Muscular atrophy of the lower leg in unilateral post traumatic osteoarthritis of the ankle joint

Abstract

Purpose: Muscle atrophy is a commonly encountered problem in osteoarthritis (OA). The aim of this study was to estimate the amount of muscle atrophy and fatty degeneration of the lower leg muscles related to ankle OA by magnetic resonance imaging (MRI).

Methods: Twenty-one patients with unilateral ankle OA were included in this cohort study. Calf circumference of the affected and healthy lower leg was documented. The degree of OA was classified in conventional radiographs. The cross-sectional areas and fatty degeneration of the muscles of the lower leg were measured in bilateral MRI.

Results: We found a significantly reduced calf circumference of the affected vs. healthy leg (p = 0.016). MRI showed a significantly lower cross-sectional area of the entire lower leg musculature in OA (p = 0.013). Sub-analysis of muscle groups revealed that only the M. soleus had a significant cross-sectional area decrease (p < 0.01). All muscles showed a significant fatty degeneration (p < 0.01).

Conclusions: We conclude that unilateral ankle joint osteoarthritis leads to an overall lower leg muscle atrophy, but significant atrophy of the M. soleus. All muscles of the affected leg undergo a fatty degeneration.

Fig. 1

Quantitative analysis. This figure represents the affected and healthy lower leg of patient no. 1 from Table 1. To calculate the area, the anatomic boundary of following muscle groups (respectively the individual muscles) were manually marked: the anterior tibial muscle group (blue), the peroneal muscle group (pink), the deep dorsal muscle group (green), the M. gastrocnemius medialis (grey) and lateralis (yellow), and the M. soleus (red)

Fig. 2

Qualitative analysis. This figure represents the affected lower leg of patient no. 1 from Table 1. Fatty muscle degeneration was assessed at the level of the quantitative measurement. The grade of fatty degeneration is displayed within each muscle group: anterior tibial muscle group (blue, 3), the peroneal muscle group (pink, 2), the deep dorsal muscle group (green, 3), the M. gastrocnemius medialis (grey, 1) and lateralis (yellow, 1), and the M. soleus (red, 3)

Fig. 3

Results of the quantitative analysis. A significant (*p < 0.01) decrease of the muscle cross-sectional area was only found in the M. soleus of the affected leg (white box), when compared to the healthy leg (grey box). In all other muscle groups the difference was not significant (ns)

Fig. 4

Results of the qualitative analysis. A significant (*p < 0.01) fatty degeneration of the muscle tissue was found in all muscle groups of the affected leg (white box), when compared to the healthy leg (grey box)