- screw should be placed in the central third of the femoral head between 5-12 mm from subchondral bone;
- consider short barrel dynamic hip screw side plate when screw < 80 mm or shorter is inserted to maximize sliding capacity;
- whether compression screw should be left in place is controversial, however, one should leave compression screw in place if short barrel plate is used, to prevetn disengagement of assembly;
- there is increase in failure rate if tip of nail is > 12 mm from femoral head subchondral articular surface.
- others argue that for best fixation, the nail should be advanced within 0.5 cm of the articular surface of the femoral head;
- Technical Considerations:
- w/ 135 deg plate, typically a 95 mm screw is required;
- determine correct length of lag screw w/ direct measuring gauge;
- this measurement allows for 5 mm of compression
- if more compression is desired, use a shorter screw;
- screw 5 mm shorter permits 10 mm of compression;
- if a shorter screw is used (for better compression) then compression screw must be left in place, so that scew barrel assembly does not become disengaged;
- if screw sliding brings threads in contact w/ plate barrel, additional impaction will not occur & device becomes biomechanical equivalent of a rigid nail-plate;
- use short-barrel dynamic hip screw sideplate when screw 80 mm or shorter is inserted to maximize available sliding capacity
Subchondral screw fixation for femoral neck fractures.
Prevention of unrecognized joint penetration during internal fixation of hip fractures: a geometric model based on Steinmetz Solid