Keywords
knee - osteochondritis dissecans - arthroscopy - orthopedics - surgery
Schlüsselwörter
Knie - Osteochondritis dissecans - Arthroskopie - Orthopädie - Chirurgie
Abbreviations
LFC:
lateral femoral condyle
MFC:
medial femoral condyle
MRI:
magnetic resonance imaging
OD:
osteochondritis dissecans
Background
Osteochondritis dissecans (OD) is one of the most common cartilage lesions of the
knee and
in approximately 85% of cases, the weight-bearing surface of the medial femoral condyle
(MFC)
is involved [1]. Of the
remaining patients, 13% experience lesions of the lateral femoral condyle (LFC) and
only 2%
exhibit defects in the trochlear notch [1]. These uncommon lesions of the LFC are frequently associated with an
intact discoid meniscus. Sometimes the exact location of the OD lesion is strictly
related to
a complete or incomplete discoid meniscal tear.
The exact etiology of OD is still unclear and traumatic, genetic, and ischemic causes
have
all been proposed as possible causes. The onset of OD is often subtle, and its symptoms
depend
on both the patient’s age and disease progression at presentation [2]
[3]. Sometimes, asymptomatic OD can be
accidentally discovered on plain radiographs taken for other reasons, while advanced
stages
can have a presentation pretty similar to other common knee injuries. Conservative
treatment
is recommended if the lesions are stable with no loose bodies or there are open physes.
Physical therapy strategies include isometric quadricep exercises in addition to stretching
and soft tissue modalities. Return to physical and work activities are generally allowed
after
resolution of pain symptoms, a normal clinical examination, and if X-rays and magnetic
resonance imaging (MRI) show signs of OD healing. Surgical intervention is currently
recommended as the primary treatment in symptomatic adults with unstable chondral
lesions or
in case of concomitant loose bodies.
Is hypothesis [2]
is that OD of the knee represents a separation of an accessory ossification nucleus
of the
distal femoral epiphysis, which is partially attached during maturation, but it may
be
completely separate if exposed to trauma. For this reason, the type of sport practiced
by
younger individuals can be an important risk factor. Other researchers have identified
a
mutation in the ACAN gene, which is important for cartilage function, as responsible
for
dominant familial OD [3]. This dominant inheritance is easily seen in some cases, such as a
family in which three out of four daughters developed bilateral OD [4].
Conversely, earlier studies such as that of Petrie [5] refute the idea that OD is a familial
inherited disorder but rather suggest it is a “disorder produced by different etiologies”.
Interestingly, the aforementioned studies provide a peculiar juxtaposition of the
genetic
component of OD. It has been also proposed that the repetitive microtrauma may cause
OD.
OD is subdivided into juvenile and adult forms. It is classified based on its anatomical
location, surgical appearance, MRI findings, and patient age. The juvenile form has
a better
prognosis than the adult form [1]
[6]. The clinical presentation of this pathological condition is
unspecific. The majority of patients present a stable chondral lesion and pain in
the anterior
portion of the knee, which is frequently correlated with physical activity. Sometimes
patients
may complain about knee instability and may present antalgic gait [7]. With palpation, it is generally possible
to detect an area of more intense pain in the lateral part of the medial femoral condyle,
although Wilson’s sign is not always present. Patients generally present edema and
crepitation
in the knee [8].
Imaging studies have the aim of characterizing the lesion, monitoring its healing,
and
determining the prognosis for conservative treatment [9]. MRI is extremely useful for determining
the size of the lesion, status of the cartilage, and viability of the subchondral
bone. The
best treatment for OD of the knee is still debated.
Case Description
A 21-year-old male complained of pain at the right knee with a catching sensation
during
active joint motion. Physical examination revealed moderate swelling and a locked
right knee
at 15° of flexion without any abnormality in the leg’s alignment.
MRI showed an area of OD with a bone lesion of 34 × 20 mm in the center of the
weight-bearing area of the medial femoral condyle ([Fig. 1]
a,b) with bone marrow edema. In addition,
two loose bodies were seen ([Fig. 1]
c). After talking with the family, we
decided to proceed with an arthroscopic treatment.
Fig. 1
a OD bone lesion in the MRI T2W fat sat
coronal plane (red arrow). b OD bone lesion in the MRI T2W fat
sat sagittal plane (red arrow). c One of two loose bodies in the
MRI T2W fat sat coronal plane (blue arrow).
The arthroscopic examination revealed a 2.8-cm by 2.5-cm displaced osteochondral fragment
from the medial femoral condyle and two articular loose bodies: the first one the
size of
21 mm length located between the patella and the medial femoral condyle, the second
one the
size of 10 mm length anterior to the ventral part of the medial femoral condyle. The
OD defect
was 0.7 cm in depth and contained poor quality scar tissue. It was considered that
the
osteochondral flap had lower potential for healing, so the fragment was simply removed
with
the two concomitant loose bodies ([Fig. 2]). A decision was thus made to proceed with repairing the chondral
lesion with a microfracture procedure ([Fig. 3]) and implantation of a 3D hyaluronan-based scaffold (Hyalofast)
([Fig. 4]).
Fig. 2
One displaced fragment (red arrow) and two cartilage loose bodies
(blue arrows).
Fig. 3
Subchondral socket of the medial condyle treated with
microfractures.
Fig. 4
Implantation of a 3D hyaluronic scaffold (yellow arrow).
Weight-bearing was not allowed for 6 weeks and passive and active range of motion
exercises were performed during this period. Full weight-bearing was allowed at 2
months.
After 3 months from the previous arthroscopic surgery, the same patient returned with
painful swelling of his right knee and a locked knee at 20° of flexion lasting for
1 day. A
new MRI examination showed a new wide unstable chondral flap originating from the
posterior
border of the previous OD lesion with a 20-mm transverse diameter × 26-mm anteroposterior
diameter ([Fig. 5]). After a
discussion with the patient and his family, we decided to proceed with an open surgery
in
order to stabilize the large osteochondral fragment.
Fig. 5
Large cartilage flap near the treated lesion. a MRI T2W fat sat sagittal plane (green arrow). b MRI
T2W fat sat coronal plane (green arrow).
During the open examination, the previous OD lesion was carefully inspected and seemed
to
be completely covered by good quality regenerative tissue ([Fig. 6]
a) at the inferior
medial part of the healing lesion. A 3 cm2 chondral flap, 0.5 cm in depth, detached
from the medial femoral condyle was seen ([Fig. 6]
b).
Fig. 6
a Regenerated tissue healed the cartilage
damage (red arrow). b Osteochondral flap (green arrow). c 1st PLP pin fixed (light blue arrow). d
Preparing fixation of 2nd PLP pin (light blue arrow).
The peripheral margins of the flap were cleaned, and a subchondral crater was curetted
to
remove fibrous tissue and improve vascularity on the femoral side. After performing
this step,
in order to restore the bony defect, the cured flap was fixed using bioabsorbable
pins (PLLA
Chondral Dart, Munich, Germany), three chondral darts, size 18 × 1.3 mm ([Fig. 6]
c,d), and one central
bio-compression screw, size 3.0 × 20 mm (Arthrex, Naples, FL, USA).
At the end of surgical procedure, the stability of the fragment fixation was checked
both
in flexion and extension.
Outcome and Follow-up
The patient was advised non-weight-bearing for 4 weeks, and exercises for range of
motion
were started the day after surgery. At the 3-month follow-up after the second surgery,
the
patient presented an excellent functional recovery of the left knee without limitations
of
range of motion.
The MRI showed early signs of osteointegration and a reduction of the chondral flap,
with
evidence of the bioabsorbable chondral dart pin still on site, both in the axial coronal
plane
([Fig. 7]
a,b) and in the sagittal plane, where the bio-compression screw was also visualized
in a good position ([Fig. 8]
a,b). In addition, a reduced reactive synovitis and intra-articular
effusion of the knee were found.
Fig. 7
Three chondral dart pins (light blue arrows) and a bio-compression
screw (orange arrow) in place in medial femoral condyle flap. a
MRI T2W fat sat axial plane. b MRI T2W fat sat coronal
plane.
Fig. 8
MRI T2W fat sat sagittal plane. a Chondral
dart pins in place (light blue arrows). b Bio-compression screw
in place (orange arrow).
Discussion
The best treatment for OD of the knee is still debated. Several procedures have been
proposed to treat OD lesions, but the gold standard technique remains controversial.
The lack of a standard operative treatment is principally due to a large number of
different shapes, sizes, or locations of focal chondral or osteochondral knee lesions
from a
scientific or routine clinical care point of view. The currently available clinical
options
complement each other in terms of their indication and have recently been differentiated
into
those with reparative or restorative properties [10]
[11].
Reparative methods (such as bone marrow-stimulating techniques with and without
biomaterial augmentation) are characterized by the formation of fibrous cartilage
[12]
[13]
[14]
[15], whereas restorative
methods such as autologous (OAT) or allogeneic osteochondral transfer (OCA) and autologous
chondrocyte implantation (ACI) form cartilage with hyaline properties.
There is increasing evidence from various studies with longer follow-up periods that
restorative procedures have better long-term results with lower failure rates [16]
[17]
[18]
[19].
If the preservation of the fragment is not possible, there is a general consensus
that the
large cartilage defect should be filled with osteochondral autografts or allograft
plugs.
The cell-free hyaluronic acid-based scaffold (HYALOFAST, Bedford, MA, USA) is a
bioscaffold that stimulates new cartilage growth and is considered a valid option
in treating
OD. Hyalofast is a non-woven biodegradable hyaluronic acid-based scaffold for hyaline-like
cartilage regeneration. It captures mesenchymal stem cells (MSCs) to heal both chondral
and
OCL in the knee and ankle. The MSCs secrete paracrine factors, which modulate the
immune
response of the host, facilitate angiogenesis, improve cell migration and survival,
and
prevent fibrosis. Once instilled, it keeps supporting MSC attachment, proliferation,
and
differentiation that will plug the lesion with new cartilage. Studies demonstrated
that the
treatment of OD with Hyalofast in combination with microfractures showed significant
improvement in VAS and AOFAS scores for lesions deeper than 7 mm with no postoperative
complications. Further, it was demonstrated that, comparing the arthroscopic treatment
of OD
with nanofracture alone with the use of Hyalofast, the cartilage quality, clinical,
and
radiological outcomes were better in the patient treated with the bioscaffold [15]
[16].
Regarding the approach, various methods have been used for internal fixation [10]
[11]
[12] of displaced chondral
fragments. Operative treatment includes a variety of techniques, such as the following:
arthroscopic drilling, mosaicplasty, arthroplasty through abrasion, microfracture,
osteochondral grafts, autologous implantation of chondrocytes, and fixation of fragments
[13]
[14].
An arthroscopic approach represents the best surgical option in symptomatic individuals
with failed conservative treatment or in skeletally immature patients. If the OD lesion
was
proven to be stable during arthroscopy, the patient may undergo subchondral drilling,
which
stimulates the formation of fibrocartilage tissue. However, there are some difficulties
to
assess the real extension of an OD lesion by arthroscopy and sometimes the unstable
margins of
the lesion may be left untreated.
Although the procedure performed arthroscopically can reduce the risk of persistent
ligamentous laxity and reduce open surgery-related morbidity, it has as its main limitation
the poor visualization of the more peripheral and hidden margins of the chondral lesion.
OD
results in tissue alteration through a potentially slow-growing expansive process,
therefore
MRI images may not document areas that, in reality, are already undergoing pathologic
alteration. We believe that supra-marginal resection and curettage should be warranted
even in
the young subject and if this may not be warranted, then the option of open surgery
should be
considered.
Lesions to the medial femoral condyle could be associated with varus alignment, while
lesions to the lateral femoral condyle are seen in patients with valgus malalignment.
Common
risk factors for failed fixation of OD lesions include unstable lesions to the lateral
femoral
condyle, screw breakage, older age, and closed physes. Knee realignment defects can
be avoided
with the proper use of reabsorbable pins; this procedure is made easier and more precise
precisely by using an open approach.
In our experience, we preferred to proceed to microfractures and arthroscopic OD repair
with a 3D hyaluronic scaffold at first because we were not able to assess the presence
of
unstable margins in the remaining portion of medial femoral condyle.
However, in situations where functional recovery does not occur adequately or when
areas
of osteochondritis are still present due to visualization problems during the first
procedure,
a revision by open surgery should, in our opinion, be considered.
Open revision surgery allowed us a more accurate assessment of the OD area to provide
an
effective fixation of the chondral flap and in this case, this should have been done
after
seeing the first MRI. Finally, the use of a bio-compression screw system (Arthrex,
Naples, FL,
USA) was effective and resolutive for the large flap fixation. In our opinion, the
procedure
described here should always be performed together in a one-step surgical session
to treat
large OD lesions, which are too demanding to address arthroscopically.
Conclusion
In treating ODs with unclear margins and the presence of loose bodies through an
arthroscopic approach, a 3D hyaluronic scaffold is the most suitable choice, as the
surgical
operator is often not able to assess the presence of unstable margins in the remaining
portion
of medial femoral condyle.
In situations where functional recovery does not occur adequately or areas of
osteochondritis are still present due to visualization problems during the first procedure,
a
revision by open surgery should, in our opinion, be considered. In selected patients
with
large and unstable chondral lesions, the combination of open fixation and implantation
of a
hyaluronan-based scaffold may represent a valid alternative to autologous grafting
and should
be performed directly with an open surgery approach.
-
In younger patients with OD, the combination of open fixation and implantation of
a
hyaluronan-based scaffold may represent a valid alternative to autologous
grafting.
-
OD is a common cartilage lesion of the knee with subtle clinical onset.
-
Conservative treatment of OD is recommended if the lesions are stable with no loose
bodies or there are open physes. Surgical intervention is currently recommended as
the
primary treatment in symptomatic adults with unstable chondral lesions or in cases
of
concomitant loose bodies.
