Fig. 3
Two circles located on the dorsal side of the proximal interphalangeal joint (PIPJ) implant head. Notations are as follows: ppe and pme, the centers of the circles in the proximal phalangeal component (PPC) and middle phalangeal component (MPC) heads, respectively; rpe and rme, the radii of the dorsal circles in the PPC and MPC heads, respectively; L, the distance between ppe and pme; Lx and Ly lengths of L projected to the x and y axes, respectively; ϕe, the angle in the clockwise direction between the x axis and the line tangent to the two circles (red solid line); and θ, degrees of PIPJ flexion