- Email: [email protected]
Scapular Dyskinesis and SICK Scapula Syndrome in Patients With Chronic Type III Acromioclavicular Dislocation
Scapular Dyskinesis and SICK Scapula Syndrome in Patients With Chronic Type III Acromioclavicular Dislocation Stefano Gumina, M.D., Ph.D., Stefano Carbone, M.D., and Franco Postacchini, M.D., Ph.D.
Purpose: This study was aimed at evaluating whether scapular dyskinesis and, eventually, SICK (Scapular malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement) scapula syndrome develop in patients with chronic type III acromioclavicular (AC) dislocation. Methods: Scapulothoracic motion was studied in 34 patients with chronic AC dislocation by use of the protocol described by Kibler et al. and Burkhart et al. An anteroposterior radiograph of the scapulae with the arms abducted was also obtained. The SICK Scapula Rating Scale was applied to patients with SICK scapula syndrome. Shoulder function was assessed with the Constant score and Simple Shoulder Test (SST). Results: Of the 34 patients, 24 (70.6%) had scapular dyskinesis with the arms at rest, and 14 of these (58.3%) had SICK scapula syndrome. The mean SICK Scapula Rating Scale score was 6.9 points (out of a possible 20 points). Clinical and radiographic evaluations with the arms abducted at 90° confirmed scapular dyskinesis in 61.7% and 64.7% of patients, respectively (P ⬎ .05). The Constant score was 83 points for the pathologic side and 91 points for the contralateral side. The Constant score value was 75 and 88, respectively, in patients with dyskinesis and those without dyskinesis (P ⬍ .05); the mean value for the SST was 8 of 12 and 10 of 12, respectively. Conclusions: Chronic type III AC dislocation causes scapular dyskinesis in 70.6% of patients. Of the latter, 58.3% have SICK scapula syndrome develop. Dyskinesis might be due to loss of the stable fulcrum of the shoulder girdle represented by the AC joint and due to the superior shoulder pain caused by the dislocation. The values for the Constant score and SST were lower in patients with dyskinesis. Level of Evidence: Level IV, prognostic case series. Key Words: Acromioclavicular joint dislocations—Type III acromioclavicular separation— Scapular dyskinesis—SICK scapula syndrome.
A
cromioclavicular (AC) joint injuries are common, especially in athletes. They represent 12% of dislocations at the shoulder girdle and 8% of all joint dislocations in the human body.1 The AC joint stabilizes the scapula in relation to the clavicle by means of a complex of ligaments and muscles. Although the clavicle rotates upward 40° to 50° during
From the Department of Orthopaedic Surgery, University “La Sapienza,” Rome, Italy. The authors report no conflict of interest. Received April 24, 2008; accepted August 27, 2008. Address correspondence and reprint requests to Stefano Carbone, M.D., Department of Orthopaedic Surgery, University “La Sapienza,” Piazzale Aldo Moro, 5, 00100, Rome, Italy. E-mail: [email protected] © 2009 by the Arthroscopy Association of North America 0749-8063/09/2501-8221$36.00/0 doi:10.1016/j.arthro.2008.08.019
40
full overhead elevation, only 5° to 8° of motion occur in the AC joint.2 This difference is the result of “synchronous scapuloclavicular” motion: as the clavicle rotates upward, the scapula rotates downward, and AC joint motion thereby decreases. This synchrony is coordinated by the coracoclavicular ligaments. Joint dislocation usually results from a direct blow to the acromion with the arm adducted. The classification of AC injuries is based on the type of anatomic lesion, as well as the direction and amount of clavicular displacement. The Rockwood classification, which is the most commonly used system, includes 6 types of injury of increasing severity.3 This classification defines the extent of injury and helps in the management of AC joint injuries. Generally, types I and II are treated conservatively with immobilization, ice, and nonsteroidal drugs.4 On the other hand, types IV, V, and VI almost always require surgical treat-
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 25, No 1 (January), 2009: pp 40-45
SICK SCAPULA SYNDROME ment.4 The management of type III dislocation, characterized by complete AC and coracoclavicular ligament tears, as well as coracoclavicular interspace greater than 25% to 100% of that in the normal shoulder, is controversial, although several prospective, randomized, controlled trials have shown that the results of conservative treatment are better than those of surgery.4-7 On the contrary, a recent study states that surgical reconstruction guarantees better outcomes.8 Bagg and Forrest9 observed that AC joint injuries associated with clavicle instability or osteoarthritic changes of the joint interfere with clavicular function and can affect scapular kinematics by not allowing the normal progression of the instant center of scapular rotation from the medial scapular border to the AC joint. Scapular dyskinesis is an alteration of the normal position or motion of the scapula during coupled scapulohumeral movements. It occurs after a large number of injuries involving the shoulder joint and is often a cause of shoulder pain.10 Warner et al11 found alterations of the scapular position and motion in 68% to 100% of patients with a history of shoulder injuries. Three-dimensional biomechanical analysis of scapular motions shows that the scapula moves around 3 axes of motion simultaneously.12,13 Abnormal motion patterns in scapular dyskinesis are best detected by first determining the position of the scapula with the patient’s arms at rest and then observing the scapular motion as the arms are elevated and lowered in the scapular plane. These dyskinetic patterns fall into 3 categories, characterized by the prominence of the inferomedial border of the scapula (type I), the entire medial border (type II), or the superomedial border (type III).14 Recently, Burkhart et al.15 have related the disabled throwing shoulder to a particular overuse muscle fatigue syndrome: “the SICK scapula.” The acronym SICK stands for Scapular malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement. The main feature of this syndrome is the malposition of the scapula in the dominant throwing shoulder, which appears to be lower than the contralateral shoulder. Symptomatic patients may complain of anterior shoulder pain in the region of the coracoid, posterosuperior scapular pain with or without radiation to the paraspinous neck region or proximal lateral arm, superior (AC joint) shoulder pain, or radicular symptoms.15 The authors have examined their overhead throwing athletes with 3 superficial landmark measurements of the scapula and have devised a grading system for the severity of scapular malposition.
41
In this study we have analyzed patients with chronic unreduced type III AC dislocation to determine whether scapular dyskinesis and, eventually, SICK scapula syndrome had developed. The kinematics of the involved scapulothoracic joint was studied to understand why some patients with an AC joint dislocation complain of pain in the AC joint, periscapular muscles, and scapulovertebral region. We hypothesized that this pain and the altered AC joint anatomy may interfere with the scapulothoracic rhythm. To our knowledge, this is the first study on the effects of a longstanding type III AC dislocation and on the biomechanics of the scapulothoracic joint. METHODS Between 2004 and 2007, 62 patients with radiographic evidence of type III AC dislocation were treated at our emergency department. Of these, 53 were treated conservatively whereas 9 underwent arthroscopic or open reduction of the dislocation. Twelve patients were excluded from the study for one of the following reasons: previous shoulder injury, associated neurologic deficit on the side of the lesion occurring at the time of dislocation, and age over 70 years at the time of follow-up. Patients with AC osteoarthritis were also excluded because, although it occurs rarely, they already had a painful shoulder before the injury. Seven additional patients could not be traced. All of the remaining 34 patients included in the study group had been treated with a figure-of-8 splint for a mean of 4 weeks and early motion of the upper limb. Thereafter, all patients followed a rehabilitation program for a mean period of 3 weeks. None had sustained other significant shoulder injuries within the follow-up period. There were 32 male and 2 female patients, aged 24 to 69 years (mean, 47 years) at the time of follow-up. The mean time interval between injury and follow-up was 28 months (range, 12 to 36 months). Scapulothoracic motion was separately evaluated by all of the authors. According to the protocol of Kibler et al.10,14 and Burkhart et al.,15 scapular position was first analyzed with the arms at rest (position 1). In this position we evaluated (1) the difference in height (in centimeters) of the superomedial scapular angle between the injured and contralateral scapulae, (2) the difference in the distance (in centimeters) of the superomedial scapular angle from the body midline between the injured and contralateral sides, and (3) the difference in angular degrees, measured with a goniometer, of the medial scapular border from the
42
S. GUMINA ET AL. Once scapulothoracic dyskinesis was diagnosed, we trained patients to follow the protocol described by Kibler and McMullen10 for rehabilitation of scapular dyskinesis, which emphasizes achieving full and appropriate scapular motion and coordinating that motion with complementary trunk and hip movements. The rehabilitation program reported by Burkhart et al.15 was adopted for patients with SICK scapula syndrome. Data are presented as means and were analyzed with the nonparametric Wilcoxon test. P ⬍ .05 was selected to indicate a statistically significant difference. RESULTS
FIGURE 1. First measurement: Difference in vertical height of superomedial scapular angle of injured scapula (A) compared with contralateral superomedial angle (B) (measured as number of centimeters from a to b) in position 1. Second measurement: Distance of superomedial scapular angle (A, B) from midline in injured and contralateral scapulae (centimeters from A to a minus centimeters from B to b). Third measurement: Difference in angular degrees of medial scapular margin from plumb midline between injured scapula (angle ␣) and contralateral scapula (angle ) measured with goniometer.
plumb line between the injured and contralateral scapulae (Fig 1). Considering 1.5 cm or 5° asymmetry as the threshold for abnormality in each measurement,15,16 we obtained the percentage of patients with scapular dyskinesis. If abnormalities were noted, we ascribed them to 1 of the 3 patterns of scapular dyskinesis described by Kibler et al.14 A history of coracoid pain was recorded, and coracoid position was assessed. For evaluating the severity of SICK scapula syndrome, we applied the SICK Scapula Rating Scale to patients who had scapular dyskinesis, inferior medial border prominence, and coracoid pain and malposition.15 This scale is based on measurements comparing the 2 scapula and investigating the subjective and objective pain of the injured shoulder. Subsequently, scapular position was assessed with the arms abducted at 90° and internally rotated, the elbows in full extension, and the hands holding a weight of 2 kg (position 2) by use of the same parameters described previously. To verify the reliability of clinical measurements, an anteroposterior radiograph of both scapulae was obtained in position 2, and the same measurements carried out on the patient’s body were made (Fig 2). Finally, we evaluated shoulder function with the Constant score17 and Simple Shoulder Test (SST).18
In position 1 the difference in vertical height of the superomedial scapular angle of the scapula between the injured and contralateral sides was 2.1 cm on average (range, ⫺1 to 4.5 cm; P ⫽ .014). The mean difference in the distance of the superomedial scapular angle from the midline between the side with AC dislocation and the contralateral side was 0.5 cm (range, ⫺2 to 2 cm; P ⫽ .208). The difference in angular degrees of the medial scapular margin from the plumb midline between the injured and contralateral scapulae was 8° (range, ⫺10° to 10°; P ⫽ .041). Of 34 patients, 24 (70.6%) had scapular dyskinesis, with a Kibler type I pattern (prominence of inferomedial border) in 17 (70.8%) (Fig 3), type II pattern (prominence of entire medial border) in 3 (12.5%) (Fig 4), and type III pattern (prominence of superomedial border) in 4 (16.6%) (Fig 5).14 SICK scapula syndrome was observed in 14 (58.3%) of the patients with scapular dyskinesis (Fig 6); the percentage was 41.2% if all 34 patients were considered. The mean
FIGURE 2. Anteroposterior radiograph of 2 scapulae with arms abducted at 90°, used to evaluate same parameters assessed on clinical examination.
SICK SCAPULA SYNDROME
43
FIGURE 5. Patient with chronic type III AC joint dislocation on right side and type III pattern of dyskinesis (prominence of superomedial border).
FIGURE 3. Patient with chronic type III AC dislocation on left side and type I pattern of dyskinesis (prominence of inferomedial border of scapula).
score on the SICK Scapula Rating Scale in the 14 patients with SICK scapula syndrome was 6.9 points (out of a possible 20 points) (range, 4 to 15 points) (with ⬍5 points in 2 cases, 5 to 10 points in 9 cases, and ⬎10 points in 3 cases). In position 2 the difference in height of the superomedial scapular angle between the affected and contralateral sides was 1.5 cm on average (range, ⫺1 to 3 cm; P ⫽ .032); the mean distance between the
FIGURE 4. Patient with chronic type III left AC dislocation on left side and type II pattern of dyskinesis (prominence of entire medial border). (Hypertrophy of the trapezius muscle does not allow AC dislocation to be appreciated.)
superomedial scapular angle and the midline was 1 cm (range, 0 to 2.6 cm; P ⫽ .142) greater on the injured side than on the contralateral side; and the angle formed by the medial scapular margin and the plumb midline was 8° (range, ⫺8° to 18°; P ⫽ .047) greater on the injured side. On the basis of these measurements, 21 patients (61.7%) were found to have scapular dyskinesis. At radiographic evaluation, the mean difference in height of the superomedial scapular angle between the injured scapula and the contralateral scapula was 1.7 cm (range, ⫺2 to 3 cm; P ⫽ .029); the mean difference in the superior scapular angle from the midline between the injured and opposite sides was 0.8 cm (range, ⫺2 to 3.3 cm; P ⫽ .208); and the difference in the value of the angle formed by the medial scapular margin and the plumb midline was 5° (range, ⫺8° to 11°; P ⫽ .049) between the injured and contralateral scapulae. On the basis of the radio-
FIGURE 6. Patient with chronic type III AC dislocation on right side and SICK scapula syndrome.
44
S. GUMINA ET AL.
graphic results, 22 patients (64.7%) had scapular dyskinesis. However, the comparison of clinical to radiographic measurements with the arms abducted at 90° did not show a statistically significant difference (P ⫽ .47). No significant differences emerged when comparing the measurements performed by the 3 authors (P ⫽ .052 to .124). The mean Constant score was 83 points (range, 54 to 94 points) for the injured side and 92 points (range, 88 to 100 points) for the healthy side (P ⫽ .0087 for comparison of the 2 groups). Patients with dyskinesis examined in position 1 (n ⫽ 24) had a score of 75 points on average (range, 54 to 80 patients) on the injured side, whereas patients with normal scapulothoracic motion (n ⫽ 10) had a mean score of 88 points (range, 75 to 94 points). Comparison of the Constant score in the last 2 groups of patients showed a statistically significant difference (P ⫽ .01). The mean SST score in the entire study group was 9 (out of a possible 12) (range, 6 to 12), with SST scores of 8 and 10 in patients with dyskinesis and those without dyskinesis, respectively. DISCUSSION In previous studies patients with shoulder pain caused by different pathologic conditions were found to have scapular dyskinesis.10 However, we could not find any studies on the changes in scapulothoracic motion as a result of type III AC joint dislocation. According to Kibler et al.,14 scapulothoracic position and motion should be studied using clinical measurements carried out first with the arms at rest and then with the arms abducted at 90° and internally rotated and elbows in full extension. We adopted this method, and in addition, we performed measurements on anteroposterior radiographs of the shoulders with the arms in abduction, because we thought that they might be more accurate than clinical measurements. However, no statistically significant difference was found between the values obtained with the arms at rest and those with the arms abducted or those calculated on the radiographs. These findings suggest that scapular dyskinesis can be detected based solely on the data obtained with the arms at rest (position 1). They also indicate that measurements on radiographs do not provide further information on scapular position. In this study 70.6% of patients with chronic AC dislocation had scapular dyskinesis, and more than two thirds of them had a prominence of the inferomedial border of the scapula. This abnormality of scap-
ular position was classified by Kibler et al.14 as a type I pattern and was attributed to inflexibility of the pectoralis major and minor, as well as to the weakness of the lower trapezius and serratus anterior.14,15 This biomechanical hypothesis may also explain the development of scapular dyskinesis in patients with a chronic AC joint dislocation. However, scapular dyskinesis might also be the result of chronic superior shoulder pain or the loss of function of the AC joint as a stable fulcrum of the shoulder girdle. In fact, in the presence of dislocation, the AC joint could not allow the normal progression of the instant center of scapular rotation from the medial scapular border to the AC joint.9 Prominence of the entire medial border and prominence of the superior angle of the scapula were classified as a type II pattern and type III pattern, respectively, and were attributed to weakness of the upper and lower trapezius and rhomboid and to impingement syndrome and rotator cuff diseases.14,15 The 30% of our patients with scapular dyskinesis were equally distributed among these 2 patterns. Superior shoulder pain and loss of the stable fulcrum may again be the cause of scapular dyskinesis development. Of the patients with scapular dyskinesis in this study, 3 of 5 had SICK scapula syndrome. In these patients the mean score on the SICK Scapula Rating Scale was 6.9 points (out of a possible 20 points). Unfortunately, we were not able to find other articles permitting comparison with our results. However, in our experience, if this score was lower than 5 points (as in 2 cases in our study), overhead activities were not limited, whereas a score from 5 to 10 points meant that such activities were painful but possible. The score in 3 patients was higher than 10 points. They could not substantially use the involved arm when abducted or elevated over 90° and had shoulder painful at rest. In many studies conservative management and surgical treatment of type III AC dislocations were found to yield a similar proportion of satisfactory results.4-7,19 However, in no article that analyzed conservatively treated patients was scapular dyskinesis considered as a possible cause of shoulder dysfunction. In our study the mean Constant scores were 83 points and 92 points for the affected side and healthy side, respectively. Furthermore, the mean Constant score was 75 points in patients with scapular dyskinesis and 88 points in those without dyskinesis. The fact that patients with dyskinesis have poorer results, at least subjectively, than those without scapular malposition is confirmed by the different mean scores in the 2 groups on the SST. Unfortunately, with the
SICK SCAPULA SYNDROME available data, no statistical analysis was performed for this subjective evaluation scale. Which is the best treatment in patients with a chronic unreduced type III AC dislocation is still a matter of discussion. Most of the abnormalities in scapular motion or position can be managed by rehabilitation programs to re-establish muscle strength and activation patterns.19-21 Kibler et al.10 obtained good results with such programs in a high percentage of patients with scapular dyskinesis not related to chronic AC dislocation. Unfortunately, we do not know whether, in these patients, physical therapy or surgical treatment for chronic dislocation may cause the resolution of dyskinesis. One limitation of our study is that we do not know what amount of scapulothoracic motion was present before injury. Therefore it remains unclear whether the injury is truly responsible for the dysfunction, especially given the small number of patients studied. In addition, it may be possible that patients who have impaired scapulothoracic motion before injury are becoming worse after injury. We also did not compare our cohort with a control group. However, in our experience scapular dyskinesis affects only a small percentage of normal subjects. CONCLUSIONS Chronic type III AC dislocation causes scapular dyskinesis in 70.6% of patients, of whom 58.3% have SICK scapula syndrome develop. Dyskinesis might be due to loss of function of the AC joint as a stable fulcrum of the shoulder girdle or due to the superior shoulder pain caused by the dislocation. In our study scapular dyskinesis was found to be correlated with impaired shoulder function. In fact, the values for the Constant score and SST were lower in patients with dyskinesis compared with those without scapular malposition. REFERENCES 1. Riand N, Sadowski C, Hoffmeyer P. Acute acromioclavicular dislocations. Acta Orthop Belg 1999;65:393-403 (in French). 2. Dumonski M, Mazzocca A, Rios C, Romeo A, Arciero R. Evaluation and management of acromioclavicular joint injuries. Am J Orthop 2004;33:526-532.
45
3. Rockwood CJ, Williams G, Young D. Disorders of the AC joint. In: Rockwood CJ, Matsen F, eds. The shoulder. Vol 1. Philadelphia: Saunders, 1998;483-553. 4. Bradley JP, Elkousy H. Decision making: Operative versus non-operative treatment of acromioclavicular joint injuries. Clin Sports Med 2003;22:277-290. 5. Hootman JM. Acromioclavicular dislocation: Conservative or surgical therapy. J Athl Train 2004;39:10-11. 6. Phillips AM, Smart C, Groom AFG. Acromioclavicular dislocation. Conservative or surgical therapy. Clin Orthop Relat Res 1998:10-17. 7. Nissen CW, Chatterjee A. Type III acromioclavicular separation: Results on a recent survey on its management. Am J Orthop 2007;36:89-93. 8. Gstettner C, Tauber M, Hitzl W, Resch H. Rockwood type III AC dislocation: Surgical versus conservative treatment. J Shoulder Elbow Surg 2008;17:220-225. 9. Bagg SD, Forrest WJ. A biomechanical analysis of scapular rotation during arm abduction in the scapular plane. Am J Phys Med Rehabil 1988;67:238-245. 10. Kibler WB, McMullen J. Scapular dyskinesis and its relation to shoulder pain. J Am Acad Orthop Surg 2003;11:142-151. 11. Warner JP, Micheli LJ, Arslanian LE, Kennedy J, Kennedy R. Scapulothoracic motion in normal shoulders and shoulders with glenohumeral instability and impingement syndrome: A study using Moirè topographic analysis. Clin Orthop Relat Res 1992:191-199. 12. McClure PW, Minchener LA, Sennet BJ, Karduna AR. Direct 3-dimensional measurement of scapular kinematics during dynamic movements in vivo. J Shoulder Elbow Surg 2001;10: 269-277. 13. McQuade KJ, Dawson J, Smidt GL. Scapulothoracic muscle fatigue associated with alterations in scapulohumeral rhythm kinematics during maximum resistive shoulder elevation. J Orthop Sports Phys Ther 1998;28:74-80. 14. Kibler WB, Uhl TL, Maddux JW, Brooks PW, Zeller B, McMullen J. Qualitative clinical evaluation of scapular dysfunction: A reliability study. J Shoulder Elbow Surg 2002;11: 550-556. 15. Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: Spectrum of pathology. Part III: The SICK scapula, scapular dyskinesis, the kinetic chain, and rehabilitation. Arthroscopy 2003;19:641-661. 16. Kibler WB. The role of the scapula in athletic shoulder function. Am J Sports Med 1998;26:325-337. 17. Constant CR, Murley AHG. A clinical method of functional assessment of the shoulder. Clin Orthop Relat Res 1987:160164. 18. Lippit SB, Harreyman DT, Matsen FA. A practical tool for evaluating shoulder function. The Simple Shoulder Test. In: Matsen FA, Fu FH, Hawkins RJ, eds. The shoulder: A balance of mobility and stability. Rosemont, IL: American Academy of Orthopaedic Surgeons, 1993;501-518. 19. Spancer EE. Treatment of grade III acromioclavicular joint injuries. A systematic review. Clin Orthop Relat Res 2007; 455:38-44. 20. Kunhn JE, Plancher KD, Hawkins RJ. Scapular winging. J Am Acad Orthop Surg 1995;3:319-325. 21. Kibler WB. Evaluation and diagnosis of scapulothoracic problems in the athlete. Sports Med Arthrosc 2000;8:192-202.
Purpose: This study was aimed at evaluating whether scapular dyskinesis and, eventually, SICK (Scapular malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement) scapula syndrome develop in patients with chronic type III acromioclavicular (AC) dislocation. Methods: Scapulothoracic motion was studied in 34 patients with chronic AC dislocation by use of the protocol described by Kibler et al. and Burkhart et al. An anteroposterior radiograph of the scapulae with the arms abducted was also obtained. The SICK Scapula Rating Scale was applied to patients with SICK scapula syndrome. Shoulder function was assessed with the Constant score and Simple Shoulder Test (SST). Results: Of the 34 patients, 24 (70.6%) had scapular dyskinesis with the arms at rest, and 14 of these (58.3%) had SICK scapula syndrome. The mean SICK Scapula Rating Scale score was 6.9 points (out of a possible 20 points). Clinical and radiographic evaluations with the arms abducted at 90° confirmed scapular dyskinesis in 61.7% and 64.7% of patients, respectively (P ⬎ .05). The Constant score was 83 points for the pathologic side and 91 points for the contralateral side. The Constant score value was 75 and 88, respectively, in patients with dyskinesis and those without dyskinesis (P ⬍ .05); the mean value for the SST was 8 of 12 and 10 of 12, respectively. Conclusions: Chronic type III AC dislocation causes scapular dyskinesis in 70.6% of patients. Of the latter, 58.3% have SICK scapula syndrome develop. Dyskinesis might be due to loss of the stable fulcrum of the shoulder girdle represented by the AC joint and due to the superior shoulder pain caused by the dislocation. The values for the Constant score and SST were lower in patients with dyskinesis. Level of Evidence: Level IV, prognostic case series. Key Words: Acromioclavicular joint dislocations—Type III acromioclavicular separation— Scapular dyskinesis—SICK scapula syndrome.
A
cromioclavicular (AC) joint injuries are common, especially in athletes. They represent 12% of dislocations at the shoulder girdle and 8% of all joint dislocations in the human body.1 The AC joint stabilizes the scapula in relation to the clavicle by means of a complex of ligaments and muscles. Although the clavicle rotates upward 40° to 50° during
From the Department of Orthopaedic Surgery, University “La Sapienza,” Rome, Italy. The authors report no conflict of interest. Received April 24, 2008; accepted August 27, 2008. Address correspondence and reprint requests to Stefano Carbone, M.D., Department of Orthopaedic Surgery, University “La Sapienza,” Piazzale Aldo Moro, 5, 00100, Rome, Italy. E-mail: [email protected] © 2009 by the Arthroscopy Association of North America 0749-8063/09/2501-8221$36.00/0 doi:10.1016/j.arthro.2008.08.019
40
full overhead elevation, only 5° to 8° of motion occur in the AC joint.2 This difference is the result of “synchronous scapuloclavicular” motion: as the clavicle rotates upward, the scapula rotates downward, and AC joint motion thereby decreases. This synchrony is coordinated by the coracoclavicular ligaments. Joint dislocation usually results from a direct blow to the acromion with the arm adducted. The classification of AC injuries is based on the type of anatomic lesion, as well as the direction and amount of clavicular displacement. The Rockwood classification, which is the most commonly used system, includes 6 types of injury of increasing severity.3 This classification defines the extent of injury and helps in the management of AC joint injuries. Generally, types I and II are treated conservatively with immobilization, ice, and nonsteroidal drugs.4 On the other hand, types IV, V, and VI almost always require surgical treat-
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 25, No 1 (January), 2009: pp 40-45
SICK SCAPULA SYNDROME ment.4 The management of type III dislocation, characterized by complete AC and coracoclavicular ligament tears, as well as coracoclavicular interspace greater than 25% to 100% of that in the normal shoulder, is controversial, although several prospective, randomized, controlled trials have shown that the results of conservative treatment are better than those of surgery.4-7 On the contrary, a recent study states that surgical reconstruction guarantees better outcomes.8 Bagg and Forrest9 observed that AC joint injuries associated with clavicle instability or osteoarthritic changes of the joint interfere with clavicular function and can affect scapular kinematics by not allowing the normal progression of the instant center of scapular rotation from the medial scapular border to the AC joint. Scapular dyskinesis is an alteration of the normal position or motion of the scapula during coupled scapulohumeral movements. It occurs after a large number of injuries involving the shoulder joint and is often a cause of shoulder pain.10 Warner et al11 found alterations of the scapular position and motion in 68% to 100% of patients with a history of shoulder injuries. Three-dimensional biomechanical analysis of scapular motions shows that the scapula moves around 3 axes of motion simultaneously.12,13 Abnormal motion patterns in scapular dyskinesis are best detected by first determining the position of the scapula with the patient’s arms at rest and then observing the scapular motion as the arms are elevated and lowered in the scapular plane. These dyskinetic patterns fall into 3 categories, characterized by the prominence of the inferomedial border of the scapula (type I), the entire medial border (type II), or the superomedial border (type III).14 Recently, Burkhart et al.15 have related the disabled throwing shoulder to a particular overuse muscle fatigue syndrome: “the SICK scapula.” The acronym SICK stands for Scapular malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement. The main feature of this syndrome is the malposition of the scapula in the dominant throwing shoulder, which appears to be lower than the contralateral shoulder. Symptomatic patients may complain of anterior shoulder pain in the region of the coracoid, posterosuperior scapular pain with or without radiation to the paraspinous neck region or proximal lateral arm, superior (AC joint) shoulder pain, or radicular symptoms.15 The authors have examined their overhead throwing athletes with 3 superficial landmark measurements of the scapula and have devised a grading system for the severity of scapular malposition.
41
In this study we have analyzed patients with chronic unreduced type III AC dislocation to determine whether scapular dyskinesis and, eventually, SICK scapula syndrome had developed. The kinematics of the involved scapulothoracic joint was studied to understand why some patients with an AC joint dislocation complain of pain in the AC joint, periscapular muscles, and scapulovertebral region. We hypothesized that this pain and the altered AC joint anatomy may interfere with the scapulothoracic rhythm. To our knowledge, this is the first study on the effects of a longstanding type III AC dislocation and on the biomechanics of the scapulothoracic joint. METHODS Between 2004 and 2007, 62 patients with radiographic evidence of type III AC dislocation were treated at our emergency department. Of these, 53 were treated conservatively whereas 9 underwent arthroscopic or open reduction of the dislocation. Twelve patients were excluded from the study for one of the following reasons: previous shoulder injury, associated neurologic deficit on the side of the lesion occurring at the time of dislocation, and age over 70 years at the time of follow-up. Patients with AC osteoarthritis were also excluded because, although it occurs rarely, they already had a painful shoulder before the injury. Seven additional patients could not be traced. All of the remaining 34 patients included in the study group had been treated with a figure-of-8 splint for a mean of 4 weeks and early motion of the upper limb. Thereafter, all patients followed a rehabilitation program for a mean period of 3 weeks. None had sustained other significant shoulder injuries within the follow-up period. There were 32 male and 2 female patients, aged 24 to 69 years (mean, 47 years) at the time of follow-up. The mean time interval between injury and follow-up was 28 months (range, 12 to 36 months). Scapulothoracic motion was separately evaluated by all of the authors. According to the protocol of Kibler et al.10,14 and Burkhart et al.,15 scapular position was first analyzed with the arms at rest (position 1). In this position we evaluated (1) the difference in height (in centimeters) of the superomedial scapular angle between the injured and contralateral scapulae, (2) the difference in the distance (in centimeters) of the superomedial scapular angle from the body midline between the injured and contralateral sides, and (3) the difference in angular degrees, measured with a goniometer, of the medial scapular border from the
42
S. GUMINA ET AL. Once scapulothoracic dyskinesis was diagnosed, we trained patients to follow the protocol described by Kibler and McMullen10 for rehabilitation of scapular dyskinesis, which emphasizes achieving full and appropriate scapular motion and coordinating that motion with complementary trunk and hip movements. The rehabilitation program reported by Burkhart et al.15 was adopted for patients with SICK scapula syndrome. Data are presented as means and were analyzed with the nonparametric Wilcoxon test. P ⬍ .05 was selected to indicate a statistically significant difference. RESULTS
FIGURE 1. First measurement: Difference in vertical height of superomedial scapular angle of injured scapula (A) compared with contralateral superomedial angle (B) (measured as number of centimeters from a to b) in position 1. Second measurement: Distance of superomedial scapular angle (A, B) from midline in injured and contralateral scapulae (centimeters from A to a minus centimeters from B to b). Third measurement: Difference in angular degrees of medial scapular margin from plumb midline between injured scapula (angle ␣) and contralateral scapula (angle ) measured with goniometer.
plumb line between the injured and contralateral scapulae (Fig 1). Considering 1.5 cm or 5° asymmetry as the threshold for abnormality in each measurement,15,16 we obtained the percentage of patients with scapular dyskinesis. If abnormalities were noted, we ascribed them to 1 of the 3 patterns of scapular dyskinesis described by Kibler et al.14 A history of coracoid pain was recorded, and coracoid position was assessed. For evaluating the severity of SICK scapula syndrome, we applied the SICK Scapula Rating Scale to patients who had scapular dyskinesis, inferior medial border prominence, and coracoid pain and malposition.15 This scale is based on measurements comparing the 2 scapula and investigating the subjective and objective pain of the injured shoulder. Subsequently, scapular position was assessed with the arms abducted at 90° and internally rotated, the elbows in full extension, and the hands holding a weight of 2 kg (position 2) by use of the same parameters described previously. To verify the reliability of clinical measurements, an anteroposterior radiograph of both scapulae was obtained in position 2, and the same measurements carried out on the patient’s body were made (Fig 2). Finally, we evaluated shoulder function with the Constant score17 and Simple Shoulder Test (SST).18
In position 1 the difference in vertical height of the superomedial scapular angle of the scapula between the injured and contralateral sides was 2.1 cm on average (range, ⫺1 to 4.5 cm; P ⫽ .014). The mean difference in the distance of the superomedial scapular angle from the midline between the side with AC dislocation and the contralateral side was 0.5 cm (range, ⫺2 to 2 cm; P ⫽ .208). The difference in angular degrees of the medial scapular margin from the plumb midline between the injured and contralateral scapulae was 8° (range, ⫺10° to 10°; P ⫽ .041). Of 34 patients, 24 (70.6%) had scapular dyskinesis, with a Kibler type I pattern (prominence of inferomedial border) in 17 (70.8%) (Fig 3), type II pattern (prominence of entire medial border) in 3 (12.5%) (Fig 4), and type III pattern (prominence of superomedial border) in 4 (16.6%) (Fig 5).14 SICK scapula syndrome was observed in 14 (58.3%) of the patients with scapular dyskinesis (Fig 6); the percentage was 41.2% if all 34 patients were considered. The mean
FIGURE 2. Anteroposterior radiograph of 2 scapulae with arms abducted at 90°, used to evaluate same parameters assessed on clinical examination.
SICK SCAPULA SYNDROME
43
FIGURE 5. Patient with chronic type III AC joint dislocation on right side and type III pattern of dyskinesis (prominence of superomedial border).
FIGURE 3. Patient with chronic type III AC dislocation on left side and type I pattern of dyskinesis (prominence of inferomedial border of scapula).
score on the SICK Scapula Rating Scale in the 14 patients with SICK scapula syndrome was 6.9 points (out of a possible 20 points) (range, 4 to 15 points) (with ⬍5 points in 2 cases, 5 to 10 points in 9 cases, and ⬎10 points in 3 cases). In position 2 the difference in height of the superomedial scapular angle between the affected and contralateral sides was 1.5 cm on average (range, ⫺1 to 3 cm; P ⫽ .032); the mean distance between the
FIGURE 4. Patient with chronic type III left AC dislocation on left side and type II pattern of dyskinesis (prominence of entire medial border). (Hypertrophy of the trapezius muscle does not allow AC dislocation to be appreciated.)
superomedial scapular angle and the midline was 1 cm (range, 0 to 2.6 cm; P ⫽ .142) greater on the injured side than on the contralateral side; and the angle formed by the medial scapular margin and the plumb midline was 8° (range, ⫺8° to 18°; P ⫽ .047) greater on the injured side. On the basis of these measurements, 21 patients (61.7%) were found to have scapular dyskinesis. At radiographic evaluation, the mean difference in height of the superomedial scapular angle between the injured scapula and the contralateral scapula was 1.7 cm (range, ⫺2 to 3 cm; P ⫽ .029); the mean difference in the superior scapular angle from the midline between the injured and opposite sides was 0.8 cm (range, ⫺2 to 3.3 cm; P ⫽ .208); and the difference in the value of the angle formed by the medial scapular margin and the plumb midline was 5° (range, ⫺8° to 11°; P ⫽ .049) between the injured and contralateral scapulae. On the basis of the radio-
FIGURE 6. Patient with chronic type III AC dislocation on right side and SICK scapula syndrome.
44
S. GUMINA ET AL.
graphic results, 22 patients (64.7%) had scapular dyskinesis. However, the comparison of clinical to radiographic measurements with the arms abducted at 90° did not show a statistically significant difference (P ⫽ .47). No significant differences emerged when comparing the measurements performed by the 3 authors (P ⫽ .052 to .124). The mean Constant score was 83 points (range, 54 to 94 points) for the injured side and 92 points (range, 88 to 100 points) for the healthy side (P ⫽ .0087 for comparison of the 2 groups). Patients with dyskinesis examined in position 1 (n ⫽ 24) had a score of 75 points on average (range, 54 to 80 patients) on the injured side, whereas patients with normal scapulothoracic motion (n ⫽ 10) had a mean score of 88 points (range, 75 to 94 points). Comparison of the Constant score in the last 2 groups of patients showed a statistically significant difference (P ⫽ .01). The mean SST score in the entire study group was 9 (out of a possible 12) (range, 6 to 12), with SST scores of 8 and 10 in patients with dyskinesis and those without dyskinesis, respectively. DISCUSSION In previous studies patients with shoulder pain caused by different pathologic conditions were found to have scapular dyskinesis.10 However, we could not find any studies on the changes in scapulothoracic motion as a result of type III AC joint dislocation. According to Kibler et al.,14 scapulothoracic position and motion should be studied using clinical measurements carried out first with the arms at rest and then with the arms abducted at 90° and internally rotated and elbows in full extension. We adopted this method, and in addition, we performed measurements on anteroposterior radiographs of the shoulders with the arms in abduction, because we thought that they might be more accurate than clinical measurements. However, no statistically significant difference was found between the values obtained with the arms at rest and those with the arms abducted or those calculated on the radiographs. These findings suggest that scapular dyskinesis can be detected based solely on the data obtained with the arms at rest (position 1). They also indicate that measurements on radiographs do not provide further information on scapular position. In this study 70.6% of patients with chronic AC dislocation had scapular dyskinesis, and more than two thirds of them had a prominence of the inferomedial border of the scapula. This abnormality of scap-
ular position was classified by Kibler et al.14 as a type I pattern and was attributed to inflexibility of the pectoralis major and minor, as well as to the weakness of the lower trapezius and serratus anterior.14,15 This biomechanical hypothesis may also explain the development of scapular dyskinesis in patients with a chronic AC joint dislocation. However, scapular dyskinesis might also be the result of chronic superior shoulder pain or the loss of function of the AC joint as a stable fulcrum of the shoulder girdle. In fact, in the presence of dislocation, the AC joint could not allow the normal progression of the instant center of scapular rotation from the medial scapular border to the AC joint.9 Prominence of the entire medial border and prominence of the superior angle of the scapula were classified as a type II pattern and type III pattern, respectively, and were attributed to weakness of the upper and lower trapezius and rhomboid and to impingement syndrome and rotator cuff diseases.14,15 The 30% of our patients with scapular dyskinesis were equally distributed among these 2 patterns. Superior shoulder pain and loss of the stable fulcrum may again be the cause of scapular dyskinesis development. Of the patients with scapular dyskinesis in this study, 3 of 5 had SICK scapula syndrome. In these patients the mean score on the SICK Scapula Rating Scale was 6.9 points (out of a possible 20 points). Unfortunately, we were not able to find other articles permitting comparison with our results. However, in our experience, if this score was lower than 5 points (as in 2 cases in our study), overhead activities were not limited, whereas a score from 5 to 10 points meant that such activities were painful but possible. The score in 3 patients was higher than 10 points. They could not substantially use the involved arm when abducted or elevated over 90° and had shoulder painful at rest. In many studies conservative management and surgical treatment of type III AC dislocations were found to yield a similar proportion of satisfactory results.4-7,19 However, in no article that analyzed conservatively treated patients was scapular dyskinesis considered as a possible cause of shoulder dysfunction. In our study the mean Constant scores were 83 points and 92 points for the affected side and healthy side, respectively. Furthermore, the mean Constant score was 75 points in patients with scapular dyskinesis and 88 points in those without dyskinesis. The fact that patients with dyskinesis have poorer results, at least subjectively, than those without scapular malposition is confirmed by the different mean scores in the 2 groups on the SST. Unfortunately, with the
SICK SCAPULA SYNDROME available data, no statistical analysis was performed for this subjective evaluation scale. Which is the best treatment in patients with a chronic unreduced type III AC dislocation is still a matter of discussion. Most of the abnormalities in scapular motion or position can be managed by rehabilitation programs to re-establish muscle strength and activation patterns.19-21 Kibler et al.10 obtained good results with such programs in a high percentage of patients with scapular dyskinesis not related to chronic AC dislocation. Unfortunately, we do not know whether, in these patients, physical therapy or surgical treatment for chronic dislocation may cause the resolution of dyskinesis. One limitation of our study is that we do not know what amount of scapulothoracic motion was present before injury. Therefore it remains unclear whether the injury is truly responsible for the dysfunction, especially given the small number of patients studied. In addition, it may be possible that patients who have impaired scapulothoracic motion before injury are becoming worse after injury. We also did not compare our cohort with a control group. However, in our experience scapular dyskinesis affects only a small percentage of normal subjects. CONCLUSIONS Chronic type III AC dislocation causes scapular dyskinesis in 70.6% of patients, of whom 58.3% have SICK scapula syndrome develop. Dyskinesis might be due to loss of function of the AC joint as a stable fulcrum of the shoulder girdle or due to the superior shoulder pain caused by the dislocation. In our study scapular dyskinesis was found to be correlated with impaired shoulder function. In fact, the values for the Constant score and SST were lower in patients with dyskinesis compared with those without scapular malposition. REFERENCES 1. Riand N, Sadowski C, Hoffmeyer P. Acute acromioclavicular dislocations. Acta Orthop Belg 1999;65:393-403 (in French). 2. Dumonski M, Mazzocca A, Rios C, Romeo A, Arciero R. Evaluation and management of acromioclavicular joint injuries. Am J Orthop 2004;33:526-532.
45
3. Rockwood CJ, Williams G, Young D. Disorders of the AC joint. In: Rockwood CJ, Matsen F, eds. The shoulder. Vol 1. Philadelphia: Saunders, 1998;483-553. 4. Bradley JP, Elkousy H. Decision making: Operative versus non-operative treatment of acromioclavicular joint injuries. Clin Sports Med 2003;22:277-290. 5. Hootman JM. Acromioclavicular dislocation: Conservative or surgical therapy. J Athl Train 2004;39:10-11. 6. Phillips AM, Smart C, Groom AFG. Acromioclavicular dislocation. Conservative or surgical therapy. Clin Orthop Relat Res 1998:10-17. 7. Nissen CW, Chatterjee A. Type III acromioclavicular separation: Results on a recent survey on its management. Am J Orthop 2007;36:89-93. 8. Gstettner C, Tauber M, Hitzl W, Resch H. Rockwood type III AC dislocation: Surgical versus conservative treatment. J Shoulder Elbow Surg 2008;17:220-225. 9. Bagg SD, Forrest WJ. A biomechanical analysis of scapular rotation during arm abduction in the scapular plane. Am J Phys Med Rehabil 1988;67:238-245. 10. Kibler WB, McMullen J. Scapular dyskinesis and its relation to shoulder pain. J Am Acad Orthop Surg 2003;11:142-151. 11. Warner JP, Micheli LJ, Arslanian LE, Kennedy J, Kennedy R. Scapulothoracic motion in normal shoulders and shoulders with glenohumeral instability and impingement syndrome: A study using Moirè topographic analysis. Clin Orthop Relat Res 1992:191-199. 12. McClure PW, Minchener LA, Sennet BJ, Karduna AR. Direct 3-dimensional measurement of scapular kinematics during dynamic movements in vivo. J Shoulder Elbow Surg 2001;10: 269-277. 13. McQuade KJ, Dawson J, Smidt GL. Scapulothoracic muscle fatigue associated with alterations in scapulohumeral rhythm kinematics during maximum resistive shoulder elevation. J Orthop Sports Phys Ther 1998;28:74-80. 14. Kibler WB, Uhl TL, Maddux JW, Brooks PW, Zeller B, McMullen J. Qualitative clinical evaluation of scapular dysfunction: A reliability study. J Shoulder Elbow Surg 2002;11: 550-556. 15. Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: Spectrum of pathology. Part III: The SICK scapula, scapular dyskinesis, the kinetic chain, and rehabilitation. Arthroscopy 2003;19:641-661. 16. Kibler WB. The role of the scapula in athletic shoulder function. Am J Sports Med 1998;26:325-337. 17. Constant CR, Murley AHG. A clinical method of functional assessment of the shoulder. Clin Orthop Relat Res 1987:160164. 18. Lippit SB, Harreyman DT, Matsen FA. A practical tool for evaluating shoulder function. The Simple Shoulder Test. In: Matsen FA, Fu FH, Hawkins RJ, eds. The shoulder: A balance of mobility and stability. Rosemont, IL: American Academy of Orthopaedic Surgeons, 1993;501-518. 19. Spancer EE. Treatment of grade III acromioclavicular joint injuries. A systematic review. Clin Orthop Relat Res 2007; 455:38-44. 20. Kunhn JE, Plancher KD, Hawkins RJ. Scapular winging. J Am Acad Orthop Surg 1995;3:319-325. 21. Kibler WB. Evaluation and diagnosis of scapulothoracic problems in the athlete. Sports Med Arthrosc 2000;8:192-202.