Since total joint arthroplasty is currently one of the most frequently performed and most successful surgical procedures in orthopaedics. Rapid and accurate periprosthetic joint infection (PJI) diagnosis is important. Chang Gung Memorial Hospital (CGMH) is the largest hospital in Taiwan, more than 3000 joint replacement surgeries were completed at CGMH in 2015. Because Staphylococcus aureus (S. aureus) is the leading cause of bone infections including PJIs. Cultures have limited sensitivity and time consuming in the diagnosis of PJI, especially in low-grade infections. Thus, we choose real-time PCR assay targeting spa gene of S. aureus in PJI and applied it to synovial fluid obtained from hip/knee revision arthroplasty, and we also compare the results to those with periprosthetic deep tissue culture obtained at revision arthroplasty. We studied 18 subjects with knee (n=7) or hip (n=11) total joint revision arthroplasty; 12 subjects had PJI by a standardized definition. The real-time PCR method targeting spa gene of S. aureus in synovial fluid is more sensitive and faster (about 2 hours) than tissue culture for the S. aureus diagnosis of prosthetic hip and knee infection PJI diagnosis with definition of S. aureus.