Background

Total knee arthroplasty has been performed even for severe valgus knee. All ligaments around knee must be balanced to obtain good clinical results. Especially medial collateral ligament plays a role as a stabilizer. For severe valgus knee, however, deep medial collateral ligament (dMCL) located closely to the articulating tibial surface [Fig. 1] can be damaged by bone resection in standard tibial osteotomy which may leads to progress valgus deformity.

Hi-flex insert was developed in part for the needs of Asian and Islamic people’s life style, because of the traditional floor sitting style in a daily life. We studied about the short term results of Genesis2 with Hi-flex insert in Japanese life style for 57knees in 39patients that were passed more than 2 years post-operation between 2004 and 2006. The mean age at implantation was 72.1. From the patients reviewed the mean pre-operative Japanese Orthopaedic Association score was 51, compared to 81 at last follow up. The mean pre-operative flexion was 113, compared to 124 at last follow up. Almost all patients had changed their life style basically from Japanese (floor sitting) to Western (chair sitting) before operation because of their knee problems. But 30% of the patients sometimes wanted to sit on the floor traditionally before the operation, and 83% of these patients can sit also after the operation. Japanese traditional life styles with the knee flexed deeply can be achieved by Genesis2 with Hi-flex insert satisfactorily limited to the patients who could do also before the operation. But when the patients sit on the floor, the complicated stress to the implants and insert were unknown. At the present time, we must advice to the patients who can sit on the floor about the motion that can reduce the stress to the implants and insert.

The treatment of rheumatoid arthritis (RA) has recently seen a paradigm shift with the introduction of biologic therapy, but there is concern that this will result in an increased incidence of infection. The occurrence of infection in RA patients who have undergone biologic therapy has recently been documented in a few reports, but this is the first report of Salmonella infection after total knee arthroplasty (TKA) in a RA patient receiving etanercept therapy. Here we report the successful treatment of a rare case of Salmonella septic arthritis.

A 61-year-old man with a 4-year history of RA was treated with methylprednisolone and methotrexate, and he consulted us because of right gonalgia. Treatment with infliximab was started, but as this was not effective, his medication was changed sequentially to etanercept 6 months later. Finally, TKA was performed on the right knee with antibiotic-loaded acryl cement (ALAC). The postoperative course was uneventful, etanercept was administered routinely from the 2nd postoperative week. The patient was discharged after 4 weeks. Five weeks after TKA, however, the patient visited us because of acute swelling and tenderness around the right knee. His laboratory values included a white blood cell count of 9300/mm3, an erythrocyte sedimentation rate of 81.0 mm/h and a C-reactive protein level of 11.3 mg/dl. Fluid obtained by joint aspiration was cloudy and dark-yellow, and prosthetic joint infection was diagnosed. The patient underwent emergency debridement by arthroscopic surgery, followed immediately by injection of 0.5 g carbapenem every 12 hours and continuous closed irrigation-suction of the joint for 2 weeks. Culture of the joint fluid revealed Salmonella enteritidis infection, which was not sensitive to aminoglycoside which we used as ALAC. The patient was treated with intravenous carbapenem for 3 weeks, oral levofloxacin at a daily dose of 300 mg for 2 weeks successively, and oral minocycline at 200 mg daily for 3 months. At follow-up 12 months after surgery, physical and blood examinations and plain radiographs demonstrated no recurrence of the infection, and the patient has resumed taking etanercept. The range of flexion in the treated knee is 0 to 145 degrees.

Salmonella arthritis is classified as septic arthritis and reactive arthritis, and septic arthritis is more likely if Salmonella is identified by culture of joint fluid. Salmonella septic arthritis has not been considered an intraoperative contaminant during joint replacement. Recently, it has become apparent that biologic therapies can play major roles in the pathogenesis of RA, and also that immuno-suppressive drugs may become risk factors for Salmonella septic arthritis. In conclusion, our patient had a successful outcome after prompt debridement and treatment with appropriate antibiotics, without the need for implant removal. It is important to be mindful of the possibility of infection and to carry out surgery immediately if a patient presents with symptoms after biologic therapy.