Download That nagging pain in the bum

 That nagging pain in the bum!
What do we really know about piriformis muscle
and how can it help us with exercise
prescription.
Brief History of Anatomy
To understand a healthy, diseased or dysfunctional human body, a
multidisciplinary approach to anatomical study is essential. It is not only
crucial to understand the birth of the body’s unique single cells and their
journey of development in to specific structures and systems but how
they may relate to one another synergistically is vital. Mankind’s
curiosity with the human body started as early as 380 BC with
Hipprocrates. Although their knowledge was scant and their procedures
were often crude by modern standards, Hippocrates the ‘father of
medicine’ and other Greek physicians established the foundations that
are the basis for the study and treatment of mankind as we know it
today (Whiting & Zernicke, 2008). It must be recognised that their
breakthroughs were extraordinary, albeit niave compared with our
current understanding. Then came the fifteen hundreds when Vesalius
promoted the practice of focusing on what was discovered at the time
and not taking previous anatomical literature verbatim.
With man’s interest in anatomical study growing day by day,
acknowledging there is still so much to know about disease and
dysfunction, clinical advancements in the diagnostics and treatment of
the human body show no sign of slowing. It is imperative at this point
that we appreciate that not all diagnostics are one hundred percent
accurate and each have their own limitations to anatomical study.
These flaws will be discussed further in this study.
This study will be looking at investigating descriptive epidemiological
studies; case studies and the distribution of disease or dysfunction, and
analytical research that deals with the incidence, distribution and control
of disease in a population: questioning the research strategies that
reveal contributing factors of disease or dysfunction. Both will be
examining numerous perspectives within the medical arena.
The piriformis muscle is a central pillar to biomechanical dysfunction;
research has shown that when it’s dysfunctional, not only can the pelvis
be taken out of alignment but it can also affect the functional
performance of the upper and lower limbs. Understanding the piriformis
muscle and all its anomalies is imperative to understanding an
individual’s needs and avoiding generalization. It is therefore the
individual’s function that is interesting and if dysfunctional, then a
common sense approach of different arenas would command the best
method to rid the problems. Research studies of anatomical
observations, imaging, functional screens, manual treatment will be
examined throughout this paper.
In the Sixteenth Century an Italian Professor at Padua, Spigelius, was
the first anatomist to name the piriformis muscle. The piriformis muscle
is one of six deep small hip external rotators. It is uppermost to the
gluteal muscle group and imperative to the arrangement of the vessels
and nerves in the buttocks. Key to understanding this muscle we must
first become orientated with its anatomical features and functions; then
later we shall be examining the literature with regards to the variety of
its form and structure histology and the significant implications these
have. The piriformis muscle largely fills the greater sciatic foramen,
through which the branches of the sacral plexus and branches of the
internal iliac vessels to the gluteal and pudendal regions leave the
pelvis; therefore, the vessels and nerves that enter the buttock
necessarily are closely related to this muscle (Williams 1999).
The piriformis is a voluntary muscle, innervated by motor neurons
whose cell bodies lie within the central nervous systems and whose
axons extend peripherally to the muscles. It is pyramidal in shape
whose muscle fibres run in a straight line from the origin to the insertion
in the same plane as gluteus medius. Its proximal attachment starts at
the anterior aspect of the second to fourth sacral segments and extends
between the lateral to the anterior sacral formina – see figure 1. From
its additional attachment on the gluteal surface of the ilium, near the
posterior inferior iliac spine, and the pelvic surface of the sacrotuberous
ligament it then feeds out of the pelvis through the greater sciatic
foramen. Bouisson arcade is a lower convex fibrous arcade stretched
from the anterior edge of the greater sciatic notch to the sacroiliac joint,
immediately above the upper edge of the piriformis muscle
(Paturet,1951). Its fibres continue downwards laterally and forwards
narrowing into a rounded tendon to attach to the medial side of the
greater trochanter of the femur.
The innervation of the piriformis muscle comes from the piriformis
nerve, from the sacral plexus L5, S2, but mainly S1. (Palastanga et al,
2006). It leaves the pelvis through the greater sciatic foramen and
below through or above the piriformis muscle before extending distally
between the greater tuberosity of the femur and the ischial tuberosity of
the pelvis into the lower extremity. The Arterial Supply comes from the
superior and inferior gluteal artery along with the lateral sacral
artery. Most sciatic nerves lie inferior and posterior to the piriformis and
bifurcate into common peroneal (fibular) and tibial nerves outside of the
pelvis.
The piriformis muscle has a unique, albeit very assorted, relationship
with the sciatic nerve which is discussed later. Understanding the
complete, although varied, anatomical relationship that the sciatic nerve
has on the piriformis muscle may have a clinical importance in the
cause and development of disease will lead to a superior management
of sciatica. However, it is important to note that as far back as 1900’s
the action and function of the piriformis muscle has been under much
debate as has its anatomy.
What does piriformis do?
A considerable quantity of literature observes the action of the piriformis
muscle from an anatomical position or in a seated upright position with
hip flexion close to 90 degrees. In an anatomical position piriformis
muscle is a lateral rotator, whilst in a seated position it assists in
abduction at the hip. The additional action of the piriformis muscle is to
stabilise the head of the femur in to the acetabulum whilst the superficial
pelvic muscles perform their action. Cael (2009) observes that if there is
excessive contraction of the piriformis muscle causing posterior tilt of
the pelvis and external rotation of the hip then excessive lengthening
leading to anterior tilt of the pelvis, hip adduction and hip medial rotation
is inevitable. However, it is also important to consider that this may only
be true if the surrounding musculoskeletal systems are also
dysfunctional. It is important to consider that the piriformis muscles’
functional capacity depends upon the position of the hip joint with
respect to flexion, extension, adduction and abduction.
Gaining the correct knowledge and full understanding of the
biomechanics and anatomical anomalies of the piriformis will we then
be able to provide the therapist/physician/Biomechanics Coach with a
superior management of dysfunction and disease and possibly the
prevention of future injury. Understanding the various anomalies within
the hip joint region would be of great advantage during surgical
procedures and for post-operative management. Kapandji (1970b) and
Steindler (1977) took investigative biomechanics and kinesiology of the
pelvis to another level when they observed the piriformis muscle
changes from an external rotator in hip extension to an internal rotator
in hip flexion. Biomechanics Coaches today have embraced this
understanding and use it successfully in the management programmes
of hypertonic piriformis muscles. In most cases the distinction between
disease and injury is clear, however there are times when these two
distinctions crossover i.e. Osteoporosis can cause bone fractures
(Whiting & Zernicke, 2008).
What affect can it have on the sciatic nerve?
Cael (2009) observed tightness in piriformis may compress the sciatic
nerve, causing radiating pain, weakness, and altered sensation in the
lower extremity. This mimics the symptoms of nerve root compression
associated with a protruding intervertebral disc or degenerative changes
in the spine. These factors are known as ‘risk factors’ and are classified
as Intrinsic or Extrinsic factors. Intrinsic risk factors are characteristics of
a biomechanical, biological or psychological nature that may predispose
and individual to the disease or injury. Extrinsic risk factors are the
external or environmental characteristics that influence a person’s injury
risk. Intrinsic risk factors are thought to predispose an individual to
injury, and once a person is susceptible, extrinsic or ‘enabling’ factors
may interact with predisposing factors to increase the likelihood of injury
(Meeuwisse, 1994). Many clinical studies are investigating the positional
relationships between the piriformis muscle and the nerves within this
area. Russell et al, (2008) set an objective to evaluate the relationship
of the sacral nerve roots in relation to the piriformis muscle.
It’s interesting to note that although most literature teaches most of
piriformis innervations is from S1, there are however anomalies to this.
Magnetic Resonance Imaging (MRI) was used on patients who had no
history or clinical suspicion of piriformis syndrome.
Anatomical Variations in piriformis
Windisch et al (2007) conducted a cadaveric study investigating
lumbosacral and buttock pain in patients history where piriformis muscle
was the contributing factor to the pain. The main focus of the study was
to detail the form and structure of the piriformis muscle with a particular
interest in the shape and the musculotendinous junction. Emphasis
throughout this study was given to specific detail of piriformis tendon
diameter, insertion and its fusion with adjacent tendons. The etiology
and the clinical manifestation of piriformis syndrome have been
examined and reviewed. Certain cadavers were removed from the study
due to the malformation of bones or tears in the piriformis muscle.
The action of piriformis muscle and it’s relationship with the sciatic
nerve varies considerably. The fusion of these different tendons can be
explained by the development of the limb, taking place over a 5-week
period from the fourth to the eighth weeks. During the fifth week, the
primary germ layers of an embryo invades the limb bud and forms two
large condensations, one dorsal to the axis resembling a column and
one ventral to it.
The dorsal muscle mass (gluteus group, piriformis) gives rise in general
to the extensors and abductors of the lower limb, whereas the ventral
mass gives rise to the flexors and adductors (obturator internus,
gemellus superior and inferior). The piriformis spreads out from the
dorsal aspect of the pelvis through the greater sciatic foramen to reach
the inner side of the sacrum.
Consider techniques used in Sports Massage such as trigger point
technique.
Testut (1884) describes the ‘Type’ variants of the relationship between
the piriformis muscle and the sciatic nerve in their books about
anatomical abnormalities in humans.
Does size matter?
Grimaldi et al, (2009) investigated the changes that occur in the deep
abductor muscles in association with differing stages of unilateral
degenerative hip joint pathology. The chosen method was cross
sectional MRI eliciting muscle morphology from the study as they
believed this is not the most accurate tool for this purpose. The study
summarised the findings with no significant change in the piriformis
muscle volume of the affected legs of the diseased group compared to
the healthy legs of the controlled group; however they found an
increase of muscle volume in the piriformis muscle of the unaffected
leg. Although the study found an increase in muscle volume they have
not identified whether the piriformis muscle is hypertrophied or
hypertonic. According to Donofrio et al (1988) relevant to the
biomechanical conditions, an increase in piriformis muscle tension, due
to dysfunction of the pelvis, causes the form and structure of the
piriformis muscle. Therefore, is size of piriformis important or just
academic? It would be important to distinguish the difference of these
findings as the management of a hypertonic muscle would be
completely different to the treatment of a hypertrophied muscle, if at all.
Ratnatunga et al (2010) summarised from their findings that posttraumatic spasm and contracture of the piriformis is thought to be the
usual cause of piriformis syndrome.
Jiri Dorvak who is a professor of neurology and is the FIFA Chief
Medical Officer has established that a muscle relaxes maximally after it
has been contracted sub-maximally and for a prolonged period,
providing the muscle with the capacity to relax. Papadopoulos et al.
(1990) states that intrinsic pathology of the piriformis muscle (e.g.
myofascial pain, anatomic variations, and myositis ossificans) as
primary piriformis syndrome, and all other aetiology as
secondary. Difficulties arise when the identification of risk factors
because in most situations, factors act in concert, and injury or disease
is a result of this interaction Diop (2002) has shown in his study an
increase in muscle volume of the piriformis may cause sciatic pain. The
treatment plan to relieve the pressure on the nerve was cutting of the
piriformis muscle. However, is it the increased volume of the piriformis
muscle or the dysfunctional pelvis that may be causing this? Therefore,
if the cause of sciatic pain is by a dysfunctional pelvis, by cutting the
piriformis muscle are we likely to eliminate the pain?
Piriformis Syndrome
Recent literature has linked much of the anatomical relationship of the
sciatic nerve and piriformis muscle as contributing factors to piriformis
syndrome and a disputed cause of very low back or buttock pain since
the idea was first postulated by Yeoman, 1928. Since then, present day
included, the piriformis muscle has been quite a celebrity when it comes
to understanding the cause’s piriformis syndrome. Many researchers
have made impressive attempts to find the most accurate diagnosis of
piriformis syndrome, with a superior management programme for
recovery. Freiburg and Vinke (1934) considered the negative behaviour
of the piriformis muscle and its fascia might be due to inflammation of
the sacro-iliac joint or the overlying lumbosacral plexus. Four million
years ago the body was built for hunting and gathering, however, for the
past 100 years we have been sitting. These daily movement patterns
are far from our original design and possibly creating the piriformis to be
more active than the original design was for as it has not had time to
adapt given the relatively short period of time over which these daily
tasks have evolved. “Human evolution has been outpaced by the
industrial revolution”. It is not, therefore, surprising that strain of this
muscle is quite common, but unfortunately quite overlooked.
(Palastanga et al, 2006).
Management
Guvencer et al (2008) used cadaveric study to investigate what occurs
between the piriformis muscle and sciatic nerve after a functional
screen. The embalming method was not discussed within this paper,
however, through the process of embalming the malleability of human
tissue becomes more rigid therefore the question arises of the internal
and external validity of this study. Post piriformis stretch showed there
was a significant stenosis of the notch by volume increase or
hypertrophy of the piriformis muscle; this will consequently compress
the sciatic nerve. The question remains as to the credibility of this work
on cadavers and its relevance to a functional unit. If it was a live subject
then although there is little evidence to support stretching for a tight
muscle, anecdotally subjects seem to feel better initially, but then their
stiffness or tightness often recurs after a short period of time. If this
evidence from Guvencer is to be considered relevant then this may
explain why the problems persist post stretching of a muscle, and
perhaps we can theorize that any short term benefits which may be
merely proprioceptive bombardment. Furthermore the work by Dorvak
and many others has shown that stretching is not the management of
choice for a muscle that is hyperactive which throws further doubt on
the relevance of this piece of work. A manual therapy practice is either
of the Beatty, Pace, and Frieburg manouvers stretch of the piriformis
muscle in isolation. Work by Dorvak and many others has shown that a
low grade contraction of a muscle that is in spasm or is hyperactive
improves its capacity to relax. If this so-called piriformis syndrome is
due to piriformis hyperactivity, the stretching management for this
condition may be one that becomes less popular. What came first is
irrelevant, it’s the individual presentation that is the key feature into
understanding the various morphological symptoms. These anomalies
and understandings are important in all arenas of clinical and therapy
work. Examination and management methods should consider the
response of muscles of the abductor synergy and function to joint
pathology and note; it is not homogenous between muscles or across
stages of pathology.
The gluteal region is also a common area for intramuscular injections of
medication which may endanger the vast variables of the neurovascular
complex within this area. From the results above we have to question
why most trigger point techniques and massage literature distinguishes
the lateral third nearest the insertion is the best place to palpate
piriformis muscle. it would be interesting to see the results from a piece
of work looking at performing trigger points in the distal 1/3 of the
‘tendon’ versus the proximal 1/3. If piriformis muscle size increase is the
cause of non discogenic sciatic and low back pain, and we know sub
maximal contraction of a muscle that is hypertonic releases the ‘grip’ of
the muscle back to a normal state; then is this all that is necessary to
reduce such symptoms that all to often are treated aggressively?
Conclusion This paper has probably stimulated more questions than it
has provided answers with the need for further research in to the true
understanding of the piriformis muscle; action, function, healthy and
dysfunctional. Without this research Piriformis syndrome will remain a
controversial and nebulous diagnosis. There are no studies reporting an
established pathology in enough patients to satisfactorily validate the
existence of piriformis pathology and anatomical causes of piriformis
syndrome are rare. From a biomechanical perspective it would be
interesting also to research other factors that may cause piriformis
loading. It has been postulated that a number of other dysfunctions can
cause piriformis problems and therefore pelvic dysfunction, such as;
upper limb and neural tension, spinal stiffness, muscle spasm in
quadratus lumborum, infraspinatus and others as well as muscle
weaknesses. Research into these and other areas will provide more
information to enable an objective view on the role and function of
piriformis and hopefully provide a means by which Biomechanics
Coaches and therapists can manage and prevent issues with this
muscle and its associated structures.