Soleus Accessorius: An Uncommon Anatomic Variant of the Calf Muscle

Anatomical variants like the soleus accessorius underscores the incredible diversity within the human body. It serves as a reminder that healthcare professionals should remain vigilant, especially in cases where unexpected structures or variations are encountered during diagnosis or treatment.

Sagittal T2w and T1w – MRI 0.3 Tesla

The soleus accessorius, also known as accessory soleus, is a relatively rare anatomical variant of the calf muscle, the soleus. The soleus muscle is one of the two major muscles in the calf, with the other being the gastrocnemius. The soleus accessorius, when present, is typically an additional muscle belly or slip located adjacent to the primary soleus muscle.

The presence of a soleus accessorius can have clinical significance in several ways:

1. Misdiagnosis: An accessory soleus can be mistaken for a soft tissue mass or other pathology in medical imaging studies, potentially leading to misdiagnosis and unnecessary medical interventions.

2. Functional Impact: In some cases, the soleus accessorius can be associated with altered biomechanics and may contribute to conditions like posterior compartment syndrome, leading to pain and discomfort in the lower leg.

3. Surgical Considerations: Surgeons and orthopedic specialists need to be aware of a soleus accessorius when performing procedures on the calf muscles to avoid accidental damage or complications.

Soleus Myotendinous Junction Injury

About aponeurotic medial insertion injury of the soleus muscle.

Knowing the anatomy and biomechanics of the gastrocnemius-soleus complex – or triceps surae – is crucial for an understanding of the etiology and treatment of all its possible injuries. Today I want to show you a painful partial lesion at the aponeurotic medial insertion of the soleus muscle in a professional soccer player.

One month after a soleus injury, a patient suffered for pain and discomfort at the distal soleus myotendinous junction; first examination was made with an ultraportable device directly on the pitch during a daily training session. A partial injury of the aponeurotic medial insertion was evident, togheter with muscle perilesional edema.

soleus-injury

Sagittal Ultrasound comparative examination of the medial soleus myotendinous junction; normal findings on the right side.

soleus-medial-insertion

Sagittal GeStir (left) and Coronal T2w Mri scans of the same patient (0.3 Tesla).

fse_t2__2__and_fse_t2__4_

Axial (left) and Sagittal (right) T2w Mri scans (0.3 Tesla).

With the dynamic ultrasound examination is better appreciated also an inflammation along the course of the posterior tibial nerve.

Also in this case the elastosonography evaluation works like a “contrast agent” well depicting the lesional area.

You can find further information about the complex anatomy of the triceps surae in this interesting scientific paper: Anatomy of the Triceps Surae: A Pictorial Essay