Recent advances and future trends in foot and ankle arthroscopy

INTRODUCTION

Ankle arthroscopy (AA) is now a well-established alternative in the treatment armamentarium of the foot and ankle surgeon. In addition to being a diagnostic tool, it gives the surgeon therapeutic applications in the same sitting using a minimally invasive technique. Its evolution, however, was slow to reach present acceptance and reliability since the early systematic descriptions of this procedure in 1939^[1] using a 2.7 mm diameter arthroscope. Masaki Watanabe is regarded as a pioneer and “father of arthroscopy” with considerable success in knee arthroscopy.^[2] In 1972, he published the first series of 28 AA patients using a newly developed self-focusing small joint 1.7 mm arthroscope.^[3] From his series of 67 cadaveric arthroscopies, Chen, in 1976, further described the surgical technique and arthroscopic anatomy of the ankle joint.^[4] The inadequacy of instrumentation and surgical techniques to overcome the difficulties related to suboptimal visualization and poor access to the relevant damaged structures within such a constrained joint contributed to the slow uptake and popularity of AA. It also limited the indications for its early use to just diagnosis and treatment of loose bodies, soft tissue, or bony impingements, with reports of varying success.^[5-8] A 21-point systematic examination of the ankle joint was also developed to help with achieving a reproducible diagnostic examination of the ankle joint.^[7] These early arthroscopic procedures were performed through the anterior approach as adequate visualization and access to the central and more posterior aspects of the ankle joint were problematic.^[9,10] To improve the situation, a new invasive and fixed distraction device was introduced in the 1980s, using pins in the tibia and calcaneus.^[11] However, to avoid any added morbidity from the skeletal pin sites, a non-invasive distraction technique was also developed.^[12] Development and refinement of a separate posterior approach^[13] opened up the possibilities of accessing posterior ankle and subtalar joints pathologies. These improvements in instrumentation, joint access and visualisation made arthroscopic intervention possible for more pathologies, including for tendons around the ankle joint and smaller joints of the foot.^[14-17]

At the turn of the century, the indications for foot and AA were well established. These ranged from intra-articular loose bodies, osteochondral injuries,^[18] impingements, arthritis, tendinopathies, and various other sports pathologies around the ankle joints [Figure 1].^[15,19-21]

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Figure 1:

Illustrative historical developments in foot and ankle arthroscopy.

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The aim of this article is to give readers an update on the spectrum of foot and AA procedures currently being performed and highlight the upcoming developments.

AA – HOW IS IT PERFORMED?

The method of AA is largely dictated by the pathology that needs to be addressed. It is usually performed under general anesthesia and as an outpatient procedure. This can be supplemented with a regional block at surgeons or anesthetist discretion. Anteriorly placed portals with the patient in supine position are used for most anterior and centrally located pathology, whereas the posterior approach with patient prone to hind foot and subtalar problems. A lateral decubitus position has also been described that allows for the placement of both anterior and posterior portals with rotation of the same side hip as needed.^[22] A thorough knowledge of the foot and ankle anatomy is essential to guide safe and accurate placement of both anterior and posterior arthroscopic portals and to understand the pathology being investigated.

SET UP

Patient positioning is dependent on the surgeons preferred approach and the work to be done. Hence, patient can be supine or prone as desired. A tourniquet is usually applied above the knee and this can be placed in a thigh holder to help fix the limb and flex the hip joint. Alternatively, a bolster can be placed underneath knee to achieve 20–45° of knee flexion, along with a side support placed at thigh region to reduce hip external rotation.

INSTRUMENTATION

The instruments used in AA are similar to larger joints but on a smaller scale. Different length arthroscopes are available, with the shorter length allowing for a decreased lever arm effect. These arthroscopes usually have 30° or 70° viewing angle and come with 4 mm, 3.5 mm, or 2.7 mm diameter, the larger diameters can deliver more irrigation fluid and thus obviate the need for additional portals for this function. Even smaller 2.0 mm diameter arthroscopes have been developed for the smaller joints of the foot. A whole range of appropriately sized additional accessories including graspers, osteotomes, shavers, burrs, curettes, knives, punches, radiofrequency probes, and suction equipment is also available.

PORTAL PLACEMENT

There are three main portals considered as the workhorses of AA, the anterolateral, anteromedial, and posterolateral portals. Additional portals and entry points can be used as needed depending on the pathology being addressed. To help with accurate portal placement, the surgeon should use an indelible marker pen to mark out the position of important structures and landmarks around the ankle joint prior to inflating the tourniquet. These include the anterior dorsalis pedis artery, deep peroneal nerve, tibialis anterior tendon, great saphenous vein, peroneus tertius tendon, malleoli, and the joint line [Figure 2]. Because of their closeness to the anterolateral portal, it is critical that the superficial peroneal nerve and its branches are identified and marked. Its position is made more prominent by inversion with plantar flexion of the foot and passive flexion of the toes. A nick in the skin marks the portal entry point and a blunt trocar or mosquito forceps are used to spread the subcutaneous tissue and gain access into the distended joint.

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Figure 2:

Anterior ankle portals with landmarks. 1 = Ankle joint line, 2 = tibialis anterior tendon, 3 = lateral malleolus, 4 = superficial peroneal nerve, 5= anterolateral portal, 6= anteromedial portal.

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Posterolateral portal

The patient can be prone or in the semi-decubitus position. First of two posterior portals, posterolateral portal’s position can be marked just lateral to the Achilles tendon at a level of a line parallel with the sole and drawn from the tip of the lateral malleolus to meet the Achilles tendon [Figure 3]. A nick in the skin and mosquito forceps is used to spread the soft tissue and access the joint. It can also be made under direct vision after the arthroscope from the anteromedial portal is place in the posterior part of the joint, through the notch of Harty, to visualize tip of needle inserted just lateral to the Achilles tendon as described above. Once access is gained, a 4.0 mm 30° arthroscope is inserted. In the hind foot arthroscopy, this is regarded as the vision portal.

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Figure 3:

Posterior portals and landmarks. 1 = Achilles tendon, 2 = lateral malleolus, 3 = medial malleolus, 4 = peroneal tendons, 5 = posterolateral portal, 6 = line from tip of lateral malleolus, 7 = posteromedial malleolus.

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Posteromedial portal

This is made at the same level as the posterolateral portal on the medial aspect of the Achilles tendon [Figure 4]. A nick in the skin and mosquito forceps is used to spread the soft tissue and access the joint till the tip of the forceps is visualized through the posterolateral arthroscope. The forceps are then replaced with a shaver under direct vision. The shaver is used to remove the fatty tissue and joint capsule to expose the posterior aspect of the ankle and subtalar joint. Identification of the flexor hallucis longus (FHL) tendon by moving the first metatarsophalangeal joint is the first step before commencing the actual arthroscopic examination. The posterior tibia nerve and artery are at risk with this portal. This posteromedial portal is regarded as the work portal in this approach.

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Figure 4:

(a) Weight-bearing lateral view radiograph of left (L) ankle showing post traumatic bony spurs at anterior lip of distal tibia and dorsal aspect of neck of talus causing anterior ankle impingement. (b) Intraoperative fluoroscopy picture following resection of anterior ankle spurs demonstrating adequate excision. (c) Intraoperative arthroscopy view of ankle joint from lateral portal demonstrating adequate excision of distal tibial anterior bone spur using a burr.

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ANTERIOR ANKLE PATHOLOGY

Indications for anterior AA range include synovitis, anterior ankle impingement syndromes, osteochondral lesions of talus (OLT) ligamentous injury repair, ankle arthritis, and certain ankle fractures.

OLT

These are lesions caused by damage to the articular cartilage and also extending to the underlying bone with over 50% of these lesions occurring in the central parts of the talus. Patients often present with a history of ankle trauma, along with pain and swelling within the ankle joint. Localized and point tenderness in the OLT area is often difficult to elicit, particularly in the posteriorly placed lesions. Pre-operative CT imaging is beneficial to pinpoint the exact location of the lesion and direct the most appropriate surgical approach to be used. MRI imaging is also helpful in describing the morphology of the lesion including the extent of associated hyaline cartilage damage. Raikin et al., in their descriptive MRI study on localization and morphology of OLT, established a nine-grid scheme of the talar dome. In their study of 424 patients, they found that 53% of lesions occurred in the centromedial aspect of the talus and 26% in the centrolateral aspect of the talus.^[30]

Treatment of OLT is dependent on several factors including severity of symptoms, age, and size of lesions. Conservative treatment has been advocated for children and adolescents^[31] with good results; however, this is less successful in adults.^[18] Arthroscopic debridement and microfracture are now considered the first-line surgical treatment for symptomatic OLT. Good success rates for this treatment have been reported with one study of 50 patients showing maintenance of initial success from this surgical treatment with a median American Orthopaedic Foot and Ankle Society (AOFAS) score of 88 out of scale of 100 after a mean follow-up of 144 months.^[32] However, the size of the lesions has been shown to effect outcome of treatment. Studies have suggested lesions >15 mm in diameter carry higher risk of failure.^[33] For such lesions, the alternative options to microfracture include osteochondral autograft transplantation^[34] or matrix-induced autologous chondrocytes implantation.^[35]

POSTERIOR ANKLE AND HIND FOOT PATHOLOGY

Indications for posterior hind foot arthroscopy include loose bodies, posterior ankle impingement, FHL, and Achilles tendon problems, OLT, subtalar conditions, and Haglund’s deformity. The procedure is usually performed with the patient prone and on an outpatient basis. Two portal arthroscopic approaches are now well established and excision of small amount of fat and some of the posterior joint capsule will in addition give access to the subtalar joint.

ANKLE FRACTURE FIXATION

The high incidence of chondral lesions and other intra- articular abnormalities present following ankle fractures and other traumatic injuries is well known with a rate of almost 80% in a study of 288 patients.^[46] Arthroscopy allows for clear visualization and assessment of these and any associated syndesmotic and ligamentous injuries.^[47,48] There is also the potential for their concurrent treatment during internal fixation of ankle and talar fractures as the arthroscopy allows assessment of fracture reduction and articular congruity, in particular, the triplane injuries in children. Talar dome osteochondral fractures benefit from arthroscopy-assisted reduction of the fracture fragment and fixation under direct arthroscopic vision. Posterior dome osteochondral fractures are challenging to access using standard arthroscopy portals and attempts were made successfully using a transmalleolar approach through which the fracture fragment fixation screw was passed under arthroscopic view and the fragment fixed.^[49] A study comparing open fracture fixation with arthroscopy assisted fixation showed superior AOFAS scores in the arthroscopy assisted group after a 40-month follow-up period.^[50]

ANKLE ARTHRITIS AND ARTHODESIS

Arthroscopic ankle arthrodesis is usually performed with patient supine through the traditional anterior portals. Occasional use of an additional posterolateral portal to get better access to the posterior cartilage and lateral gutters can be used. Studies have shown an equivalent or better results including fusion rates, length of stay, and functional outcomes, when compared to an open procedure both in the short and long term.^[51,52] It has also been used to correct and achieve ankle fusion in the presence of greater than 15° planar deformity that has traditionally been used as a cutoff to proceed to open arthrodesis [Figure 5].^[52]

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Figure 5:

Intraoperative arthroscopy view of ankle joint from the medial portal demonstrating complete chondral loss along with eburnation of talar dome.

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HALLUX ARTHROSCOPY

Improvements in instrumentation have led to increasing interest in arthroscopic evaluation and treatment of disorders of the big toe. Indications for hallux arthroscopy include for hallux rigidus, hallux valgus deformity, loose bodies, and osteochondritis dissecans. In his case report from 1988, Bartlett described his technique of arthroscopic debridement treatment for osteochondritis dissecans of the first metatarsal head.^[16] Since then, further arthroscopic techniques have been described for hallux deformities including for lateral soft-tissue release, arthrodesis, and focal osteochondral lesions of the first metatarsophalangeal joint, all with good outcomes.^[53-55]

THE FUTURE

The gradual evolution of foot and ankle arthroscopic techniques from simple diagnostic to the current third- generation procedures has revolutionized foot and ankle diagnosis and treatment.^[56] Our understanding of chronic ankle instability has also evolved with recognition of the contribution of medial ankle ligament damage, leading to refinement of our treatment strategies. This has led to the development of arthroscopic reconstructive procedures of the anterior tibiotalar ligament portion of the deltoid ligament.^[57,58] As noted with other major joints, the development of modern orthobiologics and their delivery mechanisms has seen the emergence of a potential fourth generation of regenerative arthroscopic treatments for conditions such as OLT. Early results using techniques have shown at least similar outcomes compared to the more established microfracture treatments.^[59,60] The concept of office arthroscopy is becoming more popular due to technological advancements in fine caliber foot and ankle instrumentation. Studies have described safe and reliable examination and treatment of common foot and ankle pathologies.^[61,62]