PubMed · 14788016
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J A JENSEN. 1950-10-01. [Simple finger splint].. https://pubmed.ncbi.nlm.nih.gov/14788016/
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The reduction in vibrotactile sensitivity in the fingertip is assumed to be associated with the exposure of the tissues to repetitive, non-physiological strains during dynamic loading. Experimental results demonstrated that the magnitude of a vibration-induced temporary threshold shift is dependent upon the vibration frequency of both the exposure and testing stimuli. In the present study, the frequency-dependent strain imposed on cutaneous and subcutaneous tissues of the fingertip is analyzed theoretically using a finite element model. The proposed fingertip model is two-dimensional and includes major anatomical substructures: skin, subcutaneous tissue, bone, and nail. The soft tissues (skin and subcutaneous tissues) were assumed to be nonlinearly elastic and viscoelastic, while the bone and nail were considered as linearly elastic. Simulations were performed for the contact between the fingertip and a flat surface for four different pre-compressions (0.5, 1.0, 1.5, and 2.0 mm). The frequency-dependent distributions of the dynamic strain magnitudes in the soft tissues were investigated. The model predictions indicated that the vibration exposure at a frequency range from 63 to 250 Hz will induce excessive dynamic strain in the deep zone of the finger tissues, effectively inhibiting the high-frequency mechanoreceptors; while the vibration exposure at low frequency (less than 31.5 Hz) tends to induce excessive dynamic strain in superficial layer in the tissues, inhibiting the low-frequency mechanoreceptors. These theoretical predictions are consistent with the experimental observations in literature. The proposed model can be used to predict the responses of the soft tissues in different depths to vibration exposures, providing valuable information and data that are essential for improving vibrotactile perception tests.
There are three commonly used methods of digital block anaesthesia: viz. subcutaneous, metacarpal and transthecal. A randomized, single-blinded study on 50 healthy volunteers was performed to determine time to onset, pain level and preference. Volunteers each received all three blocks, serving as their own controls. Time to onset was significantly longer (P<0.001) for the metacarpal block than for the subcutaneous or transthecal blocks. There was no significant difference in average pain level between the methods, as measured on a scale from 1 to 10. Volunteers chose the subcutaneous block (43%) as their first choice over the metacarpal block (33%) or the transthecal block (25%). The transthecal block had prolonged discomfort lasting 24 to 72 hours after injection in 20 subjects (40%). These findings suggest that subcutaneous block is effective and preferred by healthy volunteers for digital anaesthesia.
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