LOWER LIMB MYOTOMES

 

Myotomes

Having completed the scanning examination of the peripheral joints, the examiner next tests the patient's muscle power for possible neurological weakness.84 With the patient lying supine, the myotomes are assessed individually . When testing myotomes, the examiner should place the test joint or joints in a neutral or resting position and then apply a re i ted isometric pressure. The contraction should be held for at least 5 seconds to show any weakne . If feasible, the examiner should test the two side simultaneously to provide a comparison. The simultaneou bilateral comparison is not possible for movements involving the hip and knee joints because of the weight of the limbs and stress to the low back, so both sides must be done individually. The examiner should not apply pressure over the joints, because this action may mask symptoms

Myotomes of the lumbar and Sacral Spines

• L2: Hip flexion

• L3 :knee extension

• L4: Ankle dorsiflexion

• L5: Great toe extension

• S1: AnkIe plantar flexion, ankle eversion, hip extension

• S2: Knee flexion

It should be remembered that the examiner has prviously tested the 51 myotome with the patient standing and has tested for a positive Trendelenburg's sign. (modified Trendelenburg test); these movements are repeated here only if the examiner is unsure of the result and wants to test again. The ankle movements should be tested with the knee flexed approximately 30°, especially if the patient complains of sciatic pair because full dorsiflexion is considered a provocatie maneuver for stretching of neurological tissue. Like wise, the extended knee increases the stretch on the sciatic nerve and may result in false signs, such weakness that results from pain rather than from pre-· sure on the nerve root. If the patient is in extreme pain, all tests with the patient in the supine position should be completed before the patient is tested in prone. This reduces the amount of movement the patient must do, decreasing the patient's discomfort. Ideally, all tests in the standing position should be performed first, followed by tests in the sitting, supine, side lying, and prone positions.

This procedure is shown in the precis at the end of the chapter. Hip flexion (L2 myotome) is tested by flexing the patient's hip to 30° to 40°. The examiner then applies a resisted force into extension proximal to the knee while ensuring that the heel of the patient's foot is not resting on the examining. The other side is then tested for comparison. To prevent excessive stress on the lumbar spine, the examiner must ensure that the patient does not increase the lumbar lordosis while doing the test and that only one leg at a time is tested. To test knee extension or the L3 myotome, the examiner flexes the patient's knee to 25° to 35° and then applies a resisted flexion force at the midshaft of the tibia ensuring the heel is not resting on the examining. The other side is tested for comparison. Ankle dorsiflexion (L4 myotome) is tested by asking the patient to place the feet at 90° relative to the leg (plantigrade position). The examiner applies a resisted force to the dorsum of each foot and compares the two sides. Ankle plantar flexion (Sl myotome) is compared in a similar fashion, but the resistance is applied to the sole of the foot. Because of the strength of the plantar flexor muscles, it is better to test this myotome with the patient standing. The patient slowly moves up and down on the toes of each foot (for at least 5 seconds) in turn (modified Trendelenburg test), and the examiner compares the differences as previously described. Ankle eversion (Sl myotome) is tested with the patient in the supine lying position, and the examiner applies a force to move the foot into inversion.

Toe extension (L5 myotome) is tested with the patient holding both big toes in a neutral position. The examiner applies resistance to the nails of both toes an compares the two sides. It is. rati'e that the resistance be isometric, so the amount of force in this case is less than that applied ;knee extension, for example.

Hip,-ren ion (Sl myotome) is tested with the patient in~ prone. This test needs to be done only if the pa 'en . unable to do plantar flexion testing in standin~ or ankle e'ersion. The knee is flexed to 90°. The examiner then lifts the patient's thigh slightly off the examining rable while stabilizing the leg. A downward force i applied to the patient's posterior thigh with one hand while the other hand ensures that the patient's thigh is not resting .

Knee flexion (S1-S2 myotomes) is tested in th same position (prone) with the knee flexed to 90°. " extension isometric force is applied just above the ankle. Although it is possible to te both knee flexors at the same time, it is not advisab to do this because the stress on the lumbar spine too great.

LOWER LIMB MYOTOMES

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