what-when-how
In Depth Tutorials and Information
Postoperative Management
Immobilization after surgery should be as short as
possible to minimize disuse osteopenia. Spica casts are
best avoided unless there is gross instability of the oste-
otomy sites. Two long leg casts connected by a dowel (an
A-frame cast) are preferable to a spica cast because they
allow the patient to sit and help limit the tendency for
external rotation. Lightweight synthetic casts are pref-
erable to plaster. The duration of immobilization varies
among clinicians, ranging from 3 to 6 weeks. Following
immobilization, lightweight braces may be useful to get
the patient into an upright position.
friction between the sleeve and obturator components,
eventually causing the device to cease elongating. It is
doubtful that this problem can be eliminated entirely
given the design of the implant.
While most fractures that occur around an intra-
medullary nail are well tolerated, others result in bend-
ing of the device and must be revised either by cutting
the nail at the site of fracture or by “closed reduction”
to straighten the nail to facilitate removal. Cho et al.
99
found that fractures leading to bending of the implant
are most likely to be seen at the rod-tip regions where the
mechanical properties of the implant abruptly change.
These two areas include the tip of the obturator within
the sleeve component, and at the junction of the sleeve
and obturator.
Revision of extensible nails may be difficult because
the T-shaped ends may be buried beneath articular car-
tilage.
60,79
While some investigators have described
techniques to facilitate the exchange telescoping nails,
100
other clinicians have advocated single component revi-
sion to minimize disruption of the joint cartilage.
60,62
In summary, the selection of surgical techniques and
the choice of implant will depend on surgeon experi-
ence, severity of disease, remaining growth of the patient
and availability of specific instrumentation. Extensible
devices appear to be most advantageous for the femur.
Although using extensible nail devices in the femur carry
a higher complication rate than solid nails, they gener-
ally allow a prolonged period between operations of 3 to
4 years in several studies.
61,79,92
The device is especially
useful in children with considerable growth remaining.
The risks and benefits of these devices should be care-
fully discussed with the parents of children undergoing
these procedures.
The best implant for use in the tibia is less clear.
Several authors have commented that an extensible
device was more difficult to insert, had higher complica-
tion and revision rates, and was thus less suited for the
tibia.
64,83,84,92,101,102
Although a solid nail will need to be
revised sooner than an extensible device, revision sur-
gery is more easily accomplished in the tibia compared
to the femur. The subcutaneous location of the tibia facili-
tates the surgical exposure, and the use of a tourniquet
minimizes blood loss associated with revision surgery.
Future deformity correction in OI may utilize smart
intramedullary rods made of nitinol shape-memory
alloy. These nails can undergo a complex crystalline solid
phase change called martensite-astenite transformation.
The device can be bent and shaped at low temperature
(martensite phase), and when the metal is heated (asten-
ite phase) the original shape is restored. Firoozbakhsh
and coworkers
103
were able to create a bow in straight
rabbit tibia using this technology. They believe the same
principle could be applied to straighten a deformed
bone. The authors hypothesized this device could be
Complications
Reported complication and revision rates vary widely
in the literature. This is likely due to differences in how
complications are defined, variation in the phenotypic
make-up of the study group and disparities in the length
of follow-up among the different investigations. While
some complications may be avoided by sound surgi-
cal technique, many are the result of the poor quality of
bone in children with OI.
Complications with extensible nails include those
shared with solid nails, including non-union, infec-
tion, migration (both intra-cortical and extra-cortical),
extrusion into an adjacent joint or soft tissues, fracture
proximal or distal to a nail that has migrated, rotational
deformity, cortical atrophy and bending or breakage of
the implant. Because most extra-cortical rod migrations
have resulted from recurrence of anterior and anterolat-
eral deformity, a number of authors have recommended
that implants be placed in a central or slightly posterome-
dial location.
61,75,79,96,97
The problem of cortical atrophy
may be lessened by minimizing the number of osteoto-
mies and careful preservation and closure of the perio-
steum.
77,78
Stress shielding is also thought to play a role
in the appearance of cortical thinning.
98
A larger rod will
afford greater stability but causes more stress shielding.
A narrower rod will cause less stress shielding, but may
not provide sufficient stability. Until this dilemma is
resolved, it is probably best to err on the side of stability.
Other complications of extensible nails are inherent
to the design of the implant, such as loosening of the
T-piece in the Bailey-Dubow device. A common problem
with all telescoping devices is migration of one or both
of its components. Once the end of the nail migrates into
the metaphysis, it no longer functions as an extensible
nail, but instead behaves like a solid rod. Fortunately,
growth disturbance due to migration of a T-end across
the physis has been very rarely reported.
83
Sometimes
migration will occur after a period of uneventful elonga-
tion. Radiographs of these patients often reveal a subtle
bending of the implant which may lead to increased
