Post 85: Can we predict what your MRI will show…before the MRI

“Patients who have lumbar discectomy with predominant leg pain at initial presentation are known to have a better result than patients with primarily low back pain without radiation”
WHAAT!? You mean to tell me that patients with back pain only, don’t do well with a surgical approach? Yougottobekiddingme!
Obviously I joke. We can predict that a certain portion of the population may actually respond better to a surgical approach or other invasive interventions compared to therapy. Patients that have more leg pain than back pain may do better with a surgical approach than those with more back pain than leg pain.

“Of 27 patients who had only leg pain at initial examination, 26 (96%) were found subsequently to have an extruded fragment.”
Leg pain, in the absence of back pain, has a high rate of being an extruded disc fragment. What’s this mean? Picture a half-filled tube of toothpaste. Let’s start with the lid on. If you squeeze the back of the tube, the paste moves towards the front of the tube. This is similar to how a spinal disc reacts to movement. When you compress the back portion, in most healthy discs, the toothpaste consistency portion of the disc moves forward. Now, take the lid off. When you squeeze the tube, the paste comes out. Try to put it back into the tube…good luck. It doesn’t work. When the paste material in the disc comes out through an opening in the disc, this is called an extrusion.
“…33 of 39 (85%) patients with predominantly leg pain had an extruded fragment.”

The statistic to pay attention to is the high percentage of patients that either have all leg pain or mostly leg pain present with an extrusion. This information is learned simply by talking to the patient and paying attention to what the patient is saying. If you hear this pattern, think that there may be a discogenic lesion in the lumbar spine.

“Only 2 of 12 patients presenting with more back pain than leg pain were subsequently found to harbor an extruded fragment”

This sentence sounds ominous. “Harbor an extruded fragment”, sounds like harboring a fugitive. Funny thing…the way a therapist words the education portion with the patient can either be helpful or harmful. Harboring is a negative connotation and may actually increase the patient’s pain if described in this manner. The portion that is most important though is that only 12% of patients with more back pain than leg pain present (harbor) with an extrusion. An extrusion may be less likely found in a patient with more back pain than leg pain. This plays a role in the patient’s rate of improvement over time, so it is very important for all therapists to know this information. Unfortunately, if a PT is not reading the research, this information may never be learned. I only took one course in the previous 10 years that even mentioned this information.

“No difference was observed in the pain severity of patients with an extruded fragment, compared with those with a disc protrusion. Patients with an extruded fragment were more likely to experience a resolution of back pain at the onset of leg pain, than patients with a disc protrusion”

There are some theories about this. Let’s start again with some education. A protrusion is what happens when the toothpaste pushes against the tube, but the lid is still on. This means that the hydrostatic properties (big words) of the disc is still intact. Hydrostatic mechanism is simply stated that when you push on the back of the toothpaste tube, the paste moves to the front and when you push on the front of the tube, it moves to the back (in most cases, but not all cases this happens. There is another study that I may discuss if I can find it at a later date that discusses how older looking discs may respond differently).

One theory for the resolution of back pain is that the posterior longitudinal ligament (posterior = back of spine, longitudinal = up and down, ligament = ligament) no longer has pressure against the ligament when the disc loses the hydrostatic mechanism. The ligament, when irritated under experimental situations, is known to cause back pain to the side of ligament irritation (another study that I will have to find for a later blog). If there is no pressure against the ligament, it may be a factor in not experiencing back pain.

“Pain fibers are present in the outer layers of the annulus and posterior longitudinal ligament and produce severe central low back pain, when stimulated directly or stretched by injection of saline”
Over the years I have read so many studies. I also have a decent memory, so all of the stuff that I typed above I didn’t realize came from this study that I am writing about. I typically read an article and then come back and blog on it at a much later date. This quote says in more sciency terms what I said in the previous paragraph.

“The ability to predict the presence of an extruded fragment is clinically important because these patients have been reported to achieve a better result from discectomy and therefore case selection could be improved by a simple assessment of pain distribution on presentation”

WAIT!!! Not all patients with an extrusion need surgery!!! This is simply a starting point. If the patient presents with this pattern, but also demonstrates centralization of symptoms, the patient is expected for a good outcome.

Moral of the story: you are not your symptoms, but they can assist us in determining how to proceed with care.

Excerpts from:

Pople IK, Griffith HB. Prediction of an Extruded Fragment in Lumbar Disc Patients from Clinical Presentations. Spine. 1994;19(2):156-158.

Categories Physical therapy

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