impingement syndrome

definition

· term popularised by Charles Neer in 1972

· impingement of

· acromion (anterior edge and undersurface of anterior third)

· coraco-acromial ligament

· acromioclavicular joint (at times)

· on rotator cuff mechanism as glenohumeral joint moved

anatomy

Coracoacromial arch

· consists of two scapular projections (coracoid and acromion)

· connected by coracoacromial ligament

· continuous with clavipectoral fascia

· acromial branch of thoracoacromial artery runs in close relation along posterior margin

Subacromial bursa

· two serosal surfaces rather than space

· one on undersurface of deltoid and acromion

· one on rotator cuff

· help cuff slide under arch

Rotator cuff

Blood supply

· supraspinatus receives blood supply

· from muscle belly through branches of suprascapular and subscapular aa

· from bone through branches of anterior circumflex humeral a

· supraspinatus hypovascular near attachment to greater tuberosity

· critical zone of Codman

· corresponds to zone of anastomosis between osseous and tendinous vessels (watershed)

· vessels more abundant in bursal part cf. articular part

Function

Stability

· dynamic stabilisers of glenohumeral joint

· major role in supporting capsule

· long head of biceps is important depressor of humeral head

Movement

· motors for glenohumeral movement

· contribute 1/3 to 1/2 of power of abduction

· contribute 80% of power of external rotation

Susceptibility

· position in which most upper extremity functions performed is with hand in front of shoulder (esp. with shoulder in internal rotation)

· when arm raised thus, rotator cuff passes under anterior edge of acromion and aromioclavicular joint

· posterior third spared

· critical area of wear centred on supraspinatus tendon

· extends to anterior part of infraspinatus and long head of biceps

Acromion

Ossification

· arises from three centres of ossification

· usually united by age 22

· when centres fail to unite, ununited portion called os acromiale

· occurs in 3%

· segment may be large (5 x 2 cm)

· impingement may arise from

· downward hinging of acromion

· spurs or soft tissue proliferation at nonunion site

· condition present in 6% of those with impingement

Shape

· three types described by Bigliani

· Type I - flat (20%)

· Type II - curved (40%)

· Type III - hooked (40%)

· strong association between cuff tears and Type III acromia

· no association between impingement and Type III

· unclear whether shape is cause or result of cuff tear

classification

Stage I - inflammation

· oedema and haemorrhage after overuse

· young athletes in tennis and throwing sports

· weekend gardeners / handymen

· reversible to normal

Stage II - fibrosis

· repeated episodes of inflammation

· bursa fibrotic and thickened

· usually in older athlete or gardener / handyman

· shoulder satisfactory for light activity but pain after vigorous overhead use

Stage III - degeneration

· impingement wear leads to

· bone changes on anterior acromion and greater tuberosity

· incomplete or complete rotator cuff tears

· tears of biceps tendon (less common)

· almost exclusively in older patients

aetiology

Types

· three groups of patients (1/3 each)

Work

· symptoms related to work

· esp. tree pruning, fruit picking, nursing, carpentry, painting

Sport

· symptoms related to sport

· esp. throwing, tennis, swimming

Idiopathic

· no recognised precipitating factor

pathogenesis

Ischaemia

· critical zone of Codman

· MacNab theorised that there was a wringing out effect by the humeral head on the supraspinatus tendon with the arm adducted in neutral rotation

Mechanical wear

· Neer proposed that impingement is a mechanical process secondary to progressive wear

· in his experience it accounted for 95% of cuff tears

· wear may be predisposed by

· hooked acromion

· malunited fractures of greater tuberosity or humeral neck

Trauma

· may be a single violent event (macrotrauma), or repetitive motions (microtrauma)

· macrotrauma is uncommon as a cause of cuff pathology

· microtrauma is a well recognised factor

· occurs in repetitive throwing or overhead motions of the arm

Age

· age-related changes

· cause attrition of tendon

· supported by

· increased incidence with advancing age

· incomplete tears usually on articular surface

· tears often in sedentary workers with no history of trauma

Instability

· dysfunction of static stabilisers results in instability

· instability leads to anterior subluxation of humeral head

· abnormal position of humeral head causes impingement

Secondary impingement

Superior migration

· weakness of rotator cuff may result from disuse or damage

· contraction of deltoid leads to unopposed upward migration of humeral head

· leads to secondary impingement and further cuff disuse and damage

Reactive changes

· bursal thickening

· causes subacromial crowding

· exostosis

· on inferior acromion, AC joint or greater tuberosity

· precipitates wear of rotator cuff

clinical features

History

Pain

· characteristic location

· over greater tuberosity and lateral deltoid

· with activities when arm flexed and internally rotated

· work or sport

· ADL

· difficulties sleeping on affected side

Weakness

· as a result of

· pain

· rotator cuff damage

Examination

Wasting

· of deltoid with chronic disease

· of spinati with cuff tear

Tenderness

· maximal in subacromial region

· over acromioclavicular joint if degenerate

Range of motion

· active elevation more painful than passive elevation

· full active abduction may not be possible

· passive range usually full

· limitation of internal rotation and adduction indicates posterior capsule tightness

Painful arc

· pain when arm passes between 70^o to 120^o

· more pronounced when shoulder

· in plane of scapula (halfway between abduction and flexion)

· in maximum internal rotation

Crepitus

· esp. through painful arc

Weakness

· of abduction and external rotation

· due to rotator cuff damage

Neer's impingement sign

· stand behind seated patient

· fix scapula with one hand (to prevent rotation)

· elevate (between flex and abduct) shoulder with other

· pain caused by impingement of greater tuberosity on acromion

· not specific for impingement syndrome

Neer's impingement Test

· 10 ml 1% xylocaine injected beneath anterior acromion

· pain of impingement sign eliminated or markedly reduced

Drop Arm Sign

· unable to maintain 90 degrees of abduction against gravity

· consistent with large tear

Clinicopathological features

	STAGE 1	STAGE II	STAGE III
Pathology	oedema, haemorrhage	fibrosis, tendinitis	cuff tears, bone spurs
Age	< 25	25-40	> 40
X-rays	normal	normal	subacromial sclerosis
Differential	instability, AC jt dislocation	frozen shoulder, calcific tendinitis	cervical radiculopathy, GH or AC osteoarthritis
Clinical	reversible	recurrent pain with activity	progressive disability
Treatment	rest, physio	rest, HCLA	acromioplasty, cuff repair

investigations

Plain radiographs

Early

· normal in stage I and II

Late

· changes seen in stage III

· subacromial sclerosis (eyebrow sign)

· sclerosis of greater tuberosity

· acromial spur

· degenerative changes in AC joint

Cuff tear

· decreased acromiohumeral interval

· normal gap is 7-14 mm

· massive tear suspected if < 5 mm

· superior migration due to

· loss of substance of rotator cuff between acromion and humeral head

· unopposed elevation of humeral head by deltoid with loss of depressing and stabilising action of supraspinatus

· cuff arthropathy

· secondary osteoarthritis

· from wear of humeral head on undersurface of acromion

Ultrasound

· reliably demonstrates full-thickness rotator cuff tears > 1cm in size

· 85% positive predictive value

· defects revealed as

· absence of normal echoes

· failure of tissue to move with humeral head

· advantages

· non-invasive

· economic

· comfortable

· disadvantages

· operator dependent

· tears < 1 cm often missed

· difficult to differentiate scarring, incomplete tears and small full-thickness tears

Arthrography

· no communication normally exists between shoulder joint and subacromial bursa

· when contrast injected into shoulder and demonstrated in subacromial bursa, complete tear can be inferred

· more information can be obtained if

· double-contrast technique (air and contrast injected)

· combined with CT scan

· indications

· impingement not responsive to 3 mths nonoperative treatment

· injury with sudden weakness of abduction and external rotation

· shoulder problem following glenohumeral dislocation if age > 40

· technique

· patient prone

· needle introduced in palpable depression where acromion joins scapular spine

· needle aimed towards coracoid (slightly superiorly)

· 8 ml air and 2 ml contrast injected

· shoulder taken through full range of motion

· x-rays taken

· advantages

· good at demonstrating complete cuff defects and partial thickness cuff defects at deep surface

· 85% specificity and sensitivity

· disadvantages

· invasive

· does not show intrasubstance and bursal side tears

MRI

· shows coraco-acromial arch and cuff tears well

· 100% specificity and 95% sensitivity

· expensive and time-consuming

· difficulties with interpretation due to lack of experience

Arthroscopy

· demonstrates defects of rotator cuff involving both deep and bursal surface

· more limited role as MRI improving

differential diagnosis

Other cuff lesions

· chronic calcific tendinitis

· cuff tendon strain

· cuff tear

· biceps tendinitis

· frozen shoulder

Extrinsic to cuff

· acromioclavicular arthritis

· glenohumeral instability

· degenerative glenohumeral joint disease

· cervical radiculopathy

· brachial neuritis

· mediastinal pathology

treatment

Nonoperative

· most cases can be treated nonoperatively

· should be vigorously pursued in athletes

· low success rate in returning to competition after surgical decompression

General

· rest

· NSAIDs

· rehabilitation

· steroid injections

Rehabilitation

· Jackins programme

Avoidance of repeated injury

· activities at work or sport that aggravate tendinitis

Restoration of normal flexibility

· stretch out in all directions of tightness

· gentle sustained stretching exercises

Restoration of normal strength

· rotator muscle and periscapular muscle strengthening

· against resistance of rubber tubing

Aerobic exercises

· regular aerobic exercise to maintain fitness

Modification of work or sport

· assessment of activities at work or sport and education and modification

Steroids

· common experience that subacromial injections produce symptomatic relief

· some reservations

· placebo-controlled trial found no evidence of efficacy

· steroid injections in or near cuff and biceps tendons may produce atrophy and reduce ability of tendon to repair itself

· technique

· posterior approach

· enter just below posterolateral corner of acromion

· aim superiorly at 30^o

· long-acting local anaesthetic and depot preparation of steroid injected (4 ml Marcain and 1 ml Celestone Chronodose)

· maximum of 3 injections at least 2 months apart

Duration

· if no response to rehabilitation at six weeks or persistence of major symptoms at three months, arthrogram or ultrasound performed to look for cuff tear

· if cuff tear suspected at initial assessment, arthrogram or ultrasound used earlier

· if positive investigation, consider cuff repair

· if negative investigation, continue with rehabilitation for six months

· consider surgery at twelve months

Operative

Indications

· persistent disability after 1 year if pain relieved with subacromial local anaesthetic

· good result expected if patient

· > age 40

· well motivated

· absence of stiffness

· pain relieved by subacromial local anaesthetic

Contraindications

· less than 12 months nonoperative treatment

· impingement secondary to instability

· young patient with stage I disease

Technique

Approach

· beach chair position

· 7 cm sabre (shoulder-strap) incision

· from centre of AC jt

· continued inferiorly

· skin and subcutaneous tissue down to deltoid fascia undermined

· medially to past acromioclavicular joint and 4 cm laterally

· longitudinal split made in deltoid fibres

· anterolaterally in line with clavicle

· in fibrous raphe between anterior and lateral parts of deltoid

· usually 2-3 cm

· no further than 5 cm (axillary nerve)

· split in deltoid continued up through delto-trapezius fascia on dorsal aspect of acromion

· exend to AC jt and clavicle if needed

· deltoid detached from acromion subperiosteally in continuity with fascia anterior to split

· expose anterior part of acromion

· from lateral corner to AC jt

Acromioplasty

· origin of coracoacromial ligament from anterior and inferior acromion detached

· broad flat insrument introduced under acromion to protect rotator cuff

· vertical cut made with osteotome to resect all of anterior acromion that projects beyond anterior margin of clavicle

· anteroinferior corner of acromion removed with osteotome

· aim to convert undersurface to flat surface

· hypertrophied subacromial bursa resected

Acromioclavicular joint

· distal 1 cm of clavicle resected if assessed to be degenerative preoperatively

· tenderness on palpation with relief of symptoms by injection

· degenerative changes on x-ray

· inferior osteophytes resected from AC jt

Rotator cuff

· rotator cuff inspected carefully

· any defect repaired

Biceps tendon

· if rotator cuff defect present, biceps tendon explored

· if more than 50% of tendon eroded, tenodesis in groove performed

Closure

· deltoid reattached to raw surface of acromion with interrupted non-absorbable sutures (may need drill-holes)

· split in deltoid and deltotrapezius fascia closed

· routine closure

Postoperative care and rehabilitation

· pendulum exercises and passive forward flexion commenced on first postoperative day

· stick or pulley used to increase forward flexion range on second postoperative day

· arm used for gentle ADL

· sling worn when in public

· increased ADL and isometric programme started during third postoperative week

· deltoid repair protected by avoiding active elevation

· at six weeks, isokinetic programme for deltoid and rotator cuff started

Results

· 75-90% good or excellent results

· results inferior if distal end clavicle resected

· longer rehabilitation if cuff defect repaired

· failures due to

· incorrect diagnosis

· incomplete decompression

· failure of deltoid reattachment

· excessive removal of acromion

· irreversible cuff pathology (intratendinous tears or scarring)

· postoperative scarring between cuff and acromion

· failure of rehabilitation

Arthroscopic acromioplasty

· advantages

· no incision

· minimises deltoid injury

· facilitated rehabilitation

· shortened postoperative recovery

· adequate bone removal important for success

· early results not as good as open acromioplasty

· technique improving

· cadaveric study showed no significant difference in amount of bone removed open vs arthroscopically

· recent prospective studies have shown similar satisfactory outcomes with arthroscopic decompression compared with open technique

· technically demanding procedure

· problems with haemostasis

· unsatisfactory if rotator cuff defect requiring repair present