Carpal kinematics during forearm rotation using three-dimensional CT-imaging

Ulnocarpal abutment syndrome is a severe disorder of the wrist accompanied by
pain and damage to the carpal bones. The generally accepted idea is that
movement of the wrist and rotation of the forearm causes a lengthening of the
ulna relative to the radius, resulting in pushing of the ulna against the TFC
and the ulnar bones of the wrist, especially when the wrist is under axial
loading. Ultimately, this pushing leads to overload, degeneration of the ulnar
bones of the wrist and pain. Previous studies found an association between
lengthening of the ulna during axial loading in pronation and the ulnocarpal
abutment syndrome, when comparing posteroantertior radiographs to clinical
symptoms. However, such radiographs only allow for a two-dimensional view that
may give a distorted view of the true movements in the forearm and wrist. We
previously developed a method for three-dimensional CT-scanning that allows for
analysis of forearm and wrist movement. Using this technique, we now want to
study whether the ulna lengthens relative to the radius during pronation and
supination, and during axial loading.

To investigate changes in ulnar length after maximal forearm rotation and axial
loading.

Every participant will be subjected to 4 CT-scans obtained in different
positions. The wrist is immobilized. The initial scan is performed with the
forearm in neutral position, followed by two scans with the forearm in extreme
supination and pronation. The last scan is repeated under axial loading.

All four scans are made with an intermediate resolution; relevant settings are
shown in the table *CT-scan setting*. The radiation doses in computed
tomography are estimated to be 0.2 mSV per scan and are considered minor by the
world health organization (WHO). Subjects receive a total radiation dose of 0.8
mSv.