Exam Series: Guide to the Back Exam

A 67-year-old male presents to your emergency room with back pain. He has a history of intermittent back pain that typically responds to NSAIDs, however this particular episode has been much more severe. He now feels sharp pain that radiates into this left foot with certain movements, which causes weakness when walking. His past medical history is significant for a right hemicolectomy, hypertension, type II diabetes, and smoking. He has no history of IV drug use and has no infectious symptoms.

Background

Back pain is one of the most common presentations in the emergency department. The majority of these cases are musculosketal in nature, potentially involving a muscle sprain, ligament strain, or compression of nerve roots, although a specific diagnosis cannot be made is an estimated 85% of patients¹. True back pain emergencies, namely cauda equina syndrome, epidural abscess, and malignancy, are rare but require immediate intervention in order to preserve neurologic function. Additionally, there are several emergent pathologies that can present as secondary causes of back pain including aortic dissection, AAA, and PE. Thus, an approach to back pain centers on prompt recognition of true emergencies.

Anatomy of the Vertebral Column¹

The vertebral column provides structure to the back, serving as an attachment point for paraspinal muscles and providing protection to the spinal canal. The 12 thoracic vertebrae, 5 lumbar vertebrae, and 5 fused vertebrae in both the sacrum and coccyx articulate at facet joints and intervertebral discs. The posterior longitudinal ligament and anterior longitudinal ligament limit flexion and extension of the spine, while the intertransverse ligament provides support to the transverse processes.  The spinal column runs until L1-L2, after which it splits into the cauda equina.  Cervical nerve roots exit above the corresponding vertebrae, while thoracic and lumbar nerve roots exit below the corresponding vertebrae.

Approach to the History

The history and physical examination are essential in the evaluation of back pain. Most investigations are only indicated once there is a suspicion of a back pain emergency, therefore a thorough clinical evaluation is needed to identify patients at risk. In particular, “red flags” on history can point to an emergent pathology.

1. History of Presenting Illness: Characterize the pain as acute (<6 weeks) or chronic (>6 weeks). Pain that has not improved despite treatment is a concerning symptom. A history of trauma increases the risk of fracture especially in the context of an elderly patient or a history of steroid use.
2. Patient characteristics: Cancer and fragility fractures should be considered in elderly patients with back pain. Cancer should also be considered in pediatric patients, along with congenital abnormalities of the spine and infection.
3. Pain characteristics: Identify the onset, location, quality, radiation, severity, and duration of the pain. Back pain presents as primarily back dominant (likely due from muscular or vertebral disease without nerve root involvement) or leg dominant (likely due from disc herniation or nerve root impingement). Benign back pain is typically dull, achy, and non-specific that worsens with movement and improves with rest. Pain that is associated with sensory changes, weakness, falls, and gait instability suggest neurologic pain. Typically pain that is progressive, unrelenting and unrelieved by rest is suspicious for a more serious cause of back pain including malignancy, infection or fracture.
4. Associated symptoms: Bladder and bowel dysfunction including urinary retention with overflow incontinence, or fecal incontinence and/or saddle parasthesias or sensory loss suggests cauda equina. Infectious symptoms (fever, chills) and constitutional symptoms (fatigue, weight loss, night sweats) may suggest infectious, neoplastic, or rheumatologic disease.
5. Review of symptoms: There are several can’t-miss emergencies that mimic back pain including aortic dissection, MI, AAA, PE, retroperitoneal bleed, pancreatitis, and ruptured ectopic. It is essential to assess for any cardiac and respiratory symptoms.
6. Past Medical History: 5-30%² of patients with known cancer eventually develop spinal metastasis. A history of IV drug use increases the risk of epidural abscess, discitis and osteomyelitis as hematogenous spread of bacteria is the most common source. Immunosuppression also increases the risk of spinal infection.
7. Medications: Anticoagulants increase the risk of an epidural hematoma. Prolonged glucocorticoid increase the risk of fragility fractures.

In summary, red flags for neurologically significant back pain include bladder and bowel dysfunction, saddle anesthesia, neurologic deficits (esp. if bilateral), constitutional symptoms, and infectious symptoms. Patient characteristics including age >50, history of IV drug use, history of cancer, and back pain that has not improved despite treatment are other red flags.

Approach to the Physical Examination – “Look, Feel, Move”

Begin with a general assessment of a patient and their vital signs. A screening cardiovascular, respiratory, and abdominal examination is warranted to rule out extrinsic life-threatening etiologies of back pain. A pulsatile abdominal mass felt with palpation or visible on ultrasound is concerning for a AAA. Flank pain and CVA tenderness may indicate renal pathology.

1. Inspection: Examine the patient’s posture. Asymmetry in the shoulder height may indicate scoliosis, which becomes more pronounced during the Adam’s Forward Bend test where the patient bends forward at the hips with straight legs. A lateral view of the back reveals the four natural curves of the spine – cervical lordosis, thoracic kyphosis, lumbar lordosis, and coccygeal kyphosis. Examine the paraspinal muscles for swelling, atrophy, erythema, or other signs of infection.
2. Palpation: Palpate the paraspinal muscles for atrophy, tension, and pain. Palpate the spinal column for any step deformities and point tenderness. Pain with percussion is a sign of infection or fracture. Bony landmarks include:
   • C7: bony prominence at the base of the neck
   • T3: level at the spine of the scapula
   • T7: level at the angle of the scapula
   • L3-L4: iliac crests
   • S2: iliac spine
3. Range of Motion: Assess for flexion, extension, lateral flexion (ear to shoulder) and rotation of the cervical spine. Assess for flexion, extension, and lateral flexion (fingers should touch the fibula) of the back, ensuring that the patient keeps their leg straight and recognizing that tight hamstrings may limit range of motion. Rotation is best assessed with the patient seated in order to isolate movement of the back from the hips. A power examination of the back is not necessary.
4. GI/GU exam: A digital rectal exam is required to assess tone if there are any concerns for cauda equina. A post void scan for residual urine should also be ordered as urinary retention is the most common signs of cord compression.
5. Special Tests:

Videos of the special tests from Physiotutors are linked below:

Sciatica:

• Straight Leg Raise: Passive lift the patient’s straight leg. A positive test occurs when pain radiates down the leg into the foot between 30-70°. The test can also be replicated with the patient in a seated position.
• Cross Straight Leg Raise: A positive test occurs when pain is elicited in the symptomatic leg when the asymptomatic leg is raised. This test has higher specificity but lower sensitivity compared to the straight leg raise.

Clinical Utility of Special Tests in the Lumbar Spine Exam³

Femoral Nerve Root Irritation:

• Femoral stretch test: Position the patient prone and have them flex one knee to 90°. Grasp the patient’s ankle and extend the hip; radicular pain in the thigh suggests femoral nerve root irritation.

Sacroiliac Joint Pain

• FAbER: Position the patient in a supine figure-of-four position – Flex, Abduct, and Externally Rotate one hip – placing the foot on the opposite knee. Push down on the outstretched knee while stabilizing the opposite pelvis. Pain and decreased movement of the test leg suggests sacroiliac joint pain.
• Gaenslen’s: Allow the patient to hang one leg off of the bed while lying supine, then instruct them to bring the other knee to their chest. Pain in the buttock is indicative of SI joint pain.

6. Neurovascular exam: It is essential to check for any neurologic weakness as a sign of serious back pathology. Power should be tested in the lower extremities to investigate any weakness. A gait exam can also be used to assess for weakness and instability. Exams should be repeated to monitor for any rapidly progressing symptoms. Nerve symptoms that are bilateral and span multiple levels are concerning for a spinal lesion that compresses multiple roots.

Neurologic examination⁴

Investigations

X-rays are not required in the workup of uncomplicated back pain in an absence of red flags. There is no difference in outcomes in pain or function for people who receive an X-ray compared to those who go without^5,6.More than 50% of asymptomatic patients may have pathology such as a disc bulge that is seen on MRI but is clinically silent. Therefore, imaging does not necessarily correlate with symptoms and radiologic findings may not be pathologic⁷.

X-rays should be ordered in a patient with an age >50, chronic steroid use, or a history of trauma as these increase the risk of a fracture. The diagnosis of a fragility fracture is important in order to initiate appropriate therapy as an outpatient that protects from future fractures. Fewer than 20% of women and 10% of men with fragility fractures receive intervention that decreases future morbidity and mortality, in contrast to the medical management provided to almost all patients diagnosed with ACS⁸.

X-rays plus a CRP or ESR are appropriate initial investigations in a patient with a concerning history but without evidence of cord compression, including patients with known cancer, a history of IV drug use, rheumatologic disorder, or suspected infection (epidural abscess, vertebral osteomyelitis or discitis)⁹. AP and lateral views of the back are sufficient, as oblique views increase radiation exposure without a corresponding benefit to the patient. Patients with severe and complicated fractures may benefit from a CT to enhance details of the vertebrae.

MRI is indicated in cases of suspected cauda equina. Urinary retention has a sensitivity of 90% and a negative predictive value of 99.99% for cauda equine¹⁰. Post void residual can be measured on bladder scan or with bedside ultrasound using the formula volume = 0.52 x bladder height in cm x width x depth.

A systemic workup may be indicated if there is a high likelihood of an extrinsic cause of back pain. Investigations could include an abdominal ultrasound to rule out AAA, urinalysis for UTI and pyelonephritis, or beta hCG

Putting it all together

The combination of the history, physical, and ancillary test results can help to guide your assessment:

Management

Patients with muscular back pain should be encouraged to return to activities and avoid bed rest. Conservative pain management strategies including heat, massage, and acupuncture may have mild to moderate benefit and are safe to use in all patients. Referrals to physiotherapy may also be used to encourage functional gains. NSAIDs have been shown to improve pain and function, although caution should be used in patients at risk for GI bleeding and with kidney dysfunction. Tylenol may be a better choice for these patients, though there is no evidence that it improves pain when compared to placebo. Muscle relaxants (including benzodiazepines, baclofen, cyclobenzaprine) may have some benefit but have several side effects including sedation¹⁰. Opioids should not be used for the initial management of acute back pain¹⁴.

Compression of the spinal cord or cauda equina requires urgent neurosurgical consultation and intervention.

Back to the Case  

The history of this patient makes you suspicious for a cancer metastasis. You order a CRP and two views of the spine, which were all normal. Physical examination reveals a positive straight leg raise. Power is normal in the lower extremities, and you determine that his subjective weakness is secondary to pain rather than true neurological weakness. There are no red flags for cord compression on history or physical examination, and his post-void residual is normal. After ruling out all of the back pain emergencies you diagnosis sciatica, prescribe a short course of anti-inflammatories and encourage physiotherapy for strengthening. You advise the patient to return to the emergency department if he develops new symptoms or red flags and to follow-up with his family physician for reassessment and ongoing management.

Good Resources

• Rheumtutor: MSK Clinical Skills Manuals and Instructional Videos
• Orthobullets: Quick reference orthopedic information
• Physiotutor: Youtube videos for clinical assessment

References

Reviewing with the Staff

Low back pain is one of the most common Emergency Department presentations, it is rare to go a shift without encountering at least a couple of patients with the chief complaint of back pain. Most these patients will have a benign cause for their pain (about 90%). To identify the patients that have life threatening causes of back pain (i.e. infectious causes, malignancy, vascular emergencies etc..), it is important to have a high index of suspicion for the life or limb threatening causes of back pain combined with a focused history and physical examination in order to identify “red flags” that may indicate serious pathology. Any red flags should prompt further investigation. In the absence of red flags Choosing Wisely Canada recommends against imaging for back pain as it is unlikely to change management and also advises against the use of opioids as first line treatment for uncomplicated mechanical back pain. Consider NSAIDs for patients without contraindications and non-pharmacological treatments including heat as well as education on the role of rest and exercise. I generally tell patients with acute mechanical low back pain to avoid both strenuous or aggravating activities as well as prolonged rest which may worsen symptoms. If you’ve decided your patient is ready for discharge always educate them on the “red flags” that should prompt their return to the emergency department and remind the patient to arrange for follow-up with their family physician for persistent or ongoing symptoms.

Dr. Jennifer Thompson

Assistant Professor, McMaster University, Department of Emergency Medicine

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Kathryn Chan

Dr. Kathryn Chan is an emergency medicine resident at McMaster University and a former biomedical engineer. Her interests include medical technologies, systems thinking, and social determinants of health.

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