Executive Editor: Chris Colton

Authors: Renato Fricker, Matej Kastelec, Fiesky Nuñez, Terry Axelrod

Thumb - Proximal phalanx: Metaphyseal (head), oblique

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Glossary

1 Principles top

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Indications

Fractures of the distal metaphysis can be transverse, oblique, or comminuted.
Always confirm the fracture configuration with views in both planes.
Irreducible and unstable fractures require ORIF.
Other indications for ORIF are open fractures, or soft-tissue lacerations.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Lag screw with protection plate

In short oblique fractures, only one lag screw can be inserted. This is insufficient to produce enough stability. The lag screw must be protected by a plate.
For fractures of the condylar metaphysis, a minicondylar plate is preferred, because of the angular stability that it provides, although any conventional plate can also be used for protection: these have the advantage of being less bulky. This reduces the risk of compromising the gliding of the extensor tendons.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Reduction principles

Indirect reduction is achieved by traction and manipulation.
Sometimes indirect reduction may be prevented by interposition of the lateral band.
If the fracture is irreducible, ORIF is indicated.

2 Reduction top

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Indirect reduction by traction

Reduction can be achieved by traction and flexion exerted by the surgeon,...


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

... or by two pointed reduction forceps.
Confirm reduction using image intensification.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Direct reduction

Direct reduction is necessary when the fracture can not be reduced by traction and flexion, or is unstable.
When indirect reduction is not possible, this is usually due to interposition of parts of the extensor apparatus.
Use a pointed reduction forceps for direct reduction.

3 Lag screw insertion top

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Planning lag screw position

The lag screw should be inserted as perpendicularly to the fracture line as possible and from the dorsal surface. The direction of the obliquity of the fracture plane dictates the exact position of the lag screw.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Drilling for lag screws

There are two options to prepare the gliding hole and the threaded hole:

1) Gliding hole first
Drill the gliding hole in the near cortex. Ensure perfect fracture reduction and then insert a drill guide. Drill the threaded hole in the far (trans) cortex through the drill guide.
This method ensures that the threaded hole is perfectly in line with the gliding hole.
This is the preferred method


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

2) Thread hole first
Drill a hole through both cortices, using the drill for the thread hole. Then use the corresponding larger drill bit to overdrill the near cortex to create the gliding hole.
This technique is useful for small fragments. The disadvantage, however, is that the holes may not be centered in relation to each other.

Pearl
If the near cortex is tapped prior to overdrilling for the gliding hole, eccentric passage of the second drill is less likely. This can be achieved by inserting the chosen self-tapping screw through the near (cis) cortex and then removing it. The drill will now follow exactly the threaded axis.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Pitfall: Oblique measurement

When measuring for screw length in oblique drill holes, the measurement to the acute angle is different from the measurement to the obtuse angle. This problem increases with the degree of obliquity.
Always measure both angles and use the longer measurement. However, keep in mind that too long a screw can protrude to the extent that it puts the soft tissues at risk.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Screw length pitfalls

Ensure that a screw of the correct length is used.

  • Too short screws do not have enough threads to engage the cortex properly. This problem increases when self-tapping screws are used due to the geometry of their tip.
  • Too long screws endanger the soft tissues, especially tendons and neurovascular structures. With self-tapping screws, the cutting flutes are especially dangerous, and great care has to be taken that the flutes do not protrude beyond the cortical surface.

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Countersinking in diaphyseal bone

There are two important reasons for countersinking:

  1. The risk of soft-tissue irritation is greatly reduced by ensuring that the the screw head protrudes only minimally from the bone surface.
  2. Countersinking ensures that the screw head has a maximal contact area with the bone, distributing the forces from the screw head more widely and more biodynamically than an unsunk head.

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Pitfall: breaking the cortex in diaphyseal bone

Do not advance the countersink too deeply into the cortex: the cortical thickness will determine the depth of countersinking. Excess penetration risks break-through of the screw head when tightened and loss of fixation. Countersinking is, therefore, done by hand and not with a power tool.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

No countersinking in the metaphysis

Do not countersink the screws in the metaphysis as its cortex is very thin.
If countersinking is attempted, all purchase and compression may be lost due to screw-head breakthrough.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Insert lag screw

Insert the lag screw and tighten it to compress the fracture. The pointed reduction forceps can now be removed.

4 Plate preparation top

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Planning plate position

It is wise to use magnifying loupes for this step.
Plan the blade position as dorsal as possible, in order not to injure the collateral ligament.
Make sure that the plate will be perfectly aligned with the long axis of the proximal phalanx in the lateral view.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Corresponding flare

The position of the plate should be distal enough to ensure that the metaphyseal flare fits to the shape of the shoulder of the plate.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

The minicondylar blade plates are available in two forms. One fits on the ulnar aspect of the bone, and the other on the radial aspect. It is a common mistake to choose the wrong one. The correct implant will have the blade dorsal and the distal screw hole palmar.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Trim the plate

Adapt the plate length to fit the length of the proximal phalanx. Avoid sharp edges which may be injurious to the tendons. There should be at least 3 plate holes distal to the fracture available for fixation in the diaphysis. At least two screws need to be inserted into the diaphysis.

Prepare the blade
Measure the length of the drill hole.
Cut the blade to the determined length, so that it just fills the drill hole.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Pearl: Cut the blade transversely

If you cut the blade on the flat, it will compress and widen very slightly as it is cut. This makes its maximal width very slightly larger than 1.5 mm. It may not fit in the 1.5 mm hole that you have drilled.
Therefore, cut the blade on edge (to deform it through its narrower dimension) to the correct length. The resultant tip is somewhat arrow-shaped.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Pitfall: avoid dangerous edge

If you are using a dedicated minicondylar plate cutter which trims the plate by a shearing action, be very careful not to create a sharp dorsal edge that will endanger the extensor apparatus. Correct cutting will produce the sharp edge on the bone side of the plate.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Pitfall: Protrusion of the blade

Avoid protrusion of the blade through the opposite cortex, as friction during movement and eventual ligament injury may result.
Due to the fact that the phalanx is wider on the palmar side that on the dorsal side, an AP or PA x-ray view may suggest that the blade is fully contained within the bone, whereas in transverse section, it actually protrudes.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Contouring of the plate

Twist and bend the plate to follow exactly the shape of the phalangeal diaphysis.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

As the minicondylar plate has notches (like a reconstruction plate), it can also be curved on the flat to fit the curve of the phalanx.

Note
It is worth investing time in the precise contouring of the plate to the phalanx. Any imperfection in contouring will result in fracture displacement when the diaphyseal screws are tightened.

5 Drilling top

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Determine location of drill hole

In order to determine the position of the first drill hole (for the blade), it can be very helpful to turn the plate over and use it as a template.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Direct reduction

Drill a 1.5 mm transverse hole through the condylar metaphysis of the proximal phalanx adjacent to the subchondral bone, to create a track for the blade.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

This drill hole needs to be sufficiently dorsal to leave enough space for the plate’s most distal hole, adjacent to the blade.

6 Plate application top

Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Apply plate

Introduce the blade into the drill hole. Gently push with the thumb until the plate is fully seated.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Align the plate with the diaphysis

Before inserting distal screw adjacent to the blade, ensure that the plate is in line with the phalangeal diaphysis in the lateral view by rotating it around the long axis of the blade.

Insert distal screw
The distal screw, adjacent to the blade, is then inserted in a neutral position.
The screw should just engage the far cortex.

Note
Be careful to avoid screw protrusion, as ligament injury may result from friction during movement.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Drill neutral proximal hole

Use a 1.1 mm drill bit to prepare a neutral thread hole for the first screw at the proximal end of the plate.
To improve stability, drill this hole at a slightly divergent angle.


Short oblique head fracture of the proximal phalanx – Lag screw with protection plate enlarge

Insert remaining screws

Insert the proximal screw and tighten it.
Prepare for a second diaphyseal screw in a similar way to the first, and insert it.

v1.0 2008-11-08