Case Presentation: A 15-year-old male presented with sharp, constant back pain following a mechanical fall from standing height two days previously. He did not have any loss of consciousness and was able to ambulate following the injury. The back pain started immediately after the fall and continued to worsen over the following two days. He did not have any fevers, bowel or bladder incontinence, or any neurological symptoms. He was initially evaluated at an outside facility where computed tomography showed transmural displacement of several prongs of an inferior vena cava (IVC) filter that had been previously placed through the wall of the IVC. No fractures were noted on imaging. His history was significant for right leg osteomyelitis six years previously following a football injury. This was complicated by septic arthritis, tricuspid valve endocarditis, and disseminated Methicillin-sensitive Staphylococcus aureus infection involving multiple organ systems. He was hospitalized for 43 days and his hospital stay was complicated by post-surgical deep vein thrombosis (DVT). He had an inferior vena cava filter placed at that time due to contraindication to anticoagulation. On admission to our facility, he was afebrile. His physical examination was significant for tenderness to palpation over the T12 to L2 spinous processes with full range of motion and no step-offs or deformities. His back pain continued despite treatment with analgesics. During his hospital stay, he developed pain and paresthesia in the anterior aspect of his left thigh. He did not have any muscle weakness, and pulses and sensation remained intact. Limited magnetic resonance imaging (MRI) of the left thigh was performed and showed a significant fluid collection in the lateral femur superficial to the iliotibial band that was concerning for a left thigh abscess. Orthopedics subsequently performed irrigation and debridement of the abscess. Cultures were all negative. His inflammatory markers, which had been elevated and increasing prior to his irrigation and debridement, started trending down after the procedure. He remained afebrile and his back and leg pain improved significantly following his procedure.

Discussion: There is a broad differential for back pain in pediatric patients. Epidural and soft tissue abscesses have seldom been reported to cause back pain in this patient population. Thigh abscesses generally occur as the result of trauma or infection to local structures. There have been reports of thigh abscesses occurring as a complication after surgery, although many of those patients were immunocompromised or had a history of trauma. Associated conditions include soft tissue infections, post-traumatic hematomas, osteomyelitis, and thrombophlebitis. Similar to other patients with thigh abscesses, our patient had a history of previous trauma to his lower extremities. He also had a history of osteomyelitis as well as deep vein thrombosis, both of which likely served as risk factors. Additionally, the presence of his IVC filter could possibly have been a source of infectious spread as well.

Conclusions: Despite the rarity of this condition, it is important to consider thigh abscesses in the differential for back pain. There should be suspicion for this condition in patients with systemic symptoms and a history of immunosuppression and trauma.