Operative exposure of the knee for the purpose of total prosthetic
arthroplasty has traditionally focused on the desire to minimize disturbance
of the extensor mechanism, as it was the most common reason for complications
resulting in reoperation after total knee
replacement1. More
recently, with increasing interest in less invasive surgical exposure of the
knee and minimal disruption of the quadriceps mechanism, a renewed focus on
alternatives to the median parapatellar approach has
developed2. The
greatest proven advantage of the vastus-splitting approach is the preservation
of a balanced muscle pull on the patella, which results in a markedly
diminished need for lateral retinacular release to achieve central patellar
tracking; this fact has caused us to adopt a modified vastus-splitting
technique as our standard approach for primary total knee
arthroplasty3.
Reduced blood loss and a faster functional recovery have also been claimed by
proponents as advantages of the approach, but the supporting data are less
convincing3.
CRITICAL CONCEPTSINDICATIONS:We use the vastus-splitting approach for all primary total knee
arthroplasties that have not had prior violation of the extensor mechanism.
This includes patients with valgus knees, morbid obesity, and/or severe
deformity, among other technically complex primary knee arthroplasties.CONTRAINDICATIONS:Contraindications to the use of the vastus-splitting approach include:Prior injury to, or operative violation of, the extensor mechanismRevision total knee arthroplastyPITFALLS:While our follow-up data suggest that injury to the innervation of the
vastus medialis muscle distal to the split is of little discernible functional
consequence, denervation of the distal portion of the vastus medialis is not
desirable and should be avoided. This can be accomplished by using only blunt
digital dissection in the interval of the vastus medialis split. If a crossing
neurovascular pedicle is encountered, it is readily identified with use of
this technique of dissection and no further proximal development of the split
is pursued.Difficulty may be encountered in exposing and mobilizing the extensor
mechanism. We have not had difficulty in gaining ample exposure with this
approach, despite strictly protecting the patellar tendon insertion on the
tibial tubercle. Important adjunctive maneuvers for full exposure with this
approach include elevation of a generous medial soft-tissue sleeve from the
tibia extending to the midcoronal plane of the proximal end of the tibia,
division of the suprapatellar synovial pouch, and release of the
patellofemoral ligament.Postoperative hematoma and/or bleeding in the interval of the vastus
medialis split has been previously
reported4 and can be
avoided by careful blunt digital dissection in the vastus medialis interval so
as not to damage any neurovascular structures. Release of the tourniquet prior
to closure allows careful inspection for bleeding high in the interval of the
vastus medialis split and electrocautery of any bleeding points as
indicated.AUTHOR UPDATE:Since publication of the article, there have been no modifications of the
described technique and it has been adopted as our standard operative approach
for primary total knee arthroplasty.
CRITICAL CONCEPTS
INDICATIONS:
We use the vastus-splitting approach for all primary total knee
arthroplasties that have not had prior violation of the extensor mechanism.
This includes patients with valgus knees, morbid obesity, and/or severe
deformity, among other technically complex primary knee arthroplasties.
CONTRAINDICATIONS:
Contraindications to the use of the vastus-splitting approach include:
Prior injury to, or operative violation of, the extensor mechanismRevision total knee arthroplasty
Prior injury to, or operative violation of, the extensor mechanism
Revision total knee arthroplasty
PITFALLS:
While our follow-up data suggest that injury to the innervation of the
vastus medialis muscle distal to the split is of little discernible functional
consequence, denervation of the distal portion of the vastus medialis is not
desirable and should be avoided. This can be accomplished by using only blunt
digital dissection in the interval of the vastus medialis split. If a crossing
neurovascular pedicle is encountered, it is readily identified with use of
this technique of dissection and no further proximal development of the split
is pursued.
Difficulty may be encountered in exposing and mobilizing the extensor
mechanism. We have not had difficulty in gaining ample exposure with this
approach, despite strictly protecting the patellar tendon insertion on the
tibial tubercle. Important adjunctive maneuvers for full exposure with this
approach include elevation of a generous medial soft-tissue sleeve from the
tibia extending to the midcoronal plane of the proximal end of the tibia,
division of the suprapatellar synovial pouch, and release of the
patellofemoral ligament.
Postoperative hematoma and/or bleeding in the interval of the vastus
medialis split has been previously
reported4 and can be
avoided by careful blunt digital dissection in the vastus medialis interval so
as not to damage any neurovascular structures. Release of the tourniquet prior
to closure allows careful inspection for bleeding high in the interval of the
vastus medialis split and electrocautery of any bleeding points as
indicated.
AUTHOR UPDATE:
Since publication of the article, there have been no modifications of the
described technique and it has been adopted as our standard operative approach
for primary total knee arthroplasty.
Epidural anesthesia by continuous catheter with intravenous sedation is our
standard anesthetic for total knee arthroplasty, and warfarin, which is
started the night before the operation with a target international normalized
ratio of 2.0, is our preferred prophylaxis for venous thromboembolic disease.
Radiographs are hung in the operating room
(Fig. 1), and we routinely use
a split leg table (Fig. 2) for
total knee arthroplasty; it allows us to break the table at the knee on the
operative side, providing a direct end-on view of the involved limb. A midline
incision of standard length is used, and the operation is performed under
tourniquet control.
Full-thickness subcutaneous flaps are raised medially and laterally, to
include the superficial retinaculum as a continuous layer for later use during
the closure (Fig. 3). Along the
medial side, the incision in the superficial retinacular layer is extended
proximally into the fascia overlying the vastus medialis muscle approximately
1 cm medial to the border of the quadriceps tendon
(Fig. 4). The vastus medialis
fascia is then sharply elevated from the underlying muscle in continuity with
the superficial retinaculum more distally; a scalpel is required to separate
the muscle fibers from the overlying fascia near the quadriceps tendon, but,
as the dissection proceeds medially within the fascial compartment, the muscle
easily and cleanly separates from the fascia with blunt dissection
(Fig. 5). Finally, digital
dissection is used to mobilize the most medial border of the vastus medialis
within the fascial compartment, which is now clearly visible from an
"inside-out" perspective.
With the knee flexed approximately 30°, just enough to tension the
extensor mechanism, a point at the superomedial corner of the patella is
chosen as the site of the split in the vastus medialis. A large clamp is used
to initiate the split in line with the muscle fibers of the vastus medialis
(Fig. 6); the clamp is made to
penetrate the muscle through its full thickness, including the deep fascia,
until a fatty layer is identified deep to the vastus medialis muscle. Two
Army-Navy retractors are placed in the split, which is then developed in a
proximal direction within the fascial compartment
(Fig. 7). A dissecting scissor
is used to extend the split for the first 1 to 2 cm, but thereafter it is
imperative that the split be extended by digital dissection
(Fig. 8) to avoid injury to any
crossing neurovascular structures that will supply the vastus medialis muscle
distal to the split. This interval in the muscle is thereby extended to the
most medial limit of the fascial compartment, for a distance of several
centimeters, or until a neurovascular pedicle that precludes further blunt
dissection is encountered.
The arthrotomy is then continued distally from the superior medial corner
of the patella, leaving a soft-tissue cuff along the medial border of the
patella and ending alongside the medial edge of the patellar tendon on the
tibia, in a fashion similar to that used with a conventional medial
parapatellar approach. No part of the patellar tendon is elevated or released
from the tibial tubercle; the distal portion of the extensor mechanism
insertion is thereby left undisturbed throughout the procedure. With the knee
in full extension, a soft-tissue sleeve is elevated from the medial part of
the tibia to include the capsule and the deep medial collateral ligament
(Fig. 9). The dissection of
this sleeve is extended medially to the midcoronal plane to afford
mobilization and anterior displacement of the tibia relative to the femur with
external rotation and flexion of the tibia. With the knee still in extension,
the infrapatellar fat pad is resected and a limited synovectomy is performed
over the anterior aspect of the distal end of the femur to expose the osseous
surface. Finally, at this juncture, the synovium of the suprapatellar pouch is
incised in the coronal plane (Figs. 10-A
and 10-B) to mobilize the overlying quadriceps tendon to
facilitate patellar displacement and/or eversion.
The knee is then hyperflexed, and, with external rotation of the tibia and
eversion of the patella, the tibia is dislocated anterior to the femur and a
retractor is placed behind the posterior border of the proximal part of the
tibia. It should again be emphasized that the insertion of the patellar tendon
on the tibia is not disturbed. A gloved finger then checks the vastus medialis
split proximally for excessive tension, and the split is extended in a blunt
fashion if it is felt to be tight. The extensor mechanism is further mobilized
by incision of the patellofemoral ligament
(Figs. 11-A and 11-B). This
maneuver is accomplished with a long right-angle clamp that is passed in a
subsynovial plane from distal to proximal, anterior to the lateral epicondyle
(to protect the lateral collateral ligament); the patellofemoral ligament is
incised along the clamp, which greatly mobilizes the extensor mechanism and
eliminates any remaining tension on the proximal end of the vastus medialis
split or the distal insertion of the patellar tendon. Bent Hohmann retractors
are then placed at the medial and lateral borders of the tibia to protect the
medial capsular sleeve and patellar tendon, respectively, to conclude exposure
of the upper tibia (Fig.
12).
With the tibia fully exposed and displaced anterior to the distal aspect of
the femur, the menisci are resected and the cruciate ligaments are excised.
The operation then proceeds in standard fashion by first cutting the proximal
end of the tibia followed by setting the femoral component rotation parallel
to the upper tibial surface to create a rectangular flexion space
(Figs. 13-A and 13-B). The
anterior, distal, and posterior femoral cuts are made sequentially, and spacer
blocks are used to guide soft-tissue releases to balance flexion and extension
gaps as well as to guide the creation of symmetrical medial and lateral spaces
in extension. Trial components are placed, and a nonprosthetic arthroplasty of
the patella is performed (Figs. 14-A
through 14-E); the bone of the superior pole of the patella is
resected flush with the undersurface of the quadriceps tendon, and the
remaining medial, lateral, and inferior osteophytes are removed from the
patella with a rongeur. Patellar tracking is checked at this point, and tibial
component rotation is determined after several sequences of flexion and
extension of the knee with the trial components in position. Typically, no
lateral release is required in knees with varus alignment; if a release is
necessary to achieve central patellar tracking, it is performed with an
"inside-out" technique in a subsynovial plane to preserve the
superficial retinacular structures of the lateral capsule.
After cementation of the components and removal of any cement debris, the
tourniquet is released and hemostasis is achieved. It is important to
specifically check the most proximal limit of the vastus medialis split to
identify any bleeding vessel that may have been inadvertently injured during
the procedure (Fig. 15). With
only blunt digital dissection in this interval, such bleeding is rarely
encountered but should be controlled with electrocautery if discovered. A deep
suction drain is placed, and closure of the capsule is accomplished with the
knee flexed passively over a bump (Figs.
16-A and 16-B) with reapproximation of the medial capsule,
starting proximally at the superomedial corner of the patella and progressing
distally to the tibia. No sutures are placed in the vastus medialis muscle
fibers. A second drain is placed in the subcutaneous tissues, and the vastus
medialis fascial compartment is reapproximated to the medial border of the
quadriceps tendon together with the superficial retinacular tissues and the
subcutaneous layer (Fig. 17).
In this manner, the vastus medialis muscle unit is reconstituted, without
placing necrosing sutures in the muscle fibers, and the dead space in the
subcutaneous plane and muscle split is eliminated.
Aftercare and pain control are facilitated by maintenance of the indwelling
epidural catheter with a mixed anesthetic and narcotic infusion for
forty-eight hours postoperatively while the patient participates in a routine
physical therapy regimen. A continuous passive motion machine is not used, and
active knee flexion and quadriceps strengthening exercises are employed. The
epidural infusion is discontinued at forty-eight hours postoperatively, and
the catheter is removed thereafter, provided that the international normalized
ratio is =1.5; if the international normalized ratio is elevated, warfarin
is withheld until the specified level is attained to allow catheter removal
and then the warfarin is restarted. The average length of stay after total
knee arthroplasty is three days, with subsequent weight-bearing allowed as
tolerated when the patient can perform a straight-leg lift with 5 lb (2.3
kg).