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Biomedical subjects

S F Viegas

Publications and source records attributed to S F Viegas.

At least 55 records · Page 3Linked to original sources
PubMed1994

Midcarpal arthroscopy: anatomy and portals.

Arthroscopy of the midcarpal joint of the wrist is a relatively new procedure made possible by the advances and miniaturization of arthroscopic instrumentation. Only recently has even the basic variability in the normal anatomy of the midcarpal joint been delineated. Midcarpal arthroscopy is becoming a routine part of a complete diagnostic wrist arthroscopy and is offering good views of midcarpal anatomy and new opportunities for arthroscopic treatment of midcarpal and proximal wrist joint traumatic and degenerative pathology.

Arthroscopy↗
PubMed1993

Wrist anatomy: incidence, distribution, and correlation of anatomic variations, tears, and arthrosis.

We dissected 393 wrists to evaluate the incidence and distribution of anatomic features, arthrosis, chondromalacia, and soft tissue lesions. The data were then analyzed for any statistically significant associations among the different variables. The most common (73%) lunate morphology had a separate medial facet on its distal surface for the hamate. The capitate had a separate facet for the fourth metacarpal in 86% of the wrists. Fourth metacarpals with a dorsal radial facet, either separate from or connected to the rest of the fourth metacarpal base, were the most common types of fourth metacarpal. Cartilage erosion with exposed subchondral bone was identified in 58% of the wrists. It was most commonly at the proximal pole of the hamate (28%). Tears of the ligaments and/or the triangular fibrocartilage complex were identified in 56% of the wrists. The triangular fibrocartilage complex was found torn in 36% of the wrists. The lunotriquetral interosseous ligament was torn in 36% of the wrists, and the scapholunate interosseous ligament was torn in 28% of the wrists. There was a communication between the proximal wrist joint and the pisotriquetral joint in 88% of the 76 wrists, which were further dissected to assess this issue. Statistical analysis of the data found a significant correlation between the presence of cartilage erosion at the proximal pole of the hamate and the presence of a lunate facet. There was also a significant correlation between the presence of a tear in the scapholunate interosseous ligament and the presence of cartilage erosion in the scaphoid-trapezium-trapezoid joint. Analysis of the paired wrists from 169 cadavers revealed that the same soft tissue tear or combination of tears was present bilaterally in 39% of the pairs. Cartilage erosion was present bilaterally in the same location or locations in 27% of the pairs.

Adolescent↗
PubMed1993

Load mechanics of the midcarpal joint.

The midcarpal joint was studied in upper extremities of fresh cadavers with the use of a static positioning frame, pressure-sensitive film, and a microcomputer to analyze the contact prints. The contact area on the proximal side of the midcarpal joint was found to consist generally of four areas; the scaphoid-trapezium-trapezoid, the scaphoid-capitate, the lunate-capitate, and the triquetrum-hamate. The contact areas accounted for less than 40% of the available joint surface, even under loads of 118 pounds. The distribution of load through the midcarpal joint was scaphoid-trapezium-trapezoid 23%, scaphoid-capitate 28%, lunate-capitate 29%, and triquetrum-hamate 20%. The midcarpal joint, like the radiocarpal joint, appears to transmit load through distinct areas and through a relatively small portion of the available joint surface.

Biomechanical Phenomena↗
PubMed1993

Measurement of carpal bone geometry by computer analysis of three-dimensional CT images.

The aim of this project was noninvasively to analyze and quantitate the geometry, load transfer characteristics, and spatial relationships of the carpal bones by using a new three-dimensional CT scan reconstruction technique. The determination of mechanical parameters such as distances between centroids and between bone surfaces, carpal alignment, volumes, surface areas, and contact areas can provide the basis for comparison between normal wrists and wrists with a variety of progressive instability patterns, types of fracture, pathologic and posttraumatic states, and different simulated surgical procedures. This new technology has demonstrated a volumetric accuracy of 94% and a linear accuracy of 97%. Simultaneous analysis of all articulating surfaces of multiple joints can be performed in cadavers and in patients because of the noninvasive nature of the imaging reconstruction technique. This new research offers much more information than has previously been available. It also promises direct application to the clinical setting and eliminates several limitations and questions that were inescapable with previous technology.

Adult↗
PubMed1993

Wide scapholunate joint space in lunotriquetral coalition: a normal variant?

The radiologic appearances of 70 lunotriquetral coalitions in 52 patients were evaluated to determine whether a wide scapholunate joint space in subjects with this congenital abnormality reflects a scapholunate ligament disruption or is a normal variant. When the middle of the scapholunate joint space was larger than the capitolunate or third carpometacarpal joint space widths, it was considered to be abnormally wide. In 32 of 70 wrists (46%), a wide scapholunate joint space was detected. Results of instability radiographic series (n = 28) and arthrography (n = 11) were normal with respect to the scapholunate ligament in all cases, but the scapholunate joint space was markedly widened in six cases (55%) in which arthrography was performed. Arthroscopy, performed in one case, showed an intact scapholunate ligament. Because of the high prevalence of a wide scapholunate joint space and because of negative arthrographic and arthroscopic examinations, the authors conclude that widening of the scapholunate joint space is a normal variant that is common in patients with lunotriquetral coalition.

Adolescent↗
PubMed1992

Evolution of the power ("squeeze") grip and its morphological correlates in hominids.

The "squeeze" form of power grip is investigated for the purposes of clarifying the hand posture and activities associated with the grip, assessing the potential in chimpanzees for using the grip, and identifying morphological correlates of an effective power grip that may be recognized in fossil hominid species. Our approaches include: (1) the analysis of the human grip, focusing on both the hand posture involved and hand movements associated with use of the grip in hammering; (2) the analysis of similar chimpanzee grips and associated movements; (3) comparative functional analysis of regions in the hand exploited and stressed by the grip and its associated movements in humans; and (4) a review of the literature on the power grip and its morphological correlates. Results of the study indicate that humans use a squeeze form of power grip effectively to wield cylindrical tools forcefully as extensions of the forearm. Several morphological features occur in high frequency among humans which facilitate the grip and are consistent with the large internal and external forces associated with it in hammering and in other tool-using activities. Chimpanzee hand postures resembling this form of human power grip are not fully comparable and lack some of these morphological correlates that facilitate its use. The hand of Australopithecus afarensis does not appear to have been stressed by use of the grip, but there is some evidence for this type of stress in the metacarpals from Sterkfontein Member 4. Hands from Olduvai and Swartkrans do not provide sufficient evidence for assessment of power grip capabilities.

Adult↗
PubMed1992

Midcarpal arthroscopy: anatomy and technique.

Wrist arthroscopy has had a dramatic impact in both evaluation and treatment of a variety of wrist problems. Wrist arthroscopy has typically meant arthroscopy of the proximal wrist joint; however, midcarpal joint arthroscopy is becoming a routine part of a complete arthroscopic examination of the wrist. Specific indications, pertinent anatomy, and a clear technique for performing a midcarpal arthroscopy is not well documented in the literature. This article attempts to offer some insight on these issues.

Arthroscopes↗
PubMed1992

Carpal arch alteration and related clinical status after endoscopic carpal tunnel release.

One hundred eight endoscopic carpal tunnel releases were performed by a modification of the technique described by Chow. Eighty-seven of the 108 cases were evaluated for quantitative postoperative widening of the transverse carpal arch. The average postoperative widening of the transverse carpal arch was 0.17 cm (7%), with a range of 0 to 0.5 cm. Seventy percent of the patients showed 0% to 10% widening, 26% showed 10% to 20% widening, and 4% showed more than 20% widening of the transverse carpal arch. Preliminary findings show that 3 weeks after endoscopic carpal tunnel release, pinch strength was at 102% and grip strength at 86% of preoperative values. Six weeks after surgery, pinch strength was 106% and grip strength was 121% of preoperative values. The complication rate in this series was 3%. The transverse dimension of the carpal arch generally widens after endoscopic carpal tunnel release but to a lesser degree than has been reported for open carpal tunnel release. The rate of improvement of pinch and grip strength after endoscopic release is faster than that reported in the literature after open release.

Activities of Daily Living↗
PubMed1991

Simulated scaphoid proximal pole fracture.

Five fresh cadaver upper extremities were studied with use of a static positioning frame, pressure-sensitive film, a microcomputer-based videodigitizing system, and a Sun station image analysis system to assess the load bearing characteristics of the scaphoid in the proximal carpal joint. Specimens were studied in their normal condition, after a proximal pole osteotomy of the scaphoid, and after resection of the proximal pole of the scaphoid. The amount of contact area born through the scaphoid fossa was essentially the same whether the scaphoid was intact, or after a simulated scaphoid fracture of its proximal pole, or after resection of the proximal pole. The scaphoid contact area and pressure, although overall relatively constant, was redistributed after osteotomy, resulting in increased contact area under the distal fragment and no change or a slight decrease in the contact area under the proximal fragment of the scaphoid. After resection of the proximal fragment, all scaphoid contact area and pressure was born by the distal scaphoid fragment. The contact area and pressure characteristics of the lunate remained unchanged in all conditions compared with the normal condition. There were no significant changes in the locations of the centroids of the scaphoid segments and the lunate in any of the conditions tested.

Adult↗
PubMed1991

The fourth carpometacarpal joint.

The base of the fourth metacarpal and the corresponding hamate/capitate articulation were the areas of most significant variation in 142 cadaveric wrists that were dissected to assess the variation of the shapes of the second through the fifth carpometacarpal joints. Five different shapes of the fourth metacarpal base were identified. The base of the fourth metacarpal was generally either flat (85.9%) or conical (14.1%). There was a fourth metacarpal/capitate articulation present in 81.7% of the specimens. The presence or absence of a fourth metacarpal/capitate articulation and whether or not the fourth metacarpal base was flat or conical were easily identifiable on radiographs. Specific types of fourth metacarpal bases could not, however, be identified by radiography.

Adult↗
PubMed1991

The silicone scaphoid: a biomechanical study.

Five fresh cadaver upper extremities were studied by use of a static positioning frame, pressure-sensitive film, and a microcomputer-based videodigitizing system, to assess the load-bearing characteristics of a scaphoid silicone implant within the radioulnarcarpal joint. Specimens were studied in their "normal" condition, after resection of the scaphoid, after placement of a scaphoid implant, and with a scaphoid implant and a simulated capitate-lunate-triquetrum-hamate fusion. The scaphoid silicone implant bore significant, although less, load than the normal scaphoid. Decreasing the size of the scaphoid implant decreased the load born by the implant. Decreased load through the scaphoid implant was compensated by the lunate. The addition of a limited carpal fusion did not significantly decrease the load born by a scaphoid implant. Therefore, the silicone scaphoid implant is a load-bearing implant even when undersized or placed in association with a limited carpal fusion.

Adult↗
PubMed1991

Comparison of cortical and cancellous screw pull-out strengths about the posterior column and sacroiliac joint.

This study addresses the comparative pull-out strengths of cortical (4.5 mm) and fully threaded cancellous (6.5 mm) bone screws from sites about the pelvis commonly used in the fixation of posterior column acetabular fractures and sacroiliac (SI) disruptions. These sites include one from lateral to medial through the posterior column, two from posterolateral to anteromedial across the SI joint, one vertically through the sacral ala, and one vertically through the iliopubic column. Statistical analysis showed no significant difference in the force required for pull-out failure of the cortical versus the cancellous screws at any of the sites tested.

Acetabulum↗
PubMed1991

Wrist arthroscopy.

Explore the source record for details and available documents.

Arthroscopes↗
PubMed1990

Ulnar-sided perilunate instability: an anatomic and biomechanic study.

A staging system for ulnar-sided perilunate instability is presented based on a series of cadaver dissections and load studies. Stage I: partial or complete disruption of the lunotriquetral interosseous ligament, without clinical and/or radiographic evidence of dynamic or static volar intercalated segment instability deformity; stage II: complete disruption of the lunotriquetral interosseous ligament and disruption of the palmar lunotriquetral ligament, with clinical and/or radiographic evidence of dynamic volar intercalated segment instability deformity; and stage III: complete disruption of the lunotriquetral interosseous and the palmar lunotriquetral ligaments, attenuation or disruption of the dorsal radiocarpal ligament, with clinical and/or radiographic evidence of static volar intercalated segment instability deformity.

Adult↗
PubMed1990

Effects of distal radius fracture malunion on wrist joint mechanics.

An experimental model using a static positioning frame, pressure-sensitive film (Fuji), and a microcomputer-based videodigitizing system was used to measure contact areas and pressures in the wrist. Contact areas and pressures were compared in a group of wrists between the normal state and with simulated distal radius fracture malunions of varying degrees. In simulated malunions, radial shortening to any degree slightly increased the total contact area in the lunate fossa, and was significant at 2 mm of shortening. By angulating the distal radius more than 20 degrees either palmar or dorsal, there was a dorsal shift in the scaphoid and lunate high pressure areas, and the loads were more concentrated, but there was no change in the load distribution between the scaphoid and lunate. Decreasing the radial inclination shifted the load distribution so that there was more load in the lunate fossa and less load in the scaphoid fossa.

Adult↗
PubMed1990

Effects of radioulnar instability on the radiocarpal joint: a biomechanical study.

Five fresh cadaver upper extremities were studied with use of a static positioning frame, pressure-sensitive film and a microcomputer-based videodigitizing system to assess the effect of increasing radioulnar instability on the load distribution within the proximal carpal joint. Three stages of radioulnar instability were studied: (1) an avulsion fracture at the base of the ulna styloid; (2) an avulsion fracture at the base of the ulna styloid plus disruption of the dorsal portion of the distal radioulnar joint capsule; and (3) an avulsion fracture at the base of the ulna styloid, disruption of the dorsal portion of the distal radioulnar joint capsule, and disruption of the radioulnar interosseous membrane. All stages of radioulnar instability demonstrated a decrease in the lunate contact area in positions with the forearm in supination. In stage 3 instability there was also less lunate contact area in positions with the forearm in neutral pronation/supination. In stage 3 instability the lunate high pressure area centroid was abnormally palmar in all positions and the scaphoid high pressure area centroid was abnormally palmar in positions with the forearm in pronation or supination.

Adult↗