Patient Positioning
We place the patient supine on the operating table, with a sterile
pneumatic tourniquet around the thigh and a padded bump beneath the
trochanter. The leg is prepared and draped free, and the foot is held in a leg
holder during the procedure to allow variable amounts of flexion and
extension.
Exposure of the Knee
The pneumatic tourniquet is inflated after exsanguination with an Esmarch
bandage and flexion of the knee. Previous incisions are marked
(Fig. 3). We prefer a midline
skin incision; however, use of a previous incision is recommended when
present. If multiple incisions are present, we use the most lateral incision
closest to the midline, in order to preserve blood supply to the skin. Often
these are knees that have had multiple operations and may have undergone a
previous gastrocnemius flap or other soft-tissue coverage procedure. In this
instance, we are careful not to disrupt the blood supply to this coverage and
we have a plastic reconstructive surgeon available to assist during the
exposure. The dissection is carried down in the midline with conservative
elevation of skin and subcutaneous flaps. The retinaculum and extensor
mechanism are then exposed. A midline incision is performed through the
remaining extensor mechanism (the quadriceps tendon and patellar tendon or
scar tissue), creating medial and lateral flaps of retinaculum and exposing
the joint (Fig. 4). Culture
specimens are obtained and sent to the microbiology laboratory, and synovial
fluid is assessed for cell count. If there is a native patella or a remnant,
it is osteotomized in a longitudinal fashion in the midline
(Fig. 5), in line with the
midline soft-tissue retinacular incision (Figs.
6 and
7). The patellar bone is then
shelled out and carefully removed, preserving the soft tissues in continuity
with the medial and lateral retinacular flaps. This bone is kept for
autogenous bone graft as necessary. The medial and lateral gutters and
suprapatellar pouch are recreated. The midline incision is carried proximally
into the host quadriceps, again maintaining a medial and lateral sleeve of
tissue for later closure. The midline incision is carried over the host tibial
tubercle with elevation of medial and lateral soft-tissue flaps (Figs.
8 and
9).
Total Knee Arthroplasty Component Revision and Reimplantation
Revision total knee arthroplasty then proceeds as necessary. Rotation of
the femoral and tibial components is assessed, and our threshold for revision
of malrotated components is very low, as they can contribute to extensor
mechanism maltracking (Fig.
10). Balancing of flexion and extension gaps is then performed,
with careful attention to obtaining full passive extension of the knee. Trial
components are removed, and definitive components are implanted in a routine
fashion. The final polyethylene liner is inserted prior to insertion of the
extensor mechanism allograft. We have used this procedure with primary
cruciate-retaining, posterior stabilized, revision constrained condylar
designs, and constrained hinge knee designs. If stemmed components are being
inserted, it may be preferable to prepare the host tibial bone trough and
place the fixation wires through the tibia at this stage, followed by
insertion of the stemmed tibial component.
The revision total knee arthroplasty implants are now in place, and the
host tissues are next prepared to accept the extensor mechanism allograft.
Allograft Preparation on the Back Table
Simultaneous with the revision or placement of the total knee arthroplasty
components, the allograft specimen may be prepared on the back table. The host
tibial trough is not made until we have harvested the allograft tibial block,
in order to ensure a press-fit of our allograft tibial block. We first mark
with a marking pen over the allograft tibial tubercle and proximal part of the
tibia our planned harvest of the allograft tibial bone block, in a rectangular
fashion. The length of the block should be approximately 6 to 8 cm from the
tibial articular surface of the allograft to the distal cut. The width of the
block is 2 cm, and the depth is 2 cm (Fig.
11). We cut on the conservative side and make the cuts slightly
larger if necessary, as these may be trimmed or down-sized as needed. With use
of a small thin microsagittal saw, the allograft block is harvested from the
allograft tibia (Fig. 12),
with careful attention so as not to damage the allograft patellar tendon
(Fig. 13). The proximal bevel
or "dovetail" on the allograft bone block is not created during
this part of the harvest, as it is simpler to perform once the graft has been
removed from the allograft tibia.
Once the allograft bone block has been carefully removed from the allograft
tibia, we next prepare the bevel, or dovetail, on the proximal aspect of the
removed bone block (Fig. 12).
This serves two purposes. The first is to lock into the host native tibial
trough and avoid graft escape. The second is to allow a press-fit of the graft
into the native tibia. Using a marking pen
(Fig. 13), we draw an angle of
30° to 40° (from the perpendicular of the graft) as a bevel and cut it
carefully with the thin saw blade. The length of the bevel is approximately 20
to 25 mm (Figs. 14-A,
14-B,
14-C,
14-D).
Two number-2 nonabsorbable sutures are then placed in a running, locked
fashion, as described by Krackow et
al.9, along the
medial and lateral aspects of the allograft quadriceps tendon, exiting out
proximally. These sutures are kept long, and they are placed so that the
assistant can apply tension and pull the allograft tightly proximally once it
has been secured into the prepared tibial bed.
The graft and the proximal two sutures are then placed carefully in a basin
on the back table, and attention is turned to the preparation of the proximal
part of the host tibia.
CRITICAL CONCEPTSINDICATIONS:Disruption of the extensor mechanism (extensor lag) that is not amenable to
or has failed a primary repairPatellar tendon rupture, avulsion, or prior excisionQuadriceps tendon rupture, avulsion, or prior excisionPatellar fragmentation or nonreconstructible patellar fractureSevere heterotopic ossification of the extensor mechanismPrevious patellectomy with a total knee arthroplasty and symptomatic
extensor lagSevere patella infera and arthrofibrosis of the extensor mechanismConversion of previous knee arthrodesis to a total knee replacement with a
fibrosed or deficient extensor mechanismCONTRAINDICATIONS:Ongoing infection or concurrent infection of a total knee replacement at or
near the operative siteReconstructible extensor mechanism with primary repair or local autogenous
reinforcement tissueAn unreliable, noncompliant patient who is unable to cooperate with
postoperative rehabilitationPITFALLS:A fresh-frozen, nonirradiated allograft specimen consisting of a quadriceps
tendon, patella, patellar tendon, and tibial bone is required. It is
preferable to have at least 5 cm of quadriceps tendon allograft for suture
repair into the host quadriceps mechanism.We recommend use of a midline approach through the extensor mechanism
anteriorly. Large medial and lateral flaps that provide excellent tissue for
closure over the extensor mechanism allograft are developed. If there is
native patella remaining, this is osteotomized transversely in line with the
midline arthrotomy. The patellar remnant is then shelled out and removed.Component revision is often necessary. It is important that the knee be
able to be passively brought to full extension with the trial implants in
place, in order to ensure full extension is attainable postoperatively.It is important that the proximal aspect of the allograft tibial bone and
the bone trough on the native tibia be dovetailed in order to lock, or
press-fit, the allograft into the native tibia and resist proximal
migration.When the allograft is sutured proximally into the native quadriceps,
tension must be maintained on the allograft with the knee in full
extension.It is not desirable to have an overly long allograft quadriceps tendon. A
segment that is too long will end up being sewn proximally into the rectus
femoris muscle instead of into the host quadriceps tendon.The host retinaculum medial and lateral flaps should be sewn over the
allograft as much as possible in order to cover the allograft.The knee should not be flexed intraoperatively to assess the
flexion of the construct. The patient is managed with immobilization of the
knee in full extension with touch-down weight-bearing for eight weeks, and
then a directed physical therapy program is begun.The allograft patella is not resurfaced in order to avoid creating a
stress-riser in it.AUTHOR UPDATE:This technique has not been modified since the publication of our original
study. We emphasize that success with this technique requires that several
critical aspects be carefully followed. The midline incision and retention of
host medial and lateral retinacular tissue is important. Removing the patellar
remnant in this way ensures that medial and lateral flaps remain for closure,
and it improves exposure. Tensioning the allograft tightly in full extension
is necessary to help to reduce the risk of allograft attenuation and extensor
lag. Closure of the medial and lateral flaps over the allograft as much as
possible reduces the contact of the allograft with subcutaneous tissues and,
we believe, reduces the risk of infection. We emphasize that we do not flex
the repair once it is completed, as has been recommended by other authors.
CRITICAL CONCEPTS
INDICATIONS:
Disruption of the extensor mechanism (extensor lag) that is not amenable to
or has failed a primary repairPatellar tendon rupture, avulsion, or prior excisionQuadriceps tendon rupture, avulsion, or prior excisionPatellar fragmentation or nonreconstructible patellar fractureSevere heterotopic ossification of the extensor mechanismPrevious patellectomy with a total knee arthroplasty and symptomatic
extensor lagSevere patella infera and arthrofibrosis of the extensor mechanismConversion of previous knee arthrodesis to a total knee replacement with a
fibrosed or deficient extensor mechanism
Disruption of the extensor mechanism (extensor lag) that is not amenable to
or has failed a primary repair
Patellar tendon rupture, avulsion, or prior excision
Quadriceps tendon rupture, avulsion, or prior excision
Patellar fragmentation or nonreconstructible patellar fracture
Severe heterotopic ossification of the extensor mechanism
Previous patellectomy with a total knee arthroplasty and symptomatic
extensor lag
Severe patella infera and arthrofibrosis of the extensor mechanism
Conversion of previous knee arthrodesis to a total knee replacement with a
fibrosed or deficient extensor mechanism
CONTRAINDICATIONS:
Ongoing infection or concurrent infection of a total knee replacement at or
near the operative siteReconstructible extensor mechanism with primary repair or local autogenous
reinforcement tissueAn unreliable, noncompliant patient who is unable to cooperate with
postoperative rehabilitation
Ongoing infection or concurrent infection of a total knee replacement at or
near the operative site
Reconstructible extensor mechanism with primary repair or local autogenous
reinforcement tissue
An unreliable, noncompliant patient who is unable to cooperate with
postoperative rehabilitation
PITFALLS:
A fresh-frozen, nonirradiated allograft specimen consisting of a quadriceps
tendon, patella, patellar tendon, and tibial bone is required. It is
preferable to have at least 5 cm of quadriceps tendon allograft for suture
repair into the host quadriceps mechanism.We recommend use of a midline approach through the extensor mechanism
anteriorly. Large medial and lateral flaps that provide excellent tissue for
closure over the extensor mechanism allograft are developed. If there is
native patella remaining, this is osteotomized transversely in line with the
midline arthrotomy. The patellar remnant is then shelled out and removed.Component revision is often necessary. It is important that the knee be
able to be passively brought to full extension with the trial implants in
place, in order to ensure full extension is attainable postoperatively.It is important that the proximal aspect of the allograft tibial bone and
the bone trough on the native tibia be dovetailed in order to lock, or
press-fit, the allograft into the native tibia and resist proximal
migration.When the allograft is sutured proximally into the native quadriceps,
tension must be maintained on the allograft with the knee in full
extension.It is not desirable to have an overly long allograft quadriceps tendon. A
segment that is too long will end up being sewn proximally into the rectus
femoris muscle instead of into the host quadriceps tendon.The host retinaculum medial and lateral flaps should be sewn over the
allograft as much as possible in order to cover the allograft.The knee should not be flexed intraoperatively to assess the
flexion of the construct. The patient is managed with immobilization of the
knee in full extension with touch-down weight-bearing for eight weeks, and
then a directed physical therapy program is begun.The allograft patella is not resurfaced in order to avoid creating a
stress-riser in it.
A fresh-frozen, nonirradiated allograft specimen consisting of a quadriceps
tendon, patella, patellar tendon, and tibial bone is required. It is
preferable to have at least 5 cm of quadriceps tendon allograft for suture
repair into the host quadriceps mechanism.
We recommend use of a midline approach through the extensor mechanism
anteriorly. Large medial and lateral flaps that provide excellent tissue for
closure over the extensor mechanism allograft are developed. If there is
native patella remaining, this is osteotomized transversely in line with the
midline arthrotomy. The patellar remnant is then shelled out and removed.
Component revision is often necessary. It is important that the knee be
able to be passively brought to full extension with the trial implants in
place, in order to ensure full extension is attainable postoperatively.
It is important that the proximal aspect of the allograft tibial bone and
the bone trough on the native tibia be dovetailed in order to lock, or
press-fit, the allograft into the native tibia and resist proximal
migration.
When the allograft is sutured proximally into the native quadriceps,
tension must be maintained on the allograft with the knee in full
extension.
It is not desirable to have an overly long allograft quadriceps tendon. A
segment that is too long will end up being sewn proximally into the rectus
femoris muscle instead of into the host quadriceps tendon.
The host retinaculum medial and lateral flaps should be sewn over the
allograft as much as possible in order to cover the allograft.
The knee should not be flexed intraoperatively to assess the
flexion of the construct. The patient is managed with immobilization of the
knee in full extension with touch-down weight-bearing for eight weeks, and
then a directed physical therapy program is begun.
The allograft patella is not resurfaced in order to avoid creating a
stress-riser in it.
AUTHOR UPDATE:
This technique has not been modified since the publication of our original
study. We emphasize that success with this technique requires that several
critical aspects be carefully followed. The midline incision and retention of
host medial and lateral retinacular tissue is important. Removing the patellar
remnant in this way ensures that medial and lateral flaps remain for closure,
and it improves exposure. Tensioning the allograft tightly in full extension
is necessary to help to reduce the risk of allograft attenuation and extensor
lag. Closure of the medial and lateral flaps over the allograft as much as
possible reduces the contact of the allograft with subcutaneous tissues and,
we believe, reduces the risk of infection. We emphasize that we do not flex
the repair once it is completed, as has been recommended by other authors.
Preparation of the Host Proximal Tibial Trough
Using a marking pen, we mark out the host proximal tibial trough
(Fig. 15). We typically
attempt to place the allograft tibial tubercle in a position that is close to,
or slightly medial to, the position of the native tibial tubercle. In
addition, we attempt to leave at least 15 mm of host bone intact below the
tibial component anteriorly to resist proximal migration or escape of the
graft, although this 15 mm of bone is not always possible in the revision
setting with associated bone loss. The rectangular tibial trough is then
marked out for a length of 5 cm and a width of just less than 2 cm and a depth
of 2 cm. Proximally, the host bone is beveled
(Fig. 16) to accept a
press-fit of the beveled, or dovetailed, allograft bone block
(Fig. 17). This bevel in the
host bone should be created with dimensions slightly smaller than the
allograft bone block, in order to allow a pressfit
(Fig. 18). Two or three
18-gauge stainless steel wires are then placed through drill-holes in the
tibia from medial to lateral (Fig.
19). These wires must pass deep to the tibial trough. If a stemmed
tibial component is being used, it is easier to drill and place these wires
prior to inserting the stemmed component. The allograft extensor mechanism is
then inserted into the host tibial trough and is gently press-fit with a bone
tamp or punch, in an "up and in" fashion, in order to lock the
dovetail in place. The wires are then twisted, tightened, cut, and bent over
against bone to avoid irritation to the soft tissues
(Fig. 20). Alternatively, a
small-fragment cortical screw and washer may be added to the fixation at the
surgeon's preference. This creates a drill-hole in the allograft, and we
prefer to avoid this stressriser, despite the added security of the screw
fixation.
Once we have secured the allograft bone into the host tibia, attention is
turned to the proximal quadriceps medial and lateral sleeves and
retinaculum.
Preparation and Tensioning of the Host Distal Quadriceps
Similar to the retention sutures placed in the allograft quadriceps, the
host distal quadriceps medial and lateral soft-tissue sleeves are prepared. We
again use a number-2 nonabsorbable suture (FiberWire; Arthrex, Naples,
Florida) and place a short running Krakow suture into both the medial and
lateral retinaculum in the distal quadriceps muscle-tendon junction. This
allows a second assistant to "pull down" the host quadriceps
mechanism (Fig. 21),
effectively tensioning the distal host extensor mechanism
(Fig. 22). The two previously
placed allograft quadriceps sutures are pulled tightly with the knee in full
extension (Figs. 23-A and
23-B). With use of a suture
passer, these sutures are then pulled from distal to proximal, out and up
through the more proximal host quadriceps. This pulls the allograft quadriceps
up and under the host quadriceps, and simultaneously pulls or tensions the
host quadriceps distally (Fig.
24). With this tension maintained, the allograft is then sutured
in place beneath the host quadriceps with number-5 nonabsorbable suture, in a
"vest-over-pants" fashion (see
Fig. 24). Throughout this
suture repair, the two assistants maintain tension on their respective
retention sutures, in order to maintain tension with the knee in the extended
position. Once the proximal aspect of the allograft is secured, the repair is
continued along the medial and lateral sides. However, the repair is performed
with the host retinaculum brought over the top of the allograft, in order to
cover the allograft tissues as much as possible with the medial and lateral
sleeves of the host retinaculum. We find that we are usually able to
completely cover the allograft with these host sleeves that have been
preserved, in addition to suturing the allograft underneath these tissues
(Fig. 25). Distally, the host
tissues are closed over the wires and allograft bone block.