SLR - December 2017 - Ryan Supon

Tendon Length, Calf Muscle Atrophy and Strength Deficit After Acute Achilles Tendon Rupture

Reference: Heikkinen J et al. Tendon Length, Calf Muscle Atrophy, and Strength Deficit After Acute Achilles Tendon Rupture: Long-Term Follow-up of Patients in a Previous Study. J Bone Joint Surg Am. 2017 Sep 20;99(18):1509–1515.

Scientific Literature Review

Reviewed By: Ryan Supon, DPM
Residency Program: Southern Arizona VA Health Care System, Tucson, AZ

Podiatric Relevance: Even with surgical repair of acute Achilles tendon ruptures, the injured leg usually does not regain full strength. Previous studies have suggested that elongation of the Achilles tendon during rehabilitation may account for this deficit in strength. Another proposed cause is calf muscle atrophy secondary to fatty degeneration following injury. The goals of this study were to accurately measure long-term changes in Achilles tendon length, calf muscle volume and calf muscle fatty degeneration in acute Achilles tendon ruptures with surgical repair and to determine how these structural changes correlate with calf muscle strength deficits.

Methods: Fifty-five patients (48 male, seven female; Average age: 38 years old) were included in this long-term cohort study. Average follow-up was 14 years ± 0.5 after rupture. Inclusion criteria included complete Achilles tendon rupture and age 18 to 65. Exclusion criteria included  >1 week delay before treatment, corticosteroid injections around the Achilles tendon within six months of rupture, previous contralateral Achilles tendon rupture, diabetes mellitus and open Achilles tendon ruptures. Outcome measures for both legs included Achilles tendon length, calf muscle volume, fatty degeneration and isokinetic plantarflexion strength. MRI was used to measure Achilles tendon length, calf muscle volume and fatty degeneration. Isokinetic plantarflexion strength was captured using an isokinetic dynamometer and measured at 10° intervals throughout ROM of the ankle. Correlations between Achilles tendon length, plantarflexion strength and muscle volume were identified using the Spearman correlation coefficient

Results: Mean Achilles tendon length was 12 mm longer in the injured leg. The mean soleus, lateral gastrocnemius and medial gastrocnemius muscle volumes in the injured leg were all 13 percent less than the uninjured leg. The mean FHL volume was 5 percent higher in the injured leg compared to the uninjured leg, indicating compensatory FHL hypertrophy after Achilles tendon rupture. Fatty degeneration of the soleus and gastrocnemius muscles was significantly greater in the injured leg compared to the uninjured leg, with the soleus most affected. Median plantar flexion strength deficits in the injured leg ranged between 12 and 18 percent throughout ankle range of motion compared to the uninjured leg. Increased Achilles tendon length correlated with strength deficits in end-range plantarflexion and decreased medial gastrocnemius and soleus muscle volume.

Conclusions: This study reinforces previous findings of increased Achilles tendon length, decreased calf muscle volume with resultant fatty degeneration and decreased calf muscle strength following acute Achilles tendon rupture with surgical repair. Strengths of this study include long-term follow-up (14 years ± 0.5) and MRI techniques to more accurately report the outcome measures. Weaknesses of this study include not having preinjury MRI images, as it was assumed that both legs were symmetrical prior to the injury and only having one examiner measure these values from the MRI images. Based on these findings, the authors postulate that while early weightbearing and range of motion exercises promote tendon healing, they also likely lead to subtle Achilles tendon lengthening postoperatively. The authors suggest that this postoperative increase in Achilles tendon length may explain the long-term decrease in calf muscle volume and plantarflexion strength.

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