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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
PubMed1995

Force and pressure transmission through the normal wrist. A theoretical two-dimensional study in the posteroanterior plane.

Force transmission through the wrist in the normal population was investigated using the rigid body spring modeling (RBSM) technique (assuming carpal bones are rigid bodies interposed by series of springs simulating articulating cartilage and constraining ligaments). One-hundred and twenty normal wrist posteroanterior X-rays of adults (evenly divided to represent both genders and two age groups) provided the anatomical data. Reaction forces between the carpal bones were modeled using a system of compression linear springs, representing cartilage and subchondral bone, and of tensile linear springs, representing ligaments. The spring constants were determined based on the material properties of wrist cartilage and ligaments. Assumed axial loads were applied along the metacarpals to simulate a grasp strength of 10 N with active stabilization of the wrist in neutral position. The force transmission ratio at the radio-ulno-carpal joint was 55% through the radio-scaphoid and 35% through the radio-lunate joints. The remaining 10% of the load was passing through the triangular fibrocartilage with minor differences between genders. Among the intercarpal joints, a large percentage of the load of the wrist was transmitted to the scaphoid. The peak pressure was highest at the proximal pole of the radio-scaphoid, with a radio-scaphoid versus radio-lunate peak pressure ratio of 1.6. The most important ligaments in terms of load transmission were those opposing ulnar translation of the carpus. The wrist morphology had little influence on the magnitude and pattern of load distribution. There was no effect of age on wrist force distribution.

Adult↗
PubMed1995

Rotational stability of the carpus relative to the forearm.

To perform rotational tasks adequately, the rotational laxity between the radius and the carpus must be constrained within a certain limit. The contribution of nine individual capsuloligamentous structures to the rotational stability of the radiocarpal joint was studied using 14 fresh-frozen human cadaveric specimens. Torque-rotation curves, with sequential section of the soft-tissue structures, were used to calculate the percentage contribution of each individual structure. The primary pronation constraint was the palmar radioscaphocapitate ligament. The contributions to supination constraint were more complex; the dorsal radiotriquetral ligament was dominant, assisted by the palmar ulnolunate ligament. Structures originating from the ulna changed their major constraint contribution with forearm orientation, whereas those with a radial origin had a constant contribution independent of forearm rotation. Injury of these structures may lead to rotational instability at the radiocarpal level and should be considered when treating carpal instabilities.

Adult↗
PubMed1995

Operative treatment of malunited fractures of the forearm.

We conducted a retrospective review of the results of twenty-seven consecutive osteotomies for malunited fractures of the forearm performed at the Mayo Clinic from 1976 to 1991. There were seventeen male patients and ten female patients who were an average of nineteen years old (range, nine to forty-one years old) at the time of the osteotomy. The corrective osteotomy was performed an average of seventy-three months (range, two to 324 months) after the fracture. The indication for the procedure was functional loss of motion (average arc of pronation-supination, 74 degrees; range, 20 to 120 degrees) in twenty patients, an unstable and painful distal radioulnar joint in six, and an unacceptable appearance of the forearm in one. Twenty patients had a corrective osteotomy of the radius; two, of the ulna; and five, of both bones. Of the twenty patients who had a corrective osteotomy for loss of motion of the forearm, nine were managed within twelve months after the initial injury and eleven were managed more than twelve months afterward. The patients who were managed early gained an average of 79 degrees (range, 20 to 160 degrees) of rotation after the osteotomy. Those who were managed late gained an average of only 30 degrees (range, -25 to 95 degrees). A pain-free, stable wrist was achieved in three of the six patients who were managed for an unstable and painful distal radio-ulnar joint. However, these six patients lost an average of 7 degrees (range, -25 to 25 degrees) of rotation of the forearm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Carpal instability non-dissociative.

A retrospective study of 45 patients with symptoms of wrist pain and weakness with clinical evidence of instability is presented. These patients had normal intrinsic interosseous ligaments demonstrated arthrographically or surgically. They were followed for a minimum of 18 months and an average of 5.8 years. All patients demonstrated instability of the proximal carpal row which is referred to as carpal instability non-dissociative (CIND). Seven patients were treated non-operatively and 38 were treated operatively. Surgical management consisted of soft tissue reconstruction directed at the area of instability in 34 cases, joint levelling osteotomy in six, three of whom also had soft tissue reconstructions, and mid-carpal fusion in one. The overall good and excellent results were a disappointing 56% and there was no significant difference between the non-surgical and surgical groups. The best results were found in the ulna-minus CIND patients who underwent a joint levelling osteotomy, with 83% good and excellent results. CIND is associated with extrinsic ligamentous laxity; however, significant difficulty exists in locating the precise areas of maximum pathology. This accounts for the unpredictable results of treatment. As our understanding of the pathomechanics of CIND improves, the treatment will become more specific and the results should improve.

Adolescent↗
PubMed1994

Lateral stability of proximal interphalangeal joint replacement.

The lateral stability of the cadaver proximal interphalangeal joint was studied with an electromagnetic tracking system before and after implant replacement. Ten middle fingers were retrieved and randomly divided into two groups for joint replacement with either a silicone rubber flexible finger joint implant or a custom surface replacement prosthesis. Each finger was mounted on a fixture that allowed loading of the proximal interphalangeal joint with tension through the flexor, extensor, and intrinsic tendons. For the intact proximal interphalangeal joint under lateral stress, lateral angulation averaged 4 degrees in extension and 8 degrees with the joint in 60 degrees of flexion. Although lateral angulation increased after surface replacement prosthesis implantation when the joint was flexed more than 20 degrees, comparison with the intact joint showed no statistical difference. With the silicone implant, lateral angulation became more pronounced even in the extended position and showed a significant difference when the proximal interphalangeal joint was flexed more than 20 degrees.

Cadaver↗
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↗