Acute Pars Inter-Articularis Injury

Acute Pars Inter-Articularis Injury

Acute Pars Inter-Articularis Injury is sometimes called Lumbar Spondylolysis. It is a well-recognized cause of low back pain and is particularly prevalent in adolescence. Furthermore, this form of injury is seen in athletes rather than in sedentary individuals. In this article, we shall briefly talk about acute pars inter-articularis injury and how it is managed.

Clinical Anatomy

In acute pars inter-articularis injury, there is damage to the pars inter-articularis, which is a segment of the arch of the vertebra that connects the facet joints of the adjacent vertebrae. Some consider it to be a fracture of the vertebra in itself. The actual injury occurs due to alteration in shear forces that can place a great deal of stress upon the ligaments and the vertebral bones.

What is Acute Pars Inter-Articularis Injury?

Acute pars inter-articularis injury is a stress fracture or weakness of the bony segment that connects the facet joints between the vertebrae. Six out of 100 of the general population can have this condition, though in most cases it is acquired through athletic activity. It is particularly common in adolescence.

Acute pars inter-articularis injury often occurs at the level of the fifth lumbar vertebra (L5) followed closely by the fourth lumbar vertebra (L4).

Clinical Features

Many patients can remain asymptomatic for a long period of time. However, in those who do develop symptoms, low back pain is the common presenting feature. This pain can radiate into the upper part of the lower leg or into the buttocks. The pain tends to worsen during activity and is relieved with rest. Upon clinical examination, hyperextension of the opposite side can replicate the pain in the lower back on the affected site.


Acute Pars Inter-Articularis Injury is diagnosed through clinical history and radiographic examination. This involves taking X-rays and possibly a CT scan and MRI of the spine to define the extent of the damage. Twenty percent of defects are often visible on a plain X-ray and demonstrate a classic 'Scottie dog' appearance. A particularly important complication that must be kept an eye out for is one of 'spondylolisthesis,' which involves dislocation of the vertebra in a forward direction.

Once treatment has commenced and healing ensues, monitoring this through X-rays and CT scans is appropriate.

How is Acute Pars Inter-Articularis Injury Treated?

The use of over-the-counter pain medicines is often beneficial in the early stages. However, the use of non-steroidal anti-inflammatory drugs is not recommended, as they can slow down the healing of the bone. Once pain is adequately controlled, additional physical therapy may be required, such as the use of isometric contraction exercises and pulsed ultrasound therapies which can enhance blood flow and promote healing of the bone tissue.

In the event that conservative treatment options fail, patients may require surgical treatment. This is often offered in patients who have unbearable pain and have some form of nerve deficit due to damage to the nerves.


Acute pars inter-articularis injury is a common injury amongst athletic adolescents. Diagnosing acute pars inter-articularis injury is essential so that early treatment can be offered.

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