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What Does It All Mean? I'm So Confused!

Anyone with a spinal deformity who has visited a spine specialist has likely heard one or more of the terms above. In this article, we’ll try to take the mystery out of these terms since they certainly aren’t words you use in everyday conversation – unless you’re a spine surgeon, that is!!

So, what do they mean?

Luckily, you don’t have to know, but never hesitate to ask questions if you want to understand more of what your doctor is talking about. At many offices, your doctor may have residents and fellows who see patients with him or her. These residents and fellows are in training and learning all they can so one day they will be able to treat patients of their own. After examining your spine, including having you bend to the front, back and both sides to see how flexible your spine is, your surgeon and the residents and/or fellow will discuss your spine. They will probably use a lot of these words or phrases to plan the best treatment for you. When they are done with their discussion, your surgeon or a nurse should meet with you to explain things in plain language so you and your family will understand the plan too. Again, never hesitate to ask questions.

All these technical words describe things associated with your spine – part of the evaluation to determine exactly what type of curve you have and what the best treatment will be. Doctors will often have a way of classifying the various curves in your spine or naming variations of different treatments. This gives them a common baseline for discussing and getting advice about your case, even when that person can’t see your x-rays. This makes it a lot easier for them to communicate and picture your spine in their mind, based on the known criteria. For example, if you were trying to tell a friend about somebody you both had seen earlier, saying “she was the girl with long hair,” isn’t nearly as descriptive as saying, “she was the tall girl, with long red hair worn in two braids”. In medical terminology, saying the patient has a 53-degree curve doesn’t help the consultant picture your spine in their mind as well as being told that the patient is 11 years old, skeletally immature, Risser 1 with a 53-degree right thoracic curve from T6 to T11 and a compensatory left lumbar curve with a C modifier. (See glossary at the end of the article for explanations of what these words mean.)

What it all means as far as you are concerned, is that your surgeon is evaluating your spine and everything that is involved with your scoliosis, and using that information to determine what the best treatment is for you. If you’ve had surgery, you know that as part of your pre-operative evaluation you had x-rays done standing and lying down, bending side to side, and sometimes with people pushing on your curves or pulling on your head and legs to stretch you out. Those are called flexibility x-rays and give your surgeon a good idea about how flexible your spine is and how much correction you are likely to get with surgery. Also, based on certain criteria, they can determine which curve is your primary structural curve and if the curves above and below it are structural as well, or compensatory, meaning they don’t need to be fused.

They look at your hips, waistline, shoulder heights, how straight you stand, and if you lean to one side or the other. They evaluate you from the side to assess your kyphosis to see if they need to give you more or take some away. You may wonder why your shoulders have anything to do with anything – but what you don’t know is if they correct your thoracic spine too much, or fuse too far up on your spine, that could make one shoulder higher than the other. They want to fuse as much of your spine as you need fused for successful treatment that will straighten your spine, give you good balance, and hopefully last for the rest of your life, but at the same time, fuse as few vertebrae as possible to leave you with the most motion.

It has always been a subject of debate among surgeons, at which vertebra to start and stop the fusion and instrumentation. Many different surgeons do similar surgeries but may have their individual techniques that they feel work well. There will always be some that look at that 53-degree curve and feel it’s best to fuse and instrument to T12, the last thoracic vertebra and others that will always think it’s best to include L1, the first lumbar vertebra. In most cases, neither decision is right or wrong. It’s a difference of opinion and what has worked best in their hands for their patients. You’ll hear terms like upper and lower END vertebrae (UEV and LEV – where the curve begins and ends), and upper and lower INSTRUMENTED vertebrae (UIV and LIV – where the instrumentation begins and ends).

That type of debate is what research studies are made of. Some surgeons may look at all patients fused to, for example, T12 and all those fused to L1 and compare their pre- and post-operative x-rays. They’ll evaluate what the effect of both levels have had on the adjacent vertebrae, discs, and compensatory curves. Did the unfused spine respond as they predicted? If there are striking differences in the outcomes, the study may be presented at a meeting to share the results with other medical professionals, which, in turn, can change how surgeons approach a certain curve type in the future. As stated, there are many factors that go into the planning and outcome of surgical treatment, all patients with a 53-degree primary curve are not automatically treated alike. They may have subtle differences that change their UIV or LIV or how straight their spine is after surgery. Sometimes, the surgeon will purposely ‘under-correct’ a curve so the shoulders and overall balance aren’t affected.

Here are some examples of studies that were presented at SRS meetings in 2017 that each looked at treatments done for patients with similar diagnoses. The researchers, who may also be surgeons, look at all patients from participating institutions, treated during a certain period of time and divide them into groups based on levels fused, type of procedure, etc. They analyze each group seeing if there are similarities in those that had successful outcomes versus those that had various problems.

  • Thoracic-Only Fusions for Double (Type 3) and Triple (Type 4) Major Curves in AIS at a Minimum 5 Year Follow-Up: Are They Possible and Durable?
  • Short Fusion Strategy Can Prevent Left Shoulder Elevation with Shorter Fusion Area in Lenke Type 1A Curves in Mid-term Follow Up
  • Risk Factors for Progression of Thoracolumbar/Lumbar Curve with Lumbar Modifier C and Low Back Pain in Non-Operated Patients with Adolescent Idiopathic Scoliosis: Mean 25-Year Follow-Up
  • Can We Stop the Long Fusion at L5 for Selected Adult Spinal Deformity Patients with Less Severe Disability, Superior Bone Quality, and Less Complex Deformity?
  • Correlation of the Lowest Level of Instrumentation to Functional Outcomes and Risk of Further Spine Surgery in AIS with Minimum 40 Year Follow-up

Doing this type of research and learning from past treatments, surgeons are continually looking for ways to improve spine surgery, to make it safer and to make it more successful for their patients.

There is so much to think about and consider when planning a surgery, and that is your surgeon’s job; your job is to get physically and mentally prepared for surgery and follow your postoperative instructions while maintaining a positive, ‘can do’ attitude, to make your recovery as smooth as possible.

When you see your surgeon for your pre-operative visit, casually use some of the ‘lingo’ and ask what your curve classification is or if your lumbar modifier is an A, B, or C. Ask if he/she has decided what your UIV and LIV will be and really surprise and impress them!


Glossary of Terms

A, B, C Modifier – the surgeon draws a vertical line on your x-ray to see where it falls on the vertebra in the center of the curve that is furthest from the center of you body.

Modifier A: the line falls pretty much in the center vertebra.
Modifier B: the line touches the edge of the vertebra.
Modifier C: the line does not touch the center vertebra at all.

Compensatory Curve – the curve above or below your main curve which is the largest curve.  Your automatically curves the opposite way to balance you so you don’t lean to the side. Sometimes those curves are very stiff and other times they are very flexible. The ones that are flexible and get much smaller on bending x-rays are compensatory curves and do not need to be fused.

Flexibility X-rays – x-rays done with you bending to each side, lying flat on your back, and with someone pushing on your back or pulling on your head and legs to stretch your curves – these are compared to your standing x-rays which show the largest curves. You can see on the x-rays how your curve changes with the different positions. These x-rays help the doctor determine which vertebrae need to be fused.

Fusion – during surgery, the doctor attaches instrumentation to your spine to act as an internal brace holding your spine in the corrected position while the bones become one solid piece of bone.

Kyphosis – the forward bend of your spine when viewed from the side.

Lumbar – the vertebrae in your low back. There are 5 lumbar vertebrae and they are called L1 through L5 starting under your ribs down to your pelvis.

Risser – a grading of how mature your body is to help your doctor estimate how much growth you have left which helps to guide your treatment. The line grows across the top of your pelvis and is referred to as Risser 1 thru 5. The lower the number, the more skeletally immature your body is and has the potential for greater curve progression.

Skeletally Immature – (see Risser)

Structural Curve – opposite of a compensatory curve. These curves are stiffer and are the main curve of your scoliosis. Structural curves need to be included in the fusion so they don’t continue to get bigger.

Thoracic – the vertebrae in your mid-back. They are connected to your ribs. You have 12 thoracic vertebrae referred to as T1 to T12 going from top to bottom of the thoracic spine.

Upper and Lower END Vertebrae (UEV, LEV) – the vertebrae at the top and bottom ends of your curve.

Upper and Lower INSTRUMENTED Vertebrae (UIV, LIV) – the vertebrae at the top and bottom of your surgery. The instrumentation can consist of rods, screws, hooks, or wires.

Vertebrae – the bones of your spine (plural). A single spine bone is called a vertebra (singular).