4D-CT examination to evaluate range of motion obstructions and underlying causes in scheker implants

Evaluation of distal radioulnar prosthesis performance is not very common and
does not seem necessary since studies report that prosthesis longevity and
patient satisfaction are high (>90%)1,2 . However, the complication rate is
approximately 25% This raises the question whether patient satisfaction and
prosthesis longevity are valid indicators of prosthesis performance.

A better way to evaluate the performance on an implant is by a
quantitative comparison to the healthy contralateral joint, which can be
considered to be the gold standard. Range of motion, motion pattern and the
position of the rotational axis of the forearm are some parameters that
describe the function of the wrist quantitatively.

With the emergence of four dimensional computed tomography (4D-CT)
technology quantitative evaluation of DRUJ motion has become feasible.
Combining regular- and 4D-CT in the follow up of patients who have undergone
DRUJ arthroplasty would objectify prosthesis performance. Moreover, a
quantitative kinematic assessment may reveal limitations in the use or design
of current DRUJ prostheses and could improve future use of DRUJ prostheses.

Primary objective: To use 4D-CT to find possible relations between functional
deficiencies of patients with an Aptis Scheker prosthesis and important
prosthesis characteristics like implant placement and implant design.

Secondary objective: To provide a 4D-CT based method for quantifying DRUJ
implant performance. This method will be based on a comparison of kinematic
parameters of the arthroplastic- and the healthy contralateral DRUJ.

This study is a cross sectional study. Both forearms will be subjected to one
3D-CT scan and three 4D-CT scans. The 4D-CT scans will be performed during
forearm rotation (pronation to supination) and wrist movement (extension to
flexion). Further performance characteristics will be analysed by performing a
grip strength measurement, a goniometric measurement and by filling out a short
questionnaire. We will include patients from the Academic Medical Center,
Amsterdam. Processing of the 4D data will also be conducted at the Academic
Medical Center, Amsterdam.

The radiation exposure the patient will receive falls within category IIa of
the International Commission on Radiological Protection (ICRP), which qualifies
as: minor.

While radiation exposure does not allow unlimitedly forearm imaging, due to the
absence of organs in limbs, radiation risks are extremely low. As motion is
guided
voluntary, there is no risk of harm either. Findings from 4D-CT scans will be
used
for a better decision making for future patients with regard to implant
placement and sizing as well as improving the design of new DRUJ implants.