*1.2.3 Neuromuscular structure*

The peroneal musculature is the dynamic stabilizer of the lateral ankle joint. Lateral ankle sprains may cause injury to the ATFL as well as to the peroneal muscles. Not only can the muscular fibers be injured, the neuromuscular function can also be affected. It has been reported that the reaction time of the peroneal muscles may be delayed in patients with a history of repeated sprains, which may increase the risk of another lateral ankle sprain when the ankle lands in a supinated position [21]. This delay may be related to the deafferentation of receptors in the muscle tendon and ligaments around the ankle joint after a sprain injury [22].

Proprioception deficits are frequently encountered in patients with CAI. The dysfunction of proprioception will result in poor joint position sense, which means

#### **Figure 2.**

*Superficial and deep layers of deltoid ligament. (a) Superficial deltoid ligament. (1) Tibionavicular ligament, (2) tibiospring ligament, (3) tibiocalcaneal ligament, (4) deep posterior tibiotalar ligament, (5) spring ligament complex (plantar and superomedial calcaneonavicular ligaments), (6) anterior colliculus, (7) posterior colliculus, (8) intercollicular groove, (9) sustentaculum tali, (10) medial talar process, (11) lateral talar process, (12) navicular, (13) navicular tuberosity. (b) Deep deltoid ligament. (1) Tibionavicular ligament, (2) tibiospring ligament, (3) tibiocalcaneal ligament, (4) deep posterior tibiotalar ligament, (5) spring ligament complex (superomedial calcaneonavicular ligament), (6) medial talar process, (7) sustentaculum tali, (8) medial talocalcaneal ligament, (9) tibialis posterior tendon (from Vega et al. [68]).* in a patient with CAI that the actual ankle joint position may be much more inverted than perceived by the patient [23]. This error in joint position sense may increase the risk of lateral ankle sprains.

Several modifications of the stress tests have been postulated such as the varus talar tilt test combined with an internal rotation pivot stress (VTTT with IR) and the anterior talar palpation (ATP) test [28, 29]. The VTTT with IR adds an internal rotational stress on the hindfoot with varus stress, which may better detect the rotational instability in ATFL deficiency judging from its orientation [28]. The ATP test increases the sensitivity of traditional anterior drawer test by pressing the examiner's thumb on the anterolateral ridge of the talus to better detect the anterior

The superficial deltoid ligament can be evaluated using the external rotation test. With the sitting patient's leg relaxed and hanging free, the degree of ankle external rotation of both legs can be compared manually. The eversion stress test can be used

Plain weight-bearing radiographs of the ankle and foot are essential in the evaluation of patients with CAI to exclude any bony lesions and malalignment. Osseous fragments on the medial or lateral malleolar tip may indicate ligamentous

Dynamic radiographs can be performed manually, intraoperatively, or using a Telos stress device to demonstrate the anterior drawer test, the talar inversion, and the eversion test (**Figure 3**). For lateral ankle ligaments, a stress radiograph is considered positive when more than 5° difference compared with normal ankle or

Dynamic radiographs are useful for determining the extent of instability objectively and for documentation purposes. The reported specificity of dynamic radiographs is high, but their sensitivity is low [32]. A recent study showed that preoperative stress radiographic findings do not affect the clinical outcomes of CAI after surgical treatment [33]. Therefore, the dynamic radiographs are better suited

*Dynamic radiographs. A dynamic test using the Telos stress device showing marked varus tilt and anterior*

talar translation during the anterior draw [29].

*Diagnosis and Treatment of Chronic Ankle Instability DOI: http://dx.doi.org/10.5772/intechopen.89485*

*2.3.1 Plain radiographs and dynamic radiographs*

more than 10° absolute varus tilt is observed [31].

**2.3 Image studies**

or retinacular avulsion.

for follow-up than for diagnosis.

**Figure 3.**

**87**

*subluxation of the talus.*

to assess the deep deltoid ligament by similar manner [30].
