[Ultrasonic and radiographic quantification of palmar angulation in metacarpal IV and V neck fractures]

Therapy of metacarpal neck fractures depending on radiographically measured palmar angulation is discussed controversially in the literature. Some authors describe normal hand function of malunited metacarpal neck fractures with a palmar angulation up to 70°; others define 30° as the uppermost limit to maintain normal hand function. However, the methods of measuring palmar angulation are not clearly defined. Here, we present a new method to measure palmar angulation using ultrasound. The aim of this prospective study is to compare the radiographic methods of measuring palmar angulation with the ultrasound method.

20 patients with a neck fracture of the metacarpals IV or V were treated either conservatively or operatively. 2 weeks after trauma or operation, an x-ray was performed. 2 examiners measured the palmar angulation on the oblique and lateral projections using 2 different methods (medullary canal and dorsal cortex methods). At the same time, the 2 examiners performed measurements of palmar angulation using ultrasound. The measurements obtained with the different methods as well as by the 2 examiners at 2 different terms were compared. Intra- and interobserver reliability of each method was calculated, and for the ultrasound method a test for accuracy of the measured angles was performed.

Depending on the method of radiographic measurement and different x-ray projections, an average of up to 20.3° higher angles were determined as compared with the ultrasound method. The average deviation in angles measured within and between the 2 examiners was lower for the ultrasound method than for the radiographic methods, corresponding to a higher degree of intra- and interobserver reliability.

The ultrasound method for measuring palmar angulation in metacarpal neck fractures is simple, and appears to be more precise in comparison to radiographic methods. An exactly lateral projection of the fractured metacarpal bone can be imaged without superposition and exposure to radiation. The question arises whether previous studies that suggested normal hand function with palmar angulation up to 70° might have been based on too high angle-readings due to the use of radiographic methods.