To answer this question, take another look at the lateral view (Figure 1b). You will notice that the fracture line has extended into the lamina. This raises the possibility of spinal cord involvement. Anytime there is disruption of the spinolaminar line, one must further evaluate the osseous integrity of the region and rule out cord involvement by referring to more advanced imaging.
Clay Shoveler’s fractures may result from a couple of different mechanisms. They can arise from a direct blow to the cervicothoracic junction. More commonly they represent an avulsion injury. During sudden hyperflexion, reactive protective musculature (rhomboids and trapezium) contracts as an antagonist to neck movement. Additionally, the spinous process in the lower cervical or upper thoracic region would be avulsed by abrupt antagonist tension of the supraspinous, interspinous and nuchal ligaments. This typically involves C6, C7 or T1. Isolated spinous fractures above C6 are rare.
But the most common scenario is a result of posterior muscular contraction in response to sudden rotational force of the head/neck relative to the trunk. The least common cause results from hyperextension from epileptic seizures (where neural arches impact one another and fracture).
Radiographic findings are:
- Most commonly at the C7 level
- Vertical lucent fracture line through the spinous process
- Displacement and distraction of the spinous process fragment inferiorly
- May create the classic “double spinous” sign on the AP view. This represents the attached root of the spinous and the detached spinous fragment (Figure 2).
Figure 2.AP View. Inferior displacement of the spinous tip leads to a double spinous appearance known as the “double spinous” sign.
The differential diagnosis includes anomalies such as a nuchal ligament ossification, persistent apophyseal growth center at the spinous and to a lesser extent supraspinous ligament calcification:
- Persistent Apophyseal Growth Center (Figure 3): May simulate an avulsion of the spinous tip. But, close observation of three key feature help differentiate this from clay shoveler’s fracture. First, opposing margins are smooth and sclerotic. Second, the distal ununited segment is in close proximity to the remainder of the spinous with no caudal displacement. Third, the ununited segment may have a concave margin, which is continuous with the convex surface of the opposing spinous.
- Nuchal Ligament Ossification (Figure 4): These are easily differentiated by their elongated shape and more posterior position. In addition, the spinous process remains intact. The nuchal ligament is often observed after the age of 40 and is often asymptomatic.
Figure 3. Lateral View. Nonunion of the secondary growth center of the C7 spinous process. Note the smooth, undisplaced sclerotic margins between the osseous segments.
Figure 4. Lateral View. Nuchal ligament ossification. The elongated shape of the nuchal ossification and intact spinous tip helps differentiate this from a clay shoveler’s fracture.
So what about treatment. These type of fractures are usually considered stable if the avulsed fragment remains in close proximity to its host. However, if there is a wide gap between the fragment and its host, then look for hidden anterolisthesis subluxation at that level. In this case, there are probably associated ligamentous tears and the segment may not be stable. If the fracture extends into the spinolaminar region, pedicle or pillar, you must rule out spinal instability, nerve root and spinal cord involvement.
These fractures may heal as a well aligned union, a malaligned union or as a non-union (ossicle). Once stability has been established, treatment begins with a conservative approach. In the acute stage a soft cervical collar may be used intermittently in the first few weeks in addition to other modalities directed towards the soft-tissues to help reduce inflammation. Manipulation above or below the level of involvement may be performed to patient tolerance as needed. If severe pain persists surgical excision of the avulsed fragment may be warranted. In this case, the patient received four weeks of care consisting of trigger point therapy, light message, acupuncture and manipulation to other segments as needed. The patient also transitioned into more active cervical rehabilitation and was pain free at eight weeks. Follow-up films at 2.5 months revealed osseous callous formation at the fracture site and five months complete osseous healing.