Volleyball player is suffering

My father, aged 76, who was a Former Indian Volleyball player is suffering from a typical neurological problem for the last 5-6 years.
Brief History : He underwent the following operations : 1) In 1972:Spine operated for prolapsed disc between lumber 3 &4. 2) In 1998: Bypass surgery done by harvesting vein from right leg-Lima harvested 3) In 2005: Total knee replacement done of both knees. Before TKR done in 2005 he started feeling vibration of left butex muscle and on the sole of right foot. A neurologist was consulted who treated him for 2 months but with no relief. He okayed for TKR as the neurological problem had nothing to do with knee operations. On discharge after TKR in 2006 though knee operation ended very successful. The neurological problem persisted. In Jan 2006 MRI of Lumbo Sacral pine was performed and observed that critical lumbar canal stenosis at L4-5 needed correction. Thus in March 2006 endoscopic discectomy was done at L4-5. But condition detorated day after ay and both the butax muscles and soles of both the feet started vibrating at times while standing or walking. During the attack while walking or standing, he has to sit down for some time, then he gets relief. Now the condition has gone so worse that soles of both the feet have gone so spongy that he feels constantly as if he is standing on water. He has to be very careful while standing or walking or else he may fall loosing body balance. When neurologist were consulted he has been told that there is no diagnosis for this disease as neurology is still in the infant stage. Many neorobian tablets & neorobian injection taken, B12 tablets & injections taken, but the condition gets worsened day by day. The tragedy that even after undergoing color dopler tests nothing could be diagnosed. Sensation on the soles is full.
My sincere request to any proficient neurologist , is to help diagnose this unique neurological problem and recommend an ideal treatment such that he gets some relief from his ever detoriating condition