On symptomatic LEFT side
- Clavicular head of pectoralis major is present.
- Sternal head pectoralis major is seen from menubrium.
No muscle origin from body of sternum.
- Costal head of pectoralis major is absent.
- Pectoralis major tendon is present but thiner than asymptomatic side.
- Pectoralis minor is present.
On asymptomatic RIGHT side
- All three heads ( clavicular, sternal, costal ) of pectoralis major are present.
- Pectoralis minor is present.