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At least 343 records · Page 19Linked to original sources
PubMed2004

An evaluation of effective radiuses of bulk-wave ultrasonic transducers as circular piston sources for accurate velocity measurements.

The effective radius of a bulk-wave ultrasonic transducer as a circular piston source, fabricated on one end of a synthetic silica (SiO2) glass buffer rod, was evaluated for accurate velocity measurements of dispersive specimens over a wide frequency range. The effective radius was determined by comparing measured and calculated phase variations due to diffraction in an ultrasonic transmission line of the SiO2 buffer rod/water-couplant/SiO2 standard specimen, using radio-frequency (RF) tone burst ultrasonic waves. Fourteen devices with different device parameters were evaluated. The velocities of the nondispersive standard specimen (C-7940) were found to be 5934.10 +/- 0.35 m/s at 70 to 290 MHz, after diffraction correction using the nominal radius (0.75 mm) for an ultrasonic device with an operating center frequency of about 400 MHz. Corrected velocities were more accurately found to be 5934.15 +/- 0.03 m/s by using the effective radius (0.780 mm) for the diffraction correction. Bulk-wave ultrasonic devices calibrated by this experimental procedure enable conducting extremely accurate velocity dispersion measurements.

Journal Article↗
PubMed1992

The distal joint of the radius and ulna. Diagnostic studies and treatment rationale.

Three areas of functional anatomy are present in the distal ulna. Each of these has a specific function in load bearing of the wrist, rotation of the forearm, and maintenance of the relationship between the radius and ulna. The distal portion of the ulna serves as a suspensory post for ligaments that stabilize the ulnar border of the wrist. The midportion of the distal ulna contains the load-bearing triangular fibrocartilage complex. The proximal portion of the distal ulna articulates with the radius at the sigmoid notch and participates in forearm rotation. Each of these areas is assessed in problems related to ligament instability, load bearing, and range of motion. Mechanical problems that affect the distal joint of the radius and ulna include the affects of trauma, degenerative change, and inflammatory disease. Each of these requires evaluation in the treatment of joint derangement. Diagnostic studies that relate to problems in the distal radioulnar joint area include standard roentgenographs, arthrograms, magnetic resonance (MR) scanning, and arthroscopy. Each of these studies has particular advantages and disadvantages in providing data for analysis of joint malfunction. A medical history, physical examination, and use of proper diagnostic studies will assist in an appropriate diagnosis of problems in the distal joint of the radius and ulna.

Adult↗
PubMed1994

[A method of measuring iris radius by computerized image analysis].

A new method of measuring the iris contour has been set up with a personal computer. The model of a parabolic curve, an approximate mimic iris contour curve, was traced to define the profile contour of the iris from a photograph. A radius measured from the apex of the curvature of the parabola, named iris radius (IR), was calculated by a computer to describe the degree of the curvature of the iris contour. The iris radius of 93 eyes of 68 cases with early pupillary block primary angle closure glaucoma were measured by this method. The results show that the mean iris radius of cases with glaucoma is shorter than that of the normal age matched controls (53 cases 106 eyes) and there is statistical significant difference (P < 0.01). This method of measurement can be an effective method to further study the early diagnosis and pathogenic mechanism of the pupillary block angle closure glaucoma.

Adult↗
PubMed1998

Management of comminuted fractures of the distal radius in the adult. Conservative or surgical?

Displaced fractures of the distal radius are difficult to treat successfully by traditional nonoperative methods. The goal in the management of these fractures is to achieve extraarticular alignment and an articular step off of less than 2 mm. Cast immobilization has been supplemented with pins and plaster technique and external fixators. Percutaneous are limited open reduction techniques, combined with wrist arthroscopy, have been shown to be useful in the management of intraarticular distal radius fractures. Despite these advances, there are still a significant number of fractures in which the articular surface cannot be reconstructed without open reduction and internal fixation. The main objective is to restore articular integrity as perfectly as possible. Attention to meticulous surgical technique will facilitate good results. When articular restoration cannot be accomplished, early arthrodesis or arthroplasty should be indicated. In the absence of osteoarthritis, intraarticular osteotomy can be used for intraarticular malunions with a step off greater than 2 mm. Radius malalignment usually requires a dorsal opening wedge osteotomy, insertion of a corticocancellous graft, and a dorsal buttress plate. Early recognition and treatment of distal radioulnar joint injuries associated with fractures of the distal radius are paramount to reduce the incidence of painful sequelae and functional deficits.

Adult↗
PubMed1998

Assessment of the apical transportation of root canals using the method of the curvature radius.

The purpose of this investigation was to evaluate the occurrence of apical transportation after root canal instrumentation using only K-Flexofiles or K-Flexofiles intercalated with K-Flexofile Golden Mediums. For this purpose, the degree (Schneider's method) and the radius of the curvature was recorded before and after instrumentation. The results showed that there was no statistically significant difference between the techniques. The correlation between the degree and the radius of curvature of the root canal was not consistent, nor was there a relationship between the original radius of curvature and the apical transportation. However, determination of curvature by use of its radius has proved to be an effective method.

Dental Instruments↗
PubMed1979

Loss and recovery of trabecular bone in the distal radius following fracture--immobilization of the upper limb in children.

Computed tomography of the human radius is performed using a special purpose scanning device which incorporates a radionuclide (125I) as radiation source. Parameters decribing the trabecular bone and the compact bone are determined at a distal and a diaphyseal measuring site respectively. Using this measurement technique changes in bone mineralization in the radius were studied in a group of 23 children following immobilization of an upper limb for fracture healing. An immobilization period of between three to six weeks resulted in a reduction of the relevant parameter value of up to 44% (mean 16%) in the distal part of the radius, whereas no significant change could be seen in the diaphyseal part of the same bone. Rapid remineralization of trabecular bone is indicated by the increase of the corresponding parameter value at a rate of up to several percent per week. However, in some of the patients studied complete normalization was not attained during the first six months following cast removal.

Bone Regeneration↗
PubMed1995

Vascularisation of the head of the radius in the adult.

Although rare, ischemic necrosis of the head of the radius after fracture is a theoretic possibility. The epiphyseal vascularisation of the proximal end of the radius was studied by dissection and diaphanisation techniques. The main extra-osseous supply is derived from epiphyseo-metaphyseal arteries given off by the recurrent radial a. and the first collateral of the ulnar a. These, to the number of three or four, anastomose together in a peri-cervical arterial circle continuous with the periosteal vessels of the shaft. From the proximal part of this network there arise three main intra-epiphyseal branches, which traverse the head, but nearly the entire periphery of the osteochondral junction is the site of small periosteal branches penetrating the head, though to no great depth. When the head of the radius is fractured, the commonest displacement is posterolateral, and the main vessel-bearing periosteal layer probably remains intact.

Aged↗
PubMed1992

[Results of a volar approach to plate osteosynthesis of radius shaft fractures. Theoretical basis--clinical results].

This retrospective study analyses the results of 80 shaft fractures of the radius treated by open reduction and plating by a volar approach. Studies about strain distribution on the radius shaft worked out a varying pattern of tensile forces and a continuously change of the tension bend side through full range of motion. So from the biomechanical aspect an ideal position for compression plating is not determined and dorsal or volar plating brings the same stability. The advantage of the volar approach by Henry is the possibility of an easy extension of the approach to the distal or proximal part of the forearm and an optimal covering of the plate by soft tissue. To expose the superficial radial nerve is obligate, if necessary the deep radial nerve should be exposed too in proximal fractures. From 1973 to 1987 80 fractures of the shaft of the radius were treated by plating using the volar approach, since 1977 3.5 dynamic compression plate of the AO was used exclusively. Only two non-unions occurred in the beginning when the AO's third tube plate was used routinely. One massive callus formation had to be noticed with a complete loss of pronation and supination. One infection occurred, but normal wound healing and bone union could be achieved after early reoperation. Two incomplete lesions of the superficial radial nerve were seen, but normal sensibility occurred spontaneously. No other neural or vascular complication had to be noticed using this approach. In the follow-up 56 patients were seen two to 14 years postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

Non-spanning external fixation of the distal radius.

Non-spanning external fixation of the distal radius is a simple, reliable, and noninvasive technique to restore the anatomy in unstable extra-articular or minimal articular fractures of the distal radius. Rehabilitation is faster and more complete than with other comparable techniques. It is also a successful technique for stabilization of corrective osteotomy of the distal radius formal union.

Contraindications↗
PubMed2004

Corrective osteotomy of malunited distal radius fractures using carbonated hydroxyapatite as an alternative to autogenous bone grafting.

PURPOSE: The purpose of the present study was to report on the author's experience using carbonated hydroxyapatite as a bony substitute in distal radius corrective osteotomies. METHODS: Six patients had a corrective osteotomy for a malunited distal radius fracture using carbonated hydroxyapatite as an alternative to an autogenous bone graft. Internal fixation of the osteotomy was achieved by using 2 or 3 K-wires. RESULTS: At an average follow-up evaluation of 33 months (range, 22-45 mo) all the osteotomies united. Wrist flexion-extension motion improved from 75 degrees to 110 degrees , forearm rotation increased from 116 degrees to 157 degrees , and grip strength had an average increase of 140% at the time of the final follow-up evaluation. All patients were satisfied and there were no reports of persistent pain. Radiographic evaluation showed an average volar tilt improvement from a preoperative dorsal angulation shifting into a neutral position in the sagittal plane; radial lengthening improved from an average of 4 mm (range, 2-6 mm) before surgery to 7 mm (range, 5-9 mm) after surgery, ulnar plus deformity improved by 5 mm. Radiographically the carbonated hydroxyapatite material was integrated completely into the bone tissue with evidence of progressive re-absorption and bony calcification over time. The Mayo wrist score system, according to Cooney and Krimmer modifications, improved by an average of 88 and 98 points (0-100 points), respectively. CONCLUSIONS: On the basis of this preliminary experience it is reasonable to consider carbonated hydroxyapatite as a viable alternative to bone grafting in conjunction with surgical correction of a distal radius malunion. It must be augmented, however, with internal fixation.

Adult↗
PubMed2005

Influence of distal radioulnar joint subluxation on restricted forearm rotation after distal radius fracture.

PURPOSE: To analyze the influence of subluxation of the distal radioulnar joint (DRUJ) on restricted forearm rotation after distal radius fracture. METHODS: Twenty-two cases of healed unilateral distal radial fracture with restricted forearm rotation were included in the study. The subluxation of the DRUJ was evaluated using helical computed tomography scan at neutral, maximum pronation, and maximum supination and presented as the percent displacement of the ulnar head in both the injured and uninjured sides. The radiographic parameters of palmar tilt, radial inclination, dorsal shift, radial shift, and ulnar variance were measured on plain x-ray films and the rotational deformity of the distal radius was evaluated from the computed tomography scan. The differences of each radiographic parameter from the uninjured side were calculated. The relationships between the restricted forearm rotation and the percent displacement of the ulnar head and each of the radiographic parameters were analyzed statistically. RESULTS: When forearm pronation was restricted the ulnar head was located palmarly at neutral, maximum supination, and maximum pronation with severe dorsal tilt of the distal radius. When supination was restricted the ulnar head was located dorsally at maximum supination with severe ulnar-positive variance. CONCLUSIONS: The subluxation of the DRUJ was related to restricted forearm rotation. The radiographic parameters of palmar tilt and ulnar variance showed an adverse influence on the position of the ulnar head at the DRUJ, which might lead to restricted forearm rotation after distal radial fracture.

Adult↗
PubMed2006

[Ilizarov reconstruction of the distal radius after resection of a giant-cell tumor: a case report].

We present a case of Ilizarov reconstruction after en bloc resection of the distal radius. An 8-cm resection was required to remove a giant-cell tumor. Reconstruction was based on the ascension technique using an Ilizarov external fixator after corticotomy of the proximal fragment of the radius. Satisfactory reconstruction with formation of a neoarticulation between the radius and the carpus was achieved. Satisfactory wrist function was achieved and the patient was recurrence free at five years. The arguments leading to this therapeutic option are discussed.

Biopsy↗
PubMed1989

Treatment of unstable Colles' fractures with a new radius mini-fixator.

An external fixator has been developed that is confined to the radius. It is lightweight, has a low profile, and its application is uncomplicated. Because the fixator provides rigid fixation of the fracture fragments, it has the important advantage of allowing immediate active wrist exercises, thus facilitating early restoration of mobility. The radius mini-fixator has been effective in the treatment of unstable Frykman Type I and II Colles' fractures that account for 36.3% in Frykman's series. It has also been used to stabilize osteotomies of the radius for malunited Colles' fractures.

Aged↗
PubMed2004

Strength prediction of the distal radius by bone densitometry--evaluation using biomechanical tests.

Osteoporotic fractures represent an important medical problem as they are often early predictors of future fractures at other skeletal sites. The distal radius is one such fracture site. To determine the individual's risk of fracture, different measurement techniques have been developed. These methods differ in physical background, measurement site, output parameters, and cost. If correctly applied, biomechanical testing can be an efficient tool for the preclinical evaluation of these techniques. With biomechanical testing it is possible to determine the structural strength of bone which can then be correlated with various densitometric parameters. Here we will review experimental work performed in this context. Biomechanical testing conditions vary considerably from study to study with 3-point bending (shaft), axial compression (metaphysis), and fall simulations being some of the techniques used. Experimental evidence suggests that site-specific osteodensitometric measurements can predict the mechanical strength of the distal radius with moderate to high accuracy, but that measurements at remote sites display considerably lower predictive value. Geometry-based parameters of cortical bone are also good predictors, but have not been shown to offer significant advantage over measurement of bone mass. Some (but not all) studies have found that quantitative ultrasound and microstructural parameters contribute significant additional information to bone mass measurement. The most accurate prediction of distal radius fractures, however, appears to be (patient-specific) microstructural finite element modeling.

Animals↗
PubMed2002

An analysis of bone stresses and fixation stability using a finite element model of simulated distal radius fractures.

A 3-dimensional finite element model was used to study pin fixation in simulated unstable extra-articular distal radius fractures. Bone geometry and material properties were generated from computed tomography. The model was validated in cadaver testing. The model is robust and an accurate predictor of bone stresses and fracture stability under pure axial load. Three different pinning configurations and 3 different pin materials were evaluated. Crossed pinning provided greater fracture stability and a broader distribution of bone stresses than pinning through the radius styloid alone. Steel pins provided greater fracture stability; however, bioabsorbable pins produced lower stress concentration in the bone near the pins. A finite element model is useful in showing differences between various pin constructs in the treatment of distal radius fractures.

Aged↗
PubMed1996

In vivo assessment of trabecular bone structure at the distal radius from high-resolution computed tomography images.

A dedicated computed tomography system was used to acquire transaxial images of the distal radius to assess trabecular bone structure in vivo. We segmented trabecular bone from the marrow and soft tissue background by postprocessing the image with a region grow and skeletonization step. From the processed image we assessed the integrity of the bone by examining the continuity of its trabecular network and by determining the area of the holes comprising its marrow space. The continuity of the bone imaged was assessed by a proposed connectivity index (CI) and the size of the marrow spaces was assessed by calculating a mean hole area (H(A)) in the bone cross-section. Repeat measurements revealed that the intra-subject variability in CI and H(A) was small (CV < 6%). Both CI and H(A) were sensitive enough to reflect differences in structure at the head of the radius and at several sites along its shaft. We tested the diagnostic value of assessing bone structure at the distal end of the radius by measuring trabecular bone density, CI and H(A) in a mixed group of 26 subjects, nine of whom had suffered a wrist fracture. We found that a trabecular bone density threshold of 116 mg cm-3, corresponding to two standard deviations below the mean density in the 17 non-fractured subjects, separated fractured from non-fractured subjects with a sensitivity of 22% and a specificity of 100%. A CI threshold of -4.7 doubled the sensitivity (44%) and maintained the 100% specificity. An H(A) threshold of 4.5 mm2 achieved a sensitivity of 89% and a specificity of 94%. This increased sensitivity achieved by our indices suggests that an in vivo assessment of trabecular bone structure can contribute significantly to the identification of persons at risk of fracture.

Adult↗
PubMed1997

Radiocarpal articular pressures during the reduction of distal radius fractures.

OBJECTIVES: To measure in vivo radiocarpal articular pressures during closed reduction and external fixation of distal radius fractures. DESIGN: Intraoperative measurements using a sterile pressure sensitive sensor specially constructed for this application. SETTING AND PATIENTS: Ten patients with a closed distal radius fracture stabilized by radiometacarpal external fixation. Radiocarpal pressures measured during transarticular distraction, wrist palmar flexion, wrist ulnar inclination, and fracture reduction. MAIN OUTCOME MEASUREMENTS AND RESULTS: Transarticular distraction resulted in a substantial decrease of the articular pressure, averaging -158.1 mmHg. Palmar flexion resulted in a mean pressure increase of 91.8 mmHg. The reduction of the fracture using a combination of distraction, palmar flexion and ulnar deviation resulted in either an increase or decrease of articular pressure, but always with a tendency toward progressive normalization of the pressure, with a mean slope of 3.2 mmHg/min. CONCLUSIONS AND CLINICAL RELEVANCE: The phenomena leading to the reduction of distal radius fractures could be related in part to a decrease of the intraarticular pressure, which may be responsible for a suction effect on the intraarticular bone fragments.

Adolescent↗
PubMed2005

Treatment of unstable extra-articular distal radius fractures by modified intrafocal Kapandji method.

The authors prospectively assess the results of surgically treated, unstable extra-articular distal radius fractures from 29 patients with good bone quality. Mean age was 49 years, ranging from 22 to 69 years; the female gender was the most frequently affected (58.6% of the cases). Surgical fixation was indicated for fractures presenting an angulation above 20 degrees , marked dorsal comminution, and radius shortening in excess of 10 mm on initial x-rays (anteroposterior and lateral views). The Kapandji technique, with intrafocal, nonthreaded Kirschner wires, was employed. Clinical data assessed anatomic aspects according to Scheck, functional aspect after Gartland and Werley, strength by Scheck's methods, and esthetic by Frykman's criteria. Functional assessment, according to Gartland and Werley, revealed 72.1% of excellent and good results at 3 months; 89.7% at 6 months; and 96.6% at 12 months. Immediate postoperative reduction was not maintained at the final follow-up at 12 months; however, that loss was not severe, and the anatomic outcome was good and excellent in 96.6% of the cases. Six patients presented complications. Four patients presented reflex sympathetic dystrophy; 1 patient had a superficial Kirschner wire infection, and another patient had radial nerve superficial branch paresthesia. The employed technique showed to be effective in the treatment of unstable, extra-articular fractures of the distal radius. It is easy to learn and to perform. The device employed has a low cost and is widely available in operation rooms.

Adult↗