The disappearance of femoral head and neck resulting from extensive bone defect caused by secondary syphilis: a case report and literature review

BACKGROUND: Treponema Pallidum (TP), the pathogen of syphilis, commonly infects bones in cases of congenital and tertiary syphilis, but it is rare in the primary and secondary stages. With its mild symptoms and rare clinical findings, it might be easy to dismiss the diagnosis of early syphilis. Usually, effective results can be achieved after the conventional strategy of antibiotic treatments, mainly penicillin. To our knowledge, our case is so far the most serious reported case of destructive bone lesion in secondary syphilis, and our treatment for the case is the first strategy using total hip arthroplasty in secondary syphilis. CASE PRESENTATION: We present the case of a 71-year-old man with local repeated pain and dysfunction in the right hip. Radiologic examinations showed the disappearance of the ipsilateral femoral head and neck. After excluding the aetiologies of cancer metastasis and tuberculosis, we confirmed the diagnosis of syphilitic arthritis. The patient received the medical treatment of antibiotics and the surgical treatment of total hip arthroplasty. At the follow-up of 1, 3, and 5.5 years after the operation, the patient presented with a pain-free and functional hip prosthesis without local signs of infection and loosening. CONCLUSIONS: This report highlights the difficulties of early diagnosis of secondary syphilis with bone involvement. Bone defect of the femur with secondary syphilis, especially at the proximal femur, was an extremely rare complication in the previous reports. Our case was the first case of a patient who experienced the disappearance of femoral head and neck caused by secondary syphilis. Follow-up after the operation proved the successful treatment of the extensive bone defect of femur by total hip arthroplasty.