Swimmer's Shoulder (Impingement Syndrome)

Introduction:

Swimmer's shoulder, a term commonly used to describe shoulder impingement syndrome in swimmers, is a prevalent condition among athletes who engage in repetitive overhead movements. The mechanics of swimming, especially the freestyle stroke, impose repetitive stress on the rotator cuff tendons, leading to subacromial impingement. Understanding the biomechanics, pathophysiology, and treatment of this condition is essential for Clinicians, particularly those involved in sports medicine.

Anatomy and Biomechanics of the Shoulder in Swimmers:

Key Anatomical Structures Involved:

Acromion: The morphology of the acromion (Type I, II, III) plays a critical role in the development of impingement. A Type III (hooked) acromion significantly narrows the subacromial space, predisposing individuals to impingement.
Rotator Cuff Tendons: The supraspinatus tendon is most commonly affected due to its proximity to the acromion. The infraspinatus and teres minor also contribute to shoulder stabilization during swimming.
Subacromial Bursa: This fluid-filled sac cushions the tendons of the rotator cuff. Chronic irritation leads to subacromial bursitis, which can exacerbate impingement.
Glenohumeral Joint: The joint’s inherent instability in swimmers is a major contributing factor, as excessive internal rotation and abduction during swimming strokes increase the risk of impingement.

Swimming Biomechanics and Pathophysiology:

The repetitive, high-volume nature of swimming strokes, particularly freestyle, butterfly, and backstroke, places the shoulder at risk for mechanical impingement. During the freestyle stroke, the shoulder goes through the following phases:

Entry Phase: The shoulder is in abduction and internal rotation, placing the supraspinatus tendon in a position vulnerable to impingement against the acromion.
Pull-Through Phase: As the swimmer pulls their arm through the water, the shoulder experiences significant internal rotation and adduction, further narrowing the subacromial space.
Recovery Phase: In this phase, the arm is brought overhead, which can aggravate any existing inflammation or impingement due to the high degree of shoulder abduction and internal rotation.

The primary pathophysiological mechanism in swimmer's shoulder is the repetitive overhead movement leading to subacromial impingement, characterized by compression of the rotator cuff tendons (primarily the supraspinatus) and the subacromial bursa beneath the acromion during shoulder elevation.

Clinical Presentation in Swimmers:

Patients typically present with a combination of the following:

Anterior and Lateral Shoulder Pain: Often exacerbated by overhead activities such as swimming. The pain is typically localized to the anterior and lateral aspects of the shoulder.
Weakness: Especially in abduction and external rotation, which may result in reduced performance and an inability to complete training sessions.
Night Pain: Commonly reported, especially when lying on the affected shoulder.
Progressive Symptoms: In the early stages, swimmers may report pain only after prolonged swimming sessions. As the condition progresses, pain may occur during and after activity and, in severe cases, at rest.

Physical Examination:

A thorough physical examination should include tests to provoke impingement and assess the functional status of the shoulder:

Neer’s Test: Forward flexion of the internally rotated arm while stabilizing the scapula provokes pain, indicating subacromial impingement.
Hawkins-Kennedy Test: Forward flexion of the shoulder to 90 degrees followed by forced internal rotation elicits pain, indicating compression of the supraspinatus tendon against the coracoacromial arch.
Painful Arc Test: Pain is typically most pronounced between 60 to 120 degrees of abduction, which is the range where the supraspinatus tendon is most compressed.
Empty Can Test: Weakness and pain in the abduction of the arm with internal rotation (thumb pointing down) suggest supraspinatus involvement.

Diagnostic Workup:

In athletes, particularly swimmers, early and accurate diagnosis is critical to avoid chronic changes in the shoulder, such as tendon degeneration or tears.

Plain Radiographs:
- AP View: Useful for assessing acromial morphology, humeral head position, and the presence of osteophytes at the acromioclavicular joint.
- Outlet (Supraspinatus) View: Evaluates the size of the subacromial space and the presence of bony spurs. A reduced subacromial space (<7 mm) suggests impingement or a rotator cuff tear.
- Axillary View: Assesses glenohumeral instability, which can exacerbate impingement.
Ultrasound: An effective, dynamic tool to assess rotator cuff integrity, subacromial bursitis, and the presence of impingement. In dynamic ultrasound, impingement can be visualized during arm abduction.
Magnetic Resonance Imaging (MRI):
- MRI without contrast is the gold standard for evaluating soft tissue structures. It can identify rotator cuff tendinopathy, partial- or full-thickness tears, subacromial bursitis, and labral pathology.
- In swimmers, MRI often reveals early signs of rotator cuff tendinosis before full-thickness tears develop.
MR Arthrogram: In cases of suspected labral tears, particularly in swimmers with concurrent glenohumeral instability, an MR arthrogram may be useful.

Classification of Impingement Syndrome (Neer Classification):

Stage I (Edema and Hemorrhage): Seen in younger athletes (<25 years), often reversible with rest and physical therapy. There is no structural damage to the rotator cuff.
Stage II (Fibrosis and Tendinitis): Aged 25-40 years, characterized by chronic inflammation and fibrosis of the rotator cuff tendons. Symptoms are more persistent, and conservative management is less effective.
Stage III (Rotator Cuff Tears and Bony Changes): Typically seen in older athletes (>40 years), associated with partial or full-thickness tears, osteophyte formation, and irreversible damage. Surgical intervention is often required.

Management of Swimmer’s Shoulder:

Non-Surgical (Conservative) Management:

Most swimmers respond well to a comprehensive rehabilitation program that includes activity modification, physical therapy, and pharmacologic management.

Activity Modification:
- Swimmers should temporarily reduce or modify their training regimen to avoid repetitive overhead movements. Stroke technique should be evaluated to correct biomechanical errors.
- Freestyle swimmers should work on improving high elbow recovery and reducing early pull-through to minimize excessive internal rotation and shoulder strain.
Physical Therapy:
- Phase I (Acute Phase): Focus on rest, ice, and NSAIDs for pain control. The goal is to reduce inflammation.
- Phase II (Strengthening Phase): Incorporate exercises that strengthen the rotator cuff muscles, particularly the external rotators (infraspinatus, teres minor) and scapular stabilizers (serratus anterior, trapezius). Strengthening the lower trapezius and serratus anterior helps improve scapular mechanics, which is essential for preventing impingement.
- Phase III (Functional Phase): Emphasize sport-specific training with a focus on improving shoulder endurance and dynamic stability. Plyometric exercises and proprioceptive training should be introduced during this phase to simulate swimming movements.
Pharmacologic Treatment:
- NSAIDs (e.g., ibuprofen, naproxen) can be used for anti-inflammatory effects. Care should be taken to avoid long-term use due to gastrointestinal and renal side effects.
- Corticosteroid Injections may be indicated in patients with persistent pain despite physical therapy. Injections are usually administered into the subacromial space. Repeated injections should be avoided to prevent tendon degeneration and weakening.
Correction of Swimming Technique:
- Focus on high elbow recovery to reduce shoulder impingement.
- Strengthening the core and optimizing hip rotation during the freestyle stroke can reduce the strain on the shoulder, as excessive reliance on shoulder movement leads to overuse injuries.

Surgical Management:

If non-surgical measures fail after 6 months, surgical intervention may be considered. Surgery is typically reserved for those with significant structural abnormalities or persistent symptoms despite appropriate rehabilitation.

Arthroscopic Subacromial Decompression (ASD):
- Indications: ASD is indicated in patients with persistent impingement due to mechanical narrowing of the subacromial space. This procedure involves removal of inflamed subacromial bursa and partial acromioplasty to flatten the acromion and increase the subacromial space.
- Results: Studies have shown good outcomes, with the majority of swimmers returning to their pre-injury levels after appropriate rehabilitation. However, early rehabilitation is crucial to avoid shoulder stiffness postoperatively.
Rotator Cuff Repair:
- In cases of full-thickness rotator cuff tears, arthroscopic repair is indicated. Swimmers with rotator cuff tears may present with chronic shoulder pain, weakness, and reduced range of motion.
- Postoperative rehabilitation focuses on restoring rotator cuff strength, improving scapular control, and gradually returning to swimming.

Prognosis and Return to Swimming:

Most swimmers with impingement syndrome respond well to conservative treatment. With proper rehabilitation and technique correction, swimmers can return to competitive levels of training.
Surgical outcomes are generally favorable, with most athletes returning to their sport within 3-6 months after subacromial decompression or rotator cuff repair.
Postoperative rehabilitation is crucial, and a gradual return-to-swimming protocol should be followed to ensure the shoulder is fully prepared for the demands of competitive swimming.

Conclusion:

Swimmer’s shoulder, a specific form of impingement syndrome, requires a comprehensive understanding of the biomechanics, pathophysiology, and appropriate treatment protocols. Clinicians managing this condition must emphasize early diagnosis, conservative management through activity modification and physical therapy, and, if necessary, surgical intervention. Preventative strategies, such as optimizing swimming technique and strengthening the shoulder stabilizers, are key to reducing the risk of recurrence in swimmers.