603 Evaluation the First Ray Instability Using the Double Dorsiflexion Test: A Prospective Observational Case-Controlled Study

Abstract

Abstract First-Ray (FR) stability allows for foot propulsion in-stance, taking 60% weight. First-ray instability (FRI) is associated with middle column overload, synovitis, deformity, and osteoarthritis. Clinical detection can still be challenging. We propose to develop a clinical test that helps identify FRI using two simple manual manoeuvres. 10 patients with unilateral FRI were recruited. Stringent exclusion criteria were applied including hallux MTP pain, laxity, inflammatory arthropathy. A Klauemeter directly measured the sagittal plane dorsal first metatarsal head translation of affected vs unaffected feet. Maximum passive proximal phalanx 1st MTP joint dorsiflexion was measured using Tracker motion software analysis with and without applying a dorsal force at the 1st metatarsal head using a Newton meter. P-value of <0.05 was considered significant. FRI feet had dorsal translation greater than 8mm (median, 11.94; interquartile range [IQR], 10.23–13.81) vs 1.77 for unaffected control feet was (median, 1.77; interquartile range [IQR], 1.23–2.96) using the Klauemeter. The percentage reduction in 1st MTP joint dorsiflexion ROM when applying the double dorsiflexion test FRI (mean reduction of 67.98%) when compared to control feet (mean reduction of 28.44%)(P<0.01). Receiver operating characteristic (ROC) analysis showed that a 50% reduction in dorsiflexion ROM of 1st MTPJ when performing the double dorsiflexion test achieved a specificity of 100% and sensitivity of 90% (AUC =0.990, 95%CI [0.958–1.000], P>0.0001). The double dorsiflexion (DDF) is easy to perform with manual manoeuvres that avoid complex instrumented and radiation-based assessment. A greater than 50% decrease in proximal phalanx motion has an over 90% sensitivity in identifying feet with FRI.