Innervation patterns of hamstring muscles, including morphological descriptions and clinical implication.

Area of Science:

• Anatomy
• Neuroscience
• Surgical Anatomy

Background:

• Hamstring muscles are crucial for lower limb movement.
• Innervation patterns of hamstring muscles by the sciatic nerve have been inconsistently reported.
• Understanding precise innervation is vital for clinical procedures.

Purpose of the Study:

• To investigate and characterize the detailed innervation patterns of the hamstring muscles.
• To identify the number and penetration points of sciatic nerve branches supplying each hamstring muscle.
• To explore potential anatomical variations and their clinical implications.

Main Methods:

• Dissection of 35 cadaver limbs (78.6 ± 17.2 years; 48.6% male).
• Systematic recording of sciatic nerve branches supplying the biceps femoris (long and short heads), semitendinosus, and semimembranosus.
• Documentation of the exact penetration level of each nerve branch into the muscle.

Main Results:

• The semitendinosus consistently received two branches, typically entering the upper and middle thirds.
• The semimembranosus usually received one branch, entering the middle or lower third.
• The biceps femoris long head showed one or two branches entering the superior or middle thirds, with a fibrous connection to the sciatic nerve noted.
• The biceps femoris short head typically received one branch entering the middle third.
• Four instances of common nerve supply to multiple hamstring muscles were observed.

Conclusions:

• Detailed hamstring innervation patterns were established, offering valuable data for neurolysis and thigh surgeries.
• A novel mechanical connection between the sciatic nerve and the biceps femoris long head was identified.
• This anatomical finding may elucidate the pathophysiology of certain neuralgias affecting the posterior thigh.