Excerpt from a YouTube presentation explaining how even minor vertebral slippage (degenerative spondylolisthesis, e.g., Grade 1–2) can biomechanically narrow foraminal canals and the spinal canal, producing foraminal compression and related symptoms. The speaker gives rough anatomic measurements (foraminal diameter ~10 mm; narrowed areas ~7–8 mm by 4–5 mm) to illustrate how quickly space can become tight.
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And because this slippage literally is biomechanical, so to speak, you can develop symptoms of compression as that bone slides forward. You got those foraminal canals on the left and the right side. The superior aspect of that canal is the top bone. The inferior aspect of that canal, bottom half of the hole, is the inferior bone. So when the top bone slides, that offsets that hole, just like a keyhole. And you're going to end up with potential for foraminal compression. Okay. Of course, going down the backside behind the vertebral body is the spinal cord spinal canal. So as you see that shift there as well, remember, we're talking about a healthy spinal canal. You're talking about 10 millimeters of diameter there in the foraminal canals. You might be talking, you know, 7, 8 millimeters by 4 to 5 millimeters somewhere in that vicinity. Obviously, everybody's a little bit different, but you can see where this gets tight real quick. Even minor slippages, as they're saying here, Grade one, grade two, you know, small changes can add up really quick when you're talking about tight spaces, specifically amongst the spine.
