Evaluation and
rehabilitation of Functional lumbopelvic Stability: the role of the back
muscles.
Lieven Danneels
Dept. of
Rehabilitation Sciences and Physiotherapy
Ghent University
The management of
patients with chronic low back pain (CLBP) using exercise therapy has until
recently been founded largely on empirical knowledge and clinical observations,
rather than on research findings regarding the function and dysfunction of the
muscular system. In this lecture an attempt is made to obtain a better insight
into the concept of functional spinal stability, the normal functioning of back
muscles and the characteristics of muscle dysfunction in LBP. Furthermore, different
rehabilitation strategies are discussed.
I. Functional
spinal stability
Biomechanically,
the human spine is a remarkable structure that must meet two seemingly
contradictory requirements: the achievement of sufficient stability and the
provision of adequate mobility. In protecting the delicate spinal cord and
nerve roots, providing adequate support/ stability/load-bearing capacity and
allowing motion in multiple planes, the spine performs seemingly conflicting
functions. Functional stability, both static and dynamic, is required to
satisfy these demands.
The
osteoligamentous spine alone cannot perform all these functions, and, as such,
the muscles and their ability to achieve stability and balance assume prime
importance.
Inspired by the
biomechanical research of Panjabi and others we introduced a concept of
functional lumbopelvic stability. The passive structures comprise the osseous
and articular structures, the spinal ligaments, and their restriction of
segmental movement. The active structures refer to the muscles themselves,
which stabilize the spinal segment mechanically. The muscles must have adequate
endurance and strength to perform this function satisfactorily (muscular
functional characteristics). The control subsystem refers to the control of the
muscles that provide this spinal support. Neuromuscular control provides a
concerted action between the afferent input (proprioception) and the efferent
output of the nervous system (coordination), and allows the muscles to contract
with the required strength and at the appropriate time.
The fourth
element, postural control, is the capacity to keep the projection of the body's
center of gravity within the base of support. In contrast to the concept of
spinal intersegmental stabilization, postural control has in our opinion an
important function within the framework of a more general concept of functional
spinal stability. These four elements constantly interact to offer adequate
stability to the spine during changes of posture and static and dynamic loading.
II. Muscle
function
Contributing to
functional lumbopelvic stability, a body of knowledge exists about the
importance of the paravertebral and abdominal muscles, and increasing evidence
is gathered about the muscles of the pelvic floor and the diaphragm being an
integral part of the muscular mechanism. However, in this lecture major
attention has been given to the back muscles.
II.1. Muscular
subdivision
The provision of
functional spinal stability involves a complex interaction between many muscles
of the trunk and limb girdles. While some muscles perform and control the
primary action, other muscles must work in synergy to balance any asymmetrical
forces, control unwanted movements, and offer support to articular structures.
Bergmark proposed
the concept of different trunk muscles playing different roles in the provision
of dynamic stability to the lumbar spine and introduced the concept of two
muscular systems: the global and the local systems. The global muscle system consists
of large, torque-producing muscles that act on the trunk and spine without
being directly attached to it. In addition to allowing movement of the spine,
the global muscles provide general trunk stabilization, but they do not have a direct
influence on the spinal segments. The local muscular system consists of muscles
that directly attach to the lumbar vertebrae and are responsible for providing
segmental stability and directly controlling the lumbar segments.
The addition of
muscle action imparts stability to the passive structures.
In this manner, it
appears that the local and global muscles of the trunk combine to exert
compressive loading of the spine, thereby enhancing its stiffness and
functional stability. However, it is the muscles of the local system that have
the greatest potential to prevent segmental buckling and control the motion
segment.
II.2. Strategy for
muscle rehabilitation
Rehabilitation of
the trunk muscle system is one of the most important aspects of treatment
undertaken by physical therapists to help LBP patients regain function and to
prevent the recurrence of further back pain episodes. A vital function of the
muscle system is to support and control the back in static and dynamic postures
during both load-bearing and non-load-bearing activities. A systematic
progression is imperative in the rehabilitation of the neuromuscular control
system and the muscle functional characteristics. Proprioception and
coordination can be considered as the foundations for efficient neuromuscu- ar
control. The super-structure consists of the two most relevant muscle
functional characteristics: endurance and strength .
III. Muscle
dysfunction in LBP
Trunk muscle
dysfunction is being increasingly implicated as a contributory factor in the
development or recurrence of subacute and chronic mechanical back complaints.
Factors such as the degree of trunk muscle strength and endurance, as well as
coordination and proprioceptive awareness, have been shown to be influenced by
the presence of low back pain.
A number of
studies have shown that CLBP patients have significantly lower trunk strength
when compared with healthy controls, while other authors reported that trunk
strength is not significantly affected in CLBP patients.
Decreased back
muscle endurance has not only been identified as a predictor of first-time
occurrence of LBP, but has also been demonstrated in persons with CLBP compared
to those with healthy backs.
Although these
studies provide data on gross muscle function, more specific information is
required concerning the pattern and degree to which individual muscles
contribute to the dysfunction. Recently, researchers have found that it is
mainly the action of the local system that is disturbed and inhibited in the
presence of CLBP.
There is some
suggestion that a compensatory substitution by the muscles of the global system
occurs in the presence of local muscle dysfunction.
This appears to be
an attempt by the neural control system to maintain the stability of the spine
in the presence of local muscle dysfunction.
There is also
evidence to suggest that the presence of LBP results in changes in the level of
proprioception and coordination, affecting the patterns of co-contraction,
reflex and reaction times.
Finally, an
association between back disorders and a decreased quality of postural control
has also been documented.
IV. Evaluation of
Functional Spinal Stability
Physical
therapists address the often complex muscle dysfunction in patients suffering
from LBP. Currently, muscle dysfunction is more and more assumed to be involved
in acute LBP and chronic LBP.
Every muscle
dysfunction requires a systematic yet specific approach.
Systematic because
we should aim at a progressive exercise program, specific because each patient
has to be individually assessed and rehabilitated.
In clinical
practice, there is an increasing need for objective assessment.
At our department
a test battery of exercises is used to diagnose and treat a possible
dysfunction of the different components contributing to functional spinal
stability.
Relevance The
development of a test battery to identify dysfunctions in back pain patients
can be important for clinical, economic and scientific reasons.
Firstly, within
its limitations, the battery gives a better understanding of dysfunction, if
any, and illustrates in which category(ies) the patient fails. The quality of
each separate exercise can also be determined.
Starting from the
test findings, the clinician can set up an individualized exercise routine.
Secondly, CLBP
places an increasing economical burden on the health budget. As a result,
objective tests become necessary to measure in what way LBP patients need and
will benefit from physical therapy.
Finally, many
researchers emphasize the need for the identification of different subgroups
within “the nonspecific LBP” population. The successful management of CLBP and
the homogeneity of the results among randomized controlled trials greatly
depend on the accurate identification of subgroups within this population. The
combination of an accurate physical examination with a functional test battery
allow to subdivide “the nonspecific LBP” population into subgroups. Based on the
findings of the physical examination and the quality of performance during the
different functional tests, an objective evaluation of the different elements
contributing to functional spinal stability is possible.
V. Rehabilitation
of Functional Spinal Stability
A recent focus in
the physiotherapeutic management of patients with CLBP has been the specific
training of muscles surrounding the lumbar spine, the primary role of which is
considered to be the provision of dynamic stability and segmental control to
the spine. Recent studies have shown that the lumbar multifidus is one of the most
important muscles for lumbar segmental stability. Precisely this muscle was
found to be atrophied in (sub) acute and chronic back pain patients.
The use of static
stabilization training has been advocated by Jull and Richardson as an ideal
means of improving the recruitment of the multifidus.
On the other hand,
many others support the role of high-loaded dynamic exercises in the successful
management of back pain.
Although courses
of vigorous physical training have been undertaken in CLBP and produced obvious
improvements, little information is available on the effects of different
contraction modalities of the paravertebral muscles.
Strength and
endurance training has long formed the basis for therapeutic exercise, while
coordination and stabilization training has only gained importance over the
last decade. In this lecture, a strategy of back muscle rehabilitation was
presented in which the traditional strength and endurance exercises are
combined with the rather new concept of stabilization training.
It has been argued
in the literature that the local muscle system is most affected in the CLBP
patient, and that it is the functional impairment of this system that is linked
to the high recurrence rate seen in CLBP.
As such, it is
recommended that the local muscle system be trained first, using the
appropriate physiotherapeutic regimen, until adequate stabilization is
achieved. Retraining of proprioception and coordination then provides a
foundation for the safe performance of more general exercise programmes
directed at general endurance and strength.
At our department
an experiment was conducted to determine whether strength training is
beneficial in addition to stabilization training, i.e.
whether strength
training has an further effect over and above that of stabilization training.
The findings of
this study indicate that strengthening exercises are essential to achieve a
volume-growing effect of the paravertebral muscles in CLBP patients, with a
static holding component to be critical to induce hypertrophy of the multifidus.
Although many
recent literature reports stress the importance of the incorporation of
stabilization training, the benefits of stabilization training as a foundation
for strength training should be pointed out.
Therefore, on this
moment a randomized clinical trial is conducted comparing the efficacy of
combined stabilization-strength training with that of isolated strength
training.
Once more, it has
to be mentioned that greater differences in outcome between the different rehabilitation
programs are expected if in future interventions the CLBP patients would be
categorized into different subgroups.
Giving a better
insight into the concept of functional spinal stability and normal back muscle
function, characterizing possible dysfunctions of the elements contributing to
functional spinal stablity, and providing evaluation and rehabilitation
strategies, this chapter aims at making a valuable contribution to the quality
of the daily work of everyone concerned with the LBP patient
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