A young male athlete presented with a longstanding thigh lump, which was non tender and with no clear history of trauma.

High Resolution Ultrasound of the region of clinical interest demonstrated a focal convexity of the superficial fibres of the direct head of rectus femoris muscle. With dynamic stress there was herniation of rectus femoris muscle fibres into a fascial defect, which reduced spontaneously at rest. Ultrasound demonstrated subtle heterogeneous echotexture of the underlying muscle fibres suggestive of myofascial oedema.

There was noted to be a focal echogenic area at the superior margin of the fascial defect on Ultrasound. We performed high resolution 3T MRI to further define this area and the underlying muscle fibrillar pattern.

3T MRI image acquisition was performed on a Siemens Lumina 3T MRI with Deep Resolve AI image enhancement. MRI demonstrated focal bulging of the superficial direct rectus femoris fibres, well illustrated on the sagittal images. There was mild underlying muscle oedema, and focal tethering of the superior margin of the fascial orifice on the MRI images characterized by a small well demarcated lobule of adipose tissue. There was some scar tissue at the superior fascial margin of the hernial defect, characterised by T1 hypointensity. On resting MRI there was mild bulging of the muscle fibres into the fascial orifice. No mass, muscle tear or fluid collection was demonstrated.

The MRI appearances correlated with the findings on ultrasound of a myofascial hernia of rectus femoris muscle.

Comment:

High Resolution dynamic Ultrasound combined with 3T MRI with Deep Resolve image enhancement has well demonstrated an unusual case of a focal myofascial hernia involving the superficial rectus femoris fascia, with dynamic scanning demonstrating herniation and spontaneous reduction of the muscle hernia, and MRI demonstrating mild oedema of the involved muscle fibres, scarring and tethering of the margins of the fascial defect.

This somewhat unusual case illustrates the benefits of utilising MRI and high resolution Ultrasound, which may play a complimentary role in the assessment of unusual muscle pathology, exclusion of a mass and the benefits of dynamic ultrasound in demonstrating myofascial hernias, which may be difficult to appreciate on resting Ultrasound or MRI alone.

Dr Angus Watts ; MBBS; FRANZCR (Musculoskeletal and Interventional Radiologist; Principal)

Panorama Radiology Specialists is an independent doctor-owned comprehensive radiology clinic on the Gold Coast subspecialising in musculoskeletal and spinal conditions.