Evaluating the test-retest reliability of a standardized flexion - extension radiograph imaging protocol for the lumbar spine.

Lumbar spinal stenosis is a relatively common medical problem, but optimal
treatment for the condition is poorly understood. Lumbar spinal stenosis is
commonly treated with decompression surgery with or without additional fusion
surgery. Orthopaedic surgeons are currently faced with the dilemma of whether
or not to add fusion to a decompression procedure. To decide between these two
surgical options, surgeons rely mostly on their experience to conclude if a
level is unstable preoperatively or if a specific decompression procedure is
likely to destabilize the spine. A valid and reliable test for spinal
instability would facilitate research to determine whether spinal instability
measurements can be used choose the optimal surgical treatment for each level.

The main objective of this study is to evaluate the test-retest reliability of
a standardized flexion - extension radiograph imaging protocol for the lumbar
spine. To achieve this, a validated motion analysis technology will be used to
quantify differences (if any) in kinematic profiles for a patient performing
lumbar flexion-extension radiograph according to a standardized imaging
protocol and repeating the same procedure one hour later.

This is an observational, exploratory study conducted in Rijnstate Hospital
(Arnhem) and Onze Lieve Vrouwe Gasthuis (Amsterdam) during which participants
will undergo one set of flexion-extension radiographs (i.e. two radiographs)
and another set of flexion-extension radiographs (i.e two more radiographs) one
hour later.

Benefits
Participating in this study has no direct benefits for the participants.

Risks
Participants who participate in this study will be exposed to an additional 0.6
mSv of radiation compared to their regular care.

In OLVG and Rijnstate, the effective median exposure dose of a standard lumbar
radiograph is 0.2 mSv. During regular care, a patient will typically undergo
one anteroposterior and one lateral radiograph, resulting in a total radiation
dose of (2 x 0.2 =) 0.4 mSv. The effective dose for a typical flexion-extension
radiograph (which is the same as two regular radiographs) of the lumbar spine
is also 0.4 mSv. During this study, the participants will undergo one
anteroposterior radiograph while their (regular) lateral radiograph will be
replaced by a flexion-extension radiograph. After one hour, each participant
will undergo another flexion-extension radiograph, resulting in a total study
radation dose of (5 x 0.2 =) 1 mSv. This is 0.6 mSv over the radiation exposure
during regular care.

Based on a large clinical investigation on the risk to develop cancer
associated with exposure to radiation, it was estimated that the excess
relative risk for cancer development is 0.97 per Sv [14] . The excess relative
risk of the radiation that each subject would receive from participation in
this study is therefore calculated as 0.97/Sv x 0.6 mSv x 1 Sv/1000 mSv =
0.000582. To place this relative risk into perspective: there are many sources
of exposure to radiation in daily living and the public is exposed to
approximately 3 mSv/year from ubiquitous radiation. Also, most patients
eligible for inclusion in this study will be over the age of 45. In this latter
age group the lifetime risk of radiation induced carcinogenesis is known to
decline rapidly.

Considering the above, and applying the risk classification as proposed by the
Dutch Federation of University Medical Centers (NFU) the additional radiation
risk is negligible (*verwaarloosbaar risico*) because there is only a small
risk of minimal damage (*kleine kans op lichte schade*). We believe that the
benefits of gaining knowledge about the validity and test-retest reliability of
the SPSITM outweighs this negligible risk.