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Research Papers

The Envelope of Physiological Motion of the First Carpometacarpal Joint

[+] Author and Article Information
Joseph J. Crisco

Mem. ASME
Bioengineering Laboratory,
Department of Orthopaedics,
The Warren Alpert Medical School of
Brown University and Rhode Island Hospital,
1 Hoppin Street, CORO West Suite 404,
Providence, RI 02903
e-mail: joseph_crisco@brown.edu

Tarpit Patel, Eni Halilaj

Bioengineering Laboratory,
Department of Orthopaedics,
The Warren Alpert Medical School of
Brown University and Rhode Island Hospital,
1 Hoppin Street, CORO West Suite 404,
Providence, RI 02903

Douglas C. Moore

Bioengineering Laboratory,
Department of Orthopaedics,
The Warren Alpert Medical School of
Brown University and Rhode Island Hospital,
1 Hoppin Street, CORO West Suite 404, Providence, RI 02903

1Corresponding author.

Manuscript received January 10, 2015; final manuscript received July 17, 2015; published online August 6, 2015. Assoc. Editor: Zong-Ming Li.

J Biomech Eng 137(10), 101002 (Aug 06, 2015) (8 pages) Paper No: BIO-15-1008; doi: 10.1115/1.4031117 History: Received January 10, 2015

Much of the hand's functional capacity is due to the versatility of the motions at the thumb carpometacarpal (CMC) joint, which are presently incompletely defined. The aim of this study was to develop a mathematical model to completely describe the envelope of physiological motion of the thumb CMC joint and then to examine if there were differences in the kinematic envelope between women and men. In vivo kinematics of the first metacarpal with respect to the trapezium were computed from computed tomography (CT) volume images of 44 subjects (20M, 24F, 40.3 ± 17.7 yr) with no signs of CMC joint pathology. Kinematics of the first metacarpal were described with respect to the trapezium using helical axis of motion (HAM) variables and then modeled with discrete Fourier analysis. Each HAM variable was fit in a cyclic domain as a function of screw axis orientation in the trapezial articular plane; the RMSE of the fits was 14.5 deg, 1.4 mm, and 0.8 mm for the elevation, location, and translation, respectively. After normalizing for the larger bone size in men, no differences in the kinematic variables between sexes could be identified. Analysis of the kinematic data also revealed notable coupling of the primary rotations of the thumb with translation and internal and external rotations. This study advances our basic understanding of thumb CMC joint function and provides a complete description of the CMC joint for incorporation into future models of hand function. From a clinical perspective, our findings provide a basis for evaluating CMC pathology, especially the mechanically mediated aspects of osteoarthritis (OA), and should be used to inform artificial joint design, where accurate replication of kinematics is essential for long-term success.

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References

Figures

Grahic Jump Location
Fig. 3

Azimuth distribution functions of all subjects for each computed transform (neutral to flexion: N to F, neutral to adduction: N to Ad, neutral to extension: N to E, neutral to abduction: N to Ab, extension to flexion: E to F, abduction to adduction: Ab to Ad, extension to abduction: E to Ab, abduction to flexion: Ab to F, adduction to extension: Ad to E, and flexion to adduction: F to Ad). The azimuth orientation of the screw axis is specified by the TCS with idealized motion directions from the neutral to pure abduction (ABTCS), extension (ETCS), adduction (AdTCS), and flexion (FTCS) at azimuth angles of 180 deg, −90 deg, 0 deg, and 90 deg, respectively.

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Fig. 2

Volar view of the trapezium with the TCS (a). The +X direction is volar, +Y direction is proximal, and +Z direction is radial. The orientation of the screw axes (HAM) was described by two angles: an azimuth angle (azi) within the X–Z (trapezial) plane (0 deg aligned with the positive x-axis) and an elevation angle (ele) out of the X–Z plane. In a schematic distal-to-proximal view of the TCS (b), the screw axes for the idealized motions of pure flexion (FTCS), adduction (AdTCS), extension (ETCS), and abduction (ABTCS) were directed along the Z (azi = 90 deg), X (azi = 0), −Z (azi = −90 deg), and –X (azi = 180 deg) axes, respectively. The screw axes for these pure motions are labeled and the direction of rotation about the screw axis is illustrated using the right-hand rule (thumb along the axis, fingers curling in the positive direction of thumb rotation).

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Fig. 1

Surface renderings (a) and density-based renderings (b) from CT images acquired at the targeted thumb positions of neutral (N), flexion (F), adduction (Ad), extension (E), and abduction (Ab). The horizontal and vertical polycarbonate plates used to standardize and stabilize the hand during imaging are also shown. The larger cylinder supported the extended fingers. The thumb spica splint used to standardize the neutral thumb position is not visible due to its low density.

Grahic Jump Location
Fig. 4

First metacarpal (MC1) rotation (θ) as a function of azimuth angle (azi) for all 440 positions used for model fitting. Thumb rotation ranged from a low of 1.5 deg to a high of 77.0 deg across all directions of thumb motion. Peak rotations (and the highest data density) occurred at azimuth angles of −15 deg and 130 deg.

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Fig. 5

First metacarpal (MC1) screw axis elevation (ele) as a function of azimuth angle (azi). Peak elevations occurred at azimuth angles of approximately −45 deg and 130 deg, indicating coupling with external rotation and with internal rotation, respectively.

Grahic Jump Location
Fig. 6

First metacarpal (MC1) screw axis location (Qx, Qy, and Qz) as a function of azimuth angle (azi). Screw axis location varied as a second-order harmonic of azi. The locations of the fitted screw axes ranged approximately from 0 to −3 mm, 4 to −7, and 0 to −2 mm for Qx, Qy, and Qz, respectively. Qx was always dorsal biased, Qy alternated between proximal and distal, and Qz was ulnar biased. The peak proximal and distal locations of the screw axis (Qy) occurred during the primary motions of abduction, extension, adduction, and flexion. (Note the Qy axis is inverted to align with a distal orientation of the trapezium in the figures.)

Grahic Jump Location
Fig. 7

Translation (t) as a function of azimuth angle (azi). As with screw axis location, translation was fit with a second-order harmonic. However, translation also increased ∼1 mm for each 10 deg increase in MC1 rotation (θ), so separate fits were performed for each 10 deg increment of rotation, from 0 deg to 60 deg ([0–10 deg], [10–20 deg], [20–30 deg], [30–40 deg], [40–50 deg], and [50–60 deg]). For each fit, t converged to 0 mm at azi values of 180 deg, −90 deg, 0 deg, and 90 deg, suggesting that pure abduction, extension, adduction, and flexion involve no corresponding translation, while t was maximum at azi values of −135 deg and 45 deg and minimum at azi values of −45 deg and 135 deg.

Grahic Jump Location
Fig. 8

Visualization of the complete envelope of screw axes for the physiological motion of the thumb CMC joint with respect to the TCS from three orthogonal views ((a), (b), and (c)) and an oblique view (d), revealing a first-order variation in screw axis elevation as a function of azimuth angle (azi) and second-order shifts in screw axis location (Q). The set of screw axes (36 represented) is color-coded by their azimuth (azi) orientation given below the color bar, which is also labeled by the idealized directions of the screw axes for the primary motions. The spheres represent the point Q that is associated with each similarly colored screw axis. θ and t are not shown. θ is independent of both orientation and location of the screw axis, and t is dependent on θ.

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