Kinetic chain concepts in shoulder dysfunctions

Alterations in shoulder kinematics in shoulder impingement:
Ludewig et al investigated (humeral elevation in the scapular plane); glenohumeral and scapulothoracic kinematics and associated scapulothoracic muscle activity in a group of subjects with symptoms of shoulder impingement relative to a group of subjects without symptoms of shoulder impingement matched for occupational exposure to overhead work. Their work revealed:

1. In subjects of impingement there is:
i. decreased scapular upward rotation at the end of the 1st of the 3 phases,
ii. increased anterior tipping at the end of the third phase, and
iii. increased scapular medial rotation under the load conditions.

2. EMG pattern in impingement cases showed hyperactivity upper and lower trapezius in the final 2 phases, although the upper trapezius muscle changes were apparent only during the loaded condition. The serratus anterior muscle demonstrated decreased activity in the group with impingement across all loads and phases.

Comparison of scapular kinematics between elevation and lowering of the arm in the scapular plane (3):
Abnormal scapular kinematics have been identified in shoulder impingement patients during the concentric phase of arm elevation, and under static conditions. Borstad et al compared scapular orientation during both the concentric (elevation) and eccentric (lowering) phases of scapular plane abduction in subjects with and without shoulder impingement. This study found:

1. Differences in scapular tipping and internal rotation during the eccentric phase of arm elevation were identified at higher humeral angles in both affected & unaffected groups. However these findings are not found in the lower angles.

2. Symptomatic group demonstrated significant reductions in upward rotation at lower humeral elevation angles, and significant increases in anterior tipping at higher elevation angles as compared to the healthy group.

The finding of this confirms the recommendation made by Ludewig et al (4) in 1996. They suggested assessment of scapular tipping and internal rotation as well as upward rotation may be necessary to understand pathologies of the shoulder that are related to abnormal scapular kinematics.

Kinetic chain approach: One of the important non-traditional approaches evolving now a day in rehabilitation of shoulder dysfunction is Kinetic chain approach. The fundamental of this approach is “body does not operate in isolated segment” rather it is a dynamic functional synsitium.

The kinetic chain approach addresses gleno-humeral motion through scapular control & scapular control through trunk movement. The flow of activity in this pattern is from the proximal to distal direction.

Concepts of kinetic chain shoulder rehabilitation are as follows (McMullen J, 2000; Journal of athletic training):
1. For shoulder rehabilitation to be truly functional, the approach to the upper extremity should follow proximal to distal pathway along a kinetic chain.

2. Muscle around the shoulder function synergistically & should be integrated within the kinetic link system through out the rehabilitation.

3. Scapular control & coordinated rotator cuff activation are vital to successful shoulder rehabilitation & safe shoulder function.

4. Graded close kinetic chain exercises for the upper extremity must be scheduled in the initial phase of the shoulder rehabilitation.

Close kinetic approach:
Closed-chain exercise protocols are used extensively in rehabilitation of knee injuries and are increasingly used in rehabilitation of shoulder injuries. They are felt to be preferable to other exercise programs in that they simulate normal physiologic and biomechanical functions, create little shear stress across injured or healing joints, and reproduce proprioceptive stimuli. Because of these advantages, they may be used early in rehabilitation and have been integral parts of "accelerated" rehabilitation programs (6).

Specific exercises for scapular control:
In a controlled laboratory study Kibler et al studied restoration of control of dynamic scapular motion by specific activation of the serratus anterior and lower trapezius muscles which are supposed to be important part of functional rehabilitation.

Specific action of 2 dymanic exercises lawnmower and robbery are studied. These specific exercises activate key scapular-stabilizing muscles at amplitudes that are known to increase muscle strength. These exercises can be used as part of a comprehensive rehabilitation program for restoration of shoulder function. They activate the serratus anterior and lower trapezius-key muscles in dynamic shoulder control-while variably activating the upper trapezius.

However the study also recommended inferior glide and low row can be performed early in rehabilitation because of their limited range of motion, while lawnmower and robbery, which require larger movements, can be instituted later in the sequence.

References:

1. McMullenJ et al; J Athl Train. 2000 Jul;35(3):329-337.
2. Ludewig PM et al; Phys Ther. 2000 Mar;80(3):276-91.
3. Borstad JD et al; Clin Biomech (Bristol, Avon). 2002 Nov-Dec;17(9-10):650-9.
4. Ludewig PM et al; J Orthop Sports Phys Ther. 1996 Aug;24(2):57-65.
5. Kibler WB et al; Am J Sports Med. 2008 Sep;36(9):1789-98. Epub 2008 May 9.
6. Kibler WB et al; J Am Acad Orthop Surg. 2001 Nov-Dec;9(6):412-21.