Since we need to find out some old stored procedures what is unused any more, we can use “dm_exec_procedure_stats”

SELECT sc.name, p.name 
FROM sys.procedures AS p
INNER JOIN sys.schemas AS sc
  ON p.[schema_id] = sc.[schema_id]
LEFT OUTER JOIN sys.dm_exec_procedure_stats AS st
  ON p.[object_id] = st.[object_id]
WHERE st.[object_id] IS NULL
ORDER BY p.name;

and with sys.object, we can find what’s unused:

SELECT name
FROM  sys.objects -- consider schemas
where type_desc='SQL_STORED_PROCEDURE'
and name not in (SELECT p.name 
FROM sys.procedures AS p
INNER JOIN sys.schemas AS sc
  ON p.[schema_id] = sc.[schema_id]
LEFT OUTER JOIN sys.dm_exec_procedure_stats AS st
  ON p.[object_id] = st.[object_id]
WHERE st.[object_id] IS NULL
)