1 Indications topenlarge
These common fractures often heal without surgery, but if significantly displaced, they can be fixed with lag screws.
A minimum of two screws should be used. This requires that the fracture zone be at least twice as long as the diameter of the metatarsal. If the fracture is shorter, a single lag screw should be used with a protection plate.
2 Principles topenlarge
Proper alignment of the metatarsal heads is a critical goal in restoring the pathomechanics of the forefoot. On the AP view, a normal curved “cascade” (Lelièvre’s parabola) appearance, symmetric with the other foot, is mandatory. See illustration.
This ensures that the normal length of the metatarsal is restored.
It is also critical to restore the metatarsals in their axial or horizontal plane so that in the axial or tread view all the metatarsal heads are on the same level.
Any malalignment particularly flexion will recreate focally high pressure during the stance phase and toe-off and will result in pain and subsequent callus formation.
Note that for the first ray, it is the sesamoids rather than the first metatarsal head, that bear weight, and therefore one must look at the sesamoid level in establishing the alignment in the axial or horizontal plane of the first metatarsal.
3 Approach and reduction topenlarge
Long oblique diaphyseal fractures of the fifth metatarsal can best be approached through a lateral incision (see Lateral approach to MT5).
Visualization of the fracture
To determine the exact geometry of the fracture and correct placement of the screws, it may be helpful to open the fracture plane by exerting traction and rotation on the toe.
The fracture may be cleared of interposed soft tissues; if necessary, the fracture site can be irrigated for better visualization.
Reduction by traction
An assistant applies manual traction while the surgeon reduces the fracture with a periosteal elevator, or a dental pick.
Hold the reduction with one, or two, pointed reduction forceps, applied so as not to conflict with the planned screw positions.
It is essential to confirm that the apex of each fracture fragment has been properly reduced. This should produce proper rotational alignment, which can be confirmed by inspection of the toe.
4 Planning screw position topenlarge
If the fracture is long enough, 3 lag screws may be used. Each should be inserted perpendicularly to the fracture plane, and spaced evenly along the fracture.
The screws thus are distibuted in a helical pattern.
Three screws are more stable
But if the fracture is not long enough, two may be used with a protection plate if desired.
Pitfall: Beware of fissure lines
Undisplaced additional small fracture lines may be present but not apparent on x-rays. Look carefully for these when placing screws. Do not insert a screw through such a fissure, as it will often displace with loss of fixation.
Pitfall: Screw too close to fracture
Do not insert screws too close to the fracture. The screw should be at least the diameter of its head away from the fracture, and should bisect the width of the fragment.