Assessment of volar angulation and shortening in 5th metacarpal neck fractures: an inter- and intra-observer validity and reliability study

Four methods for measuring volar angulation in 5th metacarpal neck fractures were tested for validity and reliability. Mid-medullary canal measurement in the lateral view (method MC-90) has previously been proven valid in a cadaveric study, hence used as a reference to test validity of the latter three. These three yielded a significant different mean fracture angle compared with MC-90, with only minor enhancement in reliability. Therefore, none of these three methods is recommended as a better standard method than the MC-90, where reliability was found to be substantial (intraclass correlation coefficient 0.53-0.81). Two methods for measuring shortening in 5th metacarpal neck fractures were compared, and stipulation of shortening by drawing a line through the most distal point of the heads of the neighbouring 3rd and 4th metacarpals (method SH-Stip) is a simple method with excellent reliability (intraclass correlation coefficient 0.81-0.96) for estimating shortening, requiring only radiological examination of the injured hand.