PAIN MODEL OF SIJ OR BIOMECHANICAL?

Sakamoto
  et al. suggest that the SIJ may be a source of low back pain, as the majority
  of mechanoreceptors (97%) are Type III nociceptors, the other 3% being
  proprioceptors.[i] 
Szadek, et al performed a detailed histological study of the
intra-articular and extra-articular SIJ nociceptors.[ii] 
Murakami et al[iii]performed a remarkably enlightening
injections study effectively countering the belief that injection into the SIJ
is a “gold standard” in terms of diagnosing the SIJ alone as the pain generator.
 Murakami and colleagues performed
intra-articular injections in 25 consecutive patients. The
SIJ injection provided relief in only 9/25 (36%), whereas among the following 25
who received peri-articular (primary ligaments and soft tissues) injection, 100%
achieved pain relief.  They
concluded that when SIJD is a painful local condition, pain generation is not
from the intrinsic portion of the joint in the majority, and terms such as extra-articular or peri-articular SIJ
pain may be more cogent. 
Repeat studies are needed.



Given the
significant overlap of the relevant lumbar and sacral dermatomes, sclerotomes,
and sensory nerves encompassing L2-L3-L4-L5-S1-S2-S3, cautious interpretation is
mandated.  It should be mentioned
that current thinking is to use a cluster of tests, such that a positive SIJ
injection would require positive mechanical tests, congruent with the history
and overall presentation in order to diagnosis mechanical (as opposed to
inflammatory) SIJD.  Injection can
  reduce overall pain along the extrinsicpathways of these nerve
levels, reducing pain that is of primary lumbar segment origin. 
Therefore the term “gold standard” is overstated in being used to
diagnose the SIJ as the primary pain
generator.  It seems reasonable
ideal to also perform lumbar injection and contrast those results with the SIJ
injection.  Anatomically the lumbar
spine is connected to the sacrum via the last lumbar disc, the lumbosacral facet
joints, and proximal soft tissues. 
The lower lumbar segments are connected to the ilia via the iliolumbar
ligaments and other proximal soft tissues.  The SIJ, shares a similar connection
with the bony pelvis and hip.  This
deepens the complexity of isolating the primary pain generator in structures
that have a very similar neural pathway. 
This complexity is certainly humbling to those clinicians who accept the
clinical reality, insightfully written by Alvin Stoddard, DO:[iv] “The differential diagnosis
  between sacroiliac dysfunction and low back pain is
difficult.”



Laslett
  has described some diagnostic success with a small cluster of manual pain
  provocation tests, as they correlate well with positive SIJ
injections.[v] Cautious interpretation is warranted
because these tests do also stress the lumbar spine and the hip, and due to the
above stated limitations of the “gold-standard” diagnostic injection.  The ability to specifically isolate the
  majority of the force application to the SIJ and not the hip or lumbar spine
has yet to be thoroughly researched. 
It seems as though these studies and their impact on the profession
provide a sense of permission-granting to treat the SIJ with manual
procedures.  Yet many more clients
have faulty posture and faulty motion coupling in the lumbopelvic-hip region,
such that a biomechanical model, rather than only a pain-provocation model may
be more appropriate for this population. 
I submit that both models have relevance in differing populations. Hands-on clinicians may be frustrated
with limited ability to confidently reproduce or rule out SIJ pain.  However,
a biomechanical perspective does encourage treatment in order to enhance posture
and mobility of the pelvis, hip, SIJ, and proximal structures.  Reduction
  in pain may be facilitated by enhancing function via the restoration of optimal
  posture, movement, and muscle tone and length, etc. 
This encapsulates my philosophy regarding movement testing versus pain
provocation with manual tests.  In
support of movement testing, next we will discuss a fluoroscopy
study.








[i] Sakamoto N,
Yamashita T, Takebayashi T, et al. (2001). An Electrophysiologic Study of
  Mechanoreceptors in the Sacroiliac Joint and Adjacent Tissues. Spine,
26(20):68-71.




[ii] Szadek KM, Hoogland
PV, Zuurmond WW, et al. (2009). Nociceptive nerve fibers in the sacroiliac joint
in humans. Reg Anesth Pain Me.,
33(1):36-43.




[iii]Murakami E, Tanaka
Y, Aizwa T, et al. (2007). “Effect of periarticular and intraarticular lidocaine
injections for sacroiliac joint pain: prospective comparative study”. J
Orthoped Science,12: 274-280.




[iv]Stoddard A. (1980).
Manual of Osteopathic Technique.
London,United Kingdom: Hutchinson Publ.
1.




[v] Laslett M. (2008).
Evidence-based diagnosis and treatment of the painful sacroiliac joint.J
Man Manip Ther.