3DGAThree-dimensional gait analysis ICC Intraclass correlation coefficient RFT Rectus femoris transfer ROC Receiver operator characteristics AIM The aim of this study was to clarify the method of the Duncan-Ely test and to estimate its interobserver reliability and validity by comparing it with three-dimensional gait analysis (3DGA).
METHOD This study included 36 consecutive ambulatory patients with cerebral palsy (CP)who underwent preoperative 3DGA. The Duncan-Ely test was performed during three different velocities (slow, gravity, and fast). The interobserver reliability was assessed by three examiners. The results of the test were compared with kinematic variables derived from the gait analysis to assess the sensitivity and specificity of the test. The cut-off value was determined at the point of trade-off between the highest sensitivity and specificity.
RESULTSThe intraclass correlation coefficient measuring interobserver reliability of the Duncan-Ely test was greatest during fast velocity (0.819). The sensitivity and specificity of the test during gravity velocity for knee range of motion total were 63.0% and 100% respectively, with a cut-off value of 78.3°. The sensitivity and specificity of the test during fast velocity for knee range of motion total were 66.7% and 100% respectively, with a cut-off value of 65°.
INTERPRETATIONThe Duncan-Ely test shows excellent reliability in fast knee-flexion velocity, and good sensitivity and specificity compared with 3DGA during physical examination as a preoperative assessment of rectus femoris spasticity in patients with CP.Stiff-knee gait, which is defined as a restricted arc in knee motion during swing, 1 is a common gait disorder in ambulatory patients with cerebral palsy (CP), regardless of the anatomical type of CP.2 Stiff-knee gait results in foot clearance problems and reduces gait velocity and step length. Some patients complain of their shoes wearing out rapidly. Although there is still controversy, 3 it is now widely accepted that one of the causes of stiff-knee gait in patients with CP is spasticity of the rectus femoris. [4][5][6][7] Since rectus femoris transfer (RFT) has been recommended for restoring knee motion during the swing phase, it is now the standard surgical treatment for stiff-knee gait in patients with CP and is frequently performed as part of a single-event multilevel surgery. 1,5,8,9 Before single-event multilevel surgery, a physical examination is essential to assess the patient's physical status. The Duncan-Ely test, among others, has been recommended as a clinical tool for assessing rectus femoris spasticity. 10 In the classic Duncan-Ely test, the examiner passively flexes the knee rapidly while the patient lies prone in a relaxed state. The test is considered positive if the patient simultaneously flexes their ipsilateral hip or if resistance is felt by the examiner during passive knee flexion.10,11 A positive test result reflects the velocitydependent spasticity of the rectus femoris muscle during the rapid movement test as well as mu...