Wolf Petersen, MD, Robert Welp, MS, and Dieter Rosenbaum, PhD
From the Department of Trauma, Hand, and Reconstructive Surgery
and the ‡Movement Analysis Lab, Orthopaedic Department,
University Hospital Muenster, Muenster, Germany
Background: Previous studies have shown that eccentric training has a
positive effect on chronic Achilles tendinopathy. A new strategy for the
treatment of chronic Achilles tendinopathy is the AirHeel brace.
Hypothesis: AirHeel brace treatment improves the clinical outcome of
patients with chronic Achilles tendinopathy. The combination of the
AirHeel brace and an eccentric training program has a synergistic effect.
Study Design: Randomized controlled clinical trial; Level of evidence, 1.
Methods: One hundred patients were randomly assigned to 1 of 3
treatment groups: (1) eccentric training, (2) AirHeel brace, and (3)
combination of eccentric training and AirHeel brace. Patients were
evaluated at 6, 12, and 54 weeks after the beginning of the treatment
protocol with ultrasonography, visual analog scale (VAS) for pain,
American Orthopaedic Foot and Ankle Society (AOFAS) ankle score, and
Short Form-36 (SF-36).
Results: The VAS score for pain, AOFAS score, and SF-36 improved
significantly in all 3 groups at all 3 follow-up examinations. At the 3 time
points (6 weeks, 12 weeks, and 54 weeks) of follow-up, there was no
significant difference between all 3 treatment groups. In all 3 groups, there
was no significant difference in tendon thickness after treatment.
Conclusions: The AirHeel brace is as effective as eccentric training in the
treatment of chronic Achilles tendinopathy. There is no synergistic effect
when both treatment strategies are combined.
Clinical Relevance: The AirHeel brace is an alternative treatment option for
chronic Achilles tendinopathy.
Keywords: Achilles; tendinopathy; AirHeel brace; eccentric training; ultrasonography
Chronic Achilles tendon pain, manifested as a localized painful
thickening of the tendon, is relatively common among middle-aged
recreational athletes. Gradual onset of pain in the Achilles tendon with
structural changes in the midportion of the tendon (2-8 cm above the
calcaneal insertion) is called tendinopathy and is generally considered
to be a difficult condition to treat.
Several studies have demonstrated that treatment by heavy-load
eccentric calf muscle training leads to good clinical results, with
decreased pain and full recovery to previous activity level. Therefore,
this treatment strategy has to be considered the standard for the
treatment of chronic tendinopathy of the Achilles tendon. However,
our clinical experience with eccentric training has shown that some
patients discontinue this treatment because of the experience of pain
Conservative treatment options other than eccentric training for
chronic Achilles tendon pain have previously been less encouraging.
In one literature review, the authors stated that many common
treatments such as rest, strength and flexibility exercises, anti-
inflammatory agents, or corticosteroids do not alter the natural
course of this disease. These inconclusive results are explained with
the multifactorial origin of Achilles tendinopathy so
that one single
treatment appears insufficient. Very few prospective randomized
controlled trials exist to assist in choosing the best evidence-based
Chronic Achilles tendinopathy is often associated with paratendinitis.
Local massage is regarded as an important technique to loosen
adhesions in paratendinopathy and to remove metabolites and other
waste products via the venous plexus of the paratenon, and might
have a positive effect on the course of chronic Achilles tendinopathy.
The AirHeel brace (Aircast, Vista, Calif) is specifically designed to
treat Achilles tendinopathy. The manufacturer claims that the 2
interconnected air cells located under the heel and above the
calcaneus apply pulsating compression with every step to help reduce
swelling and discomfort, and enhance circulation by a local massage
effect, but these effects have not been proven with scientific studies.
The purpose of this prospective randomized study was to evaluate 3 different treatment protocols for chronic midportion tendinopathy of the Achilles tendon: (1) eccentric training, (2) the AirHeel brace, and (3) a combination of eccentric training and the AirHeel brace.
Our first hypothesis was that the AirHeel brace improves symptoms of chronic noninsertional tendinopathy. The second hypothesis was that the combination of eccentric training with the AirHeel brace has a synergistic effect.
MATERIAL AND METHODS
One hundred patients were included in the study and randomly
assigned to one of the 3 different treatment groups (Table 1): group
1, eccentric training (37 patients); group 2, AirHeel brace (35 patients);
and group 3, combination of the AirHeel brace and eccentric training
The patients were recruited by announcing the study in local
newspapers. Randomization for assigning the subjects to a treatment
group was achieved with selecting random numbers between 1
and 3 in Microsoft Excel (Microsoft Corp, Redmond,Wash).All of
these patients had been suffering from a gradually evolving painful
condition in the Achilles tendon located at the midportion for at least
3 months. Most of the patients were recreational athletes involved in
activities such as jogging or running (29%), walking (15%), or other
sports activities (33%).In all cases, the diagnosis was based on clinical examination performed
by the same investigator (R.W.), showing a painful thickening
of the Achilles tendon located at a level of 2 to 6 cm above the
tendon insertion. In all tendons, the diagnosis was confirmed by
ultrasonography, in which the tendon changes were described as a local
thickening of the tendon, irregular tendon structure with hypoechoic
areas, and irregular fiber orientation.
In all cases, the condition caused pain during tendon loading that limited
the desired activity level. Most patients (87 of 100) had previously been
advised to treat the problem by resting the affected leg. A majority
of the symptomatic tendons had been treated with other treatment
regimens (nonsteroidal anti-inflammatory drugs, 78; local cortisone
injection, 3; physiotherapy, 45; or orthotic treatment, 23) without
satisfactory effect on the Achilles tendon pain. Patients with previous
surgery or tendon rupture were excluded from this study. At the initial
visit, a clinical examination with assessment of height, body weight, and
assessment of local tenderness was performed in every patient. The
amount of pain during rest and activity was evaluated by the patients
on a 10-cm-long visual analog scale (VAS). On the VAS, the amount of
pain is recorded from 0 to 10 cm, where no pain is recorded as 0 and
severe pain is recorded as 10. The joggers registered the amount of pain
during jogging, runners during running, and walkers during walking (ie,
registration depended on the patient's type of activity). Function of the
hindfoot region was assessed with the American Orthopaedic Foot and
Ankle Society (AOFAS) hindfoot scale. Every patient completed the Short
Form-36 (SF-36). Ultrasound examination was performed to evaluate
thickening of the tendon in its midportion (2-6 cm above the insertion)
and the presence of paratendinitis. The tendon diameter was evaluated
on longitudinal cross-sections. Other findings such as hypoechogenic
structures, nodules, etc were also noted. All patients with pain at the
insertion of the tendon (insertional tendinitis) or Haglund deformity
were excluded from the study.
Eccentric Training Model
All patients in this intervention group were instructed on how to
perform the eccentric training by the same investigator (R.W.). They
were given practice instruction and a written manual on how to
progress. The correct execution of the exercises was confirmed after
6 weeks. The training protocol was adopted from previous studies.
The patients were instructed to perform the eccentric exercises 3
times daily, 7 days per week, for 12 weeks. They were also advised to
use stable shoes when performing the exercises.
In the beginning, the loading consisted of the body weight. From
an upright body position and standing with the whole body weight
on the forefoot, with the ankle joint in plantar flexion (Figure 1A),
the calf muscles were loaded by lowering the heel (Figure 1B). Two
types of exercises were used. The calf muscle was eccentrically
loaded both with the knee straight (Figure 1C) and, to maximize
the activation of the soleus muscle, with the knee slightly bent. The
calf muscles were only loaded eccentrically; no following concentric
contraction was performed, as the patients were instructed to
use the noninjured leg and/or the arms to return to the starting
Each of the 2 exercises included 3 sets of 15 repetitions. The patients
were told that muscle soreness during the first 1 to 2 weeks of
training was to be expected and that the exercises were potentially
painful, but to stop if the pain became disabling. When the patients
could perform the eccentric loading without experiencing any
minor pain or discomfort, they were instructed to increase the
load on the tendon by using a backpack increasingly loaded with
weights to reach a higher level of training. Thus, the eccentric
loading of the calf muscles was gradually increased. During the
12-week training regimen, jogging, walking, and bicycling were
allowed if it could be performed with only mild discomfort or pain.
The AirHeel is a specifically designed brace for the treatment of Achilles
tendinopathy (Figure 2). Patients were instructed to wear the AirHeel
during the daytime.
The evaluation of the efficacy of the treatment regimen was performed
after 6 and 12 weeks of the intervention. At each follow-up, the
outcome was assessed with the VAS for pain at rest, during gait, and
during sports activities; the AOFAS hindfoot scale; the SF-36; and
ultrasound examination. To avoid bias, the evaluation of the VAS and
the SF-36 was done by the patient alone. All patients were questioned
for possible adverse effects of the treatments (eg, tendon rupture,
discomfort, severe pain).
For a 1-year follow-up, patients were asked to fill out the questionnaires for
the AOFAS, report the pain on the VAS, and to report whether they reached
their preinjury sports level.
The experimental protocol for this study was approved by the Ethical
Committee of our University. All patients gave their consent to
participate in this treatment model.
Commercial software (StatView 5.0, SAS Institute, Cary, NC) was used
for all statistical calculations. A repeated-measures analysis (3 groups
by 4 easurements) was performed. The results are expressed as mean
± standard deviation (SD) throughout this article. A P value < .05 was
American Orthopaedic Foot and Ankle Society (AOFAS) Score differences were significant.
Anthropometric Data of the 3 Treatment Groups
The anthropometric data of the patients involved in the present study
show that there were no significant differences in age, duration of
symptoms, gender, height, weight, and body mass index between the
3 treatment groups (Table 1).
The total dropout rate during the 12-week treatment period was
14% and did not differ between the 3 treatment groups. Some of the
dropout patients discontinued the eccentric training because of severe
pain experienced during the exercises. The main reason for dropout in
the AirHeel group was discomfort due to poor fitting of the brace.
At the 1-year follow-up, two patients (1 in the AirHeel group, 1 in the
eccentric training group) had undergone surgery. Twelve patients
were lost to follow-up. Figure 3 shows the fate of all patients entering
American Orthopaedic Foot and
Ankle Society (AOFAS) Score
The AOFAS score improved significantly during the course of the study, from 77 points to 85 points after 6 weeks, to 89 points after 12 weeks, and to 85 points after 54 weeks of treatment (Figure 4) without any significant differences between the 3 different treatment groups. At the 1-year follow-up, the AOFAS score was still improved by 10% in the eccentric training group and in the brace group, and by 12% in the combination group as compared with the pretreatment situation. These differences were significant (P < .0001).
Pain during activities of daily living assessed with a VAS (where 0 cm = no pain and 10 cm = severe pain) improved significantly in all 3 treatment groups (Figure 5). In group 1 (eccentric training) and group 3 (combination), pain was reduced 20% and 22% after 6 weeks and 60% and 56% after 12 weeks, respectively. In group 2 (AirHeel), pain was reduced by 41% after 6 weeks with no further decrease after 12 weeks (35%). At the 1-year follow-up, pain was still reduced by 30% in the eccentric training group, by 27% in the brace group, and by 53% in the combination group as compared with the pretreatment situation. These differences were significant (P < .0001).
Pain during walking was higher than pain during activities of daily living, but there was also a significant improvement of pain during walking assessed with the VAS in all 3 study groups (Figure 6). In group 1, there was a 25% decrease of pain after 6 weeks and 71% decrease after 12 weeks. In group 2 and in group 3, there was a pain reduction of 43% and 36%, respectively, after 6 weeks but there was no significant further pain reduction after 12 weeks (group 2, 50%; group 3, 56%). At the 1-year follow-up, pain during walking was still reduced by 45% in the eccentric training group, by 46% in the brace group, and by 64% in the combination group as compared with the pretreatment situation. These differences were significant (P < .0001).
The highest pain level (overall 5.7) was experienced during sports activities. In each treatment group, the pain level decreased significantly at 6 and 12 weeks (Figure 7). At each time point, there was no significant difference between the 3 treatment groups. At the 1-year follow-up, pain was still reduced by 51% in the eccentric training group, by 47% in the brace group, and by 74%
in the combination group as compared with the pretreatment situation. These differences were significant (P < .0001). In all pain categories, the eccentric training group and the brace group had lost some of the benefit seen after the 12-week treatment period whereas the combination group showed a further improvement. However, no significant group differences were seen in any of these parameters.
In all pain categories, the eccentric training group and the brace group
had lost some of the benefit seen after the 12-week treatment period
whereas the combination group showed a further improvement.
However, no significant group differences were seen in any of these
At the initial examination, the sagittal tendon diameter was significantly greater than the diameter of the healthy contralateral
side. However, during the course of the study, there was no change in
the tendon diameter in any of the 3 treatment groups.
The SF-36 was used for quality of life assessment at time point 0, and
after 6 and 12 weeks of treatment (Table 2). Only 2 of the 8 different
categories improved significantly during the course of the study—
function and pain. Function improved by about 13% in group 1 and
in group 2. In group 3, function improved by about 17%. Pain also
improved significantly, by about 13% in group 1 and group 2. In group
3, pain improved by 19%. There was no significant difference between
the 3 treatment groups.
Return to Sports
Return to preinjury sports level was evaluated after 54 weeks. Ninety
percent of patients reached their preinjury activity level. There was no
statistical significant difference between the groups.
Function improved by about 17% when both treatments were
combined. Pain also improved significantly, by about 13% in the
eccentric training group and in the AirHeel brace group. Pain improved
by about 19% in the combination group.
It is difficult to compare outcome between studies because different
measures of outcome are often used. Although patients' perception
of general health is considered to be increasingly important, only a
few studies on Achilles tendinopathy have used this as a measure of
outcome. The SF-36 is one of the most widely used instruments for
addressing patient self-assessment. Clinical experience of patients with
intra-articular calcaneus fractures has shown that limitations in many
fields of daily life are to be expected. In a study about the outcome after surgical treatment of calcaneal fractures, Westphal et al showed Stanish et al. The exact background of the good clinical results
that the SF-36 detects more limitations in general health status than achieved with this method has long been unknown. It was believed
other classic instruments. In this context, the SF-36 seems to be an that eccentric loading of the tendon enhances collagen fibril
ideal tool for measuring outcome and should be used in future studies. alignment with increased tensile strength, encourages fibroblast
In our study, only 2 of the 9 SF-36 item scores improved significantly activity, and prevents adhesions between the healing tendon and
pain and functional status. The amount of mprovement in these adjacent tissue.
2 categories was quite low. It is difficult to judge if this moderate
increase represents a "practical" improvement from the patient's point
The SF-36 is not a disease-specific instrument; therefore, it is not
capable of detecting specific symptoms and limitations in patients
with Achilles tendinitis. Another widely used instrument for the
assessment of hindfoot disorders is the AOFAS score. With this score,
the eccentric training group and the AirHeel group improved but there
was no synergistic effect when both treatments were combined. The
same result was obtained with the VAS assessment of pain.
Although we could not replicate the very good results after eccentric
training found in other studies, the results of this study support
findings of previous studies regarding the effect of the eccentric
training. Several previous studies could demonstrate that eccentric
exercises improve pain and function in cases of chronic midportion
tendinopathy of the Achilles tendon. The concept of eccentric training
as treatment for chronic Achilles tendinopathy was introduced by
Recent studies have shown that an effect on neovascularization
could be responsible for the good result with eccentric training in
chronic midportion Achilles tendinopathy. In a clinical study, Ohberg
et al showed that in the majority of tendons with a good result after
eccentric training, the neovessels that had been demonstrated in
before treatment had disappeared at follow-up. In the
5 tendons with a poor result of treatment, there was remaining
neovascularization. Several studies have shown that tendons with
chronic tendinopathy had significantly more blood vessels than
normal tendons. The occurrence of neovascularization in the area
with tendon changes, demonstrated with color Doppler examination
simultaneously with ultrasonography, has been shown to possibly
be correlated with pain in chronic midportion Achilles tendinopathy.
From another study on biopsies from Achilles tendinopathy tissue,
we know that there are nerve structures in the proximity of the
vascular wall; consequently, the area with neovascularization should
be considered as an area with neovessels and accompanying nerves. Alfredson et al used microdialysis and could show that
concentrations of the neurotransmitter glutamate were significantly
higher in tendons with chronic painful tendinopathy compared with
pain-free (normal) Achilles tendons. In recent years, the importance
of glutamate as a mediator of pain in the central nervous system has
In contrast to eccentric exercises, the explanation for the effect of
the AirHeel brace demonstrated in this study is largely unknown.
We speculate that the cyclic massage effect of this brace supports
transport of metabolites such as glutamate or lactate via the venous
plexus of the inflamed paratenon. A second explanation could be that
the brace loosens adhesions built between the tendon, paratenon,
and the surrounding tissue. Further experimental studies are needed
to evaluate the cause of the positive effect of the AirHeel brace on
chronic Achilles tendinopathy as documented in this prospective
randomized controlled trial. To our knowledge, there are no clinical
studies about the AirHeel brace for chronic Achilles tendinopathy in
the literature. Kavros et al evaluated the efficacy of the AirHeel brace
in the treatment of plantar fasciitis. In this study, the AirHeel group
demonstrated significant improvement in pain.
Poor methodology is one suggested reason for the weak evidence
for treatment of tendinopathy. Therefore, care was taken that the
methodologic suggestions proposed by Tallon et al were met in
the present study. The complete study design was approved by
the Ethical Committee of the medical faculty of our University as a
prospective randomized controlled trial. Because placebo treatment
was regarded as unethical, we chose the well-established eccentric
training as a control group. A power analysis revealed that a minimum
of 30 patients were needed in each group to detect a medium effect
of the treatment modality. The treatment period was documented
in detail for every patient to control for treatment adherence and
compliance. The outcome assessments (AOFAS score, SF-36, VAS for
pain) were in a written form with minimal investigator assistance.
Because the literature provides no outcome instruments that have
been validated for Achilles tendinopathy, we decided to use as many
different outcome instruments as possible. All outcome instruments
were used in previous studies about Achilles tendon or hindfoot
disorders. Ultrasonography was performed to confirm the diagnosis of
midportion tendinopathy and to diagnose associated paratenonitis.
However, thickening of the tendon and structural changes were
not inclusion criteria. All patients with pain from the insertion of
the tendon were excluded from the study because previous studies
have shown that pain at this location has a different origin (Haglund
deformity, insertional tendinopathy) and does not respond well to
method of identifying abnormalities such as increased tendon
thickness, hypoechoic areas, and irregular structure. Therefore, we
decided to use ultrasonography to study tendon thickness and tendon
structure before and after treatment with eccentric training. None of
the treatment strategies tested in the present study could influence
these structural changes. The short follow-up period for the ultrasound
examination might be an explanation for this finding. Fahlstrom et
al could show that tendon width had decreased significantly years
after eccentric calf muscle training. Furthermore, before treatment
all patients had hypoechoic areas and an irregular tendon structure,
but at follow-up the tendon structure was normal (no hypoechoic
areas and regular structure) in 19 of the 26 tendons. Fahlstrom et
al speculated that the eccentric training regimen might induce a
response that normalizes the concentrations of glycosaminoglycans
and possibly enables normalization of the fiber arrangement, resulting
in decreased tendon thickness. In this study, in most patients the pain
in the tendon diminished and then disappeared during the 12-week
treatment period. It is conceivable that the pain recedes during the
early part of a possible remodeling phase, but normalization of tendon
thickness and structure may be more time consuming.
When no differences in effect can be found between treatment
groups, one should always consider a type II error. However, a power
analysis has shown that a minimum of 30 patients was needed to
detect differences between eccentric training and no treatment.
Another limitation is that from the present study, one cannot exclude
the effects of placebo, similar in all 3 groups. However, a placebo group
was not approved by our local ethics committee. Theoretically, there
could be a risk for contamination between groups in randomized
study. However, all patients of the heel brace group were instructed
not to perform any kind of strengthening exercises on
The limitations of the methods used in the present study inhibits
our ability to draw any definite conclusions. This study could not
demonstrate any significant differences between treatment with
the AirHeel brace and an eccentric training program in patients with
chronic Achilles tendon pain. No synergistic effects could be found
when both treatment strategies were combined. Further research is needed to evaluate whether the AirHeel brace
is an alternative treatment option for patients with chronic Achilles
The AirHeel brace was provided by Aircast Europe, Neubeuern, Germany.
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