Preoperative Radiographic Evaluation
Weight-bearing anteroposterior, lateral, and sunrise radiographs of the
knee should be assessed for overall coronal alignment in conjunction with an
anteroposterior radiograph of the pelvis. The valgus knee has been classified
into three types. A type-I deformity has minimal valgus and medial soft-tissue
stretching. A typical type-II fixed valgus deformity has a more substantial
deformity (>10°) with medial soft-tissue stretching, as shown in
Figures 1 and
2, and shall be the focus of
this technique guide. A type-III deformity is a severe osseous deformity after
a prior osteotomy with an incompetent medial soft-tissue sleeve, which is best
managed with a constrained or hinged total-knee design.
Attention should always be focused on both the osseous and soft-tissue
deformities. One should be aware of distal femoral hypoplasia, posterior
femoral condylar erosion, unusual proximal femoral neck-shaft angles, and
metaphyseal remodeling of both the femur and the tibia, which can lead to
malalignment or malrotation of the femoral component. Full-length standing
radiographs of the lower extremity can help to avoid these problems.
Fixed flexion contractures and the amount of medial joint-space opening may
influence the amount of osseous resection necessary to correct the deformity.
Generally speaking, in type-II fixed valgus deformities in which the medial
joint space on standing anteroposterior radiographs is >1 cm, less bone
than is typically removed should be resected from both the distal part of the
femur and proximal part of the tibia in order to allow for soft-tissue
balancing without elevating the joint line or creating an extension gap that
is too large. The amount of osseous resection can be templated on the
radiographs prior to surgery.
Templating
Anteroposterior Radiograph
(Fig. 3)
A vertical line is drawn down the center of the femoral and tibial
shafts.On the tibial shaft, a line is drawn perpendicular to the first line at the
level of the more involved lateral tibial plateau. This will be used to give
an idea of the tibial resection that will be performed. The relative amount of
the osseous resection as well as the ratio of lateral-to-medial resection can
be determined.On the femoral side, a line is drawn at the level of the lateral aspect of
the distal portion of the femur that is in 3° of valgus in relation to the
vertical line that was drawn in Step 1. This line gives an idea of the amount
of osseous resection needed from the medial and lateral femoral condyles.
Coronal correction with the "inside-out technique" is based on a
90° proximal tibial cut and a distal femoral cut performed in 3° of
valgus to the anatomical axis. This is done, as opposed to the typical 5°
to 7° of valgus used for a varus knee, in order to protect against
undercorrection of the underlying deformity.
A vertical line is drawn down the center of the femoral and tibial
shafts.
On the tibial shaft, a line is drawn perpendicular to the first line at the
level of the more involved lateral tibial plateau. This will be used to give
an idea of the tibial resection that will be performed. The relative amount of
the osseous resection as well as the ratio of lateral-to-medial resection can
be determined.
On the femoral side, a line is drawn at the level of the lateral aspect of
the distal portion of the femur that is in 3° of valgus in relation to the
vertical line that was drawn in Step 1. This line gives an idea of the amount
of osseous resection needed from the medial and lateral femoral condyles.
Coronal correction with the "inside-out technique" is based on a
90° proximal tibial cut and a distal femoral cut performed in 3° of
valgus to the anatomical axis. This is done, as opposed to the typical 5°
to 7° of valgus used for a varus knee, in order to protect against
undercorrection of the underlying deformity.
Lateral Radiograph
On the lateral radiograph, any posterior osteophytes should be identified
and outlined with a marker. During the procedure, these osteophytes should be
removed as they may hinder the range of motion as well as the soft-tissue
balance.The lateral radiograph is used for sizing the femoral component, as
magnification of the femoral condyle is greater (by 5% to 7%) on the
anteroposterior radiograph.
On the lateral radiograph, any posterior osteophytes should be identified
and outlined with a marker. During the procedure, these osteophytes should be
removed as they may hinder the range of motion as well as the soft-tissue
balance.
The lateral radiograph is used for sizing the femoral component, as
magnification of the femoral condyle is greater (by 5% to 7%) on the
anteroposterior radiograph.
Preoperative Selection of Implant
The goals of total knee replacement are to restore the alignment of the
knee, the joint line, the stability of the joint, and the range of motion; to
assure proper patellofemoral tracking; and to apply proper fixation
techniques. While these goals can be accomplished with any total knee
replacement design, we believe that there are inherent advantages to the use
of a posterior stabilized design when correcting the valgus deformity
(Fig. 4). First, the posterior
stabilized design is inherently more stable than a cruciate-retaining design
as a result of the post-cam mechanism and joint surface conformity. Thus, it
is applicable to most deformities. Second, the posterior stabilized design
allows for greater lateralization of the femoral and tibial components, which
greatly improves patellar tracking and minimizes the need for lateral
retinacular releases. Finally, this technique involves complete resection of
the posterior cruciate ligament, obviating any advantage offered by a
cruciate-retaining design.
Patient Positioning
After spinal anesthesia has been administered, the patient is positioned
supine on the operating table. A tourniquet is placed high on the thigh, and
the knee is shaved if needed. A lateral thigh post, positioned at the level of
the tourniquet, can help to stabilize the knee when it is placed in flexion
with the aid of a bump placed under the foot and taped securely to the
table.
CRITICAL CONCEPTSINDICATIONS:Type-I and II valgus deformities of the knee with severe arthritisCONTRAINDICATIONS:Type-III valgus deformitiesPITFALLS:With this technique, a varus tibial cut can lead to internal rotation of
the femoral component.While performing the "insideout" release of the posterior
capsule, one should use electrocautery to avoid iatrogenic injury to the
peroneal nerve.While pie-crusting of the iliotibial band is performed, caution should be
taken to avoid puncturing through the skin on the lateral side of the
knee.The surgeon should ensure that the knee is indeed balanced in extension
before assessing the flexion gap.AUTHOR UPDATE:Many different surgical techniques and approaches have been described for
correcting the valgus
knee2-17.
However, the results are generally inferior and the complication rates are
generally higher when correcting a valgus deformity compared with its varus
counterpart.These outcomes are due, in part, to the technically demanding nature of
soft-tissue balancing in the valgus knee. This, in turn, has led some surgeons
to accept the use of constrained implants when instability could not be
prevented with balancing techniques alone. Other surgeons have promoted medial
collateral ligament tightening reconstructions or lateral parapatellar
approaches to deal with these inherent instabilities. It is our opinion that
these techniques are not only unnecessary but also technically difficult and
fraught with the potential for wound and extensor mechanism complications.In an effort to deal with these issues, the technique described herein was
adopted by the senior author (C.S.R.) in 1985 to addres inherent instabilities
noted with his earlier technique, originally described in 1979, with the total
condylar knee
replacement1,2,9,18.With use of the "inside-out" technique and the PFC Sigma
posterior stabilized total knee system (DePuy Orthopaedics, Warsaw, Indiana),
no problems with late-onset instability or neurovascular injury have been
noted (Figs. 17,
18,
19,
20). Therefore, we recommend
this technique for the correction of all valgus type-I and II deformities.
CRITICAL CONCEPTS
INDICATIONS:
Type-I and II valgus deformities of the knee with severe arthritis
CONTRAINDICATIONS:
Type-III valgus deformities
PITFALLS:
With this technique, a varus tibial cut can lead to internal rotation of
the femoral component.While performing the "insideout" release of the posterior
capsule, one should use electrocautery to avoid iatrogenic injury to the
peroneal nerve.While pie-crusting of the iliotibial band is performed, caution should be
taken to avoid puncturing through the skin on the lateral side of the
knee.The surgeon should ensure that the knee is indeed balanced in extension
before assessing the flexion gap.
With this technique, a varus tibial cut can lead to internal rotation of
the femoral component.
While performing the "insideout" release of the posterior
capsule, one should use electrocautery to avoid iatrogenic injury to the
peroneal nerve.
While pie-crusting of the iliotibial band is performed, caution should be
taken to avoid puncturing through the skin on the lateral side of the
knee.
The surgeon should ensure that the knee is indeed balanced in extension
before assessing the flexion gap.
AUTHOR UPDATE:
Many different surgical techniques and approaches have been described for
correcting the valgus
knee2-17.
However, the results are generally inferior and the complication rates are
generally higher when correcting a valgus deformity compared with its varus
counterpart.
These outcomes are due, in part, to the technically demanding nature of
soft-tissue balancing in the valgus knee. This, in turn, has led some surgeons
to accept the use of constrained implants when instability could not be
prevented with balancing techniques alone. Other surgeons have promoted medial
collateral ligament tightening reconstructions or lateral parapatellar
approaches to deal with these inherent instabilities. It is our opinion that
these techniques are not only unnecessary but also technically difficult and
fraught with the potential for wound and extensor mechanism complications.
In an effort to deal with these issues, the technique described herein was
adopted by the senior author (C.S.R.) in 1985 to addres inherent instabilities
noted with his earlier technique, originally described in 1979, with the total
condylar knee
replacement1,2,9,18.
With use of the "inside-out" technique and the PFC Sigma
posterior stabilized total knee system (DePuy Orthopaedics, Warsaw, Indiana),
no problems with late-onset instability or neurovascular injury have been
noted (Figs. 17,
18,
19,
20). Therefore, we recommend
this technique for the correction of all valgus type-I and II deformities.
Approach and Exposure
After positioning, the extremity is prepared and draped. With the knee in
extension, a straight midline incision is planned. The knee is then
hyperflexed, and a straight midline incision is made starting approximately 5
to 10 cm proximal to the superior pole of the patella and continuing an equal
distance distal to its inferior pole. The incision is carried down to the deep
fascial layer to expose the quadriceps tendon, vastus medialis obliquus,
patella, and patellar tendon. Undermining of the skin flaps is avoided. A
standard medial arthrotomy is made.
The medial soft tissues are released subperiosteally from the proximal part
of the tibia with use of an osteotome or electrocautery to create a small
medial sleeve of tissue. The patella is then everted after releasing the
patellofemoral ligament, and the knee is fully flexed to expose the cruciate
ligaments and the menisci. Use of a posterior stabilized implant requires
release of both cruciate ligaments at this point. The menisci are excised, and
the tibia is maximally flexed and externally rotated to expose the entire
tibial plateau. The knee is stabilized in flexion by placing the foot on the
previously installed bump.
Tibial Resection
The proximal portion of the tibia should be resected at 90° to its long
axis. The exact level of resection will vary, depending on the preoperative
evaluation of the deformity and ligamentous laxity. In type-II valgus
deformities, one should remember to resect less bone than normal, i.e.,
generally, 6 to 8 mm should be resected from the medial side. Before the
tibial cuts are made, alignment should be confirmed with the alignment guide.
The distal portion of the alignment device should align with the center of the
talus on the anteroposterior radiograph. On the lateral radiograph, the
alignment rod should run parallel with the tibial crest. Once the cutting jig
is secured in place, the proximal tibial resection is performed.
Next, the trial tibial inset is used to determine the size of the tibial
tray needed on the basis of the anteroposterior diameter of the lateral
condyle. An alignment rod is used to check the alignment of the cut tibial
surface once again (Fig. 5).
One should remember that, when using this technique, a varus tibial cut causes
the femoral component to be internally rotated during the flexion gap
evaluation.
Femoral Resection
The femoral canal is first entered with use of a gouge to assist in drill
passage. The entry point is the intersection of the patellofemoral and the
tibiofemoral articular surfaces on the lateral and medial femoral condyles.
The canal should be entered with a drill, and then the entry point should be
enlarged by rotating the drill before sinking it completely. With a correct
entry point, the drill should not come into contact with the cortices of the
femoral shaft.
Next, the intramedullary femoral rod is inserted into the hole and a
femoral cutting jig is aligned with the distal aspect of the femur. The valgus
angle with the appropriate "right" or "left"
designation is set and placed on the front of the locating device. With a
valgus knee, the jig is set to cut in 3° of valgus to compensate for
metaphyseal-diaphyseal valgus remodeling that has usually taken place and to
avoid undercorrection of the underlying deformity
(Fig. 6).
The cutting block is then rotated until it is roughly parallel to the cut
surface of the tibia with the knee in 90° of flexion. The anterior rough
cut is made, and then the distal femoral cut is made, resecting no more than
10 mm of bone from the medial side while only removing 1 to 2 mm from the
lateral side.
At this point, the knee is extended and a spacer block is placed into the
extension gap. The limb is exsanguinated, and the tourniquet is inflated. The
patella is then prepared for resurfacing.
Evaluation of the Extension Gap
Attention can now be directed to the extension gap. With an appropriately
sized spacer block in place, the mediolateral stability of the knee is
evaluated in full extension by applying both a varus and a valgus stress
(Fig. 7). The application of
stress should demonstrate lateral side soft-tissue tightness in an unbalanced
valgus knee. Next, a lamina spreader is placed centrally in the gap. If the
knee is unbalanced, this should manifest as a trapezoidal gap. The goal is to
achieve a rectangular extension gap. When the gap is trapezoidal, soft-tissue
balancing with use of the "inside-out" technique is necessary to
fractionally lengthen the lateral side (Figs.
8 and
9).
The Steps of the "Inside-Out" Technique
Remove peripheral osteophytes.Extend the knee and distract with a lamina spreader.Irrigate and dry the joint.Palpate the posterior cruciate ligament, posterolateral corner, and
iliotibial band with a finger or with a small Cobb elevator to determine tight
structures.Release any remnant of the posterior cruciate ligament.Release the posterolateral capsule intra-articularly with use of
electrocautery at the level of the tibial cut surface from the posterior
cruciate ligament to the posterior border of the iliotibial band.
(Electrocautery is used to avoid injury to the peroneal nerve, which is
usually located <1 cm from the articular side.)Preserve the popliteus if possible, unless it is too tight.The iliotibial band is lengthened as necessary from the inside with
multiple transverse stab incisions a few centimeters proximal to the joint
line with use of the so-called pie-crusting
technique2.Repeat these steps after manual stress-testing if necessary.
Remove peripheral osteophytes.
Extend the knee and distract with a lamina spreader.
Irrigate and dry the joint.
Palpate the posterior cruciate ligament, posterolateral corner, and
iliotibial band with a finger or with a small Cobb elevator to determine tight
structures.
Release any remnant of the posterior cruciate ligament.
Release the posterolateral capsule intra-articularly with use of
electrocautery at the level of the tibial cut surface from the posterior
cruciate ligament to the posterior border of the iliotibial band.
(Electrocautery is used to avoid injury to the peroneal nerve, which is
usually located <1 cm from the articular side.)
Preserve the popliteus if possible, unless it is too tight.
The iliotibial band is lengthened as necessary from the inside with
multiple transverse stab incisions a few centimeters proximal to the joint
line with use of the so-called pie-crusting
technique2.
Repeat these steps after manual stress-testing if necessary.
The knee should now be balanced in extension. The application of a varus
and valgus stress to the knee with a spacer block in place should allow for a
"springy" give of 2 to 3 mm on both the medial and lateral sides
(Figs. 10,
11, and
12). The retention of at least
one or two of the lateral stabilizers is important for stability. If
instability is detected after the releases have been performed, then use of a
constrained component is considered.
Evaluation of the Flexion Gap
Once the knee is balanced in extension, the flexion gap can be addressed.
One should not attempt flexion gap balance until the extension gap has been
balanced. One should remember that overrelease of the medial side can lead to
internal rotation of the femoral component with use of this technique.
The knee is placed in 90° of flexion, and an anteroposterior cutting
block of the same size as the tibial component is preliminarily fixed to the
distal aspect of the femur roughly parallel to the cut tibial surface
(Fig. 13). (Bone cuts are used
to balance the knee in flexion, whereas controlled soft-tissue lengthening is
used to balance the knee in extension.) A lamina spreader is placed into the
flexion gap, and the medial and lateral flexion gaps are measured
(Fig. 14). If the gaps are
unequal, the block can be rotated and/or raised or lowered to create a
symmetric gap. The size of the gap should be the same as the extension gap or
even 2 mm less. The same spacer block that was used in the extension gap can
be placed into the flexion gap, prior to cutting the posterior condyles, to
assess flexion stability. It should create a snug fit with no visible medial
or lateral opening during internal and external rotation of the leg
(Fig. 15). If, at any time,
rotational malalignment is suspected, alignment can be checked by referencing
the cutting block with respect to the anteroposterior axis of Whiteside or the
transepicondylar
axis3.
The final anterior and posterior flexion cuts can now be made. Box and
chamfer cuts can then be made allowing for lateralization of the femoral
component (Fig. 16). Trial
components can be inserted to test the knee for stability through a full range
of motion and for adequate patellar tracking.
Maltracking of the patella should first be assessed with the tourniquet
deflated. If the components are well aligned and a release is deemed
necessary, pie-crusting of the lateral retinaculum usually suffices and avoids
the complications of performing a full longitudinal lateral release.
The knee is irrigated and the bone is dried. The components are cemented
into place. Excess cement is removed during pressurization, and the cement is
allowed to polymerize. The capsule is closed in flexion over a drain.
Postoperative Management
The patient is evaluated closely for any signs of peroneal nerve
compromise. If any sign of nerve compromise develops, the knee is placed in
flexion. If the compromise does not improve, the bandage is then loosened.
Physical therapy and continuous passive motion are initiated on the first
postoperative day after the drain has been removed. Patients are progressed to
weight-bearing as tolerated.