Osteoarticular tuberculosis occurs mostly in the weight-bearing and vulnerable area. The most common site is vertebral column, followed by knee and hip joint [1, 2], which account for more than 95% of all cases . The incidence of osteoarticular tuberculosis in the upper extremities is low, and that of acromioclavicular joint is rare. The first case of acromioclavicular joint tuberculosis was reported in 1950 , in a series of 1074 unusual lesions of tuberculosis, there was just one case of acromial end of clavicle involvement. Since the first acromioclavicular joint tuberculosis was reported, there have been less than 10 relevant case reports.
In the past, osteoarticular tuberculosis was usually secondary to pulmonary tuberculosis , and primary tuberculosis lesions were often found. In absence of pulmonary lesions, osteoarticular tuberculosis may not come to mind as the first diagnosis . However, the epidemic tendency of osteoarticular tuberculosis is changing according to clinical reports in recent years. Most patients did not accompany by pulmonary tuberculosis and systemic symptoms , resulting in more difficult diagnosis of osteoarticular tuberculosis. It was prone to misdiagnosis and missed diagnosis, especially unusual lesions of tuberculosis. According to the report , the most common manifestations were longstanding pain and functional loss in 83% unusual lesions of osteoarticular tuberculosis, which were often difficult to distinguish from osteoarthritis. In some cases, painless cold abscess can be the only clinical manifestation for a long period of time . In a retrospective study , out of 16 patients of glenohumeral tubercular osteoarthritis 14 were misdiagnosed as frozen shoulder, and the mean prediagnostic time period to come to a correct diagnosis was 14.5 months. The delayed diagnosis resulted in poor prognosis of joint function.
The incidence of isolated acromioclavicular joint tuberculosis is extremely low. The disease is occult and has no typical tuberculosis symptoms, and it may present with symptoms of painless swelling of the joint or as a discharging sinus [8, 9]. Although the joint is swollen, the skin is mostly without redness and fever, which is different from common bacterial infection: this feature is the characteristic of tuberculous arthritis . In this case, the lesion started as a papule with mild pain that subsequently ulcerated with purulent discharge, and antibiotic therapy was ineffective. Than we considered the possibility of tuberculosis, and completed imaging, cytology, pathology and other related examinations as soon as possible. Because of timely diagnosis and treatment, the patient avoided loss of joint function.
Imaging examination is an important method to diagnose osteoarticular tuberculosis, especially the application of MRI, which may help in the early diagnosis of tuberculosis and differentiation from osteomyelitis [10, 11]. Because MRI can show the severity of tuberculosis and has the characteristics of noninvasive and convenient, it plays an increasingly important role in the diagnosis of osteoarticular tuberculosis [12, 13]. In addition, it is essential to keep a high level of suspicion of tuberculosis at rare sites in order to make an early diagnosis [2, 14]. Tuberculosis should be considered as a differential diagnosis in all atypical presentations of osteoarthrosis, especially in China and India which remain as on the high burden country list for tuberculosis by WHO . But Mittal R et al.  thought that although the presentation was as a lytic lesion with periarticular osteoporosis on radiography, the definitive diagnosis of osteoarticular tuberculosis was only made based on histological or bacteriological confirmation.
Debridement is a common method to treat osteoarticular tuberculosis, especially for early tuberculosis . We believe that this operation is one of the most effective methods for the treatment of acromioclavicular joint tuberculosis, because this site is non-weight bearing and micro-motion joint, bone defect after debridement has little effect on function of the joint. Thorough debridement is the key to good prognosis. It is not recommended to suture directly if the wound is large and has much exudation, and VSD can be applied to continuous drainage after debridement. The drainage of secretions by VSD is more unobstructed than routine dressing change, which is beneficial to wound healing. In addition, it should be combined with standardized and continuous anti-tubercular chemotherapy to reduce the recurrence of tuberculosis.