Metatarsophalangeal Joint

The initial step, performed during a 2-day exercise, aimed at evaluating intraobserver and interobserver reliability for scoring static images and scoring images acquired in real-time while scanning patients.
Reading static images (day 1). Static images, representing a broad range of different degrees of synovitis in the metacarpophalangeal (MCP), wrist, proximal interphalangeal (PIP) and metatarsophalangeal joints (MTP) of patients with RA attending the Rheumatology Department of Ambroise Paré Hospital in Boulogne-Billancourt (France) were anonymised by the convenor (MADA). Images were obtained using the preliminary OMERACT definition for synovitis which includes both GS (SH and effusion) and PD findings. Images were acquired according to the EULAR recommendations16 (link) with a longitudinal scan obtained using either a dorsal or volar (plantar) view. Seventeen musculoskeletal sonographers (from Denmark, France, Germany, Hungary, Ireland, Italy, Netherlands, Spain, UK and USA) simultaneously but independently scored the images, which were presented randomly presented with 60 s for evaluating each image. No patient information was made available. Participants were asked to score GS and PD using both a binary (presence/absence) and SQ grading from 0 to 3 (normal, minimal, moderate, severe), according to their own daily practice, on a preprinted data collection sheet.
Acquiring and reading images (day 2). A practical exercise was then conducted the following day scanning and scoring synovitis. Eight patients with RA17 (link) were recruited from the same Rheumatology Department each having only mild to moderate hand deformities in order to eliminate possible acquisition difficulties due to severe structural deformities including ankylosis. The study was conducted in accordance with the Declaration of Helsinki and each participant gave written informed consent. The examinations were performed on the same day, in the same room, using eight identical machines (Technos MPX - Esaote Biomedica, Genoa, Italy) equipped with a 10–14 MHz broadband linear array transducer. The machines were calibrated with identical Doppler settings (frequency of 10.1 MHz, pulse repetition frequency of 750 Hz and Doppler gain of 50–53 dB). In this way, the impact of machines on the results was minimised. Fourteen rheumatologists who participated on the first day, in step 1, participated on the second day; all were blinded to the clinical details of the patients (ie, presence or not of active disease). Each patient was assigned to one machine and the sonographers then rotated from one machine to the next in a predefined sequence with 10 min allocated for scanning and recording the findings on a standard score sheet. In each patient, the second to fifth MCP and second to fifth PIP joints were scanned bilaterally using a GS and PD longitudinal scan in the midline of the joint on both the dorsal and volar aspects. Sixteen MCP joints were scanned twice in order to assess the intraobserver reliability.

The first stage of the screening protocol involved two clinical measures of foot posture; (i) the arch index [9 (link)], and (ii) normalised navicular height truncated [18 (link)]. These 'ratio' measurements have moderate to high correlations with angular measurements derived from radiographs [11 (link),14 (link),19 (link)], which provide the most valid representation of skeletal foot alignment [12 (link)]. Although the arch index and normalised navicular height measurements have comparable reliability to other measures of arch height, these were selected because of their ease of use and demonstrated validity with skeletal alignment measured via radiographs [12 (link)]. Additionally, the arch index is sensitive to age-related changes in foot posture [7 (link)] and is strongly associated with both maximum force and peak pressure in the midfoot during walking [20 (link)]. The primary purpose of using the clinical tests in this study was to avoid unnecessary referral of participants for radiographic assessment.
The arch index was calculated as the ratio of area of the middle third of the footprint to the entire footprint area not including the toes, with a higher ratio indicating a flatter foot [9 (link)] (Figure 3). The footprint was taken using carbon paper and a graphics tablet was used to calculate the surface area in each third of the foot.
Normalised navicular height truncated is the ratio of navicular height relative to the truncated length of the foot. Navicular height is the distance measured from the most medial prominence of the navicular tuberosity to the supporting surface. Foot length is truncated by measuring the perpendicular distance from the first metatarsophalangeal joint to the most posterior aspect of the heel [18 (link)], with a lower normalised navicular height ratio indicating a flatter foot (Figure 4).
To determine normal values for the arch index and normalised navicular height, we requested and were provided with raw foot posture measurements from Scott and colleagues [7 (link)] comprising data from 50 healthy young adults (26 female and 24 male with a mean age ± SD of 20.9 ± 2.6 years). The participants reported on by Scott and colleagues [7 (link)] were of similar age to the target participants for our study (Figure 1).
For the normal-arched foot study, participants qualified for the second stage of the screening assessment involving radiographic evaluation when either the arch index and normalised navicular height scores fell within ± 1 standard deviation (SD) of the mean values adapted from Scott and colleagues [7 (link)] (Figure 1). A threshold of ± 1 SD was selected as the 'normal limits' of several human physiological and anthropometric characteristics are frequently defined to lie within 1–2 standard deviations of the population mean [21 ].

Two models, i.e., generic-scaled and personalized, were created for each participant and used to perform MSK simulations with OpenSim 4.2 to estimate muscle and joint contact forces acting on the femur (Delp et al., 2007 (link); Steele et al., 2012 (link)). For the generic-scaled models, the generic ‘gait2392’ OpenSim model (Delp et al., 2007 (link)) with locked metatarsophalangeal joints was linearly scaled to fit to the participants’ anthropometry based on the location of surface markers (Kainz et al., 2017 (link)). For the personalized model, the Torsion Tool (Veerkamp et al., 2021 (link)) was used to modify the femoral geometry in the ‘gait2392’ model to match each child’s NSA and AVA before scaling the model. The maximum isometric muscle forces of all models were scaled based on the ratio of the body mass between the participant’s model and unscaled reference model (Eq. (1)) (van der Krogt et al., 2016 (link); Kainz et al., 2018 (link)). In summary, we had two models for each participant which were exactly equivalent except for the femoral geometry and corresponding muscle paths and attachments of muscles. ${\mathit{F}}_{\mathit{s}\mathit{c}\mathit{a}\mathit{l}\mathit{e}\mathit{d}}={\mathit{F}}_{\mathit{g}\mathit{e}\mathit{n}\mathit{e}\mathit{r}\mathit{i}\mathit{c}}*{\left({\mathit{m}}_{\mathit{s}\mathit{c}\mathit{a}\mathit{l}\mathit{e}\mathit{d}}/{\mathit{m}}_{\mathit{g}\mathit{e}\mathit{n}\mathit{e}\mathit{r}\mathit{i}\mathit{c}}\right)}^{\left(\mathbf{2}/\mathbf{3}\right)}$
All models and the corresponding gait analysis data were used to calculate joint angles, joint moments, muscle forces and joint contact forces using inverse kinematics, inverse dynamics, static optimization by minimizing the sum of squared muscle activations and joint reaction load analyses, respectively. Knee and ankle joint markers were only used for scaling and excluded during inverse kinematics. The remaining markers were weighted equally. Maximum marker errors and root-mean-square errors were accepted if less than 4 cm and 2 cm, respectively, as recommended by OpenSim’s best practice recommendations (Hicks et al., 2015 (link)). Additional analyses were performed to identify muscle attachments on the femur and obtain the effective directions of muscle forces (van Arkel et al., 2013 (link)). The mean waveform of the resultant HCF from all trials was calculated and the trial with the lowest root mean square difference to the mean waveform was selected as a representative loading condition. Similar to previous studies (Yadav et al., 2016 (link); Kainz et al., 2020 (link)) nine load instances were selected based on the HCF peaks and the valley in-between during the stance phase. The HCF and muscle forces acting on the femur during the nine load instances were used as loading conditions for FE analysis.

All patients with T2DM were asked whether they had numbness, pain (prickling or stabbing, shooting, burning or aching pain), and paresthesia (abnormal cold or heat sensation, allodynia and hyperalgesia) in the toes, feet, legs or upper-limb. Then, an experienced physician performed the neurologic examination which included vibration, light touch, and achilles tendon reflexes on both sides in the knee standing position (as being either presence or weakening or loss). Vibration perception threshold (VPT) was assessed at the metatarsophalangeal joint dig I using a neurothesiometer (Bio- Thesiometer; Bio-Medical Instrument Co., Newbury, OH, USA). First, the patients were informed how to know the vibration sensation is felt by gradually turning the amplitude from zero to maximum, then the test began again from zero and they were asked to say the moment that they first felt it. Measurements were made on the planter aspect of the big toe bilaterally, three times consecutively for each big toe. The median of three readings is accepted as the VPT value of that measurement (35 (link)). Sensitivity to touch was also tested using a 5.07/10-g Semmes-Weinstein monofilament (SWM) at four points on each foot: three on the plantar and one on the dorsal side. The 10-g SWM was placed perpendicular to the skin and pressure was applied until the filament just buckled with a contact time of 2 s. Inability to perceive the sensation at any one site was considered abnormal (36 (link), 37 (link)). DPN was defined as VPT ≥25 V and/or inability to feel the monofilament (35 (link)), and then participants were divided into DPN group and no DPN group.
Ankle brachial index (ABI) was measured noninvasively by a continuous-wave Doppler ultrasound probe (Vista AVS, Summit Co., USA) with participants in the supine position after at least 5 min of rest. Leg-specific ABI was calculated by dividing the higher SBP in the posterior tibial or dorsalis pedis by the higher of the right or left brachial SBP (33 (link), 38 (link)). Patients were diagnosed as having PAD if an ABI value <0.9 on either limb (33 (link), 38 (link)).
DFU was defined as ulceration of the foot (distally from the ankle and including the ankle) associated with neuropathy and different grades of ischemia and infection (39 (link)).