Aims: The distal radius fracture model prototype has been produced as a means for teaching reduction of a distal radius fracture. In this study we aim to test the repeatability and reproducibility of the force required to correct the shortening of the radius. In addition a questionnaire was carried out to assess face validity

Methods and materials: The distal radius fracture model prototype has been designed and manufactured to simulate reduction of a dorsally displaced, radially angulated, shortened fracture of the distal radius. We designed a mounting rig for the model and used a Hounsfield tensometer to measure the degree of movement of the distal fracture fragment when various degrees of force were applied. Force was applied to reproduce correction of radial shortening. Reproducibility was tested by resetting of the tensioning device at the rear of the model. The questionnaire was constructed using a series of 5 point, verbally anchored Likert items.

Results: Mean force required for reduction was 191.4 N (Newton) (range 189.4 – 193.4N). Standard deviation for repeated measurement was 1.65 N. Graphs of force versus extension showed one consistent point of slippage which could be explained by movement in the spring tensioner for distal radial displacement. On repeated testing the model tensioning device also showed good reproducibility of results. The results for face validity showed that most people rated the model as having an appearance consistent with that of a fractured distal radius (median score for appearance 4.7, tactile propertied 4.7) but that the biomechanical properties of the reduction were not scored as highy (median score 3.9) The median score when asked about the usefulness of the model for teaching junior staff was high (4.52)

Conclusions: This prototype produces repeatable performance parameters on reduction of the fracture. Overall experience with the prototype is good but it requires further refinement.

Polymethylmethacrylate (PMMA) Acrylic Bone Cement is a polymer used to anchor the prosthesis during Joint Replacement Surgery. Arthroplasty with Bone Cement is associated with late loosening, compromising prosthetic stability leading to Revision arthroplasty. Different irrigating solutions such as Hydrogen Peroxide or Saline are used during arthroplasty. The aim of the study was to analyse the effects of Hydrogen Peroxide on the mechanical properties of Bone Cement.

Materials and Methods: Cement was mixed as per standard methods used in theatre, in a vacuum and at a temp of 18 degrees centigrade. Once the cement was mixed it was then placed in conical moulds and the exposed surface was either exposed to saline or Hydrogen Peroxide solution (6% from a standard theatre preparation). We studied the effect of Hydrogen Peroxide on Dough time, Curing time, Surface Analysis and Hardness of PMMA. Dough time was performed with latex examination gloves. Curing time was measured at 15 seconds intervals using a Vickers hardness transistor. Cement hardness was assessed using the same machine. Surface analysis was performed by preparing the samples using a grit rotaforce machine. Palacos Bone Cement was used and tests were conducted according to ASTM F-451 and ISO 5833 standards.

Results: The samples exposed to hydrogen peroxide showed an increase in the dough time in comparison to the controls from 3.5 minutes to 5 minutes. Curing time showed a difference of 13.5 minutes for the controls as opposed to 17 minutes for the HP contaminated samples. Surface hardness reduced from a mean of 17.5hv to 14.3hv after exposure to hydrogen peroxide (p< 0.05). There was increased staining of the Hydrogen Peroxide sample, with surface irregularities, and an associated increase in surface porosity. Surface porosity increased from 120um (SD 11.2) to 180um (SD 8.7) (p< 0.05).

Conclusion: We have shown that the use of hydrogen peroxide contamination of bone cement interferes with the biomechanical properties of the cement, leading to an overall reduction in strength and hardness of the cement. This may lead to an associated reduction in the strength of the bone cement interface and precipitate early micro-motion and loosening of the prosthesis.