Generic preoperative planning for proximal femoral osteotomy in the treatment of nonunion of the femoral neck

SUPPLEMENT ARTICLE
Generic Preoperative Planning for Proximal Femoral
Osteotomy in the Treatment of Nonunion of the Femoral
Neck
Keith Mayo, MD* and Djoldas Kuldjanov, MD†
Summary: Despite improvements in surgical technique and overall
patient care, failed treatment of fractures of the femoral neck persists.
For the physiologically young patient, joint preservation is the
preferred method of treatment. Unfortunately, the best treatment
option, proximal femoral osteotomy, is fast becoming a lost art.
Preoperative planning is critical in this regard. The described
preoperative planning work flow is a reliable method for obtaining
the desired deformity correction for a variety of proximal femoral
malunions and nonunion. Revisiting the classic Pauwels osteotomy
for femoral neck nonunion is an appropriate vehicle to supply the
first link in resurrecting this treatment modality by providing
a standardized preoperative planning protocol.
Key Words: femoral neck nonunion, proximal femoral osteotomy,
preoperative planning
(J Orthop Trauma 2018;32:S46–S54)
INTRODUCTION
Failed surgical treatment of proximal femur fractures
persists, despite improved understanding of local blood supply,
biomechanics, and an ever-increasing array of fracture im-
plants. When malunions and nonunion in this area occur in the
physiologically younger population, joint preservation remains
preferable to arthroplasty. Unfortunately, osteotomy techniques
for correction of deformity and repair of nonunion have not
been emphasized in many orthopaedic residency and fellow-
ship training programs. Therefore, it is timely and important to
revisit the classic Pauwels osteotomy1–3 for the treatment of
femoral neck nonunion. The first step in understanding this
essential treatment modality is to become skilled in using
a standardized preoperative planning protocol. Use of this pro-
tocol is critical for the success of the subsequent surgical
procedure.
PREOPERATIVE EVALUATION
Imaging
Adequate imaging should include at a minimum
a weight bearing anteroposterior (AP) pelvis in neutral hip
rotation (patellae facing directly anterior) and an AP and
lateral of the both the injured hip and contralateral normal hip.
If there are no distal deformities or contractures, the AP pelvis
radiograph will show pelvic obliquity approximately com-
mensurate with any leg length inequality. Alternatively,
a radiograph taken with a block equal to the amount of the
leg length inequality placed under the foot on the side of the
injured hip should produce a level pelvis.
The radiographic neck-shaft angle can vary significantly
from true centrum-collum-diaphyseal (CCD) angle based on
femoral torsion.4 Because this is an important planning variable,
the AP hip radiograph should be rotated to eliminate the distor-
tion caused by any femoral torsion and provide a true AP image
of the femoral neck. In most hips, this requires internal rotation
of the lower extremity. However, in a femur with minimal tor-
sion, this maneuver may not be necessary.
Other imaging modalities may be indicated based on the
clinical setting. Studies to evaluate femoral head viability, such
as magnetic resonance (MR) imaging, may be useful. Horizontal
plane deformity in the form of neck-shaft or neck-head
retroversion is best assessed by computed tomography or MR
imaging and may be an important factor in planning. Chronic
deformity or anatomic variants predating the index injury may
be associated with hip impingement and warrant MR imaging.
Physical Examination
A thorough multisystem examination is required with
special focus on hip motion, abductor motor function, and leg
length inequality. Asymmetric hip rotation is often a sign of
horizontal plane malalignment and should prompt additional
imaging, as noted above. Evidence of some abductor motor
weakness on physical examination is common in the post-
traumatic setting. However, profound deficits warrant further
neurologic assessment. Joint contracture in a hip with a congruent
joint and a normal joint space may warrant capsulorrhaphy and
arthrolysis performed concurrently with deformity correction.
GENERIC PREOPERATIVE PLANNING USING A
NORMAL-SIDE TEMPLATE
The recommended planning sequence is illustrated
using tracings from magnification-corrected image printout
Accepted for publication November 7, 2017.
From the *Hansjoerg Wyss Hip and Pelvis Center at Swedish Hospital Seattle,
WA; and †Department of Orthopaedic Surgery, Saint Louis University
School of Medicine, St. Louis, MO.
The authors report no conflict of interest.
Reprints: Keith Mayo, MD, Hansjoerg Wyss Hip and Pelvis Center at
Swedish Hospital, 600 Broadway Suite 340, Seattle, WA 98122 (e-mail:
mayok@earthlink.net).
Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
DOI: 10.1097/BOT.0000000000001087
S46 | www.jorthotrauma.com J Orthop Trauma Volume 32, Number 2 Supplement, February 2018
Copyright Ó 201 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.8

from a picture archive and communication system. This
exercise can be replicated with only minor modiﬁcations
in a completely computerized work ﬂow using virtually any
currently available preoperative planning software.
A 58-year-old female marathon runner sustained a min-
imally displaced right femoral neck stress fracture (Fig. 1A).
Eight months later, she remained painful in the groin with
weight bearing (Fig. 1B). Computed tomography obtained
at that time showed no evidence of fracture union. The
lateral radiograph in this case did not show any discernible
sagittal or horizontal plane deformities, which correlated
with the physical examination. Therefore, the preoperative
planning in this case was restricted to the coronal plane and
based on the AP imaging. As is often the situation, multiple
FIGURE 1. The postoperative AP hip
radiograph (A) after the initial sur-
gery for the index right femoral neck
fracture is shown. The radiograph
obtained 8 months later (B) shows
implant failure and a displaced
fracture.
FIGURE 2. The normal-side AP hip
radiograph (A) reversed and cor-
rected for rotation is used as a tem-
plate using a CCD angle of 135
degrees. The injured-side right hip
AP radiograph (B) is traced and the
altered CCD angle is drawn.
J Orthop Trauma Volume 32, Number 2 Supplement, February 2018 Generic Preoperative Planning for Proximal Femoral
Osteotomy
Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved. www.jorthotrauma.com | S47

broken retained implants provide an additional surgical
challenge.
Step 1
The normal-side (left) AP hip radiograph corrected
for rotation is reversed and traced for use as a template
using a CCD angle 135 degrees (Fig. 2A). The injured-side
right hip AP radiograph is traced and the altered CCD
angle, as measured at 110 degrees, is drawn (Fig. 2B).
The angle subtended by the nonunion and a horizontal ref-
erence line is 70 degrees. This angle described by Pauwels
has been used as correction guide dating to his original
work.1,2
Step 2
Next the tracing of the injured hip is placed over the
normal template and aligned based on available landmarks
(Fig. 3A). In this case, the lesser trochanter and diaphysis are
the primary alignment reference points. When the deformity
encompasses the trochanters, this overlay process is some-
what subjective, relying predominantly on the contour of
the femoral diaphysis and clinical or ancillary radiographic
FIGURE 3. The tracing of the
injured hip is placed over the normal
template and aligned based on
available landmarks (A) and a pri-
mary transverse osteotomy at the
intertrochanteric level (superior
aspect of the lesser trochanter) has
been selected for preliminary evalu-
ation (B).
FIGURE 4. Templates of a pure
opening wedge osteotomy (A),
a pure closing wedge osteotomy
(C), and a combination opening/
closing osteotomy (B) are shown.
Mayo and Kuldjanov J Orthop Trauma Volume 32, Number 2 Supplement, February 2018
S48 | www.jorthotrauma.com Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

FIGURE 5. A pure closing wedge
construct was selected for this
patient and templated (A). The
competed template is then overlaid
on an offset high-angled blade plate
template (B).
FIGURE 6. The seating chisel path is
transferred to the original deformity
drawing, which is then overlaid on
the ﬁnal construct drawing from Fig.
5B (A). The last step in the plan is
a summation drawing with all refer-
ence K-wires that will be used at
some stage in the case (B).
Osteotomy

clues for the assessment of limb length. The goals of this
overlay are to determine the frontal plane angular defor-
mity, as well as the limb length discrepancy and any hip
offset abnormality. In this case, the measured frontal plane
deformity is 25 degrees based on the angle formed by the
respective neck axes (Fig. 3A), which should match the
simple subtraction result of normal CCD—deformity
CCD (Figs. 2A, B). Shortening measures nearly 2 cm and
fortunately, despite varus collapse, total offset is not
diminished.
In general, the proximal and distal segments of the
malunion/nonunion outline are provisionally selected on
the basis of correction versatility and healing time with
a goal of minimizing secondary deformity. Here, a primary
transverse osteotomy at the intertrochanteric level (superior
aspect of the lesser trochanter) is selected for preliminary
evaluation (Fig. 3B). This configuration is the easiest to
plan and execute and allows rotational correction before
any type of closing wedge ostectomy from the distal seg-
ment. Bone healing is relatively rapid at this level (6–8
weeks in most cases), and there is modest alteration of
the native anatomy. While this initial planning step is the
most straightforward, it is important to recognize that there
are many configurations possible and multiple plans may
need to be generated before a final selection is made.
Step 3
The degree of frontal plane correction in the setting
of femoral neck nonunion is based on the goal of
generating compression across a nonunion plane previ-
ously dominated by shear forces.1,2 Initial guidelines called
for limiting the nonunion (Pauwels) angle relative to the
horizontal to 25 degrees or less. Because most nonunions
occur in Pauwels type III fractures, achieving this goal
results in a high CCD angle in many patients, and this type
of anatomic alteration (coxa valga) has been associated
with increased risk for hip and knee arthritis.5,6 However,
this 25-degree figure persists in the literature.7,8 Therefore,
it is important to be knowledgeable regarding the internal
fixation limitations in the Pauwels era. Many of Pauwels
osteotomies were stabilized with tension band wires alone.
Routine use of the angled blade plate, first widely reported
by Marti et al,9 has allowed modification of the correction
goals to limit increases in resultant CCD without compro-
mising healing of the nonunion. Against this backdrop, the
decision was made in this case to perform a frontal plane
valgus osteotomy of 30 degrees, which takes into account
a small increase beyond the 25 degrees needed to replicate
the contralateral CCD angle. The resultant CCD angle
on the operated side will be 140 degrees. In the authors’
experience, it is rarely indicated to exceed this degree of
valgus.
The decision-making regarding an opening wedge
osteotomy versus a closing wedge or a combination thereof
is based on leg length and bony stability considerations. A
pure opening wedge (Fig. 4A) gains the most length but is
the least stable because of the limited initial bony contact
and potential compromise in tensioning of the plate. Bone
grafting will only partially mitigate these shortcomings.
Although an opening wedge osteotomy can be a relatively
safe technique in children and adolescents, as used for
other indications, it is rarely used in adults. A pure closing
wedge osteotomy (Fig. 4C) compromises length restoration
but provides the most stable construct secondary to bone-
on-bone contact area and plate loading. A combined medial
opening/lateral closing wedge technique (Fig. 4B) is a scal-
able intermediate useful in many patients. Lateral shaft
displacement denoted by arrows parallel to the primary
osteotomy plane (Figs. 4B, C) represents another variable
in correction. In closing wedge valgus osteotomies, it can
provide an additional lengthening tool. However, distorting
the relationship between the greater trochanter/metaphysis
FIGURE 7. Illustration of offset or “mismatch” tensioning of
the plate to effect compression at the osteotomy site.

and the femoral canal can make a subsequent salvage hip
arthroplasty difficult and should be undertaken cautiously.
Correction of acquired (posttraumatic) varus to near normal
alignment should have a positive effect on limb mechanical
axis. Therefore, the risk for knee arthritis is likely only in
instances of excessive CCD angles, as noted above.
Step 4
A pure closing wedge construct (Fig. 5A) was selected
for this patient. Stability and bony healing time were believed
to be paramount considerations in this relatively older patient.
The compromise was accepting the ability to achieve only
50% of the optimum lengthening. Once the final osteotomy
FIGURE 8. The final result (A)
should match the preoperative plan
(B).
FIGURE 9. AP (A) and lateral (B) hip
radiographs of a femoral fracture
treated with a sliding hip screw
show lag screw cut out and fixation
failure 3 months postoperatively.
Osteotomy

configuration template is completed, it is overlaid on an offset
high-angled blade plate template (Fig. 5B). The blade angu-
lations available are 110, 120 and 130 degrees. The easiest
technique and best fit in this case will use a 120 degrees plate.
If our planning is correct, insertion of the blade seating chisel
orthogonal to diaphyseal axis will result in a 30-degree frontal
plane correction as the side plate is applied to the shaft. In the
event of sagittal plane deformity (flexion or extension), com-
pensatory seating chisel adjustments must be made for the
subsequent blade plate placement. These adjustments may
create an anterior or posterior gap at the osteotomy interface,
which can be managed with a small closing wedge ostectomy
from the proximal segment or more simply by filling it will
morselized graft from the primary closing wedge.
Step 5
Next, the seating chisel path is transferred to the
original deformity drawing, which is overlaid on the final
FIGURE 10. Summation (A) and
final result (B) tempating are shown.
FIGURE 11. AP (A) and lateral (B)
hip radiographs showing the clinical
result at 1 week postoperatively.

construct drawing from Figure 5B (Fig. 6A). This path should
be orthogonal to the long axis as discussed previously. The
last step in the plan is a summation drawing with all reference
K-wires that will be used at some stage in the case (Fig. 6B).
From distal to proximal, these K-wires are orthogonal to the
diaphysis, proximal and distal components of the closing
wedge, seating chisel reference, and trochanteric tip. Distan-
ces from the seating chisel reference to the trochanteric tip
and transverse intertrochanteric osteotomy plane are mea-
sured. The closing wedge osteotomy reference wires will
interfere with seating chisel placement and are placed only
after seating chisel insertion has been completed. It may be
useful to use these K-wires as “cutting guides” for the sur-
geon who is inexperienced in this procedure.
Step 6
Plan execution requires familiarity with the blade plate
instrumentation and the ability to generate osteotomy site
compression (Fig. 7). This offset or “mismatch” tensioning of
the plate is used with high-angle blade plates for which an
articulated tensioner is poorly suited. The plate is attached
distally with a single screw after abutting the lateral osteot-
omy surface but leaving a modest (approximately 5–6 mm)
gap between the proximal lateral cortex and the side plate. A
plate lag screw is then placed proximally in the first or second
hole in the plate. As this screw is tightened, the femoral shaft
is lateralized and compression is generated progressively
from medial to lateral at the osteotomy site. If the bone den-
sity is questionable, it is wise to use 2 proximal screws, which
are alternately tightened, to minimize the risk of screw pull
out. When the plan is well executed, the final result should
match the preoperative plan (Figs. 8A, B).
CLINICAL CASE
A sliding hip screw was used for fixation of a femoral
neck fracture in a 42-year-old man. Lag screw cut out and
fixation failure was noted at 3 months postoperatively (Figs. 9A,
B). The plan in this case was determined to require a 110-degree
blade plate inserted off the orthogonal shaft axis to gain fixation
in the inferior femoral head below the defect cause by the pre-
vious implant (Figs. 10A, B). In this patient, the proximal hip
screw channel was to be filled with allograft as well (Fig. 10B).
Because of instability noted at the time of surgery, a lag screw
was placed above the blade path (Fig. 11A). Despite an initial
Pauwels angle of 80 degrees, the planned frontal plane correc-
tion was only 30 degrees, resulting in a new CCD angle of 135
degrees (Figs. 10B and 11A, B). Uneventful union occurred of
both the femoral nonunion and osteotomy site, further illustrat-
ing the point that historically described large corrections are
rarely, if ever, needed (Figs. 12A, B).
CONCLUSION
The above preoperative planning work flow has proven
a reliable method for obtaining desired deformity corrections for
a variety of proximal femoral malunion and nonunions. It is
easily adapted to both old style hard copy radiograph or digital/
picture archive and communication system environments.
REFERENCES
1. Pauwels F. Der schenkelhalsbruch ein mechanisches problem: Grundla-
gen des Heilungsvorganges Prognose und kausale Therapie. Stuttgart,
Germany: Ferdinand Enke Verlag; 1935.
2. Pauwels F. Biomechanics of the Normal and Diseased Hip. Berlin, Ger-
many: Springer-Verlag; 1976.
3. Weber BG, Cech O. Pseudarthrosen: Pathophysiologie, Biomechanik,
Therapie, Ergebnisse. Bern, Switzerland: Verlag Hans Huber; 1973.
FIGURE 12. AP (A) and lateral (B)
hip radiographs showing union of
both the femoral nonunion and os-
teotomy site.
Osteotomy

4. Kay RM, Jaki KA, Skaggs DL. The effect of femoral rotation on projected
femoral neck shaft angle. J Pediatr Orthop. 2000;20:736–739.
5. Benlidayi C, Guzel R, Basaran S. Is coxa valga a predictor of knee oste-
oarthritis? A cross-sectional study. Surg Radiol Anat. 2014;37:359–366.
6. Pedoia V, Samaan M, Souza R. Study of the interactions between prox-
imal femur 3D bone shape, cartilage health and biomechanics in patients
with hip osteoarthritis. J Orthop Res. 2017 [epub ahead of print].
7. Magu NK, Rohilla R, Singh R, et al. Modiﬁed Pauwels’ intertrochanter-
icosteotomy in neglected femoral neck fracture. Clin Orthop Relat Res.
2009;467:1064–1073.
8. Anglen JO. Intertrochanteric osteotomy for failed internal ﬁxation of fem-
oral neck fracture. Clin Orthop Relat Res. 1997;341:175–182.
9. Marti RK, Schuller HM, Raaymakers EL. Intertrochanteric osteotomy for
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