Introduction: Staphylococcus aureus is a major cause of chronic infections and causes particular problems in relation to implanted prostheses. Biofilm formation on abiotic surfaces affords bacteria innate protection from opsonophagocytosis and antibiotic agents and complicates the eradication of infection from bone and implanted prostheses. Increased concentrations of sodium, the major extracellular cation, have previously been implicated in increased biofilm formation in Staphylococcus aureus. In this study we demonstrate that increased concentrations of potassium, the major intracellular cation, also causes a significant increase in biofilm formation. Furthermore we also show that halide stress also leads to a primary increase in penicillin resistance in Staphylococcus aureus. Finally we demonstrate that pbp4, a key gene in cell wall synthesis, is down-regulated under sodium and potassium stress.

Methods: Staphylococcus aureus ATCC 9144 was cultured in broth supplemented with variable amounts of potassium chloride and sodium chloride. Biofilm formation was investigated in 96-well microtiter plates using a standard technique. Antibiotic resistance was investigated using graduated E-test strips. Gene transcription was assessed using RT-PCR.

Results: There was a positive correlation between biofilm formation and increased concentrations of sodium and potassium. Biofilm formation was noted to be even greater under potassium stress than under sodium stress. Sodium stress also lead to a five-fold increase in penicillin resistance in naïve Staphylococcus aureus cells. A key gene involved in cell wall production (pbp4) was down-regulated under sodium (p = 0.03) and potassium (p = 0.03) stress.

Discussion: Cellular injury or insult can lead to cell necrosis and lysis. The intracellular concentration of potassium is 30 times higher than that of the surrounding extracellular fluid. Hence, cell necrosis leads to markedly increased local concentrations of potassium. These experiments show that an increase in potassium concentration leads to an increase in biofilm formation. This suggests that biofilm formation and hence infection of implanted prostheses may be more likely in areas of major tissue trauma such as large resections and revisions. Furthermore, cellular stress leads to increased resistance to penicillin, a cell wall active antibiotic, in naïve cells which may nullify prophylaxis and complicate bacterial eradication in vivo. Finally we postulate a link between the experimental rise in penicillin resistance and the down-regulation of pbp4 demonstrated by RT-PCR under the same halide stresses.

Introduction: Among the pantheon of medical errors, wrong site surgery (WSS) is thankfully rare. However, the results can be devastating particularly if amputation is the proposed surgery. WSS can occur due to simple mistakes in communication between patient and surgeon. This project looks at one particular cause of such miscommunication: toe identification.

Method: 100 consecutive patients were asked to label their toes. The first 50 were asked to label their left foot, the subsequent 50 their right. Patients were not asked to number or name their toes as it was felt that this could bias their answers. Instead the patients were asked to imagine a hypothetical situation in which they had pain in their toes. They were asked to explain which toe was painful, as if over the phone so that they were unable to point and thus had to label their toes. No prompting was given.

Results: Disagreement between patient and professional terminology was stark. Overall, 3% of patients incorrectly labelled the little toe and a staggering 26% mislabelled the ring toe. 10% gave a contrary label to the middle toe while 17% mislabelled the index toe. The great toe caused least problems with only 2% of patients incorrectly labelling it. Patients who numbered their toes were much more likely to mislabel them than those who named them.

Conclusions: There is a huge discrepancy between the terms used by doctors and patients to label toes, increasing the chances of miscommunication and WSS. This study highlights the need for unified terminology amongst the orthopaedic profession. We suggest using the terms great, index, middle, ring and little toes. Numbering the toes should be avoided, as numbers are used in wildly contradictory ways by doctors and patients.

The purpose of this study was to review the outcomes of patients treated with injectable calcium phosphate cement (Norian SRS, Norian Corporation, Cupertino, California) for contained bone defects after resection of benign or low-grade malignant bone tumours.

The clinical records and radiographs of 17 patients who had been treated with calcium phosphate cement were reviewed, looking for incorporation into bone, reabsorption of the material and complications.

The 17 patients had a mean age of 29.8 years (range 7 to 64). The diagnosis was giant cell tumour in 9 cases, fibrous dyplasia in 2, low grade chondrosarcoma in 2, and one each of enchondroma, chondromyxoid fibroma, osteofibrous dysplasia, and chondroblastoma. The tibia was involved in 9 cases, the femur in 6 and the radius in 2. The mean follow up was 11 months (range 3 to 25).

The material is radioopaque and well visualised on plain radiographs. In most cases, incorporation of the material into the bone structure appeared good, but there was little absorption of the material during the followup available. The exceptions were 2 cases in which the material was absorbed following local recurrence of giant cell tumour.

One fracture associated with a giant cell tumour healed well in the presence of the material. In three patients, there were clinical and radiological features at follow up suggestive of periostitis related to the material. In one case a florid effusion of the knee may have been due to the material.

Injectable calcium phosphate cement may have a role in the management of contained defects requiring mechanical support following resection of benign or low-grade malignant tumours of bone. However, problems with periostitis, possibly synovitis and absorption in the presence of local recurrence should be considered.