mechanical properties of the individual subtendons, this project will thus make an important contribution to the knowledge of underlying adaptation mechanisms and residual function of the ruptured Achilles tendon. By identifying different adaptation patterns at the subtendon level of the ruptured Achilles tendon, the clinical-therapeutic treatment of this injury could also be directed in a more purposeful manner in the future.

• DFG Programme: Research Grants
• Co-Investigator: Professor Peter Augat, Ph.D.