Abstract
Background: In the management of a resected distal femoral or
proximal tibial condyle as the result of tumor or trauma, a unicondylar
osteoarticular allograft is currently the only reconstructive option that
avoids the sacrifice of the unaffected condyle. The purposes of this study
were to perform a survival analysis of unicondylar osteoarticular allografts
of the knee and to evaluate the complications.
Methods: We retrospectively reviewed the results of forty large
unicondylar osteoarticular allograft procedures in thirty-eight patients who
were followed for a mean of eleven years. Twenty-nine allografts were femoral
transplants and included eleven medial and eighteen lateral femoral condyles.
Eleven allografts were tibial transplants, including four medial and seven
lateral tibial condyles. The procedure was performed after a tumor resection
in thirty-six patients and to replace condylar loss after a severe open
fracture in the remaining two patients. Complications were analyzed, and
allograft survival from the date of implantation to the date of revision or
the time of the latest follow-up was determined. Functional and radiographic
results were documented according to the Musculoskeletal Tumor Society scoring
system at the time of the latest follow-up.
Results: One patient died of tumor-related causes without allograft
failure before the two-year follow-up evaluation. The global rate of allograft
survival at both five and ten years was 85%, with a mean follow-up of 148
months. In six patients, the allografts were removed at an average of
twenty-six months (range, six to forty-eight months) and these were considered
failures. All six patients underwent a second allograft procedure including
two new unicondylar and four bicondylar reconstructions. The mean radiographic
score for the thirty-three surviving allografts evaluated was 89%, with an
average functional score of 27 of a possible 30 points.
Conclusions: Unicondylar osteoarticular allografts of the knee
appear to be a reliable alternative for patients in whom reconstruction of
massive osteoarticular bone loss is limited to one condyle of the femur or the
tibia.
Level of Evidence: Therapeutic Level IV. See Instructions
to Authors for a complete description of levels of evidence.
Surgical resection is the primary treatment goal in aggressive benign and
malignant bone tumors, often creating large osseous defects. Unicondylar
osteoarticular defects of the knee are challenging because of the demands of
stability and function of this weight-bearing joint. Currently, functional
reconstructive options for these defects include structural allograft
transplantation, endoprosthetic replacement, and composite reconstruction with
use of allografts and metal
prostheses1.
Prosthetic and composite reconstructions require sacrificing the uninvolved
condyle and the contralateral side of the joint. Bicondylar osteoarticular
allografts2-8
provide the opportunity to support mechanical loads, and attach host ligaments
and muscles to the allograft, but this approach compromises both knee condyles
in circumstances in which only one condyle is involved by the tumor. For these
reasons, unicondylar osteoarticular allografts may be a more acceptable
option.
The surgical technique of unicondylar osteoarticular allograft
reconstruction is demanding. However, preserving the uninvolved condyle may
substantially improve the biomechanics of the reconstruction. The purpose of
this study was to analyze the long-term functional and radiographic results of
unicondylar osteoarticular allografts of the knee.
Between April 1962 and April 2001, the Orthopaedic Oncology Service at the
Italian Hospital of Buenos Aires performed forty unicondylar osteoarticular
allograft procedures in thirty-eight patients, among a total of 213
osteoarticular allograft procedures in the same anatomic region. The bone
defect was created by the resection of a tumor (thirty-three aggressive or
recurrent giant-cell tumors, one high-grade osteosarcoma, one chondrosarcoma,
and one malignant fibrous histiocytoma) in thirty-six patients and after a
severe open fracture with massive bone and cartilage loss in the remaining two
patients. The mean age of the patients was thirty years, with a range of
thirteen to fifty-four years. There were eighteen female and twenty male
patients, and they were followed for a mean of eleven years (see
Appendix).
The decision to implant a unicondylar graft was made on the basis of the
aggressiveness of the tumor and the lack of involvement of the condyle as
determined by imaging studies. With regard to the malignant tumors in this
series, this type of reconstruction was performed when, after an appropriate
wide resection, the unaffected condyle remained intact. Benign aggressive
tumors, such as giant-cell tumors, were reconstructed with a unicondylar
allograft when one condyle had sustained a pathological fracture or when,
after the tumor was curetted, there was collapse of the articular surface of
one side.
Nonirradiated allografts were harvested under sterile conditions and were
stored frozen at —80°C in the bone bank at our institution,
according to a technique that has been previously
described6. No
attempt was made to preserve the viability of the articular cartilage, and
bacteriological and viral studies were performed in accordance with the
recommendations of the American Association of Tissue Banks and with use of
the tests available at the time. Thirty-eight transplants were primary
procedures, and two were secondary procedures (after two failures of an
earlier transplant). The allografts were selected on the basis of a comparison
of age, sex, height, and radiographs of the patient with data available from
the donor in order to achieve the closest possible anatomical match. Grafts
were taken out of the package and placed directly in warm (18° to
22°C) saline solution. After being thawed, the donor bone was cut to the
proper size and soft-tissue structures, such as the cruciate ligaments,
collateral ligaments, and posterior capsule, were prepared for implantation
(Fig. 1).
Twenty-nine allografts were femoral transplants, including eleven medial
and eighteen lateral condyles (Fig.
2), and eleven were tibial transplants, including four medial and
seven lateral tibial condyles (Fig.
3). Depending upon the condyle reconstructed, the ligaments were
reattached to the corresponding allograft tissues to improve stability.
Reattachment of the allograft tissue to the host tissue was performed through
a direct lateral-lateral continuous suture. In tibial allografts, the host
meniscus was reattached to the osteoarticular allograft by suturing the
insertions of both horns and the joint capsule. In none of these tibial
osteoarticular allografts was the extensor mechanism reconstructed since, in
all cases, the tibial tuberosity was preserved. Twenty-eight allografts were
fixed with plates and screws, while twelve were stabilized only with screws.
Antibiotics were given intravenously until drains were removed on the third
postoperative day, and no routine anticoagulation therapy was used. In recent
years, external splinting was used until the wound healed. Passive
range-of-motion exercises were started two weeks after the operation,
depending on the type of soft-tissue reconstruction stability obtained at the
time of surgery. Partial weight-bearing was started three months after surgery
and, once healing of the osteotomies had been achieved, full weight-bearing
was allowed.
Patients were seen postoperatively at one week, two weeks, one month, two
months, and three months; every three months thereafter until two years; and
then annually. Plain radiographs were made at every visit, beginning one month
after the operation.
The functional evaluation of the patients was performed with the use of the
revised 30-point functional classification system established by the
International Symposium on Limb Salvage and the Musculoskeletal Tumor
Society9. This
functional score measures six parameters: pain, function, emotional
acceptance, use of walking supports, walking ability, and gait. Each parameter
is given a value ranging from 0 to 5, according to specific criteria. The
individual scores are added together to obtain an overall functional score,
with a maximum of 30 points. A score of 23 points is considered to be an
excellent functional result; between 15 and 22 points, a good result; between
8 and 14 points, a fair result; and <8 points, a poor result. The clinical
study was approved by the institutional review board. Orthopaedic surgeons
(L.A.A.T. and E.A.) interviewed patients by telephone or at their latest
follow-up evaluation and completed a questionnaire with each patient.
The result was evaluated with use of plain anteroposterior and
intercondylar knee radiographs according to the system proposed by the
Musculoskeletal Tumor
Society10, which is
based on eight criteria: the healing of proximal or distal osteotomies, the
contour of the graft, the fixation of the graft, the density of the graft, the
stability of the joint, the diameter of the graft, and the degeneration of the
joint. Each parameter is given a value ranging from 0 to 5, according to
specific criteria. The score was calculated by adding the value for each
criterion and dividing it by the total maximum attainable score. The score is
expressed as a percentage, with the maximum possible score being 100%. A
percentage of =75% is considered an excellent radiographic result; between
50% and 74%, a good result; between 25% and 50%, a fair result; and <25%, a
poor result. Two orthopaedic surgeons (L.A.A.T. and G.F.) evaluated the latest
follow-up radiographs and completed a form for each patient.
The procedure was considered an allograft failure when the allograft was
removed either as a revision procedure or by amputation. The survival of the
allograft was estimated with the use of the Kaplan-Meier
method11, starting
on the date of the operation and ending on the date of removal or the latest
follow-up. Complications, such as local recurrence, fracture, articular
collapse, and infection, were analyzed. Cox regression analysis was done to
determine whether age, gender, date of surgery, diagnosis, side (medial or
lateral), bone (femur or tibia), or type of internal fixation were independent
factors related to the survival of the allograft or damage to the joint. The
chi-square test was used to compare the overall survival or joint damage among
the groups. A p value of <0.05 was considered to be significant.
One patient died of tumor-related causes without allograft failure before
the two-year radiographic follow-up evaluation. Among the remaining
thirty-nine allografts, six failed at an average of twenty-six months (range,
six to forty-eight months) because of infection (two), local recurrence (two),
fracture (one), and massive resorption (one).
The two infected grafts were treated with allograft resection, and the
defect was maintained by an antibiotic-impregnated polymethylmethacrylate
spacer. According to the microorganisms recovered from the site of the
infected allograft, antibiotics were administered for one to three months.
After achieving infection control, one patient underwent a second unicondylar
osteoarticular allograft and the other, a bicondylar osteoarticular
allograft.
The two patients with a local tumor recurrence were managed with a
bicondylar osteoarticular retransplant. In the patient with an intra-articular
allograft fracture, the allograft was removed and a second unicondylar
osteoarticular allograft was implanted. This second allograft failed because
of massive resorption and was converted to a bicondylar osteoarticular
allograft.
Thirty-three unicondylar allografts were in place at the time of the latest
follow-up, with an average functional score of 27 points (range, 20 to 30
points). Function was rated as excellent in thirty patients and good in three.
Eighteen patients had no pain in the involved knee, and fifteen had modest
pain. Fourteen patients had no functional restrictions, eighteen had
restrictions in recreational activities, and one had partial disability.
Thirty patients were enthusiastic about the result, and three were satisfied.
Thirty-two patients walked without the use of supports, and one wore a knee
brace. Nineteen patients could walk an unlimited distance, and fourteen had
some limitations in walking. Twenty-eight patients had no discernible limp,
and five had a minor limp.
Physical examination revealed that the arc of active motion of the knee was
a mean of 115° (range, 50° to 135°). The mean radiographic score
for the thirty-three allografts evaluated was 89%, which represents an
excellent radiographic result, with twenty-seven grafts having scores between
80% and 100%. According to the Musculoskeletal Tumor Society radiographic
evaluation, the joint space was rated as unchanged or with minor deterioration
in 61% (twenty) of the thirty-three allografts. However, 39% (thirteen) of the
thirty-three allografts had some articular deterioration; 18% (six) had joint
narrowing of 2 mm, 9% (three) had joint narrowing of 4 mm, and 12% (four) had
some form of subchondral bone collapse. Although four patients had severe
joint deterioration originating from anatomical mismatches or joint
instability, knee prosthetic resurfacing was required in only two patients.
With the numbers available, no evidence of a significant relationship was
found between articular deterioration and age (p = 0.68), gender (p = 0.16),
date of surgery (p = 0.85), diagnosis (p = 0.19), side (p = 0.84), bone (p =
0.35), or type of internal fixation (p = 0.53).
At the time of the latest evaluation, thirty-three of the forty allografts
remained in place (six had failed and one patient had died) and had been
followed for a mean of 148 months (range, sixty-five to 250 months). The
Kaplan-Meier survival rate for the osteoarticular allografts was 85% (95%
confidence interval, 74% to 96%) at five and ten years
(Fig. 4). With the numbers
studied, no evidence of a significant relationship was found between the
overall allograft survival rate and patient age (p = 0.61), gender (p = 0.77),
date of surgery (p = 0.97), diagnosis (p = 0.78), side (p = 0.75), bone (p =
0.56), or type of internal fixation (p = 0.47).
The primary objective in oncologic surgery is local tumor control, and,
after adequate resection, the surgeon must decide which reconstructive
procedure is best suited for the patient. It is important to consider the
availability of each procedure, the level of surgical difficulty, the
morbidity and incidence of complications associated with each option, as well
as the prognosis for survival and the potential durability of each.
Large bone defects around the knee can be managed with prosthetic
reconstruction with the advantage of maintaining motion and immediate
functional
restoration12-20.
However, although high survival rates have recently been reported with this
type of
reconstruction12,17,
complication and failure rates have also been high in other
series13,16,19,20.
In addition, multiple revisions imply demanding operations with more loss of
bone stock. Another main disadvantage is that when the massive osteoarticular
bone loss is limited to one condyle, prosthetic reconstruction sacrifices the
contralateral articular surface and the unaffected condyle, leading to
excessive bone loss. An increased emphasis has been placed on biologic
reconstructive alternatives because of concerns related to the durability of
prosthetic materials in these generally very young patients. Osteoarticular
allografts are readily available from tissue banks and can be matched to the
size of the resected bone. For these reasons, unicondylar osteoarticular
allografts might be a more acceptable option, with survival rates of 85% at
five and ten years and an average functional score of 27 points as shown in
this study. Although complications and failures occurred during the first four
years, similar to the findings in previous reports for bicondylar
allografts21-23,
no additional failures, according to our definition, were found after that
period of time.
Late osteoarticular allograft failures may occur over time because of
gradual joint deterioration. Anatomical and dimensional matching of the
articular surface, obtaining adequate joint stability by host-donor
soft-tissue repair, and achieving joint alignment have been associated with
minor degenerative changes of the articular surface of osteoarticular
allografts24,25.
Therefore, selection of the closest anatomical match between the host and the
donor is crucial. In two of our thirty-three patients, prosthetic knee
resurfacing was required because of joint deterioration that originated from
anatomical mismatches or joint instability. Additionally, improper surgical
placement of the graft could adversely affect the outcome even if an ideal
unicondylar graft has been selected. Distal or proximal malposition offset can
lead to inappropriate loading of the articular surface, with a consequent
varus or valgus deformity of the joint. Appropriate reconstruction of the soft
tissues is also an important factor for obtaining joint stability after graft
placement. When a bicondylar allograft replacement is used, stability may be
controlled by tightening or releasing all newly sutured soft-tissue
structures. However, when a unicondylar reconstruction is performed, balancing
ligament stability is more demanding since the ligament of the unaffected side
of the knee remains intact.
Our study has several limitations. This was a retrospective clinical study
with potentially uncontrolled variables, such as different locations (medial
and lateral), variable extents of soft-tissue resection, and differences in
internal fixation. Other limitations include the small numbers of patients
with particular types of replacements (for example, there were only four
medial tibial condylar allografts), the inclusion of some patients with only
five years of follow-up, and the lack of any control group with bicondylar or
prosthetic replacements for comparison. Unicondylar osteoarticular allografts
are mainly used following resection of a benign aggressive tumor (such as
giant-cell tumor) around the knee or a malignant tumor with growth limited to
one condyle and with clearly defined margins. Although this situation is
common in orthopaedic oncology, there are few options to reconstruct such a
bone defect without compromising the unaffected condyle.
At the present time, there are very limited reconstructive functional
options for a severe condylar defect in the knee. The allograft survival rate
of 85% at five and ten years in these patients, who were followed for a mean
of 148 months, suggests that a unicondylar allograft may be a reliable
alternative when the massive osteoarticular bone loss to be reconstructed is
limited to one condyle of the knee.
A table showing the clinical details of all study subjects is available
with the electronic versions of this article, on our web site at
(go to
the article citation and click on "Supplementary Material") and on
our quarterly CD-ROM (call our subscription department, at 781-449-9780, to
order the CD-ROM). ?
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