Matt Kemp, who is an outfielder for the Los Angeles Dodgers,
will be unable to help the his team in the post season this year due to an MRI
showing swelling in one of the major weightbearing bones in Matt Kemp’s ankle,
the talus. Kemp initially injured
his ankle in a play at the plate against the Washington Nationals on July 21st. After missing 52 games on the disabled
list, he returned to play on September 16th. However, he was held out of
Saturday’s game due to soreness in his ankle. This prompted an MRI that revealed swelling in the talus,
taking Kemp out of the lineup in the post season.
What does swelling in
the ankle (talus) mean?
On an MRI after an ankle sprain injury, swelling in the
talus typically will mean that there is some cartilage damage in the bone,
called an osteochondral lesion.
When an ankle is sprained, a number of different structures can be
injured. In addition to the
ligaments and tendons around the ankle being torn, occasionally a small piece
of cartilage can chip off of the talus bone. This cartilage damage is usually not readily seen on x-rays,
but will often show up on MRI as bone swelling. A CT scan may be useful in determining the size of the
lesion.
How did this happen?
When there is an ankle sprain, many structures in the area can also be injured as well. In addition to ligaments tearing, the peroneal tendons (tendons on the outside of the ankle) can stretch and tear as well. Additionally, the ligament may tear off bone at its attachment site. Depending on the severity of the sprain, the cartilage may chip off if there was any impact in the area. According to reports, Matt Kemp's previous MRIs did not show any swelling of the bone. Therefore, this injury may have been a result of a loose, or unstable ankle. If the ligaments do not heal correctly, they may become loose. Ligaments are strong structures that help to prevent unwanted motion. When they are too loose, however, the ligaments may not be able to hold joints in place and there may be excess and unwanted motion at the joint. Over time, there may be rubbing of the bone due to these loose ligaments which may cause cartilage damage or bone swelling in the ankle bone. I suspect that the ligaments may be a little loose, causing a little movement in the ankle while Matt Kemp was playing. This small movement may have been enough to cause irritation of the ankle and possibly a cartilaginous injury.
What is the treatment
of an osteochondral lesion?
Treatment of an osteochondral lesion depends on the location
and severity of the lesion.
Lesions on the inside, or medial aspect, of the talus are usually deeper
and more stable. Lesions on the
outside, or lateral aspect, of the talus are usually shallower and wafer shaped
– making them less stable.
Osteochondral lesions can be classified as compression or bruising of
the bone (stage 1), partially detached (stage 2), completely detached but
non-displaced (stage 3), or completely detached and displaced in the ankle
joint (stage 4). Stage 1, 2, and
lateral stage 3 lesions are best treated conservatively with a period of
immobilization that includes a non-weightbearing below knee cast for six
weeks. If pain persists
after this period of immobilization, surgery may be indicated. Medial stage 3 and stage 4 lesions
are best treated with surgery.
What are the surgical
options for osteochondral lesions?
There are a number of procedures that can be done depending
on the size and depth of the lesion. Before surgery, the size and depth of the
lesion should be determined with a CT scan to help with planning the
appropriate procedure.
Microfracture surgery
Cartilage in general has a poor blood supply and it has poor
healing potential. Microfracture
surgery involves drilling holes into the lesion to stimulate blood flow in the
area and promote the formation of fibrocartilage. This procedure is fairly minimally invasive as it is often
done through a scope. This
procedure has good outcomes for smaller lesions.
Cartilage graft (OATS procedure)
A cartilage graft can be placed in the area of the osteochondral
defect to effectively replace damaged cartilage. This method is usually reserved for lesions of about 1 cm in
diameter. In this procedure, the osteochondral
lesion is punched out and replaced with a cartilage graft of identical size
from a donor. For the best
results, a graft is taken from the similar bone in which the osteochondral
defect is present as to recreate the anatomic contour of the joint as best as
possible. This is best done with a
cadaver bone that matches the affected ankle. Cadaver bones should be used within 14 days of it being
harvested and should be fresh, not frozen. Frozen grafts will deteriorate cartilage cells and reduce
the ability of the graft to successfully incorporate into the host.
Stem cells
Mesenchymal stem cells make up about 2-3 % of all blood
cells in bone marrow and they have the ability to differentiate into different
types of cell types if placed in the right environment. They also have the ability to stimulate
new blood vessel growth, which is important in developing avascular tissue such
as cartilage. Stem cells can be
separated from bone marrow that is harvested from the body and either injected
into the ankle joint or placed over the osteochondral lesion itself in a gel
form with a scaffold graft. The
stem cells will then differentiate into cartilage due to the growth factors and
signals that are present in the environment in which they were placed.
What should Matt Kemp
do?
The current treatment plan for Matt Kemp is immobilization in a non-weightbearing cast. This likely means that the lesion is either a stage 1, 2, or lateral stage 3 lesion and likely to heal with conservative treatment. It is very important to rest this injury because the talus bone does not have a great blood supply. Any additional movement or pressure to the lesion may prevent the lesion from healing. Over time, an untreated osteochondral lesion can lead to ankle arthritis. Therefore it is not an injury that he should play through, as it can cause further damage to the ankle. A CT scan would be useful in evaluating any cartilage or bone defect that may be present in the ankle. Should he continue to have pain and/or swelling to the ankle after his period of immobilization, surgery may be indicated. After immobilization, a period of rehab is needed. Range of motion and strengthening exercises are done to help strengthen the ankle. Assuming conservative treatment is successful, Matt Kemp should be back for spring training in 2014 with minimal residual effects from the ankle injury.
