About Ankylosing Spondylitis. Ankylosing spondylitis is a form of progressive arthritis due to chronic inflammation of the joints in the spine. Its name comes from the Greek words  ankylos,  meaning stiffening of a joint, and  spondylo,  meaning vertebra.nkylosing Spondylitis. A form of arthritis that affects the spine, the sacroiliac joints, and sometimes the hips and shoulders. In severe cases, the joints of the spine fuse and the spine becomes rigid. PubMed Health Glossary. (Source: NIH-National Institute of Arthritis and Musculoskeletal and Skin Diseases).
The most common cause of numbness in the part of the hand that you describe (the ring finger) would be carpal tunnel syndrome, which is a condition in which the median nerve, which runs down the center of the wrist, becomes pinched or inflamed.
Numbness of the fingers or hands is often associated with tingling. These symptoms are referred to as paresthesia of the fingers. Peripheral neuropathy is damage to the nerves of the extremities that often results in numbness or tingling. Longstanding or uncontrolled diabetes is one of the major causes of peripheral neuropathy. Alcohol abuse is another cause of peripheral neuropathy. A number of conditions are associated with numbness, burning, pain, or tingling of the fingers and hand, including stroke, multiple sclerosis, Raynaud's disease, and vascular diseases.