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18 Chronic ankle instability
Contents
Introduction
Anatomy
Clinical Presentation
Classification
Physical Examination
Imaging
Conservative Treatment
Operative Treatment
References
18.1 Introduction
The acute ankle sprain is the most common injury in both interscholastic and intercollegiate sports.(1,2). It is
estimated that approximately 30% of individuals will develop chronic ankle instability after the first initial
lateral ankle sprain.(3) Simple ankle sprains are not as innocuous as many believe, with high rates of
prolonged symptoms, decreased physical activity, recurrent injury, and self-reported disability.(3,4,5) Routine
non-operative treatment is successful in more than 90% of individuals. Surgery is reserved for those who fail
bracing, proprioceptive training, and kinetic chain strengthening.(6,7,8)
18.2 Anatomy
The ankle joint is more than a simple hinge joint as previously described. During its arc of motion, rolling and
sliding occur and the contours of the joint surfaces, in combination with the geometry of the ligaments, have
an intricate balance that is then acted on by multiple muscle groups. Leardini (9) and Bonnel (10) have both
provided excellent reviews of the complex anatomy and biomechanics of the ankle joint.
The important lateral ligamentous structures include the anterior talofibular ligament (ATFL), posterior
talofibular ligament (PTFL), and calcaneofibular ligament (CFL). 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 (11,12); it also
limits plantar flexion and internal rotation (13). 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 calcaneous.
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18.3 Clinical Presentation
The hallmarks of chronic ankle instability include repeated ankle sprains that have led to an altered patient
activity level. Important factors include injuries sustained, frequency of events, localization of pain, and prior
treatment modalities. The degree of disability appreciated by the patient is one of the most important factors
and can be significant in both high- and low-demand individuals.
18.4 Classification
The severity of injury can be defined by the degree of injury to the lateral ligaments or anatomic injury.
The anatomic classification includes Grades I through III:
Grade I - ATFL sprain
Grade II - ATFL and CFL sprain
Grade III - ATFL, CFL, and PTFL sprain
The American Medical Association uses a generalized scale based on the degree of 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 involves pathologic joint laxity. This is typically delineated by a talar tilt
discrepancy greater than to 10 degrees or an anterior drawer difference of 10 mm compared to the
contralateral ankle.
Functional instability is ascribed to sensorimotor and neuromuscular deficits that accompany
ligamentous injury, but mechanical instability is not necessarily present.
Alternatively, chronic ankle instability has been described by Karlsson as “ the subjective complaint of a
patient, apprehension or recurrent ligament sprain.”(14) This classification is supported by an increased
reaction time of the peroneus longus muscle in unstable ankles.(14-17)
18.5 Physical Examination
The initial patient evaluation starts with an assessment of standing hindfoot alignment. The contralateral
ankle should be evaluated for range of motion, strength, ankle drawer, and associated forefoot and hindfoot
abnormalities. This gives the examiner an appreciation for the patient’s baseline exam. The exam is then
repeated in the same manner on the pathologic side, noting the discrepancies between sides. Additionally,
particular attention should be paid to peroneal strength, subluxation/dislocation, or pain.
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An assessment of the degree of ankle dorsiflexion is done with the knee straight and flexed 30 degrees
(silfverskiold test). The inversion test evaluates the integrity of the CFL. This is performed by first dorsiflexing
the ankle to neutral and then inverting the hindfoot. Increased laxity is highly specific for CFL injury. The
anterior drawer test is performed with one hand stabilizing the tibia and the contralateral hand cupping the
heel and pulling forward. If the ATFL is disrupted the talus will translate anteriorly and with a more subtle
internal rotation because of the intact medial structures.
Patient cooperation is important for a sensitive examination. If the patient has had a recent recurrence, a
repeat examination may need to be performed at a later date. The tilt test and anterior drawer are very
specific for ligamentous injury when positive.
Other contributing factors such as hindfoot varus, plantar flexion of the first ray, and midfoot cavus should be
evaluated. Additionally, generalized ligamentous laxity is assessed with an evaluation of Beighton’s
hypermobility score. (18)
18.6 Imaging
Plain radiographs, including anteroposterior (AP), lateral, and mortise views of the ankle, should be obtained
to evaluate for boney pathology. Stress radiographs including anterior drawer and talar tilt may be helpful
when indicated. MRI of the ankle without contrast is important to evaluate for other associated pathology, in
particular peroneal tendon tears and osteochondral lesions, when the physical exam warrants.
18.7 Conservative Treatment
The cornerstone of conservative treatment is physical therapy. 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.
On initial presentation, a trial of physical therapy is warranted if no previous attempt had been initiated. Prior
to initiation of conservative treatment, an MRI evaluation is recommended to rule out associated pathology,
including peroneal tendon tear and osteochondral lesions of the talus, when associated tenderness warrants
it.
18.8 Operative Treatment
A subgroup of patients will continue to have dysfunction even after a well designed non-operative treatment
program. Clinical signs and symptoms are most critical for making the diagnosis. Radiographic criteria
include an anterior drawer greater than 10 mm (or 3 mm side differential) and a talar tilt test greater than 15
degrees (or >10 degree side differential). (19)
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Numerous procedures to address chronic ankle instability are described in the literature, ranging from
ligament repair to various tendon reconstructions. Reported success rates are greater than 80% no matter
which technique has been used. (19) However, simple imbrication of the lateral ligament complex with
incorporation of the extensor retinaculum has been shown to have an 85% to 95% success rate with a low
risk on nerve injury (20) The sural nerve is at greatest risk of injury and rates of nerve injury range from 7%
to 19%. Concomitant pathology that may contribute to recurrence should be addressed at the same time.
Patients with generalized ligamentous laxity in attenuated ligaments or varus alignment are at risk for failure.
Ankle arthroscopy is often performed in conjunction with lateral ligament reconstruction because of the high
incidence of chondral injury present in the chronically injured ankle, plus routine diagnostic tests may miss
intra-articular pathology. (21-23) Indications for arthroscopy have not been well-defined, but indications of
concomitant pathology should be present.
Anatomic reconstruction with a free tendon graft should be reserved for severe ligamentous laxity and
revision cases. (24,25) The various non-anatomic tendon transfers and tenodesis should be thought of as
historical in nature and the author would not endorse them.
18.9 References
1. Fernandez WG, Yard EE, Comstock RD. Epidemiology of lower extremity injuries among U.S. high
school athletes. Acad Emerg Med 2007;14(7):641--5.
2. Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15 sports: summary and
recommendations for injury prevention initiatives. J Athl Train 2007;42(2):311--9.
3. Itay SA, Ganel H, Horoszowski, Farine I. Clinical and functional status following lateral ankle sprains.
Orthopaedic Review 11(5), 73-76, 1982.
4. Braun BL. Effects of ankle sprain in a general clinic population 6 to 18 months after medical
evaluation. Arch Fam Med 1999;8:143--8.
5. Anandacoomarasamy A, Barnsley L. Long term outcomes of inversion ankle injuries. Br J Sports Med
2005;39(3):e14.
6. Gross P, Marti B. Risk of degenerative ankle joint disease in volleyball players: study of former elite
athletes. Int J Sports Med 1999;20:58--63.
7. Valderrabano V, Hintermann B, HorisbergerM, et al. Ligamentous posttraumatic ankle osteoarthritis.
Am J Sports Med 2006;34:612--20.
8. Fallat L, Grimm DJ, Saracco JA. Sprained ankle syndrome: prevalence and analysis of 639 acute
injuries. J Foot Ankle Surg 1998;37(4):280--5.
9. Leardini A, O’Connor JJ, Catani F, Giannini S. The role of passive structures in the mobility and
stability of the human ankle joint: a literature review. Foot Ankle Int 21(7):602-15, 2000
10. Bonnel F, Toullec E, Mabit C, Tourne Y, Sofcot. Chronic ankle instability: biomechanics and
pathomechanics of ligaments injury ans associated lesions. Orthop Tramatol Surg Res. 96(4):424-32,
2010.
11. Brostrom L: Sprained ankles. Part 1 : Anatomic lesions in recent sprains. Acta Chir Scand,
128:483-495, 1964.
12. Johnson E and K.L. Markolf: The contribution of the anterior talofibular ligament to ankle laxity. J
Bone Jt Surg (Am) 65-A(1):81-88, 1983.
13. Rasmussen O: Stability of the ankle joint: Analysls of the functlon and traumatology of the ankle
ligaments. Acta Orthop Scand, 211:1-75, 1985
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14. Karlsson J, Andreasson GO. The effect of external ankle support in chronic lateral ankle joint
instability: an electromyographic study. Am J Sports med. 20: 257-261. 1992
15. Konradsen L, Ravn JB. Ankle instability caused by prolonged peroneal reaction time. Acta Orthop
Scand. 388-390, 1990
16. Lovfvenberg R, Karrholm J, Sundelin G, Ahlgren O. Prolonged reaction time in patients with chronic
lateral instability of the ankle. Am J Sports Med. 23:414-417. 1995
17. Rosenbaum D, Becker H-P, Gerngross H, Claes L. Peroneal reaction times for diagnosis of functional
ankle instability. Foot Ankle Surg. 2000; 6:31-38.
18. Beighton PH, Horan F. Orthopedic aspects of the Ehlers-Danlos Syndrome. J Bone Joint Surg. 51-B,
444-453, 1969).
19. Coughlin MJ, Mann RA, Saltzman CL. Surgery of the Foot and Ankle,8th ed. Philadelphia: Mosby
Elsevier, c2007. Chapter 26, 1464-1470.
20. Baumhauer JF. Surgical considerations in the treatment of ankle instability. J. Athl Train 37:458-462,
2002.
21. Kibler WB. Arthroscopic findings in ankle ligament reconstruction. Clin Sports Med 15:799-804, 1996,
22. Taga I, Shino K, Inque M et al. Articular cartilage lesions in ankles wit lateral ligament injury: An
arthroscopic study. Am J Sports Med 21:120-127,1993.
23. Ogilvie-Harris DJ, Gilbart MK, Chorney K Chronic pain following ankle sprains in athletes: The role of
arthroscopic surgery. Arthroscopy 13:564-574, 1997.
24. Colville MR, Grondel RJ. Anatomic reconstruction of the lateral ankle ligaments using a split peroneus
brevis tendon graft. Am J. Sports med. 23(2):210-3, 1995.
25. Coughlin MJ, Matt V, Schenck RC. Augmented lateral ankle reconstruction using a free gracilis graft.
Orthop 25:31-35, 2002.
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