Answer: Based on your description it is difficult to tell if they are bare on the interior simply due to lack of light or to some other reason. If the alternative is to remove them, then it is worth a try to cut them back very hard. The best time to do this would be very early spring. If you need to try it now, make sure they receive ample water so that the soil stays moist but not soggy until they recover from the "haircut". (Doing it now increases the chances that you will kill them outright.) They should regrow quickly because of their large established root systems.
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