Discussion
The study findings suggest that remote measurement systems are valid and
cost-effective options to estimate functional movement and posture in
people with axSpA. Specifically, the validity results suggest there is
moderate to strong correlation and agreement between a majority of
functional movements and postural alignment compared to a standard
clinician assessment. The strongest correlational relationships were
shown in lumbar forward flexion, lumbar side flexion, shoulder flexion,
hip internal rotation, tragus-to-wall, and thoracic kyphosis,
particularly in people with axSpA. The only test from either a
functional movement or posture that showed no correlation between
methods was found in the lumbar lordosis, which was consistent between
the axSpA and non-back pain groups.
The two groups demonstrated expected clinical presentation differences,
including higher BASDI and BASFI scores and more restricted range of
motion and hyperkyphosis in the axSpA group. The limited range of motion
among the axSpA group in all functional movements tested demonstrates
the broader use of this technology in clinical groups that fall outside
the normal range of motion. In the end, the results did indicate varied
correlative relationships between the axSpA and non-back paing groups in
several functional movement and postural tests, notably shoulder
flexion, lumbar side flexion, tragus-to-wall and kyphosis. In both
shoulder flexion and lumbar side flexion, the axSpA group had smaller
ranges of motion compared to the non-back pain group and stronger
correlation (r = .787-.906) between the CV-aided system and clinical
measurement compared to the non-back pain group (r = .468-.655). One
reason for this discrepancy could be due to altered anatomical landmark
visibility or increased trunk compensation in higher ranges of motion as
were seen in the non-back pain group. Posture measurement demonstrated
similar incongruence; there was a stronger correlation in the axSpA
group, who presented with more kyphotic and forward flexed posture
compared to the non-back pain group. This discrepancy could stem from
less accurate and reliable measurement of smaller kyphosis curvature,
which is one limitation of the tragus-to-wall test which has a floor
effect.
The tests that did not demonstrate strong correlation were hip
abduction, cervical rotation and lumbar lordosis posture. Hip abduction
was adapted into a standing test to provide a more practical testing
position for video recording compared to the BASMI hip mobility test,
where the patient is lying on the ground and abducting both hips to
their maximum range. Although more practical to perform, standing hip
abduction has challenges that include both the participant performing it
correctly and the landmarks needed for automation. Participants often
compensate during standing hip abduction by either elevating their
ipsilateral hip or externally rotating their hip. If the clinician does
not correct the compensatory movements, it could cause an overestimation
of the range. Similarly, the compensatory movements can cause an
overestimation or inaccurate landmark identification by the CV
algorithm. Cervical rotation in a seated position with a tape measure
was also chosen for its practicality. This test was taken from the
EDASMI since the supine cervical rotation test in the BASMI similar
camera positioning challenges as the hip mobility test. The difficulty
with frontal plane measurement of a rotational movement was demonstrated
in the lack of a strong correlation between the CV-aided system and
clinician measurement, in both groups. Lastly, the lumbar lordosis
postural alignment measured by surface topography using the Kinect
sensor showed agreement, but no correlation and no significant
difference between groups. This could be on account of the documented
difficulty of measuring lumbar lordosis with surface measurement tools,
and the practicality of clothing interference in some participants
during the testing.
An important aspect of this study was the feasibility of the CV system
in a home setting because of the potential for many benefits of remote
testing. The first barrier for the participants was uploading the
videos, which was less successful in the axSpA group (n=8 missing) than
the non-back pain group (n=1 missing). Developing a user-friendly
interface for uploading videos would lower the barrier for home use. Two
other aspects of feasibility at home were the ability of participants to
successfully record the correct movement and the quality of the videos
for automated CV analysis. More than 70% of the recorded videos were
useable. The reasons for non-usable data were incorrect use of the
calibration grid, camera movement and incompatible data format from one
participant’s smartphone. These issues could be addressed by improving
instructions and calibration method. Pragmatic use of this technology at
home would be a key to helping people, with and without back pain, track
and maintain functional movement, range of motion and posture with the
option of remote clinician support. Not only does this remote system
widen accessibility to specialists who may not be local, it is a
cost-efficient method and has many social and environmental benefits. It
can benefit both patients and the health system in terms of time and
opportunity. Furthermore, it can have a positive environmental impact by
reducing the carbon footprint associated with each face-to-face visit.
For the appropriate patient, it could result in a cost savings of £64
per assessment. While these results look specifically at people with
axSpA, it can reasonably be generalised to similar long-term
musculoskeletal conditions.
Limitations
The limitations of this study include the relatively small sample size
and the cross-sectional method. While it was not possible for
simultaneous measurement from the clinician and video, the repetitions
were performed within the same session under the same conditions.
Further studies would benefit from repeated testing to measure the
sensitivity to change of these remote technologies.
Conclusions
Using a clinically-validated computer vision system in rehabilitation
has the potential to reduce inequality in the health system and make it
more cost and time effective for both patients and the health system. In
addition to demonstrating validity in most of the functional and
postural measures, results show that using this CV-aided system in a
home environment is a safe and feasible method which can widen
accessibility and affordability.