Injuries about the ankle

Chapter 14 Injuries about the ankle

Ankle fractures 380

Mechanisms of injury 381

Classification of ankle fractures 382

Supination/lateral rotation injuries 383

Abduction injuries 384

Pronation/lateral rotation injuries (external rotation with diastasis) 385

Adduction injuries 386

Compression injuries 387

Diagnosis of ankle fracture 388

Principles of treatment 389

Fractures of fibula 391

distal to the syndesmosis 391

at the level of the syndesmosis 392

proximal to the syndesmosis 393

Closed reduction of ankle fractures 394

Treatment of multifragmented compression fractures 396

Lateral ligament injuries 397

Epiphyseal injuries 398

Sprain of inferior tibiofibular ligament 398

Ankle dislocation without fracture 399

Recurrent dislocation of peroneal tendons

Osteochondritis dissecans tali 399

Footballer’s ankle 399

Complications of ankle injuries 400

AO Classification: Tibia/Fibula,

Distal Segment 401

Malleolar Segment 402

Answers to self-test 404

1 Anatomical considerations (a): The ankle joint is often fairly compared with the mortise and tenon joint of the woodworker. The talus (1) resembles the tenon (T), and is supported by the two malleoli and the articular surface of the tibia (the ankle mortise). The lateral malleolus is firmly attached to the tibia by the strong anterior and posterior tibiofibular ligaments (2).

The ankle is not quite a true hinge joint; it can permit as much as 18° of rotation through a vertical axis.

2 Anatomical considerations (b):The talus is held in the mortise on the medial side by the very strong deltoid ligament (1), and on the lateral side by the lateral (external) ligament (2).

The anterior part of the upper articular surface of the talus is wider than the posterior part (3). When the foot is dorsiflexed, the talus pushes the fibula laterally (4) and is more firmly gripped in the ankle mortise.

3 Anatomical considerations (c): As in the case of the pelvis, the main anatomical structures may be likened to a ring. If this is broken in one place the injury is usually a stable one, and conservative treatment generally indicated. (The dotted lines indicate common sites of failure – the lateral, medial and posterior malleoli; the medial, lateral and anterior tibiofibular ligaments.) Additional breaks in the ring lead to instability, with often the need for surgical stabilisation.

4 Mechanics of injury (a): The function of the ankle mortise is threatened if the malleoli are fractured or the tibiofibular ligaments are torn. The stability of the talus may also be reduced by rupture of the medial or lateral ligaments. The commonest injury is when the talus is rotated in the mortise, fracturing one or both malleoli.

5 Mechanics of injury (b): External rotation of the talus may be produced in two different ways: 1. The foot may act as a long lever; any rotational force applied to the inside of the foot is transferred to the talus with a mechanical advantage as in any system of levers. Even greater leverage may occur if, for example, the foot is attached to a ski.

6 Mechanics of injury (c): 2. The axis of movement of the subtalar joint is known to run obliquely in the direction of the crease on this paper model (1).

Inversion of the heel, represented by folding the paper, results in external rotation of the talus (2) (Rose’s torque-converter principle). A common history is of the ankle ‘coggling over’ on uneven ground.

7 Mechanics of injury (d): The talus may be forced into relatively pure adduction as, for example, when the side of the inverted foot strikes the ground heavily. (The external rotation of the talus, produced by inversion of the calcaneus, being countered by the internal rotation of the strike, resulting in net adduction.)

8 Mechanics of injury (e): Similarly, if force is applied to the medial side of the heel and foot, the talus will tend to abduct in the ankle mortise.

9 Mechanics of injury (f): Many injuries occur during the course of walking or running. Under these circumstances there are additional forces transmitted to the posterior part of the inferior articular surface of the tibia (posterior malleolus).

10 Mechanics of injury (g): Compression injuries may be caused by: (1) falls from a height, forces being transmitted vertically from heel impact, or (2) following rapid deceleration in car accidents – sometimes aggravated by the pedals being driven into the front compartment and the ankle being forcibly dorsiflexed. Comminution is a feature of this type of injury.

11 Classification of ankle fractures: There are several classifications of ankle fractures; for completeness (which none achieve) many are complex to a degree that makes committal to memory nigh impossible. Fractures involving the ankle joint are often loosely referred to as Pott’s fractures; although the term is now somewhat archaic, there is some merit in its simplicity: in first degree Pott’s fractures, one malleolus is fractured (1): in second degree Pott’s fractures, two malleoli are fractured (bimalleolar fracture) (2).

12 Pott’s classification of ankle fractures ctd: In third degree Pott’s fracture (3) there is a bimalleolar fracture, with in addition a fracture of the posterior part of the inferior articular surface of the tibia – often referred to as the third malleolus. These fractures may also be referred to as trimalleolar fractures.

13 Pott’s classification of ankle fractures ctd: These fractures may be qualified by noting the presence of diastasis of the ankle or vertical compression.

(A) First degree Pott’s fracture with diastasis. (B) Second degree Pott’s fracture with vertical compression.

14 Weber classification of ankle fractures: This is based on the level of the fibular fracture, once thought to be the key to all ankle fractures.

Type A fractures occur distal to the syndesmosis.

Type B fractures start at the level of the tibial plafond; they often spiral in a proximal direction, and usually involve the syndesmosis.

Type C fractures start proximal to the syndesmosis which may be subject to a variable amount of damage. While this classification is simple, it does not take into account injuries to related structures (e.g. an isolated fracture of the fibula is not distinguished from one accompanied by a fracture of the medial malleolus).

15. The A-O classification of ankle fractures: This follows the lines of the Weber classification. (It was developed in association with the Weber classification and is sometimes referred to as the AO Weber classification.) It takes into account damage to other structures. (Interestingly the Groups within each Type tend to follow the Pott’s classification.) For full details of this classification see p. 402.

16. The Lauge-Hansen classification of ankle fractures: A fuller and widely accepted classification of ankle fractures is that of Lauge-Hansen which groups these fractures under double-barrelled headings. The first word in each group title refers to the position of the foot at the time of injury; the second refers to the direction in which the talus moves within the ankle mortise in response to the causal forces. There are five main groups; they have been arranged here in order of frequency and a common terminology of usage has been included.

17 Supination/lateral rotation injuries (external rotation injury without diastasis) (a): The foot inverts (1). Due to the torque-converter principle, the talus rotates laterally in the ankle mortise (2). The ankle joint structures are thrown under stress and fail in a regular sequence. As each structure fails, the next is stressed. The number of structures involved is dependent on the magnitude of the forces applied to the joint.

18 Supination/lateral rotation injuries (b): The rotating talus carries the fibula with it, leading first to rupture of the anterior (inferior) tibiofibular ligament (1). Alternatively, the ligament under stress may avulse its tibial attachment (T) (Tillaux fracture).

19 Supination/lateral rotation injuries (c): As external rotation continues, the fibula fractures in an oblique or spiral fashion (2). Note the direction of the spiral. If displacement continues, the fibular fragment drags off the posterior malleolar fragment (3) to which it is attached by the posterior tibiofibular ligament (or the ligament tears).

20 Supination/lateral rotation injuries (d): If rotation continues, the fourth structure to fail is the medial ligament or its attachment (the medial malleolus) (4). Such injuries are potentially very unstable and should be carefully distinguished from Stage 1 and 2 lesions.

21 Radiographs (a): A spiral fracture of the fibula at the level shown is typical of an S/L injury: in the lateral radiograph the fracture runs downwards and forwards, and there was no evidence of a posterior malleolar fracture. Although there is very slight incongruity between the upper surfaces of the talus and the ankle mortise, absence of tenderness on the medial side of the ankle suggested this was a Stage 2 or 3 injury.

22 Radiographs (b): The avulsion fracture of the medial malleolus indicates that this is a stage 4 S/L injury. There is lateral shift of the talus in the ankle mortise but the main mass of the fibula maintains its relationship with the tibia, so there is no true diastasis. Nevertheless, this is a very unstable injury.

23 Pronation/abduction injuries (abduction injuries) (a): The foot everts and the talus swings into abduction. The first structures to be affected are on the medial side. Either (A) the deltoid ligament ruptures (rare) or there is an avulsion fracture of the medial malleolus. The fragment may be small (B) or large (C). In either case the fracture line runs horizontally.

24 Pronation/abduction injuries (b): In second stage injuries of this type, both the anterior and posterior tibiofibular ligaments rupture. In the case of the posterior tibiofibular ligament, its tibial attachment may be avulsed instead.

25 Pronation/abduction injuries (c): In the third stage the fibula fractures, often close to the level of the joint. Comminution may occur, sometimes with the formation of a triangular fragment of bone with its base directed laterally. The distal fibular fragment is tilted laterally (medial angulation). The fracture line is often horizontal.

26 Radiographs (a): In this example of a Stage 1 abduction fracture, note the small medial malleolar fragment, the intact fibula, and the undisplaced talus.

27 Radiographs (b): In this Stage 3 abduction fracture, note the direction of talar tilting, the avulsion fracture of the medial malleolus with a large fragment and the distally-situated fibular fracture. The latter is not strictly horizontal, and its slightly spiral appearance suggests that there has been a rotational element. (As a first aid measure it would be normal practice to improve on this deformity (and that in Frame 33) to lessen the risks of skin necrosis on the medial side.)

28 Pronation/lateral rotation (external rotation with diastasis) (a): The talus is laterally rotated with the foot in the everted or neutral position (i.e. the foot does not invert). The rotating talus in the first stage produces an oblique fracture of the medial malleolus, or ruptures the deltoid ligament.

29 Pronation/lateral rotation (b): As the talus continues to twist, it impinges on the fibula. The anterior tibiofibular ligament is put under tension: in the second stage of P/L injuries, its tibial attachment is avulsed (Tillaux fracture) (2) or it ruptures.

30 Pronation/lateral rotation (c): In the third stage, the talus continues to rotate, producing a fracture of the fibula (3) that is spiral or oblique in pattern.

31 Pronation/lateral rotation (d): Note that in the lateral projection (A) the obliquity of the fibular fracture is in the opposite direction to that found in S/L injuries. The fibula may fracture proximally at the neck (B) – the Maisonneuve fracture. By Stage 3, the injury is unstable although stress films may be required to demonstrate diastasis (C).

32 Pronation/lateral rotation (e): If the talus continues to thrust laterally against the lateral malleolus, the posterior tibiofibular ligament now ruptures (A) or pulls off its bony attachment (B). The interosseous membrane rips and gross diastasis results (Dupuytren fracture – dislocation of the ankle: Stage 4).

34 Supination/adduction injuries (adduction injuries) (a): The foot inverts, but the tendency to external rotation of the talus as a result of the torque convertor effect is countered by the direction of forces applied to the forefoot by the impact. The overall effect is adduction of the talus in the mortise. If the forces are slight, a partial tear of the lateral ligament results (sprain of ankle).

35 Supination/adduction injuries (b): With more severe violence there will be a complete tear of all three bundles going to form the lateral ligament (A) or there will be an avulsion fracture of the lateral malleolus (with a horizontally running fracture) (B).

36 Supination/adduction injuries (c): In the second stage, the adducting talus strikes the medial malleolus causing a vertical or high oblique fracture (A). Note: (i) Instead of the medial malleolus being pushed off, there may be a compression fracture of the angle (B). (ii) Occasionally the medial malleolus may be broken off without damage first occurring to the lateral ligament.

37 Radiographs (a): This radiograph shows quite clearly an avulsion fracture of the tip of the lateral malleolus, typical of a Stage 1 supination/adduction injury.

38 Radiographs (b): Note in a typical Stage 2 injury the fracture line tends to run almost vertically from the medial corner of the ankle mortise. There is some rotation in the radiographic projection so that the fibular shadow overlaps the tibia.

39 Radiographs (c): In this child’s ankle there is a greenstick-type fracture of the medial malleolus with some compression of the angle between the medial malleolus and the inferior articular surface of the tibia.

40 Pronation/dorsiflexion (compression injuries) (a): Commonly the foot is dorsiflexed at the ankle in association with an upward compression force – usually from a fall from a height or from a road traffic accident (A).

As the talus dorsiflexes, its wide anterior part is forced between the malleoli, shearing off the medial malleolus (B).

41 Pronation/dorsiflexion injuries (b): As violence continues, the anterior tibial margin (2) is fractured, to be followed by the lateral malleolus (3).

42 Pronation/dorsiflexion injuries (c): Fractures of the anterior tibial margin show quite well in lateral projections of the joint and help to identify quite clearly this class of fracture. The talus may sublux anteriorly, carrying the marginal fracture with it.

43 Pronation/dorsiflexion injuries (d): With still greater violence the tibia fractures in an irregular fashion, often with great comminution. There may be great irregularity of the inferior articular surface of the tibia. Note in the lateral radiograph the large anterior marginal fracture. In the anteroposterior view note the typical medial malleolar fracture, the gross comminution, and the disruption of the inferior articular surface of the tibia. In this case the fibula has remained intact.

44 Other compression injuries: If a fall occurs on to the plantar-flexed foot, the posterior articular surface of the tibia may be fractured. In addition, fractures of both malleoli (as in typical pronation/dorsiflexion injuries) may occur when the broad anterior portion of the talus is driven between them.

45 Diagnosis of ankle fractures: (a) Swelling: Note the site and distribution of swelling and bruising, e.g. (1) Diffuse swelling in front of the lateral malleolus in many ankle injuries. (2) Egg-shaped swelling over the lateral malleolus shortly after complete lateral ligament tears or lateral malleolar fractures (McKenzie’s sign). (3) Gross swelling and bruising in many trimalleolar and compression fractures. Swelling and bruising which involves both sides of the ankle is highly suggestive of an unstable injury.

46 (b) Deformity: Note the presence of any deformity. Look for: (1) External rotation of the foot relative to the leg. If the medial malleolus is fractured and laterally displaced, the distal end of the tibia may become quite prominent under the skin. (2) Posterior displacement of the foot, a common feature of posterior malleolar fractures. Deformity is associated with unstable injuries of the ankle.

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Tags: Practical Fracture Treatment

Mar 20, 2017 | Posted by admin in ORTHOPEDIC | Comments Off

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