Ultrasound imaging of bone fractures

Abstract

Ultrasound imaging is widely used to evaluate the neuromusculoskeletal system, and recently, a particular interest is mounting in assessing the bone tissue and fractures. Ultrasound can be considered a valuable diagnostic tool to perform a first-line evaluation of bone tissue, especially in particular settings without direct access to X-ray imaging and/or in emergency conditions. Moreover, different healing phases of bone fractures can be accurately assessed by combining the B-mode modality and (high-sensitive) color/power Doppler optimizing the management of patients-e.g., planning of progressive loads and rehabilitation procedures. In this review, we summarized the role of ultrasound imaging in the management of bone fractures and described the most common sonographic signs encountered in the daily practice by assessing different types of bone fractures and the progressive phases of the healing process.

Keywords: Bone fracture; Fracture healing; Ultrasound.

Fig. 1

Cadaveric anatomy of bone tissue. The bone presents an inner portion with a trabecular texture (Tra) and an outer component—compact in nature—known as cortical bone (Co) (A, B). Of note, the periosteum (white arrowheads) tightly envelops the surface of the bone and, if damaged, allows the blood to diffuse toward the epi-periosteal space (black dotted line) (C). Mu: muscle tissue, yellow arrowhead: fat tissue

Fig. 2

Normal sonographic findings of the bone tissue. A longitudinal view of the lateral elbow in a young volunteer clearly shows the cartilaginous epiphysis (yellow dotted lines) of the radial head (RH) and lateral epicondyle (LE); of note, the hyperechoic lines (yellow arrowheads) within the hyaline cartilage are the epiphyseal ossification centers (A). Likewise, a longitudinal scan of the suprapatellar region in the knee shows the physis (green arrowhead) in between the metaphysis (Met) and epiphysis (Epi) of the distal femur in a child (B). Importantly, focal interruption of the (hyperechoic) cortical bone can be related to the presence of nutritional foramina (white arrowhead) crossed by feeding vessels (red arrowhead) (C). Pat patella

Fig. 3

Pathological sonographic findings of the bone tissue. The comparative sonographic assessment shows a continued hyperechoic cortical bone of the patella (Pat) with a tensioned patellar ligament (white arrowhead) on the healthy side (A); instead, cortical defect (white asterisk) of the patella (Pat), diastasis of bony fragments (white arrows), and deformation of the patellar ligament (yellow arrowhead) are clearly visible in the post-traumatic knee (B). Of note, the disruption of the bony cortex allows the US beam to partially penetrate within the bone tissue generating an echoic wedge (void arrowhead) (B)

Fig. 4

Impact fractures and avulsion fractures. Longitudinal view (A) shows the impact fracture (white arrowhead) of the radial head (RH), but only by performing the transverse scan (B) the degree of rotation (white dotted arrow) of the bony fragment can be clearly observed. Likewise, cortical bone depression (yellow arrowhead) on the posterior surface of the humeral head (HH)—filled with fibrotic tissue (yellow asterisk)—can be observed in a patient with previous anterior subluxation of the shoulder (C). Unlike the post-acute injuries, in the acute phase of trauma (D) the misalignment of the cortical bone (green arrowhead) is usually coupled with the periosteal bulging (red arrowhead) and subperiosteal hematoma (white asterisk). Of note, avulsion fractures in the pediatric population (E) can show a simultaneous shifting of the cartilaginous epiphysis (yellow dotted line) and the epiphyseal ossification center (green arrowhead) located within the hyaline cartilage. LE lateral epicondyle, RC rotator cuff, AIIS anterior inferior iliac spine

Fig. 5

Stress fractures and healing phases. Focal thickening of the periosteum (yellow arrowhead), the disappearance of the reverberation artifact (void arrowheads) of the cortical bone, and lamellar calcifications (white arrowhead) within the periosteum are the most common sonographic findings in the stress fractures (A, B). Using high-sensitive color Doppler to follow up the healing phases of the stress fracture, microvasculature (red arrowheads) within the thickened periosteum (yellow arrowhead) (C) and penetrating vessels (orange arrowheads) crossing through the cortical bone (D) can be observed

Fig. 6

Advanced stage of the bone callus. In the advanced stage, the bone callus (white arrowhead) presents as a hyperechoic line similar to the surrounding normal bone cortex, but the underlying reverberation artifact (void arrowhead) can be absent (A). Of note, the aforementioned artifact stops abruptly exactly at the transitional zone (yellow dotted line) from the normal bone cortex to the bump of the callus (white arrowhead) (A, B). No vascular signals (C) can be visualized within/surrounding the bone callus (white arrowhead) defining the completed healing status of the bone fracture (D). sV superficial vein