Lower material stiffness in rupture-repaired Achilles tendon during walking: transmission-mode ultrasound for post-surgical tendon evaluation
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This cross-sectional study used transmission-mode ultrasound to evaluate dynamic tendon properties during walking in surgically repaired and contralateral Achilles tendon (AT), with a median (range) post-operative period of 22 (4–58) months. It was hypothesised that the axial transmission speed of ultrasound (TSOU) during walking would be slower, indicating lower material stiffness in repaired compared with contralateral AT.
Ten patients [median (range) age 47 (37–69) years; height 180 (170–189) cm; weight 93 (62–119) kg], who had undergone open surgical repair of the AT and were clinically recovered according to their treating clinicians, walked barefoot on a treadmill at self-selected speed (1.0 ± 0.2 m/s). Synchronous measures of TSOU, sagittal ankle motion, vertical ground reaction force (GRF), and spatiotemporal gait parameters were recorded during 20 s of steady-state walking. Paired t tests were used to evaluate potential between-limb differences in TSOU, GRF, ankle motion, and spatiotemporal gait parameters.
TSOU was significantly lower (≈175 m/s) in the repaired than in the contralateral AT over the entire gait cycle (P < 0.05). Sagittal ankle motion was significantly greater (≈3°) in the repaired than in the contralateral limb (P = 0.036). There were no significant differences in GRF or spatiotemporal parameters between limbs.
Repaired AT was characterised by a lower TSOU, reflecting a lower material stiffness in the repaired tendon than in the contralateral tendon. A lower material stiffness may underpin greater ankle joint motion of the repaired limb during walking and long-term deficits in the muscle-tendon unit reported with AT repair. Treatment and rehabilitation approaches that focus on increasing the material stiffness of the repaired AT may be clinically beneficial. Transmission-mode ultrasound would seem useful for quantifying tendon properties post AT rupture repair and may have the potential to individually guide rehabilitation programmes, thereby aiding safer return to physical activity.
Level of evidence
KeywordsTendon healing Tendon rupture Biomechanics Locomotion Gait analysis Speed of sound
All the authors contributed substantially to study conception and design, interpretation of data, and revision and final approval of the manuscript. MW, MSh, and SW were responsible for data collection. MW and SW were responsible for data analysis and are responsible for the overall content of the manuscript as guarantors.
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interest, financial, or otherwise.
Scott Wearing is funded through an Accelerate Fellowship, Department of Science, Information Technology and Innovation, Queensland Government and an August-Wilhelm Scheer Professorship, Technische Universität München, Germany. This research received financial support from the Australia-Germany Research Cooperation Scheme. The funders had no direct involvement in the study.
The study has been reviewed and approved by the institutional research ethics committee.
Informed consent was obtained from all individual participants included in the study.
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