how many times did the head & neck endarter nec been performed until 2103?
select count(*) from procedures_icd where procedures_icd.icd9_code = ( select d_icd_procedures.icd9_code from d_icd_procedures where d_icd_procedures.short_title = 'head & neck endarter nec' ) and strftime('%y',procedures_icd.charttime) <= '2103'