Anatomy of the Sartorius Muscle

Courtesy: Prof Nabile Ebraheim, University of Toledo, Ohio, USA

Origin-

• Sartorius muscle arises from the anterior superior iliac spine of the pelvic bone.
• The sartorius muscle crosses the upper third of the thigh obliquely, downwards medially and then descends vertically towards its insertion.
• It is a superficial muscle, the longest muscle and it’s fibres are parallel.

Insertion:

• The sartorius muscle is inserted into the anteromedial surface of the upper tibia.
• Other tendons are inserted into the same location.
• These tendons are called the Pes Anserine tendons.

Sartorius innervation –
The sartorius muscle is innervated by the femoral nerve.

• Surgical approach to the Pes Anserine insertion for harvesting of the semitendinosus and gracilis tendons puts the terminal branch of the saphenous nerve at risk as it emerges between the sartorius and the gracious tendons.

Sartorius function-

• The sartorius muscle flexes abducts and rotates the hip laterally as well as flexes the knee. It is sometimes referred to as the “tailor’s muscle” in reference to the cross-legged position in which the tailor’s once sat.
• The “tailor” position helps to understand the function of the sartorius muscle.

Anatomical & surgical considerations-

• The upper third of the sartorius muscle forms the lateral border of the femoral triangle and it’s middle third forms the roof of the adductor (subsartorial) canal which contains the femoral vessels and the saphenous nerve.
• The femoral triangle is a superficial triangular space located on the anterior aspect of the thigh just inferior to the inguinal ligament.
• The boundaries of the femoral triangle include:
  • Lateral border formed by the medial border of the Sartorius muscle.
  • Medial border formed by the medial border of the Adductor Longus muscle.
  • Base formed by the inguinal ligament.
• The femoral triangle contains 3 important structure from lateral to medial:
  • Femoral nerve
  • Femoral artery
  • Femoral vein
  And it also contains deep inguinal lymph nodes

Lateral cutaneous nerve of thigh-

• Crosses the lateral corner of the triangle.
• Supplies the skin on the lateral part of the thigh.
• The neurovascular bundle is medial to the sartorius muscle.
• Therefore, in the anterior approach to the hip, it is always safe to go lateral to the sartorius muscle in order to avoid the important structures within the femoral triangle.
• It is important to remember when performing this approach to avoid injury to the lateral cutaneous nerve of the thigh.

Hip Anterior approach(Smith-Peterson)

• The internervous plane superficially between the sartorius (supplied by the femoral nerve) and the tensor fascia Lata (supplied by the Superior gluteal nerve).

Anterior Superior Iliac Spine Avulsion

• Bony avulsion of the sartorius tendon occurs from a strong sudden pull of the sartorius with the hip in extension and the knee in flexion.
• Avulsion of the sartorius from its attachment site most commonly occurs in sprinters and other running athletes.
• The avulsion can also occur after anterior iliac crest bone graft.
• It is advisable to start harvesting the bone graft approximately 3cm from the anterior superior iliac spine to avoid weakening of the bone and avulsion fracture.
• Harvesting the bone less than 3cm of the ASIS may cause an avulsion fracture of the sartorius muscle.
• If there is a persistent hip pain after Anterior iliac crest bone graft,get an X-ray of the pelvis to check for an avulsion fracture.

Adductor Canal

• The Adductor canal (subsartorial canal)is an aponeurotic tunnel in the middle third of the thigh, extending from the apex of the femoral triangle to the opening in the adductor magnus, which is called the adductor hiatus.
• The canal contains the femoral artery, femoral vein,and the saphenous nerve,which is a branch of the femoral nerve.
• It is important to recognise the relationship of the saphenous nerve to the sartorius muscle and tendon.The saphenous nerve is posterior to the sartorius tendon.

Pes Anserine Bursa

 

• The pes Anserine Bursa is a small fluid filled sac located between the tibia and three tendons of the Sartorius,Gracilis and the Semi-tendinosus.
• The pes Anserine is the common area of insertion for the three tendons along the proximal medial aspect of the tibia.
• Innervation of the Pes Anserine muscles-
  • Sartorius -femoral nerve
  • Gracilis-obturator nerve
  • Semi tendinosis-Tibial branch of the sciatic nerve.
• Pes Anserine bursitis or “breast stroke knee” ,is an inflammatory condition of the medial knee at the pes Anserine Bursa that is common in swimmers.
• Pes Anserine bursitis is usually seen as causing pain,tenderness and localized swelling after the trauma or total knee replacement.The pain is seen below the joint line on the medial part of the proximal tibial with the bursa being deep to the tendons.