User experience with ultrawide curved displays: A mixed methods analysis

Due to the trend of replacing dual displays with ultrawide (UW) curved displays, we used a mixed methods analysis to investigate the user experience with UW curved displays. We conducted an experimental laboratory study that quantified user self-selected positions for three displays - 24 in. flat panel, and 34 in. and 40 in. UW curved displays. Participants were first provided with a familiarization protocol, and they then positioned the display. The self-selected UW display viewing distances were within current recommendations; however, viewing distance increased with display size, potentially challenging small work surface depths and may have been in response to feeling "overwhelmed" by larger displays. Head twist range of motion increased with display width. While all displays were within recommendations, participants commented that less head twisting was a factor in choosing the 34 in. over the 40 in. display. Practitioners should assess potential workstation limitations and the potential impact on neck twist angles when installing ultrawide displays.

Shoulder and elbow requirements during sagittal reach as a result of changing anthropometry throughout pregnancy

During pregnancy, anthropometric and physiological changes can result in difficulty reaching for and lifting everyday objects. The aims of this study were to determine the changes in sagittal plane anterior reach space (SPARS) and shoulder/elbow strength requirements throughout pregnancy. Seventeen participants were tested through a longitudinal observational cohort study between 16 and 36 weeks gestation in four-week intervals. A 25% decrease in SPARS was observed at the L3-4 torso height. Combined with arm mass increases, shoulder and elbow moment requirements at the minimum and maximum static reach distances significantly increased. However, inverse dynamics analysis determined that mass gains in the arm alone only minimally impact dynamic shoulder moments. Additionally, torso flexion increases throughout pregnancy demonstrates that women are attempting to compensate for decreased SPARS, possibly indicating the additional perceptual importance of reach space in accommodations for pregnant workers.

Neck musculoskeletal model generation through anthropometric scaling

A new methodology was developed to quickly generate whole body models with detailed neck musculoskeletal architecture that are properly scaled in terms of anthropometry and muscle strength. This method was implemented in an anthropometric model generation software that allows users to interactively generate any new male or female musculoskeletal models with adjustment of anthropometric parameters (such as height, weight, neck circumference, and neck length) without the need of subject-specific motion capture or medical images. 50^th percentile male and female models were developed based on the 2012 US Army Anthropometric Survey (ANSUR II) database and optimized with a novel bilevel optimization method to have strengths comparable to experimentally measured values in the literature. Other percentile models (ranging from the 1^st to 99^th percentile) were generated based on anthropometric scaling of the 50^th percentile models and compared. The resultant models are reasonably accurate in terms of both musculoskeletal geometry and neck strength, demonstrating the effectiveness of the developed methodology for interactive neck model generation with anthropometric scaling.

P2806A novel sirolimus drug eluting stent for Small-Vessel Disease: results from en-ABL e-registry

Objective

The aim of the study was to assess the clinical outcome of Abluminus DES in patients with small vessels.

Background

Percutaneous coronary intervention (PCI) of small coronary vessel (≤2.75 mm) associated with more chances of restenosis and repeat revascularization even when drug eluting stent employed.

Methods

A total of 2,500 patients enrolled in en-ABL e-registry which is a prospective, multicentre observational post market registry. Out of 2,500 patients, 1,253 patients had small vessel (SV, ≤2.75 mm) while 1,247 had large vessel (LV, >3mm) disease. The primary endpoint was major adverse cardiac events (MACE) which is composite of cardiac death, target vessel myocardial infraction (TV-MI) and target lesion/vessel revascularization (TLR) at 1 year follow up. The secondary endpoint were stent thrombosis and MACE up to 2 years.

Results

Baseline characteristics were well matched in both groups. In the SV group had higher prevalence of diabetes as compared to large vessel 43.0% vs 25.7%. Total 1,400 lesions treated with 1,612 Abluminus DES and 1,569 lesions treated with 1,675 Abluminus DES in SV and LV groups respectively. The mean diameter of stent was 2.61±0.23 and 3.3±0.3 mm in SV and LV groups respectively. There was a significant difference in MACE in treatment groups (3.7% vs. 1.4%, p=0.004 respectively) at 1 year. No significant differences were observed between SV and LV groups in terms of death/myocardial infarction or stent thrombosis. There were increment of only one TLR and no stent thrombosis reported at 2-year follow-up.

Conclusion

This result suggests the efficacy and safety of novel Abluminus DES in small vessel disease.

Neck posture is influenced by anticipation of stepping

BACKGROUND

Postural deviations such as forward head posture (FHP) are associated with adverse health effects. The causes of these deviations are poorly understood. We hypothesized that anticipating target-directed movement could cause the head to get "ahead of" the body, interfering with optimal head/neck posture, and that the effect may be exacerbated by task difficulty and/or poor inhibitory control.

METHOD

We assessed posture in 45 healthy young adults standing quietly and when they anticipated walking to place a tray: in a simple condition and in conditions requiring that they bend low or balance an object on the tray. We defined FHP as neck angle relative to torso; we also measured head angle relative to neck and total neck length. We assessed inhibitory control using a Go/No-Go task, Stroop task, and Mindful Attention Awareness Scale (MAAS).

RESULTS

FHP increased when participants anticipated movement, particularly for more difficult movements. Worse Stroop performance and lower MAAS scores correlated with higher FHP. False alarms on the Go/No-Go task correlated with a more extended head relative to the neck and with shortening of the neck when anticipating movement.

CONCLUSIONS

Maintaining neutral posture may require inhibition of an impulse to put the head forward of the body when anticipating target-directed movement.

Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale crater, Mars

Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.

In situ radiometric and exposure age dating of the martian surface

We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced (3)He, (21)Ne, and (36)Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.

Sex-specific prediction of neck muscle volumes

Biomechanical analyses of the head and neck system require knowledge of neck muscle forces, which are often estimated from neck muscle volumes. Here we use magnetic resonance images (MRIs) of 17 subjects (6 females, 11 males) to develop a method to predict the volumes of 16 neck muscles by first predicting the total neck muscle volume (TMV) from subject sex and anthropometry, and then predicting individual neck muscle volumes using fixed volume proportions for each neck muscle. We hypothesized that the regression equations for total muscle volume as well as individual muscle volume proportions would be sex specific. We found that females have 59% lower TMV compared to males (females: 510±43cm(3), males: 814±64cm(3); p<0.0001) and that TMV (in cm(3)) was best predicted by a regression equation that included sex (male=0, female=1) and neck circumference (NC, in cm): TMV=269+13.7NC-233Sex (adjusted R(2)=0.868; p<0.01). Individual muscle volume proportions were not sex specific for most neck muscles, although small sex differences existed for three neck muscles (obliqus capitis inferior, longus capitis, and sternocleidomastoid). When predicting individual muscle volumes in subjects not used to develop the model, coefficients of concordance ranged from 0.91 to 0.99. This method of predicting individual neck muscle volumes has the advantage of using only one sex-specific regression equation and one set of sex-specific volume proportions. These data can be used in biomechanical models to estimate muscle forces and tissue loads in the cervical spine.

The anatomy and biomechanics of acute and chronic whiplash injury

Whiplash injury is the most common motor vehicle injury, yet it is also one of the most poorly understood. Here we examine the evidence supporting an organic basis for acute and chronic whiplash injuries and review the anatomical sites within the neck that are potentially injured during these collisions. For each proposed anatomical site--facet joints, spinal ligaments, intervertebral discs, vertebral arteries, dorsal root ganglia, and neck muscles--we present the clinical evidence supporting that injury site, its relevant anatomy, the mechanism of and tolerance to injury, and the future research needed to determine whether that site is responsible for some whiplash injuries. This article serves as a snapshot of the current state of whiplash biomechanics research and provides a roadmap for future research to better understand and ultimately prevent whiplash injuries.

Mechanical properties of the human cervical spine as shown by three-dimensional load-displacement curves

STUDY DESIGN

The mechanical properties of multilevel human cervical spines were investigated by applying pure rotational moments to each specimen and measuring multidirectional intervertebral motions.

OBJECTIVES

To document intervertebral main and coupled motions of the cervical spine in the form of load-displacement curves.

SUMMARY OF BACKGROUND DATA

Although a number of in vivo and in vitro studies have attempted to delineate normal movement patterns of the cervical spine, none has explored the complexity of the whole cervical spine as a three-dimensional structure.

METHODS

Sixteen human cadaveric specimens (C0-C7) were used for this study. Pure rotational moments of flexion-extension, bilateral axial torque, and bilateral lateral bending were applied using a specially designed loading fixture. The resulting intervertebral motions were recorded using stereophotogrammetry and depicted as a series of load-displacement curves.

RESULTS

The resulting load-displacement curves were found to be nonlinear, and both rotation and translation motions were coupled with main motions. With flexion-extension moment loading, the greatest degree of flexion occurred at C1-C2 (12.3 degrees), whereas the greatest degree of extension was observed at C0-C1 (20.2 degrees). With axial moment loading, rotation at C1-C2 was the largest recorded (56.7 degrees). With lateral bending moments, the average range of motion for all vertebral levels was 7.9 degrees.

CONCLUSIONS

The findings of the present study are relevant to the clinical practice of examining motions of the cervical spine in three dimensions and to the understanding of spinal trauma and degenerative diseases.

Phacoemulsification in Indian eyes with pseudoexfoliation syndrome

PURPOSE

To evaluate the intraoperative and postoperative behavior after phacoemulsification in Indian eyes with pseudoexfoliation syndrome.

SETTING

Iladevi Cataract & Intraocular Lens Research Centre, Ahmedabad, India.

METHOD

Ninety eyes were prospectively evaluated. Group 1 (cohort) comprised 45 consecutive eyes with pseudoexfoliation and coexisting cataract and Group 2 (control), 45 consecutive normal eyes with senile cataract only. Phacoemulsification was performed by a single surgeon using a step-by-step, chop in situ, and lateral separation technique. An AcrySof intraocular lens was implanted in the bag in all eyes. Intraoperative observations included pupil size after maximal mydriasis, phakodonesis, zonular dehiscence, grade of cataract, and capsule tear/rupture. Postoperatively, intraocular pressure (IOP), best corrected visual acuity, aqueous flare/cell response, and the presence of posterior synechias were evaluated at 1 day and 1 month. A chi-square test was used for statistical analyses.

RESULTS

The mean pupil size was significantly smaller in Group 1 (P =.0000). No eye in either group had phakodonesis. Sixty percent of eyes in Group 1 and 31% in Group 2 had a hard cataract (P =.008). Endocapsular phacoemulsification was performed in 82% of eyes in Group 1 and 84% of eyes in Group 2. Intraoperative complications such as zonular or capsular dehiscence were not seen in any eye. Postoperatively, IOP and aqueous cell response were comparable between groups (P =.11 and P = 0.81, respectively). A significantly higher flare response was observed in Group 1 (P =.000). The visual outcome at 1 month was similar between groups.

CONCLUSIONS

The intraoperative performance of Indian eyes with pseudoexfoliation was comparable to that in normal eyes. A good surgical outcome is ensured by using an appropriate surgical technique. Apart from a higher flare response, the postoperative outcomes in eyes with pseudoexfoliation were within normal limits, and the outcome at 1 month was satisfactory.

Phacoemulsification in eyes with a small pupil

PURPOSE

To evaluate the intraoperative difficulties and long-term outcome of phacoemulsification through a small pupil using minimal iris manipulation.

SETTINGS

Iladevi Cataract & IOL Research Centre, Ahmedabad, India.

METHODS

This prospective study included 30 consecutive eyes with a maximally dilated pupil size of 4.0 mm or smaller. Except synechiolysis and occasional pupil retraction with a chopper, no iris manipulation was performed. The phacoemulsification technique included creation of deep central space, use of a low aspiration flow rate with appropriate vacuum, and step-by-step chop in situ and lateral separation of the nucleus. Patients were examined 1 day, 1 week, 1 and 3 months, and 1 year postoperatively. Specular microscopy was performed at 1 month and 1 year.

RESULTS

Fourteen eyes had chronic iritis, 12 had glaucoma surgery, 2 had pseudoexfoliation, and 2 had a rigid pupil. Mean follow-up was 13.6 months. Eighteen eyes (60%) had hard cataract. Mean preoperative pupil size was 2.80 mm +/- 0.75 (SD). Mean pupil size before the capsulorhexis was initiated was 4.42 +/- 0.58 mm. The iris was bruised in 10 eyes during cortex removal. Trace amounts of cortex were left in 4 cases. Two eyes had increased intraocular pressure in the early postoperative period. Six patients had a minimal amount of retained viscoelastic material (pseudofibrin), and 2 patients developed a sterile hypopyon. Sixteen eyes had cell deposits on the IOL surface and 12 eyes, fine uveal pigments. In 2 eyes with previous glaucoma surgery and in all eyes with iritis except 2, posterior synechias reformed.

CONCLUSIONS

Successful phacoemulsification was done with minimal or no pupil-widening maneuvers, restoring the preoperative pupil configuration.

Surgical techniques for difficult cataracts

This article reviews some of the advances that have taken place in the surgical techniques for difficult cataracts such as rock-hard, white, and posterior polar cataracts. Fashioning a central space, modified chopping maneuvers, and creation of multiple small fragments have enabled the surgeon to consistently achieve a successful outcome. A judicious combination of chop and separation movement in a step-by-step manner reduce the stress of the procedure and make it safer. Raised intracapsular pressure and poor visibility are dealt with through various innovative techniques. Use of high-viscosity sodium hyaluronate and double capsulorhexis allow the surgeon to achieve capsulorhexis with a high success rate. A controlled and gentle approach to phacoemulsification has proven to be the key factor for success in posterior polar cataracts.

Phacoemulsification in eyes with posterior polar cataract

PURPOSE

To evaluate the results of phacoemulsification in eyes with posterior polar developmental cataract and to appraise the strategy for surgical management.

SETTING

Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, Ahmedabad, India.

METHOD

This prospective study comprised 25 consecutive patients. All surgeries were performed by 1 surgeon. Endophacoemulsification was carried out after hydrodelineation. Hydrodissection or rotation was not attempted. A 2-port vitrectomy was performed when necessary.

RESULTS

Mean follow-up was 13.72 months (range 7 to 22 months). Nine patients (36%) developed posterior capsule rupture and 8 (32%) revealed plaques. An intraocular lens (IOL) was implanted in all 25 eyes. In 8 of 9 cases with rupture, the haptics were placed in the sulcus; in 1 case, the IOL was placed in the bag. One patient in the capsular rupture group developed macular edema 3 weeks postoperatively that responded to conservative treatment. Among 25 patients, 18 had a visual acuity of 20/20 to 20/30 and 6, 20/80 to 20/120. These 6 patients had residual posterior capsule plaque. All except 2 patients with plaque required a neodymium:YAG capsulotomy. In these patients, visual acuity improved to 20/30. In 1 patient, with microcornea, acuity did not improve to beyond 20/120.

CONCLUSION

This study confirms the predisposition to posterior capsule rupture in eyes with posterior polar cataracts. Careful surgical planning produces satisfactory technical and visual outcomes.

Graded thoracolumbar spinal injuries: development of multidirectional instability

Injuries of the thoracolumbar spine are serious, disabling, and costly to society. These injuries vary from mild ligament tears to severe bony fractures. Increased range of motion (ROM) and neutral zone (NZ) have been suggested as indicators of the resulting clinical instability. The purpose of the present study was to investigate the relative sensitivities and merits of the ROM and NZ in relation to spinal injuries of the thoracolumbar junction. A graded spinal trauma experiment was designed, in which the threshold of injury and injury progression were examined. Ten thoracolumbar human spine specimens (T11-L1) were traumatized using a high-speed incremental trauma model. The ROM and NZ, which indicate altered mechanical properties, were determined for three physiological motions: flexion/extension (FE), lateral bending (LB), and axial rotation (AR). The injury threshold was found to be 84 J (or 84 Nm) by examining both ROM and NZ for all motion types (P < 0.05), but the NZ was more sensitive. At the injury threshold, the NZ showed an overall average increase of 566% above that of the intact, while the equivalent increase in the ROM was only 94%. The NZ was also a more sensitive parameter documenting the progression of the injury beyond the injury threshold. After the maximum trauma of 137 J, the NZs for the three motions (FE, LB, and AR) increased by 700%, 1700%, and 3000% above their respective intact values. Corresponding increases in the ROM were much smaller: 115%, 184%, and 425% respectively. Direct extrapolation of the in vitro experimental findings to the clinical situation, as always, should be done with care. Our findings, however, suggest that the ROM, as measured from functional radiographs of a traumatized patient, may underestimate the true injury to the spinal column.

Relationship between lens and capsular bag size

PURPOSE

To measure the size of the lens and the empty capsular bag and evaluate the relationship between them.

SETTING

Iladevi Cataract & IOL Research Centre, Ahmedabad, India.

METHODS

In 46 eye-bank eyes, the equatorial diameter of the lens was measured after a corneoscleral button and the iris were removed. Empty capsular bag diameter was measured after extracapsular cataract extraction through an intact capsulorhexis.

RESULTS

Mean lens size was 10.20 mm +/- 0.38 (SD) and mean capsular bag size, 10.38 +/- 0.35 mm. The difference between the size of the lens and that of the empty capsular bag varied from 0 to 0.50 mm (mean 0.20 +/- 0.17 mm). Lenses measuring less than 10.25 mm in diameter showed an increase of 0.25 mm while lenses larger than 10.25 mm showed an increase of 0.09 mm.

CONCLUSION

Lens size was larger in our population than in previous studies. The increase in the empty capsular bag size was related to initial lens size.

Phacoemulsification of white mature cataracts

PURPOSE

To evaluate the intraoperative difficulties associated with phacoemulsification of white mature cataracts and develop a strategy for consistently achieving continuous curvilinear capsulorhexis (CCC) in these cases.

SETTING

Raghudeep Eye Clinic, Iladevi Cataract & IOL Research Centre, Ahmedabad, India.

METHODS

This prospective study comprised 60 eyes of 60 patients with senile white mature cataract. Mean follow-up was 7 months. Detailed preoperative and intraoperative notes were made including intraoperative subjective assessment of the intracapsular pressure and cataract hardness. A small capsulorhexis was attempted initially. Endophacoemulsification was performed using the stop, chop, chop, and stuff technique. The capsulorhexis was enlarged before intraocular lens implantation. An initial cut in the capsulorhexis margin was made with a cystotome needle while a spatula supported the anterior capsule. The capsulorhexis was then enlarged with forceps.

RESULTS

A CCC was achieved in 57 eyes (95%). Intracapsular pressure was judged to be raised in 24 eyes (40%). Of these, CCC was accomplished in 21 eyes (88%). Statistical analysis confirmed that raised intracapsular pressure was a significant factor. Capsule opacification or plaque was detected at the end of the surgery in 20 eyes (33%); 50% of the nuclei were of grade 5 hardness.

CONCLUSION

If a CCC can be achieved, the results of white cataract phacoemulsification are comparable to those of routine cataract surgery. When using the two-stage technique, one should be prepared to deal with a hard cataract through a small capsulorhexis.

Functional morphology of the spinal canal after endplate, wedge, and burst fractures

Changes in the canal diameter during physiological motions are important considerations in the treatment of patients who have a burst fracture with the presence of bony fragments, but without neurologic deficit. In this in vitro study, the changes in the soft-canal diameter of the thoracolumbar region, when intact and after different fractures, was investigated under several different loading conditions. The soft-canal diameter was clearly identified on the lateral radiographs by attaching a series of steel balls to the posterior longitudinal ligament and ligamentum flavum in the midsagittal plane. Endplate, wedge, and burst fractures were produced incrementally in 19 three-vertebrae human cadaveric spine specimens by high-speed impacts. After each injury, a series of functional lateral radiographs were taken. The minimal canal diameter (MCD) was obtained by digitizing the images of the steel balls on radiographs using a custom-designed computer program. In the intact specimens, the MCD at the disc level changed significantly in flexion, extension, and compression, when compared with the MCD in the unloaded neutral position. However, the changes were small. The MCD after endplate and wedge fractures changed in a similar way. However, after the burst fracture, the MCD at the bone fragment level increased remarkably by a distraction force. It also significantly improved by an anterior shear force in comparison to the corresponding MCD in the neutral position. However, this change was smaller than the change due to the distraction force.

Enlarging the capsulorhexis

We describe a method to enlarge an initial small capsulorhexis using an iris spatula and cystotome needle. The iris spatula is placed underneath the anterior capsulorhexis margin; the spatula supports the anterior capsule and protects the posterior capsule. A gentle touch on the spatula by the cystotome needle generates a break in the continuity. This is done prior to intraocular lens implantation with the capsular bag and anterior chamber filled with viscoelastic.

Primary posterior capsulorhexis with and without anterior vitrectomy in congenital cataracts

PURPOSE

To determine whether anterior vitrectomy is necessary along with primary posterior capsulorhexis in children less than 5 years of age with congenital cataracts.

SETTING

Iladevi Cataract & IOL Research Centre, Ahmedabad, India.

METHOD

This prospective study comprised 18 eyes of 16 children whose mean age was 2.3 years (range 3 months to 5 years). Primary posterior continuous curvilinear capsulorhexis (PCCC) and posterior chamber intraocular lens (IOL) implantation were performed in all eyes. No vitrectomy was done in 8 eyes (Group 1); an anterior vitrectomy was performed in 10 eyes (Group 2). Optic capture through the posterior capsule was achieved in 3 eyes in Group 1 and in 5 eyes in Group 2. Average follow-up was 13.3 months.

RESULTS

Five eyes (62.5%) in Group 1 needed secondary pars plana vitrectomy because the visual axis was obscured; no eye in Group 2 needed a secondary procedure. Four Group 1 eyes developed significant complications (updrawn pupil, decentration, occlusio pupillae, transient glaucoma). While no Group 2 eye developed a serious complication, some degree of pigment dispersion was noted in all the eyes.

CONCLUSION

The results suggest that anterior vitrectomy is desirable along with primary PCCC in children younger than 5 years with congenital cataracts.

Capsulorhexis: its safe limits

We undertook this study to determine the safe limits of capsulorhexis during nucleus expression in 40 eyes of patients undergoing extracapsular cataract extraction (ECCE) with a posterior chamber intraocular lens (PCIOL) implantation and in 30 cadaver eyes. In group I (patient eyes), capsulorhexis of 4.5 to 7.5 mm was performed and the nucleus was expressed by hydrodissection. The nuclei measured 4.5 to 9.0 mm. One relaxing incision at 12 o'clock position had to be placed in 9 patients. In group II (cadaver eyes), continuous curvilinear capsulotomies of 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5 mm were made in 5 eyes each. No relaxing incisions were placed. In both the groups, nuclei of all sizes could be safely delivered through intact capsulotomies measuring 5.5 mm or more. In two patient eyes, posterior capsule rupture occurred with rhexis measuring 4.5 and 5.0 mm, respectively. In the cadaver eyes, intracapsular extraction occurred in 4 eyes with rhexis measuring 5.0 mm or less. We conclude that a rhexis less than 5.5 mm is not safe for nucleus delivery during ECCE.

Dynamic canal encroachment during thoracolumbar burst fractures

In the burst fractures seen clinically, often poor correlation exists between the neurological deficit and the canal encroachment measured on post-trauma radiographic images. The purpose of the present study was to determine whether the dynamic canal encroachment during the trauma is greater than the static canal encroachment posttrauma. We successfully produced burst fractures in nine of 15 fresh human cadaveric thoracolumbar spine specimens (T11-L1). The specimens were incrementally impacted in a high-speed trauma apparatus until fracture occurred. During the trauma, dynamic canal encroachments were measured using three specially designed transducers placed in the canal at the levels of the superior end-plates of the T12 and L1 and the T12/L1 disk. After the trauma, residual static spinal canal encroachments were measured from the radiographs of the specimens that were prepared with 1.6-mm diameter steel balls lining the canal in the midsagittal plane. We found that the average canal diameter was 16.6 +/- 1.3 mm and the static canal encroachment was 18.0% of the canal diameter. The corresponding dynamic canal encroachment was 33.3%. Thus, the dynamic canal encroachment was 85% more than the static measurement. The clinical significance of this study lies in providing awareness to the clinician that the dynamic canal encroachment is significantly greater than the static canal encroachment seen on posttrauma radiographs or computed tomography scans. The finding may also explain the clinical observation of poor correlation between the canal encroachment measured radiographically and the neurological deficit.

On the understanding of clinical instability

STUDY DESIGN

Three-dimensional flexibility changes due to the application of an external fixator at C4-C5 were studied in cervical spine specimens.

OBJECTIVES

To evaluate the biomechanical effects of applying a cervical external fixator to a patient using an in vitro model.

SUMMARY OF BACKGROUND DATA

There is controversy regarding the relationship between the changes in spinal motion and clinical instability.

METHODS

Using fresh cadaveric C4-C7 specimens, multidirectional flexibility was measured at all vertebral levels, before and after the fixator application at C4-C5, C5-C6, and C4-C6.

RESULTS

The average ranges of motion for flexion, extension, lateral bending, and axial rotation were 8.3 degrees, 7.2 degrees, 5.3 degrees, and 5.6 degrees, which decreased by 40%, 27%, 32%, and 58%, respectively, because of the fixator application. The corresponding neutral zones were 3.4 degrees, 3.4 degrees, 3.0 degrees, and 2.0 degrees, which decreased by 76%, 76%, 54% and 69%, respectively. The decreases with the fixation at C4-C5 were similar to those for fixation at C5-C6.

CONCLUSIONS

This in vitro study documented that the application of an external fixator to the cervical spine decreases the intervertebral motion in general, and decreases flexion, extension and torsional neutral zones in particular. The findings help explain the clinical instability of the spine and support the hypothesis that the neutral zone is more closely associated with the clinical instability than is the range of motion.

Intraocular lens implantation in infants with congenital cataracts

We evaluated 21 eyes of 13 infants between two and eight months old who had primary posterior chamber intraocular lens (IOL) implantation for congenital cataracts between 1988 and 1993. Twelve eyes had a posterior capsulorhexis or plaque peeling at the time of implantation and one eye had a vitrectomy. Eight eyes had no posterior capsule procedure during the initial surgery. Follow-up ranged from six months to five years. All eyes developed one or multiple posterior synechias and all, except one, required secondary capsulectomy and vitrectomy between one month and one year. Twenty eyes attained stable IOL fixation and a clear visual axis. In one eye, the IOL decentered downward. Patients with bilateral cataracts had greater visual improvement than those with a cataract in one eye only. No patient could manage spectacles postoperatively. Our findings show the benefits of posterior capsulectomy and anterior vitrectomy done in the early postoperative period and that IOL implantation in infants is a reasonable treatment in some parts of the world.

[The unstable spine--an "in vitro" and "in vivo study" on better understanding of clinical instability]

In cases of suspected painful instability of a cervical segment, temporary external fixation by means of external fixator was applied. The segmental immobilization caused immediate relief of pain. The pain reoccurred after removal of the immobilization. The effect of immobilization by external fixation was investigated in biomechanical tests using fresh cadaveric C4-7 specimens. Multidirectional flexibility was measured before and after application of the fixator at C4/C5, C5/C6 and C4-6. We measured the reduction in motion between the different segments. In every situation the neutral zone decreased more than the range of motion. The findings are helpful to understand the clinical instability of the spine and support the hypothesis that the neutral zone is more closely associated with clinical instability than range of motion. The combination of clinical application and biomechanical investigation allowed us to establish a direct correlation between instability and pain.

Disc degeneration affects the multidirectional flexibility of the lumbar spine

STUDY DESIGN

An in vitro biomechanical investigation using human lumbar cadaveric spine specimens was undertaken to determine any relationship between intervertebral disc degeneration and nonlinear multidirectional spinal flexibility.

SUMMARY OF BACKGROUND DATA

Previous clinical and biomechanical studies have not established conclusively such a relationship.

METHODS

Forty-seven discs from 12 whole lumbar spine specimens were studied under the application of flexion-extension, axial rotation, and lateral bending pure moments. Three flexibility parameters were defined (neutral zone (NZ), range of motion (ROM), and neutral zone ratio (NZR = NZ/ROM)) and correlated with the macroscopic and radiographic degeneration.

RESULTS AND CONCLUSIONS

In flexion-extension, the ROM decreased and NZR increased with degeneration. In axial rotation, NZ and NZR increased with degeneration. In lateral bending, the ROM significantly decreased and the NZR increased with degeneration. In all three loading directions, the NZR increased, indicating greater joint laxity with degeneration.

Anular incision technique on the strength and multidirectional flexibility of the healing intervertebral disc

STUDY DESIGN

This study used a sheep model to biomechanically analyze the healing strength of the anulus fibrosus after two types of anular incisions.

OBJECTIVE

This study evaluated whether the type of anular incision made at the time of lumbar discectomy plays a role in the subsequent healing strength of the anulus and the biomechanical flexibility of the corresponding motion segment.

METHODS

Two types of anular incision, a full thickness removal of a box or window of anulus and a full thickness straight transverse slit through the anulus, were made in the intervertebral discs of 18 adult sheep. After healing times of 2, 4, and 6 weeks, the intervertebral discs were tested versus control levels for strength of anular healing and biomechanical flexibility of the corresponding motion segment.

RESULTS

The box incised discs showed a significantly greater loss in strength during the early healing phase (2 to 4 weeks) and a longer response before recovering anular strength when compared with the slit-incised discs. The type of incision also affected the multidirectional flexibility of the motion segments in a differentiated manner. Larger amounts of motion were seen with the box incision when compared with the slit incision at all time periods and in all pure moments.

CONCLUSION

The technique of anular incision plays a definite role in the timing and strength of subsequent anular healing. The box incision through the anulus led to significantly weaker healing than did the slit incision in the early healing phase (2-4 weeks). Also, larger amounts of motion were seen in the vertebral motion segments of those discs undergoing box incision when compared with slit or control levels.

Kinematics of the cervical spine canal: changes with sagittal plane loads

Spondylotic myelopathy is a result of decreased spinal canal space due to degeneration. The space also may change with physiological movements. The knowledge of the normal physiological changes is necessary for a better understanding of the clinical symptoms. Using a novel technique, we measured the changes in disk bulge, ligamentum flavum bulge, and anteroposterior canal diameter in response to tension-compression forces (up to 40 N each) and combined loading: 2 Nm of flexion or extension moment combined with 20 N compression force in five human cadaveric lower cervical spine specimens (C4-C7). From tension to compression, the average disk bulge changed 1.13 mm or 10.1% of the original canal diameter. The ligamentum flavum bulge changed 0.73 mm or 6.5% of the canal diameter. From flexion to extension the average disk bulb changed 1.16 mm or 10.8% of the canal diameter, whereas the ligamentum flavum bulge changed 2.68 mm or 24.3% of the canal diameter. Most of the changes in the bulges occurred with a small load application around the neutral position of the spine. The results of this study demonstrate that ligamentum flavum bulge can contribute significantly to canal encroachment in extension and that a flexed posture increases the sagittal diameter of the spinal canal.

Fermentation of a Yeast Producing A. Niger Glucose Oxidase: Scale-Up, Purification and Characterization of the Recombinant Enzyme

We have developed a fermentation process to produce up to 3 grams per liter of active, secreted glucose oxidase from a recombinant Saccharomyces cerevisiae. Real-time size-exclusion HPLC analysis is used to monitor enzyme production during fermentation, and purification to more than 95 percent is obtained using only filtration methods. The recombinant enzyme is stable to higher temperatures and a wider pH range than the native Aspergillus niger enzyme, and is free of contaminating amylase, cellulase and catalase.

Glucose oxidase from Aspergillus niger. Cloning, gene sequence, secretion from Saccharomyces cerevisiae and kinetic analysis of a yeast-derived enzyme

The gene for Aspergillus niger glucose oxidase (EC 1.1.3.4) has been cloned from both cDNA and genomic libraries using oligonucleotide probes derived from the amino acid sequences of peptide fragments of the enzyme. The mature enzyme consists of 583 amino acids and is preceded by a 22-amino acid presequence. No intervening sequences are found within the coding region. The enzyme contains 3 cysteine residues and 8 potential sites for N-linked glycosylation. The protein shows 26% identity with alcohol oxidase of Hansenuela polymorpha, and the N terminus has a sequence homologous with the AMP-binding region of other flavoenzymes such as p-hydroxybenzoate hydroxylase and glutathione reductase. Recombinant yeast expression plasmids have been constructed containing a hybrid yeast alcohol dehydrogenase II-glyceraldehyde-3-phosphate dehydrogenase promoter, either the yeast alpha-factor pheromone leader or the glucose oxidase presequence, and the mature glucose oxidase coding sequence. When transformed into yeast, these plasmids direct the synthesis and secretion of between 75 and 400 micrograms/ml of active glucose oxidase. Analysis of the yeast-derived enzymes shows that they are of comparable specific activity and have more extensive N-linked glycosylation than the A. niger protein.