12.40. Radiographs (3): In the standard AP and lateral projections do not mistake (A) the common os trigonum accessory bone and
(B) the epiphyseal line of the fibula for fractures. The amount of tibiofibular overlap
(C) is dependent on positioning and any diastasis. The os fibulare (D) is thought to represent an avulsion of the anterior talofibular ligament, and may be associated with instability.
12.41. Radiographs (4): The articular margins of tibia and talus should appear as two congruent circular arcs. If there is some difficulty in positioning that cannot be improved upon, four arcs will be seen. Two pairs should be congruent, as shown. If not. there is a subluxation.
12.42. Radiographs (5): Note any widening of the gap (A) between talus and medial malleolus: this is suggestive of diastasis (compare its size with the one between the upper surface of talus and the tibia: they should normally be equal). (B) Note the presence of any defects in the articular surface of the talus, suggestive of osteochondritis tali. CT and MRI scans may help in the doubtful case.
12.43. Radiographs (6): (C) Note any irregularity in the joint surfaces that may suggest previous fracture, e.g. of the posterior malleolus; note any anterior exostoses of the tibia (and/or the talus), which are a feature of footballer's ankle. (D) Examine the articular margins for exostoses, joint space narrowing and cystic change, which are common features of osteoarthritis. If these are present, look for a possible cause (such as osteochondritis dissecans), as primary osteoarthritis of the ankle is uncommon.
12.44. Radiographs (7): Look at the malleoli, where deformity (F) or rounded shadows (H) suggest previous avulsion injuries. Distortion of the talus occurs in association with talipes deformities (I) and after injuries which have resulted in avascular necrosis, and where there may be increases in bone density.
12.45. Radiographs of the ankle: Examples of pathology (1): The upper articular surface of the talus is distorted on its medial side.
Diagnosis: the appearances are typical of osteochondritis dissecans. More complete assessment of the defect may be obtained by a CT or MRI scan.
12.46. Pathology (2): This inversion film shows tilting of the talus in the ankle mortice. There was no tilting elicited in comparison films of the other side. Diagnosis: unilateral complete tear of the lateral ligament.
12.47. Pathology (3): There is a large defect in the talus, which also shows increased density interiorly. Diagnosis: tuberculosis of the ankle with gross involvement of the talus.
12.48. Pathology (4): There is gross decalcification of the ankle following a minor fracture in the foot. The ankle was stiff and painful, and there was marked swelling of the foot and leg below the knee. Diagnosis: Sudeck's atrophy (post-traumatic osteodystrophy, complex regional pain syndrome).
12.49. Pathology (4): The radiographs show gross disorganization of the ankle.
Diagnosis: Neuropathic ankle joint (Charcot's disease). In this case the pathology was syphilitic in origin.
12.51. Pathology (6): There is narrowing of the joint space and the rounding of the upper articular surface of the talus (known as a so-called 'ball and socket' ankle joint). Diagnosis: osteoarthritis of the ankle. This was secondary to fracture, although all traces of this in the AP projection have disappeared.
12.50. Pathology (5): The talus is grossly misshapen and its upper articular surface flattened: clinically this was associated with pain, swelling and stiffness of the ankle and foot. There was a history of a severe injury to the ankle and foot a year previously. Diagnosis: compression failure of the talus from avascular necrosis, with secondary osteoarthritic change. This occurred as a sequel to a dislocation of the talus, in spite of a good reduction.
12.52. Pathology (7): The bones of the ankle and foot show evidence of disuse osteoporosis, having a ground-glass appearance outlined with narrow, dense cortical margins. The ankle joint space is absent, and there is bony continuity between the talus and the tibia. Diagnosis: bony ankylosis of the ankle following a chronic joint infection (TB).
Anatomical features 272 Conditions commencing or seen first in childhood 275 Talipes equinovarus 275 Tolipes calcaneus 276 Skew foot 276 Intoeing 276 Flat foot 276 Pes cavus 276 Kohler's disease 277 Severs disease 277
Conditions affecting the adolescent foot 277 Hallux valgus 277 Peroneal (spastic] flat foot 278 Exostoses 278 Conditions affecting the adult foot 278 Hallux rigidus 278 Adult flat foot 279 Splay foot 279 Anterior metatarsalgia 279 March fracture 280 Freiberg's disease 280 Plantar (digital) neuroma (Morton's metatarsalgia) 280 Verruca pedis (plantar wart) 280 Plantar fasciitis 280 Mallet toe, hammer toe, claw toe, curly toe 280 The nail of the great toe 281 Rheumatoid arthritis 281 Gout 281
Tarsal tunnel syndrome 281 Diagnosis of foot complaints 28 1 The mature foot: summary of the key stages in examination ¡13-18) 285
Inspection 286-289 Foot posture 289-292 Circulation 292-293 Tenderness 293-296 Plantar neuroma 294-295 Tarsal tunnel syndrome 295-296 Movements 297-299 Footprints and shoes 299-300 Radiographs 300-304 Pathology 304-306
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