We investigated whether training doctors to classify proximal fractures of the humerus according to the Neer system could improve interobserver agreement. Fourteen doctors were randomised to two training sessions, or to no training, and asked to categorise 42 unselected pairs of plain radiographs of fractures of the proximal humerus according to the Neer system. The mean kappa difference between the training and control groups was 0.30 (95% CI 0.10 to 0.50, p = 0.006). In the training group the mean kappa value for interobserver variation improved from 0.27 (95% CI 0.24 to 0.31) to 0.62 (95% CI 0.57 to 0.67). The improvement was particularly notable for specialists in whom kappa increased from 0.30 (95% CI 0.23 to 0.37) to 0.79 (95% CI 0.70 to 0.88). These results suggest that formal training in the Neer system is a prerequisite for its use in clinical practice and research.

Displaced four-part fractures comprise 2-10 % of all proximal humeral fractures. The optimal treatment is unclear and randomised trials are needed. The conduct and interpretation of such trials is facilitated by a reproducible fracture classification. We aimed at quantifying observer agreement on the classification of displaced four-part fractures according to the Neer system. Published and unpublished data from five observer studies were reviewed. Observers agreed less on displaced four-part fractures than on the overall Neer classification. Mean kappa values for interobserver agreement ranged from 0.16 to 0.48. Specialists agreed slightly more than fellows and residents. Advanced imaging modalities (CT and 3D CT) seemed to contribute more to classification of displaced four-part patterns than in less complex fracture patterns. Low observer agreement may challenge the clinical approach to displaced four-part fractures and poses a problem for the interpretation and generalisation of results from future randomised trials.

The genotoxicity of conventional polymethylmethacrylate (PMMA) and a new formulation of bone cement: methylmethacrylate/n-decylmethacrylate/isobornylmethacrylate (MMA/DMA/IBMA) were tested by micronucleus test and reverse mutation assays of Salmonella typhimurium (Ames test). In extracts from cement pellets (37 degrees, 72 hr) with water and water/ethanol the concentration of MMA was reduced by 13-19 times with the new formulation and the concentrations of accelerators were reduced by 4-5 times. New chemical constituents (DMA, IBMA, dihydroxy-propyl-p-toluidine) were found in negligible concentrations. In the micronucleus test all three cement brands were found non-mutagenic and in the Ames test scattered increased revertant ratios were found without differences between the three brands. The new formulation does not possess any increased risk of genotoxicity.

We investigated whether training doctors to classify proximal fractures of the humerus according to the Neer system could improve interobserver agreement. Fourteen doctors were randomised to two training sessions, or to no training, and asked to categorise 42 unselected pairs of plain radiographs of fractures of the proximal humerus according to the Neer system. The mean kappa difference between the training and control groups was 0.30 (95% CI 0.10 to 0.50, p = 0.006). In the training group the mean kappa value for interobserver variation improved from 0.27 (95% CI 0.24 to 0.31) to 0.62 (95% CI 0.57 to 0.67). The improvement was particularly notable for specialists in whom kappa increased from 0.30 (95% CI 0.23 to 0.37) to 0.79 (95% CI 0.70 to 0.88). These results suggest that formal training in the Neer system is a prerequisite for its use in clinical practice and research.