Fixation Characteristics Research Articles

Assessment of Reading Behavior with an Infrared Eye Tracker after 360° Macular Translocation for Age-Related Macular Degeneration

PURPOSE. Macular translocation (MT360) is complex surgery used to restore reading in exudative age-related macular degeneration (AMD). MT360 involves retinal rotation and subsequent oculomotor globe counterrotation and is not without significant surgical risk. This study attempts to gauge the optimal potential of MT360 in restoring reading ability and describe the quality and extent of recovery. METHODS. The six best outcomes were examined from a consecutive series of 23 MT360 cases. Reading behavior and fixation characteristics were examined with an infrared eye tracker. Results were compared to age-matched normal subjects and patients with untreated exudative and nonexudative AMD. Retinal sensitivity was examined with microperimetry to establish threshold visual function. RESULTS. MT360 produced significant improvements in visual function over untreated disease and approximated normal function for reading speed and fixation quality. Relative to the comparative groups, eye tracking revealed the MT360 cohort generated a greater number of horizontal and vertical saccades, of longer latency and reduced velocity. In contrast, saccadic behavior when reading (forward and regressive saccades) closely matched normal function. Microperimetry revealed a reduction in the central scotoma with three patients recovering normal foveal sensitivity. CONCLUSIONS. Near normal reading function is recovered despite profound surgical disruption to the anatomy (retinal/oculomotor). MT360 restores foveal function sufficient to produce a single stable locus of fixation, with marked reduction of the central scotoma. Despite the limitations on saccadic function, the quality of reading saccadic behavior is maintained with good reading ability. Oculomotor surgery appears not to limit reading ability, and the results of retinal surgery approximate normal macular function.

Mechanical Comparison of Two Types of Fixation for Ludloff Oblique First Metatarsal Osteotomy

The Ludloff oblique metatarsal osteotomy is an effective method to correct hallux valgus deformity, although a number of problems have been associated with it, including inherent instability, delayed union, dorsal malunion, and fixation failure. The purpose of the present study was to compare the mechanical characteristics of fixation of the Ludloff osteotomy in 20 identical synthetic bone models, 10 fixated using 2 screws (group I) and 10 fixated using 2 screws augmented with a mini locking plate (group II). Each specimen was loaded to failure, and the mean average load to failure, stiffness, and absorbed energy to failure were compared using unpaired Student’s t test. The mean average stiffness of the Ludloff osteotomy fixed with 2 screws (group I) and with the supplementary mini locking plate (group II) was 172.7 ± 31.7 N/mm and 193.3 ± 39 N/mm, respectively ( p = .21). The mean average load to failure for groups I and II was 278.4 ± 64.4 N and 356.2 ± 77.9 N, respectively ( p = .025). The mean average energy absorbed before failure for groups I and II was 506.7 ± 206.4 Nmm and 769.8 ± 339.4 Nmm, respectively ( p = .05). The use of a medially applied supplementary mini locking plate offers a simple and effective method to improve the mechanical stability of the Ludloff oblique osteotomy.

Study on Pore Structure and Sulfur Fixation Characteristics of Alkali Industrial Waste

Pore structure of experiment alkali waste were investigated by Mercury Porosimetry, the influence of pore structure characteristics on their sulfur fixation performance were discussed, it can be found that little pores make a significant contribution to calcium utilization in the initial stage of reaction and at lower temperature, while bigger pores take effect in the later stage and at higher temperature, the range of effective aperture are different at different temperature, which respectively are from 0.005μm to 0.02μm at temperature from 1123K to 1223K and from 0.2μm to 0.3μm at temperature from 1223K to 1323K, the more pore in range of effective aperture, the better the sulfur fixation performance.

Potassium Dynamics in Calcareous Vertisols of Southern Iran

The study was conducted to evaluate different forms of K, and release and fixation characteristics of 12 representative calcareous Vertisols of southern Iran. Mineralogical analysis indicated that smectite was the main clay mineral in the Vertisols, but some Vertisols had chlorite, illite, and palygorskite, as well as smectite in the clay fraction. Soluble, exchangeable, HNO3-extractable, and total K ranged from 0.4 to 11.7 mg kg−1, 127.1 to 435.6 mg kg−1, 839.7 to 1942.4 mg kg−1, and 4971.5 to 11427.3 mg kg−1, respectively. Cumulative K released to 0.01 M CaCl2 during 1496 h ranged from 167.7 to 244.9 mg kg−1 for surface soils and from 109.1 to 198.0 mg kg−1 for subsurface soils. Generally, the studied soils fixed 14–38% of the added K. The K fixation in different soils correlated significantly (r = 0.90, n = 42, p < 0.01) with the smectite content in the clay fraction and cumulative K released correlated significantly with illite content in the clay fractions (r = 0.79, n = 42, p < 0.01). Results indicated that clay mineralogy of Vertisols is a key factor affecting dynamics of K in the soils and thereby sustainable management of K in crop production. Generally, we concluded that calcareous Vertisols in southern Iran have sufficient K for plant uptake, but with intensive crop production and without application of K fertilizers, these soils will be transformed to K depleted soils in the future. Thus, application of K fertilizers in long term management of plant production may be required.

Recent and Upcoming Innovation in the Technology of Hip Arthroscopy

The advancements in our understanding of hip anatomy and pathology have stimulated the innovation of new products and technologies in hip arthroscopy. Specialized patient-positioning systems can help optimize the limb distraction and joint access that is critical for accessing the hip joint. Guiding systems have been developed to reduce the risk of iatrogenic damage and improve the efficiency and safety by which the secondary portals are established. Suture anchors now commonly contain polylactic acid with varying isomer compositions that help control the rate with which these anchors are reabsorbed. The addition of composite anchors may potentially offer improved anchor-osseus fixation and degradation characteristics. Knotless anchors are now becoming available and hold the potential to improve the ease and speed of achieving stable anchor fixation. Specialized instruments, including flexible and maneuverable thermal probes, extra-long cannulas, and extra-long shavers, burs, drills, implants, and loose body retrieval devices have improved access to the hip joint and have expanded the spectrum of indications for arthroscopy of the hip. These aforementioned products and technologies are representative of an exciting period of growth and innovation in the armamentarium of tools available to surgeons versed in hip arthroscopy. This work explores some of the new products and technologies that have recently come to market in hip arthroscopy that have and potentially will continue to improve our ability to arthroscopically treat hip pathology.

Comparing fixation location and stability in patients with neovascular age-related macular degeneration treated with or without Ranibizumab

To compare fixation location and stability in patients with neovascular age-related macular degeneration (AMD) treated with or without ranibizumab. Patients were recruited from the Macular Clinic of the King's College Hospital in London. Two groups of patients with neovascular AMD with at least 12 months of follow-up were included in the study. The treated group was treated with ranibizumab while the untreated group did not have any treatment. Best corrected visual acuity (BCVA) with modified ETDRS chart, fixation location and stability as measured with Nidek MP1, central retinal thickness as measured by Zeiss Cirrus SD-optical coherent tomography (OCT), and lesion size as measured by Topcon TRC-50IX camera were analysed and correlated. In total, 102 eyes were included in the study with 76 in the ranibizumab-treated group and 26 in the untreated group. There were no significantly demographic differences between the two groups. However, as expected, the treated group has significantly better vision (48.5 vs 15.5 letters, P < 0.0001) and smaller lesions (10.8 vs 18.3 mm(2), P = 0.004), the central macular thickness as measured by OCT also showed a trend of normalised macular thickness (252 vs 282 microns, P = 0.07). The location of fixation was significantly more central in the ranibizumab-treated group (χ(2) 17.9, P < 0.0001) with over 50% of eyes with predominantly central fixation. Majority (84.6%) of the patients in the untreated group had predominantly eccentric fixation. Fixation stability was significantly better in the ranibizumab-treated group as compared with the untreated group, using both the software provided by the MP1 machine (χ(2) 21.8, P < 0.0001) and the mean log bivariate contour ellipse area calculated from the raw data obtained from the machine (3.64 vs 4.39 in treated and untreated group respectively, P < 0.0001). Low vision rehabilitation strategy for this group of patients in the ranibizumab era will be very different from those used in untreated patients with dense central scotoma. Further studies on the visual rehabilitation in the ranibizumab-treated patients should consider fixation characteristics of the patients.

Spatial and temporal variability in nitrogenase activity and diazotrophic community composition in coastal microbial mats

Coastal microbial mats are highly diverse micro-scale ecosystems in an environment characterized by strongly fluctuating conditions. Nitrogen (N) fixation is an important process in these often N-limited ecosystems. We investigated the characteristics of N2 fixation and the composi- tion of the N2-fixing (diazotrophic) community in 3 microbial mats situated along an intertidal gradi- ent over a period of 3 yr by using the acetylene reduction assay and by analyzing more than 800 envi- ronmental nifH sequences. In 2008, nitrogenase activity (NA) in the 3 mat types differed with respect to the daily pattern and daily integrated rates (ranging from 5 to almost 150 mmol C2H4 m -2 d -1 ). The diazotrophic community composition in the 3 mat types was also dissimilar. The nifH clone libraries at the location that was most influenced by freshwater contained mostly cyanobacterial and alphaproteobacterial sequences, whereas the other 2 locations were dominated by gamma- and deltaproteobacterial diazotrophs. These differences were attributed to the specific environmental conditions at each location resulting from their position along the intertidal gradient and likely caused the differences in the recorded patterns of N2 fixation. Moreover, in each of the mat types, a dramatic shift in the diazotrophic community was observed over a period of 2 to 3 yr. These shifts var- ied greatly between the locations. The characteristics of NA at the same location in different years also varied considerably. N2 fixation in these microbial mats was spatially and temporally variable, which was attributed to the shifts in diazotrophic community composition along the littoral gradient and during the 3 yr of investigation.

Short wavelength fundus autofluorescence versus near-infrared fundus autofluorescence, with microperimetric correspondence, in patients with geographic atrophy due to age-related macular degeneration

AimTo compare standard short-wavelength fundus autofluorescence (SW-FAF) and near infrared-wavelength fundus autofluorescence (NIR-FAF) in detecting geographic atrophy (GA) secondary to age-related macular degeneration, and its retinal sensitivity impairment.MethodsTwenty-five consecutive patients...

Meniscal repair using large diameter horizontal sutures increases fixation strength: an in vitro study

the purpose of this study was to compare the mechanical characteristics of meniscal repair fixation using horizontal sutures and two different diameter sutures under submaximal cyclic and load to failure test conditions. a 2-cm long anteroposterior vertical longitudinal incision was created in two groups of bovine medial menisci. Lesions were repaired using either #2-0 (Group 1), or #2 (Group 2) Fiberwire suture. Following repair, the lesion was extended through the posterior and anterior meniscal horns so that no tissue secured the repair site. Specimens underwent submaximal cyclic (5-50 N at 1 Hz for 500 cycles) and load to failure testing (5 mm/min crosshead speed) in a servo hydraulic device. Specimen failure mode was verified by the primary investigator. An alpha level of P < 0.05 was selected to indicate statistical significance. group 2 displayed greater load at failure (132.1 ± 54.4 N) than Group 1 (91.9 ± 26.2 N) (P = 0.02). Group 2 also displayed greater stiffness (47.1 ± 8.3 N/mm) than Group 1 (38.5 ± 10.2 N/mm) (P = 0.03). The failure mode for all specimens was suture pull-through the meniscal tissue. Larger diameter suture provided superior mechanical meniscal fixation. if horizontal suture would be used in meniscal repair, the most suitable larger diameter suture should be used.

Paradoxical Improvement of Visual Acuity in Macular Disease

Purpose: Improvement in visual acuity is often considered the best indicator of the effectiveness of a treatment in age-related maculopathy. However, during the course of the disease, the location of the patients’ preferred retinal locus of fixation may change. This can lead to an unexpected functional improvement, unrelated to treatment.Methods: From a running database of 1,369 retina patients, we identified 116 patients over 60 years of age when age-related maculopathy was diagnosed based on the following inclusion criteria: one study eye with an initial acuity of the logarithm of the minimum angle of resolution (logMAR) 0.7 or worse, a fellow eye with central fixation and a follow-up period of 3 years or more with precise documentation of the preferred retinal locus of fixation and scotoma distribution for both eyes using scanning laser ophthalmoscopy-based microperimetry.Results: We expected an improvement in the visual acuity in one eye (study eye) without the possibility of improvement due to previous or concurrent treatment in that eye. Twelve patients met the selection criteria. Over time, these patients had significant improvements in the visual acuity in the weaker study eye, characteristically accompanied by a concurrent decrease in visual acuity in the other eye, which initially had better visual acuity. Moreover, in all the study eyes, an unstable pseudo-central von Noorden fixation pattern evolved into a more stable eccentric preferred retinal locus.Conclusions: Visual acuity remains the gold standard for assessing visual functioning in age-related maculopathy when interpreted with caution. Improvements in visual acuity can occur solely due to the course of the disease in the other eye and as a result of its impact on binocular fixation characteristics. This finding has significant implications for low-vision rehabilitation and evaluation of various therapies in large long-term clinical studies.

Anti-tuberculous therapy combined with systemic corticosteroids improves retinal sensitivity in patients with active presumed tuberculous choroiditis

To investigate the efficacy of anti-tuberculous therapy and systemic corticosteroids in patients suffering from active presumed tuberculous choroiditis by the assessment of central retinal sensitivity and fixation characteristics. Six patients (six eyes) with active presumed tuberculous choroiditis were treated with anti-tuberculous therapy and systemic corticosteroids. Mean central retinal sensitivities and fixation stability and location were investigated with MP-1 microperimetry before and after treatment. After a mean follow-up of 11.33 ± 7.53 months (range 6-24 months), all eyes showed resolution of inflammation, with no recurrences, associated with a significant improvement in visual acuity (P = 0.003). At the baseline, mean central retinal sensitivities were 2.03 ± 2.46 dB (range 0.0-6.6 dB). Fixation was stable and predominantly central in three eyes, and unstable and predominantly eccentric in three eyes. After treatment at a mean of 9.33 ± 6.56 months (range 4-20 months), mean central retinal sensitivities improved to 9.65 ± 5.35 dB (range 2.4-15.2 dB) (P = 0.004) and fixation became predominantly central and stable in all eyes. Anti-tuberculous therapy combined with systemic corticosteroids improves central retinal sensitivity and fixation characteristics in patients with presumed tuberculous choroiditis.

Biomechanical research of antegrade intramedullary fixation for the metacarpal fractures

To study the biomechanical characteristics of antegrade intramedullary fixation for metacarpal fractures. From March to May 2008, both the 4th and 5th metacarpals from 25 formalin embalmed cadaver hands had three-point bending test after transverse osteotomy followed by randomly fixation with one of the following three methods: plate and screw, antegrade intramedullary K-wire, crossed K-wire. While, both the 2nd and 3rd metacarpals had torsional loading test after the same management as the 4th and 5th metacarpal had undergone. In the three-point bending test, both the maximum bending moment (M(max)) and bending rigidity (EI) of the antegrade intramedullary K-wire were comparable with those of the plate and screw, and were significantly larger than those of the crossed K-wire. In the torsional loading test, the antegrade intramedullary K-wire had a statistically smaller maximum torque (T(max)) than the plate and screw, and had a comparable T(max) with the crossed K-wire; while, the torsional rigidity (GJ) of the intramedullary K-wire was statistically weaker than that of both the plate and screw and the crossed wire. One single antegrade intramedullary K-wire can provide a satisfactory M(max) and EI for metacarpal fixation and shows relatively weak in the torsional loading test. The injured finger should be well protected to avoid torsional deformity in clinical practice.

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L−1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L−1 ammonium acetate (NH4OAc) and 1.0 mol L−1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.

A new fixation material for open-wedge tibial osteotomy for genu varum

Varus deformity of the knee is a determining factor in the development of osteoarthrosis of the medial compartment. Open wedge osteotomy corrects the deformity and has quickly become popular due to the fact that the surgical technique can be easily reproduced, it spares loss of bone tissue in the metaphysiary region, and it does not require muscle dissection, reducing the risk of lesion of the fibular nerve. The objective of this study was to evaluate the characteristics of a new fixation implant (Anthony-K plate - France Bloc S.A, CE n0499, ISO 9001, EN 46001), in terms of its clinical improvement, correction of the deformity, and slope alteration. Twenty adult patients with varus deformity were evaluated, and submitted to open wedge high tibial osteotomy using the Anthony plate, between October 2004 and November 2006. The varus deformity was corrected in all cases, and there was a significant increase in the Lysholm score. Correlation analysis has shown that the greater the preoperative varus deformity, the larger the opening wedge used. Also, the greater the initial posterior tibial slope, the larger the final posterior tibial slope (p=0.0168). There were no complications. The Anthony plate can be considered an alternative in the treatment of medial osteoarthrosis of the varus knee, enabling the correction of the deformity and improvement of the clinical picture. It occurs an increase in posterior tibial slope, similar to that observed with other fixation materials. More studies with the Anthony plate are necessary, after these encouraging results.

RETINAL FIXATION IMPAIRMENT IN DIABETIC MACULAR EDEMA

To evaluate the characteristics of retinal fixation in patients with diabetic macular edema using microperimetry. One hundred seventy nine eyes (98 patients) with untreated diabetic macular edema underwent best corrected visual acuity determination (Early Treatment Diabetic Retinopathy Study charts), digital color stereoscopic fundus photos, fluorescein angiography and Optical Coherence Tomography assessment of macula. Fixation and retinal thresholds were determined with an automatic microperimeter. Best corrected visual acuity (approximate Snellen equivalent) was: 20/25 or better in 90 (52%) eyes, 20/50 to 20/32 in 39 (22.5%) eyes, 20/200 to 20/62.5 in 35 (20.2%) eyes and inferior to 20/200 in 9 (5.2%) eyes. Fixation was central in 128 (71.51%), poor central in 26 (14.53%) and predominantly eccentric in 25 (13.97%) eyes; stable in 133 (74.3%), relatively unstable in 42 (23.46%) and unstable in 4 (2.23%) eyes. Both fixation location and stability were not significantly influenced by edema characteristics (diffuse, focal, cystoid, spongelike, with or without subfoveal neuroretinal detachment), (P > 0.05), whereas they were significantly influenced by the presence of subfoveal hard exudates, (P = 0.004 and P = 0.0046, respectively). Site and stability of fixation were significantly associated, (P < 0.0001). Retinal pseudofovea would have been covered by laser photocoagulation in 24 (47%) eyes with poorly central and predominantly eccentric fixation and in 29 (63%) eyes with relatively unstable and unstable fixation. Microperimetry shows that fixation location and stability in patients with diabetic macular edema are independent of edema characteristics, except when subfoveal hard exudates are present. Location of pseudofovea may influence treatment strategy.

Macular Sensitivity in Eyes with Central Serous Chorioretinopathy

To determine macular sensitivity and fixation characteristics in eyes with central serous chorioretinopathy (CSC) using fundus-related microperimetry. The authors reviewed 19 eyes with serous elevation within the central 10 degrees due to CSC and 15 normal healthy eyes that had undergone fundus-related microperimetry. The macular sensitivity was measured using the fundus-related microperimeter, MP-1. The bestcorrected visual acuity (BCVA), mean retinal sensitivity in the central 10 degrees (central microperimetry, cMP-1) and in the paracentral 10 degrees to 20 degrees (paracentral microperimetry, pMP-1), and fixation stability and location were determined and compared with that of control eyes. Eyes with CSC showed significantly lower logMAR BCVA (p<0.001), cMP-1, and pMP-1 sensitivity than control eyes (p<0.001, p<0.01, respectively). Eyes with CSC were not significantly different in fixation location (p=1.00) or fixation stability than control eyes (p=0.45). Fixation location was predominantly central in all eyes with CSC; fixation was stable in 17 (89%) and relatively unstable in 2 (11%). Eyes with CSC showed significantly lower retinal sensitivity not only at the central but also in the paracentral area. Even with decreased BCVA and retinal sensitivity, our patients showed central and stable fixation in their affected eyes.

Clinical evaluation of medicinal products for acceleration of fracture healing in patients with osteoporosis

Pre-clinical studies indicate that pharmacologic agents can augment fracture union. If these pharmacologic approaches could be translated into clinical benefit and offered to patients with osteoporosis or patients with other risks for impaired fracture union (e.g. in subjects with large defects or open fractures with high complication rate), they could provide an important adjunct to the treatment of fractures. However, widely accepted guidelines are important to encourage the conduct of studies to evaluate bioactive substances, drugs, and new agents that may promote fracture union and subsequent return to normal function. A consensus process was initiated to provide recommendations for the clinical evaluation of potential therapies to augment fracture repair in patients with meta- and diaphyseal fractures. Based on the characteristics of fracture healing and fixation, the following study objectives of a clinical study may be appropriate: a) acceleration of fracture union, b) acceleration of return to normal function and c) reduction of fracture healing complications. The intended goal(s) should determine subsequent study methodology. While an acceleration of return to normal function or a reduction of fracture healing complications in and of themselves may be sufficient primary study endpoints for a phase 3 pivotal study, acceleration of fracture union alone is not. Radiographic evaluation may either occur at multiple time points during the healing process with the aim of measuring the time taken to reach a defined status (e.g. cortical bridging of three cortices or disappearance of fracture lines), or could be obtained at a single pre-determined timepoint, were patients are expected to reach a common clinical milestone (i.e. pain free full weight-bearing in weight-bearing fracture cases). Validated Patient Reported Outcomes (PRO's) measures will need to support the return to normal function co-primary endpoints. If reduction of complication rate (e.g. non-union) is the primary objective, the anticipated complications must be defined in the study protocol, along with their possible associations with the specified fracture type and fixation device. The study design should be randomized, parallel, double-blind, and placebo-controlled, and all fracture subjects should receive a standardized method of fracture fixation, defined as Standard of Care.

FIXATION CHARACTERISTICS OF PATIENTS WITH MACULAR DEGENERATION RECORDED WITH THE MP-1 MICROPERIMETER

The authors examined the fixation stability patterns of people with age-related macular degeneration (AMD) using the MP-1 microperimeter and describe a method to bypass some calibration artifacts that can influence the fixation results. The preferred retinal locus (PRL) and fixation patterns of 37 eyes with AMD and the fovea's location relative to the middle of the optic disc of 10 experienced controls were measured. For the patients, fixation characteristics such as the former fovea's location, PRL distance, and fixation stability were analyzed. For the controls, the mean foveal distance temporal to the middle of the optic disc was 15.5 deg +/- 0.86 deg horizontally and -1.33 deg +/- 0.71 deg vertically. Thirty-one out of 37 PRLs occurred in the upper and right quadrants of the retina. There were significant positive correlations between fixation stability and PRL distance from the former fovea. Time since diagnosis and acuity also showed positive correlations with fixation stability and PRL distance from the fovea. The authors recommend that fixation stability recorded with the MP-1 be analyzed based on the raw data. Most of the fixation parameters obtained agree with those reported in the literature, if proper calibration is used.

CHARACTERISTICS OF EYE FIXATION OF AGED PEOPLE AND GENERAL PEOPLE AT THE INTERSECTION

The characteristics of the eye fixation at the traffic intersection were examined. The experiment was performed using eye-camera, and subjects were aged people and general people. The results are as follows. 1. In the case of the aged subjects, the eye fixation time in waiting for a signal was longer than that in walking on the sidewalk and that in crossing the crosswalk. In the case of the general subjects, the eye fixation time was not influenced by such situations. 2. The eye fixation objects of the aged subjects tended to be different from that of the general subjects. 3. The eye fixation height of the aged subjects tended to be almost the same as that of the general subjects.

Compressive properties of trabecular bone in the distal femur

Early loosening and implant migration are two problems that lead to failures in cementless (press-fit) femoral knee components of total knee replacements. To begin to address these early failures, this study determined the anterior–posterior mechanical properties from four locations in the human distal femur. Thirty-three cylindrical specimens were removed perpendicular to the press-fit surface after the surgical cuts on 10 human cadaveric femurs (age 71.5±14.2 years) had been made. Compression testing was performed that utilized methods to reduce the effects of end-artifacts. The bone mineral apparent density (BMAD), apparent modulus of elasticity, yield and ultimate stress, and yield and ultimate strain were measured for 28 cylindrical specimens. The apparent modulus, yield and ultimate stress, and yield and ultimate strain each significantly differed ( p<0.05) in the superior and inferior locations. Linear and power law relationships between superior and inferior mechanical properties and BMAD were determined. The inferior apparent modulus and stresses were higher than those in the superior locations. These results show that the press-fit fixation characteristics of the femoral knee component differ on the anterior shield and posterior condyles. This information will be useful in the assignment of mechanical properties in finite element models for further investigations of femoral knee components. The property–density relations also have applications for implant design and preoperative assessment of bone strength using clinically available tools.