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Anatomical Variations of the Iliopsoas Muscle
Yoko Tabira1, Joe Iwanaga1,2,3,4,5,6, Aya Han1
1Division of Gross and Clinical Anatomy, Department of Anatomy, Kurume University School of Medicine.
The Kurume Medical Journal
|June 15, 2025
Summary
Anatomical variations of the iliopsoas muscle, though rare, are clinically significant. This study details three cases of iliopsoas variants, including iliacus minimus and psoas quartus muscles, highlighting their relationship with the femoral nerve.
Area of Science:
- Anatomy
- Morphology
- Surgical Anatomy
Background:
- Anatomical variations of the iliopsoas muscle are uncommon but clinically significant due to their proximity to the femoral nerve.
- Known variants include accessory iliacus, iliacus minimus, psoas tertius, and psoas quartus muscles.
Purpose of the Study:
- To describe the anatomical findings of iliopsoas muscle variants.
- To emphasize the clinical significance of these variations in relation to the femoral nerve.
Main Methods:
- Dissections of the posterior abdominal wall were performed on 95 Japanese cadavers.
- Cadavers were sourced from Kurume University School of Medicine between 2015 and 2017.
Main Results:
- Three cases of iliopsoas muscle variants were identified.
- Case 1: A variant muscle pierced the femoral nerve (FN) and joined the psoas major (PMa).
- Case 2: Another variant pierced the FN and joined the PMa tendon, categorized as iliacus minimus.
- Case 3: A bilateral variant, psoas quartus muscle, traveled posterior to the FN and united with the psoas major and iliacus muscle (IM).
Conclusions:
- A thorough understanding of iliopsoas muscle morphologic variations is essential for accurate diagnosis and treatment of femoral nerve disorders.
- Knowledge of these variations is crucial for safe lumbar and abdominal surgery.
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