What is the angle of a banana? The difficulty in reliable assessment of hypospadiaschordee.
Christopher S. Cooper, MD, FACS, FAAP, Gina M. Lockwood, MD, FAAP, Angelena Edwards, MD, Sarah S. Perry, MS, Douglas Storm, MD, FAAP.
University of Iowa, Iowa City, IA, USA.
Background: The degree of chordee associated with hypospadias impacts operative management. Unfortunately, poor inter-observer reliability in assessing chordee by multiple methods in vitro has been demonstrated. This variability may be related to the fact that hypospadias chordee is not a discrete angle, but rather an arc-like curvature similar to that of a banana. We assessed the inter-rater reliability of a novel method of chordee measurement and compared it to measurements with a goniometer both in vitro and in vivo.Methods: In vitro assessment of curvature was performed using 5 different bananas, and in vivo chordee measurement was performed during 43 hypospadias repairs independently by faculty and resident physician following penile degloving and artificial erection. Angle assessment was performed with a goniometer and also with a smart phone app using ruler measurements of the length and width of the arc (Figure). The proximal and distal aspect of the arc to be measured was marked on the bananas, whereas the penile measurements were taken from the penoscrotal to the sub-coronal junctions. Mixed linear regression with random intercepts for measurer and banana were used to calculate in vitro inter and intra-rater reliability using the associated intraclass correlation coefficient (ICC). In vivo interrater reliability was similarly calculated from mixed linear regression with random intercepts for patient. Results: In vitro banana assessment demonstrated strong intra- and inter-rater reliability for length (0.89 and 0.88, respectively) and width measurements (0.97 and 0.96). The calculated angle demonstrated an intra and interrater reliability of 0.67 and 0.67. The banana goniometer/protractor measurements were weak with an intra-rater and interrater reliability of 0.33 and 0.21. With penile chordee, the inter-rater reliability was strong for length and width measurements (0.95 and 0.94) and 0.64 for calculated angle, however, interrater reliability of the goniometer angle was stronger (0.96). Further assessment of interrater goniometer reliability was performed relative to degree of chordee as characterized by faculty. The inter-rater reliability for < 15 degrees, 16-30, and >30 degrees was 0.68 (n=20), 0.34 (n=14), and 0.90 (n=9), respectively. When faculty classified the angle as <15 degrees, 15% were classified by the resident as > 15 degrees. When the angle was 16 to 30 degrees, 14% and 21% were classified by resident as < 15 degrees or >30, respectively. No cases were classified by the resident as < 30 degrees when the faculty classified the angle > 30 degrees.Conclusions: The arc-like curvature, rather than a discrete bend, makes the goniometer an imperfect tool to assess hypospadias chordee. The lack of well-defined penile landmarks, in addition to variability in length and curvature of the penis with alterations in turgidity during artificial erection, decrease the reliability of arc length and width measurements. Our data suggests reasonable inter-rater reliability of penile chordee assessment via goniometer in categorizing patients as having little to no chordee or having over 30 degrees of curvature.
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