Diagnostic performance of dynamic four-dimensional computed tomography (4D CT) compared to arthroscopy for analysing distal radioulnar joint instability

The wrist is a complex array of joints. It involves articulation of eight small
carpal bones, two forearm bones and five hand bones, with intricate inter- and
intra-osseous kinematics. The wrist facilitates multidirectional movement in a
synergistic manner that allow for the unique range of mobility of the hand and
forearm. Intrinsic (interosseous) and extrinsic (capsular) ligaments are the
primary passive stabilizers of the wrist. The muscles of the hand and forearm
are secondary, dynamic stabilizers.
Of all the injuries, hand and wrist injuries have the highest social and
economic impact; annual health costs and loss of labor productivity of
approximately 540 million Euros [1]. Part of the wrist injuries concerns
ligament lesions which, untreated, will progress to carpal instability and
finally osteoarthritis [2] [3] [4]. Out of the annual 25.000 wrist injuries
[5], approximately 7-10% will lead to instability [6],for which reconstruction
and salvage operations are needed, costing each ¤3.700 including physiotherapy;
a total of 9.25M¤. After surgery, patients get 3-6 months revalidation and are
unable to work, costing ¤405 per day [7]; a total of ¤55.350 per person or
138M¤ in total. If patients are diagnosed earlier, less surgeries will be
necessary, drastically decreasing the societal costs and patient discomfort.
Real-time fluoroscopy is currently the only imaging modality that can be used
to detect dynamic abnormalities in these patients [8]. However, fluoroscopy
suffers from several drawbacks: images are limited to 2-dimensions, bone
superimposition is constantly present, and the sensitivity of the examination
is highly operator dependant. This makes it impossible to reproducibly and
objectively quantify any abnormalities, if present.
Because of its high sensitivity and specificity, wrist arthroscopy is still the
gold standard for diagnosing intra-articular pathology and ligament tears of
the wrist [9]. Arthroscopy however, is an invasive and relatively expensive
procedure with a complication rate of 2%. Another drawback of arthroscopy is
the fact that the function of the ligaments can still not be dynamically
assessed for three reasons: 1) the wrist and soft tissue are distended during
the procedure to open the wrist joints for introduction of the scope and
instruments preventing movement and 2) the patient is unable to move the wrist
because of the anaesthesia and 3) movements of the wrist is not possible
because of the rigidity of the scope that has been inserted into the wrist.
A promising imaging method that could contribute to this field is 4DCT
scanning. Using recently developed, continuous acquisition of 3D CT images
during movement, it may be capable of assessing patients with suspected
instability with higher diagnostic performance by facilitating kinematic
assessment of wrist motions. In a previous study we have focused on 4DCT
imaging of the scapholunate joint (ABR number NL72518.091.19) during
radio-ulnar deviation and flexion and extension of the wrist, which has shown
to provide adequate dynamic images of the wrist and a quantitative analysis of
the scapholunate joint.. The wrist consists of an array of complex wrist joints
and ligaments stabilizing these joints. With a mechanism similar to the
scapholunate joint these joints can also become unstable causing progressive
pain and damage to the structures in the wrist. In these cases arthroscopy is
also often used causing the range of difficulties mentioned above. Because of
these promising first results with the scapholunate joint, we expect a
diagnostic application of 4DCT also for the other types of wrist instability.
Due to the rotating gantry movement different movements may cause different
motion artifacts. Therefore, 4DCT imaging of other wrist joints during
clinically relevant wrist motions are required. This means that we want to
focus on the distal radio-ulnar joint (DRUJ); the carpometacarpal-1 (CMC-1)
joint and the metacarpal phalangeal-1 (MPC-1) joint during pronation-supination
of the wrist and abduction-adduction and opposition-reposition of the thumb.
This will make it possible to set-up a method for fully automatic instability
diagnosis in the wrist based on 4DCT.
The superior 3-dimensional spatial resolution of 4DCT compared to fluoroscopy
allows this technique to accurately detect even slight positional changes of
the bones, in contrast to 2D fluoroscopy [10]. While conventional static 3D
imaging methods can provide valuable information about carpal bone anatomy and
alignment, dynamic imaging has the advantage of assessing the carpus, distal
radius and ulna, and joint spaces throughout the range of movements and
capturing their complex interplay. This will provide a way to better
understanding of normal wrist kinematics and improve diagnosis of subtle
instabilities and decrease the need for arthroscopy. Moreover, if surgical
intervention is deemed appropriate, the source of the instability might be more
precisely identified. Detailed knowledge of the nature of instability will
allow clinicians to offer more specific and appropriate surgery for each
patient. Following from this, the effect of surgical interventions on wrist
kinematics can be more thoroughly investigated, helping to guide and shape
further clinical treatment.
An important drawback of 4DCT scan is the radiation exposure, like in
fluoroscopy. However, in a previous study focused on the scapholunate ligament
(ABR number NL72518.091.19) we have shown that high-quality 4DCT images of the
moving wrist can be acquired with a mean effective radiation dose of mSv ,
which compares favourably with a normal background radiation for any individual
(2 mSv per year) 22,23. Furthermore, research in the orthopaedic research lab
of the Radboudumc has demonstrated the feasibility of 4DCT for use in imaging
the knee joint during flexion and extension movements. Using the findings of
these previous studies we have established a useful and robust workflow for
processing even low-dose, noisy imaging data. In accordance with this protocol,
we want to investigate the feasibility of the 4DCT for the moving wrist joint
to visualize the articulation of the bones of the wrist.
The distal radioulnar joint (DRUJ) is an inherently unstable joint located
between the radius and ulna stabilized by the radioulnar ligament which is part
of the triangular fibrocartilage complex (TFCC) [11]. TFCC injuries, causing
DRUJ instability, may occur after distal radial fractures in up to 43% of cases
or due to chronic degenerative injury after abnormal loading due to ulnar
impaction syndrome [12] [13]. If left untreated TFCC injuries can lead to
progressive pain worsening, functional compromise and ultimately secondary
osteoarthritis [14]. Surgical treatment of the TFCC injury is indicated with
instability of the DRUJ or unstable and displaced fractures [15].
Due to the progressive nature of the injury patients with an early diagnosis of
a TFCC injury may benefit from less-invasive treatment options, have a better
prognosis, and experience less residual disability [15]. However, current
imaging of the TFCC remains difficult, dynamic instabilities demonstrate
abnormalities only during motion. Computed tomographic arthrography and
magnetic resonance arthrography are currently the two most viable imaging
techniques, but the sensitivity and specificity of these static imaging
techniques are relatively low compared to arthroscopy, with a sensitivity of
respectively 0.89 and 0.78 and a specificity of respectively 0.89 and 0.85
[16]. Normal MRI is also used but has a sensitivity of 0.76 and a specificity
of 0.82.
Due to the novelty, only a few studies have been published on wrist kinematics
using 4DCT scans. These studies have demonstrated its potential for the
evaluation of DRUJ instability, particularly in cases of inconclusive initial
clinical

The study will consist of 3 parts. First we want to perform a reference study
with healthy volunteers to investigate the viability of 4DCT scanning of the
wrist for evaluating wrist bones configurations and movements (translations and
rotations) during a new set of wrist motions that have not been evaluated in
our previous study focused on the scapholunate ligament (NL72518.091.19). We
want to evaluate the visibility of the DRUJ, the carpal metacarpal 1 (CMC-1)
joint and the metacarpal phalangeal 1 (MCP-1) joint during clinically relevant
wrist movements. Besides, in this study we want to evaluate differences
between the left right wrist within participants during wrist motion. In future
clinical practice the uninjured wrist may be used as a reference for the
injured wrist, determining the left right difference in healthy volunteers will
show the robustness of this technique.
Subsequently, we will perform a diagnostic clinical study on patients with
chronic wrist pain, suspect for DRUJ instability. The objective of the clinical
study is to determine the sensitivity and specificity of the 4DCT scan (during
a series of movements in which DRUJ instability is predicted to be best
visible) in the diagnosis of DRUJ instability in comparison with arthroscopic
findings (gold standard). If the 4DCT shows to have a sensitivity and
specificity comparable to that of wrist arthroscopy, it is the aim to introduce
4DCT as first choice imaging modality for diagnosing wrists suspected for DRUJ
instability. Lastly, on 20 patients, we want to perform a reliability study to
investigate the intra-patient test-retest reliability of our 4DCT scanning
protocol.

Single institution, a explorative reference study with volunteers followed by a
diagnostic clinical study in the Radboud University Medical Center.
We will include 30 healthy participants with no medical history of wrist
trauma, surgery or wrist complaints and in age range of 20-50 and; and 30
patients with chronic unilateral wrist pain suspect for DRUJ instability.

For the reference study all 30 healthy participants first undergo a bilateral
3D CT scan in neutral wrist position for usage of reference. The field of view
of this scan includes all carpal bones and the two forearm bones. The scan
technique is a Toshiba delivered application and CE certified. Subsequently,
the forearms are placed in a supporting frame which minimizes lower-arm motion
during 4DCT image acquisition. Prior to image acquisition, participants will
undergo a training session on how to move their wrist according to the imaging
protocol. A bilateral dynamic 4DCT scan is made while actively moving the
wrists according to a protocoled cycle of movements. To reduce radiation
exposure, the z-axis coverage is reduced to 12 cm in the 4DCT scan . Videos of
the wrist movements are shown to the participant during image acquisition,
which will help the participants to perform the movements at a constant pace.
This will provide images with highest quality and will provide the source data
considering carpal bone movements and function of ligaments during active wrist
motions.


For this DRUJ instability study, a static 3D CT scan and a dynamic 4DCT scan of
the both wrists of the patient suspect for DRUJ instability will be done after
the X ray which is performed during standard clinical practice. The protocol is
the same as described above in the reference study but the patients follow the
DRUJ movement protocol with movements that are clinically relevant for DRUJ
instability diagnosis.
For the reliability study 20 of the patients included in the DRUJ instability
study will additively undergo an extra bilateral 4DCT scan one minute after the
first 4DCT scan. To determine the reprocibility of the wrist movements best,
the protocol is exactly the same as the 4DCT protocol as described above.

The following radiographic signs will be evaluated: radioulnar angle; sigmoid
notch to ulnar head joint distance; radioulnar ratio; radioulnar line distance;
subluxation ratio; epicentre distance; radioulnar joint volume; scaphoid and
lunate angle; ulnar variance and ulnar head to carpal bones joint distance [24]
[25] [26] [29] [30].

Setting: Collaboration between Radiology department, Plastic Surgery department
and Orthopedic research lab of the Radboud University Medical Center.
Expected duration: 6 months.

Of the healthy volunteers, 30 will undergo one bilateral static 3DCT scan and
one bilateral 4DCT scan,

In the clinical trial, 30 patients with DRUJ instability will undergo a simple
bilateral wrist radiography, a static bilateral CT scan, a bilateral 4D CT scan
and a unilateral arthroscopy of the DRUJ instability symptomatic wrist.

In addition, 20 of these 30 patients undergo a bilateral static 3DCT scan, a
bilateral 4DCT scan, and a bilateral 4DCT scan one minute after the first CT
scan. We want to investigate the test-retest reliability of the protocol.
Therefore, it is important that the exact same dynamic scan be done again. The
4DCT involves an effective dose of 0.02mSv per scan, this is in addition to the
standard static 3DCT scan. In total, the dose for this group is 0.06mSv. This
burden is a manageable risk compared to the natural background radiation in the
Netherlands (2 mSv). Therefore, it is important to note that the additional
radiation exposure is minimal, so the risk of adverse radiation-related health
effects is minimal. Moreover, both plain radiographs and arthroscopy are part
of the normal diagnostic follow-up of patients in whom DRUJ is suspected, so
there is no additional burden or risk involved.