1 Principles top
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Fracture type
Unicondylar fractures of the proximal phalanx can be transverse, short or
long oblique, or comminuted. Typically they are the results of a sports
injuries, caused by axial load combined with lateral angulation of the
finger.
Condylar fractures tend to be very unstable and should usually be treated
operatively. If conservative treatment is attempted, secondary displacement,
leading to angulation of the finger, often ocurrs.
Short and long oblique fractures
Short oblique fractures typically originate in the intercondylar
notch.
Long oblique fractures more often originate through one of the condyles,
splitting proximally towards the diaphyseal cortex on the side of the uninjured
condyle.
Caveat
These fractures are rare, but difficult to treat. There is an increased risk of joint stiffness resulting from these fractures.
It is wise to use magnifying loupes in these procedures. Gentle and precise handling throughout the procedure is mandatory.
2 Reduction top
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Anatomical reduction mandatory
Articular fractures must be reduced anatomically. Otherwise, the articular
cartilage may be damaged, leading to painful degenerative joint disease and
digital deformity.
This illustration shows how even slight unicondylar depression may lead to
angulation of the finger.
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Visualization of the fracture
In order to gain better a better view of the fracture, use a syringe to
irrigate out blood clot with a jet of Ringer lactate.
Gently explore the fracture site to assess its geometry, using a dental pick.
The pick can also be used carefully to reduce small fragments. Take great care
to avoid comminution of any fragment.
It is important to maintain the vascularity of tiny fragments attached to the
collateral ligament, in order to avoid osteonecrosis.
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Indirect reduction
Reduction starts with traction in order to restore length.
Lateral pressure, exerted by the surgeon’s thumb and index finger, will then
reduce the fracture.
Confirm reduction using image intensification.
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Direct reduction of large fragments
A small pointed reduction forceps can be used for larger fragments gently to
rock the fracture from side to side. Be careful not to apply excessive force as
this can lead to fragmentation.
Confirm reduction using image intensification.
Note
Anatomical reduction is important to prevent chronic instability or
posttraumatic degenerative joint disease.
3 Decision making top
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Decision making
Different types of treatment are available for the various fracture types.
Short oblique fractures
Fixation with one lag screw, or a percutaneous K-wire, is recommended.
Long oblique fractures
Fixation with 2 or 3 lag screws is recommended. One or more K-wires is
another option, although concerns about instability exist.
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Planning screw placement
Large fragments
In large fragments, all screws can be placed safely proximal to the
collateral ligament.
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Pitfall: Beware of fissure lines
Make sure that the screws are not placed through incomplete fissure
fractures.
This is one of the reasons why magnification is important.
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Small fragments
If only one screw can be inserted into a small fragment, it will have to be
placed within the joint cavity, but through the nonarticular face of the
condyle, distal to the collateral ligament.
The lateral aspect of the phalangeal head, which is safe for screw placement,
can be approached by flexing the PIP joint.
4 Small fragment fixation top
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Screw size
Screw length needs to be adequate for the screw just to penetrate the
opposite cortex.
Keep in mind that at the apex of the fragment, the minimal distance between the
screw head and the fracture line must be at least equal to the diameter of the
screw head. If necessary, a screw of smaller diameter will have to be
chosen.
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Prepare for drilling
There are two ways to approach the outer surface of the phalangeal head: either by flexing the PIP joint, or with an extended joint, by making a short incision in between the collateral ligament and the accessory collateral ligament.
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Drilling
Drill a gliding hole for a 1.0 mm screw, as perpendicularly to the fracture
plane as possible, using a 1.0 mm drill bit.
Use a 0.8 mm drill bit to drill a thread hole in the opposite fragment, just
through the far (trans) cortex.
Note
Be careful to select appropriately-sized instruments. The use of too large
drill bits or screws may result in fragmentation.
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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.
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Insert lag screw
Insert the lag screw and gently tighten it to compress the fracture.
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Pitfall: protruding screw head
A protruding screw head can cause ligament irritation and eventual joint
stiffness.
In order to avoid such protrusion, slightly enlarge the entrance to the screw
hole in order partially to sink the screw head. Do not attempt to countersink
with too large a tool, and be careful not to overtighten the screw, to avoid
fragmentation.
5 Large fragment fixation top
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Preliminary fixation (large fragments)
Long oblique fractures can be preliminarily fixed by inserting a K-wire. Be careful to place it in such a way that it will not conflict with later screw placement.
Avoid inserting a K-wire into small fragments, as they are in danger of fragmentation.
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Drilling and alternative preliminary fixation
Leaving the reduction forceps in place, drill a gliding hole as
perpendicularly to the fracture plane as possible, using a 1.5 (or 1.3) mm
drill bit for a 1.5 (or 1.3) mm screw. Insert a 1.5 (or 1.3) mm drill sleeve
into the gliding hole.
Use a 1.3 (or 1.0) mm drill bit to drill a thread hole in the opposite
fragment, just through the far (trans) cortex.
Leave the drill bit in the drill hole, preliminarily to hold the reduction if
no K-wire has already been used for this purpose.
Remove the reduction forceps.
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Screw size selection
The exact size of the diameter of the screw used will be determined by the
fragment size and the fracture configuration.
The various gliding hole and thread hole drill sizes for different screws are
illustrated here.
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Pitfall: Oblique measuring
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.
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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.
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Lag screw insertion
Countersinking in diaphyseal bone
There are two important reasons for countersinking:
- The risk of soft-tissue irritation is greatly reduced by ensuring that the the screw head protrudes only minimally from the bone surface.
- 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.
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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.
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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.
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Preliminary fixation with drill bit
The drill bit can be left in the drill hole for preliminary fixation. This saves space, as no K-wire is needed.
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Drill for proximal screw
Towards the proximal apex of the fracture line, drill a gliding hole for a
second lag screw. This screw, too, should be placed as perpendicularly to the
fracture plane as possible, using a 1.5 (or 1.3) mm drill bit for a 1.5 (or
1.3) mm screw. Insert a 1.5 (or 1.3) mm drill sleeve into the gliding
hole.
Use a 1.0 (or 0.8) mm drill bit to drill a thread hole in the opposite
fragment, just through the far (trans) cortex.
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Insert distal screw
Insert the distal lag screw. Do not completely tighten it at this time. The screw should penetrate the opposite cortex.
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Insert proximal lag screw
Now insert the proximal lag screw. This screw, too, should penetrate the
opposite cortex.
Alternate tightening of the two lag screws helps to avoid tilting of the
fragment and applies even compression forces over the whole fracture
surface.
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Check using image intensification. The reduction must be anatomical.
Check stability of the fixation by passive flexion and extension of the PIP joint, and by applying gentle lateral and rotational motion. This will help to determine stability in order to establish strategies for rehabilitation.
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Caveat: Changing fracture plane
Hastings and Weiss described a fracture type in which the fracture plane
changes between the condylar and metaphyseal zones.
In such a fracture configuration, it is important to observe that all the lag
screws are inserted as perpendicularly to the local fracture plane as
possible.
Be careful to confirm correct fracture planes under direct vision and in
different radiographic views.
