Avulsion fractures are the result of side-to-side (coronal) forces acting on the finger, putting the collateral ligament under sudden tension. The ligament is usually stronger than the bone, causing the ligament to avulse a fragment of bone at its insertion.
Avulsion fractures result in marked joint instability.
If the fracture is not displaced, nonoperative treatment is usually indicated (buddy taping to the adjacent finger). Displaced fractures, however, must be internally fixed.
Animation of the injury mechanism
Avulsion fractures result in marked joint instability. If the fracture is not displaced, nonoperative treatment is usually indicated (buddy taping to the adjacent finger). Displaced fractures, however, must be internally fixed.
Tension band principle
The tension band converts tensile forces into compression forces. The presence of comminution is a contraindication for tension-band treatment. In a case such as the illustrated fracture, the tension band will be applied in static mode. Tension band wiring of this fracture has been shown to be effective and usually provides good results. The advantage of this technique is its limited soft-tissue disruption. The risk of fragmentation is also minimized.
Reduction is achieved by pulling the finger laterally, in the direction opposite to the forces that created the fracture, and into MCP flexion, as necessary, to approximate the fragment. The avulsed fragment is pushed into place by the surgeon’s thumb.
With tiny fragments, indirect reduction can be achieved by tightening the tension-band wire at the end of the fixation procedure.
In displaced fractures, open reduction is often necessary. A small pointed reduction forceps is used gently to reduce the fracture from palmar to dorsal and from proximal to distal. Application of excessive force can result in fragmentation. Do not use a forceps in tiny fragments.
Note Anatomic reduction is important to prevent chronic instability, or posttraumatic arthritis.
Hold the reduction by inserting a K-wire through the center of the fracture surface. Check reduction using image intensification.
4. Wire fixation
Drill a hole
A hole is drilled in the proximal phalanx, from dorsal to palmar. The location of the drill hole should be the same distance from the fracture line as the avulsed fragment’s length. Use a drill guide, for soft-tissue protection, and either a slow-spinning 1.5 mm drill, or a 1 mm K-wire.
Thread a 26-28 gauge stainless steel monofilament 0.6 mm wire through the drill hole. A curved hemostat can be used to retrieve the wire from the palmar surface, sliding it very closely to the cortical bone in order to avoid damage to the digital nerve and artery. Periosteal elevators can be used for protection.
The wire must pass close to the bone and through the ligament in order to protect vascularity.
The wire is passed around the fragment and K-wire, and through the ligament attachment in a figure-of-eight mode. This can be achieved by passing a syringe needle of appropriate diameter on the surface of the bone, deep to the ligament attachment, and then inserting one end of the wire into the tip of the needle. The needle and the wire are then carefully drawn through, guiding the wire along the correct track.
Tighten the wire
Once the fragment is reduced, the wire is tightened, cut short, and bent along the phalanx, in order to avoid soft-tissue irritation. When tightening the wire, ensure that both ends are twisted into each other rather than twisting one end around the other straight end.
This is achieved by using traction with the pliers to tighten the loop and the twisting, still under tension, to take out the slack.
Anchoring the K-wire
Check position of the K-wires under image intensification. If the tip of the wire is in contact with the far cortex, then retract the K-wire by about 2 mm, bend it through 180 degrees, cut the wire to form a small hook, and impact the bent tip into the bone.
Use image intensification finally to ensure anatomical reduction.
5. Alternative fixations
Alternative: anchor screw
An alternative way of anchoring the figure-of-eight wire distally in the phalanx is the use of a screw instead of a drill hole.
In more vertical fractures, the K-wire gives the fragment additional stability and prevents secondary axial displacement.
If the avulsed fragment is too small to risk further damage by passing a K-wire, a simple figure-of-eight tension band is used.
Protect the digit with buddy strapping to the adjacent finger, to neutralize lateral forces on the finger.
See patient after 5 days and 10 days of surgery.
The patient can begin active motion (flexion and extension) immediately after surgery.
The implants may need to be removed in cases of soft-tissue irritation.
In case of joint stiffness, or tendon adhesion’s restricting finger movement, tenolysis, or arthrolysis become necessary. In these circumstances, take the opportunity to remove the implants.