Impingement

Synonyms

Subacromial constriction syndrome, shoulder bottleneck syndrome, shoulder constriction, shoulder bottleneck - syndrome

Definition

Under impingement syndrome, one means a constriction of the gliding space for tendons of the rotator cuff musculature and of the shoulder cap bursa with impulses or pressure damage of these structures between the head of the humerus and the shoulder cap when the arm is moved.

Age

The malady occurs typically in middle age, and most frequently among fifty-year olds.

Sexual distribution

The sexual distribution is approximately 50: 50.

Frequency

One assumes that approximately 10% of the population suffers movement limitations that are caused by pain.

Summary

Impingement syndrome deals with a malady, which affects the interior shoulder tendons (rotator cuffs), especially the Supraspinatus tendons. The reason for the malady is a natural (physiological) bottleneck in the region of the shoulder muscles that rotate the arm, the so-called rotator cuff, and of the bursa that lies above them (= Bursa subacromialis). This region is also designated as the shoulder cap. Pain arises as a result of squeezing the tendons and bursa between the upper arm head and the shoulder cap, which lies above it (Acromion and Ligamentum acromio-claviculare), e.g. when moving the head of the upper arm.

The following diagrams demonstrate parts of the complex movement mechanism in the shoulder region.

In the figure to the right, the arm hangs down sideways. In this position, one can determine the distance between the head of the upper arm and the underside of the Acromion. Determinations of the distances are usually made by means of an X-ray image or via magnetic resonance imaging (MRI, NMR). Within the scope of the determination, one designates the shoulder cap as the acromio-humeral distance, as the distance between the head of the upper arm and the shoulder cap, which should ideally be greater than 10 mm. This 10 mm distance is regarded to be the minimal dimension, which should prevent squeezing soft tissues which lie between, i.e. the rotator cuffs and Bursa subacromialis (bursa of the shoulder cap). If this region is smaller, then the probability of an impingement – syndrome is increased.

Raising the arm sideways (= abduction) occurs, e.g. by contracting the rotator cuff, especially via the Musculus supraspinatus. Within the scope of this movement, the head of the upper arm slides beneath the shoulder cap, with the result that the rotator cuff itself as well as the bursa (Bursa subacromialis) slide under the shoulder cap. This procedure is normal (physiological), so that sufficient space is normally available for these movements. However, if too little space is available, for any reason, the so-called impingement – syndrome occurs, the subacromial bottleneck syndrome. The problem, thereby, is that injuries can arise in the long run, due to the continuous rasping of the rotator cuffs on the shoulder cap, which can cause a complete rupture of the same in the final state.

According to the cause and localization of the impingement, one differentiates various forms in the region of the shoulder, which however require a more detailed knowledge of the shoulder anatomy.

Causes

Three components that participate in creating the impingement syndrome are presented in a simplified version. They are:

1. The head of the upper arm
2. The shoulder cap (consisting of the Acromion and Ligamentum acromio-acromiale)
3. The rotator cuffs with Bursa subacromialis

Modifications of one or a combination of modifications of several of these components can be the possible causes for the creation of an impingement syndrome. Pertinent thereto:

• Preponderance of the muscle group that elevates the upper arm and which thus causes the head of the upper arm to be raised.
• Fracture of the upper arm head that has healed improperly
• Overburden and/ or thickening of tendons on the rotator cuff that are caused by training (bodybuilding)
• Increase in volume of the tendons and of the bursa caused by chronic inflammations
• Calcium deposits in the tendons (Tendinosis calcarea)
• Bony projections on the undersurface of the Acromion
• Arthrosis of the shoulder joint (AC-joint)
• Adverse variable forms of the Acromion, which deviate from the normal, for example with a point that is directed downward (flat Acromion)

Diagnosis

Patients normally suffer under pain that depends on movement, which – provided that the bursa furthermore demonstrates an inflammation, can also occur at rest and during the night. If pressure is exerted on the anterior joint gap in the region of the Tuberculum majus and additional examination points, then so-called pressure pains occur. Also an elevation of the arm against resistance causes pain as well as raising the arm sideways, e.g. in the range between 60 to 120 °. One designates this as the so-called „painful arc“. Furthermore, additional provocation tests exist in the doctor’s physical examination, which purposely constrict the rotator cuffs under the shoulder cap, and thus provoke symptoms, which occur with an impingement-syndrome.

A decrease in pain can be caused by injecting a local anesthetic beneath the shoulder cap (Neer-Test). In the event that the arm still cannot be raised, despite pain relief or reduced pain, an injury in the region of the shoulder tendons (rotator cuffs) must be taken into consideration. Function texts also exist for various muscle and tendon components of the rotator cuffs, which indicate an injury (rupture) to the physician.

In order to be able to estimate the extent of the malady, the bony structure of the shoulder joint will be examined by means of X-ray control. The form of the shoulder cap and the position of the upper arm head, or eventual calcification of the rotator cuffs (Tendinosis calcarea), which indicate a special type of constriction, must be taken into consideration thereby. Ultrasonic examination or nuclear magnetic resonance imaging is suitable as an additional imaging procedure. By means of an ultrasonic examination, it is possible to observe the condition of the rotator cuffs and the size and constitution of the bursa without side-effects. An advantage with the ultrasonic examination is the possibility to observe the shoulder during movement of the arm, which is not the case with X-ray or magnetic resonance imaging.

Therapy

Different possibilities exist to have a therapeutic effect on the malady. Thereby, the therapy is always adapted to the individual illness condition.

Conservative therapy

Different measures belong to conservative therapies, which can be chosen according to the progress of the illness.

Avoidance of moving the upper arm head

If sporting activities are being undertaken, it is recommended at first to reduce exercises in the shoulder region. As soon as symptoms have been reduced and the condition has been improved, a targeted, sport-specific technique can be effectively implemented in combination with strengthening of the muscles in the region of the rotator cuff on a long-term basis. (Refer to: 4. Build-up of the musculature)

Pain and anti-inflammatory therapy

For example, by taking suitable medicines, with Voltaren ®, Celebrex ®, Ibuprofen ®, Naproxen® etc. So-called subacromial infiltrations also belong to pain therapy. Hereby, a mixture from a local anesthetic and cortisone will be injected under the Acromion (shoulder cap). Since these measures can only provide an intermediate success, and the possibility that damage to the rotator cuff cannot be excluded, the infiltration should only be performed a maximum of three times.

Physical therapy

Physical therapeutic exercises, such as for example a manual pulling (traction) on the arm or extension exercises, which cause the head of the upper arm to be pulled down away from the shoulder cap, enable an extension of the shoulder cap; upon regular application, they also enable an extension of the shortened soft tissue.

Build-up of the musculature

Upon developing the musculature, a strengthening of the so-called rotators is the primary goal. This muscle group is responsible for restraining and stabilizing the upper arm. Nevertheless, it must be observed that one at first only exercises those muscles, which re-extend the distance between the upper arm head and the lower side of the Acromion. For this reason, training of the delta muscle (Musculus deltoideus) is avoided initially.

Radiation therapy

A low-dose radiation therapy represents a quite effective means for a conservative therapy for approximately 70 % of all illnesses. Thereby, it could be established that the effectiveness of the treatment increases in accordance with the earliest onset of the treatment in the course of illness. Low-dosage means that, in comparison to radiation therapy for cancer patients, for whom a total dosage is reached in the range from 50 to 70 Gy, the dosage of the conservative impingement – therapy is set in the range of 3 to 6 Gy.

Acupuncture

In addition, pains can also be reduced through acupuncture. However, within the scope of this form of therapy, one must differentiate between acute and chronic pain. For acute pains, the treatment should occur more frequently than for chronic illnesses. Thereby, daily sessions are possible in acute cases, while therapy sessions of once or twice a week should suffice for chronic cases. In the long run, approximately 10 to 20 sessions are required to reduce pain.

Electrotherapy

Under diadynamic current, one is dealing with stimulating current, with shares of direct and impulse current. One differentiates in this area between five different qualities of current, which can be implemented individually or combined. With respect to subacute or chronic stages of the impingement – syndromes, one attempts to achieve an analgesic effect or a muscle relaxation (detonization) by means of these diadynamic currents.

Cryotherapy

Within the scope of cyrotherapy, ice is applied for therapeutic purposes. Through different application forms and variations in the range of residence times, one attempts to support the body’s own self-healing processes. For acute pains, an ice therapy can be implemented several times a day. For self-application, a package of frozen peas is suitable, for example, because the peas can be well-adapted to the shoulder contours and thus guarantee a uniform application of the cooling. However, if the patient is suffering from a chronic malady, then warmth should be applied. Here, the treating physician can offer therapeutic support.

Surgical therapy

Different indications are given for a surgical therapy. The treating physician decides between stage I and II of the illness, for which the treatment must be classified as unsuccessful after a half- to one-year of conservative types of therapy, and a tendon lesion through the so-called Acromion process, as well as stage III, the stage of an incomplete tendon rupture with unsuccessful, conservative therapy. In the previously-mentioned cases, surgical therapy can be taken into consideration as an additional possibility. The surgical operation for a subacromial constriction syndrome is designated as subacromial decompression (decompression = extension).

With regard to this decompression, different methodical approaches exist – according to the underlying causes – for an operation. Thereby the goal is to achieve that the rotator cuffs are no longer squeezed between the head and the shoulder cap and that they will not be torn under any circumstances.

In the surgical area, one differentiates between:

• The Acromion sculpture according to Neer (= Défilé – Extension)

In principle, one means hereby the extension of the subacromial space through a decompression of the Supraspinatus tendon. Thereby, the rotator cuff that lies beneath the shoulder cap should receive more space for movement. In order to achieve this, a small portion of bone is removed from the lower part of the Acromion. The Acromion sculpture is usually performed arthroscopically. An Acromion sculpture can be applied for a rotator cuff lesion as well as for an intact rotator cuff. Further below, you can find further explanations about this surgical operation.

• A corrective – operation, which can be required after a bone fracture on the head of the upper arm that has healed improperly.
• A surgical removal of calcium deposits (calcium extirpation) on the rotator cuffs (Tendinitis calcarea).
• A bursa removal. Thereby, a thickened and inflamed bursa (Bursitis subacromialis), which is located on the rotator cuff, is entirely or partially removed. This usually occurs in connection with an Acromio sculpture (see above).

In the subsequent section, the subacromial decompression will be treated: The shoulder cap consists of two parts, the posterior bony section, called the Acromion, and the anterior ligament section, the Ligamentum coraco-acromiale. The rotator cuff moves – as one can recognize on the basis of the figure – through a tunnel. This tunnel is too narrow with a subacromial bottleneck syndrome and it must be expanded. The distance between the head of the upper arm and the lower surface of the Acromion is designated medically as the acromio–humeral distance. In the normal case, a minimal distance of 10 mm must be guaranteed. One achieves an enlargement of the tunnel by removing the "bony nose" on the Acromion that is directed downwards. Although previously one still routinely removed the anterior ligament portion of the shoulder cap, today one dispenses with this to a great extent. If the so-called „abutment“, of the anterior ligament section is completely missing, the head of the upper arm can still slide upward and the situation can sometimes become worse.

Different surgical procedures of the subacromial decompression

As already briefly mentioned above, the surgical operation can be performed in an arthroscopic technique (arthroscopic subacromial decompression, also called ASD) as well as in an open technique (OSD = open subacromial decompression) with a larger incision.

The arthroscopic subacromial decompression - ASD – occurs within the scope of a simultaneously performed endoscopy of the shoulder joint (arthroscopy). Normally, one requires merely 2 - 3 small skin incisions of approximately 1 cm length, in which special instruments and an endoscope can be inserted. With a shaver, a type of rotating lathe, a portion of the lower Acromion surface is removed.

The open subacromial decompression- OSD occurs via a skin incision of approximately 5 cm. With the aid of a sharp chisel, a portion of the lower, anterior side of the Acromion will also be removed. This surgical operation can become necessary under certain circumstances with adverse, anatomical conditions, since an arthroscopic operation is usually but not always possible or recommended.

If one has the possibility to decide between both surgical forms, the ASD should usually be taken in preference to the OSD. The advantage of the ASD lies especially in the essentially more pleasant course of recovery after the operation. However, it must be mentioned that the results of ASD and OSD are of equal value in the medium term and they must be regarded as having no appreciable differences.

Aftercare

Directly after the operation, cooling measures will be instituted, in order to reduce pain, and especially to minimize swelling of soft tissues. As needed, pain-relieving and swelling-reducing medication can be individually prescribed. In order to rapidly restore movement to the arm, as of the first day post operative, physical therapy aftercare will be prescribed. This consists in part of so-called passive movements, which the physical therapist performs alone. But otherwise – after a certain preliminary time – active movements will be performed, which the patient does by himself under direction of the physical therapist. Furthermore, aftercare is recommended with the aid of a motorized movement splint (= CMP, continuous passive motion). Thereby, while the patient sits in a chair, the shoulder is laid in an electrically-driven splint and moved. Usually, patients regard the treatment with CMP as enjoyable. The movement splint can be gradually set and adjusted to individual measures. Intensive movement exercises of the shoulder are necessary, in order to retain mobility of the shoulder joint. The shoulder is a joint, which tends to become stiff rapidly, if no movement occurs. Therefore, a sufficient post-operative pain-relieving therapy is of special significance. The patient must be able to exercise. .