A new clinical test for first ray sagittal instability: the double dorsiflexion test
C. Pasapula, A. Al-Sukaini, I. Liew, J. Goetz, S. Cutts
Introduction: A rigid first ray allows good foot propulsion in stance, taking 60% weight. First, ray instability (FRI) is associated with middle column overload, synovitis, deformity and osteoarthritis. We propose and validate a new clinical test to identify FRI.
Methods: Ten patients who had 8mm or more unilateral dorsal first ray instability as measured with a Klaue Meter were recruited. The maximum passive dorsiflexion of the proximal phalanx at the 1st MTP joint was measured using a video camera and Tracker motion software with and without applying a dorsiflexion force 1st metatarsal head using a Newton meter. SPSS software was used to analyse the data.
Results: The median average dorsal translation for FRI was 11.94mm; interquartile range [IQR], 10.23-13.81. The median average dorsal translation for control feet was 1.77mm; interquartile range [IQR], 1.23-2.96). There was significant difference (P <0.0001) in the percentage of reduction in the 1st MTP joint dorsiflexion ROM when applying the double dorsiflexion test in the FRI group (mean reduction of 67.98%) when compared to control feet (mean reduction of 28.44%). 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).
Conclusion: The double dorsiflexion (DDF) test is easy to perform in the outpatient setting and can be used in conjunction with other tests in the assessment of FRI.
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