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.
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. Patient preparation and approach
This procedure is normally performed with the patient in a supine position.
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.
5. Planning screw position
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.
Insert lag screws
When inserting two screws as shown, tighten them alternately to bring the fracture surfaces together without displacement.
A sterile dressing is applied and the patient is immobilized in a boot or in a below-knee cast. If the state of the soft tissues is precarious, a padded bandage should be applied initially, and the limb should be maintained elevated until the swelling has subsided and healing of the soft tissues without further problems can be anticipated. The foot is then immobilized either in a boot or in a below-knee cast. The advantage of the boot is that it can be easily removed for inspection of the wound and for regular exercises and mobilization of the joints.
Weight bearing is delayed until such time as the wound is healed. The sutures are removed 2 weeks postoperatively and graduated weight bearing is started. The degree of loading of the extremity is determined by the severity of the injury and the stability of the fixation achieved. Early loading is important but not at the expense of loss of fixation. Intermittent elevation of the foot and extremity should be continued until such time as the swelling has subsided.
For percutaneous K-wire fixation
Weight bearing in a heel-wedge shoe is permitted. The K-wires are removed in the clinic at six weeks, at which point a flat postoperative or hard-sole shoe is permitted as tolerated.
X-rays are taken at 6 weeks postoperatively to assess union and the integrity of the fixation. The resumption of the use of normal footwear is guided by the clinical signs and x-ray evidence of union.