Question

Identify the muscle marked causes flexion of hip [Images show axial and coronal CT sections of the abdomen/pelvis with a muscle marked bilaterally in the retroperitoneum]

• A. Gluteus Muscle
• B. Psoas Muscle
• C. Latissimus dorsi
• D. Multifidus

Hint:

The muscle visible bilaterally in the retroperitoneum on CT, flanking the lumbar vertebrae, and inserting into the lesser trochanter is the primary hip flexor.

Answer 1

The Correct Option is B

Step 1: Identify the muscle on CT. The CT images show axial and coronal sections of the abdomen/pelvis. The marked muscle is seen bilaterally in the retroperitoneum, lateral to the lumbar vertebral bodies and anterior to the transverse processes. This is the characteristic position of the psoas major muscle.

Step 2: Anatomy of the psoas major muscle.

• Origin: Vertebral bodies, intervertebral discs, and transverse processes of T12 to L5
• Insertion: Lesser trochanter of the femur (via the iliopsoas tendon)
• Innervation: Branches of L1-L3 roots of the lumbar plexus (femoral nerve contributions)
• Arterial supply: Lumbar arteries, iliolumbar artery, deep circumflex iliac artery
• Action: Flexion of the hip joint (primary action); lateral flexion of the lumbar spine; stabilizer of the hip

Step 3: Rule out other options.

• Gluteus muscle: located posterolaterally in the buttock region; primary action is hip extension and abduction.
• Latissimus dorsi: a muscle of the back; acts on the shoulder joint (adduction, internal rotation, extension of arm); not visible in the pelvis.
• Multifidus: deep paraspinal muscle running along the spinous processes; stabilises the spine, does not flex the hip.

Step 4: Conclusion. The retroperitoneal muscle that causes flexion of the hip, seen on CT flanking the lumbar vertebrae, is the Psoas muscle.