Translations of the Humerus in Persons with Shoulder Impingement Syn

1
Translations of the Humerus in Persons with
Shoulder Impingement Syn

• Ludewig PM, Cook TM
• J ortho sports Phys Ther 200232248-259

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Design Objectives

• Two-group mixed-model analysis of covariance
  correlation analysis
• Abnormal translations of the humeral head
  believed to contribute to the development
  progression of shoulder impingement symptoms
• Determine whether differences in humeral
  translations exist between pts with impingement
  and asymptomatic
• If shoulder ROM are associated with abnormal
  translations.

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Methods Measures

• 3-D tracking of humeral translations
• While elevating arm in scapular plane
• No load, 2.3 kg, 4.6 kg hand-load
• Association between humeral translations
  cross-body adduction shoulder internal rotation
  ROM (Pearson correlation)

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Results

• Pts with shoulder symptoms had small but
  significant changes in A-P translations of the
  humerus.
• Changes for 90-120 deg phases of humeral
  elevation mildly negatively correlated with
  cross-body adduction ROM

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Previous Literature

• Shoulder pathologies impingement, instability,
  rotator cuff tears
• Associated with abnormal kinematics
• 1/3 of MD visits for shoulder pain
• Impingement can progress to rotator cuff tears
• Repetitive impingement, not trauma cause rotator
  cuff tears

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Primary mechanisms for impingement

• Shoulder kinematic deviations
• Anatomic abnormalities
• Repetitive eccentric overload
• Ischemia
• Degeneration of rotator cuff tendons
• Frequent or sustained use of arm at or above
  shoulder level

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Altered kinematics rotator cuff mechanism

• Contribute to problem
• Regardless of cause
• Perpetuate
• Exacerbate
• Impingement symptoms

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Impingement

• Due to inadequate clearance of rotator cuff
  tendons as arm is elevated
• Specific kinematic changes further minimize the
  space
• 3D MRI study position dependent subacromial
  space reduction
• 90 deg scapular plane abd with abductor activity
  subacromial space 3 mm less in painful shoulder
  vs non-painful

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Proposed Mechanisms

• Abnormal superior or anterior translations of
  humerus
• Little evidence
• Poppen 15 pts, 7 abnormal location of instant
  center of rotation of humeral head, 6 increased
  translation of humeral head
• Posterior capsule tightness cadaver studies,
  clinical measures
• Abnormal scapular motion
• Increasing evidence
• ? Studies or hypotheses

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Specific Hypotheses

• Abnormal superior and anterior translation
  motions of humeral head in impingement
• Humeral internal rotation and horizontal
  cross-adduction negatively correlated with
  translations of humeral head

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Instrumentation

• Fastrak 3 sensors gave relative 3 D info
• 1 taped to sternum
• 1 taped to flat superior surface of scapula
  acromion process
• 1 thermoplastic cuff secured to distal humerus
  with velcro straps
• Validated to bone-fixed markers on scapula and
  humerus
• Bony landmarks on thorax, scapula, humerus
  palpated digitized
• Length of humerus digitized

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Procedures

• Humeral head center determined from data from 20
  multiplanar humeral positions at 45 deg elevation
• Least squares algorithm used to calculate average
  pivot point
• Humeral elevation guided in scapular plane 40
  deg anterior to coronal plane
• Kinematic data from 5 reps through full ROM at
  varying loads
• Reliability from 6 subjects following day
  repeated measures

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Procedures

• Sensor orientation data transformed to describe
  relative positions of anatomical coordinate
  systems for each segment (Fig 1)
• Translations of humerus relative scapula
• 30-60 60-90 90 -120 of humeral rotation
  relative to thorax axis where impingement
  occurs
• Orientation of helical axis translations along
  that axis for humeral motion relative to scapula
• Helical axis single oblique axis about which
  the humerus is rotating for that specific phase
  of motion

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Helical axis

• Z component superior inferior translation
• Y component anterior posterior translation

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Reliability measures

• Intraclass correlation coefficients
• Standard error of the mean

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Results

• 52 subjects (26 in each group)
• No significant difference in demographics
• Active ROM internal rotation
• No significant differences
• Cross-body adduction significant differences
  asym 51.2 (9.7) sym 44.4 (8.9)
• Correlations high for humeral a-ps-I translations

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Humeral anterior-posterior translations

• Sig main group effect
• Symptomatic group 1 mm differences in
  translation per phase
• 30 60 most anterior translation
• Other 2 phases showed less posterior translation
  than asymp

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Humeral superior-inferior translations

• 60-90 90-120 demonstrated less superior
  translation than the 30 60 phase
• Humerus translated superiorly during 30-60 and
  then stayed stationary for last 2 phases

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Correlations

• Cross-body adduction internal rotation
• Not associated with magnitude of
  superior-inferior translation fors 30-60 or 60-90
• Cross-body adduction significantly associated
  with magnitude of anterior-posterior translation
  (r-.48)
• Negative correlation indicates that greater
  anterior translation associated with less ROM

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Discussion

• Provides partial support for 1st hypothesis
• A-P translations in symptomatic group slightly
  but significantly different with total difference
  of 3 mm across 30-120 deg ROM
• If started in same position, humeral head would
  be closer to undersurface of acromion,
  coracoacromial lig, coracoid process in
  symptomatic group
• Space is small, decreases with active elevation
  of arm until reaching 5 mm by 100 -110 deg of
  elevation

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Subacromial space

• Must accommodate articular cartilage, joint
  capsule, ligs, rotator cuff tendons, subacromial
  bursa
• 68 reduction in space in individuals with
  impingement (3mm less) Graichen
• 23 reduction in cadavers with full-thickness
  rotator cuff tears
• Small decreases important particularly if
  inflammation, fibrosis, thickening of tendons or
  bursa, anatomic abnormalities

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Anterior-posterior translations

• Humeral head usually centered
• 4 mm posterior if maximally extended laterally
  rotated in horizontal plane (Howell)

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Methods

• Subjects carpenters or sheet metal workers
• Work at or above shoulder level
• 40-50 incidence of shoulder pain
• Inclusion criteria
• Anterior shoulder pain gt 1 week
• Tenderness to palpation of rotator cuff tendon,
  positive impingement test, painful arc of motion
  (60-120 deg), abd to 130 deg

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Impingement tests

• Clinical tests
• Specific or sensitive, not both