Hip extensor contraction test for trauma (Butt Wink)
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A common step in evaluating trauma patients has been the digital rectal exam, where one component was to evaluate neurologic capacity by assess anal tone. A more recent view has found this method to be unreliable, and it has been suggested that replacing the DRE with a butt wink test would prove as useful for the neurological assessment.
There are a couple aspects to consider for this replacement.
A successful, firm contraction of the Gluteus Maximus can obviously indicate sufficient functioning of the Gluteus Maximus muscle. It can also infer some integrity of the bony pelvis since this requires good stability as the gluteus maximus has a broad attachment across the sacrum, coccyx, ilium and sacrotuberous ligament. Because the muscle is being voluntarily controlled, we also assume the nervous system components to be intact, including the spinal nerves L5-S2 as well as their termination in the inferior gluteal nerve.
Conversely, if there is a deficit in the contraction of this muscle all of the above structures would be implicated as being deficient, and we may consider including disruption of the gluteal artery, although this is extremely rare.
If the femur or lower extremity has been involved in the trauma as well, the patient may be unable to perform this procedure.
If the patient successfully performs the gluteus maximus contraction without incident, you may also include palpation of the biceps femoris while having the patient push the outside of their heel into the table. This can help validate the integrity of the biceps femoris muscle and its innervation, which is S2-4.
Subject lays supine on the table.
The clinician stands on the side of and palpates the gluteus maximus at the level of the greater trochanter.
The clinician gives the instruction to "Clench/contract your butt muscle" or “push both heels into the table”.
If a strong contraction is felt, it is graded as Pass.
If there is a weak, asymmetrical, or no contraction it is graded as a fail.