Updated: 3/10/2019

Internal Impingement

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Introduction
  • Overview
    • internal impingement is a cause of shoulder pain in overhead athletes caused by repetitive impingement of the undersurface of rotator cuff
      • treatment with physical therapy and posterior capsule stretching is effective for most
  • Epidemiology
    • major cause of shoulder pain in throwing and overhead athletes
  • Pathophysiology
    • mechanism
      • impingement occurs during maximum arm abduction and external rotation during late cocking and early acceleration phases of throwing  
      • causes "peel-back" phenomenon of posterosuperior labrum by the biceps
    • pathoanatomy  
      • caused by repetitive impingement of posterior under-surface of supraspinatus tendon greater tuberosity
      • pathologic micromotion of the humeral had allows the rotator cuff to become impinged between the humral head and glenoid.
        • in contrast to subacromial or "external" impingement which occurs on bursal side of rotator cuff 
      • internal impingement covers a spectrum of injuries including 
        • fraying of posterior rotator cuff (supraspinatus-infraspinatus interval)
        • posterior and superior labral lesions
        • hypertrophy and scarring of posterior capsule glenoid (Bennett lesion)
        • cartilage damage at posterior glenoid
    • etiology
      • tightness of posterior band of IGHL 
      • anterior micro-instability
  • Associated conditions
    • associated with GIRD 
    • SLAP tears
    • SICK scapula and dyskinesia
Anatomy
  • Glenohumeral joint anatomy 
  • Glenohumeral stability
    • static restraints
      • glenohumeral ligaments  
      • glenoid labrum 
      • articular congruity and version
      • negative intraarticular pressure
    • dynamic restraints
      • rotator cuff muscles
      • biceps
      • periscapular muscles
  • Rotator cuff 
    • primary function is dynamic stability  and centering the humeral head within the glenoid via balancing the force couples about the glenohumeral joint in both coronal and transverse planes, creating a stable fulcrum
      • coronal plane
        • the inferior rotator cuff (infraspinatus, teres minor, subscapularis) balances the superior moment of the deltoid
      • transverse plane
        • the anterior cuff (subscapularis) balances the posterior moment of the posterior cuff (infraspinatus and teres minor)
      • the goal of treatment in rotator cuff tears is to restore this equilibrium in all planes
Classification
  • No formal classification scheme
Presentation
  • Symptoms
    • shoulder pain, sometimes loalized posteriorly 
      • diffuse pain in posterior shoulder along the posterior deltoid
      • shoulder pain worse with throwing
        • especially during late cocking and early acceleration
  • Physical exam
    • inspection
      • may see retroversion of proximal humerus 
      • pain with palpation along infraspinatus
    • ROM
      • increased external rotation
      • decreased internal rotation 
        • loss of > 20° of IR at 90° compared to contralateral shoulder
          • must stabilize the scapula to get true measure of glenohumeral rotation
      • preservation of the total arc of motion
    • strength
      • often can demonstrate rotator cuff weakness
    • provocative tests
      • Whipple test
        • performed to test for partial suprapinsatus tears
        • performed by ranging shoulder in forward flexion, adduction and scapular retraction
        • positive when pain is reproduced on resistance 
      • Apprehension test
        • positive for internal impingement
        • performed by bringing shoulder into maximum ER, abduction and extension
        • positive if posterior shoulder pain reproduced in this position and relieved when arm brought into neutral extension/flexion
Imaging
  • Radiographs
    • recommended views
      • complete shoulder series
    • findings
      • usually unremarkable
      • AP may show a Bennett lesion (exostosis of posteroinferior glenoid) 
  • MRI or MR arthrogram
    • findings
      • can show pathology of the rotator cuff and/or labral pathology
        • such as partial articular-sided supraspinatus-infraspinatus tendon avulsion (PASTA), frayingor tear 
        • signal at greater tuberosity and/or posterosuperior labrum  
    • optional views
      • ABER positioning reproduces position of impingement showing dynamic process on the humerus and glenoid sides
Treatment
  • Nonoperative
    • PT, cessation from throwing, posterior capsule stretching 
      • indications
        • first-line of treatment
        • most internal impingement can be treated non-operatively
        • Operative treatment should only be considered if patient has failed adequate physical therapy for an extended period of time as results folliwing operative intervention are unpredictable 
  • Operative
    • arthroscopic debridement of rotator cuff and/or labrum 
      • indications
        • failure of nonoperative treatment and 
          • partial thickness rotator cuff tear (PASTA) that compromise the integrity of the rotator cuff
            • partial rotator cuff tears <50%  
          • Bennett lesions
          • peel-back labral lesion
    • Arthroscopic vs mini-open rotator cuff and/or labral repair
      • indications
        • partial tears >50% tendon thickness or full thickness tears
        • unstable labral tears
    • Posterior capsule release vs anterior capsular stabilization
      • indications
        • persistent posterior capsule contracture or anterior shoulder instability in addition to any of the above pathology
Techniques 
  • PT, cessation from throwing, posterior capsule stretching
    • cessation
      • break from throwing until pain subsided, followed by supervised return to throwing focusing on proper mechanics
    • therapy
      • posterior capsular stretching program (i.e. sleeper stretches), rotator cuff strength balancing, scapular stabilization, kinetic chain coordination
      • stretching for 6 months
    • outcomes correlated with compliance to therapy regimen
  • Arthroscopic debridement of rotator cuff tear and/or labrum 
    • diagnostic arthroscopy
      • perform meticulous exam under anesthesia to assess range of motion
      • diagnostic arthroscopy intra-articular and subacromial
    • debridement
      • arthroscopic shaver to debride loose tissue edges
    • allows accelerated rehab and return to throwing
    • shorter post-op immobilization time
  • Arthroscopic vs mini-open rotator cuff repair
    • approach
      • arthroscopic has advantage of addressing labral and other intra-articular pathology
    • acromioplasty
      • bursectomy performed to visualize bursal-side of tendon
      • acromioplasty is not indicated if no bursal-sided pathology seen
    • cuff repair
      • abrasive preparation of the greater tuberosity footprint
      • portal of Wilmington usually necessary
      • partial-thickness tears
        • in-situ trans-tendinous repair
          • pulley technique utilizing suture anchors to reduce tendon to tuberosity
          • will functionally shorten the tendon length
      • complete partial tear followed by anatomic repair technique
        • single or double-row repair
    • labrum
      • prepare glenoid rim and repair of unstable labral tear
  • Posterior capsular release vs anterior stabilization
    • posterior release
      • done adjunctively with above procedures
      • cautery wand or arthroscopic shaver to release synovium and capsular tissues
      • risk of axillary nerve injury 
    • anterior stabilization
      • done adjunctively with the above procedures
      • capsular plication most common
Complications 
  • Progression to full-thickness rotator cuff tear
    • small risk of partial tears treated with debridement alone
  • Delayed Rate of Return to Play
    • worse rates following rotator cuff repairs in throwing athletes
  • Axillary nerve injury
    • at risk during posterior release at the inferior border of infraspinatus
 

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Questions (12)

(SAE07SM.99) Which of the following anatomic structures are in contact with internal impingement in the throwing athlete? Review Topic

QID: 8761
1

Humerus and posterior-superior glenoid

64%

(42/66)

2

Humerus and anterior inferior glenoid

17%

(11/66)

3

Humerus and acromion

3%

(2/66)

4

Biceps and acromion

3%

(2/66)

5

Rotator cuff and acromion

14%

(9/66)

ML 3

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(OBQ10.174) A 19-year-old left-hand dominant collegiate baseball pitcher has left shoulder pain with late cocking and early acceleration of the ball. His velocity has decreased over the past 2 months. Rotator cuff strength is normal, he denies symptoms of instability, and Hawkins impingement testing is unremarkable. MRI with contrast reveals no intra-articular lesions. What is the most likely physical exam finding in this patient? Review Topic

QID: 3267
1

Positive sulcus sign

1%

(29/2069)

2

Decreased external rotation of the affected shoulder

8%

(173/2069)

3

Positive Speed's test

4%

(86/2069)

4

Decreased abduction of the affected shoulder

1%

(18/2069)

5

Decreased internal rotation of the affected shoulder

85%

(1749/2069)

ML 2

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PREFERRED RESPONSE 5

(OBQ11.140) Internal impingement commonly occurs in overhead athletes and is very common amongst elite baseball pitchers. In which phase of throwing does this pathologic process occur? Review Topic

QID: 3563
1

Wind-up

1%

(29/2739)

2

Early cocking

5%

(147/2739)

3

Late cocking

80%

(2193/2739)

4

Deceleration

8%

(221/2739)

5

Follow-through

5%

(138/2739)

ML 2

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(OBQ09.142) Mineralization of the posterior-inferior glenoid has been implicated as a possible source of pain in which athletic population? Review Topic

QID: 2955
1

football players

14%

(73/536)

2

swimmers

11%

(59/536)

3

basketball players

1%

(3/536)

4

rowers

14%

(75/536)

5

baseball pitchers

60%

(324/536)

ML 3

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PREFERRED RESPONSE 5

(OBQ07.38) A baseball pitcher has aching pain in the posterior shoulder after throwing. On exam, he has a 30 degree internal rotation deficit and is diagnosed with internal impingement. Stretching should focus on which aspect of the joint capsule? Review Topic

QID: 699
1

Superior

3%

(13/417)

2

Anterior

3%

(12/417)

3

Antero-inferior

9%

(36/417)

4

Inferior

1%

(4/417)

5

Postero-inferior

84%

(350/417)

ML 1

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PREFERRED RESPONSE 5

(OBQ08.4) The term internal impingement is used in throwers to describe a condition where the posterior-superior glenoid labrum impinges on which structure? Review Topic

QID: 390
1

The anterior rotator cuff

9%

(125/1448)

2

The posterior rotator cuff

70%

(1014/1448)

3

The anterior glenohumeral ligaments

3%

(44/1448)

4

The posterior glenohumeral ligaments

15%

(210/1448)

5

The biceps tendon

4%

(54/1448)

ML 2

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PREFERRED RESPONSE 2
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