Femorocoxometry: angles and segments characteristic of dysplastic and dysmorphic hip conditions in adult. Measurement using a femorocoxometer for standard or reduced (digitized) films.

Abstract

I have designed a new measurement instrument drawn on transparent film and suitable for any hip radiograph. It replaces the femorocoxometer first produced in France in 1963 and is intended to assist in the evaluation of hip dysplasia and subluxation, as well as of other developmental or acquired abnormalities of the hip. A new design was needed to obtain an instrument suitable not only for conventional radiographs but also for the new reduced-sized images frequently obtained today. Angles can be measured on films of the pelvis and on films of the hip taken in the standing position. Several millimeter-graduated segments have been added to the new version of the instrument to allow measurement of six distances characteristic of the development of hip dysplasia or subluxation. The instrument permits measurement of all the angles related to the architecture of the radiographic hip in the three planes, coronal (CE or VCE, HTE, and NSA angles), anteroposterior (VCA angle), and cross-sectional (femoral neck anteversion). All the parameters are described and illustrated. For each of them, the directions for use of the instrument are given step by step. A number of difficult or ambiguous measurements are discussed, and relevant recommendations are made. A table reports the classical values allowing to distinguish between the dysplastic and the normal hip.