Management of chronic ankle instability (CAI)

Management of chronic ankle instability (CAI)

Amit Chauhan and Rajiv Limaye discuss the different treatment options for chronic ankle instability, a common athletic injury.

Introduction

Ankle sprain injury is the most common injury sustained during sporting activities. It accounts for up to 40 per cent of all athletic injuries and is most commonly seen in athletes participating in basketball, football, running and ballet/dance [1,2]. In non-athletic population, many studies showed that two to seven individuals are affected per 1,000 in the general population each year [3].

Three-quarters of ankle injuries involve the lateral ligamentous complex, with an equal incidence between males and females [4]. Most ankle sprains do not develop lateral ligamentous instability and those that do are thought to be due to a loss of mechanoreceptors. Eighty per cent of acute ankle sprains make a full recovery with conservative management, while 20 per cent of acute ankle sprains develop mechanical or functional instability resulting in chronic ankle instability [2,5]. Chronic ankle instability can lead to early degenerative changes in the ankle due to unbalanced loading on the medial side of the ankle [6].

 

Anatomy

The ankle joint is a complex anatomic structure in which stability and mobility depends on correct ligamentous balancing, bony support, syndesmosis and tendons crossing it. The lateral ankle ligamentous complex comprises the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL) and the posterior talofibular ligament (PTFL). The ATFL runs from the anterior edge of the lateral malleolus to the talar neck, attaching just anterior to the lateral malleolar facet. It is the most important lateral stabilizer of the ankle, being the primary restraint to supination and anterior translation; it also limits plantar flexion and internal rotation. The PTFL courses from the posterior talus to the back of the lateral malleolus. It is located deep and is the strongest of the lateral ligament complex. The calcaneofibular ligament (CFL) lies deep to the peroneal tendon sheath, originating from the tip of the fibula to the lateral tubercle of the calcaneum [7,8].

 

Aetiology

The main predisposing factor for the development of chronic ankle instability (CAI) is the history of at least one previous lateral ankle sprain [4]. Almost as many as 55 per cent of patients who sustain an ankle sprain do not seek any evaluation or treatment from a healthcare professional [9]. This avoidance of treatment after an ankle sprain leads to residual symptoms such as chronic ankle instability. In addition to this, the level of activity also plays an important factor affecting daily routine activities of an individual with CAI.

Lower limb varus malalignment has been described as an important factor predisposing to ankle sprain and CAI. Anatomical variations of the tibio-talar joint such as axis of rotation, talar dome radius or retro-position of the lateral malleolus can predispose to ankle sprain and CAI [10]. Pathological conditions of the tibio-talar joint such as limitation of dorsiflexion (anterior impingement, short gastrocnemius), chondral problems (ankle osteochondral defects, loose bodies) or bimalleolar diastasis can provoke or increase CAI. Subtalar joint anatomical variations (axis of rotation, hindfoot varus) or pathologies (such as talocalcaneal coalition, subtalar joint laxity due to injuries of the cervical ligament, the talocalcaneal ligament or the interosseous ligament) act as risk factors of CAI [11–13].

Anatomical and histological variations of the collateral lateral ligament (insertion zones, number of bands, collagen diseases) are also important intrinsic risk factors for CAI [14]. Peroneal tendons pathologies can provoke or increase a CAI and pathologies with a proprioceptive deficit or imbalance in neuromuscular control are a frequent cause of CAI [11,15,16].

 

Classification

Severity of the injury to lateral ligaments can be classified according to anatomic injury or by degree of ligamentous injury. The anatomic classification includes Grades I through III, with Grade I being ATFL sprain; Grade II as ATFL and CFL sprain and Grade III with ATFL, CFL, and PTFL sprains.

The American Medical Association uses a generalised scale based on the degree of acute ligamentous injury:

Grade I – Ligament stretched

Grade II – Ligament partially torn

Grade III – Ligament completely torn

When chronic ankle instability is present, it can also be divided into functional and mechanical instability. Mechanical instability is characterised by an abnormal ankle mobility, assessed clinically using manual stress application by the anterior drawer and the talar tilt tests [17,18]. Functional instability was first described by Freeman et al as a subjective feeling of the ankle giving way during either physical activity or during common activities of daily living [19]. Mechanical instability is due to the laxity caused by ligaments tears. Functional instability is due to proprioceptive and muscular deficits after ankle sprain. Both mechanical and functional instabilities may be difficult to assess or distinguish and they most often occur as a combination in the development of CAI [20,21].

 

Clinical presentation

Clinically, the history of patients with chronic ankle instability reveals past recurrent ankle sprains and severe inversion injury. They take special precautions against weight bearing, strenuous activities and walking on rugged surfaces; wearing braces would just provide partial relief. Persistent history of “giving away” sensation along with positive physical examination findings clinches the diagnosis.

On physical examination, patients can localise the lateral ankle tenderness in the acute setting but the pain and swelling becomes more diffuse over the next few days. Careful palpation can confirm the structures involved in the injury – localised ATFL tenderness is exhibited at four to seven days post injury, while CFL injury can be diagnosed with tenderness at the calcaneal insertion. Lower leg and hindfoot alignment must be assessed, while standing and gait should be evaluated. Precise location of tenderness must be identified. Active and passive ankle range of motion (ROM) is measured with the knee extended and then on a sitting position with the legs down and the knees flexed to 90 degrees in order to assess gastrocnemius tightness. Hindfoot inversion/eversion is compared to the other side. In view of the difficulty in making precise measurements of hindfoot mobility, grading as normal, abnormal (increased or decreased) or no mobility is appropriate. An assessment of generalised joint laxity is important (modified Beighton scoring scale). Strength and pain on resisted function of peroneal and tibialis posterior tendons are specifically tested and neurovascular status of the lower legs is then assessed. Ankle ligament testing is comparative and performed on a relaxed patient in a sitting position with the knee flexed. There are two provocative tests that can assess ankle instability – the anterior drawer test and the talar tilt test.

The anterior drawer test assesses the integrity of the ATFL as the ATFL prevents anterior translation of the talus with respect to the tibia. The test is performed after positioning the ankle in neutral to 10° of plantar flexion with the patient seated and the knee flexed (see Figure 2). The examiner holds the calcaneus in one hand while stabilising the distal tibia in the other, and the calcaneus is translated forward. Increased translation of 3mm compared to the uninjured side or an absolute value of 10mm of displacement correlates to ATFL incompetence [22].

Figure 1 – Coronal T2 MRI Image showing fluid levels around lateral ligaments

Figure 1 – Coronal T2 MRI Image showing fluid levels around lateral ligaments

Figure 2 – AP and lateral radiographs showing lateral ligament reconstruction using anchors and Tightrope for syndesmosis reconstruction

Figure 2 – AP and lateral radiographs showing lateral ligament reconstruction using anchors and Tightrope for syndesmosis reconstruction

The talar tilt test is described as the angle formed by the talar dome and the tibial plafond during forced hindfoot inversion with the tibiotalar joint held in neutral. The test is not a useful physical examination tool as it is hard to distinguish ankle motion from subtalar motion, but it can be as useful as a stress radiograph. The normal range of talar tilt is variable and can range from five to 23°. However, 10° of absolute talar tilt or 5° difference compared to the contralateral side is generally considered a positive talar tilt test [23]. Stability and proprioceptive control of the ankle can be assessed by the patient standing with a single leg stance (eyes open and then eyes closed). This test may be helpful to differentiate mechanical from functional instability [24].

Chronic ankle instability is often associated with lesions that evolve from contributory factors. They do not necessarily occur with chronic ankle instability, and if any, not all these lesions occur together. Associated lesions that may accompany chronic ankle instability are sinus tarsi syndrome, tendon disorders such as peroneal tendinopathy, dislocation or subluxation, impingement syndromes, fractures such as anterior calcaneal process, fibula and lateral talar process, loose bodies, and osteochondral lesion of talar dome or distal tibia [25].

 

Radiographic assessment

The standard plain radiographs include: standing antero-posterior, lateral and mortise views. Comparative stress radiographic views with anterior drawer test and varus tilt may be performed, although it should be recognised that these have a high rate of false negative results [26]. Magnetic resonance imaging may be helpful in the presence of deep pain to assess for osteochondral lesions and tendon injuries and it will also confirm the presence of chronic ligamentous injury. All of our patients diagnosed provisionally as CAI undergo MRI for confirmation and to rule out any other associated pathology. Ultrasonography may be particularly helpful in the assessment of tendon pathology. Computer tomography/MRI arthrogram scanning is not routinely advised but may be helpful for accurate assessment of chondral lesion.

 

Management planning

There are two options for management of CAI after confirmation. Invariably, every patient undergoes non-operative treatment in the form of physical therapy. Sometimes adequate rehabilitation with a focus to correct proprioceptive, strength and motion deficits can provide sufficient reduction in symptoms to avoid surgical intervention. While the ankle is painful, an ankle support is helpful. Ankle and foot orthoses can also help prevent recurrence, including an ankle-foot orthosis (“orthotic”), stiff-soled shoes or lateral heel wedges. This rehabilitation has a high probability of success in functional ankle instability; however, the likelihood of success is decreased with mechanical instability, peroneal weakness or proprioceptive deficits.

Indication for surgical treatment is represented by associated symptomatic mechanical and functional chronic ankle instability unresponsive to a six-month rehabilitation program. Isolated mechanical instability without episodes of giving way is not in itself an indication of surgery; hence the surgical treatment is valued when patients are not willing to accept the recurrence of spraining episodes or subjective feelings of giving way. Contraindications include pain without instability, medically unfit patients, peripheral vascular disease, peripheral neuropathy and inability to comply with a postoperative regimen.

More than 80 surgical procedures have been described for chronic lateral ankle instability, and the procedures can be divided into three categories: anatomic repair, non-anatomic (or check-rein) reconstruction and anatomic reconstruction.

Anatomic Repair – Brostrom first described a mid-substance repair of the ATFL and CFL in 1966 after reporting on a series of 60 patients [27]. Gould and co-workers further modified the Brostrom procedure by reinforcing the repair using the lateral talocalcaneal ligament, CFL, and inferior extensor retinaculum, which helped limit inversion and corrected subtalar instability [28]. Karlsson and associates were the first to report on imbricating the damaged ligaments and reinserting the ligaments through drill holes in the fibula [29]. They noted improved results using this bone tunnel repair of the ATFL
and CFL.

Numerous non-anatomic reconstruction methods have been described over the years, since the original Elmslie procedure was first described in 1934 using fascia lata as a means to reconstruct the lateral ankle ligaments [30]. Watson-Jones popularised a procedure first reported in 1952 that used the peroneus brevis and rerouted the tendon in a posterior to anterior fashion through the fibula and securing it onto the talar neck [31]. In 1953, Evans reported a simplified version of the Watson-Jones procedure by routing the peroneus brevis tendon obliquely through the distal fibula in an anterior-distal to posterior-proximal fashion [32]. The Chrisman-Snook reconstruction, which was a variation on the original Elmslie procedure, was subsequently reported. The peroneus brevis tendon is split and transferred through the fibula and into the calcaneus, thus providing a more anatomic reconstruction [33].

Anatomic tenodesis reconstructions are able to augment the anatomic repair without sacrificing lateral ankle anatomy or kinematics. Colville described a reconstruction using a split peroneus brevis tendon to augment a repaired ATFL and CFL. The peroneus brevis is placed into the anatomic origins and insertions of the ligaments. As a result, normal ankle kinematics and subtalar motion are maintained [34]. Anatomic reconstruction can be achieved using free autograft or allograft tendon. The indications for this technique include poor tissue quality or revision surgery. The advantages for using free autograft or allograft are that a strong anatomic repair can be provided without sacrificing peroneal function or strength. The graft can be used to augment the anatomic repair and is placed into the anatomic origins and insertions of the ATFL and CFL. There are various sources of autograft that can be obtained from the patient including gracilis, semitendinosis, fascia lata, palmaris, plantaris and patella tendons. The use of allograft may be preferable in certain circumstances, as there is no donor-site morbidity, but the patient should be counselled regarding the inherent risks with allograft tissue [35].

Our experience

In our practice, we routinely perform ankle arthroscopy to confirm our findings and rule out any other associated pathology. After ankle arthroscopy, we continue with Modified Bostrom-Gould procedure and syndesmosis reconstruction using Tightrope (Arthrex), if required. We routinely use the twinfix anchors for the reconstruction of the torn ATFL and CFL and assess the stability of syndesmosis on arthroscopy. If there is any doubt of tear within it, we would fix this using Tightrope. The image intensifier is used in theatre and the images are saved. Post-operatively, a below knee back slab is applied. At two weeks, after the suture removal, this is changed to a below knee light-weight full cast. The patient is kept non-weight bearing for the first six weeks following the surgery and later gradually mobilised with an aircast boot. The physiotherapy program is essential leading up to a gradual return to sports and normal day-to-day activities. The usual return to competitive or contact sports are after three to six months depending on the pathology, strength of repair and associated injuries.

Conclusion

Ankle sprains are the most common injury that occur during athletic events, with the lateral ligamentous complex most frequently injured. Approximately 20 per cent of acute ankle sprains develop functional or mechanical instability resulting in chronic ankle instability. Thorough history identifying mechanical versus functional instability along with physical examination findings helps in provisional diagnosis. Weight-bearing radiographs and MRI is essential to exclude other associated pathologies. Over the years, an improved understanding of the biomechanics and path anatomy has expanded our treatment options for lateral ankle instability. A robust functional rehabilitation programme remains the mainstay to avoid CAI after an ankle sprain. Once diagnosed, patients with CAI should be undertaking physiotherapy along with orthotic support. Failed rehabilitation is an indication for surgical intervention. The anatomical repairs are still the best methods of treatment in symptomatic chronic instability and with the possibility of intra-articular pathology, it is recommended that an arthroscopy is performed at the time of surgery to confirm diagnosis and address these pathologies.

Our experience with anatomic repair using the Modified Bostrom-Gould procedure following ankle arthroscopy has shown excellent results in correctly indicated patients. We have performed this procedure even in failed cases and have achieved good results.

 

 

Authors

Mr Amit Chauhan MRCS Foot and Ankle Fellow

Mr Rajiv Limaye FRCS Orth Consulant Orthopaedic Surgeon

University Hospital of North Tees and Hartlepool, UK

 

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