Diagnosing, planning and evaluating osteochondral ankle defects with imaging modalities

Abstract

This current concepts review outlines the role of different imaging modalities in the diagnosis, preoperative planning, and follow-up of osteochondral ankle defects. An osteochondral ankle defect involves the articular cartilage and subchondral bone (usually of the talus) and is mostly caused by an ankle supination trauma. Conventional radiographs are useful as an initial imaging tool in the diagnostic process, but have only moderate sensitivity for the detection of osteochondral defects. Computed tomography (CT) and magnetic resonance imaging (MRI) are more accurate imaging modalities. Recently, ultrasonography and single photon emission CT have been described for the evaluation of osteochondral talar defects. CT is the most valuable modality for assessing the exact location and size of bony lesions. Cartilage and subchondral bone damage can be visualized using MRI, but the defect size tends to be overestimated due to bone edema. CT with the ankle in full plantar flexion has been shown a reliable tool for preoperative planning of the surgical approach. Postoperative imaging is useful for objective assessment of repair tissue or degenerative changes of the ankle joint. Plain radiography, CT and MRI have been used in outcome studies, and different scoring systems are available.

Keywords: Ankle; Cartilage; Computed tomography; Imaging; Magnetic resonance imaging; Outcome assessment; Radiography; Subchondral bone; Talus.

Figure 1

Weight-bearing radiographs [lateral (A), anterior-posterior mortise (B), and 4-cm heel-rise (C) views] showing an osteochondral defect (arrows).

Figure 2

Coronal (A) and sagittal (B) computed tomography scans of a left ankle, showing an osteochondral defect of the posteromedial talar dome. Note the clear visualization of the cyst with an intact subchondral bone plate.

Figure 3

Magnetic resonance imaging scans of coronal T1 (A) and T2 (B) and bone edema on a T2 image (C). Coronal T1 (A) and T2 (B) magnetic resonance imaging scans of a right ankle with an osteochondral lesion of the medial talar dome. Note that the extent of the bony defect is difficult to assess precisely due to the bone edema on a T2 image (C).

Figure 4

Ultrasound image (top) showing an osteochondral talar defect. A computed tomography scan (bottom) is shown for comparison.

Figure 5

Sagittal computed tomography images of a 14-year-old patient with an osteochondral defect of the medial talar dome. Normal helical CT (A) and a CT made in full plantar flexion (B) showing arthroscopic accessibility. CT: Computed tomography.

Figure 6

Radiograph of a left ankle with an ostechondral defect in the lateral talar dome, preoperative (A) and postoperative (B).

Figure 7

Coronal (A) and Sagittal (C) computed tomography-scans obtained 2 wk postoperatively, showing a medial osteochondral defect of the talus treated with arthroscopic debridement and microfracturing, these can be compared with 1-year postoperative computed tomography scans (B, D). Note the partial bony ingrowth of the defect.