Pelvic alignment
Today we are going to look into the evidence behind Pelvic alignment. We will attempt to examine the alignments themselves, how we measure them, how accurate the measurements are and more importantly attempt to answer the question, do they affect injury and pain?
Below are the main two Pelvic alignment positions, which are influenced by many factors:
Anterior Superior (AS) Ilium:
When the PSIS (posterior superior Iliac spine) moves up and forwards
It is believed that an anatomical short leg predicts anterior rotation (AS Ilium) of the ipsilateral Ilium (Cooperstein 2010).
Posterior Inferior (PI) Ilium:
When the PSIS (posterior superior Iliac spine) moves down and backwards
It is believed that an anatomical long leg predicts posterior rotation (PI Ilium) of the ipsilateral Ilium (Cooperstein 2010).
So what Pelvic alignments shall we examine that influence an
AS or a PI ilium?
ASIS and PSIS angle of tilt:
What are the normal ranges?
8 to 10 degrees positive or anterior tilt (Bradeley 2015)
0 to 23 degrees (Preece et al 2008)
How to measure the angle and how reliable is the measurement?
Pelvic inclinometers have been found to be reliable and easy
to use (Crowell et al 1994).
How valid are the measurements?
Research for:
Evidence isn’t available to support whether the measurements
of PSIS and ASIS tilt accurately depict the Innominate position.
Research against:
The ASIS and PSIS angle was found to vary from left to right
by up to 11 degrees with a neutral Pelvic position (Preece et al 2008). This essentially means that the size and shape of the bones is different from right to left making the bony landmarks potentially mislead us on the actual joint positions. Like any orthopaedic test, this measurement should only form part of an overall assessment in determining abnormal alignment and function.
Do the measurements tell us anything about injury?
Yes:
ACL ruptures were found to have increased anterior Pelvic
tilt compared to uninjured limbs (Hertel et al 2004). However what this doesn't tell us is this a cause or an effect?
Consideration should be given to the Lumbar spine, Pelvic
alignment & postural control when managing Hamstring injuries (Mason et al
2008). Obviously any change in pelvic ASIS to PSIS tilt will change the position of the Ischium attachment of the Hamstrings and could great more or less load through this area.
Dynamic anterior Pelvic tilt (ASIS and PSIS tilt) was predicted to result in an earlier occurrence of Femoroacetabular impingement in the hip joint and dynamic posterior Pelvic
tilt (ASIS and PSIS tilt) results in later occurrence of Femoroacetabular impingement (Ross et al
2014). This could be vital information in managing hip impingement conservatively as opposed to surgically.
No:
Nourbakhsh & Arab (2002) found no correlation between
lower back pain and the ASIS and PSIS angle of tilt.
So overall ASIS and PSIS tilt is very likely to be important
but it is difficult to measure accurately due to bone asymmetry. This being
said along with other measurements it may prove to be accurate, quick, easy and therefore a
useful measure for multiple spinal and lower limb musculoskeletal conditions.
Pelvic Incidence:
This is the angle between the line perpendicular to the Sacral base at its midpoint and the line connecting this point to the Femoral
heads axis
Normal ranges:
33° to 85°(Vaz et al 2001)
34° to 78° (Boulay et al 2006)
How to measure the angle and how reliable is the measurement?
The only real way to measure this angle is with a radiograph (X-ray), which is reliable but not easily performed in clinical practice.
How valid are the measurements?
Research for:
The measurement can be used to determine the orientation of each Acetabulum and so can be useful for hip joint issues (Boulay et al 2014).
Research against:
There is no research against the validity of the measurement.
Do the measurements tell us anything about injury?
Yes:
Chaléat-Valayer et al (2011) found that people with chronic
lower back pain had a smaller Pelvic incidence. Again is this a cause or an effect. We know that the posterior hip muscles can often go into spasm with back pain and this may account for why the Pelvic incidence becomes smaller due to the shortened length of these muscles pulling the Femoral head axis posteriorly.
Lumbar instability of L5-S1 segment seems to be associated
with lower Pelvic incidence (Golbakhsh et al 2012).
No:
There is no evidence that I can find that says that Pelvic incidence is irrelevant to injury.
Sacral slope / Sacral base angle:
This is the angle between the superior plate of S1 (Sacral
bases) and a horizontal line.
Normal ranges:
0.6 to 20 degrees (Boulay et al 2006)
20 to 40 degrees (Choi et al 2014)
How to measure the angle and how reliable is the measurement?
X-ray, which is reliable.
How valid are the measurements?
Research for:
It is a valid measure and it can be a clinically useful parameter for the optimisation
of total hip arthroplasty (Imai et al 2014).
Research against:
There is no evidence suggesting that a Sacral slope measurement isn't valid.
Do the measurements tell us anything about injury?
Yes:
Chaléat-Valayer
et al (2011) found that people with chronic lower back pain had a low Sacral
slope.
Sacral slope was found to be higher in Osteoarthritis of the hip joint (Bendaya et al 2014). This could possibly be due to tight hip flexors causing an increased Lumbar lordosis and therefore an increased Sacral slope angle.
No:
Nakipoğlu et al (2008) found no correlation between Sacral
slope and acute or chronic lower back pain.
Pelvic tilt:
The angle between this anterior Pelvic plane (APP) and a
vertical line in the standing position. Basically this is a more accurate way of determining the first measurement (ASIS and PSIS tilt) but uses different landmarks instead.
Normal ranges:
-2 to 30 degrees (Boulay et al 2006).
How to measure the angle and how reliable is the measurement?
The angle of rotation of the Pelvis on the lateral radiograph can be reliably calculated (Tyrakowski et al 2014).
How valid are the measurements?
Research for:
This is a more valid measurement as there is less bony size and shape issues. Pelvic tilt may affect final functional anteversion of the Acetabular cup (Blondel et al 2009).
Research against:
There is no evidence against the validity of this measurement.
Do the measurements tell us anything about injury?
This is basically the same as for the above ASIS and PSIS tilting but here are a couple more papers:
Yes:
Yes:
Patients with a
larger Pelvic tilt were more likely to experience residual back pain following
surgery (McGillion & Fairbank 2012).
No:
Chaléat-Valayer et al (2011) found no correlation between
chronic low back pain and Pelvic tilt.
Pelvic Obliquity:
This is essentially a level Pelvis looking from the back or
the front. Pelvic obliquity can be caused by leg length inequality,
contractures about the hips, as part of a structural scoliosis, or as a
combination of two or more of these causes.
How to measure the angle and how reliable is the measurement?
Looking at how level the Iliac crest and PSIS heights are.
It has been found that there is high reliability for testing Pelvic obliquity according to McGinley et al (2009).
It has been found that there is high reliability for testing Pelvic obliquity according to McGinley et al (2009).
How valid are the measurements?
Research for:
Walsh et al (2000) found correlation between leg length inequality
and Pelvic obliquity. So it can be a valid measure of leg length inequality.
Research against:
As for the ASIS and PSIS measurement there are potential issues with bony size and shape meaning that one side may have a higher Iliac crest due to a larger Ilium (Preece et al 2008).
Do the measurements tell us anything about injury?
Yes:
Correction of Pelvic obliquity appears to improve pain &
functioning in patients with chronic low back pain (Fann et al 2007). So this could indicate that a correction of an anatomical leg length inequality can help back pain but obviously the obliquity could be from a scoliosis and therefore be more of a functional difference. Either way it looks to be relevant.
Leg length discrepancy of more than 1cm may have a greater
prevalence of knee joint osteoarthritis (Harvey et al 2010).
Korpelainen et al (2001) found that leg length inequality
was one of the risk factors for Tibial stress fractures.
No:
Differences in movement patterns in the Pelvis were minimal comparing
a level Pelvis to a Pelvic obliquity caused by a 3cm artificial leg length
discrepancy (Needham et al 2012).
People with significant leg length differences suffer from
no more back pain than anyone else (Grundy et 1984).
Heel lifts or raises reduce low back pain in leg length
inequality but they didn't compare to a placebo heel lift/raise (Brady et al
2002).
Pubic Symphysis alignment:
This is essentially a level and equal Pubic Symphysis joint at the front of the Pelvis.
In most adults the Pubic Symphysis can shift up to 2 mm and rotate 1° (Becker et al 2010).
The width of the Pubic Symphysis ranges from 2.6 to 12.6 mm depending
on whether they have given birth to children (Alicioglu et al. 2008).
How to measure the angle and how reliable is the measurement?
X-ray or Ultrasound (Becker et al 2014) or Palpation but this is not that easy or as reliable as X-ray or Ultrasound.
How valid are the measurements?
Research for:
Lots of forces act on the joint, such as traction on the inferior part of the joint and compression of the superior region when standing, compression when sitting, and shearing and compression during single-leg stance (Meissner et al. 1996). This means the joint has the potential to move and cause problems.
Research against:
Most evidence points toward soft tissue problems in this area rather than alignment ones and evidence even in pregnancy is going against the theory that the excessive Pubic Symphysis movement causes the pain: No differences were found in serum relaxin concentrations in
pregnancy compared to the control group (Hansen et al 1996).
Do the measurements tell us anything about injury?
Unknown: the evidence here shows wide ranging alignments and there is need for more research to understand this area more.
Overall if you can measure the alignment and you believe that it is significant can you change it?
Orthotics:
Sacroiliac joint (SIJ) movement during single-leg stance is small
& almost undetectable by radiostereometric analysis (Kibsgård et al 2014).
However much more force will pass through the SIJ in function so the feet could
be the key by altering the ground reaction forces.
It was found that heel raises cause lower anterior Pelvic
tilt, Lumbar lordosis, & Sacral base angles compared to zero heel
inclination (Franklin et al 1995).
Muscles:
Muscles, such as the Rectus Femoris, Sartorius, Iliacus, Gluteus Maximus and Hamstrings have adequate lever arms to influence movement
in the Sacroiliac joint and so can move the Pelvis (Vleeming & Stoeckart,
2007).
Walking isn't the only movement we do, we bend a lot
too! Muyor et al (2012) found that Hamstring stretching causes a more aligned Thoracic curve & a more anterior Pelvic inclination during maximal trunk
flexion, which is better quality motion.
The important muscle groups/ slings that contribute to the
stability of Pelvis are as follows:
1) The inner unit (core/local stabilizers)
Pelvic floor, Transversus Abdominis, Multifidus, Diaphragm
& Psoas
2) The outer unit (sling systems)
Anterior & Posterior oblique slings; Longitudinal &
Lateral slings
The patterning of muscle activation & co-ordination of
muscle action ensure optimal stability & load transference in the SIJ and Pelvis.
Chicken or the egg?
Also there is the chicken or the egg argument: Did the pain
start due to abnormal Pelvic alignment or is the Pelvic alignment an effect of
being in pain? Well Moseley et al (2005) believe the latter, as they found that Pelvic alignment changed when artificial pain was inflicted and the Pelvis
returned to normal once the pain was gone. Also in Sacroiliac joint disorders
the Gluteus Maximus demonstrated significant weakness, which could cause
pelvic misalignment or abnormal Pelvic motion (Massoud Arab et al. 2011).
In summary:
In normal people 96.7% were found to have a difference in
leg length (O’Brien et al 2010). This may mean that nobody’s Pelvis is level
and normal and the issue with this is that not everyone has pain and injury. However
excessive Pelvic alignments must place more force on certain structures than
others and over time this may cumulatively create injuries in certain
individuals. Some would argue that abnormal findings exist in the normal
population without issue, e.g: 70% of pain free hockey players were found to
have an abnormal Pelvis or hips on MRI (AOSSM 2010).
and ..
MRI findings in asymptomatic individuals found that
stenosis, disc bulges, & disc degeneration increased with age (Boden et al
1990).
These types of findings can be used to call into question
the significance of structural dysfunction in the body, however the point that
they may be missing is that at some point their structural dysfunction may
become symptomatic.
See here: “A substantial percentage of asymptomatic Rotator Cuff tears became symptomatic & underwent anatomic deterioration (Moosmayer
et al 2013). Now obviously this is not a Pelvic reference but it makes my point,
which is that normal alignment of the Pelvis may range hugely but asymptomatic
individuals at the wider ends of the spectrum may have a higher risk of
developing symptoms over time. As prevention is better than cure then why not
strive for better alignment and movement.
Researching and finding accurate ways to determine and to
improve these issues through orthotics, exercise and education is the way
forward and as expected there is a great need for further research into these
areas.
Wow, what an excellent review! I appreciate the look at different ways to measure pelvic alignment and the research supporting the validity of the measurements as well as their relationship with injury.
ReplyDelete