Biomedical subjects

F W Werner

Publications and source records attributed to F W Werner.

At least 19 recordsLinked to original sources

PubMed1995

The stabilizing mechanism of the distal radioulnar joint during pronation and supination.

A biomechanical cadaver study was performed to determine the roles of the stabilizing structures of the distal radioulnar joint during pronation and supination. Subluxation and dislocation of the radius with respect to the ulna were evaluated in seven cadaver forearms placed in supination, pronation, and neutral forearm rotation. The amount of subluxation was measured with all structures intact, and after sectioning in various sequences the dorsal and palmar radioulnar ligaments, the distal portion of the interosseous membrane including the pronator quadratus, and the entire interosseous membrane. After sectioning two of any four structures, the distal radioulnar joint remained stable. When the interosseous membrane was disrupted first, the dorsal radioulnar ligament was found to be more important than the palmar radioulnar ligament in stabilizing the distal radioulnar joint in pronation, and conversely the palmar radioulnar ligament was more important than the dorsal radioulnar ligament in supination. Dislocation, and frequently diastasis, occurred only with sectioning of all four structures. This suggests that all four structures contribute to stability of the distal radioulnar joint.

Biomechanical Phenomena↗

PubMed1995

A dynamic biomechanical study of scapholunate ligament sectioning.

A biomechanical study was performed on fresh cadaver forearms to investigate the role of the scapholunate interosseous ligament in carpal stability. Scaphoid and lunate motion and radiocarpal and ulnocarpal pressure patterns were continually monitored while the wrist was moved physiologically. Prior to ligament sectioning, it was found that the position of the scaphoid and lunate were dependent on both the wrist position and the direction of wrist motion. Sectioning the scapholunate interosseous ligament caused increased scaphoid flexion, scaphoid pronation, and lunate extension. Pressure in the radiocarpal and ulnocarpal joint was redistributed following ligament sectioning. These findings support the clinical impression that the scapholunate interosseous ligament is an important stabilizer of the scaphoid and lunate.

Biomechanical Phenomena↗

PubMed1995

Relative articular inclination of the distal radioulnar joint: a radiographic study.

To determine the congruency of the distal radioulnar joint, 100 standardized normal wrist x-ray films were made and the following measurements taken: ulnar seat inclination, sigmoid notch inclination, and ulnar variance. The inclination angles were different in all but two cases. Relative to the long axis of the ulna, the sigmoid notch inclination averaged 7.7 degrees and the ulnar seat inclination averaged 21.0 degrees. There was a moderate correlation between the two inclination angles as well as between both sigmoid and ulnar seat inclination and ulnar variance. The data show that a wide variation between the inclination of the sigmoid notch and ulnar seat exists, which may explain why symptomatic articular incongruity can occur following ulnar shortening.

Adult↗

PubMed1994

Cortical and trabecular bone contribute strength to the osteopenic distal radius.

Fractures of the distal radius are common, especially in postmenopausal women, and their prevalence increases with age. Knowledge of the factors that increase the risk of fracture in this metaphyseal region would have predictive and therapeutic implications. Of particular interest in this study were (a) the relative contributions of cortical and trabecular bone to the strength of the distal radius and (b) the best radiographic features to use as strength indicators. In 21 forearms from fresh cadavera (median age at the time of death, 75 years), single photon absorptiometry and quantitative computed tomography were used to determine bone mineral content (BMC), density (BMC/W), and cross-sectional properties of the radius at distal and midshaft sites. Mechanical testing of the forearms then was used to determine the ultimate force and energy to cause the type of fracture that might be caused by a fall on the outstretched hand. Twelve of the 17 tested specimens sustained a fracture of the distal radius, and five sustained a fracture of the scaphoid. In the group of fractures of the distal radius, we found the cross-sectional area and moment of inertia of the cortical shell at the metaphyseal site to be better correlates of strength than the trabecular area and trabecular moment. In contrast, strength correlated much better with trabecular density than with cortical density. Overall, the best correlates of strength were the BMC and BMC/W at either the distal or proximal site. On balance, these results suggest that the thin cortical shell contributes substantially more to the mechanical strength of the distal radius than has been commonly appreciated.

Aged↗

PubMed1994

Biomechanics of the elbow and forearm.

The elbow joint functions as a link between the shoulder and wrist providing an exceptional amount of stability and motion. The elbow joint should not be considered a simple hinge joint; rather there are important out-of-plane motions that affect implant design and surgical reconstruction of the elbow. Forearm rotation, which occurs as the radius wraps around the ulna, guided by the soft tissues at the wrist and elbow joints, also contributes to upper extremity mobility. Force transmission in the forearm is a complex interaction of the radius, ulna, and interosseous membrane. Forces at the wrist affect the transmission of force through the forearm to the elbow joint. During some activities, forces at the elbow joint can reach several times body weight. These motion, stability, and force interactions allow for the forearm's function. It should be recognized that an event at the elbow joint affects the forearm and the wrist, and conversely injury or disease at the wrist joint can affect the elbow.

Biomechanical Phenomena↗

PubMed1993

Biomechanical evaluation of operative procedures to treat Kienböck's disease.

Operative procedures used to treat Kienböck's disease have been biomechanically evaluated experimentally. We have shown that joint leveling procedures, such as radial shortening and ulnar lengthening, experimentally unload the ulna and the radial lunate fossa. For wrists with neutral ulnar variance, a lateral opening or medial closing radial wedge procedure unloads the radial lunate fossa. Scapho-trapezio-trapezoidal fusion and scapho-capitate fusion also unload the radial lunate fossa but at the expense of loading the adjacent joints. Neither a capitate-hamate fusion nor a carpal tunnel release alter the radial ulnar carpal joint loading.

Arthrodesis↗

PubMed1992

Force transmission through the distal ulna: effect of ulnar variance, lunate fossa angulation, and radial and palmar tilt of the distal radius.

The relationship between the amount of force transmitted through the distal ulna and seven radiologically apparent anatomic parameters (ulnar variance, radial tilt, palmar tilt, lunate fossa angulation, carpal height, carpal ulnar distance, and ulnar head inclination) was examined in 58 fresh cadaver forearms. A positive, although very weak, relationship was found between the amount of force and the ulnar variance (r = 0.44). This suggests that a clinically more positive ulnar variant wrist will not necessarily cause more force to be transmitted to the head of the ulna than a wrist with a more negative ulnar variance, primarily because the triangular fibro-cartilage complex is thicker in arms with a more negative ulnar variance. Changes in ulnar variance of a forearm due to ulnar lengthening or radial shortening do, however, dramatically alter the force transmission. No other relationships were found between the ulnar force and the other radiologic parameters.

Analysis of Variance↗

PubMed1992

Distribution of pressures and forces on the wrist after simulated intercarpal fusion and Kienböck's disease.

Limited intercarpal fusion has been recommended for the treatment of Kienböck's disease. The effects of a simulated scapho-trapezio-trapezoid (STT) fusion and simulated Kienböck's disease on the biomechanics of the radio-ulno-carpal joint were investigated. The percent force, the centroid of the force, and the percent contact area in each fossa were determined. It was found that a STT fusion with the scaphoid in a neutral or extended position unloads the lunate fossa. STT fusion in flexion does not affect lunate load. It is concluded from this biomechanical experiment that STT fusion with the scaphoid in a neutral or extended position unloads the radiolunate joint regardless of the condition of the lunate. This load is shifted to the radioscaphoid articulation.

Arthrodesis↗

PubMed1992

Anatomic and biomechanical analysis of the arthroscopic wafer procedure.

The ulnar impaction syndrome is a common clinical entity that is most often associated with positive ulnar variance and is characterized by triangular fibrocartilage complex (TFCC), lunate, and/or distal ulnar pathology. Traditional treatment for symptomatic ulnar impaction syndrome has been conservative; however, in cases refractory to nonoperative management, formal ulnar shortening has been successful in long-term clinical series. Recently, arthroscopic ulnar shortening, the "arthroscopic wafer procedure" (AWP) (debridement of the perforated TFCC margins and limited ulnar head resection using a motorized burr) has become an option to treat this clinical syndrome. In an attempt to evaluate the biomechanical efficacy of the AWP, an experimental study was undertaken using nine ulnar positive cadaver forearms. Each specimen was evaluated biomechanically using axial load cells and pressure-sensitive film to evaluate the effect of serial resection of the TFCC and distal ulna on axial load and ulnar carpal pressures. The results of this experimental study revealed a statistically significant unloading of the ulnar aspect of the wrist after excision of the centrum of the TFCC and resection of the radial two-thirds width of the ulnar head, to a depth of subchondral bone resection. Furthermore, additional bony resection tended to correlate favorably with the stage of TFCC pathology noted, i.e., the more advanced the stage, the more resection necessary to unload the ulnar aspect of the wrist. Based on this biomechanical study, a limited clinical series has been initiated with early favorable results. The AWP biomechanically unloads the ulnar carpal complex, and therefore has a theoretical potential of relieving the symptoms of the ulnar impaction syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Arthroscopy↗

PubMed1992

A technique for measuring absolute toe pressures: evaluation of pressure-sensitive film techniques.

Although a number of pathologies of the forefoot in ballet dancers on pointe have been described, pressures and deforming forces have not been adequately measured. To evaluate the possible use of pressure-sensitive film (PSF) in measuring the pressures on the external soft tissues in such a confined space as the dancer's toe shoe, it was tested and calibrated with 20 cadaver toes. Each cadaver toe was internally stabilized and loaded longitudinally against PSF on a flat surface. The resultant films were analyzed with a video imaging system and the pressures and total forces were determined. Results showed that the linearity of the PSF to pressure had a regression value of 0.98. By using two sensitivity ranges of films, the total force measured by the PSF was found to be within 10% of the known applied force on each toe. The PSF, therefore, may very well be a useful and accurate method of measuring external soft tissue pressures on the forefoot.

Biomechanical Phenomena↗

PubMed1992

Knee extensor mechanics after subtotal excision of the patella.

Two sets of six fresh frozen autopsy specimens were used to test the quadriceps force requirements for knee extension after sequential distal-to-proximal and proximal-to-distal excisions of the patella. The quadriceps force as a function of knee flexion angle was recorded for varying amounts of excision and compared with the results for total patellectomy. Excision of the proximal one half or less resulted in lower force requirements when compared with total patellectomy. The effects of removal of the proximal three-fourths length of patella were inconsistent and actually increased the force requirements in three knees. The effects of distal to proximal excisions indicate a biomechanical advantage to maintaining a fragment equal to at least three fourths the length of the proximal patella. Retaining a fragment of adequate size preserves at least some of the mechanical advantage provided by the intact patella.

Aged↗

PubMed1991

Analysis of the forefoot on pointe in the ballet dancer.

The forefoot positions of nine ballet dancers standing on pointe were determined using a mold technique. These molds revealed three positions of the toes: (1) no crossing of the three medial toes; (2) crossing of the third toe behind the second; and (3) crossing of the hallux partially in front of the second. Almost half of all the toes seen on the molds had some deformation of the toenails. These molds also indicated a wide variability in the amount and location of contact between the shoes and toes.

Adolescent↗

PubMed1989

Frequency spectrum analysis of wrist motion for activities of daily living.

A frequency spectral analysis was performed on wrist motion data for 24 activities of daily living (ADLs). Wrist motion was measured using a triaxial electrogoniometer attached to the wrist using tape (for 12 subjects) and pins (for one subject). Results show that the average predominant frequency component of these ADLs was approximately 1 Hz with 75% of the spectral energy less than 5 Hz. The taped-on electrogoniometer, when compared with the pinned electrogoniometer, was adequate for calculating the predominant frequency component and spread of spectral data, but overestimated the magnitudes of the maximum spectral density and total area of the spectral curves. This discrepancy was largest for axial rotation.

Activities of Daily Living↗

PubMed1989

Pressures in the distal radioulnar joint: effect of surgical procedures used for Kienbock's disease.

Radial shortening and ulnar lengthening are two accepted surgical methods for treating Kienbock's disease. The effect of these procedures on the pressure within the distal radioulnar joint between the ulnar head and the sigmoid notch of the radius was experimentally evaluated in six fresh cadaver forearms. Radical shortening and ulnar lengthening led to increased pressure at the distal radioulnar articulation and caused shifting of the location of the center of pressure distally within the sigmoid notch. Radial displacement of the distal radial fragment at the time of radial shortening, however, decreased the peak pressures. Based on these experimental data, ulnar lengthening and radial shortening can be expected to alter the normal biomechanics of the distal radioulnar joint.

Aged↗

PubMed1988

Partial excision of the triangular fibrocartilage complex.

A cadaver model was used to evaluate the effect of partial excision of the triangular fibrocartilage complex (TFCC) on ulnar wrist kinetics. Excision of less than two thirds of the horizontal portion of the TFCC was found to have no statistical effect experimentally on forearm axial load transmission. This data supports, from a biomechanical standpoint, partial excision of the central portion of the TFCC--a procedure advocated clinically by some for treatment of a central TFCC perforation.

Biomechanical Phenomena↗

PubMed1987

Limited wrist arthrodesis: a laboratory study.

By means of an external fixator, 11 limited wrist "fusions" in eight freshly frozen cadaver wrists were studied. An electrogoniometer measured perfusion and postfusion range of motion, and the percentage of loss of motion was determined and then averaged for all eight wrists. The three fusions that crossed the radiocarpal row lost approximately 55% flexion/extension (F/E). The five fusions that crossed the intercarpal row lost approximately 27% F/E, and the three fusions within a single carpal row lost approximately 12% F/E. These results may be helpful to determine which limited wrist fusion to perform.

Arthrodesis↗

PubMed1987

A biomechanical study of distal radial fractures.

In an attempt to explain disability in dorsally angulated malunited distal radius fractures, an experiment was designed to evaluate load patterns about the wrist with varying degrees of dorsal angulation of the distal radius. Osteotomies were made in the distal radius of fresh cadaver arms after a modified external fixator was applied to the radius and load cells applied to the proximal radius and ulna. Pressure-sensitive film was inserted into the radioulnar carpal joint. After a predetermined load was applied to the wrist it was found that the load through the ulna increased from 21% to 67% of the total load as the angulation of the distal radial fragment increased from 10 degrees of palmar tilt to 45 degrees of dorsal tilt. The pressure distribution on the ulnar and radial articular surfaces changed in position and became more concentrated as dorsal angulation increased.

Biomechanical Phenomena↗

PubMed1986

Mechanical factors in electrode-induced osteogenesis.

Previous experiments have suggested that mechanical activity of electrode implants may contribute to the observed bone formation that has been attributed to the electrical currents. This was tested by implanting movable and stationary wires in the medullary canal of the rabbit femora or tibiae. The moving implants uniformly showed significant medullary bone formation at the wire, whereas the stationary ones did not. This bone persisted for as long as 8 weeks and was mostly resorbed by 12 weeks as the implants became fixed. The new trabecular bone closely resembled that typically seen at electrically active implants. Implant motion may have a more important role in electrically induced osteogenesis than previously thought.

Animals↗