119 patients with clinically diagnosed trapeziometacarpal (TMC) joint arthrosis (62 of which completed the study) were randomized to wear either a customized 3.2 mm-thick thermoplast hand-based thumb spica splint, or a pre-fabricated neoprene splint to determine if superiority exists between the two types. Results indicated that, although both splint types improved pain, grip strength and pinch strength, they did not improve DASH scores at a mean follow-up of 9 +/- 9 weeks. In addition, one splint type was not superior over the other in terms of physical function.