External Rotation Strengthening With Manual Distraction for Individuals With Glenohumeral Osteoarthritis

Abstract

OSTEOARTHRITIS CAN LEAD TO MOVEMENT LIMITATIONS, WHICH ARE A BARRIER FOR STRENGTH TRAINING. IN SOME INSTANCES WHERE IMPROVED STRENGTH IS KNOWN TO DECREASE SYMPTOMS AND IMPROVE PATIENT REPORTED FUNCTION, THERE EXISTS A DIFFICULTY IN DEVELOPING TRAINING ROUTINES THAT ADDRESS THE WEAKNESS WITHOUT SYMPTOM AGGRAVATION. THIS ARTICLE AIMS TO DESCRIBE A TECHNIQUE TO DECREASE PAIN AND IMPROVE JOINT MOTION WHILE STRENGTHENING THE ROTATOR CUFF IN INDIVIDUALS WITH OSTEOARTHRITIS OF THE GLENOHUMERAL JOINT. A DESCRIPTION OF THE EXERCISE IS PROVIDED USING MANUAL DISTRACTION TO REDUCE COMPRESSIVE AND SHEAR FORCES WHILE ALLOWING FOR PAIN-FREE PERFORMANCE AND STRENGTHENING OF THE ROTATOR CUFF.

INTRODUCTION

Osteoarthritis is a degenerative disease that affects the integrity of the entire joint, including articular cartilage, tendons, ligaments, capsule, and bone (^5,7,14,15). While the direct causes of the disease are still debated, a relationship between high, repetitive, or abnormal mechanical stress and cartilage degeneration exists (^5,8,15). Joint forces can be affected by sustained postures or repetitive movements that create an imbalance of the supporting structures of the joint (^5,8,15). While research has favored muscle strengthening and exercise to improve movement patterns and reduce mechanical stress in osteoarthritic joints of the lower extremity, evidence for the glenohumeral joint is lacking, especially in the areas of pain and function (^1,5,13). While it is unclear whether muscle weakness, most notably the rotator cuff, is a cause or consequence of osteoarthritis, there is a notable correlation (^5,13,14). The rotator cuff, consisting of the supraspinatus, infraspinatus, teres minor, and subscapularis, functions as a force couple among the larger musculature, such as the deltoid, surrounding the shoulder girdle. This force couple allows for uniform compression and a reduction of sheer forces during physiologic shoulder motion (^3,6,12). Excess of these sheer forces lead to microtrauma of the cartilage and eventually macrotrauma characterized by visible arthritic changes, pain, and functional limitation (^10,14). Specifically, the external rotators (infraspinatus and teres minor) have been shown to assist in maintaining normal glenohumeral kinematics (⁴). Furthermore, impairments in the glenohumeral external rotators have been found in conditions thought to produce the repetitive microtrauma, such as impingement, which are a likely precursor to osteoarthritis in the shoulder (^4,5,9). Pain itself has been suggested to alter the sensorimotor system causing impairments in muscle strength and motor control (¹¹). Pain has been suggested, along with weakness and stiffness, to cause further alterations in mechanics and deterioration of the joint (^5,11,13). This creates a paradox for the client with osteoarthritis, with a condition that worsens with weakness, but an inability to strengthen the muscles or be active secondary to pain. The purpose of this article is to describe a technique using a distraction mobilization that could allow for reduced or pain-free strengthening of the rotator cuff of an osteoarthritic joint.

There are many exercises that strengthen the rotator cuff muscles. Careful considerations for exercises that minimize sheer forces and maximize rotator cuff recruitment are important for the osteoarthritic shoulder (^5,13,14). For the purposes of this article and describing a specific exercise most likely to reduce the sheer stress producing microtrauma at the glenohumeral joint, strengthening of the infraspinatus and teres minor will be discussed. These muscles are primary movers for external rotation and decrease anterior and superior translation of the humeral head (^3,6,12,13). The exercise (see Video, Supplemental Digital Content 1, https://links.lww.com/SCJ/A156) performing external rotation at approximately 30° of abduction was chosen for multiple reasons. First, the infraspinatus and teres major demonstrate their greatest moment arm with slight humeral abduction using a towel roll (^3,12). Biomechanical analysis and electromyographic studies have also demonstrated maximal muscle recruitment in this position from these muscles compared with higher degrees of abduction (^3,12). Second, this position reduces the need for dynamic control of the scapulothoracic joint (¹²). Many studies have shown poor scapulohumeral control in those presenting with pain and range of motion restrictions (¹¹). By reducing the potential for scapulohumeral impairments, there can be added focus on the correct rotation of the humeral head within the glenoid until the client can progress to more functional exercises that may mimic the client's daily or desired recreational activities. An example of impingement syndromes helps to explain the importance of positioning for this exercise, as well as in describing the important function of the muscles that are addressed during this technique. Subacromial impingement can be characterized by weakness of the rotator cuff musculature and movement impairments of excessive superior glide of the humerus during shoulder flexion or abduction (^2,12). The importance of strengthening the rotator cuff is highlighted in the treatment of the movement impairments seen with impingement. In addition, the joint positions chosen for this exercise have been shown to reduce movements associated with impingement, while maximizing muscle recruitment (^3,12). While evidence demonstrating a direct association between impingement syndromes and osteoarthritis is lacking, one can see the link between rotator cuff weakness, impingement, and the potential cartilage destruction associated with osteoarthritis through an understanding of abnormal movement patterns and its effect on the joint (⁵). It is, therefore, important to not only address the osteoarthritic joint with an exercise that maximizes muscle recruitment but that also maximizes correct joint mechanics and reduces mechanical stress.

Performing the exercise (right glenohumeral external rotation with distraction):

• Secure the resistance (elastic resistance band or cable weight stack) to the left of the client at the height of the umbilicus.
• Position the arm in the plane of the scapula using a towel roll, 30° of abduction and 30° of flexion with the elbow flexed to 90° to allow easy access for distraction while maximizing posterior muscle activity. The forearm may be placed 30° below the horizontal plane for comfort (Figure 1A).
• The client should externally rotate the glenohumeral joint as far as they can without substitution and then return to the starting position (Figure 1B).
• Do not allow substitutions such as glenohumeral elevation or horizontal abduction and trunk rotation during the motion (Figure 2B).
• The resistance should be present at the starting position and remain throughout the entire motion.
• Both concentric movement into external rotation and the eccentric return to slight internal rotation should be at a speed that allows for correct performance without substitution or compensatory movement at the glenohumeral and scapulothoracic joints.
• The glenohumeral joint should remain in the plane of the scapula with care taken to prevent scapula dyskinesia during the motion (Figure 2A).
• The optimal resistance will be dependent on the phase of participation and individual characteristics of the client. The resistance level should be one that can be performed without participant discomfort or substitution.

Figure 1: (A and B) Starting and ending position. Position the arm in the plane of the scapula using a towel roll, 30° of abduction and 30° of flexion with the elbow flexed to 90° to allow easy access for distraction while maximizing posterior muscle activity. The forearm may be placed 30° below the horizontal plane for comfort.

Figure 2: (A) Scapulothoracic joint positioned in neutral and should not deviate during the exercise: A1, with shirt; A2, without shirt. (B) Glenohumeral joint positioned in the plane of the scapula and should not deviate during the exercise.

Adding distraction:

• The rehabilitation provider will place the web space of one hand under the arm as close to the axillary fold as possible while taking care to prevent compression of the neurovascular structures, such as the brachial plexus and the brachial artery. The opposite hand should be placed on the lateral side of the elbow (Figure 3A).
• The client will start in slight internal rotation, with their hand in front of their umbilicus and the forearm in pronation. Apply a distractive lateral force with the hand in the axilla and instruct the client to slowly rotate the arm clockwise, into external rotation, while maintaining an adduction force into the towel. An adduction force can be added with the opposite hand at the elbow to create an increased fulcrum for distraction (Figure 3B). See Supplemental Digital Content 1 (see Video, https://links.lww.com/SCJ/A156) for a video demonstration of this exercise.

Figure 3: (A and B) Lateral distraction is applied manually throughout the motion of glenohumeral external rotation. Care is taken not to place excessive compression on the neurovascular structures of the medial arm.

Optional modification (Figure 4)

• Clients with balance impairment may benefit from performance of this technique while sitting (Figure 4A and 4B).
• The client should have adequate trunk stability since the hip musculature is limited in their ability to stabilize in this position.
• Care should be taken to prevent rotation of the trunk and a chair may be used to prevent compensatory trunk movement.

Figure 4: (A and B) Modification of the exercise and mobilization technique to sitting.

The success of this technique depends on the severity of osteoarthritis including the anatomical positioning of degeneration, the available range of motion of the joint, and the proficiency of the provider in performing the technique. The distraction component of the exercise is a joint mobilization technique and thus should only be performed when it falls within the professional purview of the provider, and when applicable, within their jurisdictional scope. There are many other considerations for the success of this technique, including but not limited to scapular humeral rhythm, postural alignment, and other rotator cuff and periscapular muscle performance. The distraction with strengthening technique can be modified to address these impairments as well.

In conclusion, osteoarthritis is a degenerative disease, which causes restrictions in motion and pain. Conservative management can be difficult and is understudied in this population. For client's wishing to avoid surgery or those interested in maximizing strength and motion before surgery, distraction with strengthening is an alternative. Distraction not only decreases compressive forces but is also beneficial to the surrounding synovia, which is important for joint nutrition and the inflammatory process (^7,8,10). While exercise has not been shown to reverse existing degeneration of cartilage, stress within normal mechanics and under acceptable tissue loads can promote remodeling of injured tissue and perhaps prevent progression of the disease process (^7,8). Perhaps most importantly, by strengthening the appropriate muscles and controlling for repetitive abnormal and excessive mechanical stress on the tissues, one could theoretically break the cycle of degeneration and subsequent pain and functional limitation in these individuals (¹⁵).