Scientific article
Reliability and Clinical Importance of Teardrop Angle Measurement in Intra-articular Distal Radius Fracture

https://doi.org/10.1016/j.jhsa.2011.10.056Get rights and content

Purpose

The teardrop angle (TDA) is a newly characterized radiographic parameter that some authors propose as an indicator of articular incongruity of the lunate facet. The purposes of this study were to investigate intra-observer and interobserver reliability of the measurements of the TDA and to determine whether the TDA is a reliable indicator of articular step and gap formation after distal radius fracture.

Methods

We studied radiographs of 24 uninjured wrists and 24 wrists with intra-articular distal radius fractures. On standard and 10° tilt views of lateral wrist radiographs, the teardrop represents the volar rim of the lunate facet, and the TDA is defined as the angle between the central axis of the teardrop and the radial shaft. We examined interobserver and intra-observer reliability for 3 observers using the intraclass correlation coefficient (ICC) for measurements of the uninjured and fractured wrists. For subjects with fractures, we determined correlation of the TDA-volar tilt with the articular step and gap measured by computed tomography using simple linear regression.

Results

There was almost perfect intra-observer (ICC = 0.95) and interobserver (ICC = 0.93) reliability in the fractured wrists. We observed substantial intra-observer (ICC = 0.64) and fair interobserver (ICC = 0.28) reliability in the uninjured wrists on the standard lateral radiographs. On the 10° tilt views, intra-observer and interobserver reliability in the uninjured wrists increased to substantial levels (ICC = 0.76 and 0.61, respectively). The TDA-volar tilt was significantly associated with articular step and gap on computed tomography.

Conclusions

The TDA, measured on the lateral radiograph of the wrist, exhibits higher intra-observer and interobserver reliability in fractured wrists compared with uninjured wrists. On the 10° tilt views, the reliability increased in the uninjured wrists. Measurement of the TDA in plain radiographs may allow direct estimation of articular incongruity as seen on sagittal computed tomography reconstruction images.

Type of study/level of evidence

Diagnostic II.

Section snippets

Definition of TDA

On standard and 10° tilt views of the lateral wrist radiographs, we identified the teardrop, representing the volar rim of the lunate facet. A line drawn along the central axis of the teardrop (parallel to the subchondral bone of the volar rim) created a TDA with a line extending from the central axis of the radial shaft (Fig. 1B). The central axis of the teardrop was defined as a tangential line of a circle that matched the arc of the articular surface of the volar lunate facet and passed

Results

On the lateral projection, UV averaged 0 mm in non-fractured wrists and 2 mm in fractured wrists. RI averaged 26° and 16°, respectively, and VT averaged 17° and 0°, respectively. The VT in 10° tilt views from the lateral projection was a mean of 13° in non-fractured wrists. The TDA on the lateral wrist projection was a mean of 55° in non-fractured wrists and 43° in fractured wrists. The TDA in 10° tilt views was a mean of 64° in non-fractured wrists (Table 1).

Interobserver and intra-observer

Discussion

Fractures of the distal radius involving the volar lunate facet, as described initially by Melone,13 are among the more difficult articular fractures to treat effectively. Failure to reduce and stabilize the lunate facet during open reduction and internal fixation has been shown to result in poor functional and radiographic outcomes.14, 15 On the lateral view of the plain radiographs, the teardrop represents the volar rim of the lunate facet. Because the central axis of the lunate is normally

References (19)

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Copyright © 2012 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.