ESWT IN PAIN THERAPY
Background
Since the early 1980s, extracorporeal sound wave therapy (ESWT) has been used in the
treatment of nephrolithiasis and cholelithiasis with successful outcome in well over 3 million
patients (1). In the field of orthopaedics ESWT was first employed in the therapy of delayed
bone fracture healing and pseudoathroses in 1991 by Valchanou and Michailov (2). Since the
beginning of the 1990's the use of this technique has expanded to include treatment of
enthesopathies - specifically lateral epicondylitis, plantar fasciitis, and rotator cuff tendinitis.
Numerous scientific studies have been carried out in Europe, especially in Germany where
now over 100 clinics use ESWT routinely.
There are several major manufacturers of ESWT equipment - Dornier, Storz, Siemens,
Ossatron. Three of these manufacturers have obtained HPB (Health Protection Branch)
approval for the use of their equipment in Canada. Bayshore has no preferred status with
any manufacturer, thus we can select the best equipment available on the market at a given
time. Bayshore's plan is to establish a network of approx. 18 ESWT clinics from coast to
coast. ESWT treatment is not covered by Provincial health care plans. However, several
private insurers cover the ESWT fee and others are assessing the possibility of ESWT as an
insured service.
ESWT is applied using a system which integrates an electromagnetic sound-wave generator
in a mobile fluoroscopy unit. The sound waves are generated by passing a strong electric
current through a flat coil. This induces a magnetic field, which itself induces another
magnetic field in a magnetic membrane overlying the flat coil. Just as similar poles repel
each other, so do the generated magnetic fields of the membrane and the coil. By means of
an acoustic lens the focus of the sound wave source is just at the centre of the C-arm. The
focal area in which 50% of the maximum energy is reached. It has a length of 50 mm in the
direction of the sound-wave axis and a radius of 3.5 mm in the direction perpendicular to the
sound-wave axis. Once the painful area is situated in the centre of the C-arm, the sound
wave unit is docked on to the foot, lateral epicondyle, or shoulder by means of a water-filled
cylinder. An ultrasound gel is used as a contact medium between the cylinder and the skin.
The energy density of the sound-wave generator can be varied from 0.06 mJ/mm2 to 0.6
mJ/mm2. This is represented by a power setting scale ranging from 1 to 9, in which energy
density has a non-linear increase (3). For pain therapy only power levels of 0.04 to 0.23
mJ/mm2 are used (1). Position and sound wave focus are continuously monitored during the
treatment by a centre cross hair, using the ultrasound screen. Therapy impulses are applied
with an adjustable frequency of up to 4 Hz (4). Depending on the size of the area being
treated, between 1,000 and 3,000 impulses are applied to the therapy zone (1). The sound
wave generator comprises a closed system which as such does not endanger the patients
when used properly. ESWT is performed under ambulatory conditions and one session lasts
25-45 minutes; the patient is usually able to return to work on the following day (1). On
average 3-5 sessions are required per patient and are performed at 3-4 day intervals. A
cooling ointment dressing is applied to the treated area after each session.
Contraindication to ESWT is the presence of any of the following: a polyneuropathy, blood
coagulation disorders, inflammatory systemic disorders, cancer, pregnancy (1). One of the
main advantages of ESWT is the lack of side effects from the treatment (1) (3). Recent
studies showed that there are dose-dependent changes in tendon and paratenon tissue after
ESWT in animal models, however with energy flux densities of 0.28 mJ/mm2 or lower these
changes are minor and quickly reversible (5). Damage to tendons is only observed after the
application of high-energy sound waves, i.e. greater than 0.28 mJ/mm2 (5). In pain therapy
only 0.8-0.23 mJ/mm2 are used. In a study on ESWT in treating calcific rotator cuff
tendinitis, Loew et al had 7% patients develop superficial hematomas of the soft tissue and
25% of patients had skin petechia. All patients in this study had a MRI a few days after
treatment and no changes of the bone, cartilage or tendon structure were detected (6).
Rompe et al, reports no complications in more than 500 patients treated with ESWT for
lateral epicondylitis (7).
The mode of action of ESWT seems to be a symbiosis of three different mechanisms, which
together induce long term analgesic effects:
1. The sound waves destroy part or all the cell membrane, making it impossible for the
nociceptor to build up any generator potential, thus preventing the occurrence of a
pain signal.
2. The sound wave causes the nociceptor to transmit a high impulse frequency. Any
forwarding of these impulses is prevented as described under "gate control theory"
3. The sound wave induces neovasvularization. The sound wave stimulates increased
blood supply to the affected area resulting in reduced inflammation and pain.
4. The sound wave alters the chemical environment surrounding the cell by forming free
radicals which produce analgesic substances (1)
For any musculoskeletal condition, the treatment procedure of choice should be the least
invasive, least expensive and most time efficient. The last two points do not apply to ESWT
and thus ESWT is currently not used as a first line treatment but reserved for refractory
cases of lateral epicondylitis, plantar fasciitis, and rotator cuff tendinitis.
Lateral epicondylitis (LE) - commonly referred to as "tennis elbow" - was described more
than a century ago, but its pathophysiology and treatment are not yet mastered. The
incidence of this condition varies from approximately 1 to 3% in the general population (12).
Lateral epicondylitis involves the wrist extensors at or near their lateral epicondylar origin
and the extensor carpi radialis brevis is most commonly affected. Less commonly involved
muscles are the extensor carpi radialis longus, the extensor digitorum communis, and rarely
the extensor carpi ulnaris. The initial events in LE are microscopic as well as macroscopic
tears in the extensor origin at the lateral epicondyle; this tearing is followed by formation of
granulation tissue and fibrosis (12). Patients usually present with pain in the region of the
lateral elbow which can radiate down the extensor surface of the forearm as far as the wrist,
exacerbated by repetitive activity. An estimated one third of cases interfere with activities of
daily living (12). Many treatments are recommended for LE, such as relative rest, ice,
physiotherapy, oral NSAIDS, forearm supports, injections of corticosteroids, prophylactic
counseling, laser radiation, and acupuncture. Less than 10% of patients fail to improve with
these conservative measures and require surgical intervention (12).
Recently, low dose ESWT has been found to be effective in treating this condition in isolated
cases (7). Rompe et al recently published two studies which looked at patients with
symptoms for more than 12 months. The test group received 3000 impulses of 0.08
mJ/mm2 while the control group received only 30 impulses of the same energy. There were
significant differences between the two groups in follow-up with respect to subjective
outcomes, objective grip strength, and overall outcome, with the test group having much
better outcomes (7) (8). This suggests that ESWT can be an effective treatment for
refractory LE and is not just a placebo effect.
Plantar fasciitis (PF) is the most common diagnosis for pain in the inferior aspect of the heel.
The etiology usually involves inflammation and degeneration of the plantar fascia origin from
the medical tubercle of the calcaneal tuberosity. The plantar fascia is an aponeurosis that
divides distally into several slips and inserts into the proximal phalanges. The PF helps to
maintain the medial longitudinal arch. The pain of plantar fasciitis is classically worse upon
arising in the morning and gradually gets better with the first few steps. PF may or may not
be associated with a calcaneal heel spur. The majority of patients will respond to
conservative measures such as relative rest, massage locally, ice, oral NSAIDS,
corticosteroids injections, physiotherapy, heel cups or pads, custom-made orthodics, laser
treatment, night splints, etc. Occasionally surgical intervention is required for refractory
cases. PF release is one of the more popular methods of surgical management (13). Lowenergy ESWT has been introduced as an alternative to surgery for chronic, refractory cases
of PF. Patients with symptoms for over 12 months were treated with 1000 impulses of
0.08mJ/mm2 in three separate sessions; a control group received 10 impulses of the same
energy. In follow-up there were statistically significant differences between the test group
and controls with respect to rest and night pain and length of pain-free walking (3). After
low-energy ESWT the average time to significant improvement was 3-6 weeks, compared
with 3 months for surgery in one series (3). No side effects were noted from ESWT; the
treatment was considered unpleasant, but not as unpleasant as a local infiltration, by the
patients.
One of the most common causes of pain in the shoulder is rotator cuff tendinitis, with or
without calcification. This is commonly the result of repetitive work or activity where the
supraspinatous tendon impinges on the caudal surface of the coracoacromial arch. The
supraspinatous tendon is the most superior in the RC and inserts onto the greater tubercle; it
keeps the humeral head in the shallow glenoid fossa during shoulder movement.
Impingement results in inflammation. Patients have shoulder pain which is worsened by
overhead activity and by lying on the affected side. In some cases calcification develops
within the tendons as a result of angiofibroblastic change from multiple tendon tension
overload. Conservative therapy is aimed at reversing inflammation in the rotator cuff. This
includes relative rest, ice, oral NSAIDS, physiotherapy, corticosteroid injections, etc. Surgical
intervention in the form of either arthroscopic or open subacromial decompression is
considered if an adequate trial of conservative therapy fails. ESWT has been studied as a
treatment in calcific RCT (6) (10). In one series, disintegration and vanishing of calcification
on radiographs was demonstrated in 60% of patients after 12 weeks (6). Subjectively, 70%
of patients showed clear improvement of their symptoms (6). In another study, 40 patients
with persistent calcifying tendinitis were treated with a single session of 1500 pulses of 0.28
mJ/mm2. With follow-up at 6 and 24 weeks, 62.5% of the patients had partial or complete
disintegration of the deposit, and statistical analysis showed significant improvement both in
subjective and objective criteria (10).
Literature References
1. Haist, J, Steeger von Keitz, D. Shock Wave therapy of Radial and Ulnar Epicondylar
Disorders. Presentation from the Convention of German Orthopaedic Surgeons,
Wiesbaden, Germany, October 12-15, 1994.
2. Rompe, J.D.: Efficient Use of Extracorporeal Shock Waves in Tendinopathies.
electromedica 65 (1979) no.l, p. 20-25
3. Rompe, J.D.,Kullmer, K., Riehle, H.M., Herbsthofer, B., Eckardt, A., Burger, R., Nafe,
B.,
4. *United Medical Systems: Analgesic Therapy of Chronic Pain in Orthopaedics by
ESWT. August 1998.
5. Rompe, J.D., Kirkpatrick, C.J., Kullmer, K., Schwitalle, M., Krischek, 0.: Dose-related
effects of shock waves on rabbit tendo Achillis. J of Bone and Joint Surgery, May
1998, no.3, vol. 80-B,p. 546-52
6. Loew, M., Jurgowski, W.Ueberle, F.: The Effects of Extracorporeal ly Generated HighEnergy Shock Waves on the Clinical, Roentgenological and Histological Progress
ofTendinosis Calcarea of the Shoulder-a Prospective Study. Orthopaedische
Universitaetsklinik, Heidelberg, Germany.
7. Rompe, J.D., Hopf, C., Nafe, B., Burger, R.: Analgesic Effect of Exrracorporeal ShockWave Therapy On Chronic Tennis Elbow. J of Bone and Joint Surgery, March 1996,
no.2, vol.78-B, p.223-7.
8. Rompe, J.D., Hopf, C., Kullmer, K., Heine, J., Burger, R., Nafe, B.: Low-energy
extracorporeal shock-wave therapy for persistent tennis elbow. International
Orthopaedics (SICOT),1996,20_23-27.
9. Rompe, J.D., Hopf, C., Nafe, B., Burger, R.: Low-energy extracorporeal shock wave
therapy for painful heel a prospective controlled single-blind study. Arch Ortop
Trauma Surg, 1996,115:75-79.
10. Rompe, J.D., Rumler, F., Hopf, C., Nafe, B., Heine, J.: Extracorporeal Shock Wave
11. Geoffroy, P., Yaffe, M., Rohan, I.: Diagnosing and treating lateral epicondylitis.
Canadian Family Physician, January 1994, vol.40, p. 73-78
12. Chard, M.D., Hazleman, B.L.: Tennis Elbow - A Reappraisal. Brit J of Rheumatology,
editorial, vol.28,no.3, p. 186-188
13. Schepsis, A. A., Leach, R.E., Gorzycs, J.: Plantar Fasciitis - Etiology, Treatment
Surgical Results, and Review of the Literature. Clinical Orthopaedics and Related
Research, May 1991, no.266, p. 185-196