Chung-Li Wang

Comparison of the mechanical properties of the heel pad between young and elderly adults

OBJECTIVE To compare the mechanical properties of the human heel pad between young and aged adults. DESIGN A 7.5-MHz linear-array ultrasound transducer was incorporated into a specially designed device to measure the thickness of the heel pad under different loads. The heel pad was compressed with serial increments of 0.5kg to a maximum of 3kg and then relaxed sequentially. Then the load-displacement curve of the heel pad during a loading-unloading cycle was plotted. PARTICIPANTS Convenience sample of 33 volunteers without heel problems, aged 18 to 78 years, were divided into young (less than 40 years) and elderly (older than 60 years) groups. MAIN OUTCOME MEASURES Unloaded heel-pad thickness, compressibility index, stiffness, and energy dissipation ratio were calculated from the load-displacement curves. Students t-test was used to compare the mechanical properties of the heel between these two groups. RESULTS The average unloaded heel-pad thickness was 1.76+/-.20cm in the young group and 2.01+/-.24cm in the elderly group (p < .001). The average compressibility index was 53.3%+/-7.7% in the young group and 61.3%+/-5.5% in the elderly group (p < .001). Energy dissipation ratio representing shock absorbency of the heel pad, was 23.7%+/-6.9% in the young group and 35.3%+/-10% in the elderly group (p < .001). CONCLUSION Unloaded heel-pad thickness, compressibility index, and energy dissipation ratio of the heel pad were significantly increased in the elderly group, indicating loss of the elasticity of the heel pad. The loss of elasticity may be responsible for the higher incidence of heel injury in elderly individuals.

Ultrasound evaluation of plantar fasciitis

OBJECTIVE To investigate the sonographic features of plantar fasciitis (PF). METHODS High-resolution ultrasound was used to measure the thickness and echogenicity of the proximal plantar fascia and associated heel pad thickness for 102 consecutive patients with PF (unilateral: 81, bilateral: 21) and 33 control subjects. RESULTS The mean thickness of the plantar fascia was greater on the symptomatic side for patients with bilateral and unilateral PF than on the asymptomatic side for patients with unilateral PF, and also control subjects (5.47+/-1.09, 5.61+/-1.19, 3.83+/-0.72, 3.19+/-0.43 mm, respectively, p<0.001). A substantial difference in thickness between the asymptomatic side of patients with unilateral PF and control subjects was also noted (p=0.001). The heel pad thickness was not show different between control subjects and patients with PF. The incidence of hypoechoic fascia was 68.3% (84/123). Other findings among the patients from our test group included intratendinous calcification (two cases), the presence of perifascial fluid (one case), atrophic heel pads (one case), and the partial rupture of plantar fascia (one case). CONCLUSION Increased thickness and hypoechoic plantar fascia are consistent sonographic findings in patients exhibiting PF. These objective measurements can provide sufficient information for the physician to confirm an initial diagnosis of PF and assess individual treatment regimens.Objective: To investigate the sonographic features of plantar fasciitis (PF). Methods: High-resolution ultrasound was used to measure the thickness and echogenicity of the proximal plantar fascia and associated heel pad thickness for 102 consecutive patients with PF (unilateral: 81, bilateral: 21) and 33 control subjects. Results: The mean thickness of the plantar fascia was greater on the symptomatic side for patients with bilateral and unilateral PF than on the asymptomatic side for patients with unilateral PF, and also control subjects (5.47¡1.09, 5.61¡1.19, 3.83¡0.72, 3.19¡0.43 mm, respectively, pv0.001). A substantial difference in thickness between the asymptomatic side of patients with unilateral PF and control subjects was also noted (p~0.001). The heel pad thickness was not show different between control subjects and patients with PF. The incidence of hypoechoic fascia was 68.3% (84/123). Other ®ndings among the patients from our test group included intratendinous calci®cation (two cases), the presence of perifascial ̄uid (one case), atrophic heel pads (one case), and the partial rupture of plantar fascia (one case). Conclusion: Increased thickness and hypoechoic plantar fascia are consistent sonographic ®ndings in patients exhibiting PF. These objective measurements can provide suf®cient information for the physician to con®rm an initial diagnosis of PF and assess individual treatment regimens.

Contact areas and pressure distributions in the subtalar joint.

We investigated how foot position and ankle arthrodesis affect the contact characteristics of the subtalar joint. Nine fresh-frozen specimens of amputated lower legs were used. Pressure-sensitive films were inserted into the anterior and posterior articulation of the subtalar joint. The contact areas and pressure for various foot positions and under axial loads of 600, 1200, and 1800 N were determined based on the gray level of the digitized film. In neutral position and under a 600 N load, the maximum contact pressure in the subtalar joint was 5.13 +/- 1.16 MPa. The contact area (1.18 +/- 0.35 cm2) was only 12.7% of the whole subtalar articulation area (9.31 +/- 0.66 cm2), and the total force (348.5 +/- 41.7 N) transmitted via this contact area was about 58% of the applied load (600 N). Dorsiflexion of the foot increased the contact area and the force transmitted, but decreased the average contact pressure in the subtalar joint, while the reverse occurred in plantar flexion. Eversion increased the subtalar contact stress, whereas inversion up to 10 degrees decreased it. Ankle joint arthrodesis shifted the contact areas in the subtalar joint posteriorly in all inversion/eversion positions. Moreover, total force transmitted through the subtalar joint as well as the contact pressure increased.

Sonographic detection of occult fractures in the foot and ankle

The purpose of this retrospective study was to determine whether high‐resolution sonography can aid in the diagnosis of radiographically occult fractures in the foot and ankle.

Altered heel-pad mechanical properties in patients with Type 2 diabetes mellitus

SUMMARY

ELASTICITY OF HUMAN VOCAL FOLDS MEASURED IN VIVO USING COLOR DOPPLER IMAGING

Noninvasive measurement of human vocal fold (VF) vibratory length was made during normal phonation to calculate the corresponding elasticity. A fixed-ends rubber string phantom that was driven by a vibrating motor was built to simulate the horizontal VF movement. The vibratory artefact of color Doppler imaging (CDI) was used to characterize and quantify the high-frequency tissue vibration with small amplitude. Because the frequency and the length of vibrating VFs were obtained simultaneously, the stress-strain relation and the Youngs moduli of the VFs could be calculated. For the six vocally normal adult volunteers (3 M, 3 F, ages from 19 to 51 years old), the effective vibrating lengths of the vocal fold in low pitch were about 1.4 to 1.6 cm and 1.3 to 1.5 cm for men and women, respectively. The VFs lengths extended to about 1.7 to 1.8 cm in pitch over an octave higher and the stress-strain relation was nonlinear. However, in the range of lower pitch, the VF stress was relatively linear with respect to the strains and the Youngs moduli were about 30 to 120 kPa in men and 120 to 300 kPa in women.

Correlation of clinical and ultrasonographic features in congenital muscular torticollis

OBJECTIVE To find the relationship between the ultrasonographic pictures and the clinical features of patients with congenital muscular torticollis (CMT). DESIGN Prospective survey of patients with clinically suspected CMT by high-resolution ultrasonography. SETTING Rehabilitation department of a tertiary care center. PARTICIPANTS Two hundred fifty-six CMT patients, from the ages of 9 days to 16yrs, with a mean follow-up period of 6.7 months. MAIN OUTCOME MEASURES Correlation of the ultrasound appearance of the involved sternocleidomastoid (SCM) muscles with clinical features. The pathologic findings in diseased muscles from patients who underwent surgical intervention were also evaluated. RESULTS Muscle abnormalities were identified ultrasonographically in 218 CMT patients (85%) and were classified into four types: a fibrotic mass in the involved muscle (type I, 15%); diffuse fibrosis mixing with normal muscle (type II, 77%) and without normal muscle in the involved muscle (type III, 5%); and a fibrotic cord in the involved muscle (type IV, 3%). Compared with type I patients, type IV patients were more likely to undergo surgical treatment (odds ratio = 31.54, p = .0196). Type III patients were more likely to undergo surgical treatment, although this tendency was not statistically significant. CONCLUSION Ultrasonography can precisely identify pathologic changes in the involved SCM muscle of CMT patients. Type III and IV patients are more likely to require surgical intervention.

Noninvasive assessment of the viscoelasticity of peripheral arteries

Currently used methods of examining the mechanical properties of blood vessel walls are either indirect or invasive, or measure vessel diameter and pressure waveforms at different sites. We developed a noninvasive technique to assess the mechanical properties and viscoelasticity of peripheral arteries. The pressure-strain elastic modulus (Ep) and the viscoelastic properties (energy dissipation ratio, EDR) of the common carotid artery (CCA), brachial artery (BA), radial artery (RA) and dorsalis pedis artery (DPA) were determined by means of palpating pressure and diameter distension waveforms extracted from high-resolution ultrasonography. The methodology was validated in vitro using an elastic tube phantom, as well as in vivo. In vivo study in 10 healthy volunteers (mean age 22 y) showed that the pressure-diameter curves were nonlinear, with an inflection at about 85-90 mmHg, and routed clockwise with slight hysteresis. The CCA (n = 5) had a mean diameter of 6.74 mm and the pulsatile diameter distension was 12.2%. The Ep calculated at the CCA was 0.44 x 10(6) dyne/cm2 with an EDR of 7.18%. The BA, RA and DPA (n = 10) had mean diameters of 3.91 mm, 2.21 mm and 2.12 mm; arterial strains of 4.60%, 4.25% and 8.91%; mean Ep of 1.39, 1.45, 0.90 x 10(6 )dyne/cm2; and mean EDRs of 6.34%, 6.15% and 5.60%, respectively. The method presented is relatively simple to implement clinically and has potential as a new diagnostic tool for detecting local vascular changes.

Ultrasonographic Examination of the Posterior Tibial Tendon

The posterior tibial tendons (PTTs) of 16 patients with PTT dysfunction and 10 age-matched healthy subjects were examined ultrasonographically, using a 10-MHz linear-array transducer. Normal PTTs appeared hyperechoic (more echogenic) and oval, with an average diameter of 7.8 mm × 3.7 mm at the medial malleolar level. Degenerated PTTs appeared hypoechoic (less echogenic) and swollen (9.8 mm × 5.0 mm). Peritendinitis presented as a hypoechoic rim on the longitudinal sonogram (along the long axis of the tendon) and a “target sign” (hyperechoic central structure with a hypoechoic halo) on the transverse sonogram (at the right angle to the long axis of the tendon). Complete rupture of the PTT revealed an empty tibial groove at the level of the medial malleolus on the transverse sonogram and a wavy fibril pattern over the distal end on the longitudinal sonogram. Compared with the operative findings or the results of the magnetic resonance imaging, ultrasonography was sensitive and specific in diagnosing tenosynovitis and complete rupture of the PTT.

Reliability and Relationship Between 2 Measurements of Transversus Abdominis Dimension Taken During an Abdominal Drawing-in Maneuver Using a Novel Approach of Ultrasound Imaging

STUDY DESIGN Reliability study of clinical measurement. OBJECTIVES The primary purpose was to develop a reliable method for measuring muscle length changes of the transversus abdominis (TrA) during contraction. The secondary purpose was to investigate the relationship between changes in thickness and length (as indicated by the lateral sliding of the anterior muscle-fascia junction) of the TrA muscle during an abdominal drawing-in maneuver. We also provide data on between-day reliability of change in thickness (ΔT) of the TrA. BACKGROUND Ultrasound imaging measurements of TrA thickness at rest (Thr) and during maximal contraction (Thm) have been shown to be reliable. However, limited data exist on quantifying changes in TrA length (as indicated by the lateral sliding of the muscle-fascia junction [Δx]) and ΔT during contraction. METHODS Eighteen healthy adults (mean ± SD age, 22.6 ± 2.5 years) participated in this study. Brightness mode ultrasound images of the TrA were collected at rest and during an abdominal drawing-in maneuver. Subjects were examined by the same examiner twice within a 48-hour period. ΔT, ΔT/Thr, Thr, Thm, and Δx of the TrA were calculated. Medial-lateral movement of the transducer during measurement was corrected through a custom-written program that used an internal marker created by an echo-absorptive thread attached to the skin. Intraclass correlation coefficients (ICC3,1), within-subject coefficient of variance, and standard error of measurement were calculated. The relationship between ΔT and adjusted Δx of the TrA muscle was investigated. RESULTS The ICC values for Thr, Thm, and ΔT of the TrA muscle were greater than 0.75, with the exception of the left ΔT (0.62) and left ΔT/Thr (0.49). After adjusting for medial-lateral motion of the transducer, the ICC values of adjusted Δx were above 0.75, and the within-subject coefficient of variance was below 10%. There was no significant correlation between ΔT and adjusted Δx of the TrA. CONCLUSION Ultrasound imaging measurements of TrA thickness and length change were shown to be reliable using a novel method to control for medial-lateral transducer motion. Measuring different but unrelated dimensional changes in the TrA might provide further insight as to the function of the TrA.