Effective Radiotherapy for Bilateral Hip Flexion Dysfunction Due to Vertebral Metastasis at the Origin of the Psoas Major: A Case Report.

Hip flexion dysfunction caused by neoplastic involvement of the psoas muscle is rare, and bilateral cases are exceedingly uncommon. Functional decline may result not only from direct tumor invasion but also from surrounding inflammation and edema. However, reports of rapid functional improvement following radiotherapy are limited. We present a case of a man in his 70s who developed bilateral hip flexion dysfunction following initiation of chemotherapy for esophagogastric junction cancer with multiple liver metastases. Several months later, L2-L4 vertebral metastasis resulted in bilateral hip flexion weakness (Manual Muscle Test (MMT), 3/5), leading to difficulty walking. He had no sensory deficits or bladder/bowel dysfunction, with minimal pain and motor dysfunction being the predominant feature. Imaging demonstrated intermediate-attenuation areas around the vertebral bodies and increased attenuation of the fat planes surrounding the psoas muscles, but no clear evidence of direct muscular invasion. The patient underwent palliative radiotherapy to the L2-L4 region with a total dose of 30 Gy in 10 fractions. Within one week of treatment completion, bilateral psoas strength improved to MMT 5/5, with marked recovery of hip flexion function. Functional improvement was sustained despite only minimal radiological tumor regression, with functional recovery preceding radiological response. This suggests that the primary therapeutic mechanism may have been control of inflammation and edema through the anti-inflammatory effects of radiotherapy. This improvement persisted for at least three months, and the patient died several months later. This case represents an exceptionally rare instance of bilateral hip flexion dysfunction secondary to spinal metastasis adjacent to the psoas origin, showing a clinically meaningful response to radiotherapy. It underscores the importance of muscle-related mechanisms in psoas dysfunction and demonstrates the therapeutic efficacy of radiotherapy in such conditions.