Postinfectious ankylosis of the knee after bacterial arthritis following routine anterior cruciate ligament (ACL) reconstruction

AIMS AND OBJECTIVES: Knee arthroscopy is a very common surgical procedure. It belongs to the most frequently performed procedures in orthopedics and traumatology and is considered to have a low complication rate. The risk of postoperative knee infection following ACL reconstrucion is estimated 1-2 %. Thereby the ACL reconstruction cannot always be preserved. Persistent defects after healing and postinfectios osteoarthritis are observed. We present the case of an adolescent patient suffering from postoperative knee infection following routine ACL reconstruction, who is developing - while infection is decreasing - a complete bony ankylosis of the knee, clinically meaning a severe constraint to joint function with complete stiffness of the knee. MATERIALS AND METHODS: The 13-year-old male patient sustained a distorsion of the right knee during sports at school, after clinical examination magnetic resonance tomography showed a complete tear of the ACL. Single bundle ACL reconstruction was done using autologous hamstrings in Transfix technique. After 5 days at hospital the patient was discharged without any complications. Shortly afterwards the patient was admitted to hospital again presenting a postoperative knee infection. After primary operative revision the patient was shifted to our intensive care unit in a septic condition for stabilization. During 4 month of stay at our hospital multiple operative revisions were performed as arthrotomy, debridement, insertion of antibiotic carriers, complete removal of the autograft and total synovectomy. We found a severe bacterial infection (staphylococcus aureus) of the knee joint, classified Gaechter IV, histopathologically mostly avital cartilage tissue and chronic synovialitis. After decrease of the infection we could discharge the patient from hospital. RESULTS: During the following 8 month under ongoing physiotherapy the patient was developing an increasing stiffness of the knee, finally fixed at 30 degrees of flexion and with a relative shortness of the leg of 4 cm. X-rays were showing an advancing bony bridging of the joint space, meaning a spontaneous ankylosis. As mobility was good the patient declined any further operations, e.g. surgical fusion of the knee in a favourable position. Considering the age of the patient and the previous infection arthroplasty was not indicated at that time. The Patient finally was able to go to school again, impairment of earning capacity was estimated 40 %. CONCLUSION: Although knee arthroscopy has a low complication rate, preoperatively the knee infection and possible severe restricting sequelae have to be considered. Early diagnosis and treatment of postoperative infections of the knee are determining the prognosis. Even if the correct surgical procedure at the right time is done and the adaequate follow up care is chosen there may result a certain loss of function. Ankylosis of the knee as the terminal stage after postoperative infection following ACL reconstruction is very rare and is presented clearly in this case report.