Finite element analysis of sliding vs static configuration of partial threaded cannulated compression screws for Pauwels type III fracture neck of femur.

BACKGROUND

Cannulated Cancellous Screws fixation is done either as a sliding or static configuration according to the number, thread length and orientation of the screws. This study aims to compare the biomechanical properties of 3-CCS as sliding configuration and BDSF & 4-CCS (Alpha configuration) as static configuration, by finite element analysis for Pauwels type III fracture neck of femur.

METHODS

DICOM format images of saw-bone were used to build the 3-D geometric models, which were hypermeshed to create models of Pauwels type III FNF with an angle of 65°. CAD models of three configurations were created as per AO specifications and analysed for stress distribution of bone & implant, relative displacement between fracture planes & stiffness.

RESULTS

The peak stress at the fracture surface was found to be low in 4-CCS, which promotes fracture healing. 4-CCS had a decreased chance of failure due to lower implant stress and fracture surface displacement, indicating improved length stability. Overall, 4-CCS had the maximum construct stiffness, indicating a stable and rigid fixation.

CONCLUSION

The static configuration of 4-CCS showed superior biomechanical properties in terms of low stress of bone & implant, and lower relative displacement of the fracture surface with high construct stiffness over other configurations. So, 4-CCS (Alpha configuration) should be the preferred configuration for the Pauwels type III FNF.