Shoulder impingement syndrome
Healthy shoulder showing the bursa and tendons anatomy

Definition

A shoulder impingement syndrome, also named subacromial impingement, refers to the painful compression of the tendons of the rotator cuff and the subacromial bursa against the acromion when raising the arm.

Illustration shows inflammation and thickening of the bursa and rotator cuff tendons

Pathology

The inflammation and thickening of the tendons of the rotator cuff and the subacromial bursa cause the narrowing of the joint area between the acromion and the rotator cuff. Due to the restricted space in the joint, moving the shoulder provokes the pinching of the tendons and the bursa. Particularly overhead activity causes irritation and pain in patients with shoulder impingement syndrome. Normally, when elevating the arm the rotator cuff lowers the humeral head, which slides smoothly under the acromion. However, pathological changes of the rotator cuff compromise this shoulder function, whereby the position of the humeral head moves against the acromion instead of being depressed when raising the arm.  

Arm abduction is restricted by the inflamed bursa and tendons, reducing the joint space
Cross section of the shoulder depicting the compression of the bursa (red) above the rotator cuff (white) and below the deltoid muscle

Classification

There are various classification systems for a shoulder impingement syndrome.

Stages of subacromial impingement in athletes - Jobe’s Classification (1989):

Pure impingement with no instability

Primary instability, with capsular and labral injury with secondary impingement, which can be internal or subacromial impingement

Primary instability due to intrinsic ligament laxity with secondary impingement

Pure instability with no impingement.

Grading of impingement changes - Milgrom’s Ultrasound Classification:

Stage 1 Bursal thickness from 1.5 to 2.0 mm

Stage 2 Bursal thickness over 2.0 mm

Stage 3 Partial or full thickness tear of the rotator cuff.

Impingement lesions - Copeland Levy Classification:

This is based on the location of the impingement, either on the acromial or the bursal side.

Acromial side

A0 normal - smooth surface

A1 minor deterioration, haemorrhage or local inflammation

A2 marked scuffing/damage of the undersurface of the acromion and coraco-acromial ligament

A3 exposed bone areas.

Bursal side

B0 normal - smooth surface

B1 minor deterioration, haemorrhage, inflammation

B2 major deterioration of the cuff, partial thickness tear

B3 full thickness tear of the rotator cuff

B4 massive cuff tear.

Left: Distal radius intraarticular, displaced fracture; Middle: Older distal radius fracture with callus formation; Right: Distal radius and ulna fracture, extraarticular and displaced

No 2.

Intra-articular fracture extends to the wrist joint (or articulation)

Extra-articular fracture is located outside of the wrist joint

Open fracture when bone fragments perforate the skin

Comminuted fracture when the bone breaks into multiple fragments

Non-displaced when the anatomical alignment of the bone is maintained or displaced when the bone fragments move apart.

Melone’s classification describes the characteristics of intra-articular fractures of the radius:

i    Stable fracture

ii    Unstable "die-punch"

iii   "Spike" fracture

iv Split fracture

v   Explosion injuries

Acetabular fracture of the pelvis

Acetabular fractures

These fractures are divided into:

Anterior pillar (not weight bearing part of joint)

Posterior pillar (often associated with dislocation of the hip including the weight bearing part of joint)

Transverse

Comminuted involving both column type 

Sacral / coccygeal fractures

The sacrum is a triangular-shaped bone formed by 5 fused vertebrae, which provide a posterior wall to the pelvic ring. At each side of the sacrum, the ala structures articulate with the ilium bones forming the sacro-iliac joints. Sacral fractures are usually parallel to the spine and can involve the ala. Less frequently sacral fractures may display an “H” shape, including a transversal fracture uniting both sides of the sacrum. Three zones are described where sacral fractures can occur that are along vertical lines relative to the alignment of the foramina. Sacral fractures may result in sacral instability and require treatment via sacroplasty (injection of bone glue into the fracture). Surgery is necessary in case of associated neurological symptoms.

Fractures of the coccyx involve the tailbone, the terminal portion of the spine situated below the sacrum formed by 3 to 5 fused vertebrae. Coccyx fractures occur when falling on a seated position. They are more common in elderly women and seldom require surgical treatment.

Shoulder overuse is a cause of shoulder impingement syndrome

Causes

A shoulder impingement syndrome is commonly observed in young athletes and ageing individuals. It can arise from a trauma, such as a fall on the shoulder, as well as shoulder overuse due to repetitive overhead movement in either work or sport. Chronic inflammation of the bursa (bursitis) and/or tendons of the rotator cuff (tendonitis) can lead to the rupture of one or multiple tendons of the rotator cuff. Additional causes for a shoulder impingement syndrome include shoulder instability, shoulder stiffness, weakness of shoulder muscles, prolonged period of incorrect posture and inadequate physical activity.

Repetitive overhead movement in a swimmer may lead to a shoulder impingement syndrome

Risk factors

A shoulder impingement syndrome is frequently observed in people practicing overhead work in a variety of sports including swimming, throwing, tennis, weightlifting, golf, volleyball, gymnastics, as well as professions such as painting and mechanical repair. Performing repetitive abrupt movements of the shoulder in non-trained people is a risk factor for developing a shoulder impingement especially in those over 40 years of age. Ageing is in fact a risk factor for this pathology due to the weakening of tendons, lack of physical exercise and development of degenerative conditions of the shoulder. Shoulder arthritis and presence of bony spurs may lead in the long term to a shoulder impingement due to the restriction of the joint space. Congenital alterations in the shape of the acromion (hook acromion) may also increase the risk for a shoulder impingement syndrome.

Movement restriction and pain when reaching the back

Symptoms

Symptoms of a shoulder impingement syndrome include pain mostly with overhead movement of the arm and raising the arm laterally. Characteristic pain is felt when the arm is abducted between 700 and 1200 or reaching behind the back. Pain is exacerbated with worsening of the impingement severity. The condition causes progressive stiffness and movement restrictions producing poor sleeping quality particularly when lying on the affected shoulder. Patients suffering from this pathology encounter difficulties with daily activities such as washing, brushing hair and dressing. Weakening of the shoulder muscles is a common consequence of a shoulder impingement syndrome.

Clinical examination is required to form the diagnosis of a shoulder impingement syndrome

Diagnosis

The diagnosis of a shoulder impingement syndrome is formed with the initial medical history to evaluate the occurrence of incidents or physical activities that may have caused the disease. Clinical examination is based on a variety of tests to determine changes in the range of movement of the shoulder and special tests such as the provocative Neer’s test, Hawkin’s test and impingement sign. X-rays are taken to detect associated pathologies like arthritis, formation of bone spurs or abnormal acromion anatomy. Two additional diagnostic tools are used to ascertain the quality of the rotator cuff, tendons and bursa: Ultrasound is taken with abduction of the shoulder between 70º and 120º and MRI to rule out the presence of a rotator cuff tear. The diagnosis of an impingement syndrome is confirmed with the relief of pain upon injection of an anaesthetic into the space under the acromion.

Treatment

Local injection of steroids

Nonoperative treatment

Treatment of a shoulder impingement syndrome always begins with conservative management and involves a period of rest, application of ice or heat, oral use of NSAIDs, or local administration of steroids with the purpose of reducing inflammation and swelling. Physiotherapy, hydrotherapy and acupuncture are additional methods to reduce pain and restore the range of movements of the shoulder.S

‍Scars following arthroscopic shoulder surgery

Surgical treatment

Surgical intervention for the treatment of a shoulder impingement syndrome is recommended in case of a significant reduction of the joint space, with ongoing symptoms refractory to conservative treatment or when the impingement is combined with other pathologies (rotator cuff tear, bone spurs, arthritis). There are a number of surgery options relative to the individual mechanisms leading to an impingement syndrome. Subacromial decompression is performed to restore intra-joint space by resecting part of the acromion and any spurs that may be present. The impinged arthritic shoulder may be treated by resecting part of the clavicle with a procedure named arthroplasty. Additional approaches involve the removal of the bursa or bursectomy and acromioplasty, which consists in the resection of the acromio-clavicular ligament, the distal clavicle or surgical re-shaping of the acromion.

Rehabilitation aims at strengthening shoulder muscles to protect the joint

Rehabilitation

The rehabilitation period of an impinged shoulder may range from a few weeks to a year to achieve a full recovery. The onset of physical therapy depends whether or not the patient received conservative or surgical treatment and whether surgery consisted of arthroscopic or open approach. In non-operative treatment the patient will immediately begin active physiotherapy to restore shoulder strength and flexibility. Following surgery, instead, the shoulder is first put at rest with a sling for a few days prior to begin gentle physical exercise, which can be delayed to 2 weeks post-operative. Strenuous physiotherapy begins around 6 weeks post-surgery. Most commonly, pendular exercise and shoulder squeeze exercise are useful to strengthen and mobilise the shoulder. Physiotherapy also includes a number of additional measures:

Massage

Joint mobilisation

Ice/heat treatment

Physical exercise (stretching, pendular movements, shoulder shrug/squeeze, rotation)

Electrical stimulation

Education in sport and daily activities

Use of sport taping

Use of posture support

Return to sport plan

Regular stretching and physical exercise help preventing a shoulder impingement syndrome

Prevention

As for other shoulder pathologies, prevention consists mainly in avoiding or correcting those movements that contributed to a shoulder impingement, including overhead activity. Generally, it is beneficial to practice regularly physical exercise to strengthen the muscles of the shoulder and alleviate the pressure on the structures of the joints. It is also recommended to:

Avoid prolonged immobilisation of the shoulder

Begin targeted physical therapy and stretching of the shoulder joint early after surgery

Analyse and modify the ergonometric posture at work place

Use postural taping in athletes to support the shoulder during sport