It may appear to work but it causes unwanted recompilations, adversely affects performance and can be unreliable. Also it is poor practice because you should use a naming convention that doesn't conflict with Microsoft's recommendations.

"We strongly recommend that you not use the prefix sp_ in the procedure name. This prefix is used by SQL Server to designate system stored procedures."
CREATE PROCEDURE (Transact-SQL)

The only time you should prefix a stored procedure name with sp_ is if you specifically want to create a system stored procedure in the Master database and with the system proc behaviour.