Arthroscopic surgery of the ankle and hindfoot is increasingly popular. Arthroscopy for visualization of joints was reported in cadavers in 1931, this included the ankle1.
The advantage of arthroscopic surgery is in having a technique that can assist with both diagnosis and treatment of pathologies in the ankle and hindfoot, while minimizing the collateral damage to the soft tissue envelope. The aim is to reduce the morbidity associated with the soft tissue stripping, allowing early discharge from hospital, faster rehabilitation, improved healing, and fewer complications. Classically, arthroscopy is used for intra-articular pathologies, although its versatility has led to a more recent increase in its use for tendon and ligament abnormalities.
Arthroscopy is a surgical tool. It is only employed after meticulous assessment, both clinically and radiologically.
The aim of clinical assessment is to establish a diagnosis, its functional impact, to record the patient’s comorbidities, and to counsel the patient as to the expected outcome of the arthroscopic intervention. Clinical assessment uses the systematic interview technique and features of examination outlined in Table 12.1.
|Symptoms||Soreness, stiffness, swelling, stability, shape|
|Function||Mobility, work, activities of daily living, sport|
|Gait||Velocity: stride; length: cadence|
|Stance tests||Ski stance dorsiflexion, double stance heel raise, single stance heel raise, weightbearing supination, heel rock|
|Range of movement||Active–passive|
Radiological examination should include a weightbearing AP view of the ankle, with an additional mortise view if deemed necessary; a weightbearing lateral view of the whole foot and ankle; a dorsoplantar weightbearing view of the foot; and an oblique view of the foot. Additional views may be of assistance, for example a limb alignment view for assessment of deformity, and an ankle anteromedial oblique impingement view is helpful for medial bony impingement from talar neck osteophytes.
Computed tomography scanning is useful to evaluate deformity, the presence of occult arthritis, tarsal coalitions, and occult fractures. The use of SPECT-CT scanning may be helpful in better localizing pathology. Magnetic resonance imaging can provide useful additional information regarding the soft tissue envelope, particularly the ligaments and tendons, but also the presence of bone edema, infection, and avascular necrosis (AVN). Ultrasound is a valuable dynamic tool, particularly in the assessment of pathology and trauma in tendons and ligaments. Image-guided joint injections of local anesthetic and contrast medium also help in localization.
A variety of techniques of positioning and joint distraction are available. The authors prefer a simple set up, with the patient placed supine in a marginal head-down position. An ipsilateral bolster under the buttock is used to correct external rotation and align the ankle in a neutral position. The lower leg is placed on a thick cushion, flexing the knee to approximately 20°. Traction, if required, can be applied through an ankle strap, attached to a fixed arm at the end of the table (Figure 12.1). The traction is increased and decreased not by any complex mechanism, but by elevating or depressing the end of the table. The standard 30°, 4.0 mm arthroscope is the workhorse, but narrower diameters (2.7 mm “Panvision”) are preferable for smaller and tighter ankles, as well as for children. A reliable and stable fluid-management system with a relatively low-pressure setting is employed. A camera system should allow an adjustment of aperture and of focus. It should be routine to record pictures or videos.
Figure 12.1 Shows the position to allow traction, with the knee slightly bent and the initial access achieved with a hypodermic needle. A 4.0 mm arthroscope is inserted in the anteromedial portal.
An initial “examination under anesthetic” should be recorded. This should include stability in the sagittal and coronal planes. Three portals are used regularly (Figure 12.2):
the anteromedial, which is medial to the tibialis anterior
the medial midline, between the tibialis anterior and extensor hallucis longus
the anterolateral, which is just lateral to the extensor digitorum longus.
The level of the ankle joint is usually determined with a small hypodermic needle. The tibialis anterior, the extensor digitorum longus, and the lateral branch or trunk of the superficial peroneal nerve are marked if possible. A technique for identifying the superficial peroneal nerve in thinner patients is to hold the fourth toe plantar flexed and invert the foot. The nerve can usually be seen and felt subcutaneously. It is important to note that the structures can shift horizontally when traction is applied.
Figure 12.2 The commonly used anterior portals for ankle arthroscopy. Red: anteromedial; mauve: medial midline; yellow: anterolateral.
The anteromedial and anterolateral portals are the most commonly used. The medial portal is established first, with a skin incision being made with a knife followed by deep dissection to the joint with fine scissors. A blunt trocar within the arthroscope sheath is then used to establish access, before introducing the arthroscope into the anterior recess of the ankle. While traction allows easy initial access to the joint, it is often necessary to release the traction before undertaking surgery in the anterior recesses of the ankle, as the ligament distraction increases soft tissue tension and thereby increases the risk of neurovascular injury. If the anteromedial portal is established first, the light can be used to transilluminate the lateral superficial structures and reduce the risk of damage to the superficial peroneal nerve. Once the two portals are established the initial view may be limited by fat, synovitis, or scarring within the anterior gutter. This can be removed using a 3.5 power-assisted shaver with suction. Care should be taken to keep the resection device facing backward into the joint to prevent iatrogenic damage to the anterior neurovascular bundle. Once the anterior gutter is cleared, a systematic review of the ankle can be performed (Figure 12.3).
Figure 12.3 The systematic review of the ankle joint. 1: tibiofibular syndesmosis; 2: tibial plafond; 3: talar dome; 4: posteromedial recess; 5: anterior margin of the tibia.
Systematic review of the joint starts on the opposite side of the joint to the primary portal. Thus we work from the anterior inferior tibiofibular ligament visualizing the tibiofibular syndesmosis, the articular surfaces of the lateral sides of the talus and the tibia, the posterior recess of the inferior tibiofibular joint, the posterior inferior tibiofibular ligament, and the posterior transverse intermalleolar ligament. This leads you across to the posteromedial corner. As one returns anteriorly, the superior part of the medial gutter can be inspected with the medial surfaces of the joint. Once you have returned to the anterior recess the traction can be temporarily removed and the deeper part of the medial gutter and the deltoid ligament can be visualized. The anterior recess can be further inspected – particularly the talar neck. This brings you back to the lateral gutter allowing you to view the anterior talofibular ligament. At this point it is important to check the stability of the inferior tibiofibular joint with the traction off. At all stages, the joint surfaces of both the tibia and talus should be carefully reviewed.
Posterior Ankle Arthroscopy
Approaches to the posterior ankle joint and posterior subtalar joint can be performed with the patient in the prone position2 or the lateral position. No distraction is required. Posteromedial and posterolateral portals can be used adjacent to either side of the tendo Achillis, at the level of the tip of the fibula. It is necessary to take care to avoid damage to the sural nerve laterally and the posterior tibial nerve medially during portal placement.
Alternative portal placements may be helpful. If the patient is in the lateral position the ankle can be instrumented or visualized through two posterolateral incisions – one close to the peroneal tendons and one close to the tendo Achillis. The arthroscope is introduced into the lateral portal. A soft tissue resector is then introduced medially (Figure 12.4). The resector is tapped against the arthroscope and then, when localized, the resector is used to clear a space in the fat. As a pocket is created the visualization improves and the FHL tendon comes into view. It is critical to remain lateral to the FHL tendon, until adequate visualization is obtained – this avoids inadvertent damage to the posterior tibial artery and nerve (Figure 12.5). Once the posterior ankle capsule and fat are removed, the transverse tibiofibular and talofibular ligaments, the posterior ankle joint, and the subtalar joint can be viewed.
Figure 12.4 The set up for posterior ankle and subtalar arthroscopy. The “bad” leg is down. The ankle (superior) and subtalar portals are marked.
Figure 12.5 The arthroscope is introduced toward the second toe. The shaver is introduced medially, and located initially by tapping it against the arthroscope.
Soft Tissue Pathology
The pathologies affecting the synovium and soft tissues are numerous and are outlined in Table 12.2. A common indication for arthroscopy is persistent anterior ankle pain, with or without instability, following an ankle “sprain.” The patient usually presents with anterolateral pain, from synovitis, fibrosis, or scarring, which impinges on ankle dorsiflexion3. The impingement is from a mass of fibrotic tissue, which builds up in the anterolateral ankle and resembles the meniscus of the knee – a “meniscoid lesion” (Figure 12.6a). Arthroscopic resection is easily undertaken with a soft tissue shaver. Such surgery has a 90% rate of success with purely soft tissue lesions4–5, but the success rate is lower if there is articular surface damage or arthrosis. It is important to also assess the syndesmosis6, and deltoid ligament. Impingement lesions can also occur anteromedially or posteriorly. On occasions the inferior margin of the anterior inferior tibiofibular ligament can impinge on the lateral talar dome – in this case it is known as Bassett’s ligament (Figure 12.6b). Arthroscopic resection of the prominent ligament is effective7.
|Soft tissue and synovial pathology|
|Inflammation:||inflammatory arthropathy, crystal arthropathy, hemophilia|
|Neoplasia:||pigmented villonodular synovitis, synovial osteochondromatosis|
|Trauma:||fibrosis, ligament injuries, scarring, impingement|
(a) A meniscoid lesion.
(b) A Bassett’s ligament (arrow) that was impinging on the talar dome.
Anterior bony impingement of the ankle is a common indication for arthroscopy. The usual sites are an anterolateral tibial or a medial talar neck osteophyte. Osteophytes also occur on the anterior edges, as well as the tips, of the medial and lateral malleoli. They may also be seen on the lateral shoulder of the neck of the talus. Removal of an anterior tibial osteophyte is performed using a 3.5 mm barrel burr, introduced through the anterolateral portal. The normal tibia above the osteophytic shelf is identified and the osteophyte is resected to a level flush with the anterior face of the tibia. Adequate resection is also marked when the articular cartilage returns to normal. Repeated dorsiflexion of the ankle helps identify adequate clearance of the impingement. The areas that are easily missed include the extreme anterolateral corner of the tibia, and the front of the medial malleolus. Results suggest 90% of patients are improved following surgery, although this is reduced to 50% if the joint space is narrowed on preoperative radiographs8–9.
It has also been shown that ossicles that are symptomatic and enhance on MRI scanning respond well to arthroscopic excision10.
As well as anterior impingement, posterior ankle impingement syndrome is increasingly recognized in ballet dancers and athletes. The typical history is of posterior, or posteromedial, ankle pain worsened by plantar flexion. Posterior ankle impingement is thought to arise from osseous impingement between the posterior process of the talus, or an os trigonum, and the tibia. Secondary inflammation may occur in the mobile ankle, leading to mechanical entrapment of the FHL tendon. This typically occurs as the FHL runs posterior to the talus, between the medial and lateral talar tubercles. In about 7% of the population an os trigonum lying just posterior to the lateral tubercle, which is the more prominent of the two tubercles, is present. In some individuals the lateral tubercle is long, in which case it is called a Stieda’s process. The os trigonum or Stieda’s process can be excised with a posterior ankle arthroscopy (Figure 12.7), and provides 80% good or excellent results at two to five years’ follow-up11.
Figure 12.7 The space posterior to the ankle is cleared of fat, staying lateral to the FHL. An os trigonum (OT) and the subtalar joint (STJ) are also shown.
Joint Surface Pathology
Joint surface lesions include chondral lesions, osteochondral lesions, cysts, and arthritis. All of these lesions produce persistent deep-seated pain, catching, locking, and instability, with swelling from the associated synovitis. Following ankle injury these deep symptoms are differentiated from soft tissue pain or impingement, which tend to cause anterior joint line pain.
Even if the MRI does not show an articular surface lesion, arthroscopy may well reveal joint laxity, ligament damage, synovitis, fibrosis, a meniscoid lesion, chondral damage12, and loose bodies. Tibial and talar osteophytes may be identified and treated.
The Berndt and Hardy radiological classification of osteochondral lesions of the talar dome has been updated to an MRI classification, as only about 50% of osteochondral defects are visible on plain radiographs. The MRI classification is13:
Stage I: Articular cartilage injury only
Stage IIA: Cartilage injury with bony fracture and edema
Stage IIB: Stage IIA without bony edema
Stage III: Detached but undisplaced bony fragment
Stage IV: Detached and displaced fragment
Stage V: Subchondral cyst formation
Lesions of the lateral talar dome are said to be superficial with chondral flaps (Figure 12.8a). Posteromedial lesions are said to be typically deeper and associated with osteochondral cysts. There is a range of treatments including microfracture, osteochondral grafting, chondrocyte implantation, and even the implantation of particulated juvenile articular cartilage. Microfracture, with the creation of holes in the subchondral plate 3 to 4 mm apart (Figure 12.8b) to stimulate the bone marrow to produce fibrocartilaginous cover, has been reported as giving good results in 80 to 85% of lesions that are less than 15 mm in diameter. However, poorer outcomes, with less than 50% good results, are seen in cystic lesions14, and lesions larger than 15 mm15. There is evidence that bone grafting can produce comparable results to microfracture. Early weight bearing following microfracture gives equal results to non-weightbearing16.
(a) A large talar dome flap will always have exposed bone underneath it.
(b) A medial lesion, which has been debrided and microfractured.
Success has been reported with repeat arthroscopic surgery17–18, when the first arthroscopic operation fails. Nevertheless, in treating larger cystic lesions and those cases where microfracture has failed, a variety of techniques can be used. Cylindrical osteochondral autografting, or mosaicplasty, has been reported as having 87% excellent or good results19, although concerns remain about the knee, from which the graft is often harvested. Osteochondral allografts have also been reported to give satisfactory results.
An alternative is autologous chondrocyte implantation (ACI), which can be embedded within a matrix (MACI). This is a two-stage procedure. In the first stage, the chondrocytes are harvested. They are then cultured. The cultured chondrocytes are then reintroduced, either embedded in a matrix (MACI), or not (ACI). The results of these techniques appear comparable. A meta-analysis of ACI in the talus showed an overall clinical success rate of 89.9%20.
Isolated lesions of the distal tibia are much rarer than talar lesions; nevertheless, the success rate of arthroscopic treatment appears to be similar to that for talar dome lesions21.
Ankle arthroscopy can be used in two ways for the treatment of ankle arthritis: firstly, to debride the joint; and, secondly, to fuse the joint. The value of arthroscopic debridement of the arthritic ankle is open to debate. Although the removal of flaps and loose bodies can be of assistance with mechanical symptoms, it should be noted that 90% of patients without joint space narrowing have good or excellent results after excision of the anterior tibial osteophyte, whereas only 50% of patients with joint space narrowing on preoperative weightbearing radiographs had good or excellent results. Furthermore pain relief at two years after surgery was significantly improved in the pure anterior impingement group, but not the group with joint space narrowing9. Care should also be taken in those cases where the joint is clearly starting to sublux in the sagittal plane. In those patients with end-stage arthritis the role of arthroscopic surgery lies with arthroscopic ankle arthrodesis.