STABILIZATION OF THE ANKLE JOINT DURING SIMULATED SUPINATION BY MEANS OF THE ANKLE ORTHOSES MalleoLoc® L AND MalleoLoc® L3
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DISCUSSION
The analysis of numerous clinical and biomechanical studies reveals
two basic principles of joint stabilization: active (the neuromuscular
system) and passive (ligaments, joint contact, and joint capsule)
functional joint stabilization. The two different stabilization mechanisms
can replace each other as well as complement each other
depending on the corresponding present needs [7].
This study examines the function of the MalleoLoc L and L3 during
simulated ankle supination, taking into account a dynamic injury
scenario. The simulated movements, similar to ankle sprains, in
a functional setting are close to the conditions prevailing during
everyday activities and sporting activities. A previous study already
showed that ankle orthoses (eg MalleoLoc from Bauerfeind AG)
have a stabilizing effect on the ankle joint by limiting the extent of
supination [3]. The current results also suggest that the stabilization
of the ankle joint by means of orthoses is possible in those functional
dynamic situations. In particular, the MalleoLoc L3 reduced both
the maximum joint displacement as well as the maximum speed
of joint displacement with respect to injury-related ankle inversion
and internal rotation.
Since supination injuries occur at approx. 50 – 150 ms after a foot's
contact with the ground, rapid and effective protection is crucial.
The data from this study prove that, especially at this stage, the
ankle orthoses already effectively counteract supination.
In addition to purely mechanical stabilization, ankle orthoses also
seem to provide neuromuscular stabilization for the ankle by
increasing pronation while the foot is in contact with the floor and
laterally shifting the center of pressure (COP), further promoting
the tendency towards pronation [8].
In a study population in the US (794,340 patients, according to
the ICD-9 code in the US Public Health Service), only 9% of the
affected patients received an orthopedic aid after suffering from
supination injury [1].
However, several studies have shown that early functional treatment,
including ankle orthoses, is superior to conservative therapy
requiring immobilization. The parameters used as a benchmark
are ROM, "return to sport", "return to work", permanent swelling,
objective stability, and patient satisfaction [4,5]. Additionally, ankle
orthoses can be used effectively for secondary prevention [9].
This study also shows that, during an induced supination movement,
the MalleoLoc L3 and the MalleoLoc L orthoses limit the inversion
and internal rotation of the foot substantially when walking, counteracting
damage caused by ankle sprains.
BACKGROUND
In-depth knowledge of the functional stabilization of the ankle
joint is a prerequisite for developing prevention measures against
typical injuries to the ankle. Neuromuscular, ligamentous, and
osseous mechanisms regarding the stability of the ankle joint are
of particular interest here.
Studies show that supination trauma is associated with excessive
inversion of the ankle in combination with pronounced internal
rotation of the ankle [2,6]. Therefore, the objective of this study was
to examine the effect of orthoses on the control of the ankle during
walking while simultaneously provoking supination. Specifically,
the study intended to investigate the extent to which the ankle joint is
stabilized using the newly developed MalleoLoc L and MalleoLoc L3.
STUDY DESIGN
A controlled laboratory study
METHOD
Sample: n = 20 subjects, Age: 22.3 ± 2.8 years,
13 women and 7 men
Test orthoses: MalleoLoc L / L3 (Bauerfeind),
Malleo Dynastab Boa (Thuasne)
Measurement systems: 3D motion analysis (Vicon MX)
Test method: By means of a specially designed platform,
the ankle's supination movement that is
characteristic of a lateral ankle injury was
imitated. As such, the subjects stood or
walked barefoot on the platform, which could
abruptly be tilted to result in 24° inversion
and 15° plantar flexion. In addition, the
subjective feeling of stability with and
without shoes when walking and during
"agility test" was recorded.
Inclusion criteria: Athletic, active persons aged 18 – 35 years
Verified unilateral, chronic ankle instability
based on the Cumberland Ankle Instability
Tool (CAIT score ≤ 25)
Prior history of recurring ankle injuries
RESULT
inversion:
Inversion is one of the characteristic rotations of the ankle joint
when there has been an injury to the lateral capsular ligament
structures. When wearing the MalleoLoc L3 while walking on the
tilting platform was tested, the results showed a reduced max.
inversion angle (-22.1 %) and a reduced inversion speed (-20.6 %)
compared to when no orthoses were worn.
When wearing the MalleoLoc L while walking was tested, the
results also showed a significantly reduced inversion speed (-13.4%)
compared to when no orthoses were worn. The reference orthosis
showed no significant reduction in the inversion angle and inversion
speed compared to the condition in which no orthoses were worn.
In a direct comparison between the MalleoLoc L3 and the MalleoLoc L,
the MalleoLoc L3 reduced the inversion angle and the inversion
speed more than the MalleoLoc L.
Similar results were observed during the simulation of the twisting
of the ankle joint while in a standing position. Through the use of
the MalleoLoc L3, the max. inversion angle and the max. inversion
speed was reduced by 33.7 % and 13.2 %, respectively. The use of
the MalleoLoc L also resulted in a reduction of the max. inversion
angle by 11.6 %, similar to the reference orthosis (not shown).
Internal rotation
A second important subcomponent of the injury mechanism is internal
rotation. The MalleoLoc L3 limited the max. internal rotation
angle by 43.5 %, while the MalleoLoc L caused no change in the
max. internal rotation angle.
The reference orthosis significantly reduced the angle by -18.7 %.
All three orthoses stabilized the ankle, leading to a significant
reduction of the max. internal rotation speed (C: -12.1 %, L: -12.1 %,
L3: -13.1 %).
Sense of stability
In addition to the objective measurement of stabilization, the subjective
sense of stability is a prerequisite for the patient to safely
transition back to normal mobility.
When the orthoses were worn without shoes during walking, the
MalleoLoc L3 was subjectively more stable than the reference
orthosis. The MalleoLoc L achieved moderate stability characteristics
and was reported to be between the MalleoLoc L3 and the
reference orthosis.
When wearing shoes, all three orthoses showed comparable
values regarding subjective stabilization.
In the "agility test", the ankle is more heavily loaded than during
normal walking due to the required changes of direction.
Here (Fig. 3), the MalleoLoc L3 was perceived to have more of a
stabilizing effect than the reference orthosis. Again, the MalleoLoc L
tended to be between the reference orthosis and the MalleoLoc L3
in terms of the subjective sense of the level of stabilization (Fig. 4).