1 Effects of Stabilization Exercises on the Acromioclavicular Joint Jeremy Will; Danny Smith; Brandon Brill; Case Ruckman October 21, 2011 Advisor: Daniel Haun, D.C.
2 Abstract: Introduction: The acromioclavicular joint is an important link between the upper extremity and the axial skeleton. The acromioclavicular joint is an inherently unstable joint that is predisposed to injuries, especially in athletes and those people that are required to do most of their work overhead. The dominant feature of acromioclavicular joint instability is a widening of the articular surfaces. The purpose of this study was to evaluate the changes in acromioclavicular joint width after a four week exercise program utilizing isometric stabilization exercises. Methods: The research utilized eight college students that were physically active recreationally or had participated in collegiate athletics in the past. The exercises focused on scapular and rotator cuff stability with the goal of enhancing muscular control that would have a direct effect on the movement of the acromioclavicular joint. Results: This study demonstrated no differences in the mean widths of the acromioclavicular joint when compared to pre and post measurements determined using diagnostic ultrasound. Conclusions: The outcome of this study may have been more significant had an ideal population consisting of athletes or laborers that typically work overhead been recruited due to a higher likelihood of having significantly wider, and therefore unstable, acromioclavicular joint.
3 Introduction: of the humerus in the glenoid cavity (1) which forms the link of the upper extremity to the axial skeleton.(2) The joint is primarily supported by the coracoclavicular ligament and is surrounded by a fibrous capsule with an articular disc within the joint(1). The intra-articular, fibrocartilaginous joint helps to absorb compression(2) which is greatest in its closed packed position at 90o of abduction.(1) The acromioclavicular joint (ACJ) acts like a pivot between the clavicle and scapula, allowing for increased arm rotation above 90o of abduction.(3) The meniscus of the ACJ is poorly understood, and little is known of its biomechanical role. The ACJ has similar morphology to the sternoclavicular joint but more commonly has an incomplete fibrocartilaginous disc which may be one of the reasons why degenerative changes affect this joint more frequently than they do the sternoclavicular joint.(4) The ACJ is surrounded by a thin capsule that is reinforced above and below by the superior and inferior AC ligaments and the anterior and posterior ligaments. Acromioclavicular stability is maintained by the coracoclavicular ligaments (conoid and trapezoid) in addition to the AC capsule.(4) The relationship between the clavicle and scapula may also be influenced by the muscular attachments to the scapula and the role they play in proper scapular motion. The scapulothoracic articulation represents a space between the convex surface of the posterior thoracic cage and the concave surface of the anterior scapula.(5)It’s muscular and bursal structures allow a relatively smooth motion of the scapula on the underlying scapula with the scapula serving as the bony foundation of the shoulder girdle allowing for increased shoulder movement beyond the limitations of the glenohumeral joint.(5) Seventeen muscles attach to or originate from the scapula and function to stablizie the scapula and provide motion.(5) Among these, the most important are the serratus anterior, which maintains the medial angle against the chest wall, and the trapezius, which helps to rotate and elevate the scapula synchronously with glenohumeral motion.(5) The clavicle does rotate, but the scapula rotates with it, so that there should be relatively little relative motion of the clavicle and scapula. Thus, the most scapulothoracic motion occurs through the sternoclavicular joint.(4) The clinical significance of this is that ACJ fixation may be rigid without necessarily producing an obligate loss of shoulder motion.(4) In normal subjects, the ACJ width should be no wider than 6 mm and the acromioclavicular index 1.0.(6) Injury to the joint can cause an increase in width of the joint and an increased acromioclavicular index leading to joint instability and excessive joint motion. Injuries to the ACJ are very common in athletes and a source of significant morbidity.(4) AC pathology particularly affects athletes whose sport demands overhead upper limb activity which are most commonly encountered in contact sports.(4) The importance of identifying the injury type cannot be overemphasized because the treatment and prognosis hinge on an accurate diagnosis. The injuries are graded on the basis of which ligaments are injured and how badly they are torn.(2) According to the Rockwood classification of acromioclavicular joint injuries, there are six major types graded I-VI(6): The acromioclavicular joint is a plane, synovial joint that augments the range of motion
4 TYPE CHARACTERISTICS: I - Sprain of acromioclavicular ligament only II- Acromioclavicular ligaments and joint capsule. Disrupted Coracoclavicular ligaments intact. 50% vertical subluxation of clavicle. III- Acromioclavicular ligaments and capsule disrupted. Coracoclavicular ligaments disrupted. Acromioclavicular joint dislocation with clavicle displaced superiorly and complete loss of contact between clavicle and acromion. IV- Acromioclavicular ligaments and capsule disrupted. Coracoclavicular ligaments disrupted. Acromioclavicular joint dislocation and clavicle displaced posteriorly into or through trapezius muscle (posterior displacement confirmed on axillary radiograph) V- Acromioclavicular ligaments and capsule disrupted. Coracoclavicular ligaments disrupted. Acromioclavicular joint dislocation with extreme superior elevation of clavicle (100 to 300% normal). Complete detachment of deltoid and trapezius from distal clavicle. VI- Acromioclavicular ligaments and capsule disrupted. Coracoclavicular ligaments disrupted. Acromioclavicular joint dislocation with clavicle displaced inferior to acromion and coracoid process Primary osteoarthritis more commonly affects the ACJ than the glenohumeral joint, while post-traumatic ACJ arthritis is even more prevalent due to high incidence of injury to the joint.(7) Arthritic symptoms have been demonstrated in Grade I and Grade II ACJ sprains 8% and 42%, respectively.(7) Osteoarthritis is the most common cause of shoulder pain originating from the ACJ, and is a frequent finding in patients older than 50 years of age.(8) Scapular dysfunction might occur in response to inappropriate or deficient training habits, traumatic injury, microtrauma-induced muscle strains that affect normal scapulohumeral rhythm or inhibition caused by shoulder pathology.(10) Scapular stabilization prescription should begin with isometric or closed chain exercises. Prescribing closed chain exercises for the scapula is recommended early in rehabilitation as the best exercise mode to improve scapular motor patterns.(11) Isometric exercises, such as scapular retraction, allow for early neuromuscular reeducation of dysfunctional rhomboids and the middle trapezius.(11) Proper scapular kinesis and muscular balance will allow for more stability at the ACJ, allowing for better joint dynamics between the scapula and clavicle. The clinical features of arthritis of the ACJ may mimic those observed in arthritis of the shoulder. The advantages of ultrasonography include the absence of ionizing radiation, short examination time, low cost, and non-invasive character.(9) Ultrasound of the ACJ can easily demonstrate a distended joint capsule, bone irregularities, joint space distances, and dislocation of the ACJ.(9)
5 Materials and Methods: Nineteen college students will undergo diagnostic ultrasound which will be utilized to measure the width of the acromioclavicular joint. They are all physically active recreationally and in good health. All research participants denied a history of glenohumeral joint dislocations, rotator cuff tears, or labral tears. They also denied any recent history (past six months) of a fracture to either the clavicle or scapula or upper extremity. Motion, using diagnostic ultrasound, will be observed and recorded as the subject performs forearm flexion with internal rotation at the glenohumeral joint bringing the hand to the opposite shoulder and then returning to a resting position. After measurements have been taken, an interventional exercise program will be implemented consisting of eight scapular stabilization exercises. The isometric exercises to be performed include, isometric flexion of the shoulder while the arm remains in a neutral position at the subject’s side using a Theraband of medium resistance (see Diagram A). The participant will walk out from a stationary point with the Theraband anchored, increasing the resistance as the distance from the anchor point is increased. Beginning with only slight tension on the medium resistance Theraband, the subject will increase the distance to approximately five feet which will increase the resistance on the Theraband to approximately 12-13 lbs at its peak. The subject will repeat this exercise five times for a total five sets. Diagram A: (A) (B) The patient will repeat this process with for extension, internal rotation, and external rotation, with the subject’s arm flexed to 90o for internal and external rotation (see Diagrams B and C). Figure (A): Start Position for flexion isometric exercise; Figure (B): End position Process will be repeated with the patient facing the wall for isometric extension resistance.
6 Diagram B: (A) (B) Diagram C: Figure (A): Start position for isometric internal rotation; Figure (B): End position (A) (B) into a bench while in a squat position on the affected arm using it for stabilization. This three point stance will be held while the opposite, unaffected arm is flexed and extended increasing the propioceptive input in the stabilizing shoulder. This will be performed three times with 15 repetitions of flexion and extension of the opposite arm (see Diagram D). Figure (A): Start position for isometric external rotation; Figure (B): End position The next exercise is an isometric stabilization exercise in which the participant will lean
7 Diagram D: (A) (B) crouching position on their knees and elbows. The subject will be instructed to keep a neutral spine while trying to extend their back at the T4 level of the thoracic spine while retracting the scapulae. Proper verbal cues and supervision of the exercise will be conducted by the researchers to ensure correct form and muscular activation. This will be performed three times for 30 seconds duration (see Diagram E). Diagram E: Figure (A): Starting position; Figure (B): end position Note: affected arm for subject in diagram will be left arm which is the stabilization arm. The third exercise will be the T4 extension in which the participant is placed into a protocols and new measurements will be recorded for comparison. T4 Extension Exercise Upon completion of the exercise intervention, subjects will repeat the initial ultrasound Results (Data): the exercise protocols or failed to report for the follow up measurements. The remaining 8 collegiate students who completed the study showed no significant reduction in the pre and post measurements following the interventional isometric exercise protocols. The average width of There was a 63% fallout rate for this study with 12 participants either failing to complete
8 the participant’s ACJ prior to the study was determined to be 6.1 mm (+ 2.3) in the neutral position and a width of 3.7 mm (+ 1.3 mm) in the cross arm position. Following the four week exercise program, the width at neutral position measured 6.3 mm (+ 2.3mm) and 3.9 mm (+ 1.2 mm) in the cross arm position for a pre and post difference of 0.1 mm (+ 0.8). Post Cross- arm 0.33 0.30 0.24 0.40 0.62 0.46 0.46 0.33 Pre Cross- arm 0.31 0.25 0.23 0.44 0.46 0.59 0.43 0.28 Subject 1 2 3 4 5 6 7 8 Initials CG BC JW DS NW JT KD BW Side R R R R R R R R Neutral 0.43 0.46 0.32 0.58 0.71 1.01 0.54 0.85 Difference Neutral 0.12 0.21 0.09 0.14 0.25 0.42 0.11 0.57 Difference 0.13 0.17 0.13 0.12 0.20 0.57 0.10 0.44 Pre-Post Difference -0.01 0.04 -0.04 0.02 0.05 -0.15 0.01 0.13 0.46 0.47 0.37 0.52 0.82 1.03 0.56 0.77 MEAN SD 0.61 0.23 0.37 0.13 0.24 0.17 0.63 0.23 0.39 0.12 0.23 0.17 0.01 0.08 Table 1: comparison of pre- and post-assessment of width of acromioclavicular joints of research participants. Discussion: + 2.3mm) of the ACJ at rest and a width of 3.9 mm (+ 1.2 mm) in the cross-arm position on post- assessment. These results show a difference of 0.1 mm (+ 0.8 mm) from the initial measurements. These measurements allow for the examiners to view any excessive widening of the ACJ both at rest and after applying an active stress to the joint. The average width of the participants in this study (6.1mm) are consistent with the previously established average width of 3-6 mm.(6) The results of this study do not support our initial hypothesis that suggested a measurable reduction in the width of the ACJ after having participated in the research protocols. The isometric exercises resulted in a statistically insignificant amount of change from the pre- exercise measurements to the post-exercise measurements. The supervised rehabilitation exercises were one of the strengths of this study. Twice a week for four weeks participants were put through supervised exercises which included isometric flexion and extension exercises, along with internal and external rotation, and shoulder stabilization exercises. Each week the exercises were performed in a supervised setting that included monitoring each subject’s repetitions and were able to correct any improper form or movement patterns or poor form. Another strength was the use of diagnostic ultrasound to The sample of participants in this study present with an average width of 6.3 mm (SD of
9 measure the amount of motion in the acromioclavicular joint of each participant. This made it possible to make precise measurements in order to have valid and comparable pre and post exercise regimen data. It also provided the opportunity to view the anatomy of the acromioclavicular joint before the participants were taken through the exercise regimen. This allowed the researchers to rule out any anatomical contraindications to exercise, and reinforced the safety of each participant. In order for our study participants to get diagnostic ultrasounds, two doctors performed the diagnostic ultrasounds. The inter-user reliability of diagnostic ultrasound could have caused some pre and post exercise measurements to have been skewed. Also, during the cross arm maneuver of the diagnostic ultrasound, some participants may have lifted their elbows higher during the movement than others, causing more motion at the joint. The use of width measurement of the ACJ as the only statistical outcome was also a limit of this study. It may have yielded more in depth and telling results, had range of motion of the upper extremity been assessed. Due to the time obligation and failure to complete participation, only 10 subjects completed the entire exercise program. It is understood that this is a small sample size and does not provide enough data for a generalization to a larger population to determine if there would be beneficial effects of these exercises. Also, the participants in the study were chosen out of convenience and were all young adults in their mid twenties, which is not the ideal sample size for the study. Conclusion: A course of stabilization exercised had no effect on acromioclavicular joint width or acromioclavicular joint stability as measured with ultrasound. To better perform a study like this in the future one would need to determine who the single person to perform the diagnostic ultrasounds is, and to have each participant perform the same exact motion. This will provide a more accurate measurement for each participant and therefore provide more accurate results. A larger sample size, including a wider age range, would also increase the validity of the study. Strength measurements of each patient could be performed to see how strong they are in each plane (flexion, extension, internal and external rotation) which would provide a base strength that could be compared to post-exercise regimen strength. Also, the duration of the study, and the frequency of exercises could be adjusted in order to create a comparison between this study and future studies.
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