Background: Despite the use of modern instruments in total knee arthroplasty, component malalignment remains a problem. Whether a computer-assisted implantation technique can improve the accuracy of the spatial positioning of an implant is a matter of debate. The objective of this study was to determine whether computer-assisted total knee arthroplasty is superior to the conventional surgical method with regard to the precision of implant positioning. Methods: The spatial positioning of the implant in sixty total knee arthroplasties (thirty-two imageless computer-assisted and twenty-eight conventional implantations) was determined three-dimensionally with use of computed tomographic measurement, which allowed derotation and full extension of the knee in order to avoid projection-related imaging errors. Results: The overall mechanical axis showed a range of between 4.8° of valgus and 6.6° of varus alignment in the frontal plane for conventionally implanted arthroplasty components compared with a significantly smaller range of between 2.9° of valgus and 3.1° of varus alignment for computer-assisted implantations (p = 0.004). In relation to the tibial implant, the mean deviation (and standard deviation) from the mechanical axis was 2.0° ± 1.7° for the conventional surgical method and 1.4° ± 0.9° for the navigated implantation. The rotational deviation from the referenced axis of the femoral component was between 3.3° of internal rotation and 5.0° of external rotation for the conventional implantation method, with a mean deviation of 0.1° ± 2.2°. Femoral components implanted with computer assistance showed a deviation of between 4.7° of internal rotation and 2.2° of external rotation, with a mean deviation of 0.3° ± 1.4°. Conclusions: In this study, with our technique of filtering out projection-related imaging errors, computer-assisted implantation of total knee replacements improved the frontal and sagittal alignment of the femoral component but not of the tibial component. We found that the rotational alignment of the component was not improved through navigation by solely referencing to the epicondylar axis for the femur and the tuberosity for the tibia. Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Acements during 2005 to 2010 at two high-volume arthroplasty centers. A revision was defined as the replacement of at least one prosthetic component. In the descriptive analysis, polyethylene wear, aseptic loosening, periprosthetic infection, malalignment, instability, arthrofibrosis, extensor mechanism deficiency, periprosthetic fracture, and retropatellar arthritis were given as the failure mechanism associated with an early, intermediate, or late time interval (less than one year, one to three years, and more than three years, respectively) after the index total knee arthroplasty. Results: Three hundred and fifty-eight revision total knee arthroplasties were included. Of those revisions, 19.8% were performed within the first year after the index arthroplasty. The most common indications for revision, besides aseptic loosening (21.8%), were instability (21.8%), malalignment (20.7%), and periprosthetic infection (14.5%). Revisions due to polyethylene wear (7%) rarely occurred. In the early failure group, the primary causes of revision were periprosthetic infection (26.8%) and instability (23.9%). In the intermediate group, instability (23.3%) and malalignment (29.4%) required revision surgery, whereas late failure mechanisms were aseptic loosening (34.7%), instability (18.5%), and polyethylene wear (18.5%). Conclusions: Aseptic loosening, instability, malalignment, and periprosthetic infection continue to be the primary failure mechanisms leading to revision surgery. Contrary to previous literature, the results in the present study showed a substantial reduction in implant-associated revisions such as those due to polyethylene wear. Failure mechanisms that occur persistently early and in the intermediate term, such as periprosthetic infection, instability, and malalignment, remain common causes of revision surgery. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence....

Blood vessel formation is a prerequisite for bone healing. In this study, we tested the hypothesis that a delay in bone healing is associated with an altered regulation of blood vessel formation. A tibial osteotomy was performed in two groups of sheep and stabilized with either a rigid external fixator leading to standard healing or with a highly rotationally unstable one leading to delayed healing. At days 4, 7, 9, 11, 14, 21, and 42 after surgery, total RNA was extracted from the callus. Gene expressions of vWF, an endothelial cell marker, and of several molecules related to blood vessel formation were studied by qPCR. Furthermore, histology was performed on fracture hematoma and callus sections. Histologically, the first blood vessels were detected at day 7 in both groups. mRNA expression levels of vWF, Ang1, Ang2, VEGF, CYR61, FGF2, MMP2, and TIMP1 were distinctly lower in the delayed compared to the standard healing group at several time points. Based on differential expression patterns, days 7 and 21 postoperatively were revealed to be essential time points for vascularization of the ovine fracture callus. This work demonstrates for the first time a differential regulation of blood vessel formation between standard and mechanically induced delayed healing in a sheep osteotomy model. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

The correct diagnosis of a prosthetic joint infection (PJI) is crucial for adequate surgical treatment. The detection may be a challenge since presentation and preoperative tests are not always obvious and precise. This prospective study was performed to evaluate a variety of pre- and intraoperative investigations. Furthermore a detailed evaluation of concordance of each preoperative diagnosis was performed, together with a final diagnosis to assess the accuracy of the pre-operative assumption of PJI.