Radiographic goniometry of the PIP-joint: A reliable measurement method.

INTRODUCTION: Arthrodesis of the proximal interphalangeal joint (PIP joint) is a good treatment option for relief of arthritic pain. The angle of the fused PIP joint is considered important for postoperative digital function. It is therefore important to reliably measure the actual angle of fusion. Goniometry performed by hand therapists or hand surgeons can generate measurement errors. PURPOSE OF THE STUDY: The purpose of this study is therefore to investigate the intraobserver and interobserver reliability of measuring the angle of fusion of the PIP joint on X-rays. STUDY DESIGN: A clinimetric study was conducted investigating the reliability of X-ray goniometry. METHODS: Three blinded observers measured the angle of the PIP-joint fusion on a lateral postoperative X-ray. The intraobserver and interobserver reliability was calculated. RESULTS: Ninety-four patient X-rays were measured. The intraobserver reliability showed an intraclass correlation coefficient (ICC) of 0.94, and the ICC for the interobserver reliability ranged between 0.92 and 0.95. DISCUSSION: Because this is the first reliability study on radiographic goniometry, comparison of our data with other similar studies is difficult. The best comparison can be made to in vivo goniometry. Based on the investigation of ICC values of various studies on the reliability of in vivo goniometry, radiographic goniometry seems to be more reliable. CONCLUSIONS: These results indicate an excellent reliability, which is generally higher than the reliability for in vivo goniometry of the PIP joint performed by hand therapists or hand surgeons. We can conclude that radiographic goniometry of the PIP joint is a highly reliable measurement method.