Validity and reliability of the muscle function scale, aimed to assess the lateral flexors of the neck in infants

Abstract

Infants with congenital muscular torticollis (CMT) often have an imbalance in muscle function in the lateral flexors of the neck, and the need for a valid and reliable assessment tool to determine muscle function in these muscles is essential. The lateral uprighting response is used to examine and to strengthen the sternocleidomastoid muscle. A Muscle Function Scale (MFS) has been refined and used for several years in a clinic for infants with CMT. The MFS describes an infant's muscle function in the lateral flexors of the neck through ordered categorical scores. The aim of this study was to find out if the muscle function scale (MFS) is valid and reliable. A panel of experts examined validity, and the kappa statistic and intraclass correlation coefficient were calculated for interrater and intrarater reliability. The MFS is found to be a valid tool to measure the muscle function of the lateral flexors of the neck in infants with CMT. The interrater and intrarater reliability is high for both novice and experienced physiotherapists (kappa>0.9; ICC>0.9).