Altered glenohumeral kinematics in individuals with shoulder pain

Research Review: Altered glenohumeral kinematics in individuals with shoulder pain

By Stefanie DiCarrado DPT, PT, NASM CPT & CES

Edited by Brent Brookbush DPT, PT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Lawrence, R.L., Braman, J.P., Staker, J.L., Laprade, R.F., Ludewig, P.M. (2014) Comparison of 3-dimensional shoulder complex kinematics in individuals with and without shoulder pain, Part 2: Glenohumeral joint. Journal of Orthopaedic & Sports Physical Therapy 44(9). 646-B3 - ARTICLE

Note the available translations of the humeral head in normal mechanics.

Why is this relevant?: Shoulder impingement syndrome is one of the most common source of shoulder pain (1). Impingement related injury to the supraspinatus tendon, subacromial bursa, long head of the biceps tendon, and the anterior capsule can lead to tendonitis, tendon tear, or bursitis (2,3). Several treatment options exist for this syndrome: rest / reduce use of affected arm, general exercise, and/or manual physical therapy. To properly treat this condition and remove the underlying movement dysfunction (or prevent injury all together) one must understand the joint dyskinesis leading to impingement. The authors of this study performed a precise kinematic analysis of those with and without shoulder pain to better understand the mechanisms involved.

Study Summary

Posterior shoulder tightness tends to accompany an anterior superior migration of the humeral head further leading to altered kinetics and dysfunction.

Review & Commentary:

The strong methodology of this study stands out due to its 3-dimensional study of glenohumeral mechanics and its clear definition of impingement. Previous studies at the time of publications used only 2-dimensional GH translation data and did not examine motion at neighboring joints: acromioclavicular (AC), scapulothoracic (ST), and sternoclavicular (SC) . The researchers recruited symptomatic individuals as the experimental group and asymptomatic individuals as their controls, which strengthened the level of evidence provided, despite a small sample size. Subjects were deemed eligible based on clearly described, specific criteria and examined by a qualified physical therapist prior to testing.

Researchers clearly defined all outcome measures and data collection reference points. The authors collected motion data using sensors that were fixated into the subjects' humerus and scapula to minimize risk of error as surface markers are subject to soft tissue restrictions. As such, the authors reported low standards of error for GH angular motion and translations. See Altered Scapular Kinematics in Individuals with Shoulder Pain for a more detailed description of this study's strengths.

The authors listed the following limitations of the study: small sample size, differing arm dominance in AG & SG, and high variability between subject. In spite of the small sample size, results were consistent and statistically significant. Currently, there is nothing in the literature to suggest arm dominance impacts GH angular motion or translation during upper extermity (UE) motion. The variability between subjects limited pairwise comparisons but group comparisons remained strong. These limitations do not diminish the strength of these findings; however, it is important to note these results apply to the specific population studied. Although it is reasonable to examine these parameters in other populations with shoulder pain, one cannot, at this time, claim exact certainty that the data found here will apply to individuals with shoulder pain from causes other than impingement.

It would be interesting for future studies to include longitudinal data and note any asymmetries within the AG group that lead to future impingement and further altered mechanics. It is possible, as described in the sister article review (Altered Scapular Kinematics in Individuals with Shoulder Pain ) that individuals in the AG group did present with abnormal GH kinematics but with pain as the primary inclusion criteria, they were categorized as "healthy controls". Pain can cause altered mechanics and altered mechanics can cause pain, therefore both require further examination and research.

Why is this study important?

This study is important because, along with its sister article (Altered Scapular Kinematics in Individuals with Shoulder Pain ) discussing ST, SC, and AC involvement , it provides information on accessory motion in the shoulder complex using kinetic tracking fixated in the bone itself. Further, it provides this information on individuals with and without shoulder impingement, allowing the reader to understand normal and non-normal shoulder girdle biomechanics.

How does it affect practice?

Human movement specialists should analyse more than global osteokinematic motion of the shoulder complex (flexion, extension, adduction, etc.), and include analysis of optimal or compensatory arthrokinematic (glide, roll, spin, etc.) motion of involved joints during assessment. Optimal intervention for movement compensations includes both strategies specific to the muscular system, and joint specific intervention (for example, anterior to posterior mobilization of the glenohumeral joint).

• Addressing altered arthrokinematic motion is beyond the scope of personal trainers and massage therapists, except for a limited number of self-administered joint mobilization techniques (see videos below). However, noting alterations may provide information that is worthy of referral to a medical manual therapist (PT, ATC, DO, DC), and essential to your client's long-term success.

How does it relate to Brookbush Institute Content?

Movement compensations in upper extremity motion is noted in the predicted model of Upper Body Dysfunction  (UBD). Impingement syndrome is listed as an associated injury/pathology of this dysfunction.

As described in the UBD model, examining the position of the scapula is essential due to the relative motion of the humerus on the scapula. If the scapula adopts a resting position that includes excessive anteriorly tipping and/or downward rotation, the resting position of the humerus will be altered as well. Altered Scapular Kinematics in Individuals with Shoulder Pain describes the results of the scapular, SC, and AC joint motion in greater detail. Within this article, focusing on GH movement, the SG demonstrated greater inferior movement with HT elevation. This seems contradictory to previous findings of excessive superior translation (4). However, in the Brookbush UBD model, the scapula is subject to excessive downward rotation, therefore this inferior motion may be compensatory movement to create greater joint congruency.

Compensatory movements are further described in this article with increased osteokinematic motion of the glenohumeral (GH) joint when the individual demonstrated decreased scapulothoracic (ST) motion. During scaption, the syptomatic group (SG) showed more GH elevation along with decreased upward rotation of the scapula at both 30° & 60° of humerothoracic (HT) elevation. This increased GH movement with less scapular elevation can lead to decreased subacromial space during upper extremity (UE) motion which can lead to impingement of the structures therein. Decreased upward rotation of the scapula can result from overactivity in the downward rotators (levator scapulae , pectorialis minor, and rhomboids ) and inhibited upward rotators (serratus anterior , and the trapezius ). This is discussed in greater length, along with the effects of decreased scapular motion on the SC & AC joints, in the research review Altered Scapular Kinematics in Individuals with Shoulder Pain . The SG demonstrated increased humeral anterior translation during 90°-120° of HT elevation which supports previous research and will contribute to impinged subacromial structures. Overactivity of supraspinatus, subscapularis , and posterior deltoid and underactivity in the teres minor and infraspinatus would create excessive anterior translation as described in the predictive model of UBD .

To correct UBD  and correct or prevent pathology such as subacromial impingement, the Brookbush Institute recommends a corrective exercise strategy to self mobilize the GH joint, inhibit overactive muscles, activate underactive muscles and to integrate these groups into whole body movement via posterior oblique subsystem integration . The videos below demonstrate exercises to correct and prevent excessive anterior translation of the humeral head.

Subscapularis SA Static Release

Supraspinatus SA Static Release

Posterior Shoulder SA Static Release

Shoulder Mobilization

Posterior Shoulder Stretch Modifications (Sleeper Stretch on Wall)

Crucifixion Stretch (Static Pec Stretch, Sub-occipital Release & Gentle Thoracic Mobilization)

External Rotator Activation Progression

Prone Floor Cobra (and Chest-out/Thumbs-out)

Posterior Oblique Subsystem Integration (Squat to Row)

Sources

1. Van der Windt, D., Koes, B., de Jong, B., Bouter, L. (1995). Shoulder disorders in general practice: incidence, patient characteristics, and management. Annals of the Rheumatic Diseases. 54. 959-964

2. Leon Chaitow, Muscle Energy Techniques: Third Edition, © Pearson Professional Limited 2007

3. David G. Simons, Janet Travell, Lois S. Simons, Travell & Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition,© 1999 Williams and Wilkens

4. Shirley A Sahrmann, Diagnoses and Treatment of Movement Impairment Syndromes, © 2002 Mosby Inc.

© 2014 Brent Brookbush

Questions, comments, and criticisms are welcomed and encouraged -