Rotator Cuff Disease and Shoulder Impingement Syndrome:
Consensus and Controversies

Chan KM, Tong CWC

1. Introduction
Shoulder impingement syndrome was originally coined by Neer in 1972 when he described the condition as compression of the supraspinatus tendon against the anterior edge of the acromion, the coracoacromial ligament and at times a projecting spur localised to the acromioclavicular joint.1 This chronic repetitive syndrome characterised by constant attrition and microtrauma causes a progressive inflammatory process and a subsequent degenerative process within the rotator cuff which leads to the clinical syndrome of pain and weakness of the shoulder. The term shoulder impingement syndrome has largely replaced what used to be called 'painful arc syndrome'.

There has been an increase in knowledge of the basic pathology of rotator cuff disease. Beginning with repeated tendon strain and oedema, cuff pathology can progress to inflammation, fibrosis, and with time, partial or full thickness tears. There is now a general consensus that rotator cuff disease or dysfunction is a continuum which ultimately leads to failure of the cuff to fulfil its physiological role. This point of 'failure' may occur much earlier before the tendon has reached a point of tear, either partial or complete as revealed clinically.

With the advancement of imaging techniques such as ultrasound and MRI, clinicians are better informed of the pathological processes involved and the integrity of the rotator cuff. A more rational approach to the management of the condition is now possible in an attempt to bring the patient back to his/her previous function. This review article attempts to look at the pathogenesis, clinical approach and the management of rotator cuff disease/shoulder impingement syndrome highlighting areas of consensus and also issues of controversies.

2. Pathogenesis of rotator cuff dysfunction
There is a consensus that the causes of rotator cuff failure may reside in the tendon itself (intrinsic causes) or may reside in the structures surrounding the cuff (extrinsic causes).

2a. Intrinsic causes

Degenerative cuff failure
This constitutes the commonest cause of cuff failure and usually occurs in the older individual.2 Degeneration of the cuff may later result in partial tears which may progress to complete tears. The precise cause of degenerative cuff tear is unknown. One possible theory relates to the 'critical vascular zone' of the cuff tendon where the blood supply is precarious, and relative ischaemia leads to degenerative changes.

Traumatic cuff failure
This may occur when the upper limb is subject to a violent force and the rotator cuff sustains a traumatic tear. In the younger individual where the tendinous part of the cuff-bone complex is stronger than the bony part, the tendons may avulse with a piece of bone.3

Reactive cuff failure
Calcific rotator cuff tendinitis is an example of reactive cuff failure. The calcifying mass inside the tendon may give rise to a swelling which leads to impingement under the subacromial arch, hence resulting in cuff failure.

2b. Extrinsic causes

Bony factors
Bigliani classified the acromion into three categories.4 Type III acromion is where the edge of the acromion is hooked and therefore may impinge on the rotator cuff on elevation of the arm. Osteophytes under the acromioclavicular joint reduces the subacromial space and can also lead to cuff impingement and therefore failure.

Soft tissue factors
Examples include subacromial bursitis and thickened coracoacromial ligament which can both lead to impingement of the cuff and subsequent cuff failure.

Controversies
The precise interplay between the intrinsic and extrinsic factors in the pathogenesis of rotator cuff failure is not entirely clear. In particular, it is not always clear whether the bony factor is the primary pathology leading to attrition and later tear of the rotator cuff or whether the degeneration is the primary factor leading to cuff tear.

3. Clinical approach to rotator cuff disease and shoulder impingement syndrome
A consensus has been reached of the importance to be aware of the numerous other causes of shoulder pain besides rotator cuff disease when evaluating the painful shoulder.5 These include:

  1. shoulder instability
  2. glenohumeral osteoarthritis
  3. acromioclavicular joint OA
  4. nerve entrapment syndromes
  5. inflammatory synovial disease etc.

A thorough history, physical examination and appropriate investigations should differentiate between these different entities. This distinction is vital as each has a different plan of management.

Primary instability leading to secondary impingement - a consensus
The concept of primary instability of the shoulder giving rise to secondary impingement has recently been emphasised. This is especially relevant in the young athlete where primary instability is relatively common.6 It is important to make this differentiation because the primary instability has to be tackled rather than the secondary impingement. There have been instances where a surgical procedure has been done to target rotator cuff impingement where the primary problem is shoulder instability. The results of these surgeries were invariably bad as the underlying pathology was not tackled. It is therefore important when examining a shoulder in the context of impingement to look for signs of joint laxity and instability.

The Consensus
A systematic clinical assessment is mandatory.

Clinical history
Impingement tears of the rotator cuff are common after 50 years of age. Many of these patients have no prior history of trauma, and an attrition defect develops insidiously. In this setting, the rotator cuff tear is brought to the attention of the physician when the patient presents with a long standing history of intermittent shoulder pain that has become progressively more symptomatic. At this juncture, pain is usually constant, worse at night and with overhead activities, and only mildly improved with anti-inflammatory agents. The pain is commonly referred to the base of the neck and upper arm.

Young patients and athletes should be questioned with regard to their pain as it relates to activity and sport. These younger patients are more likely to have rotator cuff dysfunction and pain related to overuse, eccentric overload, subtle instability, and focused questions can aid in determining the association of any of these factors.

In addition to pain, patients with rotator cuff dysfunction also commonly complain of weakness if the arm, subacromial popping or grinding, and loss of motion.

Physical Examination
From a thorough history, a general impression should be established before proceeding with the physical examination. A complete physical examination is essential in the evaluation of any shoulder pain or dysfunction. The shoulder examination should be approached systematically in every patient with inspection, palpation, range of movement, strength testing, neurological assessment, and performance of special shoulder tests. In addition, the physical examination should include a thorough assessment of the cervical spine and the remainder of the upper extremity because patients can often have referred pain from the shoulder.

Special impingement tests have been described by Neer and Hawkins.1,7 In the young patient it is also important to perform shoulder instability tests such as the apprehension test, drawer test as well as the Jobe relocation test as shoulder instability is common in this age group and may be the cause of secondary impingement.

4. Imaging modalities
There is a general consensus that the need for imaging studies for investigating rotator cuff disease should be tailored to the individual patient with specific reference to cost effectiveness and decision making. In this era of escalating health costs, clinicians are constantly reminded to be more selective in the use of imaging modalities. The time honoured approach of using simple non-invasive studies should be done first.

In plain radiography of the shoulder, the scapular AP, axillary and supraspinatus outlet view should be ordered. This should form the basis for investigating the painful shoulder. The use of ultrasound is very much operator dependent on its efficacy therefore varies from centre to centre. MRI is the ideal way of looking at the soft tissue around the shoulder. However, there are still controversies regarding its sensitivity and specificity.

Ultrasound of the shoulder
Ultrasonography is relatively inexpensive and non-invasive and allows an easy comparison with the contralateral shoulder. Partial thickness tears are diagnosed by the absence of normal tissue echoes in the tendon. Shoulder ultrasonography has shown a specificity of 98% and a sensitivity of 91% when compared with operative findings. Differentiation among cuff fibrosis, partial thickness, and small full-thickness tears remain difficult with ultrasonography.

Magnetic resonance imaging
With the evolution of technology for MR imaging, greater application to shoulder disorders has been realised. MR imaging can reveal changes in the rotator cuff resulting from a spectrum of pathologic conditions. The ability to assess various pathologic conditions factors in the evolution of complete rotator cuff tears, ranging from interstitial degeneration to partial tears, distinguishes MR imaging from other modalities, particularly arthrography.

The use of MR imaging for the evaluation of the shoulder has increased markedly in the past 8 to 10 years. At many centres, it has replaced arthrography for evaluation of the painful shoulder. Advantages of MR imaging over arthrography include its non-invasiveness, multiplanar capability, and excellent soft-tissue contrast.

5. Management of rotator cuff disease and the shoulder impingement syndrome

5.1 Conservative management

Physical therapy
There is general consensus that a comprehensive and supervised rehabilitation programme is the first line of treatment of the shoulder impingement syndrome. The rehabilitation programme mainly consists of cuff strengthening exercises and terminal stretching exercises to regain range of motion.

Rockwood has emphasised a physician led rehabilitation programme where the physician in charge personally instructs his/her patients the various exercises and tailors the programme specifically to the needs of the patient.8 Each patient is given a home therapy kit that includes elastic bands of different strengths, a pulley set and a metre stick. Additionally, patients receive a fully illustrated booklet with all of the exercises, anatomical drawings, and definitions of related terms and demonstration videotape to remind them how to perform the exercises.

Non steroidal anti-inflammatory drugs
These are often used to decrease the inflammation and pain resulting from the cuff tears.

Intra-articular steroids
In recent years intra-articular steroid injection has slightly fallen out of favour because of the concern that this may weaken and damage the tendon further. However, judicious use of steroid injections is still part of the armamentarium of the shoulder surgeon. The use of a combination "cocktail" injection of 1% lidocaine, 0.25% marcaine, and long-acting corticosteroid appears to be a popular choice.9 Most surgeons agree to limit steroids injections to three subacromial injections within a period of 12 months.

Controversies in conservative management
The main controversy lies in the exact duration of conservative management that should be attempted before surgical treatment is contemplated. Various authors have proposed various times from 3 months to 18 months. Most surgeons tend to observe for a 6 month period. It appears that for patients older than 50, a longer period of conservative treatment is warrented. In the younger and more active individual with acute trauma, surgical intervention may be considered at an earlier time.

5.2 Operative treatment

The two structures that need to be tackled in the surgical treatment of rotator cuff disease / shoulder impingement syndrome are the acromion and the rotator cuff itself.

Surgery to the acromion

Acromioplasty- decompression
Neer was the first to popularise acromioplasty for the treatment of shoulder impingement, emphasising that resecting the antero-inferior portion of the acromion will increase the volume of the subacromial space and therefore decrease the degree of impingement of the supraspinatus tendon under the acromion.1 Open acromioplasty proved to be a very successful operation and relieved the pain in many patients with impingement syndrome.

Controversies surrounding acromioplasty
Controversy lies in whether acromioplasty should be done open or arthroscopically. The proponents for arthroscopic subacromial decompression argue that the deltoid is much less traumatised and therefore shoulder strength will be better preserved post-operatively.10 In addition there is a smaller scar, less wound pain and a shorter hospital stay. However, shoulder arthroscopy is a difficult procedure with a steep learning curve whereas open acromioplasty is a relatively simple procedure which is well tested to be effective for the general orthopaedic surgeon.

Surgery to the rotator cuff

Much controversy has surrounded the best treatment for rotator cuff tears. The two main issues which have been argued upon are:

  1. Should the rotator cuff tears be debrided or repaired?
  2. Should these procedures be done open or arthroscopically?

The issue is further complicated because controversy exists regarding the best treatment for partial tears, full thickness tears and massive tears of the rotator cuff.

Partial tears
Partial tears may be on the bursal side or the articular side of the rotator cuff. Debridement of these tears is thought to promote healing of the tendon. However, recent studies by Kumagai have indicated that debridement may not stimulate the reparative process as was originally postulated, and their group were sceptical of the recovery of incompletely torn tendons to a load bearing functional structure after debridement of the cuff.11 Kumagai recommends re-establishing a secure tendon-bone junction, consisting of a considerably healthy edge of the torn cuff and a bony trough as a source of multipotential mesenchymal cells.

Full thickness tears
There is consensus that full thickness tears need to be repaired. The controversy lies in whether these should be done arthroscopically or via a mini-open repair. It appears that a combination of arthroscopic subacromial decompression followed by a portal-extension type of mini-open cuff repair is gaining much popularity by most shoulder surgeons. The arthroscopic cuff repair is technically highly demanding and should be done by experienced shoulder arthroscopists. The efficacy of suture anchors also need to be further refined to achieve the best holding capacity in the somewhat osteoporotic bone. Massive tears The main controversy lies in whether these should be debrided or repaired. Massive tears are technically difficult to be repaired because of the sizeable defect. Various techniques have been developed to mobilise and reconstruct these tendon defects. These include the mobilisation of existing tendons, the transfer of tendons, the implantation of fascia, allografts and the placement of synthetic material.

As most of the massive tears occur in the older individual, there is still considerable controversy whether the 'attempted' repair in the degenerated tendon will hold up to our expectations. The apparent good clinical results may be due to an adequate debridement and decompression rather than restored cuff integrity.

References

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