Wang Joshua, Yeung Chun, Chang Eric, Bourke Jason M
New York Institute of Technology College of Osteopathic Medicine at Arkansas State University, Jonesboro, AR, USA.
Department of Biomedical & Anatomical Sciences, New York Institute of Technology College of Osteopathic Medicine at Arkansas State University, Jonesboro, AR, USA.
Am J Case Rep. 2025 May 3;26:e945927. doi: 10.12659/AJCR.945927.
BACKGROUND Psoas quartus is a rare anatomical variant of the psoas major muscle that can alter the course and branching of the femoral nerve as it descends from the posterior abdominal wall. Understanding its anatomical implications is crucial for clinicians and surgeons. CASE REPORT During a routine cadaveric dissection, we identified a unilateral psoas quartus muscle on the left side. This muscle was situated between the psoas major, psoas minor, and iliacus, originating from the transverse process of L5 and the quadratus lumborum. The femoral nerve exhibited an unusual branching pattern as it traveled around this muscle, bifurcating into medial and lateral branches before coalescing inferiorly. A review of the literature revealed only 4 prior reports of psoas quartus, suggesting it is a rare but significant variant. Its presence can contribute to nerve compression and altered biomechanics. CONCLUSIONS The presence of psoas quartus can contribute to femoral nerve compression, potentially leading to gait abnormalities and neuropathic symptoms. This case highlights the importance of recognizing such anatomical variations in clinical and surgical settings, particularly in procedures involving the lumbar plexus or femoral nerve blocks. Increased awareness of this muscle variant can aid in the diagnosis and management of femoral nerve-related pathologies, reducing the risk of iatrogenic nerve injury. Additionally, radiologists should consider this variation when evaluating imaging studies, as it can affect interpretations of femoral nerve entrapment or musculoskeletal abnormalities.
腰四头肌是腰大肌的一种罕见解剖变异，当股神经从腹后壁下行时，它可改变股神经的走行和分支。了解其解剖学意义对临床医生和外科医生至关重要。病例报告：在一次常规尸体解剖中，我们在左侧发现了一块单侧腰四头肌。该肌肉位于腰大肌、腰小肌和髂肌之间，起自L5横突和腰方肌。股神经在绕过该肌肉时呈现出异常的分支模式，在下方合并之前分为内侧支和外侧支。文献回顾显示，此前仅有4例腰四头肌的报道，表明它是一种罕见但重要的变异。其存在可导致神经受压和生物力学改变。结论：腰四头肌的存在可导致股神经受压，可能导致步态异常和神经病变症状。本病例强调了在临床和手术环境中识别此类解剖变异的重要性，特别是在涉及腰丛或股神经阻滞的手术中。提高对这种肌肉变异的认识有助于股神经相关疾病的诊断和管理，降低医源性神经损伤的风险。此外，放射科医生在评估影像学检查时应考虑这种变异，因为它可能影响对股神经卡压或肌肉骨骼异常的解读。
