Manassas Chiropractor. Dr. Dennis O'Hara provides Auto Injury, Personal Injury, Back Pain, Whiplash, Pain Management, Headaches, Rehabilitation, back pain relief, neck pain relief to the following locations: 20112, 20110, 20111, 20109. 20112 Chiropractor providing Auto Injury, Personal Injury, Back Pain, Whiplash, Pain Management, Headaches, Rehabilitation in Manassas, 20112, 20110, 20111, 20109, Virginia.