Monitoring the quality of total hip replacement in a tertiary care department using a cumulative summation statistical method (CUSUM).

The purpose of this study was to define immediate post-operative 'quality' in total hip replacements and to study prospectively the occurrence of failure based on these definitions of quality. The evaluation and assessment of failure were based on ten radiological and clinical criteria. The cumulative summation (CUSUM) test was used to study 200 procedures over a one-year period. Technical criteria defined failure in 17 cases (8.5%), those related to the femoral component in nine (4.5%), the acetabular component in 32 (16%) and those relating to discharge from hospital in five (2.5%). Overall, the procedure was considered to have failed in 57 of the 200 total hip replacements (28.5%). The use of a new design of acetabular component was associated with more failures. For the CUSUM test, the level of adequate performance was set at a rate of failure of 20% and the level of inadequate performance set at a failure rate of 40%; no alarm was raised by the test, indicating that there was no evidence of inadequate performance. The use of a continuous monitoring statistical method is useful to ensure that the quality of total hip replacement is maintained, especially as newer implants are introduced.

Enhanced bone regeneration and formation around implants using guided bone regeneration.

This study investigated the use of a prototype expanded polytetrafluoroethylene membrane attached to bone with butyl-cyanoacrylate, in facilitating guided bone regeneration into bone defects and around titanium screws in rabbit femora. Two experimental models were used to assess bone growth. The first model investigated two unicortical defects in each femora. The second was bone growth in a 500-micron engineered space around one transcortical titanium screw. In the first model there was a significant increase in bone formation at 1 and 2 months in the membrane groups (p < 0.01) as compared to the controls. In the second model the percentage of bone in contact with the implant was significant at 1 and 2 months in the defects covered with membrane compared to the uncovered defects. The uncovered defects had fibrous tissue adherent to the implant continuous with the overlying soft tissue. Our study demonstrated three points: this membrane can be used to increase bone regeneration into defects, this technique allows bone to grow directly around an implant, and butyl-cyanoacrylate can be used in deep soft tissue and bone applications without any apparent deleterious effects.