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Physical Assessment

 

Physical Assessment

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Extremities

Movements of the lower extremity beyond a certain point will stretch the lumbosacral plexus and associated nerve roots. Straight leg-raising (i.e., passive flexion of the straightened leg on the hip), or the reverse, extension of the leg on the hip, is used in an attempt to reproduce lower extremity radicular symptoms in patients who are thought to have irritation or damage to the lumbosacral plexus and roots. When the leg is flexed on the hip, the nerve roots of the posterior-lying sciatic nerve, which originates in the lower lumbar and upper sacral roots (L4-S2), begin to be stretched once the limb has reached about 30 degrees of flexion. Extension of the leg on the hip (with the patient lying on their side or prone) stretches the anterior-lying femoral nerve, which originates from the middle lumbar roots (L2-4).

Any mass or inflammatory process impinging on the nerve, plexus, or nerve roots is capable of binding or irritating these structures, causing pain in the peripheral distribution of the nerve. This pain is often in the muscle and bone distribution of the nerves as opposed to the skin or dermatomal distribution. Buttock, posterior thigh, calf, as well as heel discomforts are characteristic of sciatic system involvement, whereas groin and anterior thigh pains are characteristic of femoral system involvement. If there is skin involvement, loss of sensation occurs in appropriate dermatomes or peripheral nerve distribution. However, loss of sensation or weakness will only occur if the lesion is destructive. It is more common to have paresthesias (pins-and-needles sensations) than actual loss of sensation when a nerve root is damaged. A symptomatic irritative lesion may not cause any actual loss of nerve function despite causing significant pain.

Herniated disk is the most common cause of lumbosacral radiculopathy. The great majority of symptomatic intervertebral disks are between the L4-5 or L5-S1 vertebral bodies. Because the L5 and S1 roots exist at these spaces, straight leg-raising with the patient supine, causing sciatic stretch, is the maneuver of choice. A relatively small percentage of lower spine disk problems occur at L3-4 or L2-3, and a tiny number are found at L1-2 or thoracic levels (although these have been recognized more frequently in the era of magnetic resonance imaging). With the higher lumbar protrusions, femoral stretching is the maneuver that is most likely to reproduce symptoms. It must be noted that an increase of back pain, alone, is not considered an indication of nerve root involvement and is considered a negative straight leg-raising test. Such a "negative test" may still cause pain, but this is probably due to stretching irritated tendons, joints and muscles in the back. Also, a true positive test must be distinguished from tightness of the hamstring muscles, which can produce discomfort during straight leg-raising.

Flexion of the head on the chest (chin to chest) pulls the spinal cord upward and stretches the lumbosacral roots somewhat. Therefore, lower extremity symptoms may be exacerbated in the patient with lumbosacral root irritation.

Meningitis can inflame the meninges and nerve roots at all spinal levels. Therefore straight leg-raising is often positive with meningitis. In fact, there may be involuntary flexion of the knees during attempted straight leg-raise (Kernig sign).

Acute or chronic arthritis of the hip, on occasion, causes referred pain in the knee and, less commonly, in the foot. Straight leg-raising may irritate a damaged hip joint and may give a misleading impression of sciatic root irritation. However, hip joint pathology is easily detected by rotating the femur on the hip while the knee and hip are flexed. This flexion of the knee puts slack on the sciatic and femoral nerves and should not put significant stretch on the sciatic nerve roots. Pain and limitations of motion in internal and external rotation of the flexed hip (Patrick maneuver) suggests hip disease, and appropriate x-rays can confirm this suspicion.

Spine

Back pain is a common, nearly ubiquitous symptom. Pathologic processes (degenerative, neoplastic, or inflammatory) in or near the spinal column frequently give rise to local muscle spasm and pain. This may lead to postural abnormality and/or palpable firmness and tenderness of muscles. When the paraspinal muscles contract unilaterally, they bow the spine laterally; the concave side of the bow appears on the side of increased muscle tension. This lateral bowing is called scoliosis and can be observed most easily when the patient is erect. Observation is further facilitated by making a mark with a pen on the palpable top of the dorsal spinous processes of the vertebrae. The only exception to the rule of contralateral bowing occurs at the lumbosacral junction where the paraspinal muscles are broadly attached to the sacrum and the ilium. The bowing occurs toward the side of the spasm in this instance.

Many neurologic conditions result in abnormal muscle tone. When these begin early in life there may be associated skeletal abnormalities, including severe scoliosis. Although many scolioses are "idiopathic," probably related to problems of skeletal maturation, severe scoliosis, particularly when accompanied by other signs such as pes cavus (high arched feet) should prompt some neurologic examination. Progressive scoliosis, even when it does not result from neurologic abnormality, can cause neurologic dysfunction if not arrested.

Most back pain is benign. Rarely, it can result from localized serious pathology (infectious, neoplastic, hemorrhagic, etc). In many such cases, percussion of the spine to elicit point tenderness often produces localized pain. This percussion is carried out with the hypothenar portion of the fist. Because a large area is covered with each blow to the spine and there is diffusion to several vertebral segments, use of a percussion hammer to tap each spinous process may more accurately localize the involved segments, prompting some consideration of imaging.

    
       

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