An approach for direct visualization of continuous three-dimensional elbow kinematics using reconstructed surfaces has
been developed. Simulation of valgus motion was achieved in five cadaveric specimens using an upper arm simulator.
Direct visualization of the motion of the ulna and humerus at the ulnohumeral joint was obtained using a contact based
registration technique. Employing fiducial markers, the rendered humerus and ulna were positioned according to the
simulated motion. The specific aim of this study was to investigate the effect of radial head arthroplasty on restoring
elbow joint stability after radial head excision. The position of the ulna and humerus was visualized for the intact elbow
and following radial head excision and replacement. Visualization of the registered humerus/ulna indicated an increase
in valgus angulation of the ulna with respect to the humerus after radial head excision. This increase in valgus angulation
was restored to that of an elbow with a native radial head following radial head arthroplasty. These findings were
consistent with previous studies investigating elbow joint stability following radial head excision and arthroplasty. The
current technique was able to visualize a change in ulnar position in a single DoF. Using this approach, the coupled
motion of ulna undergoing motion in all 6 degrees-of-freedom can also be visualized.
Incorrect selection of the native flexion-extension axis during implant alignment in elbow replacement surgery is likely a
significant contributor to failure of the prosthesis. Computer and image-assisted surgery is emerging as a useful surgical
tool in terms of improving the accuracy of orthopaedic procedures. This study evaluated the accuracy of implant
alignment using an image-based navigation technique compared against a conventional non-navigated approach.
Implant alignment error was 0.8 ± 0.3 mm in translation and 1.1 ± 0.4° in rotation for the navigated alignment, compared
with 3.1 ± 1.3 mm and 5.0 ± 3.8° for the non-navigated alignment. Five (5) of the 11 non-navigated alignments were
malaligned greater than 5° while none of the navigated alignments were placed with an error of greater than 2.0°. It is
likely that improved implant positioning will lead to reduced implant loading and wear, resulting in fewer implantrelated
complications and revision surgeries.