Abstract
Background: The purpose of this study was to prospectively evaluate
the results of meniscal transplantation in a consecutive series of younger
patients treated for pain in the tibiofemoral compartment following a previous
meniscectomy.
Methods: Forty cryopreserved menisci were implanted into
thirty-eight patients. Sixteen knees also had an osteochondral autograft
transfer, and nine had a knee ligament reconstruction. The clinical outcome
and failure rate of all transplants were evaluated at a mean of forty months
postoperatively. Meniscal allograft characteristics were determined with use
of a rating system that combined subjective, clinical, and magnetic resonance
imaging factors.
Results: Thirty-four (89%) of the thirty-eight patients rated the
knee condition as improved. Before surgery, thirty patients (79%) had pain
with daily activities, but only four (11%) had such pain at the time of the
latest follow-up. While noteworthy pain was present in the tibiofemoral
compartment in all forty knees before surgery, twenty-seven knees (68%) had no
pain and thirteen (33%) had only mild compartment pain at the time of the
latest follow-up. Twenty-nine patients (76%) returned to light low-impact
sports without problems. Concomitant osteochondral autograft transfer and knee
ligament reconstruction procedures improved knee function and did not increase
the rate of complications. Meniscal allograft characteristics were normal in
seventeen knees (43%), altered in twelve (30%), and failed in eleven
(28%).
Conclusions: The short-term results of meniscal transplantation are
encouraging in terms of reducing knee pain and increasing function; however,
long-term transplant function and any chondroprotective effects remain unknown
and require further investigation.
Level of Evidence: Therapeutic study, Level IV (case
series [no, or historical, control group]). See Instructions to Authors for a
complete description of levels of evidence.
The meniscus provides vital load-bearing and shock-absorption functions
that are important for the integrity of the articular
cartilage1-3.
After meniscectomy, the decrease in tibiofemoral contact area and the increase
in joint contact pressures commonly lead to articular cartilage
degeneration4-7.
The risk for tibiofemoral arthrosis after meniscectomy has been demonstrated
in clinical
studies6,8-13
and has been shown to be increased in knees with a deficient anterior cruciate
ligament14-17
and axial malalignment of the lower limb.
There has been increased emphasis on the repair of meniscal tears,
including complex tears that extend into the central avascular
zone18-20.
However, not all meniscal tears can be repaired, especially if considerable
tissue damage has occurred. Transplantation of human menisci should restore
some load-bearing meniscal function. However, inconsistent results have been
found in experimental
studies21-29,
and clinical investigators have disagreed on the outcome and success
rates28-41.
Meniscal transplantation remains an evolving area, and there is a lack of
consensus regarding tissue-processing, secondary sterilization, long-term
function, and efficacy of the
procedure42,43.
The primary candidate is a young patient who has had a total meniscectomy and
has pain in the tibiofemoral compartment because of early joint arthrosis. For
these patients, there are few treatment options and the goal of meniscal
transplantation in the short term is to decrease pain and delay the
progression of tibiofemoral arthrosis. Additionally, patients may have
concomitant problems requiring ligament reconstruction or procedures to
restore the articular cartilage.
The purpose of this prospective study was to determine the results of forty
consecutive meniscal allografts. All operations were done by the same surgeon
(F.R.N.), and the results were analyzed by a senior research associate and not
the surgeon. We hypothesized that the meniscal transplant would significantly
reduce tibiofemoral compartment pain with daily activities and that knees that
had a concomitant osteochondral autograft transfer procedure for a localized
femoral condylar defect would also demonstrate significant reduction in pain
and improvement in knee function without an increased rate of postoperative
complications.
Patients
Forty cryopreserved meniscal allografts (twenty lateral and twenty medial)
were implanted in thirty-eight patients from November 1995 to March 2000. A
single meniscal allograft was implanted into thirty-six patients, and a medial
and a lateral meniscal allograft were implanted into one knee in two patients.
All patients provided informed consent to undergo meniscal transplantation and
participate in research follow-up visits. Institutional review board approval
was obtained for the special diagnostic magnetic resonance imaging
studies.
All but one patient returned for an evaluation at an average of forty
months (range, twenty-four to sixty-nine months) postoperatively. One patient
could not return but completed the subjective and functional assessment and
was interviewed five years postoperatively. This patient had had medial and
lateral meniscal allografts removed eight weeks postoperatively because of a
substantial inflammatory reaction, knee effusion, and pain. Numerous cultures
were negative, but the allografts had deteriorated and fragmented, presumably
because of an acute
rejection44 or
allergic response. These two meniscal allografts were included in the overall
rate of failure.
There were twenty male and eighteen female patients, and the average age at
the time of surgery was thirty years (range, fourteen to forty-nine years).
Twenty-eight patients (74%) were injured during sports or rigorous activities.
The average time-interval between the knee injury and the meniscal allograft
operation was 137 months (range, twelve to 372 months). Before the meniscal
allograft procedure, the patients had had 139 operations, including
sixty-eight partial or total meniscectomies, thirty-one arthroscopies, six
meniscus repairs, fourteen anterior cruciate ligament reconstructions, four
posterior cruciate ligament reconstructions, one lateral collateral ligament
reconstruction, six high tibial osteotomies, three osteochondral autograft
transfer procedures, and six other operations.
The indications for the meniscal allograft were prior meniscectomy, an age
of fifty years or less, clinical symptoms of pain in the tibiofemoral
compartment, no radiographic evidence of advanced arthrosis, and =2 mm of
tibiofemoral joint space on 45° weight-bearing posteroanterior
radiographs45.
Exclusion criteria were advanced knee joint arthrosis with flattening of the
femoral condyle, concavity of the tibial plateau, and osteophytes that
prevented anatomic seating of the meniscal allograft; axial malalignment of
varus, in which a weight-bearing line of <40% of the medial-lateral
transverse width of the tibial
plateau46 was
present, or valgus malalignment, in which a weight-bearing line of >60% was
present on radiographic evaluation; knee joint instability or patient refusal
to undergo concomitant knee ligament reconstruction; knee arthrofibrosis;
muscular atrophy; and prior joint infection.
Osteochondral autograft transfer procedures were done in sixteen knees
(40%); nine were done on the lateral femoral condyle and seven, on the medial
femoral condyle. An average of two (range, one to five) 6-mm-diameter
osteochondral grafts were placed into the defect from harvest sites along the
peripheral and proximal portions of the medial or lateral femoral condyle.
Knee ligament reconstructions were done before the meniscal allograft
transplantation in five patients and at the same time as the transplantation
in four patients. In seven patients, anterior cruciate ligament
reconstructions were done with use of either bone-patellar tendon-bone or
semitendinosus-gracilis autografts. One patient also had a medial collateral
ligament reconstruction. A posterior cruciate ligament reconstruction was done
in one patient with a two-strand quadriceps tendon-patellar bone
autograft47. Both
the posterior cruciate and the anterior cruciate ligament were reconstructed
in one patient.
Clinical and Radiographic Evaluation
A comprehensive evaluation of the knee included assessment of tibiofemoral
joint pain on palpation and during joint motion, and palpable meniscal
displacement during joint compression and distraction. A positive rotation and
flexion test (the McMurray test) was indicative of signs of a possible tear in
the transplant. The examination also evaluated the patellofemoral joint, knee
stability, and gait
abnormalities14.
The tibiofemoral joint space was evaluated in all knees before surgery and at
the latest follow-up evaluation with 45° weight-bearing posteroanterior
radiographs45.
Axial alignment was measured with use of full-length (hip, knee, and ankle)
standing
radiographs46 in
knees that demonstrated varus or valgus alignment.
Magnetic Resonance Imaging Studies
Magnetic resonance imaging was performed on all knees before surgery to
determine the status of the articular cartilage and prior meniscectomy. For
eighteen patients who lived out of town, the preoperative magnetic resonance
imaging was done at other institutions. The radiographs and magnetic resonance
imaging studies were reviewed by one of us (M.R.) to determine a joint
arthrosis rating. Knees were categorized, with use of a qualitative analysis,
as having no or mild arthrosis, moderate arthrosis, or severe arthrosis. Those
categorized as having no or mild arthrosis demonstrated normal tibiofemoral
joint space (equal to the contralateral tibiofemoral compartment), no
alteration to the normal osseous contour of the knee joint, and no
osteophytes. Knees with moderate arthrosis had at least 50% of the
tibiofemoral joint space, limited osteophyte formation, normal or only mild
alteration to the normal osseous contour of the knee joint, and a few
osteophytes. Knees with severe arthrosis had <50% of the tibiofemoral joint
space remaining, large osteophytes, femoral flattening, tibial concavity, and
loss of articular cartilage. In this investigation, knees with severe
arthrosis were not considered candidates for a meniscal transplant.
Twenty-nine meniscal allografts (73%) were analyzed with magnetic resonance
imaging, with use of our research protocol, at an average of thirty-five
months (range, twelve to sixty-seven months) postoperatively. The scans were
reviewed and measured by an independent orthopaedist who was blinded to
patient information. We assessed allograft height, width, and
displacement48
during full or partial weight-bearing (loaded) conditions. Intrameniscal
signal intensity was classified according to the method described by Stoller
et al.49, in which
grade 1 represented a nonarticular focal or globular intrasubstance increased
signal; grade 2, a horizontal, linear intrasubstance increased signal that
extended from the capsular periphery of the meniscus but did not involve an
articular meniscal surface; and grade 3, an area of increased signal intensity
that communicated or extended to at least one articular surface. We recognize
that it is difficult in a healed meniscal allograft to distinguish scar
tissue, suture artifacts, and meniscal tears.
Eight meniscal allografts in seven knees were analyzed at an average of
twenty-four months (range, fifteen to thirty-four months) postoperatively in a
0.5-T superconducting vertically oriented open magnet (General Electric
Medical Systems, Milwaukee, Wisconsin). A specially designed apparatus was
used to allow the patient to stand and apply full weight-bearing while the
knee was scanned. Single-slice sagittal and coronal images were obtained with
use of gradient-echo sequencing with the knee at full extension (0°).
Twenty-four meniscal allografts were assessed at an average of thirty-eight
months (range, twelve to sixty-seven months) postoperatively with the patient
lying supine in a 0.7-T superconducting magnet (General Electric Medical
Systems). An apparatus with a pulley weight system and a foot-plate was
designed. The knees were placed in approximately 30° of flexion, and
patients were asked to retain this flexion angle by pushing against the
foot-plate when approximately 176 N of resistance was applied. In this manner,
the patients actively contracted the quadriceps, thereby loading the knee
joint while resisting knee flexion. Spin-echo T1-weighted images were acquired
in the axial, sagittal, and coronal planes.
Subjective and Functional Assessment
Before surgery and at the most recent examination, patients completed the
validated Cincinnati knee-rating
system50 and were
then interviewed by a research associate to determine symptoms, functional
limitations, and
sports51 and
occupational activity
levels52. The
occupational rating system assessed the frequency and intensity of seven
factors (sitting, standing or walking, walking on uneven ground, squatting,
climbing, lifting or carrying, and weight carried) during full-time
employment52.
Patients received a score on a scale of 0 to 100; high scores indicated
occupations involving high level intensity, frequency, and duration of tasks
that stressed the lower extremity.
The Cincinnati knee-rating system included a patient assessment of the
overall condition of the knee on a numeric 10-point scale. Four descriptive
terms provided on the scale were "poor" (number 2),
"fair" (number 4), "good" (number 6), and
"normal" (number 10).
Knee pain was assessed with multiple questions. The pain scale of the
Cincinnati knee-rating
system50,51
was used to determine the highest activity level possible that the patient
could achieve without pain. On this scale, a score of 0 indicated pain with
daily activities; 2, moderate pain with daily activities; 4, no pain with
daily activities but pain with light sports (bicycling or swimming); 6, no
pain with light sports but pain with moderate sports (running, twisting, or
turning); 8, no pain with moderate sports but pain with strenuous sports
(jumping or hard pivoting); and 10, no pain with strenuous sports. Patients
were asked to rate the pain severity on a scale of 0 to 10, where 0 indicated
no pain and 10, the worst pain imaginable. The location of the pain was noted
as either local (in the compartment of the meniscal allograft) or diffuse.
Testing with a KT-2000 arthrometer (MedMetric, San Diego, California) was
done at 134 N of total anterior-posterior force preoperatively and
postoperatively in the knees that had cruciate ligament reconstructions. The
result of the pivot-shift test was graded on a scale of 0 to 3, with grade 0
indicating no pivot shift; grade 1, a slip; grade 2, a jerk with gross
subluxation; and grade 3, gross subluxation with impingement. Stress
radiographs were made for patients who had a posterior cruciate ligament
reconstruction to measure posterior tibial
displacement53. An
X-Stress device (SAMO, Bologna, Italy) was used to apply an 89-N force to the
proximal part of the tibia. A lateral radiograph was made of each knee at
90° of flexion. The limb was placed in neutral rotation with the tibia
unconstrained and the quadriceps relaxed. The International Knee Documentation
Committee54
classification system was used to determine knee ligament graft function. Data
from the KT-2000 arthrometer test, the stress
radiographs53, and
the clinical evaluation were used to classify graft function as normal, nearly
normal, abnormal (or partially functional), or severely abnormal (or
failed).
Meniscal Allograft Classification
A classification of the meniscal allograft characteristics was developed on
the basis of the results of magnetic resonance imaging, follow-up arthroscopy
(for the patients with persistent or recurrent symptoms), clinical
examination, and symptoms (Table
I). A meniscal transplant with a failure in any one of the six
categories was rated as having failed. Alternatively, in order to be
classified as normal, a meniscal transplant had to have all categories rated
as normal.
Surgical Procedures
Anteroposterior and lateral radiographs were used to obtain meniscal width
and length
measurements55. The
meniscal allografts were harvested with use of aseptic techniques following
Food and Drug Administration guidelines, cryopreserved (CryoLife, Kennesaw,
Georgia), and thawed just prior to implantation. The transplants were cultured
before and after implantation and were inspected for any degenerative
changes.
The patient was placed in the supine position on the operating room table
with a tourniquet applied with a leg holder, and the table was adjusted to
allow 90° of knee flexion. After examination with the patient under
anesthesia, diagnostic arthroscopy was done to confirm the preoperative
diagnosis and articular cartilage changes. In knees requiring a cruciate
ligament reconstruction, an arthroscopically assisted approach was
used56. The femoral
and tibial tunnels were drilled, and the ligament graft was passed through the
tunnels with femoral fixation done first, followed by the meniscal
transplantation, and then tibial graft fixation. Performing final ligament
graft fixation at the tibia as the final step allowed for maximum separation
of the tibiofemoral joint during meniscal transplantation. This also presented
potential failure or problems with the ligament fixation or ligament graft
during the operation.
Technique for Medial Meniscal Transplantation
Because a medial meniscal transplant has separate anterior and posterior
bone attachments, which must be secured at anatomic attachment sites to
maintain the desired position in the knee joint and to provide circumferential
tension in the transplant, an arthroscopically assisted double bone-plug
technique was
performed57. The
posterior bone plug was 8 mm in diameter and 12 mm in length. The anterior
bone plug was 12 mm in diameter and 12 mm in length. Three 2-0 nonabsorbable
Ethibond sutures (Ethicon, Somerville, New Jersey) were passed retrograde
through each bone plug, with two additional locking sutures placed in the
meniscus adjacent to the bone attachment for secure fixation of the bone plugs
within the tibial tunnel.
A 4-cm skin incision was made on the anterior aspect of the tibia adjacent
to the tibial tubercle and patellar tendon. A second 3-cm posteromedial
incision, similar to that described for inside-out meniscal repairs, was
made19,58.
The two approaches were performed with the tourniquet inflated to 275 mm and
usually required fifteen minutes; otherwise, the tourniquet was not used.
A guide-pin was placed adjacent to the tibial tubercle and was directed to
the anatomic posterior meniscal attachment, and a tibial tunnel was drilled
over the guide-wire to a diameter of 8 mm. The bone tunnel edges were
chamfered. A limited medial femoral condyle notchplasty was usually required.
At least 8 mm of opening was required adjacent to the posterior cruciate
ligament in the femoral notch to pass the posterior osseous portion of the
graft. In three knees, a subperiosteal release of the long fibers of the
tibial attachment of the medial collateral ligament (with later suture anchor
repair) was required to open the medial tibiofemoral joint sufficiently. The
meniscal bed was prepared by removing any remaining meniscal tissue while
preserving a 3-mm rim when possible. The meniscal bed was rasped for
revascularization of the graft.
A 3-cm medial arthrotomy was used to pass the posterior bone portion of the
graft, with a secondary meniscal body suture passed out the posteromedial
approach. The surgeon was seated with a headlight in place, and the knee was
flexed to 90°. On occasion, there were anterior osteophytes on the medial
tibial plateau that required resection. The posterior attachment guide-wire
was retrieved, and the sutures attached to the posterior bone were passed. A
second suture was placed into the mid-portion of the meniscus and was passed
inside-out through the posteromedial approach to guide the meniscus.
The knee was 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 was used to gently assist the passage of
the graft. With use of a headlight and retractors, it was possible to confirm
appropriate meniscal graft passage into the medial tibiofemoral compartment.
Care was taken not to advance the posterior meniscal body into the tibial
tunnel but only to seat the bone portion of the graft in order to not shorten
the meniscal graft. The posterior meniscal bone attachment and mid-body
sutures were tied over the tibial post to provide tension in the posterior
bone attachment and posterior one-third of the meniscus. The knee was flexed
and extended to assess the meniscal fit and displacement. The optimal location
for the anterior meniscal bone attachment at the anteromedial junction of the
tibial plateau was identified, with the medial to lateral placement in the
coronal plane determined with the knee in full extension. A 12-mm rectangular
bone attachment was fashioned to correspond to the anterior bone portion of
the meniscal graft. A 4-mm bone tunnel was placed at the base of this bone
trough; it exited at the anterior portion of the tibia just proximal to the
posterior bone tunnel. The sutures were passed through the bone tunnel, and
the anterior horn was seated. Full knee flexion and extension was again
performed to determine proper graft placement and fit. Tension was applied to
the anterior bone sutures, which were not tied at this point but were 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 posterior horns was believed to
be crucial for future meniscal weight-bearing position and function
(Fig. 1).
The anterior arthrotomy was closed, and the arthroscope was inserted into
the anterolateral portal for the posterior meniscal repair and into the
anteromedial portal for the middle and anterior one-third repairs, with the
single needle cannula inserted in the other anterior portal. The meniscal
repair was performed in an inside-out fashion, starting with the posterior
horn, with use of multiple vertical divergent sutures of 2-0 nonabsorbable
Ethibond both superiorly and inferiorly, constantly tensioning the meniscus
from posterior to anterior to establish circumferential tension. The assistant
was seated with a headlight and retrieved the suture needles through the
posteromedial approach. Each suture was placed and tied, bringing the meniscus
directly to the meniscal bed with observation that correct meniscal placement,
fixation, and tension existed. The anterior arthrotomy was again opened, and
the final tensioning and tying of the anterior horn bone sutures was performed
with use of the anterior tibial post. Occasionally, additional sutures were
required to secure the most anterior one-third of the meniscus to the capsular
attachments, which was performed under direct vision. After final inspection
of the graft with knee flexion and extension and tibial rotation, the
operative wounds were closed in a routine fashion.
Technique for Lateral Meniscal Transplantation
The lateral meniscus, with the anterior and posterior horns remaining
attached centrally to bone, provides the most ideal transplant. Because the
attachment sites and circumference tension relations are not disturbed, an
arthroscopically assisted keyhole
method57 of
attachment can be performed with a meticulous inside-out meniscal
repair19. The
central bone portion of the transplant incorporated the anterior and posterior
meniscal attachments and measured 8 to 9 mm in width and 35 mm in length. The
posterior 8 to 10 mm of bone that protruded beyond the posterior horn
attachment was removed to later provide a buttress against the bone trough in
the host knee.
A limited 3-cm lateral arthrotomy was made just adjacent to the patellar
tendon. A similar 3-cm posterolateral longitudinal approach was made as
described for inside-out lateral meniscal
repairs19,58.
A Henning retractor was placed directly behind the lateral meniscal bed. A
tourniquet was inflated only for these two approaches; otherwise, it was not
used.
A rectangular bone trough was prepared at the lateral meniscal anterior and
posterior tibial attachment sites to match the dimensions of the prepared
lateral meniscal transplant. The width of the transplant was determined, and a
paper ruler of the same width was cut and inserted into the lateral
compartment to determine the lateralmost margin of the bone trough. This
sizing step was important to make sure that there was no lateral overhang of
the meniscal body produced by placing the bone trough too far laterally. The
anterior horn was placed into its normal attachment, which extended medially
and adjacent to the anterior cruciate ligament. A 4-mm anterior tibial tunnel
was drilled into the bone trough, exiting just distal to the joint line, and
two sutures were passed over the central bone area of the transplant for
fixation of the graft to the tibial trough. The allograft was inserted into
the trough (Fig. 2), and the
bone portion of the graft was seated against the posterior bone buttress to
achieve correct anterior-to-posterior placement of the attachment sites. The
knee was flexed, extended, and rotated to confirm correct allograft placement.
The central bone attachment sutures were tied, the arthrotomy was closed, and
the inside-out meniscal repair was
performed19.
The appearance of the articular cartilage was classified during the
meniscal allograft procedure and was scored as previously
described59. The
cartilage was considered to be abnormal if there was a lesion that was =15
mm in diameter with fissuring and fragmentation of more than one-half of the
depth of the cartilage, or if any subchondral bone was exposed.
Postoperative Rehabilitation
The initial goal of the rehabilitation program was to prevent excessive
weight-bearing and joint compressive forces that could disrupt the healing
meniscal allograft. Immediately following surgery, the patients were placed in
a long leg brace, which was worn for approximately eight weeks.
Range-of-motion exercises from 0° to 90° were allowed the first day.
The range of flexion was increased 10° each week to allow 135° after
the fourth week. The patients were allowed only toe-touch weight-bearing
during the first two weeks and then were slowly increased to 50% of body
weight at the fourth week and to full weight-bearing at the sixth week. A
patient who had a concomitant posterior cruciate ligament
reconstruction60
was restricted in flexion and weight-bearing for eight weeks. The anterior
cruciate ligament rehabilitation program followed a previously described
protocol61.
A Bledsoe Thruster brace (Medical Technology, Grand Prairie, Texas) was
recommended for patients in whom the articular cartilage was abnormal, to
reduce loads in the tibiofemoral compartment.
Flexibility and quadriceps-strengthening exercises were begun immediately
postoperatively. Balance, proprioception, and closed-kinetic chain exercises
were implemented when a patient achieved full weight-bearing. Stationary
bicycling with low resistance was begun at the eighth week, and swimming and
walking programs were initiated between the ninth and twelfth weeks. Return to
light recreational sports was delayed for at least twelve months. Patients
were advised not to return to high-impact strenuous athletics.
Statistical Methods
In order to evaluate the primary study outcome (the pain score),
sample-size calculations were made and the power to detect a difference of 2
points between the mean scores at the preoperative examination and at the time
of the latest follow-up were determined. With thirty-eight patients in this
study, it was found that the investigation had sufficient power (80%) to
detect those differences at a significance level of 0.05. Paired two-tailed
Student t tests, contingency table analyses, single linear regression
analyses, and chi-square tests were used to determine significant differences
between preoperative and follow-up data.
Functional Outcome
The subgroup analysis comparing patients who had a concomitant
osteochondral autograft transfer procedure with those who did not have this
procedure did not reveal any difference with regard to complications, the rate
of reoperations due to meniscal allograft symptoms, clinical pain symptoms,
analysis of the functions of daily and sports activities, and the patient's
perception of the knee condition (see Appendix). Similar findings were
obtained when comparing the patients who had a ligament reconstruction with
those who did not have a reconstruction. Therefore, we present a combined
analysis of the data.
The mean pain score on the Cincinnati knee-rating scale was 2.5 points
(range, 0 to 6 points) preoperatively and improved to a mean of 5.8 points
(range, 0 to 10 points) at the time of the latest follow-up (p < 0.0001,
Table II). Before the meniscal
allograft procedure, thirty patients (79%) had moderate-to-severe pain with
daily activities, but at the time of the latest follow-up only four patients
(11%) had pain with daily activities (Fig.
3). Pain in the meniscectomized tibiofemoral compartment was
present in all forty knees prior to the meniscal allograft procedure. At the
time of follow-up, twenty-seven knees (68%) had no tibiofemoral compartment
pain and thirteen (33%) were improved and had only mild pain. Thirteen
patients rated the knee pain severity as either 0 or 1; fifteen, as 2 or 3;
eight, as 4 or 5; one, as 6; and one, as 9.
Thirty-four patients (89%) believed that the condition of the knee had
improved (Fig. 4). The mean
score for patient perception was 3.2 points (range, 1 to 6 points)
preoperatively and improved to 6.2 points (range, 1 to 9 points) at the time
of the latest follow-up (p = 0.0001). Two patients rated the knee condition as
the same, and two rated it as worse.
The mean walking score was 29 points preoperatively and improved to 37
points at the time of the latest follow-up (p = 0.0008,
Table II). Before the meniscal
allograft transplantation, twelve patients (32%) had severe limitations with
walking, but only four patients (11%) had such problems at the time of the
latest follow-up. These four patients all had articular cartilage damage, and
none returned to sports activities.
Before the meniscal allograft procedure, seven patients participated in
light sports and all but one had substantial limitations
(Table III). At the time of the
latest follow-up, twenty-nine patients (76%) were participating in light
low-impact sports without problems and one patient with symptoms was
participating against advice. Eight patients did not return to sports because
of the knee condition.
Before the meniscal allograft procedure, five patients were disabled,
eighteen were working, and fifteen were not in the workforce
(Table IV). At the time of the
latest follow-up, three patients were disabled, twenty-five were working
without limitations, two were working with symptoms, and eight were not in the
workforce. The mean preoperative score on the Occupational Rating Scale of 29
points (range, 0 to 70 points) was similar to the mean score at the time of
the latest follow-up of 26 points (range, 0 to 78 points). The lower score at
the time of the latest follow-up reflected the addition of seven patients who
had been students or homemakers before the operation and who had entered the
workforce after surgery; most of them were in occupations rated as very light
or light labor.
There was no correlation between the amount of time from the injury to the
transplantation and the pain, swelling, daily functions, or the patients'
perception of the knee condition.
Articular Cartilage Findings
Abnormal articular cartilage surfaces were detected in the tibiofemoral
compartment in thirty-four knees (85%) at the time of meniscal
transplantation. Subchondral bone exposure was found in twenty knees, and
extensive fissuring and fragmentation was noted in fourteen others.
Findings on Magnetic Resonance Imaging
The mean displacement of the twenty-nine meniscal allografts examined with
magnetic resonance imaging was 2.2 ± 1.5 mm (range, 0 to 5 mm) in the
coronal plane (Table V).
Seventeen allografts (59%) had no displacement, eleven had minor displacement,
and one could not be evaluated because of artifacts from other operative
procedures.
In the sagittal plane, the mean displacement of the posterior horn of the
allografts was 1.1 ± 2.0 mm (range, 0 to 9 mm). Twenty-five allografts
(86%) had no displacement of the posterior horn, three had minor displacement,
and one had major displacement (9 mm). The mean displacement of the anterior
horn of the allografts was 1.2 ± 1.7 mm (range, 0 to 6 mm). Twenty-five
allografts had no displacement of the anterior horn, three had minor
displacement, and one had major displacement (6 mm).
Intrameniscal signal intensity was normal in one, grade 1 in thirteen,
grade 2 in eleven, grade 3 in three, and could not be evaluated in one. Knee
joint arthrosis was rated as normal or mild in twenty-two and as moderate in
eighteen.
Knee and Radiographic Examination
One patient had signs of a meniscal tear at the time of follow-up. One
patient had tibiofemoral joint-line pain and increased palpable crepitation
compared with the findings at the preoperative examination. All patients had a
normal range of knee motion. A mild joint effusion was present in four
patients.
All seven knees that had an anterior cruciate ligament reconstruction had
normal or nearly normal anterior stability restored except one in which the
reconstruction failed. The posterior cruciate ligament reconstructions
restored nearly normal stability at 20° and 90° of flexion in the two
knees that had this operation, although one of them restored only partial
stability at 90° of flexion. No knee had an abnormal increase in medial or
lateral tibiofemoral joint-line opening or external tibial rotation.
A comparison of weight-bearing posteroanterior radiographs made
preoperatively and at the time of the latest follow-up revealed that three
knees had further deterioration and narrowing of the tibiofemoral joint space
in the involved compartment.
Follow-up Arthroscopy for Meniscal Symptoms
Four meniscal allografts in three patients were removed early
postoperatively. One patient had medial and lateral meniscal allografts
removed eight weeks postoperatively as described previously. Two patients had
knee symptoms indicative of tearing of the transplant, and the allografts were
removed eighteen months postoperatively.
Five other patients had follow-up arthroscopy for tibiofemoral symptoms
related to the meniscal allograft at three, four, six, fifty-nine, and
sixty-four months postoperatively. In three patients, tears in the periphery
of the meniscal allograft at the capsular junction were successfully repaired.
In two patients, very small tears in the allograft were resected. None of
these patients had further complaints or tibiofemoral symptoms after the
arthroscopy. All five patients were included in the portions of this study
involving the clinical examination, symptoms, and functional assessment. The
final classification of meniscal allograft characteristics in these five
patients was normal in one, altered in three, and failed in one.
One other patient had a total knee replacement thirty-five months following
the meniscal allograft transplant because of unresolved knee pain and a failed
meniscal allograft.
Classification of Meniscal Allograft Characteristics
Seventeen meniscal allografts (43%) had normal characteristics, twelve
(30%) had altered characteristics, and eleven (28%) failed. Of the twenty
lateral meniscal transplants, nine had normal characteristics, seven had
altered characteristics, and four failed. Of the twenty medial meniscal
allografts, eight had normal characteristics, five had altered
characteristics, and seven failed.
Of the twenty-two allografts in knees with no or mild arthrosis, twelve had
normal characteristics, seven had altered characteristics, and three failed.
Of the eighteen allografts in knees with moderate arthrosis, five had normal
characteristics, five had altered characteristics, and eight failed (p =
0.07).
Correlations were also found between the allograft characteristics and the
scores for pain, swelling, and walking (p < 0.05). Allografts with normal
or only altered characteristics had higher mean scores for these variables
than did those that had failed. With the numbers available, no association was
found between allograft characteristics and scores for patient perception of
the knee condition, stair-climbing, squatting, running, jumping, or twisting.
The transplant failures did not correlate with activity levels, lower limb
alignment, ligamentous deficiency, radiographic signs of joint space
narrowing, or side of implantation.
Complications
There were no infections, arthrofibrosis, or limitations of knee motion at
the time of follow-up. Four knees required a manipulation four to six weeks
postoperatively for a limitation of knee flexion. Each of these knees had had
a concomitant procedure: a posterior cruciate ligament reconstruction and a
combined posterior cruciate and anterior cruciate ligament reconstruction in
one knee each and an osteochondral autograft transfer in two knees. Four
meniscal allografts failed and were removed between eight weeks and eighteen
months postoperatively as previously described.
The present study is the first that we are aware of to use a rigorous
rating system combining subjective, clinical, and weight-bearing magnetic
resonance imaging factors to determine meniscal allograft characteristics
after implantation. This investigation also represents the first report, as
far as we know, on the clinical outcome of knees after a combined meniscal
allograft and osteochondral autograft transfer procedure. We realize that this
additional procedure represented a confounding variable and, in these knees,
it is unknown whether the improvement in symptoms and knee function was
related to the meniscal allograft, the osteochondral autograft transfer, or
both procedures.
Tibiofemoral pain was substantially reduced in twenty-eight of our
thirty-eight patients at an average of forty months postoperatively. Pain in
the tibiofemoral compartment was present in all forty knees preoperatively;
however, at the time of the latest follow-up, twenty-seven knees (68%) had no
tibiofemoral pain and thirteen (33%) were improved and had only mild pain.
Because the majority of patients were young and had been athletically active
before the meniscectomy, the ability to return to an active lifestyle (even in
terms of only light recreational activities) was an important goal. At the
time of follow-up, twenty-nine (76%) of the thirty-eight patients had returned
to light low-impact sports with no symptoms. This improvement in
activity-related restrictions was reflected in the patients' perception of the
knee condition, as thirty-four (89%) of the thirty-eight patients rated the
knee at a higher level than that recorded preoperatively. Meniscal
transplantation, however, does not allow the return to vigorous activities
that induce high joint-loading forces. Patient counseling preoperatively, and
acceptance of these limitations, is required.
The results of meniscal transplantation are more favorable when the
operation is done before the onset of advanced tibiofemoral joint
arthrosis33,36.
We advise younger patients who have had a meniscectomy to avoid high-impact
loading conditions. These patients are followed with use of 45°
posteroanterior weight-bearing radiographs, spiral computed tomographic
arthrography62, and
magnetic resonance imaging with use of proton-density, fast-spin-echo
techniques33,63
to evaluate the status of the articular cartilage and assess subchondral bone
edema. The goal of these studies is to detect early joint arthrosis. We do not
recommend a prophylactic meniscal transplantation even after total
meniscectomy in asymptomatic patients who do not demonstrate articular
cartilage deterioration. We do, however, recommend this operation after total
meniscectomy in asymptomatic patients who are less than fifty years old
(particularly in nonsedentary individuals) in whom articular cartilage
deterioration is demonstrated either at arthroscopy or through the imaging
techniques described above. This recommendation is based on the hypothesis
that the transplant will provide increased load-sharing, shock absorption, and
protection of the articular cartilage. In the current investigation, 85% of
the knees had localized areas of articular cartilage deterioration in the
affected compartment at the time of transplantation; yet the radiographic
evaluation after short-term follow-up showed that only three knees had
evidence of progression of joint arthrosis and narrowing in the involved
tibiofemoral compartment. Caution is warranted, however, in the interpretation
of these findings because of the short-term (twenty-four to sixty-nine-month)
duration of follow-up in this study. The long-term results in these patients
will depend on the concomitant arthrosis and function of the transplant.
The presence of a full-thickness femoral condylar defect with bone exposure
is a relative contraindication to meniscal transplantation. We believed that a
concomitant osteochondral autograft transfer procedure could be done without
increasing the complication rate or adversely affecting the functional
results. In this study, sixteen patients who otherwise would not have been
considered candidates for a meniscal allograft received the combined
procedure. There were no differences in complications, reoperations,
functional limitation, or pain symptoms at the time of the latest follow-up
between those who received an osteochondral autograft transfer and those who
did not. We recognize that the small number of cases prevents definitive
conclusions, and it is unknown whether the improvements noted postoperatively
were due to the transplant, the osteochondral autograft transfer, or both
procedures.
Again, in this small number of patients, we found no significant
differences between patients who had a concomitant ligament reconstructive
procedure with the meniscal allograft and those who did not. We are encouraged
that the arthroscopically assisted meniscal allograft technique has proved to
be a predictable procedure and that the addition of a ligament reconstruction
does not appear to impose substantial risks over those of the allograft
procedure alone.
Untreated lower-limb malalignment has been correlated with failed meniscal
allografts in several
studies40,64-66,
and we specifically excluded patients in whom the weight-bearing line was
<40% (varus) or >60% (valgus). In patients with such a deformity, we
perform a high tibial osteotomy approximately six months before meniscal
transplantation to allow healing of the osteotomy and to reduce the risk of
complications from a combined procedure.
Clinical Outcome of Meniscal Transplants
Several clinical studies have evaluated the use of cryopreserved meniscal
allografts34,35,37-40,67-69.
Van Arkel and de Boer presented a survival analysis of sixty-three consecutive
cryopreserved meniscal allografts that were followed from four to 126 months
postoperatively40.
Persistent pain or mechanical damage (a detached or torn allograft) was used
to determine allograft failure. The cumulative survival rates of lateral,
medial, and combined allografts in the same knee at a mean of sixty months
postoperatively were 76%, 50%, and 67%, respectively. Failure of lateral
allografts occurred at an average of fifty-three months and failure of medial
allografts, at a mean of twenty-five months postimplantation.
Potter et al.33
followed twenty-nine meniscal allografts with magnetic resonance imaging and
clinical examination for three to forty-one months postoperatively. Increased
signal intensity was detected in the posterior horn in fifteen knees, and
peripheral displacement at the body was noted in eleven knees; all of these
knees had moderate or severe chondral degeneration.
Noyes et al. described the results of ninety-six consecutive irradiated
meniscal allografts implanted into eighty-two
patients36,42.
Twenty-nine menisci in twenty-eight patients were removed prior to the minimum
two-year follow-up; this left sixty-seven meniscal allografts that were
followed for twenty-two to fifty-eight months postoperatively with magnetic
resonance imaging and clinical examination. The meniscal transplant failure
rate ranged from 6% (one of eighteen knees) in knees with normal or only mild
arthrosis on magnetic resonance imaging to 80% (twelve of fifteen knees) in
knees with advanced arthrosis. The relationship between the failure rate and
the increasing severity of joint arthrosis was significant (p < 0.001).
In the current study, eleven (28%) of our forty allografts failed. The mean
meniscal allograft displacement was only 2.2 mm under loaded imaging
conditions. However, nearly all of the allografts demonstrated signal
intensity alterations, a finding that has been reported by other
authors33,37,39,41.
We believe that these alterations were indicative of the remodeling
process.
Magnetic resonance imaging after meniscal transplantation typically showed
low signal intensity within the body of the meniscus, which was retained until
transplant remodeling. Ingrowth of cells into the transplant, removal of
portions of the dense well-formed collagen framework, and replacement with
more randomized and disorganized collagen tissues cause increased signal
intensity with a nonuniform patchy gray appearance. This occurred in fourteen
of twenty-nine meniscal transplants in this study. It is at this stage of the
remodeling process that alterations in mechanical properties and decreased
load-sharing capabilities may be
expected33. We
believe that all meniscal allografts undergo a deleterious remodeling process
at various time-periods after implantation, resulting in altered mechanical
properties and the potential for tearing, fragmentation, and degeneration
under joint-loading conditions. The long-term survival rates of meniscal
transplants are unknown at this time.
The weaknesses of this study include a small population and the short-term
follow-up (mean, forty months). Although a rigorous knee-rating system,
analysis of pain, and weight-bearing magnetic resonance images were used to
assess allograft characteristics, this provided only an indirect assessment of
true meniscal load-sharing function. It is not currently feasible to obtain
data regarding biomechanical properties or contact pressure patterns of
meniscal allografts in vivo. Furthermore, the inclusion of knees that had an
associated osteochondral autograft transfer or knee ligament reconstruction
procedure adds confounding variables, and we cannot determine which procedure
was responsible for the improvement in symptoms and knee function.
The strengths of this study include a consecutive series of patients
followed prospectively, a 100% rate of follow-up, results evaluated by an
independent senior researcher and not the surgeon, and the use of
weight-bearing magnetic resonance imaging and a reliable and valid knee-rating
system to determine the outcome. The classification of meniscal allograft
characteristics and the strict criteria for failure may not be comparable with
other clinical studies that did not use such a rating system.
In conclusion, the short-term results of meniscal transplantation are
encouraging as the majority of patients had improvement in knee function and
pain relief in the affected compartment. While this study did not determine
whether meniscal transplantation provides a chondroprotective effect, we
believe that the transplant should be performed earlier than was typically
done in the patients in this study. Eighty-five percent already had chondral
damage in the tibiofemoral compartment, a condition that is expected to
progress in the long term even after meniscal transplantation. The patients
with femoral condylar defects treated with a concomitant osteochondral
autograft also had substantial improvements in pain and function. Finally,
cruciate ligament instability can and should be corrected at the time of
meniscal transplantation.
The long-term function of the meniscal transplant remains questionable, as
the transplant appears to undergo a remodeling process that results in
alterations in its collagen fiber architecture that affect its load-sharing
capabilities and long-term survival. This procedure is indicated for patients
who have few other options for treatment after meniscectomy. They should be
advised that the procedure is not curative in the long term, and additional
surgery will most likely be required.
A table showing the effect of associated procedures on the Cincinnati
knee-rating system results 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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