Oblique View of Lumbar Spine

This view is particularly useful to show the pars interarticularis region and the apophyseal joints. Note that the pars interarticularis is a purely radiological term, its equivalent anatomically being the anterior part of the lamina. The oblique view causes a certain well- known appearance of a Scottie dog: the dog's collar is the pars interarticularis, the eye is the pedicle, the nose is the transverse process and the ear is the superior articular facet. Defects of ossification of the pars may lead to spondylolisthesis. Again, as in the cervical spine, facet articulation disorders can be seen.

Scottie dog
Scottie dog.

Cobra Head Sign

Cobra Head.
The cobra head sign is characterized by bulbous dilatation of the distal end of the ureter with a surrounding radiolucent halo, seen within the contrast material–enhanced bladder on intravenous urograms.

The cobra head sign is classically seen with an intravesical ureterocele. This type of ureterocele is also termed orthotopic, since it arises from a ureter with a normal insertion into the trigone. The term ureterocele denotes a cystic ballooning of the distal end of the ureter. What causes ureterocele is not clear. However, the anatomic basis and the mechanism of formation described in the literature is as follows: An intravesical ureterocele results from the prolapse of the mucosa of the terminal segment of the ureter through the ureterovesical orifice into the bladder. This prolapsed ureteral mucosa carries with it a portion of the continuous sheet of the bladder mucosa around the orifice. The prolapsed segment thus has a wall that consists of a thin layer of muscle and collagen interposed between the bladder uroepithelium and the ureter uroepithelium. Since the terminal ureteral orifice is usually narrowed and partially obstructed, and since there is no muscle support for the double mucosal walls of the prolapsed segment, it dilates. This dilated segment fills with urine and protrudes into the bladder.

Frontal urogram after intravenous contrast material administration shows bulbous dilatation of the distal end of the left ureter. Note the surrounding radiolucent halo (arrows).
At intravenous urography, the lumen of the ureterocele is usually filled with contrast material and is surrounded by opacified urine in the bladder. Since the double mucosal wall of the ureterocele is visible as a thin lucent line or halo surrounding its lumen, the ureterocele is outlined, giving the appearance of a cobra head.

In conclusion, the cobra head sign, when present, allows DIAGNOSIS of a URETEROCELE. However, causes of pseudoureterocele, such as a tumor or calculus, need to be ruled out on the basis of the appearance of the surrounding radiolucent halo.

Osgood–Schlatter Disease

Osgood–Schlatter disease (also known as tibial tubercle apophyseal traction injury) is an irritation of the patellar tendon at the tibial tuberosity.  The condition occurs in active boys and girls aged 9–16 years coinciding with periods of growth spurts. It occurs more frequently in boys than in girls. It has been suggested the difference is related to a greater participation by boys in sports and risk activities than by girls.

Lateral radiograph of the knee demonstrating fragmentation of the tibial tubercle with overlying soft tissue swelling.

The condition is usually self-limiting and is caused by stress on the patellar tendon that attaches the quadriceps muscle at the front of the thigh to the tibial tuberosity. Following an adolescent growth spurt, repeated stress from contraction of the quadriceps is transmitted through the patellar tendon to the immature tibial tuberosity. This can cause multiple subacute avulsion fractures along with inflammation of the tendon, leading to excess bone growth in the tuberosity and producing a visible lump which can be very painful when hit.

Diagnosis is made clinically, and treatment is conservative with rest, and if required acetaminophen (paracetamol) or ibuprofen. The condition usually resolves in a few months.