Review Question - QID 219878

Bicortical locking screws closest to the fracture will increase the stiffness of the fixation construct the most (Answer 4).

Bridge plate fixation can be utilized to treat a number of fracture types in orthopedic trauma, including femoral periprosthetic fractures, as in this case. Screw type and distribution can be utilized to modulate the strength and stiffness of a construct to induce optimal fracture healing. Absolute stability and rigid fixation are indicated in the fixation of fractures to obtain primary intramembranous fracture healing. Relative stability and flexible fixation are indicated when secondary endochondral healing is desired. Surgeons must be able to modulate the quality of the fracture fixation construct to achieve their goals. Decreasing the working distance (distance from the two closest screws to the fracture) and the use of locking screws will increase the stiffness of the construct. Far cortical locking screws are specially designed to reduce stiffness in an attempt to stimulate relative motion and secondary healing.

Bottlang et al. perform a biomechanical study on far cortical locking screws and bridge plates for the treatment of distal femur fractures. They conclude that far cortical locking significantly reduces the axial stiffness of a locked plating construct. This increase in construct flexibility only moderately decreases the overall strength of the construct.

Beltran et al. review the use of various techniques to modulate stress in fracture fixation constructs. They conclude that surgeons can manipulate multiple variables to modulate construct flexibility without sacrificing overall construct strength, including plate length, screw distribution, screw type, implant material, and the use of axially dynamic screw techniques (far cortical locking or near cortical over drilling).

Figure A is an AP radiograph of a Vancouver B1 femoral diaphyseal fracture about a well-fixed total hip arthroplasty, fixed with a locked bridge plate construct and cerclage wire.

Incorrect Answers:
Answer 1: Unicortical screws contribute less to stiffness than bicortical screws
Answer 2: Nonlocking screws contribute less to stiffness than locking screws
Answer 3: Far cortical locking screws contribute less to stiffness than normal locking screws, and are specifically designed to reduce overall construct stiffness through dynamic axial motion
Answer 5: Position C is farther from the fracture than Position B, and thus would contribute less to stiffness