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Arthroscopy of the Ankle and Subtalar Joints
Arthroscopy is a surgical technique that
involves the introduction of a small circular lens (2.0 to 6.0 mm in
diameter) into a joint for the purpose of inspection and possible
treatment. The arthroscope is an elongated tube possessing a series of
lenses that allow for the magnification of structures within the joint.
A camera is affixed to end of the arthroscope so that joint images can
be projected onto a television monitor. Small incisions (one-quarter
inch or less) are placed strategically around the joint to allow for
the introduction of the arthroscope, as well as other pieces of
equipment needed for the precise correction of joint injury. Arthoscopy vs. Arthrotomy (Open Technique) Arthroscopy
offers several advantages over classical "open joint" (arthrotomy)
techniques. First, arthroscopic evaluation and treatment only requires
small incisions in the joint capsule, limiting the degree of scarring
and trauma associated with surgery. Second, the environment within the
joint is more easily inspected by virtue of the magnification provided
by the arthroscope. Third, removal of damaged joint tissue or scarring
is achieved in a more precise manner as a consequence of the very fine,
specially designed equipment. Fourth, the joint is continuously bathed
in physiological fluids providing a healthier environment during
surgery. This is in contrast to open joint techniques where the
cartilage surface is exposed to air within the operating room,
potentially compromising its viability. Unfortunately, situations do
arise when the joint needs to be opened in order to achieve the
objectives of the surgical procedure. For example, certain cartilage
injuries within the ankle joint may be located in areas where
arthroscopic visualization is poor, or access to the lesion with
available equipment is nearly impossible. In these cases, even though
an arthrotomy was necessary due to inaccessibility, the arthroscope is
invaluable in specifically identifying the location, and extent of the
problem. Ankle and Subtalar Anatomy The ankle joint is comprised of three bones, the tibia (inner ankle and leg bone), the fibula (outer ankle and leg bone), and the talus
(odd shaped, lower ankle bone). The ankle joint space is found between
the talus and the tibia, as well as between the talus and the fibula. A
large majority of the articular surface of the talus is in contact with
the cartilage surface of the tibia. These two surfaces are slightly
dome shaped from front to back. The ankle joint allows the foot to
mobilize up (dorsiflexion) and down (plantarflexion). There are three
major ligaments associated with the outer part of the ankle joint: the Anterior Talofibular, Calcaneofibular, and Posterior Talofibular ligaments. There is one major ligament with several bands associated with the inner part of the joint: the Deltoid ligament. Together these ligaments guide motion and provide stability to the ankle joint. The lower ankle joint or subtalar joint
(below the talus) exists between the talus and the heel bone
(calcaneus). The subtalar joint is actually made up of two anatomically
distinct joints. These two joints are separated by a void or space,
which houses the two major ligamentous stabilizers of the subtalar
joint: the Interosseous Talocalcaneal and Cervical Ligaments. Further
stability is afforded to the subtalar joint by one of the three lateral
ankle ligaments (Calcaneofibular Ligament), and several bands of the
main inner or medial ankle ligament (Deltoid Ligament). The subtalar
joint allows the foot to pronate and supinate. Supination of the
subtalar joint involves movement of the foot in an inward direction, so
that the sole of the foot faces the opposite limb. Pronation of the
subtalar joint involves movement of the foot in an outward direction,
allowing the sole to face away from the opposite limb. Rearfoot and Ankle Inversion Injuries: Mechanism of Injury During
a common ankle sprain, the foot is forcibly rotated inward toward the
opposite leg. The inward movement of the foot is a motion well
accommodated by the lower ankle joint (subtalar joint), but not by the
upper or true ankle joint. Ultimately, the lower ankle joint comes to
the end of its available inward motion, and stops rather abruptly (the
lower ankle joint can be injured at this point). Continued inward
movement of the foot forces the ankle joint in a direction it is not
designed to accommodate. The lower ankle bone or talus is thus forcibly
directed inward, partially dislocating the talus out from under the
tibia and fibula. It is not uncommon for the outer ankle ligaments to
be partially or completely torn, resulting in joint instability.
Furthermore, the adjacent joint surfaces can collide or impinge during
the injury, resulting in disruption of the cartilage surface. Arthroscopy: Indications for usage Arthroscopy
is an effective tool for the evaluation and management of pain
localized to the ankle or lower ankle (subtalar) joints. Following an
ankle sprain, ligamentous scarring can occur within various regions of
the ankle or subtalar joints. Arthroscopy allows direct visualization
and precise removal of scar tissue with minimal joint trauma.
Generally, two to four portals or incisions are required for ankle
arthroscopy, and two or three for subtalar arthroscopy. Loose fragments
of bone, cartilage or ligament can be identified and removed through
the small portals in the joint capsule. Occasionally, small accessory
incisions may be necessary to remove larger fragments of tissue found
within the joint. Regions of the joint surface that have been injured
will commonly display an obvious defect or a loose flap of cartilage
that has been delaminated from the underlying bone. Not infrequently,
the joint surface will appear normal; however, gentle probing will
reveal an area of softness compared to surrounding cartilage. These
soft areas are regions of cartilage injury and will require removal of
the damaged cartilage. In some cases, physicians are drilling small
holes through these soft zones in order to promote re-adhesion of the
cartilage. In areas where there is an obvious defect in the cartilage
surface, the damaged cartilage is removed down to normal cartilage.
Following the removal of damaged cartilage, the exposed underlying bone
is drilled repetitively to facilitate bleeding into the base of the
injured area. The blood will form a clot across the full dimensions of
the defect. Over time the blood clot is converted to cartilage. The
repair cartilage is not of the same quality as was originally present;
however, the repair cartilage re-establishes near normal
surface-to-surface contact. In some cases, small plugs of normal
cartilage and bone can be removed from one location within the ankle
joint, and placed into an area of cartilage injury. Unfortunately,
transport of cartilage within the ankle joint necessitates an open
joint technique and cannot be performed arthroscopically. Arthroscopy has also been useful in assisting with the repair of fractures that involve the surfaces of the ankle joint (Pilon fractures or talar fractures).
In these cases, the arthroscope is used to visualize the fractured
joint surface as it is repaired to assure accurate realignment.
Arthroscopy has also been used to visualize the joint during removal of
the articular cartilage prior to fusion of the ankle joint. Conditions Where Arthroscopy may not be Useful Unfortunately,
arthroscopy is not helpful in certain types of joint injury. If a
cartilage lesion is located in the central or back portion of the
joint, many times the lesion cannot be accessed with the arthroscope.
In these cases, the tibia or inner ankle bone must be cut in order to
allow inspection and treatment of the lesion. Ankle fusions
cannot be performed arthroscopically if a large degree of malalignment
exists within the ankle joint itself. In these cases, the joint must be
opened and the joint surface remodeled to reduce the deformity.
Although some surgeons are repairing single ligament tears through the
arthroscope, this has not gained universal acceptance. Significant
joint instability associated with multi-ligament injury requires open
joint repair or reconstruction techniques. Arthroscopic Surgery of the Ankle and Subtalar Joints Arthroscopic
surgery of either the ankle or subtalar joints is generally considered
an outpatient (same day) surgical procedure. Pre-operatively or
intra-operatively, patients are usually given antibiotics to reduce the
risk of infection. The surgery can be performed under either general or
spinal anesthesia. Arthroscopy can also be performed under local
anesthesia with IV sedation. The latter procedure requires the
anesthesiologist to use a local anesthetic to block the large nerve
behind the knee joint (main nerve block). The surgeon will further
supplement the main block with local anesthetic infiltrated just above
the ankle joint. The patient is then kept in a twilight sleep with
medications infiltrated through the IV by the anesthesiologist.
Post-operatively, the ankle is lightly bandaged. The patient may be
placed in a removable cast boot or splint to keep the ankle at 90
degrees to the leg; however, gentle range of motion is recommended on a
regular basis after surgery. Following surgery, patients are usually
non-weight bearing for 7-14 days, and then are allowed to weight bear
as tolerated. If a large cartilage lesion was either drilled or cleaned
out, patients will remain non-weight bearing up to 4 weeks. The actual
duration of non-weight bearing will depend on the extent of the injury
and the type of treatment rendered. It is not uncommon for patients to
undergo physical therapy after surgery, especially if they had a
prolonged period of pain and disuse prior to surgery. Risks and Complications Associated with Ankle or Subtalar Arthroscopy Like
any other surgical procedure, arthroscopy has certain inherent risks
and complications. In the author's experience, these have been
uncommon. The literature sites injuries to the superficial nerves as
the most common complication after ankle arthroscopy. Most of these
nerve related injuries result in tingling, numbness, or occasionally
burning sensations across the outer part of the ankle onto the top of
the foot. Most of these sensations resolve over a period of 3-5 months.
Obviously, more significant nerve related injuries have been reported,
but they are uncommon. There is the risk of infection; this
complication is rarely seen with appropriate antibiotic prophylaxis
prior to surgery and sterile technique during surgery Conclusions Arthroscopy
of the ankle or subtalar joints has proven to be a valuable tool for
treating various injuries to these unique joints. The degree of joint
and soft tissue trauma associated with arthroscopy is no doubt less
than open joint techniques, resulting in somewhat faster healing times.
Immediate return to walking and sports is not usually recommended. The
joint can be often sore and swollen for several weeks after surgery.
Aggressive and rapid return to activity can result in a more prolonged
recovery time. Listen to physician instructions and follow carefully.
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