A retrospective review identified nine patients who had been treated
with isolated femoral lengthening over a humeral nail at St. Louis
Shriners Hospital for Children between January 1, 1996, and September
30, 1997. All patients were available for follow-up at a minimum
of two years postoperatively, and all were included in this study.
Charts were reviewed for demographic information, diagnoses, and
complications. At the time of final follow-up, the range of motion
of the hip and knee were determined and radiographs, including a
preoperative and final scanogram, were reviewed to assess limb length. A
final standing anteroposterior radiograph of both lower extremities
was examined for evidence of avascular necrosis of the femoral head
and to measure limb alignment, including deviation of the mechanical
axis and the lateral distal femoral angle
15-17
. We also evaluated the hip preoperatively and on the final postoperative
standing anteroposterior radiograph of the lower extremities, measuring
the articulotrochanteric distance, femoral neck diameter, and neck-shaft
angle
18
.
Indications for surgery included a limb-length discrepancy that
was projected to be >6 cm at skeletal maturity with use of the Moseley
technique
19
, that was primarily located in the femur, and that caused functional
problems with gait. Severe ipsilateral hip dysplasia with an acetabular
index of >20° or with subluxation was an absolute contraindication
to this procedure. Knee instability with >10 mm of laxity on the
Lachman test was a relative contraindication to this procedure because
of the difficulty inherent with monolateral external fixation devices
crossing the knee to stabilize the joint. Patients with severe knee
instability were treated with a circular external fixator that crossed the
knee to prevent posterior subluxation during lengthening and were
not included in the present study. The diagnoses in our series included
a congenital short femur in eight patients
20
and neonatal sepsis with multifocal osteomyelitis leading to limb-length
discrepancy in one patient.
All of the femora were lengthened over a humeral intramedullary
nail (Smith and Nephew Richards, Memphis, Tennessee) inserted in
an antegrade fashion through the lateral aspect of the greater trochanter.
The osteotomy site was distracted with an Orthofix monolateral lengthener
(Orthofix S.R.L. Limb Reconstruction System; Bussolengo, Verona,
Italy).
Operative Technique
Preoperative radiographs were reviewed, and the diameter of the
femoral canal at the isthmus and the length of the femur from the
trochanter to the distal femoral physis were measured, with magnification
taken into account. The nail diameter was planned to be equal to
the isthmic femoral diameter, and an appropriate selection of humeral
nails was made available preoperatively. The patient was placed
supine on a radiolucent operating table (Orthopaedic Systems, Union
City, California). A 4-cm longitudinal incision was made over the greater
trochanter, and blunt and sharp dissection was carried out down
to the lateral aspect of the greater trochanter. An awl was used
to enter the lateral portion of the greater trochanter (
Fig. 1
). A guide-wire was then passed into the femoral canal, and the
canal was reamed to a diameter 1.5 mm greater than its measured
diameter. Attention was then turned to the lateral aspect of the
distal part of the femur, with three 5-mm titanium half-pins placed
into the femur perpendicular to its long axis (
Figs. 2-A
,
2-B
, and
2-C
). If derotation was planned at the time of the lengthening, the pins
were placed at an appropriate angle to guide derotation following
the osteotomy. The most distal half-pin was placed approximately
1 cm proximal to the distal femoral physis. A nail of appropriate
length was chosen to extend to the level of the most proximal of
the distal half-pins (
Fig. 2-B
). The nail was then inserted through the lateral trochanteric entry
site, and the insertion jig was left in place proximally. Three
proximal 5-mm half-pins were then placed parallel to one another
through the guide, perpendicular to the nail, with spacing determined
by the constraints of the fixator. The most proximal pin should
be placed at the level of the superior edge of the lesser trochanter.
These pins are inserted either anterior or posterior to the humeral
nail (most commonly anterior, as determined by a lateral image of
the proximal part of the femur with the rod in place). Care is taken
to ensure bicortical purchase of the half-pins to avoid weak unicortical
purchase. Although ideally the pins should not come into contact
with the nail, the half-pins nearly always abutted the nail because of
the small diameter of the femur. The nail was then removed, and
a 5-cm lateral incision was made, centered approximately 1 cm distal
to the proximal half-pin group. Minimal subperiosteal exposure around
the femur was obtained through the lateral exposure. An osteotomy
was then created 1 cm distal to the proximal pins with use of a
3.2-mm drill-bit to perforate the cortex multiple times and an osteotome
21
. The nail was reinserted and passed across the osteotomy site under
direct vision. The nail was then locked proximally with a 4.0-mm
screw, and the external fixator was assembled. An extensive soft-tissue
release, recommended by some authors
8,9
, was not performed.
Postoperative Care
Distraction typically began on the sixth postoperative day, with
0.25 mm of distraction accomplished every six hours (
Fig. 2-C
). Full weight-bearing was encouraged immediately. Initially, the
patients used crutches, and then they were weaned from them as tolerated.
Inpatient physical therapy for hip, knee, and ankle range of motion
was instituted twice daily. Pin care was limited to daily showers
22
. At the first sign of a pin-site infection (i.e., pain or erythema),
a ten-day course of oral antibiotics was begun. During physical
therapy, care was taken to maintain full knee extension, passive
knee flexion to at least 40°, and passive hip abduction
to at least 30°. All patients wore a knee extension brace
(a premeasured medial and lateral upright brace with an anterior
strap across the patella) as needed to maintain full passive knee
extension. Anteroposterior and lateral radiographs were made weekly
throughout the distraction period to evaluate callus formation.
A standing anteroposterior radiograph of the pelvis was made every
three weeks to evaluate hip position-specifically, early signs of hip
subluxation.
Once the planned lengthening had been achieved, the patient was
returned to the operating room, the intramedullary nail was interlocked
distally with a single 4.0-mm screw placed in an anteroposterior
direction, and the external fixator was removed (
2-D
). Full weight-bearing was continued with the use of crutches, but
without immobilization or bracing, and radiographs were made every
four weeks until consolidation and final reconstitution of the cortex
were complete. Crutch use was continued for four weeks after removal
of the external fixator.
Dynamization of the intramedullary nail by removal of the distal
interlocking screw was performed in all patients during a third
surgical procedure. This was usually done at five to ten months
after the index procedure, to maximize healing, after final reconstitution
could be observed on at least three of the four femoral cortices
(
Figs. 2-E
and
2-F
). We do not recommend nail removal before two years postoperatively.
At the conclusion of the lengthening procedure, the mechanical
axis was assessed on a standing, long-cassette radiograph as described
by Paley and Tetsworth
16,17
. Angulatory deformities, particularly distal femoral valgus, were
addressed by planning appropriate hemiepiphyseal stapling at the
distal part of the femur (
Fig. 2-G
). Often, hemiepiphyseal stapling was combined with dynamization
of the intramedullary nail.
Patient Demographics
The nine patients were followed for a mean of 128 weeks (range,
111 to 161 weeks). They ranged in age from eight to eleven years
(average age, nine years and ten months) at the time of the index
procedure. Four of the nine patients had had previous surgery on
the affected femur. Three had undergone prior lengthening procedures,
and one had undergone a closed reduction of a congenital hip dislocation
with a subsequent varus rotational osteotomy.
All patients had a preoperative scanogram and standing long-cassette
radiograph made of both lower extremities. The mechanical axis was
identified as it passed through the area of the knee and was classified
as crossing zone I, II, or III
15,23
. Bone age was determined on hand radiographs as described in the
atlas by Greulich and Pyle
24
. The Moseley straight-line graph method was used with multiple
data points to calculate projected limb-length discrepancy. The
average projected limb-length discrepancy was 8.4 cm (range, 6 to
11 cm), and the actual limb-length discrepancy at the time of the
procedure averaged 5.7 cm (range, 3.2 to 7.6 cm). Five patients
had an external rotation deformity ranging from 10° to 40°,
which was corrected by derotation at the lengthening site.
The time from the initial surgery to the removal of the external
fixator and locking of the intramedullary nail averaged eighty-two
days (range, seventy to ninety-eight days). Dynamization of the
intramedullary nail by removal of the distal interlocking screw
was performed at an average of seven months (range, five to ten
months) after the index procedure.
Radiographic Results
The femora were lengthened a mean of 6.1 cm (range, 5.0 to 8.0
cm), 19.5% (range, 15.9% to 26.2%) of the preoperative femoral length.
The mean lengthening index was 12.2 days/cm of length (range, 9.5
to 16.9 days/cm of length).
Examination of the preoperative and latest radiographs revealed
no nonunions or malunions at the osteotomy site. Consolidation and
reconstitution of the cortex were noted to be complete in all patients
within six months after the index procedure. No patient had evidence
of avascular necrosis on either anteroposterior or lateral radiographs.
During the course of treatment, three patients underwent hemiepiphyseal
stapling because of angular deformity (genu varum in one and genu
valgum in two). At the time of the latest follow-up, the mechanical
axis passed through zone I and was unchanged from that seen at the
preoperative evaluation in eight of the nine patients. In the ninth
patient, the mechanical axis changed from zone I to zone II with
mild valgus angulation at the time of the latest follow-up. The
mean lateral distal femoral angle increased from 83° (range,
79° to 86°) preoperatively to 88° (range,
83° to 92°) at the time of final follow-up, indicating
improvement of the distal femoral valgus deformity.
The neck-shaft angle and articulotrochanteric distance in both hips
were measured on preoperative and final follow-up radiographs in
an attempt to quantify any change in proximal femoral alignment.
The articulotrochanteric distance increased by a mean of 1 mm (from
16 mm to 17 mm) between the preoperative and final postoperative
radiographs, indicating a very slight increase in valgus. The femoral
neck diameter increased a mean of 9 mm (from 25 mm to 34 mm). The
neck-shaft angle decreased by a mean of 1° (from 133°
to 132°).
Clinical Results
The range of motion of the hip and knee was evaluated both preoperatively
and on a regular basis postoperatively. Neither hip nor knee subluxation
developed in any patient. Two patients required more than three
months of outpatient physical therapy at home for improvement of
the range of motion of the knee, but at two years postoperatively
all patients had regained both hip and knee motion to within 5°
of the preoperative values. No surgical procedures were required
to improve the range of motion.
Complications
A total of two operative fractures and two deep infections developed
during the course of treatment in three patients. One patient, with
a history of a congenital short femur, had a unicortical fracture
at the site of one of the distal half-pins three months after removal
of the frame. He was treated with limited weight-bearing, and the
fracture healed without any adverse sequelae. A second patient with
a history of congenital short femur sustained a fracture through
the distal locking site of the intramedullary nail. Varus deformity
developed, and 2 cm of length was lost. Nail replacement restored
the alignment.
Superficial pin-site infection developed in all nine patients. All
had resolution of pain, inflammation, and drainage within ten days
after the start of oral antibiotic therapy. In one patient, with
a history of multifocal neonatal osteomyelitis, osteomyelitis due
to
Staphylococcus aureus
developed one year after complete consolidation of the lengthening
site. He was treated successfully with intravenous antibiotics and
nail removal. At one year after removal of the nail, he had had
no recurrence of the infection.
A third patient, with a congenital short femur, who had had two
prior lengthenings of that femur sustained a fracture of the distal
part of the femur after removal of the distal interlocking screw.
He was treated with open reduction and renailing during a six-hour
procedure with extensive dissection. Osteomyelitis due to
Staphylococcus aureus
developed; it ultimately healed after intravenous administration
of antibiotics, removal of the intramedullary nail, and external
fixation of the fracture.
The concept of using an intramedullary nail in the femur to address
limb-length discrepancy is not new. A number of authors have described
closed femoral shortening performed over an intramedullary nail
25-28
. Epiphysiodesis is the preferred technique in skeletally immature
patients with a small limb-length discrepancy
29
. However, patients with a discrepancy of >5 cm often prefer femoral
lengthening. Drawbacks to femoral lengthening include prolonged
treatment with external fixation and many possible complications.
In a study consisting mostly of adults, Paley et al.
9
performed a matched-case comparison of lengthening over an intramedullary
nail and Ilizarov lengthening, with thirty-two femora in each group.
Use of the intramedullary method was associated with a decreased
duration of external fixation, faster consolidation, faster resumption
of a normal range of motion at the hip and knee, and fewer complications
overall. We adapted this method of lengthening of the femur over
an intramedullary nail for use in a preadolescent population. Several
potential complications were considered before we undertook this
trial.
While the use of an intramedullary nail for fixation of femoral fractures
in preadolescent patients has been discussed, the risk of avascular
necrosis of the femoral head makes this approach controversial.
Mileski et al.
13
reported a case of avascular necrosis of the femoral head after intramedullary
nailing in a thirteen-year-old child. The injury is thought to be
associated with damage to the posterior ascending branch of the
medial femoral circumflex artery. Others have also reported cases
of avascular necrosis of the femoral head following nailing through
the piriformis fossa in children
10-12,14
.
Because of the risk of capital femoral avascular necrosis, we do
not use the piriformis fossa as an entry point for the humeral nail.
Rather, we approach the femur through the lateral aspect of the
greater trochanter. To date, we have seen no evidence of avascular
necrosis in patients treated with this method.
Use of the greater trochanter as an entry point for intramedullary
nailing decreases the risk of avascular necrosis of the femoral
head and is relatively easy technically. However, the potential
for injury to the trochanteric physis must be considered. If growth
of the greater trochanter is completely ablated, an increase in
the articulotrochanteric distance and in the neck-shaft angle can
be expected. Altered joint mechanics and an altered gait pattern
may result as well. Gage and Cary
30
evaluated the use of trochanteric epiphysiodesis to treat capital
femoral avascular necrosis in infants and in a group of children
with an average age of six years. They found that, after the age
of eight years, at least 50% of the growth of the trochanter occurs
in an appositional fashion. Four children in their study had a trochanteric
epiphysiodesis after the age of eight years. There was no effect
on trochanteric growth in two of them, and the effect was minimal
in the other two.
Raney et al.
31
thought that active growth is present in the trochanteric physis
and that this physis extends toward the capital femoral epiphysis
into the second decade. They reported on five selected patients
treated with an intramedullary nail placed through the tip of the
greater trochanter; increased neck valgus and an increased articulotrochanteric
distance developed in all of these patients soon after surgery (usually
within the first year). Although their patients remained asymptomatic,
the authors recommended the use of other means of fixation to avoid
injury to this physis. Others have noted similar findings after
intramedullary nailing through the tip of the greater trochanter
11,18,31-34
.
Although it has not been proven, we believe that the injury in patients
with femoral neck valgus after transtrochanteric nailing lies in
the area between the trochanter and the femoral head. Inspection
of the radiographs in the reported cases of femoral neck valgus
revealed evidence of closure of the medial aspect of the trochanteric
physis and the lateral portion of the femoral neck physis
31,32
. We think that insertion of the nail through the lateral aspect of
the greater trochanter avoids this critical area and preserves growth
at the base of the femoral neck. Use of a nail with a proximal bend,
such as a humeral nail, facilitates the use of this lateral entry
point. This allows atraumatic insertion and has thus far prevented
an increase in either the articulotrochanteric distance or the neck-shaft
angle in our patients.
Osteomyelitis developed in two patients in our series. In one patient,
who had had multifocal osteomyelitis as an infant, the osteomyelitis
developed after consolidation. The infection resolved after removal
of the nail and a six-week course of intravenous antibiotics. In
the second patient, the osteomyelitis developed after open reduction
with internal fixation of a fracture at the tip of the nail that
had occurred after consolidation of the lengthening site. It is
unclear whether the infection in this patient was related to the
index procedure or to the extensive dissection performed at the
time of the fracture treatment. However, this high rate of late
infection raises a serious concern about the use of this technique,
and additional study and follow-up are necessary.
All of our patients had regained the preoperative range of motion
at the time of final follow-up, and only two required a prolonged
home range-of-motion program to obtain that motion. This result
compares favorably with the experience of Herzenberg et al.
35
, who reported that five (20%) of twenty-five patients lost knee
motion after Ilizarov femoral lengthening.
With the Ilizarov technique, very extensive lengthening is possible:
increases of as much as 60% of the bone's preoperative length have
been achieved successfully. However, lengthening of >20%, particularly
in patients with congenital limb-length discrepancy, has been associated
with a high rate of complications and with concerns about the long-term
effects on articular cartilage
7
. An important limitation of our technique is that lengthening is
possible only for the length of the intramedullary nail that lies
distal to the osteotomy site. A portion of the nail must remain
within the femoral canal at the conclusion of the lengthening to
maintain adequate angulatory control. In one patient, the lengthening
was accomplished with only 1.5 cm of the nail remaining within the
distal fragment. Subsequently, after removal of the fixator and
locking of the nail, angulation and loss of length occurred. The
lengthening was salvaged with removal of the nail and placement
of a longer nail. Because of this experience, we now leave at least
4 cm of the nail within the distal fragment at the time of fixator removal.
The use of an intramedullary device necessitates lengthening along
the anatomic axis, which has the theoretical risk of increasing
the genu valgum deformity normally associated with a congenital
short femur or producing a valgus deformity in patients with a mechanically
straight lower extremity. Although we noted some increased valgus
in some patients, the change in alignment seems to be minimal. Three
patients were treated with hemiepiphyseal stapling for residual
angular deformity after the lengthening. At the latest follow-up evaluation,
eight of the nine patients had a zone-I mechanical axis. At the
time of writing, hemiepiphyseal stapling was planned for a later
date in the ninth patient.
As with any surgical intervention performed for lengthening, there
is a risk of producing growth acceleration leading ultimately to
overlengthening or growth deceleration leading to underlengthening
of the involved limb segment. Sharma et al.
36
reported growth deceleration after lengthening in patients with
congenital limb-length discrepancy. To date, we have not detected
any effect on later growth of the affected limb. However, to fully
assess this concern, these patients should be followed to skeletal
maturity.
In conclusion, lengthening over a humeral nail for the treatment
of limb-length discrepancy due to femoral shortening decreases the
duration of treatment with the fixator and also decreases the lengthening
index. Soft-tissue tethering with loss of motion is also minimized.
Important problems include the risk of infection and of refracture
at the tip of the nail. Unanswered questions remain regarding the
long-term effect on trochanteric growth. Although additional follow-up
and experience are needed, this technique seems to show promise for
dealing with some of the problems encountered with use of the Ilizarov
technique.