Biomedical subjects

Laurel Kuxhaus

Publications and source records attributed to Laurel Kuxhaus.

3 recordsLinked to original sources

PubMed2005

Coupling between wrist flexion-extension and radial-ulnar deviation.

BACKGROUND: Conventional wrist joint goniometry evaluates range of motion in isolated directions. The coupling between wrist flexion-extension and radial-ulnar deviation was investigated. METHODS: Ten healthy young male subjects performed wrist flexion-extension, radial-ulnar deviation, and circumduction motions. Flexion-extension and radial-ulnar deviation angles were computed from the coordinates of surface markers attached to the forearm and hand. A motion analysis system recorded marker motion. FINDINGS: During radial-ulnar deviation, the amount of accompanying flexion-extension movement was linearly related to the amount of radial-ulnar deviation. The secondary (flexion-extension) range of motion (48.3 degrees) was about 75% of the primary (radial-ulnar deviation) range of motion (55.1 degrees). During the flexion-extension task, the coupling was less linear. The motion range in radial-ulnar deviation (21.2 degrees) was about 20% of the primary (flexion-extension) range of motion (108.3 degrees). The radial-ulnar deviation and flexion-extension motions combined extension with radial deviation, and flexion with ulnar deviation. The convex hull of the flexion-extension and radial-ulnar deviation angles during circumduction was "egg-shaped" and asymmetric with respect to the anatomically defined flexion-extension and radial-ulnar deviation axes. Wrist position in one direction strongly influenced the range of motion in the other. Maximum range of motion in flexion-extension occurred with the wrist near the neutral radial-ulnar deviation position, and vice versa. Wrist deviation from neutral position in one direction diminished wrist range of motion in the other. INTERPRETATION: Wrist movements in flexion-extension and radial-ulnar deviation are coupled. Maximal wrist range of motion is near the neutral position. To account for the naturally coupled wrist motion in work station design and rehabilitation, the wrist should be placed at a neutral position.

Activities of Daily Living↗

PubMed2005

Quantifying deficits in the 3D force capabilities of a digit caused by selective paralysis: application to the thumb with simulated low ulnar nerve palsy.

We present the development of a vision-feedback method to characterize how selective paralysis distorts the three-dimensional (3D) volume representing digit-tip force production capability and its application to healthy individuals producing thumb-tip force with and without simulated low ulnar nerve palsy (LUNP). Subjects produced maximal static voluntary force spanning the transverse, sagittal and frontal planes of the thumb (16, 15 and 10 subjects, respectively). Subjects produced thumb-tip force tasks in guided and self-selected directions. The envelope (convex hull) of extreme forces in each plane approximated that cross-section of the 3D volume of force capability. Some subjects repeated the tasks with a temporary ulnar nerve block applied at the wrist to simulate complete acute LUNP. Three geometric properties of the force convex hull characterized each cross-section's shape: the ratios of its principal moments of inertia (RPMIs), the orientation of its principal axis (OPA), and its centroid location. Our results show that force production in the thumb's sagittal plane may be a reproducible and objective test to grade motor impairment in LUNP: paired t-tests of the larger RPMI in this plane best distinguished the nerve-blocked cases from the control cases in the guided task (p = 0.012), and Discriminant Analysis of the centroid location for the self-selected task in this plane correctly classified 94.7% of subjects into the control and ulnar nerve-blocked groups. We show that our method measures and detects changes in a digit's force production capabilities. Towards a clinical test of motor impairment in LUNP, this biomechanical study dictates which 3D thumb-tip forces to measure (those in the sagittal plane) and how to measure them (using the self-selected task).

Biomechanical Phenomena↗

PubMed2005

Quantifying the effect of the distal intrinsic release procedure on proximal interphalangeal joint flexion: a cadaveric study.

PURPOSE: The distal intrinsic release procedure is a popular treatment for intrinsic hand tightness. The literature remains ambiguous regarding the optimal amount of extensor hood to excise. Our goals were to quantify the mathematic relationship between the amount of extensor hood excised and proximal interphalangeal (PIP) joint flexion and to determine the minimum amount of extensor hood excision required to significantly change PIP joint flexion capability (the ability to achieve a change from the initial PIP joint angle). METHODS: We simulated the distal intrinsic release procedure by sequentially excising 5-mm strips (perpendicular to the long axis of the finger) of the extensor hood of cadaveric fingers beginning 5 mm proximal to the PIP joint center. We tensioned the intrinsic muscles to each digit to produce an intrinsically tight state and tensioned the flexor digitorum superficialis to produce an antagonist force and simulate the intrinsic tightness test. We measured PIP joint angle (the angle of the long axis of the middle phalanx relative to the proximal phalanx) in response to greater portions of excised extensor hood to quantify its contribution to intrinsic tightness. RESULTS: The relationship between the amount of extensor hood excised and the PIP joint flexion capability appeared quadratic, not linear. For the index, ring, and small fingers significant changes in PIP joint flexion were detected after resection of 59%, 26%, and 33%, respectively, of the extensor hood length. Although our results did not show statistical significance for the middle finger we project the critical amount to be at least 65%. CONCLUSIONS: We show PIP joint flexion changes after the distal intrinsic release procedure. We recommend excising a finger-dependent minimum amount of tissue before expecting a significant increase in PIP joint flexion capability.

Cadaver↗