what-when-how
In Depth Tutorials and Information
Other complications seen with various telescopic rods
(Dubow-Bailey (DB), Fassier-Duval (FD), Sheffield)
include:
19-23
Disengagement of the Female and Male
Components
After several years of growth, the two components
of a telescopic rod will reach the maximum elonga-
tion, after which, with continued growth, the two parts
of the rod will disengage and migrate away from each
other, leaving a part of the shaft (diaphysis) unpro-
tected. This situation, for some surgeons, is an indica-
tion to replace the rod with a longer one. But as most
patients are now receiving bisphosphonates and have
stronger bones, it may be an unnecessary surgery for an
asymptomatic patient. On the other hand, if a fracture
occurs between the two nail parts, it becomes neces-
sary to replace the nail more urgently since the patient
is in pain. There is no “good” option and the situation
must be clearly explained to the child/family, express-
ing the two alternatives: change the rod automatically
when maximum elongation is observed, or wait until
the bone bows or breaks in the unprotected area.
1.
Telescoping problems (non-telescoping)
2.
Rod migration (proximal or distal)
3.
Bowing or breakage
4.
Disengagement of the female and male components
5.
Growth disturbance
Telescoping Problems (Non-Telescoping)
Like a radio antenna, the telescopic rod can no lon-
ger expand if it is bent. It is therefore important to insert
such a rod very smoothly in the bone, without forcing.
If after a fracture only the male component is bent, the
rod should continue to telescope with growth. But if
the female rod is bent, telescoping is no longer possi-
ble. The decision for rod revision in such circumstances
depends on the age of the patient (how much growth is
expected) as well as the degree of bowing in the bone.
Growth Disturbance
Inserting a rod in a growing bone and passing
through the growth plate carries a theoretical risk of
growth disturbance, but as long as the rod is perpen-
dicular to the physis and passed only once (avoid mul-
tiple attempts), this complication is extremely rare. When
a rod no longer telescopes, the tip of the male rod will
travel through the growth plate while the bone continues
to grow. This has never been an issue in clinical practice.
Limb length inequality is often seen in OI and most
often is due to multiple fractures with shortening or dif-
ferential bowing from one leg to the other. Limb length
inequalities should be treated in a similar fashion to
other children with this problem. However, the treat-
ing surgeon should take into account that OI children
may not grow as fast or as much as other children and
therefore growth modulation may need to be done at an
earlier chronologic age.
Rod Migration (Proximal or Distal)
In the femur, proximal migration can happen peri-
odically and typically the rod backs up into the but-
tock. This causes discomfort/pain to the patient in
flexion/extension of the hip (sitting/standing) and
can also cause difficulty with abduction. Rod revision
is usually necessary to push the rod back down to the
greater trochanter. The reasons for migration are mul-
tiple; in part the non-ossified greater trochanter is
made of cartilage which is soft and the large abductor
muscles attach to the greater trochanter causing micro-
movements which over time decrease the anchorage of
the nail.
Distally the male rod is fixed into the epiphysis (with
both the DB and the FD rod). If the pull-out strength of
the male rod is greater than the fixation in the epiphy-
sis, the bone will grow and the rod will be left behind.
This is called “apparent” proximal migration of the
male rod. Revision surgery is not always necessary as
the non-telescopic rod behaves like a regular rod and
would only need to be addressed if bowing or fractures
occur below the male component.
CONCLUSION
In summary, the consensus on the choice of implant
and material for long bones in OI is controversial. Most
agree that rodding is far superior to any plating tech-
niques. However, the material of the rods and the type
of rods used continue to be a source of debate. Centers
that have access to telescoping rods prefer this method,
despite the need for specialized training and experience
with the technique, as well as the elevated cost of the
implant. Regardless of the implant chosen, the orthope-
dic surgeon needs to understand and respect the prin-
ciples of rodding in brittle bones to avoid devastating
complications.
Bowing or Breakage
Bowing of the rod is in most cases due to trauma.
The bone breaks and the rods are bent. Depending on
the angulation (amount and location) it may be neces-
sary to perform revision surgery. As non-union post-
osteotomies are more frequently observed in OI bones,
failure of the IM rod at the level of a non-union can be
observed. Over time, the rod fatigues due to the micro-
motion and the rod can then break. Smaller diameter
rods are more at risk.
