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Biomedical subjects

F Schuind

Publications and source records attributed to F Schuind.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Treatment principles in hand fractures].

The fractures of the hand are frequent and represent a problem of public health. The displacement of the fracture occurs because of post-traumatic musculo-tendinous imbalance. The fractures of the hand are to be treated according to four principles: anatomical reduction, followed, when possible, by immediate mobilization, if necessary, by immobilization of the injured parts in the "protective" position (metacarpophalangeal flexion, interphalangeal extension and with the first web space under stretch), and prevention of post-traumatic edema. When an osteosynthesis is performed, the mounting should be stable enough to allow early mobilization. The most useful techniques include external minifixation, and internal fixation using one or several screws.

Bone Screws↗
PubMed1996

[Biomechanics of the normal elbow and following total semi-constrained arthroplasty].

The elbow possesses two degrees of freedom: flexion-extension and pronation-supination. The axis of flexion-extension joins the centers of the capitellum and of the trochlea. The axis of pronation-supination passes through the head of the radius, and through the distal ulnar dome. The functional elbow mobilities include 100 degrees of elbow flexion (30 to 130 degrees) and 100 degrees of forearm rotation (50 degrees of pronation and 50 degrees of supination). The elbow is submitted to high articular contact forces. The joint stability depends on the articular surfaces, capsulo-ligamentous restraints and dynamic muscular contractions. As a practical application of this fundamental knowledge, an experimental study of the effects of total elbow arthroplasty on joint stability and muscle moment arms is reported, insisting on the deleterious effects of implant malpositioning.

Biomechanical Phenomena↗
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

Loose-hinge total elbow arthroplasty. An experimental study of the effects of implant alignment on three-dimensional elbow kinematics.

A previous study suggested that the kinematics of a loose-hinge total elbow arthroplasty (TEA) are those of a truly semiconstrained joint. This study addresses the effects of malposition of the implant. The three-dimensional elbow kinematics during simulated active motion were studied in six cadaver specimens using an electromagnetic tracking device. In addition to simulated active elbow flexion, flexion arcs were obtained under an elbow varus or valgus moment, to calculate the structural varus-valgus laxities. The results after four different Coondrad-Morrey TEA positions of implantation were compared with those of the intact elbow. The flexion-extension amplitudes were not significantly decreased after TEA implantation, except with external rotation of the ulnar component, which resulted in a loss of extension. In the intact elbow and after TEA implantation in any position, the mean varus-valgus deviations throughout elbow flexion were in a narrower range than the structural limits imposed by the ligaments (intact elbow) or the TEA hinge design. With internal malrotation of the humeral component over 10 degrees, however, the valgus structural limit was reached and, conversely, the varus limit with external rotation over 10 degrees. The clinical improvement observed with the semiconstrained TEA is derived from the benefits of the less constrained articulation. The proximodistal changes of TEA implantation have no consequence on the kinematic pattern. Rotational malpositioning of either humeral or ulnar component should be avoided, the first because it changes the kinematic pattern toward the structural limits of the implant and, therefore, may lead to excessive stresses at the bone-cement-implant interfaces and to early loosening, and the latter because it causes loss of extension.

Biomechanical Phenomena↗
PubMed1994

[Plexiform fibrohistiocytic tumor of the hand. Late form].

Plexiform fibrohistiocytic tumours are very rare, apparently benign neoplasms of the superficial soft tissue: only two series and one case report have been described in the literature. Macroscopically located within the dermis or superficial subcutis, they seem to predominate in the upper limbs of children and young adults. Moreover their recurrence rate is relatively high. We report the case of a 56 year old male patient presenting such a plexiform fibrohistiocytic tumour of the hand, which was surgically excised after a progressive clinical evolution of approximately 5 years and in which no recurrence has been observed with a follow-up of more than 24 months.

Follow-Up Studies↗
PubMed1993

Small external fixation devices for the hand and wrist.

Small external fixators have been developed for use in the hand and wrist. The main indications are stabilization of open or infected fracture or non-union of the metacarpals and phalanges; length maintenance in segmental bone loss; and distraction-lengthening of the fingers. The device may be used also for articular or periarticular fracture, closed diaphyseal fracture in adults, fracture in children, various arthrodeses, or corrective osteotomies.

Biomechanical Phenomena↗
PubMed1992

Flexor tendon forces: in vivo measurements.

S-shaped force transducers were developed for measurement of the forces along intact tendons. After calibration, the transducers were applied to the flexor pollicis longus and flexor digitorum superficialis and profundus tendons of the index finger in five patients operated on for treatment of carpal tunnel syndrome. The tendon forces generated during passive and active motion of the wrist and fingers were recorded. For pinch function, the amount of the applied load was measured with a special pinch meter. Tendon forces in the range of 0.1 to 0.6 kgf were measured during passive mobilization of the wrist. Tendon forces up to 0.9 kgf were present during passive mobilization of the fingers. Tendon forces up to 3.5 kgf were present during active unresisted finger motion. Tendon forces up to 12.0 kgf were recorded during tip pinch, with a mean applied pinch force of 3.5 kgf. These results have potential application in determining the amount of force that a tendon repair would have to resist during passive as well as active postsurgical mobilizations.

Carpal Tunnel Syndrome↗
PubMed1992

Vascularized bone transfer for tibial pseudarthrosis. Part II: Vascularized bone and muscle transfers. Exclusive free fibular bone graft.

The techniques of vascularized transfer of a bone segment, or of revascularization of a conventional bone autograft by a pedicle or a microsurgical muscular flap represent one of the most significant advances made during the last years for the treatment of large bone defects of the tibia with associated skin injury. The authors present their experience with 16 cases, including 5 microsurgical transfers.

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

External minifixation for treatment of closed fractures of the metacarpal bones.

External minifixators were used in the treatment of 63 closed diaphyseal metacarpal bone fractures. A simple half-frame configuration was applied in all the cases. Open reduction was performed in 26%. The mean duration of external fixation was 30 days. There were no cases of nonunion. Anatomical reduction was obtained in 86.6% of the cases. There were no cases of reflex sympathetic dystrophy. The general functional results were very good or good in 96.6%. Open reduction did not significantly alter the final results. External minifixation is usually accepted as a treatment of open metacarpal fractures. Because of the excellent results obtained in our series, we believe that the indications of external minifixation could be enlarged to closed metacarpal bone fractures.

Adolescent↗
PubMed1991

Treatment of forearm fractures by Hoffman external fixation. A study of 93 patients.

Ninety-three patients with acute fractures of the diaphysis of one or both bones of the forearm were treated by a Hoffmann external fixator, using a half-frame configuration. Whenever possible, closed methods of reduction were used. The versatility of the Hoffmann external fixator allows multiple attempts and possible secondary resumption of the reduction. The half-frame configuration is stable enough, allowing the restoration and maintenance of the precise anatomy of the forearm bones and early active postoperative motion. The median length of retention of the external fixator was 13 weeks. Because of the elastic type of fixation, a solid periosteal callus was usually obtained. Non-union occurred in 8.5% of the patients. One refracture at the former fracture site was observed.

Adolescent↗
PubMed1989

Single stage reconstruction of a large tibial defect using a free vascularised osteomyocutaneous ulnar transfer.

We present the case of a young man with 13 cm of bone and soft-tissue loss in the tibia and a severe traction injury of the brachial plexus. A free vascularised composite transfer of the bone and soft tissues of the ulnar side of the forearm was undertaken to reconstruct the defect. Bony union was achieved after a year and was followed by complete functional recovery of the lower limb.

Adult↗