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Wheeless' Textbook of Orthopaedics

Radiographic Studies for Ankle Sprains



- See: Radiographic Studies of the Foot and Ankle

- Static Films:
    - os subfibulare:
          - historically, this has been considered to be an accessory ossicle located just below the ditsal fibular epiphysis;
                - it is distinguished from a fracture by its smooth borders, and by the fact that a fracture will preferentially involve the physis;
          - there is some recent evidence to suggest that this structure may represent a nonunion of an avulsion frx from the fibula;
                - patients may demonstrate ipsilateral ankle instability and absence of a similar ossicle on the contra-lateral foot;
          - reference:
                 The symptomatic os subfibulare:  Avulsion fracture of the fibula associated with recurrent instability of the ankle.


- Talar Tilt:
    - stress test w/ ankle wts:
          - examiner stabilizes the leg with one hand while inverting plantar flexed heel with the other hand;
          - alternatively, place the patient's leg in the lateral position, hanging off the table;
                 - a strap is applied around the ankle which courses around the lateral side of the ankle;
                 - a 4 kg wt is then applied which forces the ankle into inversion and plantar flexion;
          - other ankle may be used for comparison;
          - line is drawn across the talar dome and tibial vault;
          - degree of lateral opening angle is measured;
          - normal tilt is less than 5 deg, others say an abnormal value is twice the angle of the normal ankle or over 9 deg;
    - standing stress test:
          - may be more sensitive than other stress tests;
          - patient is stood on an inversion stress platform with the foot and ankle in 40 deg of plantar flexion and 50 deg of inversion;

- Anterior Drawer Test:
    - abnormal anterior translation is between 5 to 10 mm, or 3 mm more than other side;

- External Rotation Stress Test:
    - evaluates syndesmotic & deep deltoid ligament;
    - on AP view differnece in width of superior clear space between medial and lateral side of the joint should be < 2 mm;
    - these are static measurements of the talar position;
    - in normal ankle, talus may tilt up to 5 deg w/ inversion stress;
    - measurements of talar tilt using stress x-rays are used to evaluate lateral ligament stability;

- Arthrographic Studies of the Sprained Ankle:
    - leakage of the dye thru a particular ligament or thru the distal tibiofibular syndesmosis will pin point structure torn;
    - performed by inserting 22 gauge needle into the medial side of joint;
    - extra articular dye anterior to the laterala malleolus is always associated with a rupture of ATFL;
    - dye seen in peroneal sheath usually is caused by rupture of CFL;
    - extension of contrast > 3.5 cm above joint is c/w ligamentous injury;
    - arthrography needs to be performed within 1 week of injury or fibrin clots may seal any capsular tear;

- Decision Rules for Use of Radiography in Acute Ankle Injuries - Ottawa Rules
    - Jama, March 3, 1993 - Vol 269, No. 9;
    - ankle series are indicated if the patient has pain near the malleoli and one or more of the following:
           - age 55 years or greater
           - inability to bear wt immediately after injury & for 4 steps in ER.
           - bone tenderness at the posterior edge or tip of either malleolus;
    - foot series are indicated if the patient has pain in the midfoot and bone tenderness at:
           - navicular bone
           - cuboid
           - base of the fifth metatarsal
           - or is unable to bear weight



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, October 29, 2012 6:56 pm