Allograft Selection
Fresh-frozen allografts are obtained and stored according to a previously
described
technique7. Poor
anatomical matching in terms of both size and shape between the host defect
and the graft can substantially alter joint kinematics and load distribution,
leading to bone resorption or joint degeneration. To improve the accuracy in
size matching between the donor and the host, we developed measurable
parameters on the basis of computed tomography
scans7. On the axial
view of the distal part of the femur, we determine the maximum total width and
anteroposterior dimension of the medial and lateral condyles
(Fig. 1) and the width of the
intercondylar notch. In the proximal part of the tibia, the maximum total
width and the anteroposterior width of the medial and lateral plateaus are
measured (Fig. 2). These
measurements are available in our hospital bone bank and facilitate selection
of the best graft to match the patient. The allograft selection is based on a
comparison of these parameters with those of the donor.
Unicondylar Osteoarticular Allograft of the Distal Part of the
Femur
Preoperative imaging includes magnetic resonance imaging and computed
tomography as necessary to define the margins of the lesion and the intended
resection (Figs. 3 and
4). All operations are
performed in a cleanair enclosure with vertical airflow and usually with
spinal anesthesia. The patient is placed on the operating table in the supine
position. A sandbag is placed under the ipsilateral buttock. A long midline
skin incision is made, beginning in the middle part of the thigh, and a medial
parapatellar arthrotomy is performed in a manner similar to that of a total
knee replacement. The distal part of the femur is approached through the
interval between the rectus femoris and the vastus medialis. The patella is
then everted, and the knee is flexed to expose the joint
(Fig. 5). The cruciate and
collateral ligaments of the affected condyle (that is, the anterior cruciate
and lateral collateral ligaments for the lateral condyle and the posterior
cruciate and medial collateral ligaments for the medial condyle) are
identified (Figs. 6 and
7) and are sectioned close to
their femoral attachments to ensure presentation of sufficient length to allow
reattachment to the donor. If there is an extraosseous tumor component, a cuff
of normal muscle must also be excised. A femoral osteotomy is performed at the
appropriate location on the basis of preoperative imaging studies. The
longitudinal limb of the osteotomy is performed parallel to the long axis of
the femur, and the transverse limb is performed perpendicular to the axis of
the shaft, in order to preserve the unaffected condyle
(Fig. 8). Simultaneously with
the tumor resection, the allograft specimen is prepared on the back table. The
graft is taken out of the plastic packaging and is placed directly in warm
normal saline solution. After being thawed, the donor bone is cut to the
proper dimensions (Fig. 9) and
the soft-tissue structures, such as the cruciate and collateral ligaments, are
prepared for implantation and reattachment. It is critical that adequate
soft-tissue structures remain on the allograft so that they can be sutured to
their counterparts on the host. After resection of the tumor, the distal
femoral allograft is inspected to confirm the appropriate size and the absence
of degenerative changes. The allograft segment is then tailored to fit the
bone defect. Precise apposition between the allograft and the host bone is
critical. Distal or proximal malpositioning would lead to offset of the
articular surface and inappropriate loading of the affected compartment, with
a resulting varus or valgus deformity. When a satisfactory reduction has been
obtained, the graft is provisionally secured with threaded Kirschner wires
that are inserted through the distal part of the condyle. The graft is then
stabilized by means of internal fixation with cancellous screws compressing
the metaphyseal bone. A plate is applied to fix the diaphyseal osteotomy site;
in order to minimize the risk of fracture, it should span as much allograft
length as possible (Fig. 10).
Once the allograft has been secured to the host bone, the knee is flexed to
allow soft-tissue reconstruction of the joint
(Fig. 11). We use a number-1
nonabsorbable suture to repair the native cruciate ligament (the anterior
cruciate ligament for the lateral condyle and the posterior cruciate ligament
for the medial condyle) to the corresponding cruciate tissues provided by the
allograft. Finally, the corresponding collateral ligament (the lateral
collateral ligament for the lateral condyle and the medial collateral ligament
for the medial condyle) is repaired in similar fashion (Figs.
12,
13, and
14). The patella is reduced,
if it was not originally detached, by suturing the capsule and parapatellar
tendons. Two suction drains are inserted, and, after lavage of the wound with
saline solution, the quadriceps is meticulously repaired. A layered closure of
the subcutaneous tissues and skin is then performed. Prophylactic antibiotics
are given intravenously according to a standard protocol, and anticoagulation
therapy is routinely employed.
Unicondylar Osteoarticular Allograft of the Proximal Part of the
Tibia
The same basic principles are applied for unicondylar osteoarticular
allograft reconstruction of the proximal part of the tibia (Figs.
15 and
16). A long midline incision
is made, beginning at the upper pole of the patella. The incision is extended
over the tibia, and a medial or lateral parapatellar arthrotomy is performed,
depending on which tibial condyle is affected. Such an incision provides a
wide exposure of the proximal part of the tibia and the knee joint
(Fig. 17). The biopsy track is
removed in continuity with the specimen. The proximal part of the tibia is
exposed extraperiosteally, and a cuff of normal muscle is excised as a margin
around any extraosseous component of the tumor. The osteotomy is planned at
the appropriate location as determined on preoperative imaging studies. Both
cruciate ligaments and the patellar tendon are identified and are left
attached to the unaffected tibial condyle. The meniscus of the affected
condyle is detached and is preserved with the host. Regarding the collateral
ligaments, only when the medial tibial condyle is involved must the medial
collateral ligament be detached, but when the lateral tibial condyle is
reconstructed the lateral collateral ligament remains intact with the fibula
(Fig. 18). After resection of
the tumor, the allograft is tailored to fit into the bone defect
(Fig. 19). After the donor
bone is thawed in a warm solution, it is cut to the proper dimensions and is
inserted into the defect (Figs.
20 and
21). The graft is temporarily
secured with threaded Kirschner wires that are placed through the proximal
part of the tibial plateau, and the graft is then stabilized by means of
internal fixation. A plate is applied across the diaphyseal osteotomy site,
and, in order to minimize the risk of fracture, it should span as much
allograft length as possible (Fig.
22). Once the allograft bone has been secured to the host, the
knee is flexed to allow soft-tissue reconstruction of the joint. The host
meniscus is reattached with a number-1 nonabsorbable suture to the
osteoarticular allograft by securing the perimeter of the meniscus as well as
both the anterior and posterior horns to the articular capsule of the
allograft (Fig. 23). In
proximal medial tibial unicondylar reconstructions, we use a number-1
nonabsorbable suture to repair the corresponding ends of the medial collateral
ligament. Two suction drains are inserted, and, after lavage of the wound with
saline solution, a meticulous repair of the quadriceps is completed. A layered
closure of the subcutaneous tissues and skin is then performed. Prophylactic
antibiotics are given intravenously, and anticoagulation therapy is routinely
employed.
After reconstruction, the knee is placed in full extension and is secured
with a knee immobilizer or a locked hinged postoperative brace. After two
days, the drains are removed and the wound is inspected. Ice or a cryotherapy
device is used to minimize postoperative swelling and discomfort.
Postoperatively, a physical therapist instructs the patient in brace use,
crutch walking, and isometric quadriceps exercises. The goals during the first
postoperative week are to minimize swelling and to obtain complete passive
extension. Passive flexion exercises are instituted during the second
postoperative week, with the goal of obtaining at least 60° of flexion. At
four weeks postoperatively, active-assisted knee motion is initiated until
full active extension and 90° of flexion are obtained. The patient is
allowed partial weight-bearing at eight to twelve weeks, and at this time the
knee brace is discontinued, depending on the stability obtained at the time of
the operation. Increased weight-bearing is permitted according to the
progression of radiographic union of the allograft and the host bone (Figs.
14 and
24).
CRITICAL CONCEPTSINDICATIONS:The procedure is appropriate for the treatment of massive unicondylar
osteoarticular defects after tumor resection or traumatic bone loss.The major neurovascular bundle must be free of tumor.CONTRAINDICATIONS:Tumor affecting both condyles.Inadequate host soft tissue to reconstruct the joint.Degenerative changes of the tibial or femoral articular surfaces. In this
situation, an allograft prosthetic composite is used.PITFALLS:The procedure is best performed by an orthopaedic oncologic surgeon with
experience in knee reconstructive and sports-medicine procedures.All previous biopsy sites and all potentially contaminated tissues,
including any needle biopsy tracks, should be removed en bloc with the
surgical specimen.Poor anatomical matching for size and shape between the host defect and the
graft or proximal-distal malpositioning of the articular surface of the graft
will substantially alter joint kinematics and load distribution, leading to
bone resorption, joint degeneration, and/or varus or valgus axial
malalignment.Reconstruction of the ligaments must be meticulous and precise because one
side of the joint is normal. Balancing of the soft tissues is critical.To obtain a solid allograft construct, the internal fixation should span
the entire length of the allograft.AUTHOR UPDATE:Since the original article was published, the surgical approach has
remained essentially unchanged.A locking compression plate is now used for the majority of our patients
because we believe that it imparts greater mechanical stability to the
reconstruction.The postoperative care and rehabilitation have remained unchanged.
CRITICAL CONCEPTS
INDICATIONS:
The procedure is appropriate for the treatment of massive unicondylar
osteoarticular defects after tumor resection or traumatic bone loss.The major neurovascular bundle must be free of tumor.
The procedure is appropriate for the treatment of massive unicondylar
osteoarticular defects after tumor resection or traumatic bone loss.
The major neurovascular bundle must be free of tumor.
CONTRAINDICATIONS:
Tumor affecting both condyles.Inadequate host soft tissue to reconstruct the joint.Degenerative changes of the tibial or femoral articular surfaces. In this
situation, an allograft prosthetic composite is used.
Tumor affecting both condyles.
Inadequate host soft tissue to reconstruct the joint.
Degenerative changes of the tibial or femoral articular surfaces. In this
situation, an allograft prosthetic composite is used.
PITFALLS:
The procedure is best performed by an orthopaedic oncologic surgeon with
experience in knee reconstructive and sports-medicine procedures.All previous biopsy sites and all potentially contaminated tissues,
including any needle biopsy tracks, should be removed en bloc with the
surgical specimen.Poor anatomical matching for size and shape between the host defect and the
graft or proximal-distal malpositioning of the articular surface of the graft
will substantially alter joint kinematics and load distribution, leading to
bone resorption, joint degeneration, and/or varus or valgus axial
malalignment.Reconstruction of the ligaments must be meticulous and precise because one
side of the joint is normal. Balancing of the soft tissues is critical.To obtain a solid allograft construct, the internal fixation should span
the entire length of the allograft.
The procedure is best performed by an orthopaedic oncologic surgeon with
experience in knee reconstructive and sports-medicine procedures.
All previous biopsy sites and all potentially contaminated tissues,
including any needle biopsy tracks, should be removed en bloc with the
surgical specimen.
Poor anatomical matching for size and shape between the host defect and the
graft or proximal-distal malpositioning of the articular surface of the graft
will substantially alter joint kinematics and load distribution, leading to
bone resorption, joint degeneration, and/or varus or valgus axial
malalignment.
Reconstruction of the ligaments must be meticulous and precise because one
side of the joint is normal. Balancing of the soft tissues is critical.
To obtain a solid allograft construct, the internal fixation should span
the entire length of the allograft.
AUTHOR UPDATE:
Since the original article was published, the surgical approach has
remained essentially unchanged.A locking compression plate is now used for the majority of our patients
because we believe that it imparts greater mechanical stability to the
reconstruction.The postoperative care and rehabilitation have remained unchanged.
Since the original article was published, the surgical approach has
remained essentially unchanged.
A locking compression plate is now used for the majority of our patients
because we believe that it imparts greater mechanical stability to the
reconstruction.
The postoperative care and rehabilitation have remained unchanged.