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Biomedical subjects

R L Linscheid

Publications and source records attributed to R L Linscheid.

At least 19 recordsLinked to original sources
PubMed1992

Pisiformectomy in young patients.

Pisotriquetral arthrosis in young patients is considered rare and the diagnosis may be difficult to distinguish from other ulno-carpal problems. 12 patients under 40 years of age (15 cases) who underwent pisiformectomy were reviewed at a mean of 41 months. Patients with a good history of trauma and a positive response to intra-articular local anaesthetic injection did well. Others with an indefinite history and bilateral symptoms did not do so well. Trispiral tomography is the radiological investigation of choice.

Adult↗
PubMed1992

Changes in wrist and forearm configuration with grasp and isometric contraction of elbow flexors.

The purpose of this study was to determine the changes in wrist and forearm configuration with grasp and elbow flexor contraction by analysis of resting and grasping x-ray films of 15 normal adults and forearm scanograms of 10 other normal subjects. With grasp, a significant proximal migration of the radius (averaging 0.9 mm), a decrease in the carpal height ratio, and an increase in the lunate uncovering index were observed. With flexor contraction, there was a significant decrease in the forearm interosseous space.

Adult↗
PubMed1992

Nonoperative treatment of acute hamate hook fractures.

Six patients with acute and two patients with subacute nondisplaced fractures of the hamate hook were treated with immobilization. The patients with acute fractures were treated within 7 days of the injury, and those with subacute fractures were treated after 7 days. Seven of the eight patients showed documented healing of their fractures. At follow-up (average 8 months) all seven were free of symptoms. One patient with a subacute fracture did not comply with treatment and had a painful nonunion. Our results show that hamate hook fractures that are diagnosed early may heal with nonoperative management. Fractures that fail to heal with immobilization or those with chronic nonunion should be treated with excision of the hook fragment.

Acute Disease↗
PubMed1992

Comparative flexor tendon excursion after passive mobilization: an in vitro study.

Two experimental studies were conducted to investigate flexor tendon excursions. In the first study, tendon excursions due to passive joint motion in various loading condition were evaluated. In the second study, the efficacy of a new technique that used synergistic wrist motion (S-splint) was compared with the traditional dorsal splinting methods: the Kleinert splint (K-splint) and the Brooke Army Hospital/Walter Reed modified Kleinert splint with a palmar bar (P-splint). The results of these studies question the anticipated tendon excursion associated with postoperative splinting. They demonstrated that the measured tendon excursion under a condition of low tendon tension was almost half that of theoretically predicted values. In zone II, the magnitude of excursion introduced by the three mobilization methods were in descending order: S-splint, P-splint, K-splint (p less than 0.05). Differential tendon excursion between the flexor digitorum profundus and the flexor digitorum superficialis had a mean value of 3 mm and was not significantly different among the three methods. Passive proximal interphalangeal joint motion was the most effective means of providing increased amplitude of tendon gliding in zone II. Passive distal interphalangeal joint motion did not increase excursion in zone II as much as had been predicted.

Cadaver↗
PubMed1992

Force distribution across wrist joint: application of pressure-sensitive conductive rubber.

A new pressure-sensitive conductive rubber sensor was used for investigation of the pressure distribution through the radio-ulno-carpal joint. Twelve of these transducers were placed in the radio-ulno-carpal joint. Pressure was measured in seven different wrist positions under loads incrementally increasing from 0 to 12 kg. Half of the sensors showed less than 0.5 MPa, even at maximum load, while a high-pressure area was located palmary in each fossa. The peak pressure measured in the wrist neutral position was 2.4 MPa on the scaphoid fossa, 1.5 MPa on the lunate fossa, and 1.1 MPa on the triangular fibrocartilage with a 10 kg load. The peak pressure ratio between the scaphoid and the lunate was 1.7 in the neutral wrist position. This increased in radial deviation to 2.9 and decreased in ulnar deviation to 0.8. The force-transmission ratio was 50% through the scaphoid fossa, 35% through the lunate fossa, and 15% through the triangular fibrocartilage in the neutral position. The advantage of this sensor is that it is thin and flexible and provides reliable reproducible quasi-instantaneous measurements.

Biophysical Phenomena↗
PubMed1992

A normal data base of posteroanterior roentgenographic measurements of the wrist.

In 120 adults, we measured the dominant wrist on posteroanterior roentgenograms in order to determine the normal dimensions and variations according to age and sex. Men and women were equally represented as were two age-groups (twenty-five to forty years and forty-one to sixty years). The roentgenograms were made, with standard exposure and development techniques, with the wrist and forearm in a neutral position and the x-ray tube aligned vertical to the radial styloid. The roentgenogram that was made with the wrist in the mid-coronal plane was digitized and was used to measure distances between specified landmarks. The mean ulnar variance was -0.9 millimeter (normal range, -4.2 to 2.3 millimeters). The average carpal height ratio was 53 per cent (normal range, 46 to 61 per cent). The mean radial inclination was 24 degrees (range, 19 to 29 degrees). The carpal-radial and carpal-ulnar ratios were smaller in women. The width of the distal radio-ulnar joint was reduced in the older subjects. There was a significant positive relationship (p < 0.0001) between the maximum force reached and the length of the third metacarpal. We believe that information concerning the normal roentgenographic measurements and relationship between the bones of the wrist can be used (1) to follow the progression of carpal instabilities, osteonecrosis, osteoarthrosis, or rheumatoid arthritis; (2) in clinical research; and (3) in the design of wrist implants.

Aged↗
PubMed1992

Treatment of scapholunate dissociation. Rotatory subluxation of the scaphoid.

The treatment of scapholunate dissociation remains controversial. Although good to excellent results have been reported using a variety of surgical techniques, they have often not been confirmed by other authors. Limited wrist mobility and the likelihood that degenerative changes will progress appear to be inherent in most approaches. The ideal treatment is to restore the normal anatomy and, with it, the function of the wrist. Destroying a normal joint by even a limited fusion as a means to provide stability to an abnormal joint is counter to our usual approach to disease. It is for that reason that more reliable soft-tissue reconstructive procedures are necessary. Those interested in arthroscopy are pursuing endoscopic methods of repair, but, at present, little progress is apparent. The physician who solves this problem with an uncomplicated and reliable surgical solution will have indebted us all.

Acute Disease↗
PubMed1992

Biomechanics of the distal radioulnar joint.

The distal radioulnar joint (DRUJ) is a complex joint involved in pronosupination and ulnocarpal motion and support. The ulnar head, in a rolling, sliding motion, moves from the dorsal to the volar rim of the sigmoid notch as the joint moves from pronation to supination. The triangular fibrocartilage (TFC) is taut first dorsally and then volarly in the same sequence. The ulnar carpus is supported variably, as a function of ulnar length relative to the radial articular surface, by the pole of the distal ulna through the TFC. The TFC does not resist the pistonlike movement of the DRUJ, which occurs under dynamic loading. The coronal alignment of the DRUJ minimizes shear stress on the articular surfaces because of its alignment with the rotational axis of the forearm. Ulnar variance is a factor in the development of several clinical conditions.

Biomechanical Phenomena↗
PubMed1991

Correlation of physiological cross-sectional areas of muscle and tendon.

Muscle physiological cross-sectional area, as defined and measured by dividing the volume of the muscle by its fibre length, is proportional to the maximum strength of the muscle. It is one of the important parameters when considering muscle mechanics in sports science and, clinically in tendon transfer procedures. This study reports that tendon cross-sectional area correlated well with the physiological cross-sectional area of associated muscles.

Adult↗
PubMed1991

Concomitant scapholunate dissociation and Kienböck's disease.

Six men had concurrent scapholunate dissociation and Kienböck's disease, a finding suggestive of a common cause. Five patients attributed the onset of wrist pain to a single traumatic event. Three had x-ray evidence of scapholunate dissociation before the onset of lunate osteonecrosis. Biomechanical factors that may be of significance are ulnar minus variance, lesser compliance of the triangular fibrocartilage, ulnar translation of the carpus at impact with shear fracture through the lunate, and disruption of the scapholunate interosseous membrane occurring under similar stress. Lunate osteonecrosis may depend on a susceptible vascular pattern or intraosseous injury or both. The development of lunatomalacia complicates an already unstable wrist. Treatment options vary according to the clinical stages of each condition, although contrasting treatments have not established optimal care.

Adult↗
PubMed1991

The distal radioulnar ligaments: a biomechanical study.

The mechanical roles of the triangular fibrocartilage have been examined in three experiments. Kinematic analysis by a stereophotogrammetric method revealed that the palmar radioulnar ligament was taut in supination and that the dorsal radioulnar ligament was taut in pronation. In full pronation, the palmar radioulnar ligament decreased to an average of 71% of its length in tension. In full supination, the dorsal radioulnar ligament decreased to an average of 90% of its length. Mechanical testing of the triangular fibrocartilage under axial load disclosed a significant laxity (mean: 10.4 mm), which was decreased in pronation. Transverse loading tests demonstrated that the triangular fibrocartilage is less stiff in neutral forearm rotation. Study of the material properties of the palmar and dorsal parts of the triangular fibrocartilage showed these structures to be strong ligaments with material properties similar to those of the radiocarpal ligaments.

Biomechanical Phenomena↗
PubMed1991

Extensor mechanism of the fingers. I. A quantitative geometric study.

A close-range stereophotogrammetric measurement system was used to determine the three-dimensional geometric characteristics of the extensor assembly in seven human finger specimens and five finger configurations. The numerical data obtained showed that, although changes in length of the different bundles are small, their spatial orientation varies considerably from one to another position. This information should help to improve the accuracy of models derived to understand the extensor assembly behavior in normal and pathological conditions.

Fingers↗
PubMed1991

Extensor mechanism of the fingers. II. Tensile properties of components.

Seven fresh human finger specimens have been studied to determine the differences in structural stiffness between different components of the extensor assembly. Differences were found to be significant, ranging from an average of 275 N/mm for the proximal and distal segments of the central band to an average of 40 N/mm for the central-to-lateral intercrossing fascicles. The terminal tendon of the lateral band was shown to be as stiff as the middle segment of the central band.

Fingers↗
PubMed1991

A kinematic study of luno-triquetral dissociations.

An analysis of carpal motion after sectioning the ligamentous support of the luno-triquetral joints was done by use of stereoradiographic methods. The ligaments were sectioned in two stages. In stage I, a complete sectioning of both the dorsal and palmar luno-triquetral ligaments and the interosseous membrane was done. Stage II consisted of further sectioning of both the dorsal radio-triquetral and dorsal scapho-triquetral ligaments. After both stage I and stage II ligament sectioning, all of the intercarpal joints exhibited altered kinematics. The changes were especially marked at the luno-triquetral joint where motion was increased in all planes of wrist motion. The essential lesion in producing a static palmar flexed intercalated segment instability was division of the dorsal radio-triquetral and dorsal scapho-triquetral ligaments in association with the luno-triquetral ligaments and interosseous membrane sectioning.

Cadaver↗
PubMed1991

Preiser's disease.

Nine patients with the diagnosis of unilateral Preiser's disease were seen between 1970 and 1987. The mean age of four male and five female patients was 37 years (range, 20 to 70 years). The diagnosis was based on radiographic evidence of sclerosis, fragmentation, erosion, and collapse of the proximal pole of the scaphoid. Onset was usually insidious but two had a preexisting radial hypoplasia, a third had a modest scaphoid malunion, and a fourth had a recent fall. Treatment consisted of scaphoid excision and silicone rubber prosthetic replacement in three, debridement of necrotic bone fragments in one, and different periods of cast support and observation in the remaining five. No relationship to ulnar variance was seen. Mean follow-up was 6.9 years. Of the scaphoid implants, two had subluxated, but only one was painful. In the more conservatively treated group, pain and function were only modestly limiting in four, who returned to their original occupations as did the one treated by curettage of necrotic bone in the proximal pole. One patient (case 4) was severely incapacitated because of associated severe congenital anomalies of the lower extremities. Polyaxial tomography permitted a better assessment of the degree of involvement and carpal alignment. Preiser's disease is a rare affliction of the carpal scaphoid which may involve the entire bone in avascular changes but primarily leads to fragmentation and collapse of the proximal pole. A conservative approach to treatment is favored based on this experience.

Adult↗
PubMed1990

Effect on force transmission across the carpus in procedures used to treat Kienböck's disease.

A simplified two-dimensional articulating force analysis (rigid body spring model) examined how different surgical procedures used for treating Kienböck's disease modify the force distribution across the carpus. A two-dimensional model of a carpus was loaded through the metacarpals by forces of up to 143 Newtons. The resulting intercarpal displacement and joint loadings were calculated for the intact wrist and for different simulated surgical procedures. The predicted total amount of force transmitted through the radio-lunate joint of the intact wrist averaged a 32% of the total radio-ulno-carpal joint load. Limited intercarpal fusions were found to reduce compressive loading at the radio-lunate joint by no more than 15% of the original load. Capitate shortening was successful in relieving radio-lunate forces, however, it dramatically overloaded the adjacent scapho-trapezial and triquetral-hamate joints. By contrast, a 4 mm lengthening of the ulna (or shortening of the radius) resulted in a 45% reduction of radio-lunate load with only moderate changes in force at the midcarpal and radio-scaphoid joints. On the basis of this study, radial shortening or ulnar lengthening significantly unload the lunate and are rationale procedures in the treatment of Kienböck's disease. Limitations regarding direct clinical application of this mathematical model are also discussed.

Analysis of Variance↗