Wrist Arthroplasty Using 3D Printing
Ji Hye Son, MD
University Hospitals Cleveland Medical Center, Cleveland, OH
Introduction: Total wrist arthroplasty is increasing worldwide. The available implants vary greatly in concept and design. A current, widely used system has two metallic components, the radial component and the carpal component, with a spacer between these two components. The radial component has a curve that imitates the radial inclination but has a shape of an ellipsoid, which does not reflect true distal radius. The wrist is a complex structure and the current total wrist arthroplasty systems partially replicate the anatomy of the wrist.
Materials & Methods: This is a proof of concept study. Cadaver wrists underwent computed tomography (CT). The right wrist was used as a reference and various measurements were obtained - radial inclination, radial height, radial width, radial tilt, shift, as well as distal radio-ulnar joint and the relationship of the radius to the carpal bones. The measurements obtained from the right wrist was utilized to formulate the 3D model for the left total wrist prosthesis. After the 3D printout of left total wrist arthroplasty was obtained, osteotomy was performed on the cadaver left distal radius shaft, and the 3D printout model was implanted to the cadaver wrist. The model was rigidly fixated to the carpus and second and third metacarpals. Passive range of motion was measured in the cadaver wrist. Computer models were used to assess the contact stress distributions between the customized 3D model versus commercially available total wrist prosthetic.
Results: The contact stress distribution of the customized 3D model was more closely related to the right distal radius versus the model of the commercially available total wrist prosthetic. The passive range of motion obtained from the cadaver wrist after implanting the 3D model was 35 degrees dorsiflexion, 40 degrees flexion, 8 degrees radial deviation, and 15 ulnar deviation, which is comparable to commercial prosthetics.
Conclusions: The wrist is a highly complex and dynamic structure. 3D printing has the potential to provide total wrist implant that can best restore anatomic integrity.
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