Nonunion After High Tibial Osteotomy
S. Robert Rozbruch, MD - Hospital for Special Surgery, Limb Lengthening
John E. Herzenberg, MD - Institute for Advanced Orthopaedics, Sinai
Hospital, Baltimore, Maryland
Kevin Tetsworth, MD - Rockhampton Queensland, Australia
H. Robert Tuten, MD - Private Practice, Georgia
Dror Paley, MD - Institute for Advanced Orthopaedics, Sinai Hospital,
Published in Clinical Orthopaedics and Related Research,
Number 394, January 2002
The purpose of this study was to determine whether distraction osteogenesis
can be used to treat hypertrophic nonunion associated with angular
deformity and shortening after Coventry style high tibial osteotomy.
Five consecutive patients were retrospectively reviewed. In all cases,
the alignment had collapsed into excessive varus or valgus and leg
length discrepancy was present. The leg length discrepancy, mal-alignment,
and nonunion were treated simultaneously with distraction.
All cases resulted in union by the time of fixator removal, which
averaged 4.4 months. Hospital for Special Surgery knee score significantly
improved from 42 to 89. The mechanical axis deviation significantly
improved by 5 cm. The coronal plane deformity significantly improved
by 13°, and leg length discrepancy improved significantly from
2.3 cm to 0.5 cm. Metaphyseal bone stock increased by 43%, and the
Insall-Salvati ratio increased from 1.1 to 1.2 and remained within
normal limits. All patients were satisfied with the procedure, and
none have had nor need a total knee replacement at an average followup
of 4 years. Distraction osteogenesis of nonunion after high tibial
osteotomy is a minimally invasive and successful procedure. It leads
to bony union with correction of deformity and leg length discrepancy
and prevents the need for total knee replacement at intermediate-term
followup. The increase in metaphyseal bone stock may make future total
knee replacement technically easier.
Nonunion after high tibial osteotomy is uncommon. Coventry4
reported no nonunions in a series of 213 osteotomies. Myrnerts17
reported one nonunion in 78 proximal tibial osteotomies, an incidence
of 1.3%, and Bauer et al1
reported one nonunion in 66, a 1.5% incidence. Tjornstrand et al26
reported 10 nonunions in 280 osteotomies, an incidence of 3.6%. In
the English language orthopaedic literature, four reports address
the treatment of this problem.2,24,26,28
The numbers of patients in these reports are small, and the treatments
variable. Tjornstrand et al26
advocated open resection of the nonunion followed by Charnley external
transfixation and casting in their report of 12 cases. Schatzker et
closed compression of the nonunion with external fixation in their
report of three cases. Wolff and Krackow28
advocated open treatment with bone grafting and plating in their report
of six cases. Cameron et al2
reported the use of a double plating technique with bone grafting
in their report of 10 cases. Most of these articles focus on the problem
of nonunion and address alignment secondarily. None address the issue
of axial length, patella height, or metaphyseal bone stock, which
are important considerations for future total knee replacement.12,16,27
introduced a novel approach for treating hypertrophic nonunions using
an external fixator to stimulate osteogenesis by distraction through
the nonunion site. There have been four reports in the English language
orthopaedic literature in which distraction osteogenesis has been
used successfully to treat hypertrophic nonunions with deformity after
Hypertrophic nonunions are well vascularized, but union is prevented
by the lack of stability. The fibrocartilaginous tissue of a hypertrophic
nonunion has osteogenic potential, which can be realized once the
proper biomechanical environment is established. Contrary to popular
belief, compression is not required for healing. When the torsion
and shear forces are eliminated, distraction or compression forces
applied to the site of the nonunion lead to new bone formation and
healing of the nonunion. During this process, limb deformity and shortening
can be corrected.3
This concept of treatment was used in five patients with nonunion
after high tibial osteotomy associated with deformity and shortening.
This represents a series of cases dealing exclusively with a previously
unreported technique of management of this uncommon but challenging
problem. It is also the first study of nonunions after high tibial
osteotomy to report on leg length discrepancy, in addition to bony
union, angular deformity, and functional outcome.
Materials and Methods:
Five patients with nonunion and deformity following high tibial osteotomy
were treated with distraction osteogenesis from 1994 to 1998. Four
of the five patients were referred for treatment. One patient had
the high tibial osteotomy performed at the authors' center. The average
patient age was 46.6 years (range, 35-57 years), and the average interval
from the index surgery to treatment was 8.4 months (range, 6-9.5 months).
All procedures were done percutaneously with application of a circular
external fixator or monolateral external fixator. In no case was the
nonunion site opened nor was any bone grafting used. Four of the five
patients had hardware from the initial high tibial osteotomy. In one
patient, the proximal internal fixation screws were removed percutaneously.
In a second patient, the hardware was removed through a lateral incision.
The hardware was not removed in the other two patients since its presence
was not felt to interfere with the planned surgery. The outcomes were
evaluated by radiographic analysis and with the Hospital for Special
Surgery knee score.
Radiographic analysis included preoperative and postoperative measurements
of leg length discrepancy, mechanical axis deviation, medial proximal
tibial angle, posterior proximal tibial angle20
and Insall-Salvati ratios.11
A point 1.5 cm lateral to the midline was chosen as the mechanical
axis deviation goal to calculate the change in mechanical axis deviation
and for statistical analysis. This was modified from the concept of
Fujisawa et al.6
Anatomic femorotibial angle was measured, and a goal of 10° of
valgus was chosen to calculate the preoperative to postoperative change.
This was based on the concept of Insall et al.12
Additionally, the amount of metaphyseal bone stock was quantified.
On the frontal plane radiograph, a direct measurement of the metaphysis
was made from the medial tibial plateau joint line to a fixed point
in the metaphysis distal to the osteotomy nonunion. The fixed point
chosen was a visible landmark, such as a screw thread or hole. Magnification
error was corrected to allow comparison of preoperative and postoperative
radiographs. The metaphyseal bone stock percent change was calculated
Difference in metaphyseal height / preoperative metaphyseal height
Clinical outcomes were evaluated with the Hospital for Special Surgery
This evaluation included pain with walking and at rest, function related
to walking, stair climbing, and transfers, knee range of motion (ROM),
strength, deformity, and instability.
Statistical analysis was performed using the Student's paired t test.
The Ilizarov device (Smith & Nephew Orthopaedics, Memphis, TN) was
used in two patients. Multiple opposed 1.8mm olive wires were inserted
into the proximal fragment under careful fluoroscopic control. The
rings were assembled onto the wires. Care was taken to avoid placement
of intraarticular wires by staying as close to the nonunion as possible.
Contact with internal hardware was avoided to help prevent deep infection.
The frame was then was assembled and hinges were placed on the bisector
line of the center of angulation and rotation at the convex edge of
the bone to induce an opening wedge correction.20
The Orthofix monolateral fixator (Orthofix Inc., Richardson, TX) was
used in 3 patients. Two half-pins (6mm) were inserted into the proximal
fragment from the medial side. Care was taken to avoid contact with
internal hardware with careful insertion of a 1.8 mm guide wire. A
4.8mm cannulated drill was used to create the drill hole for the solid
6mm half pin. A T-clamp with a variable axis hinge distraction was
used to distract the nonunion.
A fibula osteotomy was not performed. If the nonunion was stiff (less
than 5° mobility), distraction was started immediately. Distraction
rates were adjusted so that the fastest moving edge of the bone lengthened
at 1mm per day. If the nonunion was partially mobile (5° to 20°
of mobility), distraction was started after an initial period of compression
of 1/2mm two times daily for one to two weeks. The bone formation
was inspected on the radiograph, and the distraction rate was adjusted
accordingly. Weight bearing as tolerated was allowed throughout the
The average followup was 4 years (range, 2-6 years). The average time
in the external fixator was 4.4 months (range, 2.5-5.5 months). This
represented time to bony union. The average knee ROM improved from
0° to 105° to 0° to 116°. The average preoperative
leg length discrepancy was 2.3cm (range, 1.8-2.7cm). This improved
to an average postoperative leg length discrepancy of 0.5cm (range,
0-1cm) (p = 0.0027). The average mechanical axis deviation improvement
in four patients was 5.0cm (p = 0.007). Mechanical axis deviation
measurements were not available in one patient.
The average tibial coronal plane deformity correction was 17°
(range, 7°-22°). The anatomic femorotibial angle deformity
changed from an average of 17.4° deformity (range, 5°-30°)
to an average of 4.8° deformity (range, 1°-14°) (p = 0.0031)(Fig
The average preoperative medial proximal tibial angle was 80°
(range, 70°-103°). This improved to an average postoperative
medial proximal tibial angle of 92° (range, 89°-93°)(Fig
2). In four of the five patients, the nonunion was malaligned
in excessive varus with an average medial proximal tibial angle of
75° (range, 70° -83°) and ended treatment with an average
medial proximal tibial angle of 91° (range, 89°-93°).
In one patient, the nonunion was malaligned in excessive valgus with
a medial proximal tibial angle of 103° and ended treatment with
a medial proximal tibial angle of 93°. The normal range of the
medial proximal tibial angle is 85° to 90°. The average preoperative
and postoperative posterior proximal tibial angle was 89.5° and
84° respectively, indicating a correction of procurvatum deformity.
The normal range of posterior proximal tibial angle is 77° to
Insall-Salvati ratio increased from 1.1 to 1.2 (p = 0.057) and remained
within normal limits. The average percent increase in metaphyseal
bone stock of the proximal tibia was 43% (range, 23%-63%) (p = 0.00061).
The average preoperative Hospital for Special Surgery knee score in
four patients was 42 (range, 39-44). This improved to an average postoperative
Hospital for Special Surgery knee score of 89 (range, 80-98) (p=0.00038).
The Hospital for Special Surgery knee score was not available in one
patient. All patients stated that they were satisfied with the procedure
and would do it again. After an average followup of 4 years (range,
2 - 6 years), no patient had undergone total knee replacement, nor
was total knee replacement planned for any of the patients.
Two patients had superficial pin tract infection develop that responded
to oral antibiotics. One patient with pseudogout had a knee effusion
develop 1 month after the application of the Orthofix external fixation
device. The synovial cell count was 15,000 leukocytes and was positive
for birefringent crystals. Synovial fluid cultures were negative for
bacterial growth. The patient had an arthroscopic lavage. During this
procedure there was a question of arthroscopic fluid egress through
one of the proximal pin sites. For this reason, this proximal pin
was removed and another one was inserted more distally. The remainder
of the time in external fixation was without incident.
One patient had a change in the mechanical axis deviation and anatomic
femorotibial angle with time. The mechanical axis deviation progressed
from 3.3cm medial to 5.0cm medial and the anatomic femorotibial angle
changed from 4° varus to 9° varus during a period of 2 years.
The medial proximal tibial angle did not change, and the joint line
obliquity angle changed from 0° to 4° varus (This progression
of deformity does not reflect a change in the tibial deformity but
rather progressive loss of medial compartment cartilage).
Associated factors included posterior horn medial meniscus tears in
two patients diagnosed and treated with previous arthroscopy. One
patient had had a knee arthrotomy 22 years before the high tibial
osteotomy. Three of the five patients had noninsulin dependent diabetes
This study suggests that nonunion after high tibial osteotomy associated
with deformity and shortening can be treated successfully with distraction
osteogenesis. This treatment modality has several advantages over
previous treatment modalities. Distraction osteogenesis using the
Ilizarov method is a percutanous procedure with minimal blood loss.
Nonunion takedown and hardware removal are not necessary. Distraction
of the nonunion accomplishes simultaneous bony healing, correction
of deformity, and lengthening.
The classic approach to nonunion surgery placed great emphasis on
compression forces and rigid stabilization with plates or external
fixation to achieve union.7,14,22
Catagni et al3
published the first reported series of patients in whom distraction
osteogenesis was the mode of treatment for hypertrophic nonunions.
They reported 21 hypertrophic nonunions after trauma treated with
distraction using the Ilizarov apparatus. Stable union was achieved
in all their patients. Angular, axial, and translational deformities
were corrected in all of their patients. Leg length discrepancy was
corrected in 86% of their patients.
Saleh and Royston23
presented a series of 10 hypertrophic nonunions after trauma in which
bony alignment and length were restored and union induced by external
fixation and callus distraction. The mean length increase was 3.5cm
and the mean angular correction was 13.5°. There were no refractures
or loss of correction or length.
Paley et al18
included three cases of distraction of hypertrophic nonunions among
25 cases of tibial nonunions with bone loss. In another report, Paley
et al19 included
three cases of distraction of hypertrophic nonunions among 29 cases
of malunions and nonunions of the femur and tibia. They characterized
nonunions into stiff, partially mobile, and flail types. This technique
was not recommended for flail nonunions which are usually atrophic
and have greater than 20° mobility. Partially mobile nonunions
have 5° to 20° mobility predominantly in one plane with a
solid end point to manual stress and usually with some fixed deformity.
These were treated with distraction after an initial period of compression.
They recommended initial compression of 0.5 to 1.0mm per day for 2
weeks to stimulate osteogenesis followed by gradual distraction. They
used compression combined with intermittent distraction at the same
rate to stimulate bony consolidation. Stiff nonunions have less than
5° motion and were treated with distraction of the nonunion site
at 1.0mm per day. The stiffness of a nonunion is an indirect reflection
of the type of tissue between the ununited bone ends. Stiff nonunions
have dense fibrocartilaginous tissue. Distraction of this tissue leads
to new bone formation with the nonunion site acting as the fibrous
These studies revealed successful treatment of hypertrophic nonunions
with distraction after trauma. Hypertrophic changes at a nonunion
site show that callus-forming capacity and biologic healing potential
are present. What is required in such cases is appropriate manipulation
of the mechanical environment to induce the callus to mature and remodel.
Reduction or abolition of shear forces, rather than compression, is
needed for successful healing. This can be achieved with mechanically
stable external fixation and bony realignment. Linear distraction
can be continued to correct shortening and angular distraction may
be used to correct angular deformity.23
Distraction treatment of hypertrophic nonunions offers a unique opportunity
to observe the capacity for bone formation within the nonunion. Additional
treatment then can be based on whether bone formation is observed.
The appearance of callus confirms the bone healing capacity of the
hypertrophic nonunion (Fig 3). Absence of callus
formation suggests the need for bone grafting.
The broad surface area and adequate blood supply of the upper tibia
provide favorable conditions for healing, and nonunion is uncommon.26
Tjornstrand et al26
presented the first series of nonunions after high tibial osteotomy.
They advocated open resection of the pseudoarthrosis, bone grafting,
Charnley transfixation compression and casting. Schatzker et al24
reported three cases of nonunion where they did not resect the pseudarthrosis
but did perform open bone grafting and applied a transfixation external
fixator in compression. Wolff and Krackow28
reported the results of internal fixation in the treatment of six
cases of nonunion after proximal tibial osteotomy. They advised against
resection of the pseudarthrosis site in order to preserve metaphyseal
bone for future total knee replacement, and they routinely performed
open bone grafting. Cameron et al2
advocated the use of double plates bolted together. Limb alignment
and leg length discrepancy were not emphasized in these studies.
Results of total knee replacement in patients after previous high
tibial osteotomy have been reported to be less favorable than in patients
who did not undergo osteotomy.13,15,16,27
This has been related to previous skin incisions, patella baja, and
bony considerations. Patella baja can lead to difficult soft tissue
exposure and patellar eversion during total knee replacement. This
could lead to the need for quadricepsplasty during total knee replacement.
Multiple skin incisions can compromise skin vascularity and the soft
tissue envelope of the knee. Bony abnormalities present after high
tibial osteotomy may significantly reduce the bone available for resection
during total knee replacement.
In none of the reports on nonunion after high tibial osteotomy, have
the authors improved or even measured metaphyseal bone stock and patella
baja. An increase in metaphyseal bone stock, and an improvement of
patella baja by the Insall-Salvati ratio11
was seen in the current study. Insall-Salvati ratio11
increased but remained within normal limits in all patients in the
current study. In four of the five patients, no additional incisions
were made that would interfere with future arthroplasty. Retained
hardware was observed to deform as the bony deformity corrected (Fig
4). In one patient, percutaneous screw removal was performed.
Routine hardware removal is not necessary. It is important to avoid
contact between the external fixation pins and wires and the internal
hardware to prevent deep infection. Although there is a theoretical
increased risk of infection of total knee replacement in a knee that
previously had an external fixator, the authors are unaware of any
studies that would support this theory.
Another concern is septic knee arthritis from intraarticular placement
This is especially true in patients where in whom the proximal nonunion
fragment is small. DeCoster et al5
identified four zones of the knee. The capsule inserts 4 to 14mm below
the articular surface in a regular pattern. The anterior half of the
circumference is close to the joint line (less than 6mm). They recommended
placement of wires and pins greater than 14mm from the subchondral
line. If wire placement is needed closer to the joint, this can be
done safely in the anterior half at least 6mm from the subchondral
line. In the experience of the current authors, the incidence of knee
sepsis after proximal tibia external fixation is rare in reconstructive
cases. Even in situations of intrarticular wire placement, the synovium
seals off rapidly creating a barrier to the knee. In acute trauma,
where soft tissue injury and swelling are present, this mechanism
may be less effective. Superficial pin tract infections are common
and were seen in 2 of 5 patients in the current series. Patients were
given an oral antibiotic prescription and instructed to take a one
week dose if a pin infection developed. Patients were educated about
recognizing a pin infection in order to avoid delay in treatment.
The issues that require consideration in the treatment of these nonunions
are bony union, axial alignment, leg length discrepancy, and future
total knee replacement. Bony union, restoration of normal axial alignment,
correction of leg length discrepancy, increase in metaphyseal bone
stock, improvement of patella baja, and improvement of functional
outcome as measured with the Hospital for Special Surgery knee score
were seen in all patients in the current study. At an average of 4
years followup, none of the patients has required total knee replacement.
Distraction osteogenesis in the treatment of nonunion with deformity
after high tibial osteotomy is a minimally invasive percutaneous procedure
with a successful clinical and radiographic outcome. The nonunion
site is not exposed surgically minimizing the risk of infection and
no bone graft is required eliminating donor site morbidity. Future
total knee replacement, if necessary, may be technically easier as
a result of this procedure.
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Legend of Figures
Fig 1. The
anatomic femorotibial angle change in five patients.
Fig 2. The
medial proximal tibial angle change in five patients.
radiograph showing proximal tibia nonunion with valgus deformity.
week followup showing correction of deformity and distraction osteogenesis
with Ilizarov frame.
followup (2 weeks after frame removal) showing bony union, correction
of deformity, and increased metaphyseal bone stock.
month postoperative radiograph showing bony remodeling of proximal
picture at twenty-eight months.
radiograph showing nonunion with varus deformity and retained hardware.
radiograph showing the application of an Orthofix monolateral frame.
month followup showing distraction osteogenesis and correction of
deformity. Deformation of the hardware and increased metaphyseal bone
stock are evident.
month followup showing bony union (day of frame removal).