The Influences of Subscapularis Lesion on Ultrasonography and Kinematics in Patients With Shoulder Impingement
Condition: Shoulder Impingement Syndrome
MeSH terms: Shoulder Impingement Syndrome; Syndrome; Rotator Cuff Injuries
Study type: Observational

Summary: 
      Subacromial and subcoracoid impingement have been categorized as external impingement, one
      type of shoulder impingement syndrome (SIS). Differentiation between subacromial impingement
      and subcoracoid impingement are important in determining the treatment target. The thickness
      of the coracohumeral ligament (CHL) may affect coracohumeral distance (CHD), which has been
      suggested as a possible factor in developing subcoracoid impingement with subscapularis (SSC)
      lesion. Evidence that indicates the existence of abnormal SSC, CHL thickness and CHD in
      people with SIS is limited. The purposes of the study were (1) to evaluate the correlations
      between CHL thickness and CHD by using ultrasonography in people with SIS with and without
      SSC lesion, (2) to examine the difference in SSC/CHL thickness and CHD between people with
      SIS with and without SSC lesion.
    

Detailed description: 
      Based on previous studies, a total sample size of 40 participants was calculated to provide
      80% power with detection of a difference of more than 1.0 mm CHD between 2 groups. The
      inclusion criteria of the participants were age of 20-60 years old and positive unilateral
      shoulder results on at least 3 of 5 tests: 1) Neer's test, 2) Hawkins' test, 3) the Empty can
      test, 4) the pain or weakness with resisted ER test, and 5) tenderness in the tendon of the
      rotator cuff. Participants with a history of shoulder dislocation, fracture or surgery,
      history of direct contact injury to the neck or upper extremities within the past month,
      glenohumeral joint instability (positive apprehension test, sulcus sign), neurologic disorder
      (upper motor neuron diseases, cervical radiculopathy), passive ER Range of Motion (ROM) less
      than 30 degrees, or pain (visual analogue scale, VAS more than 5) during the experimental
      tasks were excluded. After the impingement tests were performed to ensure that the
      participants met our inclusion criteria, all participants were assessed with 3 special SSC
      tests, namely, the lift-off test, belly-press test (Napoleon sign) and bear-hug test, for
      group allocation. Patients with positive results on at least 2 of the 3 special tests were
      allocated to the SSC lesion (SSCL) group.

      The characteristics of the participants were collected by one assessor, including age,
      gender, height, weight, dominant side, involved side, duration of symptom, pain (VAS),
      occupation ratio, the Flexilevel Scale of Shoulder Function (FLEX-SF) and internal rotator
      strength.

      USG measurements We measured the following outcomes: (1) CHL thickness, (2) CHD and (3) AHD.
      Each outcome was measured in 3 trials and the mean of the 3 trials was used for data
      analyses. All of the measurements were measured with THI turned on except for that of CHD,
      due to the deeper anatomical structure.

      For measurement of the CHL thickness, the position of the linear probe was on the lateral
      border of the coracoid process to obtain a longitudinal image of the CHL. Each participant
      was instructed to lie in supine position and relax while the examiner maintained the elbow of
      the participant at flexion of 90° and the shoulder under maximal ER without shoulder
      abduction or flexion (arm by side) (Figure 2). Maximal ER of the shoulder was achieved when
      the examiner could not further externally rotate the shoulder of the participant. The
      thickness of the CHL at a 2-mm distance from the coracoid process was measured.

      CHD was measured with the probe positioned on the lateral border of the coracoid process to
      obtain images of the coracoid process and humeral head in 4 different shoulder rotation
      positions: (1) shoulder neutral rotation (CHD-NR), (2) external rotation (CHD-ER) and (3)
      shoulder internal rotation with maximal forward flexion and full adduction (CHD-IRFA, with
      the arm adducted across the chest reaching for the opposite shoulder) and (4) shoulder
      internal rotation (CHD-IR) (Figure 2). Participants were asked to sit with their arms by
      their sides and to perform the 4 different positions respectively. The measurements were
      repeated for 3 trials with repositioning of the arm to a neutral position for intervals of 10
      seconds. The distance measured was that between the coracoid process and the lesser
      tuberosity of the humerus.

      SSP tendon thickness was evaluated with the patient's palm placed over his/her iliac wing, or
      "back pocket", with the elbow flexed and directed medially. The transducer was placed over
      the anterior aspect of the shoulder, perpendicular to the supraspinatus tendon and just
      anterior of the anterior-lateral margin of the acromion. A transverse glide was then
      performed at the site to determine the exact position where the observer judged that the
      tendon thickness was at its maximum. The thickness of the SSP tendon was measured 2 cm away
      from the biceps long head tendon. For measuring SSC tendon thickness with a short axis of
      view, the probe was positioned horizontally on the bicipital grove. The participant's forearm
      was placed with the elbow flexed to 90° in slight internal rotation, with the palm facing
      upward and medially. Then the patient was asked to rotate the forearm externally, keeping the
      palm up and the elbow strictly close to the iliac crest.

      Acrociohumeral distance (AHD) was measured under 0° and 60° of scapular plane shoulder
      elevation. The transducer was placed on the most anterior aspect of the acromion edge, with
      the long axis of the transducer placed in the plane of the scapula and parallel to the flat
      surface of the acromion. The participants sat in an upright position without back support and
      with their feet flat on the floor, holding their shoulders back and looking straight ahead,
      to achieve retracted shoulders and extension in the thoracic and cervical spine. AHD was
      measured at 0° and 60° of active shoulder elevation in the scapular plane. A 60° scapular
      elevation of AHD was then measured with a goniometer placed on the patient's arm to determine
      60° of active shoulder elevation, with the thumb pointing up.
    

Observational model: Case-Only
Time perspective: Cross-Sectional
Sampling method: Probability Sample
Study population: 
        Forty subjects whose age from 20 to 60 years old were recruited from National Taiwan
        University Hospital and through general local internet media. The inclusion criteria of
        subjects will be at least three positive of five tests, including Neer's test, Hawkin's
        test, Empty can test, tenderness in tendon of rotator cuff and resisted external test. In
        addition, participants with a history of shoulder dislocation, fracture or surgery, history
        of direct contact injury to the neck or upper extremities within the past month,
        glenohumeral joint instability (positive apprehension test, sulcus sign), neurologic
        disorder (upper motor neuron diseases, cervical radiculopathy), passive ER ROM less than 30
        degrees and pain (visual analogue scale, VAS less than 5) during the experimental tasks
        will be excluded.
      
Keywords: shoulder impingement syndrome; subcoracoid impingement; coracohumeral ligament distance; subscapularis