Sizing and Inspection of Meniscal Transplants
Anteroposterior and lateral radiographs are used to measure the approximate
width and length of the meniscal
transplant1. The
surgeon should have knowledge of the donor-selection criteria and
tissue-processing procedures of the tissue bank as these may vary
substantially, even among tissue banks that are certified by the American
Association of Tissue Banks and that follow the guidelines of the United
States Food and Drug Administration. The implications of different processing
techniques with regard to graft sterility are
important2-4
but beyond the scope of this report.
We advise the surgeon to request that the tissue bank provide, well before
the surgery, a photograph of the transplant that has been selected for each
patient. A metric ruler should be placed adjacent to the transplant in the
photograph to ensure that the allograft is of adequate size and width. The
surgeon should also be aware that certain medial menisci have a hypoplastic
anterior horn that is narrow, inserting distal to the medial tibial surface
(Type III5), and
that these menisci are not acceptable for implantation. Also, if the middle
one-third of a medial or lateral meniscus is 8 to 10 mm in width, it is
suitable only for small patients. In addition, if the lateral meniscus has
reduced anteroposterior length, less than that calculated on the sagittal
radiograph, it is not suitable for implantation.
The meniscus is thawed, inspected, and prepared prior to the administration
of the anesthesia because it is difficult to detect implant defects through
the plastic packaging. The implant is also prepared first so that the surgeon
can determine the depth and width required for the tibial slot when the
central bone-bridge technique is selected.
Technique for Lateral Meniscal Transplantation
Preparation
The lateral meniscus, with the anterior and posterior horns remaining
attached centrally to bone, is a better transplant than the medial meniscus.
Because the attachment sites and circumference tension relationships are not
disturbed, an arthroscopically assisted tibial slot
method2 of
attachment can be performed with a meticulous inside-out meniscal
repair6. The central
bone portion of the transplant incorporates the anterior and posterior
meniscal attachments and usually measures 8 to 9 mm in width, 35 mm in length,
and 10 mm in depth. The posterior 8 to 10 mm of bone that protrudes beyond the
posterior horn attachment is removed to later produce a buttress against the
bone trough in the host knee. Commercially available sizing blocks and channel
cutters (Stryker Endoscopy, Kalamazoo, Michigan, and CryoLife, Kennesaw,
Georgia) allow appropriate sizing.
Surgical Technique
The patient is placed in a supine position on the operating room table,
with a tourniquet applied with a leg-holder and the table adjusted to allow
90° of knee flexion. The contralateral lower extremity is placed in a
thigh-high elastic stocking and is padded to maintain mild hip flexion to
decrease tension on the femoral nerve. After examination with the patient
under anesthesia, diagnostic arthroscopy is done to confirm the preoperative
diagnosis and to assess changes in the articular cartilage. An
arthroscopically assisted approach is used in knees that require a cruciate
ligament
reconstruction7. The
femoral and tibial tunnels are drilled, and the ligament graft is passed
through the tunnels, with femoral fixation done first, followed by the
meniscal transplantation, and then by tibial fixation of the cruciate graft.
Fixing the ligament graft at the tibia as the final step allows maximum
separation of the tibiofemoral joint during meniscal transplantation. It also
prevents failure or problems with the ligament fixation or ligament graft
during the operation.
A limited 3-cm lateral arthrotomy is made just adjacent to the patellar
tendon. Although there are arthroscopic techniques for preparation of the
tibial slot, we believe that the limited arthrotomy provides superior
visualization and makes it possible to avoid incision into the patellar
tendon. A second, 3-cm posterolateral accessory incision is made, centered
just behind the lateral collateral ligament
(Fig.
1-A)6,8.
The interval between the biceps tendon insertion and the iliotibial band is
identified and incised (Fig.
1-B). The lateral head of the gastrocnemius is gently dissected
with Metzenbaum scissors off of the posterior aspect of the capsule at the
joint line (Fig. 1-C). Care is
taken at this point because dissection that extends too far proximal to the
joint line at the posterolateral aspect would enter the joint capsule. If this
occurs, a capsular repair is required to maintain joint integrity during the
inside-out meniscal repair. The lateral inferior genicular artery is also in
close proximity, and it is identified and preserved. The space between the
posterolateral aspect of the capsule and the lateral head of the gastrocnemius
is further developed bluntly. An appropriately sized popliteal retractor
(Stryker) is placed directly behind the lateral meniscal bed. The tourniquet
is inflated only for these two approaches; otherwise, it is not used.
CRITICAL CONCEPTSINDICATIONS:The indications for a meniscal allograft procedure are
prior meniscectomy, an age of fifty years or less, pain in the tibiofemoral
compartment, no radiographic evidence of advanced arthrosis, and =2 mm of
tibiofemoral joint space as seen on 45° weight-bearing posteroanterior
radiographs10.CONTRAINDICATIONS:Contraindications include advanced arthrosis of
the knee joint with flattening of the femoral condyle, concavity of the tibial
plateau, and osteophytes that prevent anatomic seating of the meniscal
allograft11; axial
varus malalignment in which a weight-bearing line of <40% of the
medial-lateral transverse width of the tibial
plateau12 is seen
on radiographs or valgus malalignment in which a weight-bearing line of
>60% is seen on radiographs; instability of the knee joint or the patient's
refusal to undergo concomitant knee ligament reconstruction; knee
arthrofibrosis; muscular atrophy; and previous joint infection.PITFALLS:The patient is informed that the transplant is inspected just before the
surgical procedure in the operating room and that the decision to proceed with
the procedure will be made at this time if the graft is deemed suitable. Also,
there is the remote possibilty that, during the operative procedure, either
the final preparation or the implantation of the meniscal allograft may not be
possible as a result of problems with its size or the ability to obtain
correct positioning in the joint.The preparation of the meniscal template is critical for successful
placement of the final tibial slot and correct positioning of the transplant.
The aluminum foil template is made to represent the size of the implant and is
inserted through the limited anterior arthrotomy incision.The slot placement for the latera or medial meniscal transplant must be
exact. Otherwise, the meniscus may be displaced at its midportion outside the
joint, or it may be positioned too far inside the joint and subsequently incur
excessive compression and tearing. It is possible to realign the bone trough a
few millimeters medially or laterally in the coronal plane, and an absorbable
interference screw can be used for fixation in the final coronal adjustment of
the implant.During medial meniscal transplantation, the template may indicate that the
transplant is excessively wide in the medial-to-lateral direction. If it does,
the middle one-third of the transplant would rest outside of the medial tibial
plateau in order to avoid compromising the attachment of the anterior cruciate
ligament. The two-tunnel technique is selected to obtain correct anatomic
positioning and the desired subsequent circumferential hoop stress.The use of multiple vertical divergent sutures is required to position the
transplant in the anatomically correct manner. There are usually wavy areas in
the implant, with loss of circumferential tension, that are successfully
removed by correct placement of these sutures.We prefer the inside-out meniscal repair technique, which is considered to
be the most precise suturing method.We avoid meniscal fixators, with which it is not possible to provide the
same secure fit and exact placement of the implant.The sutures should not be placed in the middle and inner thirds of the
meniscus, as this could weaken the implant.The suturing of the implant is meticulous, as twelve to fifteen sutures are
required both superiorly and inferiorly, all placed in a vertical direction.
Horizontal sutures have poor holding ability and are therefore not used during
meniscal transplantation.Care is taken not to damage the articular cartilage. The technique requires
two surgical assistants, one dedicated to holding the lower limb to open the
medial or lateral tibiofemoral compartment for visualization of the implant
and the other seated to retrieve and tie the sutures at the posterior aspect
of the joint.The suturing of the medial or lateral posterior horn adjacent to the
posterior attachment requires angulation of the suture needle away from the
neurovascular structures.In order for the meniscal transplant to function, it must be placed at the
normal anatomic insertion sites. If the posterior horn attachment of the
medial or lateral meniscus is placed too far posteriorly, it will not provide
proper
load-sharing13.
Alternatively, a too anterior position of a medial meniscal transplant will
produce excessive compressive forces and damage the meniscus.We disagree with those who have advocated techniques of medial meniscal
transplantation in which the posterior bone portion of a medial meniscal
implant is not retained and the fibrocartilaginous posterior horn is placed in
a posterior tibial attachment tunnel. Although such transplants are far easier
to prepare and implant surgically, there are inadequate scientific data to
support the belief that the soft-tissue ends of the meniscal implant (without
the bone attachment) will heal and provide the circumferential tension in the
meniscus that is required for function.AUTHOR UPDATE:In our original study, we used the central bone-bridge technique, which
maintains a central bone bridge between the anterior and posterior meniscal
attachments, primarily for lateral meniscal transplantation. This is also now
our preferred technique for medial meniscal transplantation, as described in
this article.Currently, we use a template of the meniscal implant to determine the
location of the bone slot. The lateralmost placement of the central bone slot
for the medial meniscal implant is limited by the tibial attachment of the
anterior cruciate ligament. The anterior horn of the medial meniscus must not
be of a Type-III
configuration5—i.e.,
it must not insert too far distally on the anterior tibial margin. If
assessment of the medial meniscal transplant reveals a medial-to-lateral size
mismatch, then separate anterior and posterior bone attachments and tunnels
are required. The posterior part of the bone-meniscus transplant is placed at
the normal attachment, and the anterior horn is placed in a medial-to-lateral
direction to restore correct tensioning and position in the joint.For tight knees with only a few millimeters of medial joint opening, the
central bone-bridge technique enables the surgeon to avoid performing a
partial detachment of the distal part of the medial collateral ligament, which
would otherwise be required to gain access to the joint for suturing and to
avoid damage to the articular cartilage.There are now newer techniques for tissue-processing and advanced
donor-screening tests that provide highly safe meniscal transplants with an
exceedingly low risk of disease transmission. Advances in tissue-processing
and Food and Drug Administration guidelines for tissue banks are important to
ensure the safety of allografts.
CRITICAL CONCEPTS
INDICATIONS:The indications for a meniscal allograft procedure are
prior meniscectomy, an age of fifty years or less, pain in the tibiofemoral
compartment, no radiographic evidence of advanced arthrosis, and =2 mm of
tibiofemoral joint space as seen on 45° weight-bearing posteroanterior
radiographs10.
CONTRAINDICATIONS:
Contraindications include advanced arthrosis of
the knee joint with flattening of the femoral condyle, concavity of the tibial
plateau, and osteophytes that prevent anatomic seating of the meniscal
allograft11; axial
varus malalignment in which a weight-bearing line of <40% of the
medial-lateral transverse width of the tibial
plateau12 is seen
on radiographs or valgus malalignment in which a weight-bearing line of
>60% is seen on radiographs; instability of the knee joint or the patient's
refusal to undergo concomitant knee ligament reconstruction; knee
arthrofibrosis; muscular atrophy; and previous joint infection.
PITFALLS:
The patient is informed that the transplant is inspected just before the
surgical procedure in the operating room and that the decision to proceed with
the procedure will be made at this time if the graft is deemed suitable. Also,
there is the remote possibilty that, during the operative procedure, either
the final preparation or the implantation of the meniscal allograft may not be
possible as a result of problems with its size or the ability to obtain
correct positioning in the joint.The preparation of the meniscal template is critical for successful
placement of the final tibial slot and correct positioning of the transplant.
The aluminum foil template is made to represent the size of the implant and is
inserted through the limited anterior arthrotomy incision.The slot placement for the latera or medial meniscal transplant must be
exact. Otherwise, the meniscus may be displaced at its midportion outside the
joint, or it may be positioned too far inside the joint and subsequently incur
excessive compression and tearing. It is possible to realign the bone trough a
few millimeters medially or laterally in the coronal plane, and an absorbable
interference screw can be used for fixation in the final coronal adjustment of
the implant.During medial meniscal transplantation, the template may indicate that the
transplant is excessively wide in the medial-to-lateral direction. If it does,
the middle one-third of the transplant would rest outside of the medial tibial
plateau in order to avoid compromising the attachment of the anterior cruciate
ligament. The two-tunnel technique is selected to obtain correct anatomic
positioning and the desired subsequent circumferential hoop stress.The use of multiple vertical divergent sutures is required to position the
transplant in the anatomically correct manner. There are usually wavy areas in
the implant, with loss of circumferential tension, that are successfully
removed by correct placement of these sutures.We prefer the inside-out meniscal repair technique, which is considered to
be the most precise suturing method.We avoid meniscal fixators, with which it is not possible to provide the
same secure fit and exact placement of the implant.The sutures should not be placed in the middle and inner thirds of the
meniscus, as this could weaken the implant.The suturing of the implant is meticulous, as twelve to fifteen sutures are
required both superiorly and inferiorly, all placed in a vertical direction.
Horizontal sutures have poor holding ability and are therefore not used during
meniscal transplantation.Care is taken not to damage the articular cartilage. The technique requires
two surgical assistants, one dedicated to holding the lower limb to open the
medial or lateral tibiofemoral compartment for visualization of the implant
and the other seated to retrieve and tie the sutures at the posterior aspect
of the joint.The suturing of the medial or lateral posterior horn adjacent to the
posterior attachment requires angulation of the suture needle away from the
neurovascular structures.In order for the meniscal transplant to function, it must be placed at the
normal anatomic insertion sites. If the posterior horn attachment of the
medial or lateral meniscus is placed too far posteriorly, it will not provide
proper
load-sharing13.
Alternatively, a too anterior position of a medial meniscal transplant will
produce excessive compressive forces and damage the meniscus.We disagree with those who have advocated techniques of medial meniscal
transplantation in which the posterior bone portion of a medial meniscal
implant is not retained and the fibrocartilaginous posterior horn is placed in
a posterior tibial attachment tunnel. Although such transplants are far easier
to prepare and implant surgically, there are inadequate scientific data to
support the belief that the soft-tissue ends of the meniscal implant (without
the bone attachment) will heal and provide the circumferential tension in the
meniscus that is required for function.
The patient is informed that the transplant is inspected just before the
surgical procedure in the operating room and that the decision to proceed with
the procedure will be made at this time if the graft is deemed suitable. Also,
there is the remote possibilty that, during the operative procedure, either
the final preparation or the implantation of the meniscal allograft may not be
possible as a result of problems with its size or the ability to obtain
correct positioning in the joint.
The preparation of the meniscal template is critical for successful
placement of the final tibial slot and correct positioning of the transplant.
The aluminum foil template is made to represent the size of the implant and is
inserted through the limited anterior arthrotomy incision.
The slot placement for the latera or medial meniscal transplant must be
exact. Otherwise, the meniscus may be displaced at its midportion outside the
joint, or it may be positioned too far inside the joint and subsequently incur
excessive compression and tearing. It is possible to realign the bone trough a
few millimeters medially or laterally in the coronal plane, and an absorbable
interference screw can be used for fixation in the final coronal adjustment of
the implant.
During medial meniscal transplantation, the template may indicate that the
transplant is excessively wide in the medial-to-lateral direction. If it does,
the middle one-third of the transplant would rest outside of the medial tibial
plateau in order to avoid compromising the attachment of the anterior cruciate
ligament. The two-tunnel technique is selected to obtain correct anatomic
positioning and the desired subsequent circumferential hoop stress.
The use of multiple vertical divergent sutures is required to position the
transplant in the anatomically correct manner. There are usually wavy areas in
the implant, with loss of circumferential tension, that are successfully
removed by correct placement of these sutures.
We prefer the inside-out meniscal repair technique, which is considered to
be the most precise suturing method.
We avoid meniscal fixators, with which it is not possible to provide the
same secure fit and exact placement of the implant.
The sutures should not be placed in the middle and inner thirds of the
meniscus, as this could weaken the implant.
The suturing of the implant is meticulous, as twelve to fifteen sutures are
required both superiorly and inferiorly, all placed in a vertical direction.
Horizontal sutures have poor holding ability and are therefore not used during
meniscal transplantation.
Care is taken not to damage the articular cartilage. The technique requires
two surgical assistants, one dedicated to holding the lower limb to open the
medial or lateral tibiofemoral compartment for visualization of the implant
and the other seated to retrieve and tie the sutures at the posterior aspect
of the joint.
The suturing of the medial or lateral posterior horn adjacent to the
posterior attachment requires angulation of the suture needle away from the
neurovascular structures.
In order for the meniscal transplant to function, it must be placed at the
normal anatomic insertion sites. If the posterior horn attachment of the
medial or lateral meniscus is placed too far posteriorly, it will not provide
proper
load-sharing13.
Alternatively, a too anterior position of a medial meniscal transplant will
produce excessive compressive forces and damage the meniscus.
We disagree with those who have advocated techniques of medial meniscal
transplantation in which the posterior bone portion of a medial meniscal
implant is not retained and the fibrocartilaginous posterior horn is placed in
a posterior tibial attachment tunnel. Although such transplants are far easier
to prepare and implant surgically, there are inadequate scientific data to
support the belief that the soft-tissue ends of the meniscal implant (without
the bone attachment) will heal and provide the circumferential tension in the
meniscus that is required for function.
AUTHOR UPDATE:
In our original study, we used the central bone-bridge technique, which
maintains a central bone bridge between the anterior and posterior meniscal
attachments, primarily for lateral meniscal transplantation. This is also now
our preferred technique for medial meniscal transplantation, as described in
this article.
Currently, we use a template of the meniscal implant to determine the
location of the bone slot. The lateralmost placement of the central bone slot
for the medial meniscal implant is limited by the tibial attachment of the
anterior cruciate ligament. The anterior horn of the medial meniscus must not
be of a Type-III
configuration5—i.e.,
it must not insert too far distally on the anterior tibial margin. If
assessment of the medial meniscal transplant reveals a medial-to-lateral size
mismatch, then separate anterior and posterior bone attachments and tunnels
are required. The posterior part of the bone-meniscus transplant is placed at
the normal attachment, and the anterior horn is placed in a medial-to-lateral
direction to restore correct tensioning and position in the joint.
For tight knees with only a few millimeters of medial joint opening, the
central bone-bridge technique enables the surgeon to avoid performing a
partial detachment of the distal part of the medial collateral ligament, which
would otherwise be required to gain access to the joint for suturing and to
avoid damage to the articular cartilage.
There are now newer techniques for tissue-processing and advanced
donor-screening tests that provide highly safe meniscal transplants with an
exceedingly low risk of disease transmission. Advances in tissue-processing
and Food and Drug Administration guidelines for tissue banks are important to
ensure the safety of allografts.
The width of the transplant is determined, and an aluminum foil template of
the same width and length as the transplant is cut and is inserted into the
lateral compartment to determine the lateralmost margin of the bone trough.
This sizing step is important to make sure that there is no lateral overhang
of the meniscal body produced by placing the bone trough too far laterally. A
rectangular bone trough is prepared at the anterior and posterior tibial
attachment sites of the lateral meniscus to match the dimensions of the
prepared lateral meniscal transplant. The sequence of steps to prepare the
lateral tibial slot is illustrated in Figures
2-A,2-B,
2-C,
2-D. The tibial bone slot is 1
to 2 mm wider than the transplant, to facilitate implantation. The anterior
and posterior horns of the implant are placed into their normal attachment
locations, adjacent to the anterior cruciate ligament. The allograft is
inserted into the trough (Fig.
2-E), and the bone portion of the graft is seated against the
posterior bone buttress to achieve correct anterior-to-posterior placement of
the attachment sites. A vertical suture in the posterior part of the meniscal
body is passed posteriorly to provide tension and facilitate implant
placement. The knee is flexed, extended, and rotated to confirm correct
allograft placement. The posterior suture is tied, and sutures are placed in a
vertical fashion into the anterior one-third of the meniscus, attaching it to
the prepared meniscal rim under direct visualization.
An alternative technique is to use a starter chisel and finishing chisels
to fashion the tibial trough to its final depth and width
(Fig. 3-A). A tibial trough
sizing guide is employed to check the length and depth
(Fig. 3-B). The allograft
sizing block (Fig. 3-C)
confirms that the allograft bone bridge is of the correct width and depth.
Two methods are available for fixation of the central bone attachment. Two
2-0 nonabsorbable sutures (Ticron [Davis and Geck, Wayne, New Jersey] or
Ethibond [Ethicon, Somerville, New Jersey]) may be placed in the central
region, brought through a drill hole, and tied. Our preferred method involves
placement of an interference screw (7 × 25 mm), made of an absorbable
composite material, medial and adjacent to the central bone
attachment9. The
arthrotomy is closed, and the inside-out meniscal repair is performed with
multiple vertical divergent sutures, which are placed first superiorly to
reduce the meniscus (Fig. 4)
and then inferiorly in the outer one-third of the implant. Sutures are not
placed in the middle and inner thirds of the meniscus to avoid weakening the
implant, which has a limited healing capability in these regions
(Fig. 5).
Technique for Medial Meniscal Transplantation
Preparation
The medial meniscal transplant is inspected to confirm that the size is
appropriate and no degenerative changes are present. The implant is not
prepared until it is decided whether the central bone-bridge technique (which
is preferred) or the two-tunnel technique (involving separate anterior and
posterior bone attachments and tunnels) is required.
The patient is placed in a supine position on the operating room table,
with a tourniquet applied with a leg-holder and the table adjusted to allow
90° of knee flexion. The contralateral lower extremity is placed in a
thigh-high elastic stocking and is padded to maintain mild hip flexion to
decrease tension on the femoral nerve. After examination with the patient
under anesthesia, diagnostic arthroscopy is done to confirm the preoperative
diagnosis and assess changes in the articular cartilage.
A 4-cm skin incision is made on the anterior aspect of the tibia adjacent
to the tibial tubercle and the patellar tendon. A second, 3-cm vertical
posteromedial incision, similar to that described for inside-out meniscal
repairs8, is made
just posterior to the superficial medial collateral ligament
(Fig. 6-A). The fascia is
incised anterior to the sartorius (Fig.
6-B), and the pes anserinus muscle group is retracted posteriorly.
The interval between the semi-membranosus tendon and the capsule is sharply
dissected. The layer between the medial aspect of the gastrocnemius tendon and
the posteromedial aspect of the capsule is separated with blunt dissection
(Fig. 6-C). Great care is
taken to identify and avoid injury to the infrapatellar branches of the
saphenous nerve. The two approaches are performed with the tourniquet inflated
to 275 mm Hg and usually require fifteen minutes; otherwise, the tourniquet is
not used.
A medial meniscal transplant, with anatomically placed anterior and
posterior bone attachments, must be appropriately secured to maintain the
desired position in the knee joint postoperatively and to provide the
circumferential tension required for transplant function. A template of the
medial meniscal transplant, made of aluminum foil and measured according to
its anterior-posterior and medial-lateral dimensions, is inserted through the
limited anterior arthrotomy incision and is sized to the medial tibial
plateau. This allows the surgeon to mark the position of the central bone
trough and to determine whether the meniscal implant will be properly
positioned just adjacent to the tibial attachment of the anterior cruciate
ligament, without excessive medial tibial overhang. Next, it is verified that
the anterior and posterior attachments are located at the anatomically correct
sites. With the central bone-bridge technique, 4 to 6 mm of the medial tibial
eminence is removed. If the implant is suitable and there is no medial tibial
overhang, then the central bone-bridge technique may be used. If the implant
needs to be adjusted to fit to the medial tibial plateau by moving the
anterior horn farther laterally, then the two-tunnel technique is selected.
Once the technique has been chosen, the meniscal allograft is prepared.
Central Bone-Bridge Technique
The central bone-bridge technique for medial meniscal transplantation is
the same as that described for lateral meniscal transplantation. A reference
slot is first created on the tibial plateau in the anteroposterior direction.
A guide pin is positioned in the slot, inferiorly on the tibia, and a
cannulated drill bit is placed over the pin to drill a tunnel. The final
tibial slot is 8 to 9 mm in width and 10 mm in depth. A rasp is used to smooth
the slot to allow insertion of the central bone bridge of the allograft.
The central bone bridge of the allograft is sized to a width of 7 mm (1 mm
less than the dimension at the tibial site) and a depth of 10 mm9.
This allows the position of the central bone bridge to be adjusted in the
anterior-posterior direction while the meniscus is positioned to fit in the
anatomically correct position relative to the femoral condyle.
A vertical suture is placed through the junction of the posterior and
middle thirds of the meniscus. A single-barrel cannula is used to advance the
suture through the capsule at the corresponding attachment site of the
meniscus, and the suture exits through an accessory incision
(Fig. 7). The meniscus is
passed through the arthrotomy incision into the knee, with tension placed on
the sutures to facilitate proper positioning in the knee joint. Care is taken
to align the bone bridge with the recipient tibial slot. The knee is taken
through flexion and extension and tibial rotation to align the implant. Once
the appropriate anterior-posterior position of the central bone bridge is
achieved, a guide wire is inserted between the bone bridge and the lateral
side of the slot. A tap is inserted over the guide wire to create a path for
an interference screw with the bone bridge held in place manually. An
absorbable bone interference screw is inserted adjacent to the bone
bridge.
The joint is again taken through a full range of motion, and the position
of the implant is verified. Occasionally, there is an osteophyte on the
anterior aspect of the medial tibial plateau, and this must be resected to
avoid compression of the meniscal implant. The central bone bridge of the
implant is fixed with an interference screw (7 × 25 mm). The meniscus is
sutured with vertical divergent sutures (2-0 Ethibond) under direct
visualization. The anterior arthrotomy is closed, and the inside-out vertical
divergent sutures are placed, as described, to sew the meniscus to the
meniscal bed, with removal of any implant undulations and restoration of
circumferential meniscal tension. The central bone bridge of the implant
provides fixation of the anterior and posterior portions of the implant and
healing into the host tibia (Fig.
8).
Two-Tunnel Technique
If it is determined that the central bone-bridge technique is not
acceptable, the surgeon must prepare separate anterior and posterior bone
portions of the meniscal transplant. Both are secured to anatomic attachment
sites to provide a functional meniscal implant
(Fig. 9). The transplant is
prepared with a posterior bone plug, 8 mm in diameter and 12 mm in length, and
an anterior bone plug, 12 mm in diameter and 12 mm in length. Two 2-0
nonabsorbable Ethibond sutures are passed retrograde through each bone plug,
with two additional locking sutures placed in the meniscus adjacent to the
bone attachment for subsequent secure fixation of the bone plugs within the
tibial tunnel.
A guide pin is placed adjacent to the tibial tubercle and is directed to
the anatomic posterior meniscal attachment. A tibial tunnel is drilled over
the guide wire to a diameter of 8 mm. The bone-tunnel edges are chamfered. A
limited notchplasty of the medial femoral condyle is usually required. At
least 8 mm of opening adjacent to the posterior cruciate ligament in the
femoral notch is needed to pass the posterior osseous portion of the graft. On
occasion, a subperiosteal release of the long fibers of the tibial attachment
of the medial collateral ligament (with later suture-anchor repair) is
required to open the medial part of the tibiofemoral joint sufficiently. The
meniscal bed is prepared by removing any remaiing meniscal tissue while
preserving a 3-mm rim when possible. The meniscal bed is rasped for
revascularization of the graft.
A 3-cm anteromedial arthrotomy is used to pass the posterior bone portion
of the graft, with a secondary meniscal body suture passed out through the
incision for the posteromedial approach. The surgeon is seated with a
headlight in place, and the patient's knee is flexed to 90°. On occasion,
there are anterior osteophytes on the medial tibial plateau that require
resection. The posterior attachment guide wire is retrieved, and the sutures
attached to the posterior bone are passed. A second suture is placed into the
midportion of the meniscus and is passed insideout through the incision for
the posteromedial approach to guide the meniscus.
The knee is flexed to 20° under a maximum valgus load to pass the
posterior bone portions of the graft, with the secondary meniscal body suture
held by an assistant. A nerve hook is used to gently assist the passage of the
graft. With use of a headlight and retractors, it is possible to confirm
appropriate passage of the meniscal graft into the medial tibiofemoral
compartment. Care is taken to not advance the posterior part of the meniscal
body into the tibial tunnel but to only seat the bone portion of the graft in
order to avoid shortening of the meniscal graft. The posterior meniscal bone
attachment and the midbody sutures are tied over the tibial post to provide
tension in the posterior bone attachment and the posterior one-third of the
meniscus. The knee is flexed and extended to assess meniscal fit and
displacement. The optimal location for the anterior meniscal bone attachment
at the anteromedial junction of the tibial plateau is identified, with the
medial-to-lateral placement in the coronal plane determined with the knee in
full extension. A 12-mm rectangular bone attachment is fashioned to correspond
to the anterior bone portion of the meniscal graft. A 4-mm bone tunnel is
placed at the base of this bone trough, and it exits at the anterior aspect of
the tibia just proximal to the posterior bone tunnel. The sutures are passed
through the bone tunnel, and the anterior horn is seated. Full knee flexion
and extension are again performed to determine proper graft placement and fit.
Tension is applied to the anterior bone sutures, which are not tied at this
point but are used to maintain tension in the graft during the inside-out
suture repair. This meticulous seating of the meniscal transplant under
circumferential tension with bone attachment of both the anterior and the
posterior horn is believed to be crucial for future meniscal weight-bearing
position and function.
The anterior arthrotomy is closed, and the arthroscope is inserted into the
anterolateral portal for the posterior meniscal repair and into the
anteromedial portal for the repairs of the middle and anterior one-thirds,
with the single needle cannula inserted in the other anterior portal. The
meniscal repair is performed in an inside-out fashion, starting with the
posterior horn, with use of multiple vertical divergent sutures of 2-0
non-absorbable Ethibond both superiorly and inferiorly, with constant
tensioning of the meniscus from posterior to anterior to establish
circumferential tension. The assistant, seated with a headlight, retrieves the
suture needles through the posteromedial approach. Each suture is placed and
tied, bringing the meniscus directly to the meniscal bed with observation that
meniscal placement, fixation, and tension are correct. The anterior arthrotomy
incision is again opened, and the final tensioning and tying of the anterior
horn bone sutures are performed with use of the anterior tibial post.
Occasionally, additional sutures are required to secure the most anterior
one-third of the meniscus to the capsular attachments, which is done under
direct vision (Fig. 10). After
final inspection of the graft with knee flexion and extension and tibial
rotation, the operative wounds are closed in a routine fashion.