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"Abductory twist'' -an element of observational gait analysis in low back pain -a case study

Authors:
67
Prabu Raja Gopala Krishnan(A,B,E,F),
Narasimman Swaminathan(B,E), Kavitha Vishal(B,E),
D’souza Vanita Vincent(E), Benjamin Varghese(E)
Department of Physiotherapy, Father Muller Medical College, Mangalore, India
“Abductory twist’’ – an element
of observational gait analysis in low
back pain – a case study
Key words: abductory twist, observational gait analysis, dynamic foot function,
medial longitudinal arch
SUMMARY
Background. The objective of this case study is to explain the influence of the altered lower limb kinematics in subject
with non-specific low back pain using simple video analysis and to emphasise the relationship between the altered lower
limb kinematics and low back pain. Low back pain management is one of the most challenging tasks encountered by the
therapist. Altered lower limb kinematics has been hypothesized to influence low back pain. A thorough biomechanical evalu -
ation of the lower limbs and the pelvic girdle along with the spine is important in successful rehabilitation of non-specific low
back pain.
Material and methods. An 18 year old cricket player with the chief complaint of low back pain presented to the depart-
ment of physiotherapy. Routine physiotherapy evaluation was carried out and the patient was diagnosed with non specific
chronic low back pain. He had undergone specific low back rehabilitation protocol elsewhere. On observation it was found
that there was a collapse of medial longitudinal arch during midstance. Following this, a through video analysis was done to
identify the abnormalities in kinematics. There was a rapid medial movement of the heel at the instant of heel off which was
coined as abductory twist in the literature.
Conclusion. Abductory twist is an abnormal finding in which there is an excess and prolonged foot pronation beyond
midstance. This alters the kinematics proximally leading to back pain. Observational gait analysis is mandatory in recurrent
non-specific low back pain. This case study explains the pathomechanical relationship between the foot and low back pain.
CASE STUDY
Zaangażowanie Autorów
A – Przygotowanie projektu
badawczego
B – Zbieranie danych
C – Analiza statystyczna
D – Interpretacja danych
E – Przygotowanie manuskryptu
F – Opracowanie piśmiennictwa
G – Pozyskanie funduszy
Author’s Contribution
A – Study Design
B – Data Collection
C – Statistical Analysis
D – Data Interpretation
E – Manuscript Preparation
F – Literature Search
G – Funds Collection
Adres do korespondencji / Address for correspondence
Prabu Raja Gopala Krishnan
Lecturer in Biomechanics and Clinical Therapist, Department of Physiotherapy Father Muller
Medical College, Mangalore, India, e-mail:praburaja7@yahoo.in, Ph +918242238289
Liczba słów/Word count: 2248 Tabele/Tables: 0Ryciny/Figures: 4Piśmiennictwo/References: 14
Otrzymano / Received 12.10.2010 r.
Zaakceptowano / Accepted 10.12.2010 r.
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© MEDSPORTPRESS, 2011; 1(4); Vol. 11, 67-73
INTRODUCTION
The biomechanics of the foot and ankle is important to
the normal function of the entire lower extremity. The body
requires a flexible foot to accommodate the uneven surface
and a rigid foot for the push off during gait. The dynamic
biomechanics of the foot and ankle complex, that allows
successful performance of these requirements, can be un -
derstood only during walking. Foot acts as a link between
the ground surface and leg. The functional biomechanics of
the foot and ankle is vital in the closed kinematic chain.
Pronation and supination movements occurring at subtalar
joint during the stance phase of gait are critical in deter-
mining the lower limb kinematics [1].
NORMAL KINEMATICS OF FOOT
IN A GAIT CYCLE (Fig. 2)
Prior to the initial contact, foot is in the supinated position.
At initial contact, foot starts to pronate. This pronation caus-
es the parallel orientation of the axis of the calcane ocuboid
and talonavicular joint and causes unlocking of midtarsal
joints. So the foot becomes flexible at this phase to absorb
the ground reaction forces. At the end of loading response
pronation stops. It starts to supinate from the pronated posi-
tion and reaches neutral by the end of midstance. Beyond
midstance it starts to supinate further. This supination leads
to locking of midtarsal joints, during which the midtarsal joints
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Krishnan P.R.G. et al., “Abductory Twist’’ – an element analysis in back pain
Fig. 1. Subtalar joint pronation and supination
Fig. 2. Foot kinematics during gait cycle
axes become perpendicular to each other. The foot now acts
as a rigid lever for a more efficient pull of peroneus longus
and the tibialis posterior, respectively. Thus, a synergistic
contraction of these two muscle groups stabilizes the midfoot
and first ray. First ray stabilization affords good alignment of
the first MTP joint and a rigid lever for push-off [3,4,5].
EFFECTS OF TIBIAL
AND REARFOOT VARUM
IN FOOT KINEMATICS
Usually rear foot varum is associated with tibial varum.
Both tibial varum and rearfoot varum deformities are sus-
pected to cause abnormal pronation of the STJ. When
rearfoot varus deformity is present, the plane of the meta -
tar sal heads is in an inverted position in relation to the
ground when the STJ is in the neutral position .This leads
to the initial contact of the lateral aspect of the heel and the
medial side of the foot is off the ground. In an attempt to
bring the medial side of the foot plantar grade which is
inverted to the ground with the STJ in neutral position, the
pronation moment on the STJ is increased since the later-
al forefoot has a large magnitude of GRF underneath it,
and the medial forefoot has little or no GRF underneath it.
The increase in STJ pronation moment will cause eversion
motion of both the calcaneus and forefoot during weight
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Krishnan P.R.G. et al., “Abductory Twist’’ – an element analysis in back pain
Normal biomechanics
Frontal analysis
bearing activities until the plane of the plantar forefoot is
contacting the ground. The reason for the increase in the
pronated position of the STJ with tibial varum and rearfoot
varus deformities is not because of the inverted position of
the calcaneus, but it is due to the inverted position of the
plantar forefoot in relation to the ground [6,7].
BIOMECHANICS OF ‘ABDUCTORY
TWIST’ (Fig. 3)
Foot pronation beyond midstance creates internal rota-
tion moment of the leg. When the contralateral limb swings
forward, it creates external rotation moment of the stance
leg. During the stance phase, the foot is held stationary by
the frictional force from the ground. Therefore, the foot can-
not rotate along with the transverse plane rotations of the
pelvis unless the foot is off the ground. So there is a con-
flict between the proximal external rotation moment creat-
ed by the pelvic rotations and distal internal rotation mo -
ment created by the late midstance pronation. Because of
the frictional force, the foot does not resupinate to accom-
modate external rotation moment. As the heel comes off
the ground, friction between the ground and foot can no
longer resist the external rotation moment from the trans-
verse plane pelvic rotation. This leads to the rapid medial
movement of the heel at the instance of heel off which is
called as ‘Abductory Twist’. This occurs due to the misma -
tching of tibial-femoral and pelvic transverse plane rota-
tions, due to the subtalar pronation during the late midstan -
ce .External rotation moment are stored as potential ener-
gy in the soft tissues surrounding the hip joint. Release of
this energy in the form of kinetic energy will occur at the
instance of heel off producing Abductory Twist. The foot
pronation beyond midstance, which causes abductory twist
could be a compensatory mechanism in response to rear-
foot varum and tibial varum or both [7,8,9].
FUNCTIONAL HALLUX LIMITUS
Functional Hallux Limitus (FHL) is a term in which the
first MTP joint shows no limitation when non-weight bear-
ing, but shows limited dorsiflexion during gait. Few authors
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Krishnan P.R.G. et al., “Abductory Twist’’ – an element analysis in back pain
Fig. 3. Analyses on a Treadmill
have postulated that Functional Hallux Limitus is a major
part of the abnormality that causes lumbar stress.
FACTORS LEADING TO
FUNCTIONAL HALLUX LIMITUS (Fig. 4)
Pathological Reverse Windlass mechanism
This occurs as a result of excessive pronation at the
subtalar joint. This excessive pronation could result from
the tibial and rear foot varum. So this excess pronation ex -
cessively tenses the plantar fascia pulling the hallux down
and prevents normal dorsiflexion in gait. This is one of the
reasons for functional hallux limitus.
Functional bony restriction of MTP joint
For the hallux to dorsiflex, the first ray should plantar -
flex. Functional limitation of hallux dorsiflexion is associat-
ed with the lack of first ray plantarflexion. Here, excess
sub talar pronation, which occurs due to tibial and rear foot
varum produces excess dorsiflexion of the first ray which
impede the dorsiflexion of the first hallux. This is called the
Functional Hallux Limitus.
Case Description: An Eighteen year old patient pre-
sented with the complaints of intermittent low back pain for
1 year, which was diagnosed as non specific low back pain
and underwent core stability program which turned out
unsuccessful. The patient complained of pain following ac -
tivi ties like running and batting. Physical evaluation of low
back did not reveal any specific structural involvement. Lo -
wer extremity evaluation has been emphasized as a sour -
ce of problem in recurrent low back pain in literature [12,
13]. Static evaluation of lower extremity revealed tibial va -
rum and rear foot varum bilaterally but more on the right
side. Video analysis was done during the test on a tread-
mill to evaluate the dynamic foot function.
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Krishnan P.R.G. et al., “Abductory Twist’’ – an element analysis in back pain
PATHOMECHANICS
DISCUSSION
Relationship between abnormal Gait and
Low back ache
Significance of Preswing Phase
At the end of the terminal stance there is 150 of hip ex -
tension, the knee is in full extension. The metatarsophalan -
geal joints are dorsiflexed 250 to 300. The swing phase is
properly prepared with the joints in these positions. From
the fully extended position, the hip and knee rapidly flex
while the ankle plantarflexes and the metatarsophalangeal
joints dorsiflex more as it enters the preswing phase. These
late preswing motions permit acceleration of the limb so
that at toe-off the iliopsoas muscle acts on a limb that is
already in motion. Failure of the preswing mechanism pre-
vents the limb from achieving adequate speed for toe-off
and results in the iliopsoas muscle working harder to accel-
erate the limb which could be an etiological factor for low
back pain [12,13].
Failure of proper hip extension during the single-sup-
port phase causes overuse of the iliopsoas muscle, which
could be a major etiologic factor in chronic low-back pain.
Several authors have mentioned a series of three
“rock ers” within the foot. These are; “heel rocker” the round
underside of the calcaneus, ankle rocker” (via ankle joint
dor siflexion), and “Forefoot rocker” (via metatarsophalang -
eal joints dorsiflexion) Failure of forefoot rocker leads to
Functional Hallux Limitus [13,14].
The natural tendency to extend the hip is progressively
lost. It is known that lumbar disk rupture occurs as a result
of either an extremely high force applied to it or a low force
that is repeatedly applied over a long period of time. Lum -
bar disks are quite strong under vertical loads, but they are
rather weak under stress that is applied by rotation and lat-
eral bending. Kapandji [3] has shown that, if the femur is
fixed and the psoas muscles acts, the lumbar vertebrae will
move. By analyzing with the reverse origin and insertion
force vector of the iliopsoas, he attributed this motion to
lumbar rotation and lateral flexion, which are considered as
the mechanical causes of lumbar herniations. When the
limb in the preswing phase fails to undergo proper acceler-
ation, the act of swing initiations impeded. There appears
to be a reflexive response to this inability to initiate ade-
quate swing motion: the lateral trunk bend. This response
occurs at the moment of toe-off and is toward the con-
tralateral side. The lateral trunk bend appears to universal-
ly use the contralateral quadratus lumborum and hip exten-
sors – to “drag” the trailing side into motion. This is consis-
tent with the clinical findings in patients with chronic low-
back pain. They often exhibit low back pain symptoms, par-
ticularly at the sacroiliac joint, on the same side as the sa -
gittal plane blockage. The patients also have chronic tight-
ness of the quadratus lumborum and gluteal muscles. In
addition, because the quadratus lumborum inserts into
both the iliac crest and the iliolumbar ligament, its constant
overuse can cause rotational stress to the L5 vertebra,
leading to low back pain [12,13,14].
CONCLUSION
This case study showed the significance of gait analy-
sis in the evaluation of chronic recurrent low-back pain.
72
Krishnan P.R.G. et al., “Abductory Twist’’ – an element analysis in back pain
Fig. 4. Functional hallux limitus
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Thorough evaluation of lower extremity kinematics is vital in
the management of low back pain. Abductory twist is an im -
portant abnormal finding which indicates that there is e
xcess
and prolonged foot pronation beyond midstance which alters
the kinematics proximally, leading to back pain.
This could be
observed in video analysis done during a treadmill test,
because eliminating the source of the problem is important to
avoid recurrences rather than treating symptoms.
ACKNOWLEDGEMENTS
The author would like to express his gratitude to Mr.
Shashikumar and Mr. Rajesh for their help in preparing dia-
grams and flow charts.
73
Krishnan P.R.G. et al., “Abductory Twist’’ – an element analysis in back pain
74
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The biomechanics of the foot and ankle is important to the normal function of the lower extremity. The foot is the terminal joint in the lower kinetic chain that opposes external resistance. Proper arthrokinematic movement within the foot and ankle influences the ability of the lower limb to attenuate the forces of weightbearing. It is important for the lower extremity to distribute and dissipate compressive, tensile, shearing, and rotatory forces during the stance phase of gait. Inadequate distribution of these forces could lead to abnormal stress and eventual breakdown of connective tissue and muscle. Pathologies such as heel spurs, hallux valgus, neuromas, hallux limitus, shin splints, and nonspecific knee pain result from abnormal mechanics of the foot and ankle. The use of orthotics to re-establish the normal biomechanics of the foot and ankle have profound clinical applications. The combined effect of muscle, bone, ligaments, and normal biomechanics will result in the most efficient force attenuation in the lower limb. J Ortho Sports Phys Ther 1987;9(1):11-16.
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Joint structure and function. A comprehensive analysis
  • K P Levangie
  • C C Norkin
Levangie KP, Norkin CC. Joint structure and function. A comprehensive analysis 3rd ed; 2001: 367-402.