Scapular dyskinesis

Definition

Scapular dyskinesia is defined as observable alterations in the static position of scapula or abnormal patterns of motion of scapula during coupled scapulohumeral movements in relation to the thorax.

Introduction

  • Due to inhibition or disorganization of activation patterns of scapular stabilizing muscles.
  • Disrupts the normal rhythm of scapulohumeral motion and shoulder kinematics.
  • Associated with various shoulder pathologies such as impingement, adhesive capsulitis, instability, SLAP lesions, rotator cuff injuries and acromioclavicular disorders.
  • May be the cause, effect or compensation. Exact role in shoulder dysfunction unknown.
  • It may exacerbate symptoms or adversely affect the outcomes of treatment.
  • Other causes are pectoralis minor contracture, Glenohumeral internal rotation deficit (posterior capsule of shoulder contracture), excessive thoracic kyphosis or excessive lumbar lordosis.
  • Frequently seen in athletes with shoulder injuries. It is also in asymptomatic individuals.
  • Treatment directed towards underlying cause and by kinetic chain based rehabilitation protocols to restore normal muscle activation protocols.

Functions of scapula

  • Provision of a stable but mobile foundation for humeral head during glenohumeral motion
  • Scapulothoracic motion
  • Elevation of acromion during abduction to prevent impingement of supraspinatus.
  • As a link in the kinematic chain for proximal-to-distal sequencing of velocity, forces and energy of shoulder function.

Scapular kinematics

  • Scapula, shoulder and humerus are either stabilized or moved during various activities to generate, absorb or transfer forces.
  • To optimize function, the scapula should move in coordination with the movements of humerus to maintain the instant centre of rotation and the alignment of glenohumeral joint. This has been likened to the balancing of a ball on seals nose.
  • Control of scapular position and motion is an important component of shoulder function.
  • It needs fine control of position and motion of scapula by specific muscle activation patterns.
  • Scapular movements may be at the glenohumeral or scapulothoracic joint.
  • Scapulothoracic movements occur between the scapula and the thoracic wall aided by the acromioclavicular and sternoclavicular joints.
  • Measurement of scapular movements may be done in two dimensions or in three dimensions.
  • Normal scapular motion may be rotations or translations
  • 3 rotations
    • Upward or downward
    • Internal or external rotation
    • Anterior or posterior tilt
  • 2 translations
    • Superior or inferior
    • Anterior or posterior
  • Normalscapular motionduringglenohumeral elevation.
    • Upward rotation 500, External rotation- 240, posterior tilt- 300.
    • Clavicle elevation 100, clavicle retraction- 210.
    • Scapulohumeral rhythm- 2:1

Scapular force couples involve contraction ofagonists and antagonists forscapular stabilization or controlled motion.

  • Scapular stabilization- Upper and lower trapezius and the rhomboids coupled with the serratus anterior.
  • Scapular elevation- Serratus anterior and lower trapezius coupled with the upper trapezius and rhomboids.

Abnormal kinematics in scapular dyskinesia

  • Serratus anterior and lower trapezius most susceptible to inhibition by pain or disease.
  • Abnormal kinematics patterns.
    • Serratus anterior fatigue or weakness- Increased upward rotation
    • Trapezius weakness or fatigue- Decreased upward rotation.
    • Infraspinatus weakness- Decreased posterior tilt
    • Frozen shoulder- Increased superior translation.
    • Impingement syndromes- Decreased posterior tilt, decreased external rotation, decreased upward rotation
  • Effectsofscapulardyskinesis
    • Loss of retraction and protraction control- Loss of full retraction leads to loss of stable cocking position during throwing and arm elevation. Loss of full protraction increases deceleration forces on the glenohumeral joint. Increases shear stresses on anterior stabilizing structures. It may also lead to impingement.
    • Loss of elevation control- Can lead to impingement
    • Loss of kinematic chain function.

Causes of scapular dyskinesis

Postural anomaly

  • Cervical lordosis
  • Thoracic kyphosis

Anatomic disruptions

  • Clavicle fracture
  • ACJ disruptions

Nerve injury

  • Spinal accessory palsy- Causes psuedowinging of scapula with prominence of medial border, scapula is laterally rotated and inferiorly translated.
  • Long thoracic nerve palsy- Causes winging with prominence of medial border, scapula is medially rotated and superiorly translated.
  • Dorsal scapular nerve palsy- Scapula translated inferiorly and laterally

Contractures

  • Pectoralis minor- Increased anterior tilt and decreased scapular retraction during abduction
  • Glenohumeral internal rotation deficit

Muscle imbalance or weakness.

  • Muscular dystrophy

Proprioceptive dysfunction

Types of scapular dyskinesia (Kibler)

  1. Prominence if inferior angle of scapula- Due to excessive anterior tilting of scapula.
  2. Prominence of entire medial border of scapula. Due to excessive internal rotation of scapula.
  3. Prominence of superior scapular border- Due to excessive upward translation of scapula.
  4. Normal- No asymmetries, no prominence of borders or angles.

Clinical Methods

  • Clinical assessment includes observation of bilateral scapular position at rest and during movements.
  • Resting position assessed with the patient standing, arms by the side of body, elbows fully extended, hands by the side of thigh with the thumbs pointing forward.
  • Resting position of scapula
    • Serratus anterior palsy- Prominent superior medial border and depressed acromion.
    • Trapezius palsy- Prominent inferior border and elevated acromion.
  • Ask the patient to elevate and lower both the arms in the sagittal plane (forward flexion) with the elbows in extension. Repeat several times.
  • Repeat the motion in the scapular plane of 300 (Scaption).
  • Observethe motion of medial and superior borders and the inferior angle of scapula during repeated motions of arm elevation and lowering.
    • Special tests
    • Step1- Observation
      • Dynamicscapulardyskinesis test
        • Patient holds 1 kg weight in each hand then forward flexes first then abducts.
        • Observe for any winging or prominence of medial or inferior scapular borders.
        • Any deviation from normal considered as dyskinesia.
      • Lateralscapular slide test
        • Measure the distance from the medial border of scapula to a fixed point on the spine in 3 positions of arm.
        • Firstly with the arms by the side of body; secondly with the hand on hips with fingers anterior, thumb posterior and shoulder in 100 extension and lastly with the arms elevated to 900 with maximal internal rotation.
        • >1.5 cm asymmetry is abnormal.
      • Posterior displacement test
      • Scapular upward rotation measure
    • Step2- Assisted correction
      • Scapularassistancetest-
        • Done in those with impingement symptoms.
        • Assistance to scapular elevation during elevation or abduction given by manually stabilizing the scapula by keeping the hand on the superior border of scapula and also by rotating the inferior angle of scapula outwards with the other hand.
        • Increased power or decreased symptoms is considered as positive.
      • Scapular retraction test.
        • Manually stabilize the medial border of scapula in a retracted position. Ask the patient to forward flex and abduct.
        • Improved rotator cuff function considered as positive.
    • Step3- Assess other structures
      • Thoracic and cervical posture
      • Lumbar lordosis
      • Pelvic tilt
      • Acromioclavicular joint
      • Rotator cuff, labrum, biceps tendon
      • Glenohumeral range of movements
      • Wall push-ups to assess serratus anterior
      • Muscle strength
      • Measure the clavicle
    • Normal scapular motion described as bilateral posterior tilting, external rotation and slight superior translation during arm elevation and reversal of these during lowering of arm.

Problems with clinical assessment are the following.

  • Difficulties in assessment of scapular motion due to overlying soft tissues.
  • Difficulty in measurement of multidirectional movement in 3 types of rotations and 2 types of translations.
  • Lack of criteria of clinical assessment methods

Treatment

  • Treatment is by physiotherapy aimed at correction of posture, correction of movement deviations believed to reduce subacromial space and improvement of soft tissues by strengthening and stretching.
  • Treatment is for the underlying cause and by physical therapy to relieve symptoms and to regain muscle strength and activation patterns.
  • Physical therapy aimed at improving muscle strength, alter scapular position and reduce shoulder pain.
  • Rehabilitation should be comprehensive and should be in phases.
  • Phases of rehabilitation are
    • Acute phase- (0-3 weeks)
    • Recovery phase (3-8 weeks)
    • Maintenance phase (6-10 weeks)
  • Rehabilitation proceeds in a proximal to distal protocol.
  • Starts in the spine and hip. Once proximal control is achieved start scapular exercises followed by shoulder and arm exercises.

Acute phase 

  • Avoid painful movements and positions.
  • Start assisted stretching
  • Start closed chain exercises with hand supported
  • Start scapular exercises without arm elevation.
  • Start shoulder and arm exercises.

Recovery phase

  • Increase load of closed chain exercises
  • Add arm elevation as tolerated.
  • Begin kinetic tubing exercises
  • Start lunges with dumbbells.

Maintenance phase

  • Start dynamic-stretch-shortening (Plyometric) exercises.
  • Start overhead dumbbell presses and lunges.

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