Considerations in Total Wrist Arthroplasty Design

Purpose: Total wrist arthroplasty (TWA) offers a functional alternative to arthrodesis in patients with severe wrist arthritis.^1–3 Despite improvements in implant design, loosening and failure remain a problem with the long-term success of TWAs.^1–4 The purpose of this report is to highlight some of the key considerations for designing a new TWA implant.

Materials and Methods: Current and past TWA implant designs were evaluated for range of motion, geometry, clinical outcome, and the history/ mode of failure.^1–4 Design engineers consulted with surgeons and physical therapists and conducted a meta-analysis of the literature to identify areas of patient dissatisfaction and areas for improvement. 3D-printed models in healthy and arthritic cadaver wrists were utilized to identify overall geometry, space constraints, and anchoring points. Data on range of motion, axis of rotation, and muscle moment arm were collected. Additional design considerations included surgical techniques, manufacturing, and custom installation/orientation tools.

Results: Review of current and past TWA implants demonstrates failure through dislocation (palmar and ulnar migration) and component loosening (metacarpal and radial). Carpal loosening is related to difficulty establishing stable carpal fixation. Edge loading and polyethylene (PE) wear result from torsional loads applied to condylar-shaped joints and seem to be an important factor in failure. Implant geometry also plays a crucial role in providing the needed arc of motion and establishing the axis of rotation.

Conclusions: The next generation TWA implant must incorporate a design to improve carpal fixation further. It should have new articular geometry to allow for improved range of motion. It also must provide better joint kinematics to reduce edge loading and PE wear and therefore decrease the likelihood of implant loosening.

Conflicts of Interest

None.

Keywords

arthroplasty - design considerations - wrist arthroplasty - wrist biomechanics

References

References

1 Hooke AW, Pettersson K, Sagerfors M, An KN, Rizzo M. An anatomic and kinematic analysis of a new total wrist arthroplasty design. J Wrist Surg 2015;4(2):121–127

2 Weiss A-P, Kamal RN, Shultz, P. Total wrist arthroplasty. J Am Acad Orthop Surg 2013;21(3):140–148

3 Adams, BD. Wrist arthroplasty: partial and total. Hand Clin 2013;29(1):79–89

4 Grosland NM, Rogge RD, Adams BD Influence of articular geometry on prosthetic wrist stability. Clin Orthop Relat Res 2004; (421):134–142