So the first question is, what is a transitional segment?
In simple terms, a transitional segment is where a segment of the spine, either at the very top or more commonly at the very bottom, has formed differently. So when you were in your mum's belly, your body decided to do things slightly differently and either created a 6th lumbar vertebrae or the sacrum decided to be larger and enclosed the L5, leaving you with only 4 lumbar vertebrae. Below are some pictures to help this make more sense.
This xray is a clear example of a 'Lumbarization' where the patient has a congenital 6th Lumbar vertebrae.
'Sacralisations' are the opposite where the sacrum (middle bone of the pelvis) is larger then normal, therefore encasing L5 and leaving the patient with only 4 lumbar vertebrae.
What does a transitional segment do?
The most common thing that I read on radiological reports is that a transitional vertebrae is an incidental finding meaning - "Hey look, that's a bit weird. I better mention it even though it doesn't really affect anything".
The truth of the matter is that in some cases a transitional segment is the MAIN reason why that patient is in pain and often why that patient has had CHRONIC LONGSTANDING pain that no one has been able to get better.
Yes in some cases a transitional segment can have absolutely no affect on anything and is just some odd anomaly that makes you unique but by saying they all are isn't recognizing the variety that transitional segments come in. They are all different and depending on the type and its combination with other mechanical issues that may be present in that individual, it can have a huge impact on pain and non-resolution of a lower back problem.
How can a transitional segment cause and sustain lower back pain?
Transitional segments, all of them, change the way your spine mechanically moves compared to the ideal. But for the purposes of this blog, lets just discuss the two most common ways.
The first is when you have a lumbarization, or an additional 6th lumbar vertebrae, most commonly you will have an additional disc. Now again this doesn't have to mean anything significant, but in a lot of cases this disc does create problems. It is another structure that can become damaged and create pain or it can protrude back into the spinal canal creating pressure on nerve roots causing stronger pain. Because this disc sits at the level between S1 and S2, it will sit lower and commonly on an angle forward, subjecting it to more force. basically a person with this situation going on in their lower back has less margin for error. Now if you combine this type of congenital anomaly with flat feet for example, (which shifts your centre of gravity forward causing an increased sacral base angle) you will almost certainly have lower back pain that is stronger and a consistent feature in your life. Not a great scenario.
The other common way a transitional segment can affect lower back pain is when you have what is called a partial sacralization. This is where on side of L5 your body decided to make it the sacrum but on the other side it is a freely moving L5 segment. Its like a transition of a transitional segment. Half/half. The problem this creates is that one side is capable of movement while the other is fused bone. What usually happens is the spine and pelvis will slowly twist in adaptation to unilateral movement, causing a lumbar scoliosis and rotated and laterally flexed pelvis. These types of patients often have unilateral lower back pain, most commonly from a ligament that has given up on life due to being over worked.
Why do transitional segments make me mad?
Simply put they are either not diagnosed because less and less practitioners are ordering xrays and relying solely on their examination skills, or they are found on an xray and disregarded as irrelevant.
Think about it, if you are examining a patient and you find one side of L5 isn't moving much you'll probably conclude they are restricted there and try and move it right? What if its fused, solid bone??!!!!!!!
The reason I wrote this blog is because in the last fortnight I have had 6 new patients come in with different varieties of the same issue. A transitional segment that no one cared to take an xray of and properly diagnose. In all 6 cases the patient had not been getting better with the treatment they were undertaking and in 3 of the cases, these poor people have been to a bunch of practitioners all of whom had not xrayed and not diagnosed the problem correctly.
So what should you do as the patient?
My adivce to you is, if you have had a long standing lower back issue and it's not resolving - and no one has ordered an xray of your lower back - go get one! If it mentions a transitional segment, discuss it with your practitioner and if you get the 'Its an incidental finding' answer then seek a second opinion.