Articular cartilage lacks a blood supply and thus is regarded as having
poor healing
potential1-3.
Specifically, it is widely accepted that a partial-thickness cartilage injury
cannot heal
spontaneously4-7.
Therefore, a variety of approaches are under investigation to improve
cartilage
healing1-3.
One of the options to facilitate healing is to recruit bone-marrow cells to
the injured site by penetrating the subchondral bone; however, previous
experimental and clinical studies have suggested that this approach typically
leads to healing by the formation of fibrocartilage-like tissue over long
periods of
time1-3.
We present a case in which successful fixation of partial-thickness
chondral fracture of the subchondral bone was achieved in the knee of an
adolescent. A core biopsy revealed complete healing of the fragment to the
subchondral bone without fibrous-tissue formation, with restoration of the
normal transition between the deep zone of cartilage and the subchondral bone.
To our knowledge, this is the first report in which the healing of a chondral
fragment to the lesion base has been demonstrated histologically. The parents
of our patient were informed that information concerning this case would be
submitted for publication.
An eleven-year-old boy twisted the left knee while kicking a soccer ball in
February 2001. The patient presented to our clinic nineteen days after the
injury because of persistent swelling. Physical examination revealed that the
left knee had full extension but a slight loss of flexion to 120°. There
was a joint effusion but no ligamentous laxity. Plain radiographs showed no
abnormality (Fig. 1). Magnetic
resonance imaging (Fig. 2) and
subsequent arthroscopy (Fig. 3,
A) confirmed the presence of an intra-articular free
cartilage fragment. There were no physical, radiographic, magnetic resonance
imaging, or arthroscopic findings that suggested previous patellar
dislocation. Macroscopically, the free fragment looked like normal cartilage
(Fig. 3, B). The
fragment was biopsied for histologic evaluation. The detached surface of the
fragment was covered with fibrous tissue
(Fig. 4, A). With
higher magnification, the substance of the fragment was found to be comprised
of normal cartilage tissue with apparently viable cells
(Fig. 4, B). Notably,
there was degeneration of the cartilage matrix in the deep zone, with some
proliferation of chondrocytes, and spindle-shaped (fibroblast-like) cells were
clustered in a layer covering the detached surface
(Fig. 4, C). The
matching defect on the lateral femoral condyle was covered with white tissue
(Fig. 3, C). With
probing, the surface of this tissue on the base of the lesion felt like soft
fibrocartilage. We therefore curetted away the surface tissue, and histologic
examination revealed that it consisted of hyaline cartilage matrix with
underlying subchondral bone. The cartilage matrix contained clusters of
chondrocytes, which are seen in association with both partial-thickness
cartilage injury and
osteoarthritis2
(Fig. 4, D).
The lesion was then repaired. After curettage of the bed, bleeding from the
surface was observed (Fig. 5,
A). This finding suggested that the chondral fracture had
occurred in the deep zone of the cartilage matrix and, further, that the
curettage had penetrated the subchondral bone. The fragment was then fixed to
the base of the lesion with four bioabsorbable pins (Neofix; Gunze, Kyoto,
Japan) (Fig. 5, B).
After surgery, the knee was immobilized in an above-the-knee cast at 45°
of flexion for three weeks. After removal of the cast, the patient began
passive and active range-of-motion exercises. Partial weight-bearing was
allowed at six weeks, followed by full weight-bearing at eight weeks.
Four months postoperatively, the patient had gained a full range of motion
without ligamentous laxity and had resumed the activities of daily living
without symptoms. Six months postoperatively, plain radiographs revealed
normal findings but a repeat magnetic resonance imaging scan revealed that the
reattached cartilage fragment was still distinguishable from the adjacent
cartilage tissue (Fig. 6), and
therefore it was difficult to determine whether the fragment was being
integrated into the adjacent cartilage tissue. With the patient's consent,
second-look arthroscopy was performed to evaluate healing at six months after
surgery. The surface of the reattached fragment appeared to be comprised of
normal cartilage, and it was difficult to distinguish its peripheral margins
(Fig. 7). A core biopsy was
done with use of a 14-gauge biopsy needle
(Fig. 8). The biopsy specimen
was taken from the center of the fragment and included subchondral bone to
allow for an assessment of the quality of the repair
(Fig. 8, A).
Histologically, the reattached cartilage was indistinguishable from normal
hyaline cartilage tissue in both the superficial zone
(Fig. 8, B) and the
deep zone (Fig. 8, C).
Notably, the fibrous tissue that had covered the deep surface of the detached
fragment prior to fixation (Fig. 4,
A) had disappeared and the osteochondral junction
appeared to have been restored (Fig. 8,
D). After second-look arthroscopy, the patient was
allowed to return to strenuous sports activity. At two years of follow-up, the
patient was clinically free from symptoms, had a full range of motion, and
continued to participate in strenuous sports activity. Plain radiographs
showed no degenerative changes. A magnetic resonance imaging scan obtained at
two years and nine months postoperatively revealed that the cartilage fragment
was completely healed to the femoral condyle and that the boundary with the
adjacent cartilage was smooth and indistinguishable
(Fig. 9).
Note: The authors thank Dr. Andrew L. Wallace, Imperial College
School of Medicine, London, England, and Dr. Rafael I. Pavlovich, Institute
for Orthopaedics, Arthroscopy and Sports Medicine, Sonora, Mexico, for
editorial assistance.