Back pain: Pathology review

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Case study0:00–0:58

At the urgent care clinic, three people came in with lower back pain. The first is Jeff, a 26-year-old, who says his pain began 5 hours ago after trying to lift a 300-pound weight off of the floor at his local gym.
He describes the pain as sharp and severe and says the pain goes down the back of his right leg and into his foot. Physical examination reveals a positive straight leg raise test on the right, and a diminished right Achilles tendon reflex.
Second is Beth, a 68-year-old, who says she slipped and fell while walking in her kitchen yesterday. Her history includes a wrist fracture from a little over a year ago.
Physical examination shows midline spinal tenderness to palpation. Finally, we have Harry, a 71-year-old male, who says his back pain has progressively worsened over the past month, keeping him up at night.
He also reports increased urinary frequency.Back pain is a very common complaint and one for which there are many potential causes.

Pathology0:58–1:38

It can originate from the spinal cord, nerve roots, the vertebral column, the surrounding muscles, and ligaments, or even extra-spinal structures, such as abdominal organs.
Therefore, the causes of back pain can be subdivided into mechanical causes, such as muscle strain, spinal osteoarthritis, disc herniation, spinal stenosis, vertebral fractures and osteoporosis; and non-mechanical causes, such as bone metastasis, seronegative spondyloarthritis, and vertebral osteomyelitis.First, let’s start with musculoskeletal causes.
The vast majority of cases of back pain are considered non-specific musculoskeletal pain due to strained muscles or ligaments.

Musculoskeletal causes1:38–2:18

These individuals have no sensory or motor deficits, and they typically complain about tenderness over the affected muscle or ligament.
The treatment for these individuals is prescribing activity as tolerated and NSAIDs for pain management. The next one is spinal osteoarthritis, which can be due to the natural aging process where the cartilage at the tips of bones wear down over their lifetime.
It is associated with joint degeneration, ligamentous changes, disc degeneration, and finally, deformity of the spine. Next we have disk herniation.

Disc herniation2:18–5:05

Now, the spine is made up of bony vertebrae separated by intervertebral disks that act like cushions to absorb shock. The intervertebral discs consist of a thick, tough, fibrous outer ring called the annulus fibrosus surrounding a soft gelatinous core called the nucleus pulposus.
In disk herniation, the nucleus pulposus bulges outward, almost always posteriorly, since the posterior longitudinal ligament is relatively thin compared to the wide anterior longitudinal ligament..
This is most often caused by an individual doing some heavy lifting, and while any disk in the spine can herniate, a high yield fact to know is that it is almost always one of two disks in the lumbosacral region that herniates, the L4-L5 disk or the L5-S1 disk.
But, on rare occasions, the disk between L3-L4 vertebrae can also herniate. Regardless of the disc that herniates, the nerve that is affected is typically below the level of herniation.
A key symptom for L4-5 and S1-3 disc herniations is sciatica, or a shocking pain that shoots down from the buttocks through the leg, following the course of the sciatic nerve.
In L4 radiculopathy, where the disk between L3-L4 herniates, there’s also motor deficits like weakness in knee extension and reduced patellar reflex.
On the other hand, if the L4-L5 disk herniates, it can result in L5 radiculopathy. The motor deficits include weakened hip abduction and foot dorsiflexion.
Another high yield point that you have to know for your exam is that individuals with L4 or L5 radiculopathy have difficulty in heel walking!
Finally, if the L5-S1 disk herniates, it can lead to S1 radiculopathy. Motor deficit includes weakened foot plantar flexion and a diminished Achilles tendon reflex.
Finally, remember that individuals with S1 radiculopathy have difficulty in toe walking. A common test used in diagnosing lumbar disk herniation is the straight leg raise test, or SLR, where a person laying on their back keeps their legs straight and then raise them one at a time between 30 and 60 degrees.
If they experience pain radiating down their leg, the test is considered positive, suggesting lumbar disk herniation. An MRI of the spine can confirm the diagnosis.
First-line treatment for disk herniation is usually conservative and involves rest with activity as tolerated, and NSAIDs to manage pain.
If that fails to manage pain, corticosteroids may be used. If symptoms persist or worsen beyond 6 weeks, treatment may involve surgical removal of part, or all of the disk.
Now, it’s important to note that herniated disk can compress spinal roots below the L2 and cause cauda equina syndrome! Besides disc herniation, trauma and tumors can also cause this syndrome, which is characterized by back pain, radiculopathy, loss of bladder and sphincter control, and sexual dysfunction.

Cauda equina syndrome5:05–6:06

For your exam, you have to know that cauda equina syndrome is associated with saddle anesthesia, which is a loss of sensation in the areas that touch the saddle when you ride a horse.
This includes the buttocks, inner surface of the thigh and perineum. Also, one or both legs can be impaired by muscle weakness, loss of knee and ankle reflexes, and even paraplegia.
A high yield fact to remember is that individuals with cauda equina syndrome require immediate surgical decompression via laminectomy to prevent permanent nerve damage.
In addition, they can receive high doses of steroids to relieve the pain and reduce edema, while waiting for the surgical intervention.
Next is spinal stenosis, which refers to the narrowing of the spinal canal or intervertebral foramen, through which the spinal cord and spinal nerves pass, respectively.

Spinal stenosis6:06–8:10

Natural wear and tear or degeneration of the spine over time is the most common cause of spinal stenosis. Over time, osteophytes, or bone spurs, can form, and the ligamentum flavum can also grow excessively.
All of these factors contribute to narrowing the spinal canal and intervertebral foramen, increasing joint stress, causing pain.
Since the causative factors develop over time, it is typically found in individuals over the age of 60. The high yield hallmark feature of spinal stenosis is neurogenic claudication, which refers to the pain being exacerbated by walking or standing upright and relieved by sitting or bending forward.
This is because walking or standing upright narrows the spinal canal and intervertebral foramen while bending or leaning forward widens the spinal canal and intervertebral foramen.
Pain relief when bending forward is often referred to as the “shopping cart sign” because individuals typically bend forward when pushing a shopping carts and this offers symptom relief.
Key symptoms include back pain which is usually the chief complaint. There could also be neurologic symptoms such as lower extremity numbness, tingling, or weakness if the stenosis results in compression of the spinal cord or nerve roots.
Just like with disc herniation, sciatica can also be present if nerve roots in the lumbar and sacral regions are compressed.
Diagnosis typically involves a suggestive history, followed by a neurological exam and an MRI to confirm the diagnosis. Treatment is mostly conservative, involving physical therapy and pain management with NSAIDs or epidural steroid injections in some cases.
In rare cases where spinal stenosis leads to compression of the spinal cord or spinal nerves producing neurologic deficits, such as those in cauda equina syndrome, decompression surgery may be required.Next up are vertebral fractures, which are usually caused by major trauma that can lead to spinal cord lesion and eventual neural deficit.

Vertebral fractures8:10–9:38

But, for your exam you have to know that vertebral fractures can also be asymptomatic, and in that case you should think of compression fractures.
A compression fracture is a subtype of vertebral fractures that is most commonly seen in individuals with osteoporosis. This is because individuals with osteoporosis, typically older, post-menopausal women, have bones that are less dense, making them more susceptible to fractures.
In the spine, the body of each vertebra losing density over time decreases their ability to withstand pressure that may occur even with normal movement, such as bending over, and fractures can develop.
But it’s important to note that minor trauma such as slipping and falling can also result in a compression fracture. Vertebral fractures can lead to kyphosis, or outward bending of the spine, and loss of height.
It is usually after some minor trauma that an individual with a compression fracture will present with localized back pain.
Diagnosis is dependent on a suggestive history followed by a physical exam looking for localized midline spine tenderness and an X-ray of the spine to confirm.
Treatment is often conservative, involving bracing, pain management, and managing the underlying osteoporosis. In rare cases in which pain persists beyond 6 weeks or if the fracture produces neurologic deficits, surgery may be indicated.Let’s move on to back pain that is related to cancer, which is most commonly caused by bone metastases!

Bone metastases9:38–11:08

For your exam you have to know that cancers that commonly spread to the axial skeleton include prostate and breast cancers, then kidney, thyroid, and lung cancers.
Another high-yield cause is multiple myeloma, which stands for the neoplastic proliferation of plasma cells within the bone marrow which is most commonly seen in individuals over 60 years of age.
When you think of multiple myeloma, think of mnemonic “CRAB”, where C stands for hyperCalcemia, R for Renal involvement, A for Anemia, and B for Bone lytic lesions and Back pain.
A tumor in the spine can grow and push up against the spinal cord, thereby causing spinal cord compression which can lead to neurological symptoms and even permanent loss of neurologic function.
The main symptom is often back pain that comes on gradually, progressively worsens, and is worst at night. The pain can be accompanied by constitutional symptoms such as night sweats, fever, chills, fatigue, malaise, or unintentional weight loss.
Neurologic symptoms can include lower extremity weakness, numbness, bladder or bowel dysfunction, or even paralysis in severe cases.
Diagnosis often involves an MRI, or CT instead in patients where an MRI is contraindicated. If the primary cancer is located, a biopsy is needed to identify the causative cancer, so treatment can begin.
Next, we have seronegative spondyloarthropathies, which include inflammatory conditions that affect the vertebral column.

Seronegative spondyloart11:08–12:34

These disorders are called “seronegative” because there’s an absence of rheumatoid factor, or RF, which is most commonly found in rheumatoid arthritis.
They also have a strong association with HLA-B27, which is an MHC I class molecule. For your exam, you have to know that seronegative spondyloarthropathies more commonly affect men, usually before the age of 45.
Another high yield point is that these individuals typically complain about slowly progressive lower back pain, especially around the sacroiliac joints.
The pain is worse at night and there’s also morning stiffness that lasts more than 30 minutes and improves with movement and exercise.
Besides back pain, individuals with seronegative spondyloarthropathies can also present with peripheral arthritis; enthesitis, which is an inflammation of the sites where tendons and ligaments insert into the bone; uveitis, which is an inflammation of the uvea; and dactylitis, which is the inflammation of the fingers, also known as sausage fingers.
Now there are several subtypes of seronegative spondyloarthropathies and you can remember them by a mnemonic PAIR, where P stands for arthritis; A for Ankylosing spondylitis; I for Inflammatory bowel disease; and R for Reactive arthritis.
First, let’s start with psoriatic arthritis which occurs in individuals with psoriasis. It is characterized by an asymmetric inflammation of the joints, primarily on the hands and feet, but also spine.

Psoriatic arthritis12:34–13:07

For your exam, it’s important to note that less than 30% of individuals with psoriasis develop psoriatic arthritis. These individuals typically present with dactylitis and “pencil-in-cup” deformity on x-ray.
“Pencil-in-cup” deformity occurs due to resorption of the terminal phalanges.With ankylosing spondylitis, there’s a chronic symmetrical inflammation of the spine and sacroiliac joints that can lead to partial or even complete fusion of joints, or ankylosis.

Ankylosing spondylitis13:07–14:06

Now ankylosing spondylitis is more commonly found in males and for your exam, you have to know that these individuals can present with extra-articular features such as unilateral anterior uveitis, which occurs in 25% of individuals with ankylosing spondylitis; aortic regurgitation; and restrictive pulmonary disease due to costovertebral and costosternal ankylosis.
Moreover, to assess the severity of the condition, it’s crucial to monitor the chest wall expansion. X-ray features include ankylosis of sacroiliac joints, ankylosis of the intervertebral joints, and “bamboo spine”.
Bamboo spine occurs as a result of vertebral body fusion by marginal syndesmophytes, which are bony growths within the ligaments of the spine.The last one is reactive arthritis, which was formerly known as Reiter syndrome.
This is an autoimmune condition that typically affects young men. It occurs after a bacterial infection of the gastrointestinal or urinary tract and the most common microorganisms that are associated with reactive arthritis include Shigella, Yersinia, Chlamydia, Campylobacter, and Salmonella.

Reactive arthritis14:06–14:57

Remember that these organisms are not invading into the joints and the inflammation is autoimmune in nature. An easy way to remember them is to think of the mnemonic ‘SHY chiCS’.
The classic triad seen in individuals with reactive arthritis consists of conjunctivitis, urethritis, and arthritis. So, for your exam remember that these individuals can’t see, can’t pee, and can’t climb a tree.
And now, finally we move on to osteomyelitis. So this is not an autoimmune disorder and the microorganisms are actually invading the bones causing damage.

Osteomyelitis14:57–16:21

If bacteria spread from a distant site through the bloodstream to vertebrae, then it’s called vertebral osteomyelitis. This usually affects two adjacent vertebrae and the intervertebral disk between them.
Now for your exam, you have to know that the most common causes of vertebral osteomyelitis are Staphylococcus Aureus and Mycobacterium Tuberculosis.
Moreover, vertebral osteomyelitis caused by Mycobacterium Tuberculosis is also referred to as Pott disease. Individuals with vertebral osteomyelitis typically complain about back pain, fever, and night sweats and it’s easy to confuse this with metastasis to the spine.
Laboratory findings, such as elevated erythrocyte sedimentation rate, or ESR, and C-reactive protein, or CRP, are sensitive, but not specific enough; therefore we have to use imaging methods, such as X-ray and MRI.
X-ray is insensitive in acute osteomyelitis, but it can be useful in the diagnosis of chronic osteomyelitis; while MRI stands for the best imaging method for detecting acute infection and precise detection of affected vertebrae.
Alright, as a quick recap. Back pain is a very common complaint and one for which there are many potential causes.
It can originate from the spinal cord, nerve roots, the vertebral column, the surrounding muscles, and ligaments. Therefore, the causes of back pain can be subdivided into mechanical causes, such as muscle strain, spinal osteoarthritis, disc herniation, spinal stenosis, vertebral fractures and osteoporosis; and non-mechanical causes, such as bone metastasis, seronegative spondyloarthritis, and vertebral osteomyelitis.Now, back to our patients!

Review16:21–16:58

Jeff has sharp low back pain radiating down his leg and into his foot, so this is a case of sciatica. The symptoms started after he attempted to lift something heavy and due to his young age, the most likely diagnosis is lumbar disk herniation.

Summary16:58–18:10

The positive straight leg test also suggest this. The diminished Achilles tendon reflex pointing specifically to L5-S1 disk herniation.
An MRI of his spine can confirm the diagnosis. Beth’s age, sex, past history of a wrist fracture all points to osteoporosis.
The recent minor trauma from the fall that resulted in her current complaint of back pain is most likely due to osteoporotic vertebral compression fracture.
The physical exam demonstrated midline spine tenderness localized to L4, and X-ray confirmed the diagnosis. Harry’s age, sex, and description of progressively worsening back pain that is keeping him up at night, coupled with the urinary change of increased frequency suggest prostate cancer that has metastasized to his spine.
An MRI reveals blastic lesions to his lumbar spine, and labs reveal increased levels of prostate specific antigen and alkaline phosphatase.
is keeping him up at night. Coupled with the urinary change of increased frequency, suggest prostate cancer that has metastasized to his spine.
An MRI revealed blastic. Lesions to his lumbar spine, and Labs reveal increased levels of prostate-specific,