what-when-how
In Depth Tutorials and Information
4.
Which rod for which bone?
In the lower extremities, femurs and tibias can
be rodded with either regular or telescopic rods
depending on the age of the patient, the size of the
bones and the preference of the surgeon. In the upper
extremities, the situation is different: the humeri can
be rodded with telescopic rods (much more difficult
than lower extremity rodding) or with regular rods
(either from the top down, or from the bottom up -
“Eiffel Tower” construct).
The same principles do not apply to the forearms:
the radius is naturally bowed and its anatomy
needs to be respected to avoid a loss in range of
motion (pronation/supination). Therefore, the
radius will be rodded from the distal epiphysis up,
while the ulna will be rodded from the olecranon
down. (It is better to avoid an entry point directly
on the tip of the olecranon as the rod is likely
to be felt under the skin by the patient, causing
discomfort and also causing a risk of limitation of
active extension with the top of the rod protruding
in the olecranon fossa).
During growth, the radial rod, fixed in the distal
radial epiphysis, will be pushed away while the
ulnar rod will remain more proximal: the two rods
slide away from each other. K wires or elastic rods
are the best implants for forearm surgery.
5.
Any role for locking plates?
The use of bisphosphonates in OI has raised
the incidence of non-union
13
particularly in the
subtrochanteric region of the femur.
As an attempt to cure pseudarthroses, Dr. Cho and
his team have been recently using locking plates
in association with IM rodding.
14
The effect of the
locking plate is to provide compression on the lateral
cortex of the femur to enhance bone healing. When
the bone has healed, removal of the plate is necessary
to avoid causing a stress riser.
6.
Stabilization of rotation
Most pediatric IM rods do not have a locking system
(like IM rods for adults) and rotation at the fracture
site or the osteotomy site is always a concern. Even
the recent modification of the Sheffield rod by Dr.
Cho
15
may prevent the migration of the rod, but does
not block the rotation.
Therefore, it is sometimes necessary to add an “anti-
rotation” device (either a small two-hole plate or a
“figure of eight” wire) to the rodding.
For adolescents and young adults with OI, a locking
nail is the implant of choice. It has the advantage
of stability and avoids the use of postoperative
immobilization, but the problem is the size of the
rod: the smallest diameter for such nails is 8.5 mm
which is often too big for OI bones.
A new nail (with an option for locking) filling the
gap between the pediatric implants and the adult
implants is just being released
16
but no clinical
studies have yet been published.
COMPLICATIONS OF LIMB
SURGERY IN OI
The following sections will describe complications
related to the choice of implant when treating children
with bowing and fractures secondary to OI (infection-
and anesthesia-related complications are not included).
Plates
The stress riser effect has already been mentioned.
Fractures above or below the plate are common. The
use of plates in long bones in OI patients should be
avoided. Occasionally, a plate can be added to an IM
rodding to control rotation or comminution in difficult
cases. However, once the bone is healed it is strongly
recommended to remove the plate to avoid issues with
stress risers.
Regular Rods (K Wire and Rush Rods)
Due to the fact that these rods have no capacity for
locking or anchorage, migration of the rod is frequent
(probably due to the mobility at the fracture/osteotomy
site) and often requires revision. Clinically, when the
rod migrates, it can be felt under the skin. This becomes
painful for the patient and reoperation is needed before
the rod breaks through the skin. Should a skin break
occur, there is a higher risk of infection.
Protrusion of the rod into a joint is more likely to
happen during surgery, and it must be recognized and
treated appropriately. Should the tip of a rod be left
protruding into a joint, this can cause articular cartilage
damage and ultimately osteoarthrosis.
Telescopic Rods
The most frustrating complications with the Dubow-
Bailey rods are the disengagement of the “T” part from
the female rod, usually at the greater trochanter level.
Not only is the femoral rod no longer attached to the
proximal femur jeopardizing the telescoping, but the
small metallic “T” part is very difficult to retrieve in
the soft tissues. To avoid this complication, Sharrard
17
designed a modification of the original rod called the
Sheffield rod where the “T” part is welded instead of
being screwed. This rod remains very popular in vari-
ous countries worldwide.
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