Evaluation of first ray instability using the double dorsiflexion test: A prospective observational case-controlled study

Background: 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.

Methods: 10 patients with unilateral FRI were recruited. Unaffected contralateral feet were used as controls. Stringent exclusion criteria were applied including hallux MTP pain, laxity, inflammatory arthropathy and collagen disorders. 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 a video capture and Tracker motion software analysis with and without applying a dorsal force at the 1st metatarsal head using a Newton meter. Proximal phalanx motion was compared in affected vs unaffected feet with and without dorsal metatarsal head force application and compared to direct measurements using the Klaumeter. P value of < 0.05 was considered significant.

Results: FRI feet had dorsal translation greater than 8 mm (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).

Conclusion: The double dorsiflexion (DDF) is easy to perform with two relatively simple manual manoeuvres that avoids the need for complex instrumented and radiation-based assessment. Greater than 50% decrease in proximal phalanx motion has an over 90% sensitivity in identifying feet with FRI.

Level of evidence: This was a prospective case-controlled study of consecutive cases of a level II evidence.