Introduction: Standard treatment for distal tibia fractures is the fixation with locking compression plates. Locking plate fixation has revolutionized fracture treatment in the last decade and may be ideally suited for a bridging plate osteosynthesis. This technique allows some controlled axial fracture motion, what essential for secondary bone healing is. A disadvantage of the locking plate technique seems to be an unsymmetrical micro motion along the fracture gap. The micromotion at the far cortex side is much larger than at the near cortex side (near the plate). It is supposed to be that the fracture movement on the near cortex is too small.

To increase the motion at the near cortex side a new kind of screws has been developed. In this study we examined the micromotion using normal locking head screws versus the new dynamic locking head screws.

Materials and Methods: A simplified fracture model was created by connecting 2 plastic cylinders (POM C, EModul: 3.1GPa) with a standard 11-holes Locking Compression Plate (Synthes). The fracturegap (between the two cylinders) amounted 3mm. Three kinds of fracture models were constructed: The model of a transverse fracture, an oblique fracture and a spiral fracture. An axial load from 0N up to 200N was applied with a testing machine (Zwick). The motion of the fracture model was measured in three dimensions using the optical measurement system PONTOS 5M (GOM, Braunschweig, Germany). The accuracy of the optical measurement system was about 5 micrometers.

Results: A total of 72 measurements were compared. Using the new screw, axial stiffness was decreased for 16% and micromotion was up to 200 μm higher in comparison to the old screw.

Discussion: Using the new dynamic locking head screw it’s possible to increase interfragmentary motion up to 200μm on the near cortex side (plate side).

Introduction: The extracorporeal shock wave therapy (ESWT) has a wide spectrum of indication in orthopaedics. However, infection in the application area is regarded as a contraindication. Therefore, in this study, the effect of of ESW on bacteria and their interaction with antibiotics is tested.

Methods: Standardized suspensions of S. aureus (ATCC25923) were exposed to different energy flux densities (EFD 0,38–0,96 mJ/mm²) and different impulse quantities (1000–12000 impulses) of a focussed ESWT. The surviving bacteria were quantified and compared to an untreated control group. The permeability of the cell wall of treated bacteria was analysed with a fluorescence assay and the DNA examined qualitatively for defects.

The influence of ESW on the effectiveness of antibiotics was examined using Gentamicin whose stability under influence of ESW was proven infrared-spectrometrically earlier.

S. aureus in specific broth (CAMHB) was treated with 4000 impulses at 0.59 mJ/mm². Then the MIC against Gentamicin was compared with the MIC of an untreated control group.

For the examination of synergistic effects between antibiotics and ESW, bacteria were treated with ESW (4000 impulses, 0.59 mJ/mm²) in a solution of CAMHB and varying Gentamicin concentrations (0.25 – 4 μ g/ml).

The vital bacteria were quantified and compared to the control group which was exposed to either ESW or Gentamicin. Bacterium colonies were quantified according to the guidelines of the NCCLS, the statistical evaluation was done with the Man-Whitney-U- test.

Results: The ESW showed a significant germicidal effect (P < 0.01) after application of either a high EFD (> 0.60 mJ/mm², 4000 impulses) or a high impulse quantitiy at low EFD (up to 12,000 impulses, < 0.60 mJ/mm²). The amount of CFU could be reduced by up to 99.9%.

Despite the germicidal effect of the ESWT neither a change of the bacterium cell permeability nor a damage to the DNA could be proved. Synergistic effects between Gentamicin and ESW were not found. No loss of effectivity of the Gentamicins at a simultaneous application of the ESW (P > 0.05) could be seen either.

Conclusion: The ESWT has a significant germicidal effect on bacteria after exceeding a certain threshold energy.

It could be shown that the applied total energy is responsible for the germicidal effect rather than single paramters as EFD and impulse quantity. A synergistic effect of antibiotics applied in addition to the ESW could not be proved. When ESW was carried out in presence of Gentamicin, the antibacterial effect of Gentamicin was influenced neither positively nore negatively.

The simultaneous application of ESW and systemically or locally applied antibiotics could represent a new therapy approach against tissue and bone infections. To prove this, further in-vivo studies are needed.

Introduction: Extracorporeal shock wave therapy (ESWT) covers a multitude of different indications in modern orthopedics, however, bacterial infections are still considered as contraindications. The goal of the present study was to determine the effect of ESWT on growth of clinically relevant bacteria in orthopedic and trauma surgery.

Methods: Standardised suspensions of a methicillin sensitive and a methicillin resistant strain of Staphylococcus aureus, and reference strains of Staphylococcus epidermidis, Pseudomonas aeruginosa and Enterococ-cus faecalis were subjected to 4000 impulses of high-energy shock waves with an energy flux density (EFD) of 0.96 mJ/mm2 and a frequency of 2 Hz. Furthermore, corresponding suspensions of S. aureus ATCC 25923 were exposed to different impulse rates of shock waves (1000 to 6000 impulses) and to different EFDs up to a maximum of 0.96 mJ/mm2 (2 Hz) to evaluate the influence of shock wave parameters. Subsequently, viable bacteria were quantified by culture and compared with an untreated control.

Results: A highly significant antibacterial effect of the ESWT was demonstrated for all bacterial strains with a reduction of growth to values between 1,1% and 29,7% (P < 0.01). Reference strains of S. aureus and S. epidermidis reacted most sensitive whereas E. faecium demonstrated highest resistance against high-energy shock waves. After applying different energy levels to S. aureus, a significant bactericidal effect was observed only with a minimum threshold EFD of 0.59 mJ/mm2 (P < 0.05). A threshold impulse rate of more than 1000 impulses could be defined to reduce bacterial growth of S. aureus (P < 0.05). Further elevation of energy and impulse rate exponentially increased bacterial killing.

Conclusions: ESWT proved to exert significant antibacterial effect in an energy-dependent manner. The results suggest that infections are not necessarily contraindications to shock wave therapy and could even represent a new indication for ESWT. However, clinical relevance should be assessed in vivo in an animal model.