Mutsuaki Edama

Background: This study aimed to examine whether the morphology of the articular surface of the first tarsometatarsal (TMT) joint, plantar tarsometatarsal ligament (PTML), and hallux valgus angle (HVA) were associated with plane‐specific TMT joint displacement. Methods: Nine Thiel‐embalmed cadavers (18 feet) were included. HVA was measured using a goniometer. The capacity for TMT joint motion (mobility) was operationalized as displacement of the first metatarsal relative to the medial cuneiform under manual stress, measured ultrasonographically in the dorsal, plantar, and medial imaging planes. PTML morphology (length, width, and thickness) and TMT joint articular surface morphology (type classification) were assessed, and their associations with plane‐specific TMT joint displacement were analyzed. Results: No significant differences in dorsal, plantar, or medial displacement were observed between Type III and the other articular surface morphologies after adjustment for multiple comparisons. Similarly, PTML length, width, and thickness were not significantly associated with displacement in any direction. Although HVA was positively associated with plantar displacement before adjustment, this association did not remain significant after FDR correction. Conclusions: In this small exploratory cadaveric study, no statistically significant associations were identified between first TMT joint displacement and articular surface morphology, PTML morphology, or HVA after accounting for within‐cadaver clustering and multiple comparisons. These findings should be interpreted cautiously because of the small sample size and limited range of HVA severity. Level of Evidence: Level IV, Descriptive laboratory study

Retrocalcaneal bursitis is often accompanied by insertional Achilles tendinopathy. However, the mechanical effects of bursal effusion remain unclear. This study aimed to elucidate the mechanical impact of retrocalcaneal bursal effusion using Thiel-embalmed cadavers, which are known to exhibit mechanical properties comparable to those in vivo. Ten lower limbs from seven Thiel-embalmed cadavers were examined. Ultrasound-guided injection of the preservation fluid was performed to simulate retrocalcaneal bursal effusion. Ultrasonographic evaluation was conducted under three conditions based on bursal thickness: Baseline, Mild (2 ± 0.5 mm), and Severe (4 ± 0.5 mm). The dynamics of the Achilles tendon insertion during passive ankle dorsiflexion were recorded using ultrasonography. Average curvature and thickness of the Achilles tendon insertion were measured and compared between the conditions and ankle angles. In Baseline and Mild conditions, the average curvature increased from plantarflexion to dorsiflexion but remained unchanged in the severe condition. The Severe condition demonstrated a significantly greater average curvature at plantar flexion than the other conditions. The thickness significantly decreased with dorsiflexion only in the severe condition, resulting in a significantly thinner insertion at maximum dorsiflexion compared with the other conditions. Our findings suggested that Mild effusion of the retrocalcaneal bursa may not exacerbate the mechanical load of Achilles tendon insertion. In contrast, in the presence of severe effusion, the retrocalcaneal bursa may compress the Achilles tendon insertion even in the plantarflexion position, and during dorsiflexion the tendon showed deformation compatible with increased compression.

Muscle fascia is implicated to play a role in musculoskeletal pain; however, the distribution of unmyelinated nerve fibers within human fascia remains to be characterized. Conventional formalin fixation of biological tissues for long periods degrades the antigenicity of protein markers, often resulting in loss of nerve fiber immunoreactivity, limiting immunohistochemical analysis. This study aimed to examine the intrafascial distribution of immunohistochemically labeled unmyelinated nerve fibers in the muscle fascia of cadavers embalmed for 4-21 months using the Thiel-embalming method, which employs a low concentration of formaldehyde. Immunohistochemical staining of peripherin-immunoreactive (-ir) nerve fibers, representing unmyelinated C-fibers, was performed in the proximal, middle, and distal third regions of the crural fascia (CF) from 16 lower legs of eight Thiel-embalmed cadavers. The area occupied by peripherin-ir nerve fibers was quantified for each region. Peripherin-ir nerve fibers were identified in the CF of all specimens. The areas of peripherin-ir fibers were significantly greater in the middle and distal regions compared with the proximal region. Overall immunoreactivity, defined as the total area of peripherin-ir nerve fibers, was not affected by post-embalming storage duration of up to 21 months. These findings demonstrate the presence of unmyelinated nerve fibers in the human CF of Thiel-embalmed cadavers and reveal region-specific differences in their intrafascial distribution. The results provide neuroanatomical evidence supporting the potential involvement of fascia in human myofascial pain.

This study aimed to elucidate the differences between subjective and objective symptoms of edema during the menstrual cycle in female university students with regular menstruation. The study included 29 female university students with regular menstrual cycles. The menstrual cycle was categorized into the early follicular, mid-luteal, and late-luteal phases, and measurements were taken during each phase. Subjective symptoms were evaluated using body charts and the Menstrual Distress Questionnaire (MDQ) to assess the presence of edema. Objective symptoms were measured using a body composition analyzer to assess body weight, body water content, and regional water content. In the evaluation of subjective symptoms of edema using the body chart, no significant differences were observed across cycles. However, when body regions were compared, there were significantly fewer subjective symptoms in the upper arm (Rt/Lt) than in the face and trunk across all phases, while the lower leg (Rt/Lt) had significantly more subjective symptoms. The MDQ (water retention item) showed no marked differences across cycles. For objective evaluations of edema, including body weight and total body water, no significant differences were observed across cycles; however, regional water content was significantly higher in the trunk and right arm during the mid-luteal and late-luteal phases than in the early follicular phase. Our findings suggest that the location and timing of subjective edema symptoms may differ from those of objective symptoms.

Hepcidin is a key regulator of iron metabolism and has been proposed as a biomarker for detecting iron deficiency. This study examined serum hepcidin and non‐invasively measured urinary hepcidin in 260 female athletes to assess their potential utility in evaluating iron status. Urinary hepcidin/creatinine showed a strong correlation with serum hepcidin and was positively associated with ferritin, suggesting that it reflects underlying iron dynamics. Iron‐related measures, including hepcidin, showed expected differences across iron‐status categories, consistent with physiological changes from iron repletion to iron deficiency anemia. In diagnostic analyses, both serum hepcidin and urinary hepcidin/creatinine demonstrated good accuracy for identifying iron deficiency including iron deficiency anemia. Serum hepcidin yielded AUCs of approximately 0.85–0.90, while urinary hepcidin/creatinine showed AUCs around 0.85–0.88. Internal validation produced consistent confidence intervals, suggesting stable estimates. At the Youden‐optimal cutoff, both markers showed comparable performance, with sensitivities of 0.74–0.91, specificities of 0.73–0.92, and high negative predictive values (0.83–0.97). These cutoff values were derived from internally validated analyses and should be considered preliminary, requiring external validation before broader clinical implementation. These findings suggest that hepcidin‐based measures may assist in ruling out iron deficiency or guiding triage decisions. Because urinary hepcidin can be obtained non‐invasively and demonstrated performance similar to serum hepcidin, it may represent a practical screening option in athletic populations, although further external validation is needed.

This study aimed to clarify the differences in the stabilizing functions of the upper and lower fiber bundles of the anterior talofibular ligament (ATFL). Five Thiel-fixed cadavers (10 ft) were divided into an upper fiber bundle cut group (upper-cut group, 5 ft) and a lower fiber bundle cut group (lower-cut group, 5 ft). The angular conditions were set as 0-degree ankle dorsiflexion, 15-degree plantar flexion, and 30-degree plantar flexion. Anterior drawer and inversion stresses were applied using a Telos stress device at 120 N. Measurements were obtained when the upper and lower fiber bundles of the ATFL were intact (intact condition) and when either the upper or lower fiber bundle was severed (cut condition). For each group, the distance between the lateral malleolus and talus was measured using an ultrasound diagnostic device under both the intact and cut conditions and compared. Regarding anterior drawer stress, the displacement rate (%) significantly increased in both the upper- and lower-cut groups under the cut condition at 30-degree plantar flexion. Meanwhile, for the inversion stress, only the upper-cut group demonstrated a significantly increased displacement rate (%) under the cut condition at 0-degree dorsiflexion. No significant difference in either anterior drawer stress or inversion stress at any angle was observed between the two groups. Both the upper and lower fiber bundles of the ATFL may be involved in stabilizing ankle function during anterior drawer stress at 30-degree plantar flexion. In addition, the lower fiber bundle may play a role in stabilizing the ankle during inversion stress at 0-degree dorsiflexion.

Background: Reaction time is analyzed in various situations in sporting events and is reported to be so important that it can make the difference between victory and defeat. This study focused on teeth clenching resulting in remote muscle activation, and examined whether it improves performance of reaction time. This study examined the effects of clenching and clenching strength on the systemic simple reaction time. Methods: This study included 20 healthy adults with normal clenching and a right dominant foot. The task movement for the systemic simple reaction time measurement was a 30 cm forward step. The following three clenching conditions were used: no clenching without dental contact (no-bite condition), a condition in which the participants were instructed to clench with moderate strength (moderate condition), and a condition in which the participants clenching with maximum effort (max condition). The analysis items were release time, grounding time, soleus muscle (Sol) reaction time, and masseter muscle activity. Results: The max condition significantly reduced the reaction time compared with the no-bite condition. Sol reaction and grounding times showed a negative correlation between clenching strength under moderate conditions and the rate of change in reaction time under no-bite and moderate conditions. Release time exhibited no significant correlation between clenching strength under the moderate condition and the rate of change in reaction time under the no-bite and moderate conditions. The remote facilitation effect of clenching improved the systemic reaction time by producing immediate muscle activity. Conclusions: Clenching shortens the systemic simple reaction time. This finding highlights the potential importance of clenching in enhancing performance during sporting events.