Pertinent Insights On Ankle Arthroscopy
There are three less commonly used portals that authors have described in the arthroscopic literature. The anatomical sites of these less commonly used portals have an increased risk of damaging nerves or blood vessels. Surgeons should only use these portals if they are unable to access the pathology within the joint from the three principal and safest portals I described previously.
The central anterior portal is located just lateral to the extensor hallucis longus tendon at the level of the tibiotalar joint. The anterior tibial vessels and deep peroneal nerve are at high risk for injury with this approach.
The posteromedial approach is located just medial to the Achilles tendon at the level of the joint line. This portal puts the posterior tibial vessels, tibial nerve, medial calcaneal nerve and flexor hallucis longus tendon at risk with this technique.
The final portal described in ankle arthroscopy is a transmalleolar approach through the lateral malleolus. Guhl described the lateral malleolar portal in 1988 for accessing osteochondral defects on the posterior aspect of the talus.4
Ensuring Appropriate Instrument Selection
After performing incisions and blunt dissection to the level of the capsule, the surgeon can use a trocar or an obturator to pierce the joint capsule and employ a cannula to maintain the portals after their establishment. Trocars are solid rods with a sharp pyramidal tip while an obturator is a solid rod with a blunt tip. The obturator is a much safer instrument for establishing a portal and surgeons should use this whenever possible to decrease the chance of damaging healthy cartilage when establishing the portals.
There is a wide array of instrumentation for arthroscopy. Paramount on this list is the arthroscope with a camera and light source to allow the surgeon to visualize the intra-articular space on a monitor. The camera comes in three different lens angles, which one can orient 0, 30 or 45 degrees from the shaft of the arthroscope. The angled lenses allow the surgeon to view the tibial or talar cartilage without the need to angulate the arthroscope and possibly score healthy cartilage with the camera.
Insert the camera into the joint through a cannula, which helps to maintain the portal during the procedure. The ingress and egress of fluid through the instrumentation aid in distending the joint space and synovium to maximize visibility within the joint. One can use lactated Ringer’s solution as it is the most physiologic fluid readily available.
Once the pathology is visible, there are a variety of instruments you can use to treat the patient. These include shavers, abraders, cutters, specialized instrumentation for grasping loose bodies, curettes and lasers. All of the equipment for ankle arthroscopy is available in different diameters with 2.7 mm and 4.0 mm instruments being the most commonly used sizes for the ankle joint.
A Brief Overview Of Four Terms For Instrument Manipulation
Ankle arthroscopy has four main terms that describe how surgeons manipulate the instrumentation within the joint.
• Scanning is the use of the camera to inspect the entire joint line visually. It allows the surgeon to locate the pathology and assess for further injuries that he or she may not have previously identified.
• Triangulation involves orienting the camera lens and an instrument within the ankle joint at the point of pathology at the same time. This principle allows the surgeon to inspect the pathology while the instrument manipulates it and visualize the location as the treatment occurs.
• Pistoning is the advancement and withdrawal of the camera within the joint space as the camera scans the joint. Pistoning allows the inspection of the talar neck, synovium and ankle gutters and recesses.
• The final basic principle of arthroscopy is rotation. Rotation enables one to visualize the areas around the lens in all directions without pistoning the camera.