REIDER PART 2
97

Chaptfu 9

Lumbar Spine 357

Bowstring Sign

MacNab described anothcr confirmatory test for sciatic nerve tension known as the bowstring sign. To elicit the bowstring sign, the examiner again begins by performing the straight-leg raising test to the point of rcproduction of the patient s radicular pain. The knee is then flexed 90°, which usually relieves the patients symptoms. Digital pressure is then applied to the popliteal fossa over the posterior aspect of the sciatic nerve (Fig. 9-27). If this again reproduces the patients radicular pain, the impres-sion of sciatica is further confirmed. The sensitivity of the bowstring sign is similar to that of Lasfcgues test in con-firming lumbar radiculopathy (0.69).

Swmp Test

The slump test is really a variant of the straight-leg raising and Lascgues tests pcrformed in the seated position. The slump test is a progressive series of maneuvers designed to place the sciatic nerve roots under increasing tension. The patient begins the slump test sitting on the side of the examination table with the back straight, looking straight ahead (Fig. 9-28A). The patient is then encouraged to slump, allowing the thoracic and lumbar spines to collapse into flexion while still looking straight ahead (Fig. 9-28B). The ncxt step is to fully flex the cervical spine (Fig. 9-28C). The patient is then instructed to extend one knee, thus performing a straight-leg raise (Fig. 9-28D). The patient then dorsiflexes the foot on the same side, thus duplicating the Laseguc test (Fig. 9-28E). The process is then repcatcd with the opposite lower extremity.

At each stage in the procedurę, the patient informs the examiner what is being felt and whether radicular pain is produced. Many normal individuals feel tightness in the lower back and the thigh with this series of maneu-vers. Reproduction of familiar radicular pain, as in the straight-leg raising, Lasegue, and crossed straight-leg raising tests, is highly suggestive of sciatic nerve root tension. Subsequent extension of the neck relaxes the spinał cord and may thus relieve nerve tension (see Fig. 9-28F).

Femoral Nerve Stretch Test

As noted, the straight-leg raising test and its variants do not place significant tension on the nerve roots above L5. Although compression of the upper lumbar nerve roots is not common, it does occur. Herniations of the L3-L4 disk commonly compress the L4 nerve root. The femoral nerve stretch test is designed to assess compression of the L2, L3, or L4 nerve roots. To perform the femoral nerve stretch test, the patient is positioned prone on the exam-ination table with the knee flexed to at least 90°. The patient s hip is then extended passively by lifting the thigh off the cxamination table (Fig. 9-29). In the normal patient, this induces only a mild feeling of tightness in the anterior thigh. When one of the nerve roots that con-tribute to the femoral nerve is compressed, this maneuver reproduces the patients radicular pain in the anterior thigh.

Miscellaneous Special Tests

Single Leg Hyperextension Test It has alrcady been noted that hyperextension of the lumbar spine is often painful in the presence of spondy-lolysis. The single leg hyperextension test has been described as a morę specific test to detect the presence of spondylolysis and to suggest which side is involved in the

Figurę 9-27. A and B, Bowstring sign.