Citations

Ligaments surrounding the hindfoot joints play an important role in hindfoot stability. This in vitro study investigated anatomical and biomechanical characteristics of nine major ligamentous structures, including length and orientation at neutral position and physiological elongation with the foot in five different positions relative to the neutral position. The results showed that ligament elongation depended on the ligament length, orientation in neutral position, and movement of bones to which they were attached.

We studied six fresh frozen cadaver feet to define the three-dimensional motion of the hallux proximal phalanx in relation to the first metatarsal and to describe the contact features of the first metatarsophalangeal joint. Six tendons to the hallux were loaded to simulate dynamic loading of the hallux. A magnetic tracking system was used to monitor the three-dimensional movement of the proximal phalanx while the toe position was changed from a neutral position to full extension by adjusting the tendon loads. The average surface area was 0.38 ± 0.08 cm 2 in the neutral position; it decreased with toe extension and was the lowest (0.04 ± 0.03 cm 2 ) at the full extension position. Contact distribution of the proximal phalanx did not change substantially throughout the arc of motion. However, for the metatarsal articular surface, the contact distribution shifted dorsally with increasing degrees of extension. These data are consistent with the observation that chondral erosions associated with hallux rigidus and degenerative arthritis initially affect the dorsal articular surface of the metatarsal, and implant arthroplasty often fails from component loading dorsally. The current technique of determining joint contact characteristics is applicable not only for the first metatarsophalangeal joint but also other joints that have not been studied because of shortcomings with more conventional methods.

A cadaver study was performed to determine the effect of the posterior tibial tendon (PTT) on the stability of the foot in simulated midstance phase of gait. Thirteen fresh-frozen human foot specimens were used. Loads were applied axially and to each tendon. Three-dimensional positions of tarsal bones before and after tendon loading were determined with the use of a magnetic tracking device. Significant differences in tarsal bone positions were observed with application of loads to the Achilles, posterior tibial, flexor digitorum longus, peroneus longus, and peroneus brevis tendons at the metatarsotalar, calcaneotalar, and talotibial joints and in overall arch height. These tendon loads caused position changes toward arch flattening or mild pes planus deformity. Significant differences in tarsal bone positions were observed with PTT loading compared with no PTT loading in metatarsotalar, calcaneotalar, and talotibial levels as well as arch height. The PTT caused position changes toward restoring the arch alignment. These data suggest that the PTT is an important stabilizer of the arch of the foot.

The change in position of the bones of the foot was studied in three dimensions after plantar fascia release in intact and destabilized feet. Fifteen fresh-frozen human foot specimens were used. Physiologic loads of 445 newtons were applied axially to simulate standing at ease, and the three-dimensional position of tarsal bones was determined with a magnetic tracking device. The positions were presented in the form of screw axis displacements, quantitating rotation, and axis of rotation orientation. After fasciotomy in the six intact feet, significant differences in rotation were observed at the talotibial and calcaneotalar levels. After fasciotomy in the four unstable feet with three supporting elements sectioned, significant differences in position were observed at the talotibial joint and a significant decrease in arch height was observed. After fasciotomy in the five unstable feet with five supporting elements sectioned, significant differences in rotation were observed at the talotibial joint (mean, 5.5 ± 1.6° P = 0.001), calcaneotalar joint (mean, 6.1 ± 2.1° P = 0.003), and metatarsotalar level (mean, 9.3 ± 4.1° P = 0.007). The average decrease in arch height was 7.4 ± 4.1 mm ( P = 0.015). Displacement of all joints tested occurred after fasciotomy, with rotation about all three axes. These changes in displacement were more pronounced in unstable or destabilized feet. The data suggest that operations involving fasciotomy affect arch stability and should not be performed in patients with evidence of concomitant pes planus deformity, because of the likelihood of further deformation.

We studied 15 cadaver feet to determine three-dimensional motion of selected tarsal bones under axial loading at three different loading levels. We determined the motion of individual joints and also the rotation of the tarsal bones in relation to the tibia. Joint rotations increased consistently with higher loads. The navicular-talar joint had the greatest total screw axis rotation, which averaged 9.4° ± 2.2° at 667 N of load, followed by the first metatarsal-navicular (mean, 7.2° ± 1.5°), talar-tibial (mean, 5.2° ± 1.6°), and calcaneal-talar (mean, 4.4° ± 1.7°) joints. The observed changes indicate the need for assessment of foot and ankle alignment clinically and radiologically while the patient is weightbearing.

Material properties of the plantar aponeurosis were determined by a two-dimensional video tracking method to simultaneously measure the aponeurosis deformation. Failure loads averaged 1189 ± 244 N and were higher in men. Average stiffness of the intact fascia was 203.7 ± 50.5 N/mm at a loading rate of 11.12 N/sec and it did not vary significantly for the loading rates of 11.12 to 1112 N/sec. The high tensile loads required for failure were consistent with clinical and biomechanical studies and indicated the importance of the aponeurosis in foot function and arch stability.

In spite of the common occurrence of pes planus and multiple operations that have been reported to relieve the associated symptoms, there is little published on the relative contribution of various structures to stabilization of the arch of the foot. Twelve fresh-frozen human cadaveric feet were loaded along the tibial axis with compressive loads of 230, 460, and 690 newtons with the specimens intact and after sequential sectioning of plantar fascia, plantar ligaments, and spring ligament. Structures were sectioned in six different sequences and changes in vertical and horizontal dimensions of the medial arch were measured. The highest relative contribution to arch stability was provided by the plantar fascia, followed by plantar ligaments and spring ligament. Plantar fascia was a major factor in maintenance of the medial longitudinal arch. Its division in the cadaveric feet decreased arch stiffness by 25%.

AbstractPurposeThe goals of this study were to: (1) establish a range of the performance of four restorative systems for posterior single‐tooth crowns under single load to fracture submerged in an aqueous environment, (2) identify restorative system(s) of interest to be examined in the second study phase under sliding contact step‐stress fatigue as full‐contour anatomically appropriate single posterior tooth restoration(s), (3) establish a range for loading/testing for phase 2.Materials and MethodsForty specimens (n = 10/group) of 2 mm uniform thickness were tested. Group 1: monolithic lithium disilicate IPS e.max Press; group 2: IPS e.max ZirPress, 0.8 mm zirconia core with 1.2 mm pressed veneering porcelain; group 3: IPS e.max ZirPress, 0.4 mm zirconia core with 1.6 mm pressed veneering porcelain; group 4: IPS InLine PoM. Specimens were bonded to a block of polycast acrylic resin on a 30° sloped surface with resin cement. Specimens were axially single loaded to failure while submerged under water.ResultsThere was a statistically significant difference (p < 0.001) in failure load among the four restorative systems. Lithium disilicate showed a mean failure load similar to mean maximum posterior bite forces (743.1 ± 114.3 N). IPS e.max Zirpress with a 0.4 mm zirconia core exhibited the lowest mean failure load (371.4 ± 123.0 N).ConclusionFracture resistance of monolithic lithium disilicate in an aqueous environment is promising and requires second phase testing to evaluate the potential of various thicknesses appropriate for posterior single tooth applications. Doubling the IPS e.max Zirpress zirconia core from 0.4 mm to 0.8 mm increased the fracture resistance of this restorative system threefold.

Background and objective Survival of patients with pancreatic adenocarcinoma is limited and few prognostic factors are known. We conducted a two-stage genome-wide association study (GWAS) to identify germline variants associated with survival in patients with pancreatic adenocarcinoma. Methods We analysed overall survival in relation to single nucleotide polymorphisms (SNPs) among 1005 patients from two large GWAS datasets, PanScan I and ChinaPC. Cox proportional hazards regression was used in an additive genetic model with adjustment for age, sex, clinical stage and the top four principal components of population stratification. The first stage included 642 cases of European ancestry (PanScan), from which the top SNPs (p≤10 −5 ) were advanced to a joint analysis with 363 additional patients from China (ChinaPC). Results In the first stage of cases of European descent, the top-ranked loci were at chromosomes 11p15.4, 18p11.21 and 1p36.13, tagged by rs12362504 (p=1.63×10 −7 ), rs981621 (p=1.65×10 −7 ) and rs16861827 (p=3.75×10 −7 ), respectively. 131 SNPs with p≤10 −5 were advanced to a joint analysis with cases from the ChinaPC study. In the joint analysis, the top-ranked SNP was rs10500715 (minor allele frequency, 0.37; p=1.72×10 −7 ) on chromosome 11p15.4, which is intronic to the SET binding factor 2 (SBF2) gene. The HR (95% CI) for death was 0.74 (0.66 to 0.84) in PanScan I, 0.79 (0.65 to 0.97) in ChinaPC and 0.76 (0.68 to 0.84) in the joint analysis. Conclusions Germline genetic variation in the SBF2 locus was associated with overall survival in patients with pancreatic adenocarcinoma of European and Asian ancestry. This association should be investigated in additional large patient cohorts.

BACKGROUND A rise or fall of cardiac troponin is a prerequisite for the diagnosis of acute myocardial infarction. Defining significant changes requires knowledge of both biological and analytical variation. The short-term biological variation of cardiac troponin in healthy individuals is 3%–48%. However, healthy individuals may not be representative for patients in whom cardiac troponin measurement is often of clinical importance. Therefore, we studied the individual variation of cardiac troponin in patients with symptoms of stable coronary artery disease. METHODS Twenty-four patients scheduled for elective coronary angiography were included. Blood samples were drawn once at enrollment and serially at six 4-h intervals on the day before coronary angiography. Cardiac troponin was measured with hs-cTn assays from Abbott Laboratories (premarket cTnI assay) and Roche Diagnostics (Elecsys® cTnT assay with two different lots). RESULTS The short-term individual variation in cardiac troponin I (cTnI) was 14%, the reference change value (RCV) 49%, and RCV-log-normal (rise/fall) 54%/−35%. The corresponding values for cTnT were 7%, 23%, and 26%/−21%. The long-term variation for cTnI was 24%, RCV 69%, and RCV-log-normal (rise/fall) 97%/−49%. The corresponding values for cTnT were 11%, 32%, and 37%/−27%. CONCLUSIONS The short-term individual variation of cardiac troponin in patients with symptoms of stable coronary artery disease is similar to the biological variation previously demonstrated in healthy individuals. Our results suggest that a change in cardiac troponin concentrations of &gt;50% can be used in attempting to diagnose acute myocardial injury. To detect significant long-term changes in cardiac troponin concentrations, larger changes will be required.