Short arm splints for wrist stabilization: A mechanical material test and cadaveric radiography study

Abstract

Purpose: Documentation of the wrist stabilizing effect and mechanical properties of common splinting materials is warranted to support evidence-based condition-specific recommendations for wrist immobilization. The objectives of this study were to assess the wrist stabilizing properties of volar and dorsal short-arm splints made of four different materials and evaluate the mechanical properties of the splinting materials. Methods: Dorsal and volar short arm splints made of plaster of Paris (PoP) (eight layers), Woodcast (2 mm, rigid vented), X-lite (classic, two layers) or a 3D-printed material (polypropylene) were sequentially mounted on 10 cadaveric arm specimens and fixed in a radiolucent fixture. This enabled the evaluation of maximum wrist flexion and extension relative under an orthogonal load of 42 N via radiographic images. In addition, a three-point bending test was performed on ten sheet duplicates of each of the four splinting materials. Results: When applied as a volar splint, PoP had the highest capability to resist wrist flexion and extension. However, when applied as a dorsal splint, Woodcast exhibited a lower wrist flexion and a similar wrist extension. The 3D-printed splints—both volar and dorsal—showed the highest mean wrist flexion and extension. The mechanical properties of the Woodcast, X-lite and 3D-printed splinting materials were very similar. PoP exhibited distinct properties with a stiffness of 146 (95% confidence interval [CI]: 120–173) N/mm and a deflection at Fmax of 0.6 (95% CI: 0.5–0.7) mm compared to ≤7.7 (95% CI: 7.4–7.9) N/mm and ≥20 (95% CI: 18–22) mm for the other materials. Conclusion: PoP displayed better wrist stabilizing properties and material stiffness than Woodcast, X-lite and 3D-printed polypropylene. When considering wrist stabilizing properties, PoP may still prove to be the preferred choice for wrist immobilization. Level of Evidence: Not applicable.