Abstract
BackgroundFirst metatarsophalangeal joint (MTPJ) mobility is commonly assessed by its angular displacement (joint angle) or subjectively rated as ‘hypermobile’, ‘normal’ or ‘stiff’ by a clinician. Neither of these methods is ideal because displacement alone does not take into account the force required to displace the joint and subjective evaluation is not always reliable. This study presented a novel method to determine the passive quasi-stiffness of the first MTPJ. The reliability of the proposed method was also assessed. The first MTPJ passive quasi-stiffness of 13 healthy subjects were measured at two occasions, 7 days apart, by two testers (experienced and inexperienced). A tactile pressure sensing system was used to measure the force applied to dorsiflex the first toe by the testers. The torque (in Nmm) about the first MTPJ was calculated as the applied force (in N) multiplied by a moment arm (in mm), where moment arm was the length of the first proximal phalanx. A video camera recorded the motion of the first MTPJ, simultaneously with force measurements, to determine the joint angular displacement (in degrees) using the Dartfish software. The quasi-stiffness (in Nmm/degrees) was calculated as the slope of a graph where torque was plotted against first MTPJ angular displacement. Descriptive statistics of the first MTPJ quasi-stiffness were calculated. Intra-rater and inter-rater reliability were assessed using Bland and Altman plot, intraclass correlation coefficients (ICC), and standard error of measurement (SEM).ResultsFirst MTPJ quasi-stiffness of the subjects ranged widely from 0.66 to 53.4 Nmm/degrees. Intra-rater reliability for experienced tester was moderate (Session 1: 14.9 ± 14.6 Nmm/degrees, Session 2: 14.2 ± 8.5 Nmm/degrees, ICC = .568, SEM = 7.71 Nmm/degrees). Inter-rater reliability between experienced (12.6 ± 8.4 Nmm/degrees) and non-experienced (19.9 ± 9.2 Nmm/degrees) testers was poor (ICC = -.447, SEM = 11.29 Nmm/degrees).ConclusionsFirst MTPJ passive quasi-stiffness can be quantified from torque and angular displacement measurements using simple equipment in a clinical setting. The tester’s experience affected the consistency in joint quasi-stiffness measurements.Electronic supplementary materialThe online version of this article (doi:10.1186/s13047-016-0173-2) contains supplementary material, which is available to authorized users.
Highlights
First metatarsophalangeal joint (MTPJ) mobility is commonly assessed by its angular displacement or subjectively rated as ‘hypermobile’, ‘normal’ or ‘stiff’ by a clinician
On the opposite end of the mobility spectrum, a hypermobile or unstable first MTPJ may be associated with conditions such as hallux valgus and metatarsalgia [5,6,7]
The mean difference between Session 1 and Session 2 was small as a group (0.68 Nmm/degrees), the measurement error was rather large with a standard error of measurement (SEM) of 7.7 Nmm/degrees
Summary
First metatarsophalangeal joint (MTPJ) mobility is commonly assessed by its angular displacement (joint angle) or subjectively rated as ‘hypermobile’, ‘normal’ or ‘stiff’ by a clinician. Neither of these methods is ideal because displacement alone does not take into account the force required to displace the joint and subjective evaluation is not always reliable. The first metatarsophalangeal joint (MTPJ) is the articulating joint between the first metatarsal and the proximal phalanx of the big toe It is classified as a single synovial joint that allows motion in the sagittal and transverse planes, with sagittal plane dorsiflexion being the joint’s primary movement in gait. Other uses of measuring MTPJ range of motion include screening and identification of people who may be at high risk of diabetic foot ulceration [8] and assessment of surgery outcome in patients treated for hallux valgus [9]
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