A consecutive series of 235 total knee arthroplasties using the PFC system was followed prospectively for at least ten years in 186 patients. The operation was for osteoarthritis in 150 knees, for rheumatoid arthritis in 83, and for Paget’s disease and femoral osteonecrosis in one knee each. At the latest review 56 patients had died, fi ve were too ill to assess and three could not be traced. The PFC knee replacement utilised was a nonconforming posterior-cruciate-retaining prosthesis with a polyethylene insert which is fl at in the sagittal plane. The patella was resurfaced using a metal-backed component in 170 cases, but later in the series we used an all-polyethylene component in 22 knees; 43 patellae were not resurfaced. The survival without need for reoperation for any reason was 90% at ten years. Nineteen revisions were component-related due to failure of nine metal-backed patellae, nine polyethylene inserts, and one unresurfaced patella; two reoperations were for synovectomy (one for recurrent haemarthrosis and one for recurrent rheumatoid synovitis) and three were for metastatic joint infection. There were no revisions for aseptic loosening of femoral or tibial components, or the all-polyethylene patellar replacement. The PFC system provides good and predictable results in tricompartmental arthritis of the knee. Loosening appeared to be negligible, but there were wear-related problems in 8%. The change from a metal-backed patella and an increase in the contact area of the tibial insert should provide further improvement by minimising wear

Aims

Currently, the US Center for Medicaid and Medicare Services (CMS) has been testing bundled payments for revision total joint arthroplasty (TJA) through the Bundled Payment for Care Improvement (BPCI) programme. Under the BPCI, bundled payments for revision TJAs are defined on the basis of diagnosis-related groups (DRGs). However, these DRG-based bundled payment models may not be adequate to account appropriately for the varying case-complexity seen in revision TJAs.

The purpose of this study was to compare the diagnostic accuracy for the detection of infection between the culture of fluid obtained by sonication (SFC) and the culture of peri-implant tissues (PITC) in patients with early and delayed implant failure, and those with unsuspected and suspected septic failure. It was hypothesised that SFC increases the diagnostic accuracy for infection in delayed, but not early, implant failure, and in unsuspected septic failure. The diagnostic accuracy for infection of all consecutive implants (hardware or prostheses) that were removed for failure was compared between SFC and PITC. This prospective study included 317 patients with a mean age of 62.7 years (9 to 97). The sensitivity for detection of infection using SFC was higher than using PITC in an overall comparison (89.9% versus 67%, respectively; p < 0.001), in unsuspected septic failure (100% versus 48.5%, respectively; p < 0.001), and in delayed implant failure (88% versus 58%, respectively; p < 0.001). PITC sensitivity dropped significantly in unsuspected compared with suspected septic failure (p = 0.007), and in delayed compared with early failure (p = 0.013). There were no differences in specificity.

Sonication is mainly recommended when there is implant failure with no clear signs of infection and in patients with delayed implant failure. In early failure, SFC is not superior to PITC for the diagnosis of infection and, therefore, is not recommended as a routine diagnostic test in these patients.

Cite this article: Bone Joint J 2013;95-B:244–9.

A new generation of knee prostheses has been introduced with the intention of improving post-operative knee flexion. In order to evaluate whether this goal has been achieved we performed a systematic review and meta-analysis. Systematic literature searches were conducted on MEDLINE and EMBASE from their inception to December 2007, and proceedings of scientific meetings were also searched. Only randomised, clinical trials were included in the meta-analysis. The mean difference in the maximum post-operative flexion between the ‘high-flex’ and conventional types of prosthesis was defined as the primary outcome measure. A total of five relevant articles was identified.

Analysis of these trials suggested that no clinically relevant or statistically significant improvement was obtained in flexion with the ‘high-flex’ prostheses. The weighted mean difference was 2.1° (95% confidence interval −0.2 to +4.3; p = 0.07).