Culture of tissue samples obtained peri-operatively is ‘the gold standard’ for determining the presence of infection in prosthetic revision surgery. The growth of identical bacterial strains in three or more specimens strongly indicates an infected prosthesis. With routine microbiological culture techniques, identification of different phenotypes of coagulase negative staphylococcus (CNS) will be interpreted as either contamination or a polybacterial infection. At our clinic, different phenotypes of CNS are cultured in approximately 20% of patients operated with a two-stage revision due to a chronic prosthetic infection.

We studied the genotype of different phenotypes of CNS cultured in specimens obtained from prosthetic joints.

We analysed 22 cases, where different phenotypes of CNS were cultured in tissue, and joint fluid specimens were collected peri-operatively. The pre-operative diagnosis was chronic prosthetic infection (n=16), aseptic revision (n=5) and primary prosthesis (n=1). Different phenotypes were assessed by colony morphology and/or antibiogram. Pulsed-field gel electrophoresis (PFGE) was employed to identify and compare the genotypes.

In 16 out of 22 cases (73 %), PFGE unveiled that phenotypically different strains of CNS belonged to the same genotype. Of these 16 cases 7 had different antibiograms. In the other group (6/22), phenotypically different strains of CNS did not belong to the same genotype. In the 16 cases with different phenotypes belonging to the same genotype, gentamicin bone cement had previously been used in 15 cases. In the other group (6/22), gentamicin bone cement had not been used previously in any case (p < 0.01, chi-square test).

Phenotypically different strains of CNS identified by routine microbiological techniques should not be classified readily as contamination or as a mixed bacterial infection in prosthetic surgery. A particular precaution should be taken in the case of patients who had previously been operated on with use of gentamicin-loaded bone cement.

Aims: The aim of this study was to measure implant migration and bone remodelling of the proximal femur two years after insertion of a customized or a standard femoral stem. Materials and methods: In a prospective, randomized study 26 hips (26 patients) have been examined postoperatively and after 3, 6, 12 and 24 months using radiostereometry (RSA) and DEXA. Thirteen hips received a customized femoral stem (Unique, SCP as) and 13 hips received a standard uncemented femoral stem (ABG¨, Stryker-Howmedica). An uncemented acetabular cup (Duraloc¨, DePuy) was used in all hips. The mean age of the patients was 55 (24–67) years. Results: The median displacement of the custom/ standard femoral stems was 0.04/0.01 mm along the - medial-lateral axis, 0.08/0.02 mm along the proximal-distal axis and 0.03/0.08 mm along the anterior-posterior axis, respectively. Statistically, there was no difference between the two groups. One custom stem subsided 5.2 mm at one year, but showed no further migration at two years. The mean decrease in bone mineral density (BMD) in all Gruen zones was 6% in the Custom-group and 7% in the ABG-group. The most pronounced bone loss was seen in Zone 7 and was 21% and 25% for the two groups, respectively. Discussion: We found no statistically signiþcant difference in short-term stem migration comparing a customized and a standard, uncemented femoral stem. Furthermore, the changes in bone mineral density were almost equal in femurs with either type of prosthesis.

We studied the effect of transcutaneous electrical nerve stimulation (TENS) on stump healing and postoperative and late phantom pain after major amputations of the lower limb. A total of 51 patients were randomised to one of three postoperative treatment regimens: sham TENS and chlorpromazine medication, sham TENS only, and active low frequency TENS. There were fewer re-amputations and more rapid stump healing among below-knee amputees who had received active TENS. Sham TENS had a considerable placebo effect on pain. There were, however, no significant differences in the analgesic requirements or reported prevalence of phantom pain between the groups during the first four weeks. The prevalence of phantom pain after active TENS was significantly lower after four months but not after more than one year.