Radiological imaging plays a fundamental role in the study of HO and the multidisciplinary approach is fundamental.

Conventional Radiology, CT, MR, and nuclear medicine: each of them provide specific information useful for the definition of the location, size, and volume of HO.

Conventional Radiology.

Radiologically, HO is not detectable for a period of time between 1-2 months after the injury.

It’s essential to be able to adapt the radiographic technique to the specific needs of patients.

Management of these particularly fragile patients is a considerable problem in the implementation of X-ray examinations and other methods.

In the radiographic study of the shoulder, hip and knee, some essential x-ray projections were identified and were adapted to the specific characteristics of each patient.

Shoulder

Standard Grashey view projections are required and, if possible, two projections are acquired.

If the patient's condition is particularly debilitating, it can be carried out those projections in bed.

It's very important to acquire an image of the glenoid and humeral head on the glenoid plane, highlighting the joint relationships. 

In this projection, the central beam is oblique in the mediolateral direction by at least 25 ° and centered on the coracoid process (Fig. 4)

Occasionally, axial projection is required and it can be performed in bed by removing the headboard. (fig. 5)

Hip

The most suitable radiographic projections for the study of the pelvis and hip are essentially the following two.

Anterior-posterior: it is possible to use the patch to keep the correct position. Particular attention to rotations: both ASIS must be equidistant from the sensitive plane. (fig. 6)

Frog legs: this projection is preferably acquired for both hips at the same time (fig. 7).

The use of dedicated foam cushions is essential to facilitate the positioning of the lower limbs and prevent patient slipping (Fig. 8).

Knee

AP projection is performed according to standard criteria. The use of the patch can be useful to maintain the intra-rotation of the limb.

The lateral projection must be performed on the supine patient; this projection allows verifying overtime the variation of the femur's degree of flexion on the pelvis. (Fig. 9 and 10).

Sometimes it is useful to follow the physical characteristics of the patient to obtain diagnostic images (fig. 11).

For the radiological study of the other body segments, x-ray procedures need to be adapted to the patient's physical condition (fig. 12)

Computed Tomography has the ability to provide important information regarding the precise location of the calcifications and their relationship with the joints.

Low-dose protocols that include MPR sequences (Fig. 13) and 3D reconstructions (fig.14) are required.

Magnetic resonance provides information especially regarding soft tissues and allows you to view any masses and evaluate their vascularization.

However, it has low specificity, and therefore its role in the diagnosis of HO is rather marginal (soft tissue evaluation).

to study the bone in MRI, the following sequences are used: T1-TSE, to study morphology; T2-TSE, useful for viewing static liquids; STIR, which, with the suppression of the adipose tissue signal, allows to highlight any bone edema (fig. 15).

Nuclear Medicine

The triphasic bone scintigraphy, and in particular its first two phases (vascular and tissue), allows the detection of heterotopic ossification as low as about 2.5 weeks after spinal cord injury, while the third phase (bone) showing positivity with a delay of a week (fig. 16) 

The share of activity detectable in the bone phase of the scintigraphy peaks a few months after spinal damage, after which it gradually decreases until it returns to normal values within 6-12 months.

Radiotherapy 

There is moderate Level 4 evidence (SCIRE Project) that radiotherapy reduces the progression and recurrence of heterotopic ossification. 

according to the literature, a single 7 Gy session is indicated.