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Mechanical Back Pain

Updated: Aug 13, 2021

Focused Physical Examination


1:05 Introduction

Low back pain can be caused by a myriad of different etiologies, and consequently, the examination can take on a variety of different forms. The approach that will be discussed here is best applied when the history is suggestive of a musculoskeletal etiology. If you suspect a visceral or vascular origin of the pain, then an altogether different exam will be required.


The purpose of this video is to guide you on how to do a focused lower back exam. This is not a cumulation of all back exam techniques, which would be very timing consuming and cumbersome. Instead, the aim is to verify findings that have been discovered in the history and to adequately screen for red flags, without rushing yourself or the patient. Pending findings discovered in the history, a more detailed examination may be indicated, requiring that you tailor your strategy for each patient. But for the most part, a straightforward screening examine will suffice.


You may wish to begin with a simple introduction. Introducing yourself and getting to know the patient. There are many ways in which you can do this, from brief and simple greetings to more elaborate introductions. Next you require consent from the patient in order to perform the examination. Inform them of your intentions, what you will be doing, and let the patient know that they may stop you at any moment. Now is also an opportune moment to wash or sanitize your hands if you have not done so already, and to ensure that the patient is properly positioned and draped. The entire back should be exposed for complete inspection.


1:38 Vital Signs

While taking an OSCE exam, if the vital signs haven’t been provided, this is a good moment to ask for them.


1:49 Inspection

Continue with general inspection from the back, and then from the side. On the back inspect for any swelling, discolorations or scars, hairy patches, deformities, asymmetry, or muscular atrophy. While inspecting from the side assess the contour of the back, noting any significant deviation from the normal spinal curvature, such as excessive thoracic kyphosis or the lack of lumbar lordosis (i.e., flattening of the lumbar spine).

To start with, I’m just going to examine you from right here. Next, I’m going to need you to stand up for me. But before you do, can you tell me if you need any help? Now I’m going to take a look at your back from behind you and then from the side.

3:00 Gait

Now examine the patient’s gait. Ask them to walk to the end of the room and back. Pay attention to the gait cycle, range of movement, and turning ability. Make note of any difficulties that the patient has, and any specific gait abnormalities displayed. It’s not always necessary heel and toe walking, but significant weakness of the muscles innervated by L4-L5 can be screened for with heel walking, while toe walking screens for significant muscle weakness in the S1 distribution.


If you detect a Trendelenburg gait, then you may wish to elicit the Trendelenburg sign. To do so, stand behind the patient and place your hands on their iliac crests. Then ask the patient to stand on one foot at a time. Normally, the iliac crests will remain level. But with hip abductor weakness, there will be a drop on the side of the non-weight-bearing hip. The Trendelenburg sign indicates dysfunction of the hip abductors, usually due to gluteus muscle weakness which can be due to superior gluteal nerve damage or an L5 radiculopathy.

Next I’m going to stand behind you and place my hands on your hips. Is that alright with you? Can you stand on one foot? And now on the other?

3:57 Palpation

Next comes palpation. While observing the patient’s face, palpate the bony prominences of the spinous processes along the midline of the spine; feel for step-offs and other gross deformities, and watch for facial grimacing as a sign of tenderness. For reference, the L4 to L5 vertebral space usually occurs at the level of the intercristal line, which is an imaginary line that connects superior aspect of the iliac crests posteriorly. Next, palpate lateral to the midline to assess the paraspinal muscles for tenderness, muscle spasm, asymmetry, or other deformity. Lastly, press on the sacroiliac joints.

Now I need to press along your back, going from the upper part to the lower. Please let me know if you feel any pain.

4:34 Range of Motion

If possible, assess active flexion and extension of the back. While assessing range of motion, position yourself close enough to the patient in order to provide support if necessary. During back extension, you may offer to place your hand on the patient’s lower back in order to help keep them steady. Pay particular attention to if the pain is worse with flexion and improves with extension, and vice versa. Make note of any restrictions in movement, as well as the fluidity to which the patient manages these movements. If you suspect an inflammatory spinal condition, then it may be prudent to perform a Schober test and to assess for chest expansion.

What I would like to do now is see how well you can bend forward, and then backward. Would you be able to try to touch your toes without bending your knees. And now can you place the palms of your hands on your buttocks, push your hips forward, and lean back as far that is comfortable.

To perform a Schober test, mark two points on the back; one midway between the posterior superior iliac spines, and the other 10 cm above it. Ask the patient to bend forward, and then measure the distance between these two points. Normally, the distance should lengthen by at least 5 cm. An increase of less than 5 cm indicates restricted lumbar spine range of motion and is suggestive of an inflammatory spondyloarthropathy (e.g., ankylosing spondylitis), but can also occur with chronic back pain and spinal tumors. An alternative form of this test, the modified Schober test, may be preferred.

Now I would like to perform a test that involves making two small markings on your back with my pen, and then measuring the distance between them after you bend forward.

Chest Expansion: Assessment of chest expansion is another, helpful test of ankylosing spondylitis. To measure chest expansion, encircle the chest with a tape measure at the level of the xiphoid process. Then note the measurements at the end of both deep expiration and inspiration.


Contracted Neurologic Exam

Next up is a contracted neurologic exam, with a focus on the function of the L4 to S1 nerve roots, which are the areas most often involved in mechanical low back pain. Extensive neurologic evaluation is usually unnecessary. If you suspect mechanical back pain, then one test per nerve root is sufficient for screening purposes. However, if an abnormality is found, then further examination is warranted. For the purpose of this video, I will discuss sensory, motor and reflex screening tests for each of the relevant nerve roots.


6:20 Sensory Screen

For the sensory screen, dab the patient’s skin with a piece of cotton wool to detect any loss of sensation. Assess three dermatomes, starting distally and moving proximally.


The lateral aspect of the foot corresponds to S1, the web space between the 1st and 2nd toe corresponds to L5, and the medial malleolus corresponds to L4.

Next I will check if you can feel this piece of cotton when I place it on the skin of your lower leg.

Saddle anesthesia, as well as bowel and bladder incontinence are important signs of cauda equina syndrome, which is a surgical emergency. To assess for perineal sensation, which is supplied by sacral roots 2-4, lightly stroke between the upper buttocks with a blunt object. This assessment can performed now or at the end of the examination, whichever you prefer.

It is also important for me to check that sensation in the area of your upper buttock is not impaired.

7:05 Motor Screen

In terms of motor function, instead of examining the strength of all the muscles of the lower legs, nerve root dysfunction can be screened for by assessing three active movements against resistance.


Knee extension tests for L4 function, toe extension tests L5, and toe flexion tests S1. If you detect any weakness, then assess motor function in other movements corresponding to the same nerve root. And remember, always compare both sides.

Now I need to test the muscle strength in your legs and feet. Can you push out with your lower leg against my hand. Can you raise your big toe while I press down. And now can you press down with your big toe as I push up.

7:34 Reflexes

Prior to assessing the reflexes, it is helpful to first palpate the tendon. And if the reflex is not initially obtained, attempt a reinforcement maneuver. For example, you may ask the patient to hook their hands together, and then pull; at which point you should strike the tendon.


The ankle reflex tests the S1 nerve root, while the knee reflex mostly tests L4.


What I need to do next is tap on your knee and ankle with this little hammer.

To assess the plantar response, stroke the patient’s foot with a blunt, but narrow object; run it from the lateral edge of the heel to tuberosity of the fifth toe, and then medially across the forefoot. Normally, all toes will flex (i.e., curl downwards). However, extension of the great toe, known as Babinski sign, is indicative of an upper motor neuron lesion. This finding is highly significant and would negate an isolated diagnosis of mechanical back pain.


Now I need to stroke the bottom of your foot. I must warn you, it may be a little uncomfortable.

8:27 Provocative Tests

Provocative tests can increase suspicion of a particular pathology. The straight leg raise, for example, can reveal irritation of nerve roots L5 and S1, while the femoral stretch tests puts stress on the L2 – L4 nerve roots. Another test that can be performed when there is suspicion of hip pathology is the FABER test.


8:47 Straight Leg Raise

To perform the straight-leg raise, have the patient lie supine with the contralateral leg flexed to about 90° in order to reduce hamstring tightness. Then slowly elevate the ipsilateral leg with the knee in extension. The test is positive if the patient reports leg dominant pain in the distribution of radicular nerve roots. Reproduction of the patient’s typical back pain is not relevant for the sake of this test. So it is very important to clarify with the patient where it is that they felt pain. If there is uncertainly, sensitizing maneuvers such as foot dorsiflexion or neck flexion can help support the finding of nerve root irritation. Also perform the straight leg raise on the other leg. Reproduction of pain on the contralateral side, a maneuver referred to as the crossed straight-leg raise, further supports suspicion of nerve root irritation.

I’m going to slowly raise your leg. Please let me know if you feel any pain. Can you show me where it hurts?

Alternatively, a modified straight leg raise can also be very useful. In this version of the test, the patient’s leg is elevated while in the seated position, thus stretching the nerve root. Reproduction of radicular pain can cause the patient to lean backwards in order to relieve nerve root tension and to place both arms on the table for support, a position referred to as the tripod sign. Failure to lean backward or elicit the pain experienced on the straight leg raise would be suggestive of non-organic pain and could raise concern of malingering.


Conclusion

That brings us to the end. When you finish your exam, remember to thank the patient for their cooperation.


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