Biomedical subjects

I T Chu

Publications and source records attributed to I T Chu.

5 recordsLinked to original sources

PubMed2001

Experimental flatfoot model: the contribution of dynamic loading.

The goal of this study was to determine if the application of muscle forces (simulating the dynamic phase of the midstance part of gait) had an effect on flatfoot deformity. We created a flatfoot model in each of seven cadaver foot specimens by grasping the Achilles, peroneus longus, peroneus brevis, flexor digitorum longus, and flexor hallucis longus tendons with soft-tissue vice clamps connected via wire cables to pneumatic cylinders. The experiment included four stages: 1) initial static axial loading; 2) axial loading after 3,000 load cycles (average, 735 N; range, 70 to 1400 N); 3) axial loading after releasing the spring ligament and plantar fascia; and 4) axial loading after an additional 3,000 load cycles. At each stage, both static (with axial loading only) and dynamic (axial loading with tensioning of the tendons to simulate the muscle forces at midstance) conditions were evaluated radiographically. No change was observed between the static and dynamic conditions in the first two phases of the experiment. After the third phase, changes in the talar-first metatarsal angle and the height of the medial cuneiform were noted, particularly in the dynamic condition. These and additional radiographic changes were magnified in the fourth phase, but only in the dynamic condition. We concluded that, to create an effective flatfoot model, the medial structures, including the spring ligament and possibly the plantar fascia, must be severed. Cyclic loading of the foot further increased the arch flattening, and this effect was magnified by dynamic loading.

Aged↗

PubMed2001

The contribution of the medial calcaneal osteotomy to the correction of flatfoot deformities.

HYPOTHESES/PURPOSE: The success of the medial displacement calcaneal osteotomy in correcting flatfoot deformities is likely to be the result of a shift of the Achilles tendon forces on the hindfoot. The purpose of this study was twofold: 1) to define the contribution of the Achilles tendon to the flatfoot deformity, and 2) to define the effect of a calcaneal medial displacement osteotomy. METHODS: We used six different experimental dynamic stages: 1) intact foot without Achilles loading; 2) intact foot with Achilles loading; 3) flatfoot without medial calcaneal displacement osteotomy and without Achilles loading; 4) flatfoot without medial calcaneal displacement osteotomy but with Achilles loading; 5) flatfoot with medial calcaneal displacement osteotomy but without Achilles loading; and 6) flatfoot with medial calcaneal displacement osteotomy and with Achilles loading. The experimental flaffoot was developed by releasing the posterior tibial tendon, spring ligament, and plantar fascia and applying 7,000 cycles of axial fatigue load (range, 700 to 1,400 N; 1-Hz frequency). To simulate the phase of midstance, the peroneus longus, peroneus brevis, flexor digitorum longus, and flexor hallucis longus tendons were grasped by clamps, connected to pneumatic actuators, and loaded with precalculated forces. Anteroposterior and lateral radiographs were obtained for each stage on which the following measurements were made: talonavicular coverage angle, talar-first metatarsal angle, talocalcaneal angle, and height of the medial cuneiform. These measurements were compared with a one-way ANOVA. RESULTS: Between stages 1 and 2, all measurements were statistically insignificant. Between stages 3 and 4, for all measurements, Achilles tendon loading aggravated the flatfoot deformity (p < 0.05). After medial calcaneal osteotomy (stages 5 and 6), the Achilles tendon contributed less to the arch-flattening. We found that the medial displacement osteotomy plays an important role in reducing and/or delaying the progress of flatfoot deformity. CONCLUSIONS/SIGNIFICANCE: In the flatfoot, loading of the Achilles tendon increases the deformity. Medial calcaneal osteotomy significantly decreases the arch-flattening effect of this tendon and therefore limits the potential increase of the deformity.

Achilles Tendon↗

PubMed2000

Six first metatarsal shaft osteotomies: mechanical and immobilization comparisons.

Because malunion (usually with dorsal elevation of the first metatarsal) has been reported after the treatment of severe hallux valgus deformities by proximal osteotomies, the current study was designed to compare the sagittal stability of six different metatarsal shaft osteotomies: the proximal crescentic, proximal chevron, Mau, Scarf, Ludloff, and biplanar closing wedge osteotomies. A plate was used in the biplanar closing wedge osteotomy; all others used screws for fixation. Ten fresh-frozen, human anatomic lower extremity specimens were used for each osteotomy. Failure loads were measured as units of force (newtons) and converted to pressure (kilopascals). Then the F-Scan system, which uses a thin insole to measure plantar pressure, was used to evaluate the pressure under the first metatarsal of seven volunteers using four types of shoes. According to the results, in patients with normal bone stock who are compliant, any of the four shoe types tested may be used after a Ludloff, Scarf, biplanar wedge (plantar screw fixation), or Mau osteotomy, but the wedge-based shoe should be used after a proximal crescentic or chevron osteotomy or for patients with severe osteopenic bone.

Biomechanical Phenomena↗

PubMed1999

Unruptured congenital aneurysm of the sinus of Valsalva presenting with pulmonary stenosis.

Congenital aneurysm of the sinus of Valsalva is a rare cardiovascular anomaly. It is usually silent until rupture occurs. The natural history of unruptured aneurysm of the sinus of Valsalva is still not clear, and the therapeutic strategy is uncertain. Here we reported a case of unruptured aneurysm of the sinus of Valsalva which was correctly diagnosed before invasive diagnostic procedures. A 30-year-old female noted mild palpitation and dyspnea for 1 month. Physically, a grade 3/6 systolic ejection murmur at upper left sternal border was detected. Echocardiography revealed dilatation and irregular protrusion of the right sinus of Valsalva encroaching on right ventricular outflow tract to cause obstruction. With these findings, unruptured aneurysm of the sinus of Valsalva with pulmonary stenosis was diagnosed. Cardiac catheterization and angiography confirmed the diagnosis. The aneurysm was repaired with a Dacron patch with good results. It is concluded that sinus of Valsalva aneurysm can be diagnosed by echocardiography before its rupture so as to render a proper management for this potentially life-threatening anomaly.

Adult↗

PubMed1997

Transcatheter closure of a huge pulmonary arteriovenous fistula with embolization coils.

A 46-year-old female with bilateral pulmonary arteriovenous fistulas was treated with Gianturco coil occlusion. The small right lung fistula was closed with a 6 mm coil, whereas the huge left lung fistula was occluded with three coils (one 10-mm and two 8-mm). Angiography 3 d later demonstrated recanalization of the left fistula. Two 8 mm coils were inserted to achieve complete obstruction again. She developed pulmonary infarction in the left lung 2 d later, which recovered without sequelae. We conclude that coil embolization for huge pulmonary arteriovenous fistula is feasible but may result in pulmonary infarction.

Adult↗