While under general anesthesia, the patient is positioned either prone on a
specialized fracture table or laterally on a radiolucent operating table with
a beanbag used for support. With the patient prone on the fracture table, the
sterile field consists of the buttock and the posterior and lateral aspects of
the thigh (Fig. 1). With the
patient in the lateral position and the limb draped free, the sterile field is
similar to that in hip arthroplasty surgery, but it extends posteriorly to
include the region of the posterior superior iliac spine
(Fig. 2). For either position,
a radiolucent operating table is used along with intraoperative c-arm
fluoroscopy to assess fracture reduction and hardware location. Routinely, our
preference is to isolate the surgical field using an iodophor-impregnated
adhesive plastic skin drape, as illustrated in the figures.
We prefer the Kocher-Langenbeck posterior approach for routine posterior
wall fractures of the acetabulum (Figs. 3-A
through
3-E)5.
However, a modification of the Gibson posterolateral approach can be used to
allow better access to a superior (weight-bearing-dome) fracture fragment or
to avoid an incision through an area of injured posterior soft tissue
(Figs. 4-A and
4-B)6.
To minimize the risk of iatrogenic sciatic nerve injury, flexion of the
ipsilateral knee is maintained throughout the operative procedure to place the
nerve in a relaxed position.
For the Kocher-Langenbeck approach, the skin incision
(Fig. 3-A) is centered over the
greater trochanter. The proximal branch of the incision is directed toward the
posterior superior iliac spine, ending approximately 6 cm short of this
osseous landmark. Distally, the incision extends approximately 15 cm along the
midlateral aspect of the thigh. This skin incision is carried through the
subcutaneous tissue and superficial fascia onto the fascia lata (the
iliotibial tract) and the thin, deep fascia overlying the gluteus maximus
muscle (Fig. 3-B). The fascia
lata is then divided in line with the skin incision, beginning at the distal
aspect of the wound, continuing proximally toward the greater trochanter, and
ending at the first sighting of the gluteus maximus muscle fibers as they
insert into the iliotibial tract.
The next step is the splitting of the gluteus maximus muscle. Despite
possessing a dual blood supply and thus having the potential for an
intervascular plane of dissection, the gluteus maximus muscle has innervation
only from the inferior gluteal nerve. Consequently, there is no internervous
plane, and the nerve branches of the upper one-third of the muscle cross the
intended interval of dissection slightly more than halfway between the level
of the greater trochanter and the posterior superior iliac spine. Therefore,
splitting of the muscle fibers should stop as soon as the first nerve branch
to the upper part of the muscle is encountered
(Fig. 3-C). Following release
of the gluteus maximus insertion into the femur, which allows adequate
posteromedial retraction of the large mass of the gluteus maximus muscle
without undue stretch of the inferior gluteal nerve, the sciatic nerve is
located along the posterior surface of the quadratus femoris muscle
(Fig. 3-C). Next, the
piriformis and obturator internus tendons (with the superior and inferior
gemelli muscles on either side) are incised approximately 1.5 cm from their
insertion points into the greater trochanter; it is important to preserve this
distance from the insertion site in order to avoid injury to the blood supply
of the femoral head. After reflection of these short external rotator muscles
and elevation of the gluteus medius and minimus muscle origins from the
external surface of the ilium, exposure of the posterior acetabulum and the
retroacetabular space is essentially complete
(Fig. 3-D). A specially
designed sciatic nerve retractor can be conveniently placed into the lesser
sciatic notch in front of the tendon of the obturator internus to facilitate
exposure of the posterior column (Fig.
3-E). A blunt Hohmann retractor can be used for this purpose as a
less desirable alternative.
For the modified Gibson approach, the skin incision begins at a point
approximately 8 cm anterior to the posterior superior iliac spine at the level
of the iliac crest, extending distally to the greater trochanter and then
midlaterally in line with the femur for approximately 15 cm
(Fig. 4-A). Beginning distally
and extending to the level of the greater trochanter, the iliotibial band is
incised in line with the skin incision. Next, the interval between the tensor
fasciae latae and gluteus maximus muscles is identified and developed from the
level of the greater trochanter proximally to the iliac crest
(Fig. 4-B). The entire gluteus
maximus muscle can now be reflected posteriorly on its neurovascular pedicle.
The remainder of the deep dissection is similar to that of the
Kocher-Langenbeck approach.
After completion of the surgical approach, the next step is to define all
of the fracture fragments. Usually resulting from high-energy trauma such as
motor-vehicle crashes, fractures of the posterior wall are often comminuted,
with marginally impacted and free osteochondral fragments in addition to
multiple wall pieces still maintaining soft-tissue attachments
(Fig.
5)2. In
order to maximize the restoration of clinical hip function, great effort must
be made to return all of these fragments to their anatomical positions. The
wall fragments are cleared of debris and reflected on their capsular
soft-tissue attachments, which are carefully preserved, to reveal the
posterior column with its remaining articular surface. The hip must then be
subluxated to allow inspection of the joint for removal of osteochondral free
fragments, to define the extent of marginal impaction, and to allow for joint
irrigation and débridement (Fig.
6-A). To accomplish these tasks, traction is applied to the hip
with the aid of muscle paralysis. Traction may be applied with use of the
fracture table with the patient in the prone position or manually through a
5-mm or 6-mm Schanz screw placed in the greater trochanter with the patient
positioned laterally (Fig.
6-B). After the joint has been cleared of debris, including any
remaining ligamentum teres, the marginally impacted and free fragments are
keyed into position, often with the reduced femoral head used as a template.
The elevated, marginally impacted fragments leave an underlying void resulting
from the impacted cancellous bone, in a situation analogous to a depressed
tibial plateau fracture. Similarly, this void must be filled. Many bone-void
fillers, including local autologous bone from the greater trochanter as well
as assorted synthetic materials, have been
recommended7,8.
However, we prefer freeze-dried cancellous allograft bone
(Fig. 6-C). Osteochondral free
fragments must be assessed for the amount of attached cancellous bone
remaining; free fragments devoid of any cancellous bone have a limited chance
of successful healing. Therefore, although every attempt should be made to
replace all fragments, often, especially in elderly patients, this objective
cannot be achieved.
It is frequently difficult to maintain marginally impacted and
osteochondral free fragments in their elevated and reduced positions.
Therefore, we recommend stabilizing these fragments with subchondral 2.0-mm
mini-screws or 1.5-mm bioabsorbable pegs (Figs.
6-D and
7-A through
8-F)2,3,9.
Although many manufacturers produce these items, we have developed certain
preferences and techniques that have been successful in our hands. Miniscrews
with a smaller, flatter cruciate head (such as those from Synthes, Paoli,
Pennsylvania) are preferred, as it is much easier to countersink these screw
heads below the cancellous bone surface
(Fig. 9). We have found the
most common mini-screw and bioabsorbable peg length to be 40 mm. Therefore,
screws of 40 to 50 mm in length (which usually are not part of standard
mini-screw fracture-fixation sets) should be available in the operating room.
Considering the depth of the wound in these patients, insertion of the 2.0-mm
mini-screws, as well as the 1.5-mm bioabsorbable pegs, is facilitated by using
a standard 1.6-mm smooth Kirschner wire (rather than a small drill-bit) to
create the pilot hole. Overdrilling to create a gliding hole for these fully
threaded screws is not required. After reduction, fixation, and grafting of
these fragments, the hip is again subluxated to evaluate the quality of the
intra-articular reduction.
The posterior wall fragments with their intact capsular attachments are
then sequentially reduced and held with a pointed ball spike
(Fig. 10-A). Since the
articular surface can no longer be seen, the accuracy of the reduction of the
articular surface is extrapolated from the reduction of the acetabular rim and
that of the extra-articular cortical fracture lines. The inability to achieve
an anatomic reduction of the posterior wall fragments is indicative of
intra-articular incongruity, which is most likely due to incompletely reduced,
or shifting of previously reduced, free and impacted fragments. Although
Kirschner wires may be used to temporarily hold the reduced posterior wall
fragments, we have found that smooth Kirschner wires are unreliable for either
temporary or permanent fixation of these fragments. Therefore, we fix
posterior wall fragments using at least one screw while maintaining the
reduction with the ball spike (Figs. 10-B
and 10-C). After this reduction and fixation is completed, the hip
is inspected in all planes with c-arm fluoroscopy to ensure that the hardware
has not penetrated the joint surface
(Figs. 11-A through
11-D)10.
Screws that appear to compromise the subchondral bone on tangential or axial
views should be
redirected10. The
entire construct is then further supported with 3.5-mm buttress-plating; this
is accomplished with use of a reconstruction plate, which is supplemented by a
one-third tubular spring
plate11 in selected
fractures with extensive comminution of the posterior wall (Figs.
8-D, 8-E, 8-F, and
12-A through 12-E). Buttress
plates are placed as close to the acetabular rim as possible. In addition,
each posterior wall fragment should be held by at least one lag screw placed
along the acetabular rim. These rim screws can be inserted before or after
buttress-plate application. Then, after the removal of any remaining
provisional fixation, the hip is again inspected in all planes with c-arm
fluoroscopy to assess fracture reduction and hardware placement. This method
of definitive fixation of the marginally impacted and osteochondral free
fragments followed by screw and plate fixation of the overlying posterior wall
fragments (termed two-level fracture fixation) has proved successful
in the treatment of the most comminuted of posterior wall
fractures9.
The wound is then closed in layers over suction drains. Before the patient
is discharged from the hospital, three standard radiographs of the pelvis
(anteroposterior, internal oblique, and external oblique) and a
two-dimensional computed tomography scan are made to assess fracture
reduction. Nonweight-bearing or toe-touch weight-bearing (20 to 30 lb [9 to 14
kg]), with crutches or a walker, is maintained for ten to twelve weeks. There
is no range of motion restriction. Progression to full weight-bearing should
be individualized on the basis of the appearance of the follow-up radiographs.
Physical therapy is continued until muscle strength and range of motion are
regained.
CRITICAL CONCEPTSINDICATIONS:The main indication for open reduction and internal fixation of a posterior
wall fracture of the acetabulum is hip instability, which can be identified in
several ways. Patients presenting with a hip dislocation should be treated
with emergent reduction of the dislocation. Patients exhibiting gross
instability on physical examination after closed reduction, defined as joint
instability occurring at =40° of hip
flexion12, are
treated operatively. After a successful closed reduction, as documented by
plain radiography, the hip is further evaluated by two-dimensional computed
tomography. If this modality shows the fracture to involve >50% of the
posterior wall, it can be considered
unstable7,13-15.
All other posterior wall fractures, including those that are not associated
with a known hip dislocation, should be considered potentially unstable. In
these cases, a dynamic fluoroscopic stress examination of the hip should be
performed with the patient under general anesthesia to identify instability
requiring surgical
treatment2,3.
Loss of joint congruency, evidenced by posterior subluxation of the femoral
head, is considered to be diagnostic of hip instability. For this stress
examination, the patient is placed supine with the hip in neutral rotation and
full extension. The hip is then progressively flexed to >90° while
manual force is applied through the hip along the longitudinal axis of the
femur; simultaneously, fluoroscopic imaging of the hip in the anteroposterior
and obturator oblique projections is performed
(Figs. 11-A and 11-B). If the
hip appears stable on this assessment, the examination is repeated with the
addition of slight adduction and internal rotation (approximately
20°)7,15.Other indications for operative repair include a hip fracture-dislocation
that is not reducible by closed means, the presence of incarcerated fragments
that prevent congruent reduction, or the presence of an ipsilateral femoral
neck fracture.CONTRAINDICATIONS:Nonoperative treatment of an unstable posterior wall fracture is
inconsistent with the recovery of normal, satisfactory hip function.
Therefore, absolute contraindications to this approach are limited to those
patients whose medical conditions preclude general or regional anesthesia.
Relative contraindications consist of patient situations that might be, in the
treating surgeon's opinion, better served by total hip arthroplasty. These
circumstances include preexisting arthritis, severely comminuted fractures in
elderly patients, and osteopenia precluding adequate fracture fixation.PITFALLS:Nerve injury is a serious complication of this procedure, and three nerves
in particular are at risk. For the Kocher-Langenbeck approach, it is important
not to split the gluteus maximus muscle proximally beyond the first branch of
the inferior gluteal nerve to the upper part of the muscle. Excessive traction
on the superior gluteal nerve after elevation of the gluteus medius and
minimus muscles from the external surface of the ilium can result in
neurapraxic injury and abductor weakness. The sciatic nerve (especially its
peroneal division) is at risk during the entire surgical procedure. Great care
must be taken to eliminate tension on the nerve by maintaining the knee in
flexion throughout the procedure. There are multiple variations in sciatic
nerve anatomy at this level; therefore, the nerve must be identified initially
overlying the quadratus femoris muscle and traced proximally to the greater
sciatic notch. The nerve is unprotected by intervening soft tissue both above
and below the obturator internus tendon with its attached gemelli muscles;
retractors in these regions place the nerve at risk and should be used with
caution (Fig. 3-D).Hardware must be placed in close proximity to the joint surface in order to
obtain stable fixation. C-arm fluoroscopy should be used as described to
evaluate hardware position (Figs. 11-A
through 11-D). Any hardware found to be too close to the joint
surface should be repositioned. Spring plates create a special risk of
intra-articular compromise of the joint surface. If the "hooks" of
the plate are too long or malpositioned, the femoral head may be at risk
(Figs. 12-A through 12-E).Posterior wall fractures consisting of one large fragment may be stabilized
satisfactorily with use of screws alone. However, the more conservative course
of action is always to supplement screw fixation with a buttress plate.
Fixation with use of screws alone is not indicated in comminuted
fractures.AUTHOR UPDATE:Since the time-period when the patients in the original article were
treated, we have increased our use of the modified Gibson surgical approach.
This approach offers an increase in superior and anterior surgical access.
Therefore, we have found it to be especially helpful for fractures of the
posterosuperior aspect of the acetabular wall, obviating the need for
trochanteric osteotomy to gain further exposure.
CRITICAL CONCEPTS
INDICATIONS:
The main indication for open reduction and internal fixation of a posterior
wall fracture of the acetabulum is hip instability, which can be identified in
several ways. Patients presenting with a hip dislocation should be treated
with emergent reduction of the dislocation. Patients exhibiting gross
instability on physical examination after closed reduction, defined as joint
instability occurring at =40° of hip
flexion12, are
treated operatively. After a successful closed reduction, as documented by
plain radiography, the hip is further evaluated by two-dimensional computed
tomography. If this modality shows the fracture to involve >50% of the
posterior wall, it can be considered
unstable7,13-15.
All other posterior wall fractures, including those that are not associated
with a known hip dislocation, should be considered potentially unstable. In
these cases, a dynamic fluoroscopic stress examination of the hip should be
performed with the patient under general anesthesia to identify instability
requiring surgical
treatment2,3.
Loss of joint congruency, evidenced by posterior subluxation of the femoral
head, is considered to be diagnostic of hip instability. For this stress
examination, the patient is placed supine with the hip in neutral rotation and
full extension. The hip is then progressively flexed to >90° while
manual force is applied through the hip along the longitudinal axis of the
femur; simultaneously, fluoroscopic imaging of the hip in the anteroposterior
and obturator oblique projections is performed
(Figs. 11-A and 11-B). If the
hip appears stable on this assessment, the examination is repeated with the
addition of slight adduction and internal rotation (approximately
20°)7,15.
Other indications for operative repair include a hip fracture-dislocation
that is not reducible by closed means, the presence of incarcerated fragments
that prevent congruent reduction, or the presence of an ipsilateral femoral
neck fracture.
CONTRAINDICATIONS:
Nonoperative treatment of an unstable posterior wall fracture is
inconsistent with the recovery of normal, satisfactory hip function.
Therefore, absolute contraindications to this approach are limited to those
patients whose medical conditions preclude general or regional anesthesia.
Relative contraindications consist of patient situations that might be, in the
treating surgeon's opinion, better served by total hip arthroplasty. These
circumstances include preexisting arthritis, severely comminuted fractures in
elderly patients, and osteopenia precluding adequate fracture fixation.
PITFALLS:
Nerve injury is a serious complication of this procedure, and three nerves
in particular are at risk. For the Kocher-Langenbeck approach, it is important
not to split the gluteus maximus muscle proximally beyond the first branch of
the inferior gluteal nerve to the upper part of the muscle. Excessive traction
on the superior gluteal nerve after elevation of the gluteus medius and
minimus muscles from the external surface of the ilium can result in
neurapraxic injury and abductor weakness. The sciatic nerve (especially its
peroneal division) is at risk during the entire surgical procedure. Great care
must be taken to eliminate tension on the nerve by maintaining the knee in
flexion throughout the procedure. There are multiple variations in sciatic
nerve anatomy at this level; therefore, the nerve must be identified initially
overlying the quadratus femoris muscle and traced proximally to the greater
sciatic notch. The nerve is unprotected by intervening soft tissue both above
and below the obturator internus tendon with its attached gemelli muscles;
retractors in these regions place the nerve at risk and should be used with
caution (Fig. 3-D).
Hardware must be placed in close proximity to the joint surface in order to
obtain stable fixation. C-arm fluoroscopy should be used as described to
evaluate hardware position (Figs. 11-A
through 11-D). Any hardware found to be too close to the joint
surface should be repositioned. Spring plates create a special risk of
intra-articular compromise of the joint surface. If the "hooks" of
the plate are too long or malpositioned, the femoral head may be at risk
(Figs. 12-A through 12-E).
Posterior wall fractures consisting of one large fragment may be stabilized
satisfactorily with use of screws alone. However, the more conservative course
of action is always to supplement screw fixation with a buttress plate.
Fixation with use of screws alone is not indicated in comminuted
fractures.
AUTHOR UPDATE:
Since the time-period when the patients in the original article were
treated, we have increased our use of the modified Gibson surgical approach.
This approach offers an increase in superior and anterior surgical access.
Therefore, we have found it to be especially helpful for fractures of the
posterosuperior aspect of the acetabular wall, obviating the need for
trochanteric osteotomy to gain further exposure.