Four-Dimensional Computed Tomography-Derived Radiolunate Arthrokinematics With a Case Study in Four-Corner Arthrodesis.

Background: The radiolunate joint is conventionally thought to be spared from radiocarpal osteoarthritis, but proximal lunate degenerative changes have been noted. An investigation of radiolunate arthrokinematics in ostensibly healthy wrists may improve understanding of posttraumatic and postoperative outcomes. We hypothesize that four-dimensional computed tomography (4DCT)-derived radiolunate arthrokinematics during motion will differ between wrists with type 1 and type 2 lunates. The clinical-translational relevance of this analysis is highlighted using a 4DCT case study of scaphoid excision with 4-corner arthrodesis (SEFCA).

Methods: Four-dimensional computed tomography data were collected during flexion-extension and radioulnar deviation in 19 healthy wrists (mean [SD] age: 43.6 [11.7] years, 21.1% female) and 1 wrist 3 years after SEFCA (male, 52 years). Carpal osteokinematics and joint arthrokinematics were calculated to derive median radiolunate interosseous proximities at each 4DCT-captured timepoint.

Results: Median radiolunate interosseous proximities during motion are well approximated by second-order regressions in uninjured wrists. In the arthrodesed wrist, closest proximities occurred at the extremes of motion except maximum radial deviation.

Conclusions: This study quantifies a normative range of median radiolunate interosseous proximities during wrist motion. The normative 4DCT datasets provide a reference range for evaluating postoperative arthrokinematics, suggesting the clinical-translational potential of dynamic imaging. The case study highlights applications for patient-level postoperative evaluation, which can be expanded to other pathologies, surgeries, or conditions in the future.