Fatty Infiltration of the Gastrocsoleus After Tendo-Achilles Lengthening and Gastrocnemius Recession in a Rabbit Model

Background: Tendo-Achilles lengthening (TAL) and gastrocnemius recession (GR) are components of the operative treatment for certain foot conditions. We investigated changes in rabbit gastrocsoleus weight, volume, and percent fat resulting from TAL, GR, and immobilization. Materials and Methods: Eighteen rabbits were randomized into three groups. Group I = gastrocnemius recession; Group II = (TAL) Z-plasty lengthening; Group III = immobilization only. Treatment limbs were randomized. Six randomly selected contralateral limbs were used for controls. At 12 weeks the gastrocnemius and soleus were weighed (g) and measured (ml) separately. Values were combined and analyzed as a gastrocsoleus complex. The weight, volume, and percentage of fatty infiltration were analyzed using one-way analysis of variance (ANOVA). Results: The following differences were statistically significant. GR volume was less than control (p < 0.01); TAL weight and volume was less than control (p < 0.01); GR percent fat was greater than control (p < 0.05) and TAL percent fat was greater than control (p < 0.05). GR weight and volume was less than cast only (p < 0.01); TAL weight and volume was less than cast only (p < 0.01); TAL percent fat was greater than cast only (p < 0.01); GR percent fat was greater than cast only (p < 0.05); GR weight was greater than TAL (p < 0.05). Conclusion: In a rabbit model, the findings suggest the gastrocsoleus undergoes atrophy and fatty infiltration after TAL or GR. Immobilization does not contribute to either process. Clinical Relevance: These findings correlate with human functional studies documenting the relationship between TAL or GR and decrease in plantarflexion strength. Further studies are needed to determine if significant variation in functional differences due to TAL versus GR exists.