Measuring Joint Flexibility in Hallux Rigidus Using a Novel Flexibility Jig

Abstract

Background: The flexibility of the first metatarsophalangeal (MTP) joint in patients with hallux rigidus (HR) has not been studied. Compared to measuring range of motion alone, measures of joint flexibility provide additional information that may prove useful in the assessment of HR. The purpose of this study was to assess the flexibility of the hallux MTP joint in patients with HR compared to controls using a novel flexibility device. Methods: Fifteen patients with Coughlin stage II or III HR and 20 healthy controls were recruited prospectively. Using a custom flexibility jig, each of 2 raters performed a series of seated and standing tests on each subject. Dorsiflexion angle and applied torque were plotted against each other to generate 5 different parameters of flexibility. Differences between (1) HR patients and controls and (2) the sitting and standing testing positions were assessed with t tests. Intrarater test-retest reliability, remove-replace reliability, and interrater reliability were assessed with intraclass correlation coefficients (ICCs). Results: Patients in the HR group were older than patients in the control group ( P < .001) and had lower maximum dorsiflexion ( P < .001). HR patients were less flexible as measured by 3 of the 5 flexibility parameters: early flexibility (first 25% of motion; P = .027), laxity angle ( P < .001), and torque angle ( P = .002). After controlling for age, only laxity angle differed significantly between HR patients and controls ( P < .001). Generally, patients were more flexible when seated compared to standing, with this effect being more marked in HR patients. All parameters had good or excellent intra- and interrater reliability (ICC ≥ 0.60). Conclusions: Hallux MTP joint flexibility was reliably assessed in HR patients using a flexibility device. Patients with HR had decreased flexibility of the hallux MTP joint compared to control patients. Level of Evidence: Level II, prospective comparative study.