Caudal regression: a review of seven cases, including the mermaid syndrome

Caudal regression consists of sacral agenesis combined with variable lower extremity deformities. The patients have contractures of the lower extremities, hip dislocations, neurologic impairment, and spine instability. Treatment consists of soft tissue releases, osteotomies, or orthotics. The goal of orthopaedic intervention is proper seating and standing, which may be achieved without amputation. In our patients, the lower extremity deformities were corrected surgically, but long-term function is unknown. We report the problems and treatment of seven patients with caudal regression syndrome, including the only known survivor with sirenomelia (mermaid syndrome), who underwent separation of the lower extremities.