Abstract
Background: Late-onset tibia vara (Blount disease) can be difficult
to treat because of frequent morbid obesity and associated deformities,
including distal femoral varus, proximal tibial procurvatum, and distal tibial
valgus, that contribute to lower extremity malalignment. We present a
comprehensive approach that addresses all components of the deformity and
allows restoration of the anatomic and mechanical axes.
Methods: Fifteen consecutive patients (nineteen lower extremities)
with late-onset tibia vara were managed with this comprehensive approach. The
mean age of the patients at the time of surgery was 14.9 years, and the mean
weight was 113 kg. Standing anteroposterior and lateral radiographs were made
preoperatively and at the time of the final follow-up. Preoperatively, the
mean mechanical axis deviation was 108 mm, the mean lateral distal femoral
angle was 95°, and the mean mechanical medial proximal tibial angle was
71°. In all nineteen extremities, the proximal tibial varus deformity was
corrected by means of a valgus osteotomy and application of an Ilizarov ring
external fixator. Distal femoral varus was corrected by means of either
hemiepiphyseal stapling or valgus osteotomy with blade-plate fixation in
thirteen of the nineteen extremities. Distal tibial valgus was treated either
with hemiepiphyseal stapling or with varus osteotomy and gradual correction
with use of the Ilizarov external fixator in eleven of the nineteen
extremities.
Results: After a mean duration of follow-up of 5.0 years, the mean
mechanical axis deviation had improved to 1 mm (range, 20 to -30 mm), the
lateral distal femoral angle had improved to 87° (range, 83° to
98°), and the mechanical medial proximal tibial angle had improved to
88° (range, 83° to 98°). The mean time required for correction of
the proximal tibial varus deformity was thirty-one days, and the external
fixator was removed at a mean of 4.5 months postoperatively. All patients had
development of one or more superficial pin-track infections (mean, 1.9
pin-site infections per patient). No wound infections, nonunions, or
neurovascular complications occurred. Eighteen of the nineteen extremities
were pain-free at the time of the final follow-up.
Conclusions: This comprehensive approach allowed restoration of the
mechanical and anatomic axes of the lower extremity in patients with
late-onset tibia vara, resulting in a resolution of symptoms as a result of
normalization of the weight-bearing forces across the knee and ankle. We
believe that this approach will decrease the risk of early degenerative
arthritis of the knee.
Level of Evidence: Therapeutic Level IV. See Instructions
to Authors for a complete description of levels of evidence.
Blount described a group of children who had an onset of varus
deformity of the proximal part of the tibia in later childhood or adolescence,
a condition that he described as adolescent tibia
vara1. Thompson et
al. clarified this classification by categorizing patients who had had a
juvenile onset of varus deformity (at the age of four to ten years) along with
those who had had a true adolescent onset (at the age of eleven years or more)
as having late-onset tibia
vara2,3.
Early-onset or infantile tibia vara is characterized by a more severe proximal
tibial deformity and substantial depression of the medial aspect of the
proximal tibial
epiphysis2-5.
Children with late-onset tibia vara present a challenging combination of
marked genu varum deformity, usually accompanied by
obesity6. The
deformity usually develops in middle childhood or early
adolescence7,8
and is differentiated from infantile tibia vara on the basis of the less
severe epiphyseal deformity and the history of normal lower extremity
alignment prior to the development of a genu varum
deformity1,4,5,9.
Although the name of the disorder suggests that varus of the proximal part
of the tibia is the only deformity present, this is not the case. The proximal
tibial varus deformity is produced by a posteromedial growth suppression,
which initially produces varus and then progressive procurvatum of the
proximal part of the
tibia3,9-12.
Associated toeing-in gait also worsens as the deformity progresses, initially
as a functional maneuver to allow the foot to be placed as close to the line
of progression as possible and subsequently as a result of progressive
internal tibial
torsion9. The
combination of proximal tibial varus and procurvatum as well as internal
tibial torsion results in a complex three-dimensional deformity. The
progressive proximal tibial varus deformity produces increased forces on the
medial aspect of the distal femoral physis, leading to growth suppression and
a distal femoral varus deformity as well. In severe cases, the varus deformity
in the distal part of the femur can be nearly as severe as that in the
proximal part of the
tibia13. As the
proximal tibial and distal femoral varus deformities increase, substantial
strain is placed on the lateral collateral ligament of the knee, which can
lead to laxity and instability of the knee
joint9. Finally, in
severe cases, compensatory distal tibial valgus may develop, allowing the
patient to align the ankle joint parallel to the
floor9.
Although the formation of an osseous bar across the medial aspect of the
proximal tibial physis along with medial epiphyseal depression is not uncommon
in patients with severe infantile tibia vara, similar bar formation in
patients with late-onset tibia vara has not been reported, to our
knowledge5,14,15.
Depression of the medial aspect of the proximal tibial epiphysis requiring
medial plateau elevation has not been reported in patients with late-onset
tibia vara4.
Although late-onset tibia vara occasionally may occur in thin or
normal-sized patients, the majority of patients are
obese2,6,16-21.
These patients typically are in the ninetieth percentile of weight for both
age and
height17,18,20-22.
During normal walking, nonobese individuals place the foot close to the
midline of foot progression, thereby minimizing weight transfer and energy
expenditure. Obese individuals with large thighs have a very difficult time
adducting the hip adequately to place the foot for midline progression. Davids
et al.22 speculated
that this "fat thigh syndrome" produces a varus moment on the knee
that leads to increased pressure on the medial aspect of the proximal tibial
physis and inhibits growth in accordance with the Hueter-Volkmann
law23.
Since 1994, we have addressed all of the deformities associated with
late-onset tibia vara with a comprehensive approach. Proximal tibial varus is
treated with a valgus osteotomy followed by gradual correction with use of an
Ilizarov external fixator. If the patient has open physes and adequate growth
remains for correction of the deformities of the distal part of the femur and
distal part of the tibia, hemiepiphyseal stapling is performed. When the
physes are closing, these deformities are corrected with osteotomy. Distal
femoral varus is treated with a valgus osteotomy and stabilization with a
blade-plate. Distal tibial valgus is treated with a varus osteotomy followed
by gradual correction with use of an Ilizarov external fixator. All procedures
are performed simultaneously. The purpose of the present study was to evaluate
the results of this comprehensive approach to the deformities in patients with
late-onset tibia vara.
Fifteen consecutive patients (nineteen lower extremities) with
late-onset tibia vara were managed with our comprehensive approach between
January 1, 1994, and December 31, 1998. Medical records, hospital charts, and
radiographs were retrospectively reviewed with regard to demographic
characteristics, operative procedures, complications, and functional and
radiographic data. All nineteen extremities underwent a proximal tibial valgus
osteotomy followed by gradual correction of the proximal tibial varus
deformity with use of an Ilizarov circular external fixator
(Smith-Nephew-Richards, Memphis, Tennessee). This device was also used to
correct associated proximal tibial procurvatum and internal tibial torsion.
The distal femoral varus deformity was corrected with use of a valgus
osteotomy and stabilization with a 95° adult condylar blade-plate
(Synthes, Paoli, Pennsylvania) if insufficient growth remained to allow
lateral hemiepiphyseal stapling. Distal tibial valgus deformity was treated
either with medial hemiepiphyseal stapling or with varus osteotomy and gradual
correction with use of an extension of the Ilizarov frame. All patients were
followed for a minimum of two years postoperatively.
The lower extremities were evaluated preoperatively and at the time of the
final follow-up with use of standard radiographs. These included a standing
anteroposterior radiograph of both lower extremities; a standing
anteroposterior radiograph of both ankles, showing the distal half of the
tibia; and a lateral radiograph of the knee, showing the proximal half of the
tibia. Line measurements were performed according to the system of Paley et
al. (Figs. 1-A and
1-B)24-27.
These measurements included the mechanical axis deviation, the mechanical
lateral distal femoral angle (normal, 88°; range, 86° to 89°), the
mechanical medial proximal tibial angle (normal, 87°; range, 85° to
89°), the mechanical lateral distal tibial angle (normal, 91°; range,
88° to 95°), and the joint-line congruency angle (normal, 2°;
range, 1° to 3°). Lateral radiographs were evaluated to determine the
posterior proximal tibial angle (normal, 80°; range, 77° to
84°).
All patients complained of pain in the involved knee or knees
preoperatively and were observed to have a lateral knee thrust when
walking.
The mean age at the time of surgery was 14.9 years (range, 10.6 to 18.1
years). The etiology was juvenile onset tibia vara for three patients and
adolescent tibia vara for the remaining twelve patients. The mean weight was
113 kg (range, 43 to 178 kg). Thirteen patients (87%) were above the
ninety-fifth percentile for weight according to their age, and fourteen
patients (93%) were above the ninety-fifth percentile for weight according to
their height. Four patients were so obese that they had sleep apnea that
necessitated nighttime use of continuous positive airway pressure.
Preoperative anteroposterior radiographic measurements of the lower
extremities demonstrated a mechanical axis deviation of 108 mm (range, 41 to
208 mm), a mean mechanical lateral distal femoral angle of 95° (range,
82° to 102°), and a mean mechanical medial proximal tibial angle of
71° (range, 61° to
77°)28,29.
These measurements all indicated substantial lower extremity malalignment. The
mean joint-line congruency angle was 3° (range, -2° to 12°).
Radiographs of the ankles revealed a mean mechanical lateral distal tibial
angle of 85° (range, 79° to 93°). Lateral radiographs revealed a
mean posterior proximal tibial angle of 71° (range, 58° to 88°).
The mean preoperative lower limb-length discrepancy in the eleven patients
with unilateral disease was 14 mm (range, 0 to 30 mm) as assessed either with
scanography or on the standing anteroposterior radiograph of both lower
extremities. None of the four patients with bilateral disease had a
substantial limb-length discrepancy.
All nineteen extremities had a proximal tibial osteotomy with placement of
an Ilizarov circular external fixator. Correction of the distal femoral varus
was indicated if the lateral distal femoral angle was >95°
(representing >5° of mechanical varus). According to this criterion,
thirteen of the nineteen femora had a distal varus deformity that required
correction. Eleven of these thirteen extremities had a distal femoral valgus
osteotomy with blade-plate fixation, whereas the other two had enough
remaining growth to undergo lateral distal femoral hemiepiphyseal
stapling.
Correction of the distal tibial valgus deformity was performed if the
mechanical lateral distal tibial angle was =86° (representing
=5° of mechanical valgus). According to this criterion, eleven of the
nineteen tibiae had a distal valgus deformity that required correction. Eight
of these extremities had a distal tibial varus osteotomy with gradual
correction, and the other three were corrected by means of medial
hemiepiphyseal stapling. Two extremities had lateral instability of the knee
secondary to lateral collateral ligament laxity and were treated with
concomitant distal transport of the proximal part of the fibula to tighten the
ligament. Four extremities underwent only a proximal tibial osteotomy, six
extremities underwent a proximal tibial osteotomy with correction of either
the distal part of the femur or the distal part of the tibia, and seven
extremities underwent deformity correction at the proximal part of the tibia,
the distal part of the femur, and the distal part of the tibia. Two
extremities required deformity correction at the proximal part of the tibia,
the distal part of the femur, and the distal part of the tibia as well as
fibular transport to tighten the lateral collateral ligament.
Surgical Technique
Preoperatively, radiographs were analyzed and planning was performed
according to the techniques described by Paley and
Tetsworth24,25.
An Ilizarov circular external fixator was preconstructed to lengthen the tibia
as needed and to simultaneously correct varus and procurvatum through an
oblique-plane placement of the hinges. After correction of the angulatory
deformity and restoration of length, the fixator was modified in situ to
correct rotational malalignment. In two patients (three tibiae) with greater
rotational deformity, an inclined oblique-plane hinge initially was
constructed to provide simultaneous correction of alignment in the frontal,
coronal, and rotational planes, with restoration of length. If the patient was
skeletally mature, a proximal two-ring block, with the rings located
approximately 2 cm apart, was utilized to stabilize the proximal part of the
tibia. If the patient was skeletally immature, a single proximal ring was used
to avoid performing the osteotomy distally in the diaphysis of the tibia. This
proximal ring block was connected to the distal ring segments with
appropriately placed hinges or struts. Two distal rings were used; the rings
were locked with rods if a distal tibial osteotomy was not required, and they
were connected with appropriately placed hinges or struts if a distal
osteotomy was to be performed. If clinically important lateral collateral
ligament laxity was present, a separate block of pins was used to secure the
distal end of the proximal fibular fragment and to transport it distally,
thereby tightening the lateral collateral ligament.
After appropriate general endotracheal anesthesia had been induced and the
patient had been carefully positioned on a radiolucent surgical table
(Orthopedic Systems, Hayward, California), the entire lower extremity was
prepared and draped and a sterile tourniquet was placed about the proximal
part of the thigh. The distal femoral varus deformity was corrected first,
when necessary. A supracondylar distal femoral opening-wedge valgus osteotomy
was performed through a lateral
approach30-33.
A large Kirschner wire was first placed perpendicular to the lateral cortex of
the femur to serve as a reference wire. A second Kirschner wire was then
placed into the distal metaphysis at or just proximal to the physis. It was
oriented such that the subtended angle between it and the initial Kirschner
wire was 5° less than the preoperatively measured deformity (to allow for
the placement of the 95° condylar blade-plate). The initial reference
Kirschner wire was then removed. The chisel was then placed into the distal
femoral metaphysis, just proximal and parallel to the second Kirschner wire
and the blade length. An osteotomy was then created 2 cm proximal to the
chisel with use of an oscillating saw, and the chisel was withdrawn. The
five-hole 95° blade-plate was then inserted into the slot created by the
chisel and was impacted into place. The second Kirschner wire was then
removed. The distal part of the femur and the attached blade-plate were then
reduced to the femoral shaft, creating a stable opening-wedge osteotomy.
After the femoral osteotomy but prior to closure of the femoral wound,
while the tourniquet was still inflated, a posterolateral incision was made
over the fibula at the junction of its middle and distal thirds. Subperiosteal
exposure of the fibula was performed to avoid injury of the branches of the
deep peroneal nerve to the extensor hallucis longus or the peroneal artery and
vein. A 1-cm section of the fibula was removed with use of an oscillating saw
and, if necessary, was cut into pieces and placed into the femoral osteotomy
site as bone graft. Both femoral and fibular osteotomy wounds were then
thoroughly irrigated and closed. The femoral wound was closed over a
drain.
If hemiepiphyseal stapling of the distal part of the femur or the distal
part of the tibia was planned, the staples were placed extraperiosteally under
fluoroscopic guidance as described by Zuege et
al.34 prior to
application of the external fixator.
The tourniquet was deflated, the preconstructed circular fixator was placed
onto the lower extremity, and suction tubing was used to suspend the leg
within the external fixator. This tubing was placed under the leg and over the
external fixator and was clamped into place with use of hemostats to secure
the leg appropriately within the fixator. Transverse and transfibular wires
initially were placed both proximally and distally, with care being taken to
place the closest wires approximately 5 mm away from the physis. If a fibular
transport to tighten the lateral collateral ligament had been planned, no
transfibular wire was placed. The transfibular wire, if placed, was positioned
within the metaphysis of the fibula as the surgeon carefully palpated to
identify and avoid the peroneal nerve. If a distal tibial osteotomy was
necessary, a second distal transverse wire was placed. Anterolateral and
anteromedial half-pins were then placed into the proximal part of the tibia.
Three or four half-pins were then placed into the tibial diaphysis, in
locations ranging from anterior to medial.
The tourniquet was reinflated and the proximal tibial osteotomy was
performed after a careful subperiosteal exposure distal to the patellar tendon
insertion and approximately 1 cm distal to the proximal tibial fixation pins.
A drill was used in a plane parallel to the proximal ring to outline the
osteotomy site according to the technique described by De Bastiani et
al.35. An Ilizarov
osteotome was used to connect the drill-holes and to cut the medial and
lateral tibial cortices. The osteotome was then driven into the osteotomy site
and was twisted to complete the osteotomy and to fracture the posterior
cortex. If required, a distal tibial osteotomy was created in an identical
fashion. The wounds were then closed, and the tourniquet was deflated.
Generous pin releases were performed at the conclusion of the procedure.
Gradual correction was begun on the second postoperative day at a rate of
0.25 mm every six hours. Serial radiographs were made weekly and as needed to
monitor correction and bone formation. The patient was encouraged to bear
weight as early as possible, and vigorous physical therapy was instituted to
maintain mobility and range of motion of the knee and ankle. Daily showers
were instituted as pin care and soft-tissue releases were carried out as
needed36. The
fixator was left in place and was progressively dynamized until complete
consolidation of the osteotomy site had occurred.
The fifteen patients were followed postoperatively for a mean of 5.0
years (range, 2.3 to 9.8 years). All patients were skeletally mature at the
time of the last follow-up. The mean time required for correction of the
proximal tibial varus deformity was thirty-one days (range, eleven to
sixty-eight days). The external fixator was removed after a mean of 4.5 months
(range, 2.9 to 6.4 months).
All patients had clinical improvement. At the time of the last follow-up,
fourteen patients (eighteen extremities) were asymptomatic and one patient
(one extremity) continued to complain of knee pain, the etiology of which
could not be determined. The latter patient had a final mechanical axis
deviation of 7 mm lateral to the joint center, with good alignment of the
distal part of the femur and the proximal part of the tibia. Magnetic
resonance imaging demonstrated no evidence of intra-articular abnormality. The
pain did not limit the patient's activities, and the patient declined
additional intervention.
The lateral knee thrust was eliminated in all patients. All patients had
regained full ranges of knee and ankle motion at the time of the last
follow-up. No patient had clinically important knee laxity to varus or valgus
stress at the time of the last follow-up.
Radiographs that were made at the time of the last follow-up revealed
improvement in lower extremity alignment. The mechanical axis deviation
improved to a mean of 1 mm (range, 20 to -30 mm)
(Table I). The lower
extremities were essentially equal in length, with a mean discrepancy of 1 mm
(range, -22 mm to 6 mm) at the time of the final follow-up
(Figs. 2-A through 2-H).
The mean mechanical lateral distal femoral angle improved to 87°
(range, 83° to 98°). In the two patients who underwent hemiepiphyseal
stapling, the mechanical lateral distal femoral angle improved from 92° to
87° in one patient and from 96° to 87° in the other. The
mechanical lateral distal femoral angle in the eleven patients who underwent
distal femoral osteotomy improved from a mean of 97° (range, 94° to
102°) to a mean of 88° (range, 84° to 96°).
The mean mechanical medial proximal tibial angle improved to 88°
(range, 83° to 98°). The mean joint-line congruency angle improved to
2° (range, 0° to 5°). The mean posterior proximal tibial angle
improved mildly from 71° (range, 58° to 88°) to 77° (range,
57° to 89°). The mean mechanical lateral distal tibial angle improved
slightly from 85° (range, 79° to 93°) to 89° (range, 82°
to 93°). The mean mechanical lateral distal tibial angle in the three
patients who underwent hemiepiphyseal stapling of the distal part of the tibia
improved from 84° (range, 83°, 86°, and 83°) to 89°
(86°, 88°, and 92°). The mean mechanical lateral distal tibial
angle in the eight patients who underwent osteotomy of the distal part of the
tibia improved from 83° (range, 79° to 86°) to 90° (range,
86° to 92°).
All patients had development of one or more superficial pin-site infections
(mean, 1.9 infections per patient), which resolved with oral
antibiotics36. No
patient required intravenous antibiotic therapy. No neurovascular
complications were encountered. No patient had development of a deep
infection, osteomyelitis, or nonunion.
Postoperatively, the need for additional procedures required fourteen of
the fifteen patients to return to the operating room between one and three
times per involved extremity. Removal of the external fixator under a general
anesthetic was requested by the patient for eighteen of the nineteen
extremities. Other indications for additional procedures included wire removal
(thirteen patients), fixator modification (two patients), and staple removal
(two patients). In all, only one extremity required no additional procedures,
six required one additional procedure, nine required two additional
procedures, and three required three additional procedures.
Patients with late-onset tibia vara typically are obese and can
present with complaints of genu varum, knee pain, toeing-in, or knee
instability5,16-19,22.
The natural history of this condition is unclear, but residual infantile tibia
vara leads to chronic knee pain and degenerative
arthritis37-40.
Varying amounts of respiratory distress may be present, depending on the
patient's obesity and activity
level41-43.
Occasionally, even the walk from the waiting room to the examination area can
be exhausting for these patients. Patients with knee pain often describe
medial pain and symptoms of increased pressure in the medial compartment of
the knee as well as symptoms of anterior knee pain, probably secondary to
maintenance of the knee in a flexed position during gait.
A standing long-cassette anteroposterior radiograph of both lower
extremities is essential for the evaluation of these patients. If the patient
appears to have unilateral bowing, careful attention should be paid to the
contralateral limb because the patient's obesity frequently can mask mild
contralateral genu varum. Because of the obesity of these patients, we have
found it necessary to make preoperative preparations for special equipment,
including a large tourniquet and a radiolucent table that can support the
patient's weight.
Although some authors have recommended physeal distraction as a means of
achieving correction, this is not possible in skeletally mature
adolescents44,45.
Laurencin et al.46
effectively utilized an oblique, laterally based closing-wedge osteotomy that
hinges at the intact cortex just distal to the proximal tibial physis for
acute correction of mild deformities. Most patients with late-onset tibia vara
require at least proximal tibial osteotomy to correct the deformity. Osteotomy
with limited internal fixation, the mainstay of treatment of infantile tibia
vara5,15
has little application in the treatment of late-onset tibia
vara18.
The obesity of the patient makes the application of a well-fitting
above-the-knee cast difficult, if not impossible, and prevents the adequate
control of the position of the osteotomy site. In addition, the older age and
size of the patient make patient mobility highly desirable. The problems
associated with non-weight-bearing on the affected extremity make walking
extremely difficult for these patients. Furthermore, the difficulties
associated with assessing limb alignment either intraoperatively or
postoperatively make residual proximal tibial varus or undercorrection a
possibility. External fixation of the tibia is indicated for the correction of
more severe
deformities21,47-49.
This allows either acute or gradual correction with a monolateral or circular
fixator. Price et al. demonstrated that monolateral fixation with either acute
or gradual correction can effectively correct the tibial varus deformity in
the frontal
plane48. Alignment
in the sagittal plane and rotational correction are more difficult to obtain
with use of the monolateral
fixator21,50.
A detailed preoperative plan is essential for any surgical procedure. The
magnitude and location of the various osseous deformities, laxity of the
lateral collateral ligament, the presence of joint contractures, and lower
limb-length discrepancy should all be assessed and incorporated into the
preoperative plan. The overall plan should correct each of the constituent
deformities, normalizing the mechanical and anatomic axes in order to avoid
increased stresses resulting from chronic malalignment as well as increased
sheer forces on the knee or ankle resulting from joint-line obliquity.
Although the long-term results of our comprehensive technique are not known,
this approach has provided pain relief, a stable correction, and restoration
of normal lower extremity alignment in this difficult patient population.
During the planning and execution of the varus correction, particular
attention should be paid to normalizing distal femoral and proximal tibial
alignment. Because of the obesity of these patients, joint-contact forces are
excessive even when normal mechanical alignment is present. Although the
mechanical alignment in these patients could be corrected through a single
tibial osteotomy that compensates for existing femoral varus, this would leave
the knee joint oblique to the mechanical axis and would introduce sheer forces
during weight-bearing. Because of these concerns, we believe that it is
essential to correct all of the deformities separately in order to provide
optimal mechanical alignment and to delay the onset of degenerative
arthritis.
Circular external fixation with gradual correction of the proximal part of
the tibia allows for maximal adjustability of the alignment in all planes and
is indicated for more severe deformities and the most obese
patients17,51.
Other advantages include stable fixation with improved patient mobility; the
ability to evaluate alignment in a functional, standing position; and the
ability to accurately correct all deformities of the tibia, including proximal
tibial varus and procurvatum, internal tibial torsion, and distal tibial
valgus.
After correction of the genu varum deformity, the distal tibial valgus, if
uncorrected, can produce a pes planus deformity with hindfoot
valgus9. This
persistent distal tibial valgus leaves the ankle in a position in which it is
oblique to forces involved in walking, leading to sheer forces at the joint
surface. This can become painful, particularly in obese patients with
late-onset tibia vara. Wagner et
al.52 found
decreased tibiotalar contact areas at the ankle in patients with distal tibial
deformities of =10°. Ting et
al.53 found that
this effect was exacerbated in patients with decreased subtalar motion who
were unable to compensate for the valgus. This has led us to correct
deformities of >5° at the distal part of the tibia.
In conclusion, this comprehensive approach to late-onset tibia vara is
effective, but careful preoperative planning and an analysis of all of the
deformities are essential. In particular, correction of each of the
deformities in the lower extremity allows the mechanical alignment of the
lower extremity to be optimized with the restoration of anatomic and
mechanical axes. This approach has led to relief of pain through adolescence,
and we are hopeful that it will eliminate the onset of degenerative arthritis
in the knee and ankle, although the long-term results remain to be seen.
?
The authors did not receive grants or outside funding in support of their
research or preparation of this manuscript. They did not receive payments or
other benefits or a commitment or agreement to provide such benefits from a
commercial entity. No commercial entity paid or directed, or agreed to pay or
direct, any benefits to any research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
authors are affiliated or associated.
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