The Combined Nomenclature set out in Annex I to Council Regulation (EEC) No 2658/87 of 23 July 1987 must be interpreted as meaning that spinal fixation systems such as those at issue in the main proceedings may not be classified under subheading 9021 90 90 of the Combined Nomenclature if they are covered by another subheading of heading 9021 of the Combined Nomenclature. Whether those systems may be classified under subheading 9021 10 10 or subheading 9021 10 90 of the Combined Nomenclature will depend on the principal function they perform, which is a matter for the referring court to determine by having regard to the objective characteristics and properties of such systems as well as to their intended and actual use.