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There are a variety of devices available to accomplish
the controlled distraction of the bone. Basically, they
fall into two categories: external fixators which attach
to the bone from outside of the body with a series of
rings, pins and wires and internal devices that are implanted
inside the body and lie on the bone or in the marrow cavity
of the bone. Additionally, other approaches that do not
utilize the distraction concept may be most appropriate
for specific cases. Sometimes a combination of external
and internal fixators, such as “Lengthening over
Nail” is used.
External
Fixators
External fixators are the most widely known and versatile
devices used to accomplish limb lengthening. There are
several types of external fixators. The simplest is
the monolateral. The more complex, yet more versatile
devices are circular fixators such as the Ilizarov and
Taylor Spatial Frame. Both consist of an external frame
attached to the limb that is to be straightened and
/ or lengthened.
The Ilizarov frame, named after its inventor, Russian
physician Gavrill A. Ilizarov, is a circular scaffolding
that surrounds the limb. The rings of the frame are
attached to the bone with wires or screws. The rings
are connected to each another by bars that contain a
nut or screw which is manually turned to gradually increase
the distance between the cut ends of the bone. The Taylor
frame is an improvement on the Ilizarov device, utilizing
computer software to establish a precise schedule of
adjustments to be made to the frame by the patient/family.
The primary risk in the use of an external fixator
is infection. For this reason, pin sites, the area where
the pin meets the skin, must be carefully kept clean
to prevent infection that could spread to the bone.
Other risks are nerve or vascular injury, pin loosening,
scarring of pin sites, bending and breaking of the lengthened
bone, stiffness of adjacent joints and the social and
psychological stress of wearing a somewhat cumbersome
external fixator.
New refinements in technology designed to decrease fixator
time and maintain joint mobility have produced a variety
of techniques and devices as noted below.
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This is a 15 year old boy who sustained a severe
injury to the growth plate of the femur, around
the knee, 10 years ago. Over time, he had multiple
surgeries in another country. He presented with
a 18 cm shortening with bowing of the left leg that
was fused at the knee. He underwent gradual lengthening
and realignment of the femur and tibia, with near
equalization of leg lengths. Clinical appearance
and x rays of the patient before and after gradual
realignment and lengthening are seen. |
Lengthening Over Nail
(LON)
Used in combination with an external fixator, this technique
allows better alignment and shortens the time in an
external fixator. A metal rod is inserted into the marrow
cavity of the center of the bone, and the external fixator
is applied around the peripheral part of the bone. As
the limb is lengthened, one end of the bone slides over
the rod and the new bone is grown around it. After the
bone is lengthened, the patient goes back to the operating
room for the insertion of special screws that lock the
rod to the bone. The screws are positioned at both ends
of the rod on opposite sides of the lengthening zone,
thus eliminating the further need for the external fixator.
The fixator is removed during the same operation and
at the end of the consolidation phase; the metal rod
is surgically removed. This process shortens the total
external fixator treatment time to less than half. Lengthening
Over Nails is not appropriate for all patients, particularly
those whose problem is linked to an infection or in
young children. The technique is more suitable for the
leg bones such as the tibia and femur.
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A 16 year old boy sustained a compound fracture
of the left tibia with 6 cm of bone loss (A).
He was hit by car while riding a bicycle. Once the
wound was cleaned, the skin was closed and the fracture
stabilized with an intramedullary nail (B).
After a few days, an external fixator was applied,
and a bone transport over the nail was carried out
(C). Healing occurred without any
further intervention (D) and he
returned to unrestricted activities including sports. |
Some other treatments
do not require an external fixator:
Fully Implantable Lengthening
Nails and Prostheses
The most recent treatment innovation
is the use of fully implantable devices that can lengthen
the limb from within without the need for an external
fixator. Among other advantages, this approach eliminates
the risk of pin infection and muscle tethering by the
pins, and offers less pain and more comfort. However,
it is not appropriate for many patients. Also, some
of these devices may be more prone to technical problems.
Other Ways
of Equalizing Limb Lengths
Epiphysiodesis and Growth
Plate Stapling
This operation, done only in children
with sufficient growth remaining, can stop the growth
in the longer leg until leg length equalization is achieved.
Precise timing for performing this procedure is critical
to achieving a successful outcome. Compared to limb
lengthening, patients require less postoperative rehabilitation.
If staples across the growth plates are used, they may
need to be removed at a later date.
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A 12 year old who had sustained injury to the left
lower leg 2 years ago, presented with the left leg
3 cm longer than the right. Given the mild discrepancy
and growth remaining, he underwent stapling of the
growth plate at the lower end of the left femur. |
Acute Bone Shortening
Reconstruction
It is possible for a piece of bone to
be removed from a longer leg. This is typically done
in adult femur bones. While this option can be good
choice for certain patients, it does not always provide
a comprehensive solution for short, crooked limbs.
Amputation and Prosthetics
Treatment options for extreme limb length
discrepancies include Prosthetic Reconstruction Surgery
(PRS) designed to modify or amputate the limb so that
it can be more easily fitted into a prosthesis. If this
is done, the prosthesis can be lengthened to equalize
the LLD as the child grows. Operations of this type
such as Syme amputation and Van Ness rotationplasty
are usually only considered for the most severely deficient
cases in which one or more joints are missing.
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A 3 month old girl was seen with severe congenital
shortening related to several missing bones in the
right lower leg and foot. Given the severity of
deformity and the lack of a functional foot, she
underwent an amputation with prosthetic reconstruction
of the lower leg at age 9 months. Within a few days
following surgery, she started walking on her “new”
leg. |
Percutaneous
Osteotomy Techniques
(Minimally Invasive Methods
to Straighten Crooked Bones)
Minimally invasive techniques to cut bone (osteotomy)
are increasingly being performed in children and adults.
Through small skin incisions, the underlying bone is
cut under x-ray control with techniques that tend to
preserve the overlying covering of the bone (periosteum).
These gentler yet precise methods to cut the bone can
also be utilized to remove and replace plates and nails
from prior surgery which have proven ineffective, or
to cut bone for external fixation. Compared to traditional
open procedures requiring large incisions, these percutaneous
techniques may carry far less risk of infection, blood
loss and damage to the soft tissues and yet promote
faster healing due to preservation of the biologically
active periosteum.
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A 24 year old right hand dominant man sustained
a compound fracture of his right forearm as a teenager.
He developed a deep infection in the bone that required
multiple surgeries including removal of part of
the infected bone. He presented to us with a severe
deformity of the right wrist with x rays demonstrating
bone loss and a persistent non-union of the fracture.
A staged reconstruction with bone transport was
performed. He returned to work full time as a construction
worker. |
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The
Techniques
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