The subtalar joint is technically one of the hardest joints to scope. The problem primarily lies with the shape of the subtalar joint and variability of portal location. Unlike other joints, the subtalar joint does not have a well-defined anatomic portal due to variability in location of the sural nerve and peroneal tendons. Extreme care is necessary to avoid those structures. After entry into the joint, one then must contend with the curvature and slope of the sinus tarsi, interosseous ligament, middle facet, posterior facet and posterior space. Every surgeon seems to have his or her preferred patient position whether it be supine, lateral or prone, which poses challenges.
Unlike with ankle arthroscopy, when one is performing subtalar joint arthroscopy, the surgeon must acclimate to working with a short scope and be comfortable using the scope and shaver within inches of one another via portals that could be less than a cm apart. To make matters worse, the equipment consistently pistons in and out of the portals, essentially restarting the orientation process again and again. All of this adds time to the procedure. Subtalar joint arthroscopy is not fast and requires a lot of patience.
As outlined by Frey in 2009, one can utilize arthroscopy for surgical intervention as well as for diagnostic purposes.1 Frey elaborates that clinicians may employ subtalar arthroscopy for the treatment of osteophytes, chondromalacia, osteochondral lesions, loose bodies, arthrofibrosis, coalition and synovitis. Additionally, multiple authors have discussed arthroscopic calcaneal fracture reduction and arthroscopic arthrodesis.2-6
Many authors utilize the term “hindfoot arthroscopy” to group together endoscopic exploration of the peroneals, flexor hallucis longus, Haglund’s resection and even os trigonum resection with subtalar arthroscopy.8-9 For this column, let us take a closer look at the subtalar joint and hindfoot arthroscopy.
Analyzing Common Preoperative Diagnoses For Subtalar Arthroscopy
One of the most commonly treated conditions with subtalar arthroscopy is the non-specific diagnosis of sinus tarsi syndrome. Mansur and colleagues published a series of eight patients with recalcitrant sinus tarsi pain, all of whom had severe subtalar synovitis.10 In these cases, the majority of the synovitis was adjacent to the interosseous ligament. More importantly, all eight patients returned to sport within six months after arthroscopic intervention. For this study, synovitis was clearly a primary intra-articular finding, which is consistent with other research.11-12
Frey showed similar results in a 2009 study, finding that arthroscopy facilitated more accurate diagnosis of interosseous ligament tears in patients with sinus tarsi syndrome.1 In one of the largest series of subtalar joint arthroscopies (115 cases), Ahn and colleagues noted that synovitis was the most common intra-articular finding followed by arthritis, chondromalacia and arthrofibrosis.13 With 31 of these cases, they were able to more accurately diagnose interosseous ligament tears, cervical ligament tears and fibrous coalitions.
Pertinent Pearls In Determining Portal Placement
Knowledge of the various portals and associated anatomic landmarks are crucial to improving surgical outcomes and avoiding complications. As with most arthroscopy of the foot and ankle, traction devices are dependent on surgeon preference. Unlike with ankle arthroscopy, insufflating the subtalar joint in the beginning of the subtalar joint arthroscopy procedure is unnecessary. Simply confirming that the fluid flows in through the 18-gauge needle and out of the second or third portals confirms that the surgeon is actually in the joint prior to insertion of the cannulas, and subsequent insertion of the camera.
Lateral and posterior portal approaches are the most common as they enable access to the posterior facet and central aspect of the joint in front of the talus. When choosing portal placement, anatomic position in relationship to the surrounding nerves, tendons, ligaments and vasculature is important.
In looking at the lateral two-portal technique, Lintz and team described the first portal as within the sinus tarsi laterally and directed slightly posterior to utilize the interosseous ligament as the anterior border for orientation.14 They placed the second portal just anterior and slightly inferior to the distal aspect of the lateral malleolus. This placement shows the posterior facet.
As with any arthroscopy, orientation is key. We prefer to start with the angle of Gissane and identify the interosseous ligament to establish the anterior portion of the joint (see top photo). As we inspect the talus centrally, we start to follow the anterior aspect of the talus and sweep laterally to assess the lateral gutter of the joint. As one would see with ankle arthroscopy, we typically see not only synovitis but classic findings like tissue impingement, plica and meniscoid lesions when using subtalar joint arthroscopy.
Muñoz and Eckholt have described additional portals for subtalar joint arthroscopy.11 Commonly utilized with the lateral approach, the posterolateral portal would be at the level of the distal lateral malleolus, just lateral to the Achilles tendon to avoid damage to the sural nerve. These authors also described a medial portal, extending from the medial aspect of the tarsal canal, to gain further access to the posterior facet. Employing fluoroscopic guidance, one would place the needle into the medial portion of the canal first with subsequent introduction of the cannula or working instruments.
The senior author rarely, if ever, utilizes this portal since he often gains acceptable visualization from the lateral side looking medially. However, on rare occasions, as Muñoz and Eckholt suggest, identifying and debriding middle facet coalitions is easier via the medial portal.11 One must understand, just as one would do with ankle arthroscopy, the surgeon needs to work from one portal and visualize from the other, at times alternating to achieve optimal visualization.
What The Surgeon Should Know About Necessary Equipment
Although typical equipment is up to surgeon preference, Siddiqui and colleagues used a 2.4 mm, zero degree arthroscope.12 Sossa and colleagues suggested using a short 30 degree, 2.7 mm arthroscope and a 2.9 mm shaver.15 However, if utilizing a posterior portal, a longer scope would be indicated. Similarly, a joint distractor may or may not be necessary depending on the planned procedure. Numerous authors propose joint distraction but the authors of this column typically do not utilize joint distraction, except in the case of subtalar arthrodesis.16,17
At the ankle arthroscopy course at St. Louis University, where the senior author is a faculty member, we routinely utilize a standard ankle 4.0 mm scope and 3.5/4.0 mm shavers for the subtalar portions of the lab. Due to the helpful improvement in visualization with larger scopes, we will routinely have the larger equipment available for all of our cases. Once you have a safe entry into the joint, the size of the equipment becomes immaterial.
Also similar to ankle arthroscopy procedures, when we perform subtalar joint arthroscopy, we utilize lidocaine with epinephrine, 1%, 1:100,000, using 20 cc within a 1,000 cc IV bag of normal saline, which assists with intra-articular bleeding.
We prefer to utilize temperature-controlled thermal wands for radiofrequency ablation with options including OPES™ (Arthrex), SERFAS (Stryker) or TAC-S (Smith & Nephew). All of these thermal wands fit within the subtalar joint through the portals. They do an excellent job in reducing intra-articular bleeding, facilitating synovectomy, and even enabling one to perform capsular shrinkage. The surgeon is also able to tighten up the interosseous ligament and subtalar capsule. The hard part is visualization of the middle facet. There is often a large amount of debris blocking the view of the medial joint (see second through fourth photos above).
Important Considerations In The Post-Traumatic Patient
Post-traumatic cases are often the most challenging, especially when imaging shows no obvious pathology but arthrofibrosis can still be present. This is relevant when considering open reduction and internal fixation (ORIF) after surgical repair of calcaneal or talar fractures.
One of our patients, a soldier, sustained a Hawkins type III talar fracture, which required ORIF. Subsequent ankle arthroscopy revealed significant arthrofibrosis but he continued to have chronic pain as he resumed running. Imaging was unimpressive. He had restriction in his subtalar joint range of motion and diagnostic sinus tarsi injection yielded significant relief. Subtalar arthroscopy found just as much fibrosis in the subtalar joint as we saw in his ankle arthroscopy. Additionally, the patient had grade III-IV chondromalacia. He eventually went on to a subtalar fusion.
Examining Post-Operative Expectations
We feel that patients who have subtalar arthroscopy can return to weightbearing one week post-op regardless of the procedure. We routinely start passive ankle and subtalar range of motion the day after surgery. For diagnostic arthroscopy with minimal debridement, we typically begin weightbearing the same day as surgery.
In conclusion, subtalar arthroscopy is increasing in popularity, at least within the literature. Clinicians may utilize this procedure for a variety of conditions with sinus tarsi syndrome being the primary preoperative diagnosis. One can infer from current knowledge of this procedure that this minimally invasive joint operation is reproducible and has fairly positive outcomes with minimal complications.
Dr. Spitalny is a staff podiatrist at the General Leonard Wood Army Community Hospital in Ft. Leonard Wood, MO, and adjunct faculty with the DePaul Podiatric Surgical Residency Program in St. Louis.
Dr. McKee is a third-year resident with the DePaul Podiatric Surgical Residency Program in St. Louis.
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