Persistent functional loss following ruptured Achilles tendon is associated with reduced gastrocnemius muscle fascicle length, elongated gastrocnemius and soleus tendon, and reduced muscle cross-sectional area

We examined muscle function, muscle architecture, and tendon length bilaterally in persons who experience a functional deficit 2 years after an Achilles tendon rupture. Eleven persons were investigated on the injured compared with the uninjured side 47 +/- 7 months (mean +/- SD) after a tendon rupture. Heel-rise data, plantar flexion strength, tendon resting angle 3D MRI-determined tendon length and muscle cross-sectional area, ultrasound-determined fascicle length, and pennation angle were obtained. The heel-rise test yielded reduced max height (32%), number of repetitions (54%), and work performed (61%), P < .001. Plantar flexion strength was impaired (P < .001) with the knee in extension (20%-42%) and flexion (29%-39%). Muscle cross-sectional area was reduced for both the soleus (36%) and gastrocnemius muscles (46%; P < .001). Both the soleus tendon (55%) and the gastrocnemius tendon (14%) were longer (P < .001), and the fascicle length of the medial gastrocnemius was substantially reduced (18%; P < .001). The difference in heel-rise height correlated to that of the gastrocnemius tendon elongation, r = .66, P < .05, but not soleus tendon elongation. These data show that a functional deficit after an Achilles tendon rupture is associated with an elongated soleus and gastrocnemius tendon along with a reduced soleus and gastrocnemius muscle cross-sectional area and gastrocnemius fascicle length.