surfaces 378 380 and facilitate insertion of device 310 into a desired area within a patient upper and lower surfaces 374 376 include serrations 382 e g grooves teeth projections etc that may extend along all or a portion of the length of third link 316 between first end 370 and second end 372 inner surface 378 may be curved such that when device 310 is expanded links 312 314 316 form a generally oval shaped interior first end 370 of third link 316 includes a slot 392 e g an elongated aperture recess etc that is configured to receive pivot pin 318 and enable pivot pin 318 to pivot and translate within slot 392 as such first link 312 is able to move in both a pivoting and translating manner an end wall 396 limits the pivoting and translational movement of first link 312 relative to third link 316 as device 310 is moved between a radially collapsed position and a radially expanded position first end 370 further includes a channel groove or recess 394 that is configured to receive projection 338 e g lobe knuckle hinge portion or member etc on first link 312 as shown in fig2 pivot pin 318 is received within slot 392 in third link 316 and aperture 340.