The aims of this study were to evaluate the incidence of local argyria in patients with silver-coated megaprostheses and to identify a possible association between argyria and elevated levels of silver both locally and in the blood. Between 2004 and 2011, 32 megaprostheses with silver coatings were implanted in 20 female and 12 male patients following revision arthroplasty for infection or resection of a malignant tumour, and the levels of silver locally in drains and seromas and in the blood were determined. The mean age of the patients was 46 years (10 to 81); one patient died in the immediate post-operative period and was excluded.

Seven patients (23%) developed local argyria after a median of 25.7 months (interquartile range 2 to 44.5). Patients with and without local argyria had comparable levels of silver in the blood and aspiration fluids. The length of the implant did not influence the development of local argyria. Patients with clinical evidence of local argyria had no neurological symptoms and no evidence of renal or hepatic failure. Thus, we conclude that the short-term surveillance of blood silver levels in these patients is not required.

Cite this article: Bone Joint J 2013;95-B:988–92.

Aim

Accurate and reliable patient information plays a crucial role in the multidisciplinary treatment of malignancies helping to ensure compliance of the patients and their relatives with often long-lasting and stressful treatment. The English version of the online encyclopaedia Wikipedia has been recently reported to be the prominent source of online health information. However, there is little information concerning the quality of information found in Wikipedia.

Introduction: Infections associated with prosthetic joints cause significant morbidity and account for substantial costs for health care systems. The management of prosthetic joint infections is less standardized, because of the variable clinical presentations and the lack of data from randomized, controlled trials.

We evaluated the results of surgical one stage versus two stage exchange of patients diagnosed positive for prosthetic infection following total hip replacement in correlation with a classification described by Mc Pherson.

Material and Methods: 94 patients were diagnosed positive for prosthetic joint infection following total hip replacement in the years 1995 to 2004: gender distribution was 45 male and 49 female patients. 37 patients were treated with a one stage exchange, 57 patients underwent a two step procedure. Patients were further divided into two groups following the mentioned classification described by Mc Pherson as infection type I+II and III. Further characterisation was performed following systemic host grade (A versus B+C) and local extremity grade 1 versus 2+3.

Results: Eradication of prosthetic infection was achieved in 94, 5% (n=52) within the group of two stage exchange and 56, 8% (n=21) of patients treated with a one stage procedure. Outcome of patients following a one stage or a two step exchange was overall significantly different with p< .001. Further deviations between the described two procedures were noted in the subgroups following the classification described by Mc Pherson. A benefit of patients who underwent a two step procedure was seen according the severity of the classification following Mc Pherson.

Conclusion: Eradication rate of prosthetic joint infections differs statistically significant overall and in the subgroups following Mc Pherson in dependence of the surgical procedure. For this reason the individual surgical procedure should be geared to an algorithm, following the classification described by Mc Pherson.

Introduction: Rotating hinge knee prostheses are designed to provide a stable knee reconstruction when the intrinsic soft-tissue stability of the knee had been lost as a result of tumor resection, multiple knee replacements, trauma or surgical reconstruction. Instability is the main risk factor for implant’s dislocation. We performed a biomechanical analysis to establish the association between design of the central rotational stem (length and taper) and the implant’s stability, using a self constructed biomechanical apparatus on a test bench in the laboratory.

Materials and Methods: The lengths and tapers of the central rotational stem of three different rotating hinge knee implants (LPS/M.B.T. (DePuy)-cylindrical, length: 46mm, taper: 0°; S-ROM Noiles (DePuy) -conical, length: 46mm, taper: 5°; GMRS (Howmedica) -cylindrical, length: 47mm, taper: 0°) were measured using a self-constructed biomechanical testing device. The degree of tilting of the central rotational stem within the vertical post-in channel by extending the distraction was measured as well the maximum amount of distraction before the stem’s dislocation.

Results: The GMRS implant design was superior to the LPS/M.B.T. and the S-ROM Noiles implant design concerning stability and maximum amount of distraction before dislocation (38 vs. 27 vs. 26 mm). The GMRS system had a steep rising distraction-angular displacement curve until the dislocation at 38mm occurred while the laxity curve of S-ROM Noiles showed a poor increasement. Besides early high laxity it required only 26mm of distraction to dislocate.

Conclusions: Our conclusion is that rotating hinge prostheses with a short and markedly tapered central rotational stem have the highest instability/angular laxity at any given amount of distraction. Such knee prostheses should be used with caution in patients after excessive soft tissue resection. A long and cylindrical central rotational stem seems to prevent early instability and implant’s dislocation.