David F.
Bindelglass, M.D., Jondy L. Cohen, M.D., and
Lawrence D.
Door, M.D.
The surgical
technique for total knee arthroplasty (TKA) as performed by
he senior author is reviewed. Certain steps in the procedure
are discussed in detail to provide insight into how these
steps can be carried out more precisely with reproducible
results. The method of cementing all three components with
one mixture of cement is particularly helpful and time
saving, which makes cemented fixation more attractive. As in
any surgery, attention to detail and organization produces
superior results
Much has been written about the techniques of performing total knee arthroplasty
(TKA).8-11 The purpose of this article is to
detail our technique for cemented TKA, which can be used
whether the posterior cruciate ligament (PCL) is retained or
sacrificed. The technique will be illustrated with cruciate
retention because the operation is more difficult when the
PCL is retained. Emphasis will be placed on technical steps
that simplify the operation and on dealing with common
problems that may complicate the procedure. Exposure, soft
tissue balancing, bone cuts, and the technique for cementing
all three components from one mixture of cement will be
examined. Attention to detail, as outlined below, is
critical to achieving optimal results.
EXPOSURE
Exposure is accomplished
through a midline incision.29 A tourniquet is
used in almost all cases, the exception being in the limb
with any vascular compromise or diabetes. The distal
incision should pass just medial to the tibial tubercle
rather than directly over it, avoiding a scar over the bony
prominence and decreasing the chance of wound healing
problems. Prior incisions should be incorporated and the
skin incision for TKA modified to allow this. Specifically,
parallel incisions isolating an island of skin must be
avoided.10
The approach to the knee joint
is made through a medial parapatellar incision. The medial
subvastus approach described in this journal of Mullen can
also be used and avoids any incision into the quadriceps
mechanism. The patella is then everted. If this cannot be
accomplished a number of options exist. The incision in the
quadriceps tendon should be carried proximally to the most
proximal extent of the tendinous portion. Distally, the
medial third of the patella tendon can be elevated off the
tubercle with a scalpel. The tendon is elevated in
continuity with the anterior periosteum so that if an
accidental avulsion does occur this soft tissue remains as a
continuous sleeve that will scar back down. Sometimes a
lateral release is necessary at this stage of the procedure
in order to successfully evert the patella. Finally, in a
very stiff knee (60° arc of motion or less) a patellar
turndown approach may be needed.12 A modification
of the Coonse Adams approach is used. A standard lateral
release is performed and carried proximally along the
lateral border of the quadriceps tendon. At the proximal end
of the incision an oblique cut is made across the tendon,
connecting the lateral release and medial parapatella
incisions (Fig 1). This incision passes only through the
tendinous portion, and the deeper muscle fibers often can be
left intact. After the components are put in place the final
repair is done. The tendon is reattached side to side
medially so that proper tracking is achieved. Proper tension
to minimize a postoperative lag is achieved with the knee
flexed at 90° . The quadriceps mechanism must be absolutely
taut and the patella held centered in the trochlear groove
so that it cannot be moved at all with manual
pressure.
Rehabilitation after quadriceps
turndown is modified so that range of motion is restricted
to 60° passively during the first 10 postoperative days. No
active motion is allowed and an immobilizer is worn except
when the patient is in continuous passive motion (CPM).
After 10 days, unrestricted active and passive motion are
allowed.
PATELLA CUT
After the patella is prepared
the medial soft tissues are released from the tibia. While a
medial release is part of the soft tissue balancing in
correcting a varus deformity, some release is necessary in
all knees for exposure. Adequate tibial preparation requires
anterior subluxation of the tibia, which cannot be
accomplished without release of the medial capsule from the
proximal tibia. The scalpel or electrocautery is used
initially to elevate the capsule subperiosteally at the
level of the tibial tubercle. This begins at the edge of the
distal portion of the capsular incision and is wide enough
to allow an elevator to peel periosteum as far medially and
posteriorly as the medial edge of the triangular tibia (Fig.
2a). The elevator is replaced by a bent Hohmann retractor
(Fig 2b). A scalpel is used to release the medial sleeve,
which is now under tension. This is carried proximally
through the coronoid ligaments between the tibia and the
medial meniscus, and the transverse ligament is cut allowing
the medial meniscus to fall away with the medial soft
tissues. Dissection continues posteriorly with a scalpel
while under direct vision and then may be continued further
with an elevator, care being taken to remain in contact with
the bone. In all knees the dissection is continued to the
midcoronal plane and in varus knees to the midposterior
line.
Elevation of the soft tissue
exposes osteophytes on the proximal tibia and distal femur.
These are removed with an osteotome to release tension on
the medial soft tissue, a procedure that is an integral
portion of soft tissue balancing (Fig. 3). The remnant of
the medial meniscus is now visible. One clamp is placed at
its anterior edge and a second on the medial capsule to
place it under tension. The meniscus is resected leaving a
small cuff at its attachment to the medial collateral
ligaments (MCL) so as to protect the latter
structure.
The knee is now flexed with the
patella everted. In the stiff knee a release of the
superficial MCL will be necessary before flexing the knee.
The MCL can be very tight in the stiff knee and flexion may
lead to tearing of the ligament or avulsion of the medial
epicondyle.12
The anterior cruciate ligament
(ACL) is divided in mid substance with a knife, and the
lateral meniscus is divided anteriorly where it becomes the
transverse ligament, so that it will fall away laterally. As
much fat pad as necessary is excised so that the surgeon’s
view of the lateral plateau is not obstructed. The tibia can
now be displaced forward by placing a straight Hohmann
retractor in the midline posteriorly. The foot is externally
rotated with one hand and the tibia pried forward using the
retractor (Fig 4). Residual medial and lateral meniscal
tissue is excised. A bent Hohmann retractor is used on the
lateral side to hold the extensor mechanism and lateral
capsule laterally. The Hohmann is placed in the lateral
midline and should be in place whenever any work is done on
the tibia. The lateral patellofemoral ligaments are incised
to facilitate retraction of the patella. The synovium that
overlies the anterior femoral cortex is incised so that the
junction between the trochlea and the anterior cortex is
clearly seen. Undercutting or notching the cortex can then
be avoided.
BONE CUTS
Patellofemoral problems
represent a large percentage of complications of TKA.13 Most surgeons leave the preparation of the patella as
the last step in the operation and as a result may not treat
it with the same detail to attention and precision as in the
tibial and femoral preparation. Therefore, the patella cut
is performed first. A patellar osteotomy guide is used to
perform the cut. It is important to maintain the thickness
of the patella during TKA for proper tracking. The initial
thickness is measured with a caliper, and the level of cut
determined so that the combined thickness of the patellar
bone and prosthesis equals the initial thickness.
Osteophytes are removed from the periphery to facilitate
proper positioning of the jib and the starting point for the
saw, and then the cut is made (Fig 5). Fixation holes are
made using a guide and the trial patella is placed. It
should cover the cut surface of the bone nearly completely.
Excess bone is removed with a rongeur (Fig. 6).
Intramedullary cutting guides
have become generally accepted for the distal femoral cuts.
Placement of the opening hole can affect the component
position. The femoral starting point should be just anterior
to the attachment of the PCL and a few millimeters lateral
to the midline. The canal should be drilled with a larger
drill than the alignment rod and fat contents should be
removed with suction. A fluted rod should be used. These
precautions reduce the pressure increase caused by a rod in
the medullary canal, which can lead to fat
emboli.7 The surgeon should also have a short
alignment rod and external guide for cases where the
medullary canal is abnormal (ie, postfracture). Once the
distal cutting guide is fixed in place, the angle of the cut
can be checked using a block with a hole made at 6° to its
axis; this first over the alignment rod confirming proper
orientation for the cut (Fig 7). Anterior and posterior cuts
are made using standard cutting blocks.
To promote better patellar
tracking, the anterior and posterior femur are cut in slight
external rotation. External rotation cuts also compensate
for a 0° tibial cut rather than the anatomic 3° varus,
maintaining a symmetric flexion gap.10 External
rotation of the component can be checked three ways. First,
the femur can be lifted up by the cutting block so the tibia
is lifted off the table. The block position is now evaluated
by observing the rotation of the block relative to the
femoral shaft. (Fig. 8a). Second, most blocks with measuring
guides have an anterior projection whose position relative
to the anterior femoral cortex can be noted to determine
rotation. Lateral rotation denotes external rotation (Fig.
8b). Third, when the posterior cuts are made, assuming
minimal deformity of the posterior condyles, the medial
posterior condyle fragment should be thicker than the
lateral (Fig. 8C).
Chamfer cuts are completed and
a trial femur malleted into place. With the trial in place,
osteophytes in the intercondylar notch can be resected so
that the inner walls of the notch vault become continuous
with the edge of the prosthesis (Fig. 9a). A small rongeur
should pass freely through the notch on either side of the
PCL (Fig. 9b).
TIBIAL CUTS
The authors prefer the use of
an intramedullary (IM) tibial cutting guide as recommended
by Laskin11 and Whitesides.16 This
produces the most consistent results for tibial bone cuts
and avoids varus. Recent criticism of the accuracy of
intramedullary guides is based on the inability to fully
seat the rod, especially in valgus knees.14 However, using a ¼" rod resolves this problem.
The entry point for the IM rod
is the insertion of the ACL on the tibia. Precautions are
again used to avoid increasing intramedullary pressure. A
guide is used that makes certain the mediolateral cut of the
tibial surface will be exactly perpendicular to the long
axis of the tibia. We prefer this cut of the medial tibia,
rather than the anatomic 3° varus cut, so that an extensive
varus tibial cut is avoided. A posterior slope of 7° to 8°
is built into the cutting jib. Initially recommended by the
Townley,15 a posterior slope significantly
improves postoperative flexion.
The rotation of the cutting
guide relative to the tibia can affect the orientation of
the tibial cut. The jig should be centered over the tibial
tubercle between the medial third and lateral two thirds of
the tubercle (Fig. 10). If an extramedullary guide is used
it should be closer to the medial malleolus than the center
of the ankle. The level of the tibial cut is important
because tibial bone weakens rapidly as one goes distally
from the joint surface. 1 Tibial fixation is
compromised by a low tibial cut. Maximum thickness of the
tibial cut should be no more than 5 to 8 mm. Specifically,
defects in the tibial surface should not be the guide for
determining the depth of the tibial cut (Fig.
11).6
SOFT TISSUE
BALANCING
Most soft tissue balancing is
performed prior to the bone cuts. Releases are done
routinely as part of the exposure, with the extent depending
on the measured preoperative deformity. The previous section
on exposure describes the standard medial release. In
addition, in a varus knee with the tibia subluxed forward,
more posterior osteophyte is removed and the cautery can be
used to release 1 cm of tissue from the top of the tibia
between the posteromedial corner and the posterior midline
(Fig.12). This is all the release necessary in 98% of varus
knees.5
For a valgus knee an analogous
release is done laterally as part of the exposure. Once the
knee is flexed a bent Hohmann retractor is placed
anterolaterally on the proximal tibia to hold the patella
laterally. The cautery is used to elevate 1 cm of capsule
from the lateral proximal tibia, around to the posterior
midline (Fig. 13). Osteophytes are removed from the tibia
and femur. In most valgus knees this is an adequate
release.
For inspection of the posterior
knee joint a lamina spreader is used to jack open the joint.
Posterior osteophytes are palpated and then removed with a
curved osteotome until flush with a posterior diaphyseal
cortex (Fig 14.) The elevator may also be used to elevate
the posterior capsule from the posterior diaphysis. In the
knee with a preoperative flexion contracture this will
release a fixed contracture of no more than 15° .
After any posterior release is
completed the trial components are placed. The knee is then
tested for varus/valgus stability at 90° , 30° and full
extension. The varus knee may still have medial tightness
necessitating further medial release. The superficial MCL is
released subperiosteally with an osteotome, creating a
continuous sleeve of medial soft tissue (Fig 15). This
sleeve maintains continuity of the medial side. No repair is
therefore necessary. A detailed discussion of techniques for
dealing with varus deformity has been previously
published.5
When valgus knees remain tight
on the lateral side, medial laxity will remain. There are
three lateral structures to be released. The first is the
popliteus, which is released sharply from its femoral
attachment. If this release is insufficient, the iliotibial
(IT) band is step-cut at the level of the joint line and
stretched (Fig 16). An alternative method is to Z-cut the IT
band and lengthen the tendon.8 Lastly, in rare
cases the lateral collateral ligament is sharply released
from the femur. These releases generally require a thicker
tibial polyethylene component.
Once the medial and lateral
soft tissue balance is completed, alignment and stability
are again evaluated. The tightness of the PCL is assessed.
With the knee flexed at 90° , the distal femoral condyles
should be within 1 cm of the anterior lip of the tibial
component (Fig 17). If the femoral component rests on the
posterior half of the tibial tray the PCL needs to be
recessed. This is done with electrocautery, partially
dissecting the attachment off the femur (Fig 18). Usually 2
to 3 mm is sufficient, so that the tibia falls back easily
under the femur. Lastly, patellar tracking is assessed. The
patella is reduced and the knee is ranged. The foot is held
in neutral rotation, and as the knee is flexed and extended
the patella tilt and displacement are assessed. If the
patella tilts laterally or tracks laterally, a lateral
release is needed. This is performed from the inside out.
The patella is grabbed between the thumb and index finger
and pulled forward to put the retinaculum under tension. An
incision is made through only the retinaculum at the level
of the patella and approximately 1 t 2 cm lateral to the
patella. Once the retinaculum is incised the surgeon is able
to get a finger between the retinaculum and the subcutaneous
tissue (fig 19). This finger protects from ‘button-holing’
the skin. The release is then carried straight down the
tibia over the finger. Tracking is again checked. If the
patella still tracks laterally the lateral release is
extended proximally into the muscle fibers of the vastus
lateralis, and if this is still insufficient then the
modified turndown described above is performed.
BONE DEFECTS
A number of techniques exist
for dealing with bone defects. We have previously discussed
the use of bone grafts.4 Richard Scott initiated
the use of wedges, which has become more common.3 In general, if 50% of the condyle is involved then some form
of augmentation is necessary.
CEMENT
FIXATION
One of the reasons given for
cementless fixation is a reduction in operating room time.
The increased time required for cementing results from
separately cementing the femur and tibia. Ewald initially
advocated simultaneously cementing all components and
discusses the technique in this issue. We too use a
technique where all three components are cemented with one
mixture of cement.
Bone is lavaged with a water
pik and packed with a sponge while two packages of Simplex
cement (Howmedica, Rutherford, NJ) are mixed. At 2 minutes,
cement is spread onto the patella surface with a spatula.
When the component has multiple fixation pegs the holes may
be difficult to find. Methylene blue can be placed in the
holes prior to cementing to outline them after the cement is
manually pressurized into the bone. (Fig 20). The patella is
seated and held with the surgeon’s thumb and index finger. A
curette is used to remove excess cement from the periphery.
The assistant then maintains manual
pressure.
