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Ankle instability: presentation and management
FOOT AND ANKLE
Ankle instability: presentation and management
ankle. Freeman introduced the term “functional instability” for a group of patients who complain of giving way but do not have abnormal mobility of the ankle. It is thought that functional instability occurs due to proprioceptive or neuromuscular deficits, or because of poor postural control. Proprioceptive deficits can arise as a consequence of damage to proprioceptive fibres in the joint capsule and ankle ligaments. Neuromuscular deficits can arise due to damage to the peroneal muscles. These types of functional deficits result in impaired neuromuscular recruitment, and affected patients are likely to benefit from an appropriate physiotherapy regimen. Patients who demonstrate abnormal ankle joint mobility on clinical examination or under stress radiography are said to have “mechanical instability”. Although conceptually it is nice to be able to classify patients with CAI into two different classes the reality is that the complete spectrum of CAI often includes an overlap in presentation3 (Figure 1).
M Hossain R Thomas
Abstract The ankle joint is akin to a mortise. Damage to this mortise joint with injury to either the medial, lateral or syndesmotic complex can result in chronic ankle instability. In this article we discuss the management of ankle instability, most commonly arising from injuries to the lateral ligament complex. Chronic ankle instability may develop from an inversiontype ankle sprain, usually affecting the anterior talo-fibular ligament (ATFL). Most affected patients improve with conservative management following this injury, but up to 30% of patients can develop debilitating chronic ankle symptoms. In assessing ankle instability it is important to differentiate between patients with functional instability and those with mechanical instability. Clinical assessment is the cornerstone of diagnosis, although stress views performed under anaesthesia (including the contralateral ankle for comparison) are useful. MRI is helpful in the assessment of soft tissue and cartilage injury. Short periods of immobilisation and physiotherapy are the mainstay of acute treatment. Patients with functional instability may benefit from peroneal strengthening and proprioceptive rehabilitation. Surgery is recommended for patients with mechanical instability who fail conservative treatment. Anatomical ligament repair has the best results. Non-anatomic ligament reconstruction is reserved for revision cases although primary ligament reconstruction may have a role in selected cases.
Relevant anatomy (Figure 2) Lateral collateral ligament complex This ligament complex comprises the Anterior talo-fibular ligament (ATFL), posterior talo-fibular ligament (PTFL) and the calcaneofibular ligament (CFL). ATFL: the ATFL is essentially a discrete thickening of the ankle joint capsule. It is a flat quadrilateral structure that originates from the antero-inferior margin of lateral malleolus and runs antero-medially to be inserted on to the talar body just anterior to the lateral malleolar articular surface and is about 0.5e1 cm wide. Although the ligament is depicted as a single band in most illustrations, Sarrafian described the ATFL as having two distinct bands, later corroborated by Golano P et al.4 It is the weakest of the three ligaments but can undergo great deformation before failure.
Keywords ankle instability; anterior talo-fibular ligament; Brostrom repair; functional instability; mechanical instability
PTFL: the PTFL originates from the malleolar fossa on the medial surface of the lateral malleolus and travels horizontally to be inserted on to the postero-lateral talus, coming under tension in dorsiflexion. It is very strong and is rarely injured.
Introduction Ankle sprains are among the most common sporting injuries. It is estimated that around 5000 ankle sprains occur every day in the UK.1 Although most of these patients get better with conservative treatment, a significant number continue to have long term problems with pain, swelling and chronic ankle instability.2 It is important to appreciate, when a patient presents with complaints of the ankle giving way, that he or she may have anatomical abnormalities that predispose to chronic ankle instability (CAI). It is also useful to emphasise that not all patients who complain of ankle instability have objective signs of an unstable
M Hossain PG Cert MSc (Orth Eng) MSc (Oxon) FRCSGlasg (Tr and Orth) Senior Foot and Ankle Fellow, Cardiff Regional foot and ankle unit, University Hospital of Llandough, Llandough, UK. Conflicts of interest: none declared. R Thomas BSc (Hons) FRCS (Tr and Orth) FFSEM(UK) Consultant Orthopaedic Surgeon, Cardiff Regional foot and ankle unit, University Hospital of Llandough, Llandough, UK. Conflicts of interest: none declared.
ORTHOPAEDICS AND TRAUMA --:-
Figure 1 Interplay of factors in chronic ankle instability.
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against anterior translation, varus tilt and internal rotation of the talus. CFL The CFL is angulated posteriorly in the neutral position of the ankle but becomes more vertical in ankle dorsiflexion and in this position acts as a true collateral ligament. It spans both the ankle and the subtalar joints. The CFL resists ankle inversion with the ankle in neutral to dorsiflexion and is an important stabiliser of the subtalar joint. It is relaxed in a valgus ankle and stressed in a varus position. It is therefore apparent that throughout the arc of ankle motion either the ATFL or the CFL acts as a true collateral ligament of the ankle (ATFL in plantarflexion and CFL in dorsiflexion). There is a window in this range of movement where neither of the two ligaments is able to support the ankle. The mean normal angle between the two ligaments is 105 (range 70 e140 ). If the angle between the two ligaments is increased then the window of instability also enlarges. Individuals with such an anatomical variation may be more prone to develop ankle instability.
Figure 2 Anatomy of the ankle: lateral ligaments and the anterior inferior tibio-fibular ligament.
CFL: the CFL is a distinct structure. It is not a capsular thickening but is extra-capsular. It is in close proximity to the peroneal tendons. During surgical exploration these tendons act as a landmark for the CFL. It is found immediately deep to, and runs at right angles to, the peroneal tendons. The CFL originates from the tip of the fibula and runs downwards and backwards to attach to a tubercle situated on the postero-lateral surface of calcaneus. It’s footprint on the calcaneus is around 3 cm posterior and superior to the peroneal tubercle. There is some variation in its proximal attachment. Instead of attaching proximally to the tip of the fibula, the CFL can be attached to the ATFL or have attachments to both fibula and ATFL.
Practice point 1 C C C
C
C
Anatomic factors predisposing to ankle instability
Syndesmosis complex The ankle syndesmosis is formed between the distal tibia and fibula. The stability of this complex is maintained by the anterior tibio-fibular ligament, posterior tibio-fibular ligament and interosseous tibio-fibular ligament. Stability of the syndesmosis is also provided by the inferior margin of the interosseous membrane. The anterior tibio-fibular ligament is directed inferior and laterally from the anterior tubercle of the distal tibia to the anterior margin of the lateral malleolus. The lower fascicle of the anterior tibio-fibular ligament (AITFL) is frequently damaged in ankle sprains and can consequently produce anterolateral ankle impingement. The pathologic lesion can be seen at ankle arthroscopy as a thick hyalinised “meniscoid” lesion.
Varus hindfoot A varus hindfoot predisposes to ankle instability. Inversion of the subtalar joint locks the transverse tarsal joint and reduces the ability of the ankle to dissipate stress. In a normal ankle, on heel strike, the centre of pressure of the foot lies lateral to the subtalar joint axis. This results in the Ground Reaction Force (GRF) producing pronation torque in a normal ankle. However, if the hindfoot is in varus this produces a supinating torque because of the medially placed centre of pressure. This torque stresses the ATFL. Tight tendo Achilles Tightness of the Achilles tendon limits ankle dorsiflexion and also results in the ATFL being stressed for a longer period of the gait cycle.
Biomechanics ATFL The ATFL is horizontal in the neutral position of the ankle. Therefore, as a restraint, it is ineffective in a neutral or dorsiflexed position. The ATFL becomes more vertical in ankle plantar flexion in line with the fibula and becomes a true collateral ligament in this position. The ligament is therefore stressed in the plantar flexed ankle and is most prone to injury in this position. Indeed, it is the main stabiliser of the ankle in plantar flexion
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ATFL stabilises the ankle in PF CFL stabilises the ankle in DF ATFL is the weakest of the lateral ligaments and is the most frequently injured Individuals who have widely spaced ATFL and CFL may be more prone to chronic ankle instability Varus hindfoot and tight tendo Achilles both predispose to ankle instability
Pathomechanics of ankle sprain It has been proposed that on landing from a height the ankle assumes the natural loose-packed position of inversion and plantar flexion.2 Therefore, synchronous firing of the evertors and dorsiflexors are necessary to stabilise the ankle. Ankle sprains occur when this mechanism is disrupted. It has also been
2
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FOOT AND ANKLE
observed that the dominant ankle is more prone to injury than the non-dominant side.
ankle dorsiflexion represents a positive impingement test. This could be due to a meniscoid lesion from injury to the AITFL as described above. Tenderness over the talar dome that is worse on palpation but not on dorsiflexion might be due to an osteochondral injury. Tenderness posterior to the fibula suggest peroneal tendon pathology. Peroneal tendons are frequently injured in ankle sprains. If the peroneal tendons are unstable there may be obvious prominence at the back of the fibula or this may be brought about by resisted eversion with the ankle.
Clinical features Patients may present with pain, swelling, giving way, activity limitation etc. It is important to elicit in the history how long ago the first acute event occurred, what treatment was offered, how frequently the ankle gives way and what are the precipitating factors. Pain at rest, between episodes of giving way, may suggest underlying chondral injury.
Move: the range of movement of the ankle should be ascertained and the strength of the peroneal muscles tested. Tests for generalised joint laxity (Beighton score) should also be performed to rule out systemic instability. Silfverskiold test e tightness in gastrocnemius muscles and tendo Achilles should be sought by assessing ankle range of motion with the knees extended and flexed. If ankle dorsiflexion is limited on knee extension but improved on knee flexion this suggests gastrocnemius tightness. Alternatively, if ankle dorsiflexion is limited on knee extension but not improved on knee flexion, this suggests that the tendo Achilles may be tight. Anterior draw test e this test (Figure 4) evaluates the ATFL. The patient needs to be relaxed, seated with the knee flexed and the ankle plantar flexed around 10e20 . One of the examiner’s hands stabilises the tibia and, with the other hand, the foot is pulled forwards. An alternative way to perform this test is to stabilise the heel on the bed with one hand and pull tibia forwards with the other hand. The test should be compared with the contralateral ankle. Although different grades of positivity are described, the inter- and intra-observer reliability are likely to be low. A recent consensus statement has therefore recommended that positive tests be described as stable, unstable or unstable with a sulcus sign.5 A sulcus sign is present when a
Clinical examination Look: examination commences with the patient standing with both knees exposed to allow lower limb assessment. As discussed earlier, subtle varus of the foot is a known risk factor for ankle instability (Figure 3). This requires a subjective assessment, as there is no evidence-based guideline regarding what constitutes the threshold for diagnosis of a “subtle varus ankle”. Normal hindfoot alignment is few degrees of valgus. Assessing gait also gives an opportunity to observe whether the peroneal tendons dislocate during gait. Some patients with complaints of ankle instability actually have peroneal instability that gives a perception of the ankle giving way. The site and size of any swelling is also noted. Swelling can be present over the lateral malleolus, lateral gutter, peroneal tendons or the ankle joint. If pain is present it is useful to ask patients if they can identify the site of pain with a single finger. Patients with chronic ankle instability frequently have concomitant injury and the site of pain they identify may be indicative of this. Muscular and proprioceptive control of the leg is assessed by asking the patient to stand on one leg at a time with eyes open and then with them closed. Patients who are unable to remain steady on their ankle with the eyes closed have a proprioceptive deficit. Feel: the site of tenderness is the key to differential diagnosis. A torn ATFL is tender just anterior and superior to the tip of fibula. Tenderness present more superiorly over the ankle joint would suggest a possible syndesmosis injury. Tenderness over the lateral gutter and lateral talar dome that is exacerbated with
Figure 3 Subtle hindfoot varus: this patient presented with a complaint of recurrent stumble on his right ankle.
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Figure 4 Anterior drawer test.
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External rotation stress test e this test is performed to assess for syndesmosis injury. The knee is flexed and the leg stabilized with one hand, while the other hand externally rotates the foot. A positive test reproduces pain over the syndesmosis. The external rotation stress test has a low sensitivity but high specificity to detect syndesmotic injury.7 This means that many injuries remain undetected by this test but there are few false positive cases.
dimple is seen in the lateral gutter on testing. It is not commonly seen in practice. An anterolateral draw test has also been described in the literature that is claimed to be more sensitive and specific in detecting ATFL injury but has not been clinically validated or widely adopted.6
Practice point 2 Practice point 3
Clinical examination check list: Look: Lower limb alignment: rule out subtle cavus Gait Site and size of swelling Peroneal instability Modified Romberg test Feel: Area of tenderness Move: ROM Resisted eversion Silfverskiold test Anterior draw test Talar tilt test Beighton score
Classification of ankle instability Anatomic injury
Clinical finding
Imaging finding
I
ATFL/CFL partial tear ATFL tear ATFL þ CFL
or þ drawer
Drawer, Talar tilt
þ drawer þ þ drawer
þDrawer, Talar tilt þDrawer, þTalar tilt
II III
Investigations Although clinical examination is quite sensitive to detect grade III injury it is less reliable in detecting less severe degrees of injury. Appropriate investigations are useful diagnostic tools and help to reinforce the clinical diagnosis.
Talar tilt test e this test (Figure 5) evaluates the CFL. With the ankle plantigrade the hindfoot is tilted one way then the other to assess for asymmetric movement. Palpation over the talar neck helps to differentiate movement of the ankle from the subtalar joint. It is often difficult to compare between sides. Tilting both heels simultaneously with the patient prone may allow better comparison between the two sides.
Radiology Weight bearing AP, mortise and lateral views of the ankle are standard images. Plain films may show syndesmotic injury, osteochondral fracture of the talus or avulsion fracture of fibula (Figure 6). An ossicle at the tip of the lateral malleolus is also
Figure 6 X-ray of ankle showing avulsion fracture of fibula suggestive of peroneal instability, this patient presented with a complaint of ankle instability.
Figure 5 Talar tilt test.
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Grade
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Figure 7 EUA: anterior draw.
frequently found in CAI. The hindfoot alignment view is also useful to assess hindfoot alignment although is not routinely performed.5
Figure 9 MRI showing injury to ATFL.
Stress views Stress views (Figures 7 and 8) allow objective assessment of displacement under load. These views should be performed with comparative views of the normal side. It is useful to understand that there is no consensus in the published literature, or good evidence, to indicate the true cut-off for a positive test. More than 4 mm anterior displacement is considered positive in the anterior draw test. Talar tilt is measured by drawing a line tangential to the articular surfaces of the distal tibia and talus. The talar tilt angle is formed by the convergence of these two lines. More than 6 difference between the two sides is considered positive and more than 15 difference indicative of injury to both the ATFL and the CFL.8
Ultrasound Ultrasound is useful in skilled hands, particularly to assess the peroneal tendons, but has been made redundant by the widespread availability of MRI scanning. MRI MRI (Figure 9) allows not only the assessment of the ATFL and CFL but also of local tendons and bones. The diagnostic accuracy of MRI has been widely investigated. The ATFL is best seen in axial cuts at a level where the fibula appears as a comma shaped structure. At this level the ATFL bridges the anterior margin of distal tibia and fibula. High signal or disruption is suggestive of injury.
Treatment Conservative All patients should have an initial trial of conservative treatment.5 Treatment following acute ankle injury consists of rest, elevation, ice packs and some form of ankle immobilisation for a short period. There is evidence that any type of immobilisation: such as taping, functional bracing, Aircast walker or short leg cast may be more helpful than no support.9 Therefore patient compliance and preference may be taken into account in choosing a form of immobilisation. Once the acute episode has resolved it is important to organize physiotherapy for appropriate rehabilitation. This consists of proprioception training, peroneal tendon strengthening, tendo Achilles stretching and balance training. Proprioceptive training is imparted with the wobble board and peroneal strengthening with Theraband exercises. Data is available for short term efficacy following neuromuscular rehab but long term follow up results are not known.10 Taping of the ankle reduces mechanical instability and has also been proposed as a prophylactic intervention, especially in athletes.11 Patients who fail to improve with conservative treatment may benefit from surgical intervention.
Figure 8 EUA: talar tilt.
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continuing instability.13 However, there may be a role for early ligament reconstruction in patients with a high BMI, heavy manual jobs, sportsmen or those with generalised ligament laxity who may overstress the repaired ligament and are therefore at high risk of failure of primary repair.5 Ligament reconstruction may affect ankle kinematics but in these situations stability is preferred over normal kinematics. Reconstruction is also indicated when there is insufficient native ligament left for adequate repair. It has also been suggested that ligament reconstruction rather than repair should be chosen if arthroscopic assessment reveals the ATFL to be highly irregular in appearance. The damaged ligament in this case is likely to be composed of scar tissue rather than type I collagen and as such may not be suitable for primary repair.5 Non-anatomic lateral ligament reconstruction has a long track record. A number of procedures have been described. WatsonJones described re-routing of the peroneus brevis (PB) tendon between the talus and the calcaneus. This was subsequently modified by Evans, who preferred re-routing via the distal fibula. Chrisman and Snook detached only a portion of PB, keeping its distal attachment intact. The main criticism of non-anatomic repairs is that these techniques restrict the movement of the subtalar joint and also sacrifice the PB tendon, which is an important lateral stabiliser of the ankle. Therefore some surgeons have attempted near anatomic repair using allografts.15 Many surgeons feel that in view of long term complications and availability of modern fixation techniques non-anatomic reconstruction using PB should now be avoided.5
Practice point 4 C
C C
C
C
Proprioceptive training and neuromuscular strengthening form the cornerstone of conservative management Anatomical repair has the best results from surgery Surgery should also address associated problems such as peroneal tendon tear/instability, osteochondral lesion, impingement lesion Non-anatomic repairs sacrifice peroneus brevis and also affect subtalar joint kinematics Near anatomic allograft repair and arthroscopic anatomic repair are new techniques that show promising results
Surgery Surgery has been reserved for patients with chronic ankle instability who fail conservative treatment. However, there have been reports of acute surgical repair with the supposed benefits of a reduced incidence of instability.12 It remains to be seen if early surgery is better than functional rehab over the long term. Arthroscopy: a number of studies have demonstrated that there is a high incidence of intra-articular pathology in patients with chronic ankle instability. Arthroscopy is therefore indicated when surgery is planned. The majority of surgeons would perform arthroscopy in the same sitting as ligament reconstruction. However, some choose to perform arthroscopy as an elective procedure prior to ligament reconstruction which follows at a later date.13 Arthroscopy serves both diagnostic and therapeutic purposes. It helps to assess chondral injury and to treat synovitis, impingement lesions and osteochondral lesions. Those who prefer a staged approach to surgery have claimed that treatment of soft tissue impingement and osteochondral lesions may avoid the need for further surgery in some patients. Patients with refractory functional instability may also benefit from arthroscopic debridement.
Additional surgery: it is important to stress that if concomitant pathologies are present they also need to be addressed for a successful surgical outcome. For example, a fixed varus hindfoot may need to be corrected with a calcaneal sliding osteotomy, whilst a tight tendo Achilles or gastrocnemius may benefit from appropriate release. If a fibular ossicle is found this also needs to be addressed. Fixation should be attempted for large ossicles but small fragments may be excised.5
Outcome measures Ligament repair: a number of repair techniques have been described. Anatomical repair gives the best results and is indicated in most patients.13 Anatomical repair of the existing ATFL and CFL to bone was described by Brostrom but the modification by Gould is currently most popular. Gould recommended reinforcement of the repair using inferior extensor retinaculum. The availability of suture anchors allows direct insertion of ligament ends onto the fibula rather than suturing together torn ligament ends. Interestingly, anatomical repair is not only simple, it also restores ankle kinematics to near normal compared to ligament reconstruction techniques. Lately there has been interest in arthroscopic lateral ligament repair. These techniques aim to replicate arthroscopic Brostrom-Gould repair.14 This is still an evolving field and although early results have been published long term results are still awaited.
There has been a generally welcomed trend in orthopaedic surgery to record patient specific outcome measures. Although there are some outcome measures in use in foot and ankle surgery there is currently no widely accepted and validated outcome measure for patients with chronic ankle instability.5 It is therefore difficult to compare results across studies and to pool outcomes for meta-analysis. The Foot and Ankle Outcome Score (FAOS) has been validated in patients with lateral ligament reconstruction. The Cumberland ankle instability tool (CAIT)16 has also been used.
Conclusion CAI represents a spectrum of pathologies in and around the ankle. Careful clinical assessment is required for successful management. Most patients can be managed with conservative treatment. A number of different surgical options are available for those who fail conservative treatment. It is expected that future trials will concentrate on developing validated patient reported outcome measures so that objective evidence-based treatment recommendations can be made. A
Ligament reconstruction: ligament reconstruction can be performed using a number of options: native autografts, allografts or synthetic implants. The majority of UK orthopaedic surgeons would perform a revision anatomical repair for failure of a primary anatomical repair and only attempt ligament reconstruction for
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Please cite this article in press as: Hossain M, Thomas R, Ankle instability: presentation and management, Orthopaedics and Trauma (2014), http://dx.doi.org/10.1016/j.mporth.2014.12.001
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REFERENCES 1 O’Loughlin PF, Murawski CD, Egan C, Kennedy JG. Ankle instability in sports. Phys Sportsmed 2009 Jun; 37: 93e103. 2 Yeung MS, Chan KM, So CH, Yuan W. An epidemiological survey on ankle sprain. Br J Sports Med 1994 Jun; 28: 112e6. 3 Hertel J. Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability. J Athl Train 2002 Dec; 37: 364e75. P, Vega J, de Leeuw PA, et al. Anatomy of the ankle ligaments: 4 Golano a pictorial essay. Knee Surg Sports Traumatol Arthrosc 2010 May; 18: 557e69. 5 Guillo S, Bauer T, Lee JW, et al. Consensus in chronic ankle instability: aetiology, assessment, surgical indications and place for arthroscopy. Orthop Traumatol Surg Res 2013 Dec; 99(suppl 8): S411e9. 6 Phisitkul P, Chaichankul C, Sripongsai R, Prasitdamrong I, Tengtrakulcharoen P, Suarchawaratana S. Accuracy of anterolateral drawer test in lateral ankle instability: a cadaveric study. Foot Ankle Int 2009 Jul; 30: 690e5. 7 de C esar PC, Avila EM, de Abreu MR. Comparison of magnetic resonance imaging to physical examination for syndesmotic injury after lateral ankle sprain. Foot Ankle Int 2011 Dec; 32: 1110e4. 8 Gaebler C, Kukla C, Breitenseher MJ, et al. Diagnosis of lateral ankle ligament injuries. Comparison between talar tilt, MRI and operative findings in 112 athletes. Acta Orthop Scand 1997 Jun; 68: 286e90.
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9 Lamb SE, Marsh JL, Hutton JL, Nakash R, Cooke MW, Collaborative Ankle Support Trial (CAST Group). Mechanical supports for acute, severe ankle sprain: a pragmatic, multicentre, randomised controlled trial. Lancet 2009 Feb 14; 373: 575e81. 10 de Vries JS, Krips R, Sierevelt IN, Blankevoort L, van Dijk CN. Interventions for treating chronic ankle instability. Cochrane Database Syst Rev 2011 Aug 10. Issue 8. Art. No.:CD004124. 11 Hubbard TJ, Cordova M. Effect of ankle taping on mechanical laxity in chronic ankle instability. Foot Ankle Int 2010 Jun; 31: 499e504. 12 Petersen W, Rembitzki IV, Koppenburg AG, et al. Treatment of acute ankle ligament injuries: a systematic review. Arch Orthop Trauma Surg 2013 Aug; 133: 1129e41. 13 Rogers M, Park D, Singh D, eds. Consensus of the 3rd round table. Barcelona: Ortho solutions Ltd., June 2013. 14 Nery C, Raduan F, Del Buono A, Asaumi ID, Cohen M, Maffulli N. €m-Gould for chronic ankle instability: a Arthroscopic-assisted Brostro long-term follow-up. Am J Sports Med 2011 Nov; 39: 2381e8. 15 Miller AG, Raikin SM, Ahmad J. Near-anatomic allograft tenodesis of chronic lateral ankle instability. Foot Ankle Int 2013 Nov; 34: 1501e7. 16 Donahue M, Simon J, Docherty CL. Critical review of self-reported functional ankle instability measures. Foot Ankle Int 2011 Dec; 32: 1140e6.
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Please cite this article in press as: Hossain M, Thomas R, Ankle instability: presentation and management, Orthopaedics and Trauma (2014), http://dx.doi.org/10.1016/j.mporth.2014.12.001
Ankle instability: presentation and management
ankle. Freeman introduced the term “functional instability” for a group of patients who complain of giving way but do not have abnormal mobility of the ankle. It is thought that functional instability occurs due to proprioceptive or neuromuscular deficits, or because of poor postural control. Proprioceptive deficits can arise as a consequence of damage to proprioceptive fibres in the joint capsule and ankle ligaments. Neuromuscular deficits can arise due to damage to the peroneal muscles. These types of functional deficits result in impaired neuromuscular recruitment, and affected patients are likely to benefit from an appropriate physiotherapy regimen. Patients who demonstrate abnormal ankle joint mobility on clinical examination or under stress radiography are said to have “mechanical instability”. Although conceptually it is nice to be able to classify patients with CAI into two different classes the reality is that the complete spectrum of CAI often includes an overlap in presentation3 (Figure 1).
M Hossain R Thomas
Abstract The ankle joint is akin to a mortise. Damage to this mortise joint with injury to either the medial, lateral or syndesmotic complex can result in chronic ankle instability. In this article we discuss the management of ankle instability, most commonly arising from injuries to the lateral ligament complex. Chronic ankle instability may develop from an inversiontype ankle sprain, usually affecting the anterior talo-fibular ligament (ATFL). Most affected patients improve with conservative management following this injury, but up to 30% of patients can develop debilitating chronic ankle symptoms. In assessing ankle instability it is important to differentiate between patients with functional instability and those with mechanical instability. Clinical assessment is the cornerstone of diagnosis, although stress views performed under anaesthesia (including the contralateral ankle for comparison) are useful. MRI is helpful in the assessment of soft tissue and cartilage injury. Short periods of immobilisation and physiotherapy are the mainstay of acute treatment. Patients with functional instability may benefit from peroneal strengthening and proprioceptive rehabilitation. Surgery is recommended for patients with mechanical instability who fail conservative treatment. Anatomical ligament repair has the best results. Non-anatomic ligament reconstruction is reserved for revision cases although primary ligament reconstruction may have a role in selected cases.
Relevant anatomy (Figure 2) Lateral collateral ligament complex This ligament complex comprises the Anterior talo-fibular ligament (ATFL), posterior talo-fibular ligament (PTFL) and the calcaneofibular ligament (CFL). ATFL: the ATFL is essentially a discrete thickening of the ankle joint capsule. It is a flat quadrilateral structure that originates from the antero-inferior margin of lateral malleolus and runs antero-medially to be inserted on to the talar body just anterior to the lateral malleolar articular surface and is about 0.5e1 cm wide. Although the ligament is depicted as a single band in most illustrations, Sarrafian described the ATFL as having two distinct bands, later corroborated by Golano P et al.4 It is the weakest of the three ligaments but can undergo great deformation before failure.
Keywords ankle instability; anterior talo-fibular ligament; Brostrom repair; functional instability; mechanical instability
PTFL: the PTFL originates from the malleolar fossa on the medial surface of the lateral malleolus and travels horizontally to be inserted on to the postero-lateral talus, coming under tension in dorsiflexion. It is very strong and is rarely injured.
Introduction Ankle sprains are among the most common sporting injuries. It is estimated that around 5000 ankle sprains occur every day in the UK.1 Although most of these patients get better with conservative treatment, a significant number continue to have long term problems with pain, swelling and chronic ankle instability.2 It is important to appreciate, when a patient presents with complaints of the ankle giving way, that he or she may have anatomical abnormalities that predispose to chronic ankle instability (CAI). It is also useful to emphasise that not all patients who complain of ankle instability have objective signs of an unstable
M Hossain PG Cert MSc (Orth Eng) MSc (Oxon) FRCSGlasg (Tr and Orth) Senior Foot and Ankle Fellow, Cardiff Regional foot and ankle unit, University Hospital of Llandough, Llandough, UK. Conflicts of interest: none declared. R Thomas BSc (Hons) FRCS (Tr and Orth) FFSEM(UK) Consultant Orthopaedic Surgeon, Cardiff Regional foot and ankle unit, University Hospital of Llandough, Llandough, UK. Conflicts of interest: none declared.
ORTHOPAEDICS AND TRAUMA --:-
Figure 1 Interplay of factors in chronic ankle instability.
1
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Please cite this article in press as: Hossain M, Thomas R, Ankle instability: presentation and management, Orthopaedics and Trauma (2014), http://dx.doi.org/10.1016/j.mporth.2014.12.001
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against anterior translation, varus tilt and internal rotation of the talus. CFL The CFL is angulated posteriorly in the neutral position of the ankle but becomes more vertical in ankle dorsiflexion and in this position acts as a true collateral ligament. It spans both the ankle and the subtalar joints. The CFL resists ankle inversion with the ankle in neutral to dorsiflexion and is an important stabiliser of the subtalar joint. It is relaxed in a valgus ankle and stressed in a varus position. It is therefore apparent that throughout the arc of ankle motion either the ATFL or the CFL acts as a true collateral ligament of the ankle (ATFL in plantarflexion and CFL in dorsiflexion). There is a window in this range of movement where neither of the two ligaments is able to support the ankle. The mean normal angle between the two ligaments is 105 (range 70 e140 ). If the angle between the two ligaments is increased then the window of instability also enlarges. Individuals with such an anatomical variation may be more prone to develop ankle instability.
Figure 2 Anatomy of the ankle: lateral ligaments and the anterior inferior tibio-fibular ligament.
CFL: the CFL is a distinct structure. It is not a capsular thickening but is extra-capsular. It is in close proximity to the peroneal tendons. During surgical exploration these tendons act as a landmark for the CFL. It is found immediately deep to, and runs at right angles to, the peroneal tendons. The CFL originates from the tip of the fibula and runs downwards and backwards to attach to a tubercle situated on the postero-lateral surface of calcaneus. It’s footprint on the calcaneus is around 3 cm posterior and superior to the peroneal tubercle. There is some variation in its proximal attachment. Instead of attaching proximally to the tip of the fibula, the CFL can be attached to the ATFL or have attachments to both fibula and ATFL.
Practice point 1 C C C
C
C
Anatomic factors predisposing to ankle instability
Syndesmosis complex The ankle syndesmosis is formed between the distal tibia and fibula. The stability of this complex is maintained by the anterior tibio-fibular ligament, posterior tibio-fibular ligament and interosseous tibio-fibular ligament. Stability of the syndesmosis is also provided by the inferior margin of the interosseous membrane. The anterior tibio-fibular ligament is directed inferior and laterally from the anterior tubercle of the distal tibia to the anterior margin of the lateral malleolus. The lower fascicle of the anterior tibio-fibular ligament (AITFL) is frequently damaged in ankle sprains and can consequently produce anterolateral ankle impingement. The pathologic lesion can be seen at ankle arthroscopy as a thick hyalinised “meniscoid” lesion.
Varus hindfoot A varus hindfoot predisposes to ankle instability. Inversion of the subtalar joint locks the transverse tarsal joint and reduces the ability of the ankle to dissipate stress. In a normal ankle, on heel strike, the centre of pressure of the foot lies lateral to the subtalar joint axis. This results in the Ground Reaction Force (GRF) producing pronation torque in a normal ankle. However, if the hindfoot is in varus this produces a supinating torque because of the medially placed centre of pressure. This torque stresses the ATFL. Tight tendo Achilles Tightness of the Achilles tendon limits ankle dorsiflexion and also results in the ATFL being stressed for a longer period of the gait cycle.
Biomechanics ATFL The ATFL is horizontal in the neutral position of the ankle. Therefore, as a restraint, it is ineffective in a neutral or dorsiflexed position. The ATFL becomes more vertical in ankle plantar flexion in line with the fibula and becomes a true collateral ligament in this position. The ligament is therefore stressed in the plantar flexed ankle and is most prone to injury in this position. Indeed, it is the main stabiliser of the ankle in plantar flexion
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ATFL stabilises the ankle in PF CFL stabilises the ankle in DF ATFL is the weakest of the lateral ligaments and is the most frequently injured Individuals who have widely spaced ATFL and CFL may be more prone to chronic ankle instability Varus hindfoot and tight tendo Achilles both predispose to ankle instability
Pathomechanics of ankle sprain It has been proposed that on landing from a height the ankle assumes the natural loose-packed position of inversion and plantar flexion.2 Therefore, synchronous firing of the evertors and dorsiflexors are necessary to stabilise the ankle. Ankle sprains occur when this mechanism is disrupted. It has also been
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observed that the dominant ankle is more prone to injury than the non-dominant side.
ankle dorsiflexion represents a positive impingement test. This could be due to a meniscoid lesion from injury to the AITFL as described above. Tenderness over the talar dome that is worse on palpation but not on dorsiflexion might be due to an osteochondral injury. Tenderness posterior to the fibula suggest peroneal tendon pathology. Peroneal tendons are frequently injured in ankle sprains. If the peroneal tendons are unstable there may be obvious prominence at the back of the fibula or this may be brought about by resisted eversion with the ankle.
Clinical features Patients may present with pain, swelling, giving way, activity limitation etc. It is important to elicit in the history how long ago the first acute event occurred, what treatment was offered, how frequently the ankle gives way and what are the precipitating factors. Pain at rest, between episodes of giving way, may suggest underlying chondral injury.
Move: the range of movement of the ankle should be ascertained and the strength of the peroneal muscles tested. Tests for generalised joint laxity (Beighton score) should also be performed to rule out systemic instability. Silfverskiold test e tightness in gastrocnemius muscles and tendo Achilles should be sought by assessing ankle range of motion with the knees extended and flexed. If ankle dorsiflexion is limited on knee extension but improved on knee flexion this suggests gastrocnemius tightness. Alternatively, if ankle dorsiflexion is limited on knee extension but not improved on knee flexion, this suggests that the tendo Achilles may be tight. Anterior draw test e this test (Figure 4) evaluates the ATFL. The patient needs to be relaxed, seated with the knee flexed and the ankle plantar flexed around 10e20 . One of the examiner’s hands stabilises the tibia and, with the other hand, the foot is pulled forwards. An alternative way to perform this test is to stabilise the heel on the bed with one hand and pull tibia forwards with the other hand. The test should be compared with the contralateral ankle. Although different grades of positivity are described, the inter- and intra-observer reliability are likely to be low. A recent consensus statement has therefore recommended that positive tests be described as stable, unstable or unstable with a sulcus sign.5 A sulcus sign is present when a
Clinical examination Look: examination commences with the patient standing with both knees exposed to allow lower limb assessment. As discussed earlier, subtle varus of the foot is a known risk factor for ankle instability (Figure 3). This requires a subjective assessment, as there is no evidence-based guideline regarding what constitutes the threshold for diagnosis of a “subtle varus ankle”. Normal hindfoot alignment is few degrees of valgus. Assessing gait also gives an opportunity to observe whether the peroneal tendons dislocate during gait. Some patients with complaints of ankle instability actually have peroneal instability that gives a perception of the ankle giving way. The site and size of any swelling is also noted. Swelling can be present over the lateral malleolus, lateral gutter, peroneal tendons or the ankle joint. If pain is present it is useful to ask patients if they can identify the site of pain with a single finger. Patients with chronic ankle instability frequently have concomitant injury and the site of pain they identify may be indicative of this. Muscular and proprioceptive control of the leg is assessed by asking the patient to stand on one leg at a time with eyes open and then with them closed. Patients who are unable to remain steady on their ankle with the eyes closed have a proprioceptive deficit. Feel: the site of tenderness is the key to differential diagnosis. A torn ATFL is tender just anterior and superior to the tip of fibula. Tenderness present more superiorly over the ankle joint would suggest a possible syndesmosis injury. Tenderness over the lateral gutter and lateral talar dome that is exacerbated with
Figure 3 Subtle hindfoot varus: this patient presented with a complaint of recurrent stumble on his right ankle.
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Figure 4 Anterior drawer test.
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External rotation stress test e this test is performed to assess for syndesmosis injury. The knee is flexed and the leg stabilized with one hand, while the other hand externally rotates the foot. A positive test reproduces pain over the syndesmosis. The external rotation stress test has a low sensitivity but high specificity to detect syndesmotic injury.7 This means that many injuries remain undetected by this test but there are few false positive cases.
dimple is seen in the lateral gutter on testing. It is not commonly seen in practice. An anterolateral draw test has also been described in the literature that is claimed to be more sensitive and specific in detecting ATFL injury but has not been clinically validated or widely adopted.6
Practice point 2 Practice point 3
Clinical examination check list: Look: Lower limb alignment: rule out subtle cavus Gait Site and size of swelling Peroneal instability Modified Romberg test Feel: Area of tenderness Move: ROM Resisted eversion Silfverskiold test Anterior draw test Talar tilt test Beighton score
Classification of ankle instability Anatomic injury
Clinical finding
Imaging finding
I
ATFL/CFL partial tear ATFL tear ATFL þ CFL
or þ drawer
Drawer, Talar tilt
þ drawer þ þ drawer
þDrawer, Talar tilt þDrawer, þTalar tilt
II III
Investigations Although clinical examination is quite sensitive to detect grade III injury it is less reliable in detecting less severe degrees of injury. Appropriate investigations are useful diagnostic tools and help to reinforce the clinical diagnosis.
Talar tilt test e this test (Figure 5) evaluates the CFL. With the ankle plantigrade the hindfoot is tilted one way then the other to assess for asymmetric movement. Palpation over the talar neck helps to differentiate movement of the ankle from the subtalar joint. It is often difficult to compare between sides. Tilting both heels simultaneously with the patient prone may allow better comparison between the two sides.
Radiology Weight bearing AP, mortise and lateral views of the ankle are standard images. Plain films may show syndesmotic injury, osteochondral fracture of the talus or avulsion fracture of fibula (Figure 6). An ossicle at the tip of the lateral malleolus is also
Figure 6 X-ray of ankle showing avulsion fracture of fibula suggestive of peroneal instability, this patient presented with a complaint of ankle instability.
Figure 5 Talar tilt test.
ORTHOPAEDICS AND TRAUMA --:-
Grade
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Figure 7 EUA: anterior draw.
frequently found in CAI. The hindfoot alignment view is also useful to assess hindfoot alignment although is not routinely performed.5
Figure 9 MRI showing injury to ATFL.
Stress views Stress views (Figures 7 and 8) allow objective assessment of displacement under load. These views should be performed with comparative views of the normal side. It is useful to understand that there is no consensus in the published literature, or good evidence, to indicate the true cut-off for a positive test. More than 4 mm anterior displacement is considered positive in the anterior draw test. Talar tilt is measured by drawing a line tangential to the articular surfaces of the distal tibia and talus. The talar tilt angle is formed by the convergence of these two lines. More than 6 difference between the two sides is considered positive and more than 15 difference indicative of injury to both the ATFL and the CFL.8
Ultrasound Ultrasound is useful in skilled hands, particularly to assess the peroneal tendons, but has been made redundant by the widespread availability of MRI scanning. MRI MRI (Figure 9) allows not only the assessment of the ATFL and CFL but also of local tendons and bones. The diagnostic accuracy of MRI has been widely investigated. The ATFL is best seen in axial cuts at a level where the fibula appears as a comma shaped structure. At this level the ATFL bridges the anterior margin of distal tibia and fibula. High signal or disruption is suggestive of injury.
Treatment Conservative All patients should have an initial trial of conservative treatment.5 Treatment following acute ankle injury consists of rest, elevation, ice packs and some form of ankle immobilisation for a short period. There is evidence that any type of immobilisation: such as taping, functional bracing, Aircast walker or short leg cast may be more helpful than no support.9 Therefore patient compliance and preference may be taken into account in choosing a form of immobilisation. Once the acute episode has resolved it is important to organize physiotherapy for appropriate rehabilitation. This consists of proprioception training, peroneal tendon strengthening, tendo Achilles stretching and balance training. Proprioceptive training is imparted with the wobble board and peroneal strengthening with Theraband exercises. Data is available for short term efficacy following neuromuscular rehab but long term follow up results are not known.10 Taping of the ankle reduces mechanical instability and has also been proposed as a prophylactic intervention, especially in athletes.11 Patients who fail to improve with conservative treatment may benefit from surgical intervention.
Figure 8 EUA: talar tilt.
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continuing instability.13 However, there may be a role for early ligament reconstruction in patients with a high BMI, heavy manual jobs, sportsmen or those with generalised ligament laxity who may overstress the repaired ligament and are therefore at high risk of failure of primary repair.5 Ligament reconstruction may affect ankle kinematics but in these situations stability is preferred over normal kinematics. Reconstruction is also indicated when there is insufficient native ligament left for adequate repair. It has also been suggested that ligament reconstruction rather than repair should be chosen if arthroscopic assessment reveals the ATFL to be highly irregular in appearance. The damaged ligament in this case is likely to be composed of scar tissue rather than type I collagen and as such may not be suitable for primary repair.5 Non-anatomic lateral ligament reconstruction has a long track record. A number of procedures have been described. WatsonJones described re-routing of the peroneus brevis (PB) tendon between the talus and the calcaneus. This was subsequently modified by Evans, who preferred re-routing via the distal fibula. Chrisman and Snook detached only a portion of PB, keeping its distal attachment intact. The main criticism of non-anatomic repairs is that these techniques restrict the movement of the subtalar joint and also sacrifice the PB tendon, which is an important lateral stabiliser of the ankle. Therefore some surgeons have attempted near anatomic repair using allografts.15 Many surgeons feel that in view of long term complications and availability of modern fixation techniques non-anatomic reconstruction using PB should now be avoided.5
Practice point 4 C
C C
C
C
Proprioceptive training and neuromuscular strengthening form the cornerstone of conservative management Anatomical repair has the best results from surgery Surgery should also address associated problems such as peroneal tendon tear/instability, osteochondral lesion, impingement lesion Non-anatomic repairs sacrifice peroneus brevis and also affect subtalar joint kinematics Near anatomic allograft repair and arthroscopic anatomic repair are new techniques that show promising results
Surgery Surgery has been reserved for patients with chronic ankle instability who fail conservative treatment. However, there have been reports of acute surgical repair with the supposed benefits of a reduced incidence of instability.12 It remains to be seen if early surgery is better than functional rehab over the long term. Arthroscopy: a number of studies have demonstrated that there is a high incidence of intra-articular pathology in patients with chronic ankle instability. Arthroscopy is therefore indicated when surgery is planned. The majority of surgeons would perform arthroscopy in the same sitting as ligament reconstruction. However, some choose to perform arthroscopy as an elective procedure prior to ligament reconstruction which follows at a later date.13 Arthroscopy serves both diagnostic and therapeutic purposes. It helps to assess chondral injury and to treat synovitis, impingement lesions and osteochondral lesions. Those who prefer a staged approach to surgery have claimed that treatment of soft tissue impingement and osteochondral lesions may avoid the need for further surgery in some patients. Patients with refractory functional instability may also benefit from arthroscopic debridement.
Additional surgery: it is important to stress that if concomitant pathologies are present they also need to be addressed for a successful surgical outcome. For example, a fixed varus hindfoot may need to be corrected with a calcaneal sliding osteotomy, whilst a tight tendo Achilles or gastrocnemius may benefit from appropriate release. If a fibular ossicle is found this also needs to be addressed. Fixation should be attempted for large ossicles but small fragments may be excised.5
Outcome measures Ligament repair: a number of repair techniques have been described. Anatomical repair gives the best results and is indicated in most patients.13 Anatomical repair of the existing ATFL and CFL to bone was described by Brostrom but the modification by Gould is currently most popular. Gould recommended reinforcement of the repair using inferior extensor retinaculum. The availability of suture anchors allows direct insertion of ligament ends onto the fibula rather than suturing together torn ligament ends. Interestingly, anatomical repair is not only simple, it also restores ankle kinematics to near normal compared to ligament reconstruction techniques. Lately there has been interest in arthroscopic lateral ligament repair. These techniques aim to replicate arthroscopic Brostrom-Gould repair.14 This is still an evolving field and although early results have been published long term results are still awaited.
There has been a generally welcomed trend in orthopaedic surgery to record patient specific outcome measures. Although there are some outcome measures in use in foot and ankle surgery there is currently no widely accepted and validated outcome measure for patients with chronic ankle instability.5 It is therefore difficult to compare results across studies and to pool outcomes for meta-analysis. The Foot and Ankle Outcome Score (FAOS) has been validated in patients with lateral ligament reconstruction. The Cumberland ankle instability tool (CAIT)16 has also been used.
Conclusion CAI represents a spectrum of pathologies in and around the ankle. Careful clinical assessment is required for successful management. Most patients can be managed with conservative treatment. A number of different surgical options are available for those who fail conservative treatment. It is expected that future trials will concentrate on developing validated patient reported outcome measures so that objective evidence-based treatment recommendations can be made. A
Ligament reconstruction: ligament reconstruction can be performed using a number of options: native autografts, allografts or synthetic implants. The majority of UK orthopaedic surgeons would perform a revision anatomical repair for failure of a primary anatomical repair and only attempt ligament reconstruction for
ORTHOPAEDICS AND TRAUMA --:-
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REFERENCES 1 O’Loughlin PF, Murawski CD, Egan C, Kennedy JG. Ankle instability in sports. Phys Sportsmed 2009 Jun; 37: 93e103. 2 Yeung MS, Chan KM, So CH, Yuan W. An epidemiological survey on ankle sprain. Br J Sports Med 1994 Jun; 28: 112e6. 3 Hertel J. Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability. J Athl Train 2002 Dec; 37: 364e75. P, Vega J, de Leeuw PA, et al. Anatomy of the ankle ligaments: 4 Golano a pictorial essay. Knee Surg Sports Traumatol Arthrosc 2010 May; 18: 557e69. 5 Guillo S, Bauer T, Lee JW, et al. Consensus in chronic ankle instability: aetiology, assessment, surgical indications and place for arthroscopy. Orthop Traumatol Surg Res 2013 Dec; 99(suppl 8): S411e9. 6 Phisitkul P, Chaichankul C, Sripongsai R, Prasitdamrong I, Tengtrakulcharoen P, Suarchawaratana S. Accuracy of anterolateral drawer test in lateral ankle instability: a cadaveric study. Foot Ankle Int 2009 Jul; 30: 690e5. 7 de C esar PC, Avila EM, de Abreu MR. Comparison of magnetic resonance imaging to physical examination for syndesmotic injury after lateral ankle sprain. Foot Ankle Int 2011 Dec; 32: 1110e4. 8 Gaebler C, Kukla C, Breitenseher MJ, et al. Diagnosis of lateral ankle ligament injuries. Comparison between talar tilt, MRI and operative findings in 112 athletes. Acta Orthop Scand 1997 Jun; 68: 286e90.
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9 Lamb SE, Marsh JL, Hutton JL, Nakash R, Cooke MW, Collaborative Ankle Support Trial (CAST Group). Mechanical supports for acute, severe ankle sprain: a pragmatic, multicentre, randomised controlled trial. Lancet 2009 Feb 14; 373: 575e81. 10 de Vries JS, Krips R, Sierevelt IN, Blankevoort L, van Dijk CN. Interventions for treating chronic ankle instability. Cochrane Database Syst Rev 2011 Aug 10. Issue 8. Art. No.:CD004124. 11 Hubbard TJ, Cordova M. Effect of ankle taping on mechanical laxity in chronic ankle instability. Foot Ankle Int 2010 Jun; 31: 499e504. 12 Petersen W, Rembitzki IV, Koppenburg AG, et al. Treatment of acute ankle ligament injuries: a systematic review. Arch Orthop Trauma Surg 2013 Aug; 133: 1129e41. 13 Rogers M, Park D, Singh D, eds. Consensus of the 3rd round table. Barcelona: Ortho solutions Ltd., June 2013. 14 Nery C, Raduan F, Del Buono A, Asaumi ID, Cohen M, Maffulli N. €m-Gould for chronic ankle instability: a Arthroscopic-assisted Brostro long-term follow-up. Am J Sports Med 2011 Nov; 39: 2381e8. 15 Miller AG, Raikin SM, Ahmad J. Near-anatomic allograft tenodesis of chronic lateral ankle instability. Foot Ankle Int 2013 Nov; 34: 1501e7. 16 Donahue M, Simon J, Docherty CL. Critical review of self-reported functional ankle instability measures. Foot Ankle Int 2011 Dec; 32: 1140e6.
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