Dr. David Chang on Discovery

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ContributorDr. David Chang, M.D.Read Full Bio

Biography

Dr. David Chang is a board certified orthopedic spine surgeon who specializes in surgical treatment of spinal disorders. He has worked and studied in both coasts of the country. After graduating from Princeton University, he received his medical degree from New York University. He completed his orthopedic surgical training at NYU-Hospital for Joint Diseases. He completed an advanced fellowship in orthopedic spinal surgery with Drs. Robert Watkins and Lytton Williams. With his training under Dr. Watkins, Dr. Chang understands the complexities of sports related spinal injuries. Additionally, Dr. Chang’s interest lies in minimally invasive spinal surgery, artificial disc replacement technology and degenerative disorders of the cervical and lumbar spine. Dr. Chang is part of the Watkins Spine Group that works in association with the Marina Del Rey Hospital in the Southern California area.

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ContributorDr. David Chang, M.D.Read Full Bio

Biography

Dr. David Chang is a board certified orthopedic spine surgeon who specializes in surgical treatment of spinal disorders. He has worked and studied in both coasts of the country. After graduating from Princeton University, he received his medical degree from New York University. He completed his orthopedic surgical training at NYU-Hospital for Joint Diseases. He completed an advanced fellowship in orthopedic spinal surgery with Drs. Robert Watkins and Lytton Williams. With his training under Dr. Watkins, Dr. Chang understands the complexities of sports related spinal injuries. Additionally, Dr. Chang’s interest lies in minimally invasive spinal surgery, artificial disc replacement technology and degenerative disorders of the cervical and lumbar spine. Dr. Chang is part of the Watkins Spine Group that works in association with the Marina Del Rey Hospital in the Southern California area.

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I'm Dr. David Chang, um, a board certified orthopedic surgeon. I went to school at Princeton University for undergraduate education then I went to NYU School of Medicine. After that I did a five-year orthopedic residency at the NYU School of Medicine and Hospital for Joint Diseases. Then I did a Spine Fellowship with Dr. Watkins out here in Los Angeles. Back pain is multifactorial in ideology. I mean obviously there's gonna be some anatomic structures that could be the epicenter of that back pain. Could it be the disc, could it be the facet joints, could it be nerve issues, could be just muscular aches. But, what leads to it? Is it going to be psychosocial factors? Just stresses, emotional stresses from job, emotional stresses from your family life. Is it going to be real physical work be it working around the house or your physical job, labor-type job.

So, those are some of the things that just kind of come to my head, whenever I'm examining patients. What are the other things that might be affecting the patient as it relates to back pain? So this is the model of the spine and it's pretty life size. I talk about the spine as a multisegmented structure not much different than a centipede if you will, a lot of repetitive parts. People always refer to the disc, it's one of the largest structures here that we might be able to see but I refer to the spine in motion segments. So let's take this segment here, and then this would be the L5 bone, L4 bone, L3 bone, L2 bone, and L1 bone. L stands for lumbar.

And if we take this motion segment at L2-3, it comprises the L-2 bone and the L-3 bone as well as an intervening disc, which would be the L2-3 disc. If we say a singular number, it's usually referring to a bone or a singular nerve root if we say L2-3 it's usually referring to the motion segment, the disc segment, or the structures back here that my fingers are pointing to those are the facet joints. And, you might be able to see one bone rub and articulate with the bone below at that joint. Coming back to that motion segment concept, there's two bones, one disc, and two adjacent facet joints.

And in that motion segment, there's usually gonna be two nerves that could be potentially irritated. There's gonna be 15 joints in the spine. Five disc joints and then two paired facet joints so that's 10 joints and any one of those can break down, and once one breaks down, then that starts putting abnormal stresses on the other . So we'll talk about degenerative disc disease. And I think that is a, for a lack of better term, dump truck category or term that encompasses many spectrums of degeneration within the disc or the spinal motion segments. The disc is a shock absorber, think of it as a sponge. Maybe the disc is drying out, right? Maybe there's just small tears within the disc, we call them annular tears and that's on the mild side.

Then somewhere in the middle, there are disc herniations, or disc bulges. They're clearly disruptions within the disc, more than just mild dehydration. And then, on the right side of the spectrum, there's real frank degeneration in the disc, where the disc material is really dehydrated, it's starting to crack and fissure, maybe the disc space is collapsing. I think people often hear herniated disc or a bulging disc or disc protrusion, for the non spine specialist, they sort of blend together.

Clearly, disc herniations and disc bulges are going to be disruptions of the disc material. Some element of that disc material is going to be sticking out beyond the normal boundaries of that disc or that circle. If it's sticking out beyond the normal boundaries, it might be compressing some of these nerve roots that are passing by or traversing that specific disc. For a disc herniation, for me, it's very specific. It's sort of like crab meat, it's firm but soft. It's not as firm or hard as bone material but it is harder than the more pliable nerve structures.

So if that crab meat-like structure, or disc material is pushing on the nerve, it's gonna physically win that battle and compress that nerve and irritate that nerve. So a disc herniation is when you've got that crab meat-like material extruded out beyond the normal boundaries of the disc and it's pushing on a specific nerve root and oftentime what manifests from there is the radiating leg pain. Patients might refer to it as sciatica type pain. The disc bulge, again, still a disruption to the disc.

I liken it to a situation where if you took a small dough ball and you just started compressing it, well it's gonna start pancaking out in sort of a horizontal plane, sort of non specifically and sort of generically, very broad based and when I see a disc bulge on an MRI, clearly I'll see a structural change in the shape of the disc material. Maybe I'll see a little bit of nerve compression, but it seems somewhat symmetric right versus left. I reserve that sort of structural and clinical picture for a disc protrusion or a disc bulge or a bulging disc.

Other terms you might hear are slipped disc, and the disc is not actually slipped but it's unstable to the extent that in that concept of the motion segment where you have one bone, one disc and another bone below it, the top bone is slipped forward relative to the bone below and medically that's called a spondylolisthesis. If you look at it from a side profile, the back edge of each one of these bones has to flow nicely in a smooth, curved line, right? But in a model where there is a slipped disc, this bone is gonna be slipped forward and so the back edge of this bone, if you can imagine, it would have sort of a staircase or a stepped off pattern to flow into the back edge of the bone below it.

So, when patients come into my office and they tell me what their chief complaint is, I want to know what's bothering them, how long has it been bothering them, and then beyond that, how is that affecting them. And I also ask them point blank, what do they expect from me? How do they envision me helping them? Oftentimes we'll get x-rays, that's the first test, it's a great test. It's a sort of a surveillance type exam, it'll show the bones of the spine, it'll show the alignment of the spine, it'll show sort of the curvature if patients have scoliosis. So, it's like looking at the forest from a distance.

Then there are other types of tests that are really trying to look at the branches and the leaves of those trees of the forest. The MRI allows us to actually look at the composition of that disc material, see if it's dehydrated or it's not dehydrated, see if there are actually any disc bulges or disc protrusions or disc herniations that might be pushing pressure on the nerves. We might be able to see other structures like cysts, that could also be coming from a facet joint that could be putting pressure on the nerve roots. CT scan as a modality is great to look at the bony st-architecture. I can talk about cracks in the bones or broken bones, it can highlight bone spurs coming off the facet joints or the disc joints.


There are other types of CT scans where in addition to the CT scan imaging you're also gonna do a myelogram. And a myelogram is gonna be what people think of as a spinal tap. A radiologist has to put a needle into your back and we'll inject some dye. That dye is a radiopaque dye which will be seen on the CT scan and the purpose of that is that dye is going to illuminate the nerves that wouldn't otherwise be seen, or readily seen on a CT scan.

Now we can see the nerves, juxtaposed to the bones with real good image quality. Oftentimes we're not using contrast imaging of an MRI or a CT scan unless maybe it's a revision case or a more complicated case we think there might be some tumor involved or something like that. There's one more test called the bone scan and the bone scan is not sort of the bone scan that primary medical doctors to evaluate for osteoporosis, this is a bone scan specifically called a SPECT scan and it stands for single photon emission computed tomography and it helps evaluate where the bone cells are going in your body.

And to just to kind of quick sort of overlay of it is we'll inject you with a very small amount of radioactive substance and it's just a marker and that marker will light up bone or tag and label bone cells. It's sort of like Lojack for a car, the car gets taken, gets going to another place and we're able to find out where it goes. And so similarly with the SPECT scan, your brain's gonna tell those bone cells to go someplace, maybe they're gonna go to a degenerated hot joint, maybe the facet joint, maybe the disc joint. And if the bone scan picks up on that we'll have a bright red spot or a hot spot at that one particular joint level and that helps us, as spine surgeons narrow down where your pain generator is.

And if that bone scan or SPECT scan comes back positive then that leads up to recommend surgery with a little more certainty and it raises our probability that surgery's actually gonna help you in the context of that particular disc causing your pain and maybe doing a fusion surgery to address it.

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