Unilateral arch hypertrophy with spinous process tilt: a sign of arch deficiency.

Unilateral arch hypertrophy (UAH) may be generated by a contralateral deficiency which is most commonly a pars defect (43 out of 50 patients studied). Such a defect can also cause rotational instability. When present, both can be easily detected on simple anteroposterior views through the resulting pedicular and pars asymmetry and spinous process tilt. From simple anteroposterior views, one can predict that at least one arch defect does exist, that it is unstable, and not of recent origin

Radiologie de l'instabilité rotulienne: intérêt du cliché de profil et de la vue axiale à 30 degrees rotation externe.

Patellar instability is often missed by conventional axial views because transient subluxation of the patella essentially occurs during the first degrees of knee flexion (0 to 30 degrees), a position in which bilateral routine axial views are impossible to obtain. However, simple radiographic methods enable detection of both patellar instability and the often associated trochlear depth insufficiency. Every lateral radiograph of the knee depicts the depth of the proximal trochlear groove which is superior to 5 mm in a normal population. Upper trochlear depth insufficiency is frequently observed in the case of major patellar instability. Lateral views of the knee recorded during the first degrees of flexion (0 degrees-15 degrees) enable detection of patellar maltracking through the patellar tilt always associated with significant subluxation of the patella. Patellar maltracking may be studied dynamically by lateral fluoroscopy during progressive flexion of the knee. Unilateral 30 degrees axial radiographs with forced lateral rotation of the leg are definitely superior to conventional axial views in detecting transient patellar subluxation. These simple radiographic modalities should replace computed tomography in the search for patellar instability

Patellofemoral joint: 30 degrees axial radiograph with lateral rotation of the leg.

A method for axial radiography of the patellofemoral joint has been developed that combines a forced lateral rotation of the leg with 30 degrees flexion of the knee. This view can be obtained without any special device and is definitely superior to the 45 degrees routine axial view in the detection of lateral subluxation of the patella. It should be obtained when patellar instability is suspected