Proximal-distal shift of the center of rotation in a total wrist arthroplasty is more than twice of the healthy wrist - PubMed (original) (raw)

. 2020 Jul;38(7):1575-1586.

doi: 10.1002/jor.24717. Epub 2020 May 25.

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Proximal-distal shift of the center of rotation in a total wrist arthroplasty is more than twice of the healthy wrist

Bardiya Akhbari et al. J Orthop Res. 2020 Jul.

Abstract

Reproduction of healthy wrist biomechanics should minimize the abnormal joint forces that could potentially result in the failure of a total wrist arthroplasty (TWA). To date, the in vivo kinematics of TWA have not been measured and it is unknown if TWA preserves healthy wrist kinematics. Therefore, the purpose of this in vivo study was to determine the center of rotation (COR) for a current TWA design and to compare its location to the healthy wrist. The wrist COR for six patients with TWA and 10 healthy subjects were calculated using biplane videoradiography as the subjects performed various range-of-motion and functional tasks that included coupled wrist motions. An open-source registration software, Autoscoper, was used for model-based tracking and kinematics analysis. It was demonstrated that the COR was located near the centers of curvatures of the carpal component for the anatomical motions of flexion-extension and radial-ulnar deviation. When compared to healthy wrists, the COR of TWAs was located more distal in both pure radial deviation (P < .0001) and pure ulnar deviation (P = .07), while there was no difference in its location in pure flexion or extension (P = .99). Across all coupled motions, the TWA's COR shifted more than two times that of the healthy wrists in the proximal-distal direction (17.1 vs 7.2 mm). We postulate that the mismatch in the COR location and behavior may be associated with increased loading of the TWA components, leading to an increase in the risk of component and/or interface failure.

Keywords: center of rotation; kinematics; replaced wrist; total wrist arthroplasty; wrist.

© 2020 Orthopaedic Research Society. Published by Wiley Periodicals LLC.

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Conflict of interest statement

CONFLICT OF INTEREST

The institutions of JJC and SWW possess intellectual property on a total wrist implant design that was not examined in this study. APCW has a financial interest in a total wrist arthroplasty design that was not examined in this study.

Figures

Figure 1.

Figure 1.

Three-dimensional models of a healthy wrist (radius, capitate, and third metacarpal), and a replaced wrist (resected radius, radial component, polyethylene cap, carpal component, resected capitate, and third metacarpal) in the neutral pose. For the sake of clarity, other carpal bones are omitted.

Figure 2.

Figure 2.

The tracked third metacarpal and radius for the healthy wrist (left) and carpal component and radial component for the replaced wrist (right) for one of the radiographic views. The image features of radiographs are enhanced using Sobel edge filter and intensity thresholding to maximize the similarity between the bones/implants and radiographs.

Figure 3.

Figure 3.

Depiction of bones’ and implants’ coordinate systems. X-axis (red), y-axis (green), and z-axis (blue) demonstrate the axes.

Figure 4.

Figure 4.

The screw axis was transferred to the origin of the radius coordinate system and based on its orientation and projection the azimuth (azi) and elevation angles were calculated. X-axis (red), y-axis (green), and z-axis (blue) demonstrate the radius coordinate system.

Figure 5.

Figure 5.

Center of minor and major curvatures of the ellipsoidal shape of the polyethylene cap. Curvatures were detected using the least-squares fitting of an ellipsoid to the surface points of the polyethylene cap.

Figure 6.

Figure 6.

The projected center of rotation (COR) was defined for the healthy wrists as a point on the mid-axis of the capitate which had the shortest distance from the axis of rotation (red). The polyethylene cap’s mid-axis was used to define the projected COR for the replaced wrists (TWA).

Figure 7.

Figure 7.

Center of rotation (COR) on the resected capitate for the replaced wrist (top panel) and capitate (bottom panel) for the healthy wrist. The replaced wrist had a COR located slightly distal to the center of curvature in flexion-extension (top left panel; radial view), while it was slightly proximal to the center of curvature in radial-ulnar deviation (top right panel; volar view). Centers of curvatures are shown as black dots, and the standard deviation of COR in both directions are shown as colored ellipses.

Figure 8.

Figure 8.

The proximal-distal shift of the projected center of rotation (COR) as a function of wrist motion (for all tasks). COR shifted in a sinusoidal pattern (solid black line with confidence interval as a shaded region) in proximal (+) and distal (−) direction from the most distal point on capitate (i.e., 0 on the figures) for both cohorts. The healthy wrist’s COR traveled an approximately 7.2 mm while the replaced wrist’s COR traveled about 17.1 mm.

Figure 9.

Figure 9.

The axis of rotation’s elevation angle of healthy wrist followed a sinusoidal pattern, while the replaced wrist had mostly a negative elevation angle throughout. The average (solid black line) and standard deviations (shaded black region) were calculated at 4 anatomical and 4 coupled wrist motions.

Figure 10.

Figure 10.

The shortest distance from the screw axis to the x-axis of capitate (l). This distance for the replaced wrist was approximately 0 throughout the wrist motion, while the healthy wrist had slightly larger variations. The average (solid black line) and standard deviations (shaded black region) were calculated at 4 anatomical and 4 coupled wrist motions.

Figure 11.

Figure 11.

The overall pattern of screw axis orientation and location at four anatomical (F: flexion, E: extension, R: radial deviation, U: ulnar deviation) and four coupled wrist motions (UF: ulnar-flexion, UE: ulnar-extension, RE: radial-extension, RF: radial-flexion) for Freedom® replaced wrist (top panel) and a typical healthy wrist (bottom panel) in radial view (left panel) and volar view (right panel). In both healthy and replaced wrists, rotation axes for pure flexion-extension and radial-ulnar deviation were orthogonal and consistent with the motion. In healthy wrists, dart-thrower’s (RE to UF) and anti dart-thrower’s (RF to UE) followed the same pattern, while in the replaced wrist the coupled motions had dissimilar and complex patterns.

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