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PubMedDate not supplied

[The sensitivity of ultradistal mineral measurement of the radius in the early assessment of bone loss].

This study was carried out to assess the sensitivity of single photon bone absorptiometry (SPBA) as an early screening tool for osteoporosis and select the optimum site for measurement. We measured bone mineral density (BMD) at the distal tenth of both radius and ulna (D-BMD) and at the ultradistal radius, a site distal to the point at which the radius and ulna are 8 mm apart (UD-BMD). Our study group consisted of 107 healthy women aged 25-60 years (mean +/- SD: 45.8 +/- 10.0), subdivided according to age into 3 groups: Group 1: 25-40 years, Group 2: 41-50 years, Group 3: 51-60 years. When comparison was made to Group 1, D-BMD was found significantly reduced only in Group 3 (p < 0.0001), while UD-BMD was found reduced in both Groups 2 (p < 0.02) and 3 (p < 0.0001). The percent reduction of BMD in Groups 2 and 3 with respect to Group 1 was significantly greater at the ultradistal site than at the distal tenth of the radius and ulna (p < 0.0001 versus D-BMD). Despite limits inherent in the cross-sectional study design, our results suggest that forearm SPBA indicates post-menopausal bone loss irrespective of scanning site, but detects pre-menopausal loss sensitively only at the ultradistal site. Ultradistal measurement would therefore seem suitable for early screening for osteoporosis as an alternative or in addition to the generally used more proximal site.

Absorptiometry, Photon↗
PubMed1993

Use of the external fixation apparatus for percutaneous insertion of pins in the distal one-third of the radius: an anatomic study.

OBJECTIVE: To assess the risk of soft-tissue injury during percutaneous placement of external fixation pins in the proximal radius. DESIGN: An anatomic study with embalmed cadaver limbs. SETTING: Hand and upper limb centre at a university-affiliated hospital. INTERVENTIONS: Two 4-mm Hoffman half pins were percutaneously placed along the dorsoradial ridge of the radius, four finger breadths proximal to the radial styloid process. MAIN OUTCOME MEASURES: Injuries to soft tissues including tendons, nerves and vessels were noted. RESULTS: Nerve or tendon injuries occurred in 7 of 26 forearms. Three pins transfixed either the superficial branch of the radial nerve or lateral antebrachial cutaneous nerves. Tendon injuries included the brachioradialis in two forearms, the extensor carpi radialis brevis in three forearms, and the extensor carpi radialis longus and the abductor pollicis longus in one forearm each. CONCLUSIONS: Percutaneous pin placement in the distal radius is unsafe. The authors recommend open pin placement for fractures of the distal radius.

Bone Nails↗
PubMed1995

Iatrogenic posterior interosseous nerve injury: is transosseous static locked nailing of the radius feasible?

To assess the risk of injury to the posterior interosseous nerve (PIN) in transosseous locked nailing of the radius, the relationship of the PIN to the surgical zone was studied in five pairs of fresh frozen adult cadaver arms. A static locked intramedullary nail was inserted in each radius using the recommended surgical technique. A formal dissection of the radial nerve and its branches was then performed to document the relationship of the PIN to the radial head in neutral, pronation, and supination also was measured. In no specimens was the PIN injured by the screw insertion. However, in two specimens (right and left arm of the same donor) the PIN was 1 mm and 2 mm, respectively, from the screw insertion site. The average shortest distance from the PIN to the screw was 11.3 mm. As measured along the mid-shaft of the radius, the average distance from the radial head to the PIN was 36.2 mm in 90 degrees supination, 46.7 mm in neutral, and 56.9 mm in 90 degrees pronation. Transosseous static locked nailing of the radius is feasible, but the surgeon and patient must be aware of the risk of possible injury to the PIN. To minimize this risk, we suggest that the proximal locking screw should be inserted from a direct lateral entry at < 30 mm from the radial head with the forearm in neutral rotation.

Adult↗
PubMed1994

Orthofix external fixation of distal radius fractures: complications associated with screw size.

We did a retrospective analysis of 28 patients who were treated with the Orthofix external fixation system for complex fractures of the distal radius to study complications associated with screw size. The 14 patients in group 1 had a 4.5/3.5-mm tapered screw placed in the metacarpal bone; the 14 patients in group 2 had a 3.5/3.3-mm tapered screw placed in the metacarpal bone. Both groups had 4.5/3.5-mm tapered screws placed in the radius. Two patients in group 1 had metacarpal pin tract infections; no patients in group 2 had a distal pin tract infection. Two patients in group 1 had a fracture of the metacarpal; only one patient in group 2 had a fracture of the metacarpal. In both groups two patients had proximal pin tract infections at the radius screw fixation site. There was no screw breakage in either group. The unique design of the tapered Orthofix screw allows it to be removed almost painlessly in the clinic. At installation in the operating room, however, the surgeon must remember not to back the threaded pin out for fine adjustment of bony penetration. Any reverse excursion of the threaded shaft will loosen the tapered screw and cause early failure of the fixation. We no longer use the 4.5/3.5-mm screw when managing wrist fractures with the Orthofix external fixation system. It is now our policy to use the 3.5/3.3-mm screw for fixation of the Orthofix external frame to both the metacarpal bone and the radius.

Adolescent↗
PubMed1996

[Fractures of the distal radius with dorsal displacement: a comparative study of the predictive value of 6 classifications].

PURPOSE OF THE STUDY: The authors compare six classifications in a prospective study of distal radius fractures surgical treatment. Classifications included Castaing's, Frykman's, Gartland's, Older's, Lindström's and Jenkins'. MATERIAL: 96 patients presenting a distal radius fracture were included in a protocol comparing two surgical treatments. 42 were treated with styloid pinning and immobilization while 54 with intra-focal pinning and immediate mobilization according to Kapandji's technique. METHODS: Each patient was graded initially according to each six classifications. Patients were reviewed at 6 weeks, 3, 6, 12, and 24 months. Clinical and radiographical evaluation were performed. Clinical and radiological results were compared according to each group of classification. RESULTS: None of the six classifications appeared to have any utility to predict functional or radiological results. None was able to distinguish treatment option. DISCUSSION: The six classifications did not permit to predict clinical or radiological outcome of distal radius fractures treated by radial styloid pinning or Kapandji's technique. All those classifications have been described for conservative treatment rarely performed in France for displaced fractures. CONCLUSION: The six classifications tested showed no predictive value in K-wire treatment of dorsally displaced distal radius fractures.

Adolescent↗
PubMed1996

[Carpal ligament lesions associated with fresh distal radius fractures: arthroscopic study of 54 cases].

AIM: Intracarpal ligamentous tears and fractures of the distal radius may have a similar injury mechanism. We performed arthroscopy of the wrist in 54 patients with distal radius fracture to find out the frequency of associated ligamentous tears. RESULTS: 41% of the patients with an extraarticular fracture of the distal radius had at least one severe ligamentous tear of a carpal ligament. In the group of patients with intraarticular fracture we detected ligamentous tears even in 89%. Most frequent were tears of the lunotriquetral ligament. DISCUSSION: Associated ligamentous tears are more common than expected. These tears may be of importance in the outcome of treatment of distal radius fractures.

Adolescent↗
PubMed2005

Effect of background electrolyte on the estimation of protein hydrodynamic radius and net charge through capillary zone electrophoresis.

Two physicochemical models are proposed for the estimation of both hydrodynamic radius and net charge of a protein when the capillary zone electrophoretic mobility at a given protocol, the set of pK of charged amino acids, and basic data from Protein Data Bank are available. These models also provide a rationale to interpret appropriately the effects of solvent properties on protein hydrodynamic radius and net charge. To illustrate the numerical predictions of these models, experimental data of electrophoretic mobility available in the literature for well-defined protocols are used. Five proteins are considered: lysozyme, staphylococcal nuclease, human carbonic anhydrase, bovine carbonic anhydrase, and human serum albumin. Numerical predictions of protein net charges through these models compare well with the results reported in the literature, including those found asymptotically through protein charge ladder techniques. Model calculations indicate that the hydrodynamic radius is sensitive to changes of the protein net charge and hence it cannot be assumed constant in general. Also, several limitations associated with models for estimating protein net charge and hydrodynamic radius from protein structure, amino acid sequence, and experimental electrophoretic mobility are provided and discussed. These conclusions also show clear requirements for further research.

Electrolytes↗
PubMed2001

Adhesive Contact of Elastically Deformable Spheres: A Computational Study of Pull-Off Force and Contact Radius.

Elastic spheres in contact deform around the contact region, due to intermolecular interaction forces. The deformed contacting surfaces change the distance between interacting molecules that in turn alters the force of interaction. Thus, the contact behavior of elastic spheres constitutes a nonlinear mathematical problem that defies the traditional analytical methods for general solution. Efficient computational techniques have enabled a detailed study of adhesive contact behavior of elastically deformable spheres with self-consistent solutions of a nonlinear integral governing equation. The present work extends the previous computational analysis to the quantities of practical interests such as the pull-off force and the radius of contact area. Trends of variations in the pull-off force as physical properties change are examined. Computationally determined radial positions as stress condition indicators suggest that the concept of contact radius is not clearly defined in the literature and can be confusing. It seems that some contact mechanics models would be consistent with the definition of the edge of contact area as the radial position for the local surface stress to change from compression to tension, whereas others would rather assume the contact radius as the radial position for the local tensile stress to reach its peak. The substantial quantitative deviation of self-consistently computed contact radius from the DMT model prediction suggests that models based on the assumption of a well-defined contact area having a constant gap may not be appropriate when describing cases of small values of Tabor's parameter. Copyright 2001 Academic Press.

Journal Article↗
PubMed1998

Minimal radius of curvature of lipid bilayers in the gel phase state corresponds to the dimension of biomembrane structures "caveolae".

Caveolae are membrane invaginations with a radius of curvature in the range of 40 nm for the bulb; 10-15 nm is the minimal radius for lipid bilayers in the liquid-crystalline Lalpha (liquid-disordered: ld) phase state. A minimal radius of 20-30 nm could be detected for the gel phase state by analysis of convex-concave bilayer deformations. Circular protrusions with a diameter in the range of only about 40 nm are closed by a flat lid, and those with diameters of 60 nm or more are closed by hemispherical caps. These structures are found primarily in phosphatidylcholine/sterol mixtures, where the gel phase state "liquid ordered" (lo) has been introduced. As a further example the mixture of dimyristoylphosphatidylcholine (DMPC) with an unusual sterol (diflucortolon-21-valerat) is presented. In the usual hydration at temperatures above the phase transition the deformation requires an incubation at 4 degrees C for several weeks or months to form. Using a low temperature hydration procedure (at 4 degrees C), surprisingly bilayers of pure DMPC and DPPC (dipalmitoylphosphatidylcholine) are found to deform in the same convex-concave manner, and this takes place within hours and days. The dependence on hydration protocol is also observed for formation of a sponge-like bilayer network with 30-35 nm radius of curvature in brain sphingomyelin and its mixtures with cholesterol. Caveolae are microdomains enriched in cholesterol and sphingomyelin and are simultaneously discussed to be in the lo state. Direct evidence by investigation of bilayers formed by the lipids isolated from caveolae is still lacking, but structures similar to caveolae which are in the gel phase state (very probably the lo state) are also formed by lipids extracted from bacterial membranes. A further analogy exists because both natural lipid mixtures (brain sphingomyelin and bacterial lipids) transform during heating from the curved bilayer structures into microvesicles above the phase transition. Internalization of caveolae is a process of vesicle formation.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2001

[Postoperative morbidity in surgically treated extension fractures of the distal radius. A comparative study of dorsal and volar approach].

The aim of this study was to investigate perioperative morbidity in operative interventions in distal radiusfractures, comparing the operative approach from volar and dorsal. Only problems, resulting from the operative approach towards the distal aspect of the radius, were examined. In a Case-Control-Study, we investigated patients with operative by plate-osteosynthesis treated distal radius-extensions-fractures. During 3 years we investigated 92 patients. 49 were operated with a volar approach, and after changing the operative management, consecutive 43 patients with a dorsal approach to the distal radius. Indications for operative treatment were not changed. The approach to the distal aspect of the radius corresponded to the recent guidelines. Further perioperative procedures were identical, including procedures in anesthesiology. Datas of patients have been investigated for epidemiology, kind of operations, point of time in treatment, duration of operation, X-Ray, immobilisation and time of inhospital stay as well as all documented complications. It has been shown, that in respect of all criterias, concerning length of operation (106 vs. 83 min), intraoperative X-Ray (3.0 vs. 1.65 min) as well as postoperative immobilisation (33 vs. 25 days), and documented incidences of complications like secondary wound-healing (19/49 vs. 0/43) or nerval irritations (13/49 vs. 1/43), the dorsal osteosynthesis is definitively to be favored.

Adolescent↗
PubMed2000

Radius construction and structure in the orb-web of Zilla diodia (Araneidae).

In orb-webs, the tension of the sticky spiral produces a centripetal force on the radii, resulting in an increase in tension along each radius from the centre of the web to the periphery. Zilla diodia (Walckenaer, 1802) atypical of araneids, was found to adapt the structure of its radii to this tension gradient by building radii that are double stranded at the periphery of the web and single stranded near the centre. Furthermore, the proportion of each radius that is doubled was found to be larger in the upper part of the web - where the overall tensions in the radii are known to be higher than in the lower part of the web. suggesting that the spider adjusts the proportion of each radius that is doubled to the overall tension in the radius.

Animals↗
PubMed1993

Fractures of the distal end of the radius in young adults: a 30-year follow-up.

76 patients were examined clinically and radiologically 27 to 36 years after a fracture of the distal radius. The average age was 31 years at the time of injury and 63 years at follow-up. In 81% of the patients there was no difference between the fractured and the non-fractured side. No patient had to change his or her occupation or leisure activities because of the fracture. There were more degenerative changes in the fractured wrist than in the non-injured side. A statistically significant correlation was found between axial compression and the presence of degenerative changes in the radio-carpal and distal radio-ulnar joints. Treatment of the fracture of the distal end of the radius in the young adult should aim to conserve the length of the radius. However, after 30 years, complaints are few and correlate with degenerative changes in the radio-carpal joint only. 47 patients with articular fractures of the distal end of the radius were examined in the same way. The average age at the time of injury was 32 years and 58% of the patients were men. In 87% of the patients there was no difference between the fractured and the non-fractured side. However 37% had minor complaints. A higher proportion of patients with articular fractures developed degenerative changes than those with non-articular fractures. The existence of radiographic signs of osteoarthritis is directly related to axial compression and the persistent incongruity, after reposition, in either the radio-carpal or the distal radio-ulnar joints.

Adult↗
PubMed2006

Low-profile dorsal plating for dorsally angulated distal radius fractures: an outcomes study.

PURPOSE: Controversy exists surrounding the effectiveness and complications associated with dorsal plating for distal radius fractures. This study evaluated the functional outcome of dorsal plating for dorsally angulated distal radius fractures at a single institution. METHODS: Thirty patients formed the study cohort. All plates were low profile and stainless steel. Radiographic parameters, range of motion, and strength compared with the uninjured side were recorded. The functional outcome was evaluated by the Disabilities of the Arm, Shoulder, and Hand questionnaire and the Gartland and Werley scoring system. RESULTS: The median patient age at surgery was 59 years. The median follow-up period was 18 months. According to the AO classification system, there were 4 type A fractures, 5 type B fractures, and 21 type C fractures. The median preoperative dorsal angulation was 30 degrees, and the median postoperative angulation was -4 degrees volar. Sixteen patients with fractures had an intra-articular step-off or gap, which were all corrected to neutral by the procedure. Seven patients with the fractures showed positive ulnar variance, all corrected to neutral at time of follow-up evaluation. Compared with the contralateral side, the mean extension and flexion were 88% and 81%, respectively; pronation and supination were 89% and 87%, respectively; and grip strength and thumb pinch were 78% and 94%, respectively. The mean postoperative Disabilities of the Arm, Shoulder, and Hand questionnaire score was 15 points, and 28 patients had Gartland and Werley scores of good or excellent. No patients needed to have their plates removed, and no extensor tendon rupture was reported. One patient lost reduction, 1 patient needed a tenolysis of the extensor pollicis longus tendon, and 2 patients required the removal of a single metaphyseal screw. CONCLUSIONS: Results from this study show that patients can expect to have 80% of their range of motion and strength after dorsal plating for distal radius fractures. Moreover, 93% of the patients will have good to excellent functional outcomes. Complications from dorsal plating may be caused by the specific plate used, rather than by the technique itself, supporting a dorsal approach for dorsally angulated distal radius fractures.

Adult↗
PubMed1995

The radius of gyration of native and reductively methylated myosin subfragment-1 from neutron scattering.

Reductive methylation of nearly all lysine groups of myosin subfragment-1 (S1) was required for crystallization and solution of its structure at atomic resolution. Possible effects of such methylation on the radius of gyration of chicken skeletal muscle myosin S1 have been investigated by using small-angle neutron scattering. In addition, we have investigated the effect of MgADP.Vi, which is thought to produce an analog of the S1.ADP.Pi state, on the S1 radius of gyration. We find that although methylation of S1, with or without SO42- ion addition, does not significantly alter the structure, addition of ADP plus vanadate does decrease the radius of gyration significantly. The S1 crystal structure predicts a radius of gyration close to that measured here by neutron scattering. These results suggest that the overall shape by crystallography resembles nucleotide-free S1 in solution. In order to estimate the effect of residues missing from the crystal structure, the structure of missing loops was estimated by secondary-structure prediction methods. Calculations using the complete crystal structure show that a simple closure of the nucleotide cleft by a rigid-body torsional rotation of residues (172-180 to 670) around an axis running along the base of the cleft alone does not produce changes as large as seen here and in x-ray scattering results. On the other hand, a rigid body rotation of either the light-chain binding domain (767 to 843 plus light chains) or of a portion of 20-kDa peptide plus this domain (706 to 843 plus light chains) is more readily capable of producing such changes.

Amino Acids↗
PubMed1999

An asymptotic estimate for the effective radius of a concentric bipolar electrode.

A concentric bipolar electrode (CBE) (consisting of a central disc and an outer annulus) has been proposed as an approximate method of measuring the surface Laplacian of the body surface electrical potential distribution. The derivation of the surface Laplacian approximation, in terms of the potential difference measured with the bipolar electrode, contained an unspecified parameter which has been dubbed the 'effective radius' of the concentric bipolar electrode. This paper presents an asymptotic analysis to derive an expression for the effective radius in terms of the physical dimensions of the electrode (the radius of the central disc and inner and outer radii of the annulus). Also studied is the way in which the value of the effective radius affects the behaviour of the relative error in the surface Laplacian measurement at various dipole source locations within a conducting medium.

Body Surface Potential Mapping↗
PubMed2004

Voltammetric determination of the geometrical parameters of inlaid microdisks with shields of thickness comparable to the electrode radius.

The cyclic voltammetric behavior of disk microelectrodes surrounded by thin insulating shields (TSM) was investigated from both theoretical and experimental points of view. In particular, microdisks with shields of thickness (b - a), a few electrode radii (a) were considered. A finite difference simulation procedure with a nonuniform, expanding spatial grid, already available in the literature, was employed for predicting shape and height of the voltammograms. The parameters of this numerical simulation were optimized again, and the steady-state limiting currents found in this work for a range of TSMs compared well with previous publications. The steady-state limiting current at TSMs was enhanced with respect to microelectrodes surrounded by thick insulating sheaths (i.e., b >> a), and steady-state conditions were achieved faster. Under these conditions, the difference in potential observed on the forward and backward waves, when the current is half of its maximum value (deltaE(1/2)), was almost equal to zero. Nonsteady-state cyclic voltammograms were also simulated using the optimized parameters, and the effect of scan rate on deltaE(1/2) was examined in detail. Based on this dependence, a voltammetric procedure for the simultaneous determination of microdisk radius and its insulator thickness was proposed. Experimental measurements were performed by using platinum wires, 10-12.5-microm radius, and carbon fibers, 4-microm radius, coated with 4-6-microm-thick electrophoretic paint. The shield thickness produced around the wires was such that b/a < 3. The experimental results obtained were in general congruent with the theory and demonstrated the validity of the method proposed here for the simultaneous determination of radius and shield thickness of a TSM.

Journal Article↗
PubMed2002

Radius and asphericity of the posterior corneal surface determined by corrected Scheimpflug photography.

PURPOSE: To obtain the shape of the posterior corneal surface in a healthy population, using Scheimpflug photography corrected for distortion due to the geometry of the Scheimpflug imaging system and the refraction of the anterior corneal surface. METHODS: The posterior corneas of 83 subjects, ranging in age from 16 to 62 years, were measured in the vertical meridian using corrected Scheimpflug photography. The aspherical shape of the anterior Corneal surface was also determined in conjunction with the correction of Scheimpflug images. RESULTS: The average radius of the anterior corneal surface was 7.87 +/- 0.27 mm (SD), while the average radius of the posterior corneal surface was 6.40 +/- 0.28 mm (SD). The ratio between the posterior and the anterior radius of curvature was 0.81 +/- 0.02. The asphericity of the anterior and the posterior corneal surfaces was 0.82 +/- 0.18 and 0.62 +/- 0.27, respectively. The asphericity of the posterior corneal surface decreased significantly with age. The posterior/anterior asphericity ratio is also dependent on age and was 0.98 +/- 0.17 at 16 years of age and 0.53 +/- 0.30 at 62 years of age. CONCLUSION: Corrected Scheimpflug photography is an appropriate technique for measuring the radius and asphericity of the posterior corneal surface. The asphericity of the posterior corneal surface changes with age.

Adolescent↗
PubMed1989

Wall-thickness and midwall-radius variations in ventricular mechanics.

A fluid-fiber-collagen stress tensor is used to describe the rheology of the left ventricle of the heart. Linear theory is used to find the equilibrium solutions for the end-diastolic and end-systolic states of general axisymmetric shapes that are small perturbations of a thick-walled finite cylinder. The general problem can be studied by superposing the effects of variable midwall radius but constant wall thickness with those of variable wall thickness but constant midwall radius. A Fourier series representation is used to describe the midwall radius and thickness functions. Numerical calculations are performed to determine the deformed geometry and spatial distributions of tissue pressure, stresses, and fiber strains. The calculations proved to be highly accurate when compared to an analytical solution obtained for the special case of no fibers. The results show significant longitudinal differences when compared to results for the cylindrical geometry, with more sensitivity to variation in wall thickness than to variation in midwall radius.

Animals↗