Value of washers in internal fixation of femoral neck fractures with cancellous screws: a biomechanical evaluation uri icon

abstract

  • OBJECTIVE: The purpose of this study was to evaluate the maximum insertion torque of cancellous bone screws in osteoporotic proximal femurs with and without the use of washers. METHODS: Eight matched pairs of osteoporotic fresh-frozen human cadaveric femurs (age >70 years, all female) were used. Two screws were inserted in each femur either with or without a washer, and maximum insertion torque was measured using a 50 N.m torque transducer. The testing was performed using a customized device, which allowed the torque transducer to apply a constant axial force and rate of rotation to the screws. RESULTS: In 14 of 16 paired trials, the maximum screw insertion torque was higher when a washer was used. The average maximum torque with a washer was 5.1 N.m compared with 3.1 N.m without a washer (P < 0.01). CONCLUSIONS: The addition of washers increased the maximum insertion torque of cancellous screws in the proximal femur by 65% in this study. Washers prevent the screw heads from penetrating the lateral cortex at low insertion torque loads, and thereby provide for an improved purchase of the screws in the femoral head with a higher maximum insertion torque. We advocate for routine washer use and encourage future clinical studies to further understand the correlation between their use and improved outcomes in this patient population.

publication date

  • 2015