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The natural course of atraumatic shoulder instability
The natural course of atraumatic shoulder instability Shigehito Kuroda, MD, Tetsuyuki Sumiyoshi, MD, Johji Moriishi, MD, Kimiko Maruta, MD, and Noriyuki Ishige, MD, Chiba, Japan
Over the years, we have observed a shifting among loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation, leading us to the conclusion that they are all varieties of the same condition: atraumatic shoulder instability. For this study, we followed the natural course of atraumatic shoulder instability in 341 patients (573 shoulders) for 3 years or more. There were 467 cases of loose shoulder, 49 cases of voluntary dislocation, 56 cases of habitual dislocation, and 1 case of sustained subluxation. The average follow-up period was 4 years and 6 months. Spontaneous recovery occurred in 50 cases. The average age of patients at the onset of atraumatic shoulder instability who exhibited a change in instability was 14.6 years. The average age of patients at the onset of atraumatic shoulder instability who exhibited no change in shoulder instability was 19.4 years. There was a significant difference of P < .01 in the age of onset between these two groups. The incidence of spontaneous recovery in the group that discontinued overhead sports was 8.7 times greater than in the group that continued to play overhead sports. The incidence of spontaneous recovery in the group that discontinued non-overhead sports was only 1.4 times greater than in the group that continued to play non-overhead sports. However, no instance of spontaneous recovery was observed among patients who changed from playing non-overhead sports to playing overhead sports. The spontaneous recovery of atraumatic shoulder instability encountered in this study shows that it is best to place priority on observing the course of atraumatic shoulder instability for several years and to avoid performing unnecessary surgery. (J Shoulder Elbow Surg 2001;10:100-4.)
INTRODUCTION In 1971, Endo et al2 reported that they found abnormal instability in 530 of 13,036 shoulders. They From Matsudo Orthopaedic Hospital, Matsudo City, Chiba Prefecture, Japan. Reprint requests: Shigehito Kuroda, MD, Matsudo Orthopaedic Hospital, 1-161 Asahi-cho, Matsudo City, Chiba Prefecture 271-0043 Japan. Copyright © 2001 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2001/$35.00 + 0 32/1/111962 doi:10.1067/mse.2001.111962
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named this disorder loose shoulder. In 1980, Neer and Foster7 reported on “inferior and multidirectional instability of the shoulder,” including traumatic and atraumatic shoulder instability. The term coined by Endo et al referred to the atraumatic type of instability. In the course of following loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation, a pattern of shifting is seen among them, leading to the conclusion that they are all varieties of the same condition: atraumatic shoulder instability. Furthermore, spontaneous recovery sometimes occurs in which all shoulder instability disappears. The natural course of atraumatic shoulder instability has not been reported in the literature except for in 1 abstract on glenohumeral laxity by Emery and David1 and in 2 of our articles (in Japanese with English abstracts).3-6 In loose shoulder, there is downward, forward, and backward instability of the shoulder joint. It is not a symptom of a larger ailment affecting the whole body nor a paralytic condition. The onset of loose shoulder is never the result of trauma. The subjective symptoms are a heavy feeling in the shoulder girdle, stiffness in the shoulder, mild pain, and a sensation of instability when lifting things. Symptoms are mild, but stubborn to cure. Loose shoulder accounted for 82.4% of the cases in this study. In voluntary dislocation, there is downward, forward, and backward instability of the shoulder joint, and the patient is able to bring about dislocation or subluxation of the shoulder at will. The important point with voluntary dislocation is that dislocation or subluxation does not occur once the patient is taught how to avoid it. Voluntary dislocation accounted for 7.9% of the cases in this study. In habitual dislocation, there is downward, forward, and backward instability of the shoulder joint, and dislocation or subluxation of the shoulder occurs involuntarily when the joint assumes a certain position, which differs for each patient. Habitual dislocation accounted for 9.4% of the cases in our study. Habitual dislocation differs from traumatic recurrent shoulder dislocation, which was not covered by this study. In this study, 93% of habitual dislocation and subluxation were of the posterior type in which posterior subluxation occurs when the arm is raised in a forward elevated position of approximately 90° to 100°. The remaining 7% of habitual dislocation was of the anterior type in which anterior subluxation or dislocation occurs when the arm is raised between 90° and the pivotal position.
J Shoulder Elbow Surg Volume 10, Number 2
In sustained subluxation, there is downward, forward, and backward instability of the shoulder joint, and the shoulder joint is in a permanent state of anterior subluxation. The condition is extremely rare and accounted for only 0.3% of the cases in this study.
CASES AND METHOD From April 1985 to April 1999, 12,949 patients (14,218 shoulders) visited the Shoulder Disorder Clinic at Matsudo Orthopaedic Hospital, and atraumatic shoulder instability was diagnosed in 511 patients (919 shoulders). Four hundred eight patients (79.8%) exhibited atraumatic shoulder instability in both shoulders. For this study, we followed the natural course of atraumatic shoulder instability in 573 shoulders of 341 patients for 3 years or more. We excluded patients whose clinical record was incomplete or who underwent rehabilitation. However, we did include patients who used nonsteroidal anti-inflammatory drugs, ointment, or medicated skin patches for 2 or 3 weeks. Male patients numbered 145 and accounted for 241 cases. They ranged in age from 5 to 46 years, with an average age of 18.9 years. Female patients numbered 196 and accounted for 332 cases. They ranged in age from 8 to 51 years, with an average age of 21.1 years. The follow-up period was between 3 and 11 years, with an average of 4 years and 6 months. The breakdown of the 573 cases of atraumatic shoulder instability in this study was as follows: 476 cases of loose shoulder, 49 cases of voluntary dislocation, 56 cases of habitual dislocation, and 1 case of sustained subluxation. For this study, a diagnosis of atraumatic shoulder instability required that the condition had not been caused by trauma and that at least 3 of the following 5 conditions were present: 1. Presence of the sulcus sign, induced by downward traction when the arm was held at the side both in the internally rotated position and in the externally rotated position 2. Forward instability in which the humeral head moved forward past the glenoid rim either partially or completely as a result of the load and shift test 3. Backward instability in which the humeral head moved backward past the glenoid rim either partially or completely as a result of the load and shift test 4. An increase in the rotatory range of motion in zero position 5. Outward slipping of the humerus evident on a plain radiograph taken in zero position. Of the 573 cases of atraumatic shoulder instability in this study, 423 cases (73.8%) met all 5 criteria, 109 cases (19%) met 4 criteria, and 41 cases (7.2%) met 3 criteria. To measure the rotatory range of motion in zero position, 2 photographs of each patient in supine position were taken with a digital camera, and the results were measured on a computer display. The arm was placed in a forward elevated position of 150°, with a 30° wedge-shaped pillow underneath to prevent the degree of elevation from becoming larger. One photograph showed the elbow bent at 90° with the shoulder in maximum external rotation, and the other photograph showed the shoulder in maximum internal rotation. The average rotatory range of motion in
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zero position in this study was 93.1°. For persons with normal shoulders (we examined 157 normal shoulders of 88 persons) with the factor of age averaged in (average age was 20.7 years), the average rotatory range of motion in the zero position was 72.7°. The rotatory range of motion in the zero position of our atraumatic shoulder instability patients was significantly greater than in those without atraumatic shoulder instability (P < .01). For the purposes of this study, we excluded patients with a Hill-Sachs lesion, a Bankart lesion, or subscapular leakage because they did not fulfil the conditions for atraumatic shoulder instability. We conducted follow-up evaluations of the patients with atraumatic shoulder instability every 3 to 6 months, taking into consideration all changes in shoulder instability.
RESULTS Change in shoulder instability without progression to another disorder In 26 cases (5.6%) of loose shoulder and 1 case (1.8%) of habitual dislocation, there was definite improvement of shoulder joint stability. In 2 cases of loose shoulder (0.4%) and in 2 cases of habitual dislocation (3.6%), there was a definite increase in shoulder joint instability (Table I). Thus, in 31 (5.4%) of the cases in this study, we were able to detect change in shoulder joint instability without any shift of disorder. Shift of disorder In our follow-up, 50 (8.7%) of the cases in this study underwent one or more shifts of disorder. As Table II shows, the shifts of disorder in this study showed a great deal of variation. Spontaneous recovery In the course of follow-up, we observed spontaneous recovery with the clinical disappearance of shoulder joint instability in 43 cases of loose shoulder (9%) and in 7 cases of habitual dislocation (12.5%) (Table III), a total of 8.7% of the cases in this study. Women accounted for 28 of the cases and men 22. For women, the age of spontaneous recovery ranged from 14 to 39 years, with an average of 20.1 years. Of the 28 female cases, 24 cases (85.7%) recovered at 24 years or younger. For men, the age of spontaneous recovery ranged from 9 to 29 years, with an average of 16.4 years. Of the 22 male patients, 21 cases (95.5%) recovered at 20 years or younger. Investigation of the relation between sports and spontaneous recovery showed that 97 patients (162 cases) played such overhead sports as baseball, softball, volleyball, handball, javelin throwing, tennis, badminton, and dodge ball. Of those who stopped playing overhead sports, 26.9% (7 of 26 cases) recovered spontaneously. On the other hand, only 3.1% of those who continued to play overhead sports (4 of 127 cases) recovered spontaneously (Figure 1). There were no spontaneous recoveries among the 9
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cases that changed from overhead sports to non-overhead sports. As for non-overhead sports, we found that 73 patients (120 cases) played some kind of non-overhead sport. The rate of spontaneous recovery for those who stopped playing non-overhead sports was 20.8% (5 of 24 cases) as opposed to 15.2% (14 of 92 cases) for those who continued to play non-overhead sports (Figure 2). However, there were no spontaneous recoveries among the 4 cases who changed from nonoverhead sports to overhead sports. In addition, there were no spontaneous recoveries among 9 patients (18 cases) who exhibited general joint laxity and Endo type III loose shoulder (downward subluxation recognized in a radiography taken in standing position without any load). One case each of loose shoulder and habitual dislocation relapsed after spontaneous recovery. All in all, in our follow-up, 22.9% of the cases in this study (131 of 573 cases) exhibited some change in shoulder joint instability, be it improvement in shoulder stability, increase in shoulder instability, shift of disorder, or spontaneous recovery. The age of onset of atraumatic shoulder instability among those who exhibited change in shoulder joint instability ranged from 4 to 39 years, with an average age of 14.6 ± 5.4 years (mean ± SD). On the other hand, the age of onset of atraumatic shoulder instability among those who did not exhibit change in shoulder joint instability ranged from 4 to 50 years, with an average of 19.4 ± 9.4 years. There was a statistically significant difference in the age of onset between these two groups (P .01).
DISCUSSION As is well known, atraumatic shoulder instability commonly strikes the young. In the course of our long-term follow-up, we frequently encountered shifts of disorder and spontaneous recoveries. We came to see that in many cases, atraumatic shoulder joint instability changes often. The shift of disorder among loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation led us to the conclusion that they are all variations of the same disorder: atraumatic shoulder instability. The age of onset in patients who exhibited change in shoulder joint instability was statistically significantly lower than for those patients who did not exhibit change in shoulder joint instability. Except in the cases of general joint laxity and Endo type III loose shoulder, atraumatic shoulder instability that develops at an early age is easily influenced by the amount of physical activity in which patients engage, making it reasonable to expect spontaneous recovery. The incidence of spontaneous recovery in the group that discontinued overhead sports was 8.7 times greater than in the group that continued to play overhead sports. Furthermore, in the group that changed from non-overhead sports to overhead sports, there were no sponta-
J Shoulder Elbow Surg March/April 2001
Table I Change in shoulder instability without any shift of disorder Disorder (N)
Improvement
Increase in shoulder instability
26 (5.6%) 1 (1.8%)
2 (0.4%) 2 (3.6%)
Loose shoulder (476) Habitual dislocation (56)
Table II Shifts of disorder Shifts of disorder
Shoulders
LS → VD LS → HD VD → HD LS → VD → LS LS → VD → HD → VD VD → HD → LS LS → VD → HD → LS LS → VD → HD LS → VD → HD → LS → HD LS → HD → LS HD → LS → HD HD → VD VD → LS HD → LS VD → SS
8 11 8 1 1 3 1 2 1 3 1 3 4 2 1
LS, Loose shoulder; VD, voluntary dislocation; HD, habitual dislocation; SS, sustained subluxation.
Table III Spontaneous recovery Disorder (N) Loose shoulder (476) Habitual dislocation (56)
Shoulders
Incidence
43 7
9.2% 12.5%
neous recoveries. When we consider these facts, we can see that overhead sports are an impediment to atraumatic shoulder instability healing naturally. The possibility of spontaneous recovery should be an extremely important consideration when deciding on the need for surgery. For instance, habitual dislocation is involuntary. It is easy to think that surgery is appropriate as soon as a diagnosis is made. Indeed, we ourselves thought so until we encountered the spontaneous recovery of atraumatic shoulder instability. However, since confirming that spontaneous recovery of atraumatic shoulder instability does occur, we set a follow-up period of at least 2 years before considering surgery. If pain occurs during that period, or if use of the shoulder in daily activities becomes severely restricted, then the time has come for operative treatment. Even when a loose shoulder joint goes through repeated dislocations or subluxations, there is little risk of intra-articular lesions. However, when pain occurs, the possibility of intra-articular lesion becomes impossible
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Figure 1 Incidence of spontaneous recovery in the group that discontinued overhead sports and in the group that continued overhead sports.
Figure 2 Incidence of spontaneous recovery in the group that discontinued non-overhead sports and in the group that continued non-overhead sports.
to deny, and it is no longer possible to leave atraumatic shoulder instability untreated. Once this view is adopted, operative treatment of atraumatic shoulder instability can be seen as deciding itself. Loose shoulder is a stubborn complaint, but overall symptoms are mild. This is why the need for operative treatment is rare. In the case of voluntary dislocation, it is possible to teach the patient to prevent dislocation through greater awareness. If a person can learn to prevent voluntary dislocation that has become
a habit, surgery is not necessary. The real problematic types of atraumatic shoulder instability are voluntary dislocation that a patient cannot learn to control and habitual dislocation. However, even in the case of these two types of atraumatic shoulder instability, unless pain appears or daily activities become severely restricted, it is best to set a follow-up period of several years with the hope of eventual spontaneous recovery, and avoid unnecessary surgery as much as possible. An exception to this rule should be made for
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patients with habitual dislocation who become depressed because they are unable to play sports. In such cases, surgeons should not hesitate to operate.
We would like to express our thanks to Mr Charles Thorpe for his help in preparing this paper.
Summary We followed 573 cases of atraumatic shoulder instability for 3 years or more. In 31 cases (5.4%) in this study, we found a change in shoulder instability with no shift of disorder. In 50 cases (8.7%), there was a shift of disorder between loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation. In 50 cases (8.7%), we observed spontaneous recovery. The incidence of spontaneous recovery in the group that gave up overhead sports was 8.7 times greater than in the group that continued to play overhead sports. The incidence of spontaneous recovery in the group that gave up non-overhead sports was only 1.4 times greater than in the group that continued to play non-overhead sports. Before deciding on operative treatment for atraumatic shoulder instability, it is best to bear in mind the possibility of spontaneous recovery and set an adequate follow-up period.
REFERENCES 1. Emery RJH, David HG. Changes in glenohumeral laxity signs during adolescence [abstract]. J Shoulder Elbow Surg 1994;3:S23 2. Endo H, Takigawa A, Takada K, Miyoshi S. Die diagnose und die behandlung von dem sogenannte schulterschlottergelenk [in Japanese]. Cent Jpn Orthop Traumat 1971;14:630-2. 3. Kuroda S, Sumiyoshi T, Sai M, Moriishi J. Untreated results of the atraumatic shoulder instability [abstract]. J Shoulder Elbow Surg 1993;2:S37. 4. Kuroda S, Sumiyoshi T, Sai M, Moriishi J. Untreated results of the atraumatic shoulder instability [in Japanese]. The Shoulder Joint 1993;1:81-5. 5. Kuroda S, Sumiyoshi T, Sai M, Moriishi J, Maruta K. Onset and spontaneous recovery of multidirectional instability of the shoulder [abstract]. J Shoulder Elbow Surg 1997;6:242. 6. Kuroda S, Sumiyoshi T, Sai M, Moriishi J, Maruta K. Onset and spontaneous recovery of multidirectional instability of the shoulder [in Japanese]. The Shoulder Joint 1997;3:449-52. 7. Neer CS II, Foster CR. Inferior capsular shift for involuntary inferior and multidirectional instability of the shoulder. J Bone Joint Surg Am 1980;62:897-908.
Over the years, we have observed a shifting among loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation, leading us to the conclusion that they are all varieties of the same condition: atraumatic shoulder instability. For this study, we followed the natural course of atraumatic shoulder instability in 341 patients (573 shoulders) for 3 years or more. There were 467 cases of loose shoulder, 49 cases of voluntary dislocation, 56 cases of habitual dislocation, and 1 case of sustained subluxation. The average follow-up period was 4 years and 6 months. Spontaneous recovery occurred in 50 cases. The average age of patients at the onset of atraumatic shoulder instability who exhibited a change in instability was 14.6 years. The average age of patients at the onset of atraumatic shoulder instability who exhibited no change in shoulder instability was 19.4 years. There was a significant difference of P < .01 in the age of onset between these two groups. The incidence of spontaneous recovery in the group that discontinued overhead sports was 8.7 times greater than in the group that continued to play overhead sports. The incidence of spontaneous recovery in the group that discontinued non-overhead sports was only 1.4 times greater than in the group that continued to play non-overhead sports. However, no instance of spontaneous recovery was observed among patients who changed from playing non-overhead sports to playing overhead sports. The spontaneous recovery of atraumatic shoulder instability encountered in this study shows that it is best to place priority on observing the course of atraumatic shoulder instability for several years and to avoid performing unnecessary surgery. (J Shoulder Elbow Surg 2001;10:100-4.)
INTRODUCTION In 1971, Endo et al2 reported that they found abnormal instability in 530 of 13,036 shoulders. They From Matsudo Orthopaedic Hospital, Matsudo City, Chiba Prefecture, Japan. Reprint requests: Shigehito Kuroda, MD, Matsudo Orthopaedic Hospital, 1-161 Asahi-cho, Matsudo City, Chiba Prefecture 271-0043 Japan. Copyright © 2001 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2001/$35.00 + 0 32/1/111962 doi:10.1067/mse.2001.111962
100
named this disorder loose shoulder. In 1980, Neer and Foster7 reported on “inferior and multidirectional instability of the shoulder,” including traumatic and atraumatic shoulder instability. The term coined by Endo et al referred to the atraumatic type of instability. In the course of following loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation, a pattern of shifting is seen among them, leading to the conclusion that they are all varieties of the same condition: atraumatic shoulder instability. Furthermore, spontaneous recovery sometimes occurs in which all shoulder instability disappears. The natural course of atraumatic shoulder instability has not been reported in the literature except for in 1 abstract on glenohumeral laxity by Emery and David1 and in 2 of our articles (in Japanese with English abstracts).3-6 In loose shoulder, there is downward, forward, and backward instability of the shoulder joint. It is not a symptom of a larger ailment affecting the whole body nor a paralytic condition. The onset of loose shoulder is never the result of trauma. The subjective symptoms are a heavy feeling in the shoulder girdle, stiffness in the shoulder, mild pain, and a sensation of instability when lifting things. Symptoms are mild, but stubborn to cure. Loose shoulder accounted for 82.4% of the cases in this study. In voluntary dislocation, there is downward, forward, and backward instability of the shoulder joint, and the patient is able to bring about dislocation or subluxation of the shoulder at will. The important point with voluntary dislocation is that dislocation or subluxation does not occur once the patient is taught how to avoid it. Voluntary dislocation accounted for 7.9% of the cases in this study. In habitual dislocation, there is downward, forward, and backward instability of the shoulder joint, and dislocation or subluxation of the shoulder occurs involuntarily when the joint assumes a certain position, which differs for each patient. Habitual dislocation accounted for 9.4% of the cases in our study. Habitual dislocation differs from traumatic recurrent shoulder dislocation, which was not covered by this study. In this study, 93% of habitual dislocation and subluxation were of the posterior type in which posterior subluxation occurs when the arm is raised in a forward elevated position of approximately 90° to 100°. The remaining 7% of habitual dislocation was of the anterior type in which anterior subluxation or dislocation occurs when the arm is raised between 90° and the pivotal position.
J Shoulder Elbow Surg Volume 10, Number 2
In sustained subluxation, there is downward, forward, and backward instability of the shoulder joint, and the shoulder joint is in a permanent state of anterior subluxation. The condition is extremely rare and accounted for only 0.3% of the cases in this study.
CASES AND METHOD From April 1985 to April 1999, 12,949 patients (14,218 shoulders) visited the Shoulder Disorder Clinic at Matsudo Orthopaedic Hospital, and atraumatic shoulder instability was diagnosed in 511 patients (919 shoulders). Four hundred eight patients (79.8%) exhibited atraumatic shoulder instability in both shoulders. For this study, we followed the natural course of atraumatic shoulder instability in 573 shoulders of 341 patients for 3 years or more. We excluded patients whose clinical record was incomplete or who underwent rehabilitation. However, we did include patients who used nonsteroidal anti-inflammatory drugs, ointment, or medicated skin patches for 2 or 3 weeks. Male patients numbered 145 and accounted for 241 cases. They ranged in age from 5 to 46 years, with an average age of 18.9 years. Female patients numbered 196 and accounted for 332 cases. They ranged in age from 8 to 51 years, with an average age of 21.1 years. The follow-up period was between 3 and 11 years, with an average of 4 years and 6 months. The breakdown of the 573 cases of atraumatic shoulder instability in this study was as follows: 476 cases of loose shoulder, 49 cases of voluntary dislocation, 56 cases of habitual dislocation, and 1 case of sustained subluxation. For this study, a diagnosis of atraumatic shoulder instability required that the condition had not been caused by trauma and that at least 3 of the following 5 conditions were present: 1. Presence of the sulcus sign, induced by downward traction when the arm was held at the side both in the internally rotated position and in the externally rotated position 2. Forward instability in which the humeral head moved forward past the glenoid rim either partially or completely as a result of the load and shift test 3. Backward instability in which the humeral head moved backward past the glenoid rim either partially or completely as a result of the load and shift test 4. An increase in the rotatory range of motion in zero position 5. Outward slipping of the humerus evident on a plain radiograph taken in zero position. Of the 573 cases of atraumatic shoulder instability in this study, 423 cases (73.8%) met all 5 criteria, 109 cases (19%) met 4 criteria, and 41 cases (7.2%) met 3 criteria. To measure the rotatory range of motion in zero position, 2 photographs of each patient in supine position were taken with a digital camera, and the results were measured on a computer display. The arm was placed in a forward elevated position of 150°, with a 30° wedge-shaped pillow underneath to prevent the degree of elevation from becoming larger. One photograph showed the elbow bent at 90° with the shoulder in maximum external rotation, and the other photograph showed the shoulder in maximum internal rotation. The average rotatory range of motion in
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zero position in this study was 93.1°. For persons with normal shoulders (we examined 157 normal shoulders of 88 persons) with the factor of age averaged in (average age was 20.7 years), the average rotatory range of motion in the zero position was 72.7°. The rotatory range of motion in the zero position of our atraumatic shoulder instability patients was significantly greater than in those without atraumatic shoulder instability (P < .01). For the purposes of this study, we excluded patients with a Hill-Sachs lesion, a Bankart lesion, or subscapular leakage because they did not fulfil the conditions for atraumatic shoulder instability. We conducted follow-up evaluations of the patients with atraumatic shoulder instability every 3 to 6 months, taking into consideration all changes in shoulder instability.
RESULTS Change in shoulder instability without progression to another disorder In 26 cases (5.6%) of loose shoulder and 1 case (1.8%) of habitual dislocation, there was definite improvement of shoulder joint stability. In 2 cases of loose shoulder (0.4%) and in 2 cases of habitual dislocation (3.6%), there was a definite increase in shoulder joint instability (Table I). Thus, in 31 (5.4%) of the cases in this study, we were able to detect change in shoulder joint instability without any shift of disorder. Shift of disorder In our follow-up, 50 (8.7%) of the cases in this study underwent one or more shifts of disorder. As Table II shows, the shifts of disorder in this study showed a great deal of variation. Spontaneous recovery In the course of follow-up, we observed spontaneous recovery with the clinical disappearance of shoulder joint instability in 43 cases of loose shoulder (9%) and in 7 cases of habitual dislocation (12.5%) (Table III), a total of 8.7% of the cases in this study. Women accounted for 28 of the cases and men 22. For women, the age of spontaneous recovery ranged from 14 to 39 years, with an average of 20.1 years. Of the 28 female cases, 24 cases (85.7%) recovered at 24 years or younger. For men, the age of spontaneous recovery ranged from 9 to 29 years, with an average of 16.4 years. Of the 22 male patients, 21 cases (95.5%) recovered at 20 years or younger. Investigation of the relation between sports and spontaneous recovery showed that 97 patients (162 cases) played such overhead sports as baseball, softball, volleyball, handball, javelin throwing, tennis, badminton, and dodge ball. Of those who stopped playing overhead sports, 26.9% (7 of 26 cases) recovered spontaneously. On the other hand, only 3.1% of those who continued to play overhead sports (4 of 127 cases) recovered spontaneously (Figure 1). There were no spontaneous recoveries among the 9
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cases that changed from overhead sports to non-overhead sports. As for non-overhead sports, we found that 73 patients (120 cases) played some kind of non-overhead sport. The rate of spontaneous recovery for those who stopped playing non-overhead sports was 20.8% (5 of 24 cases) as opposed to 15.2% (14 of 92 cases) for those who continued to play non-overhead sports (Figure 2). However, there were no spontaneous recoveries among the 4 cases who changed from nonoverhead sports to overhead sports. In addition, there were no spontaneous recoveries among 9 patients (18 cases) who exhibited general joint laxity and Endo type III loose shoulder (downward subluxation recognized in a radiography taken in standing position without any load). One case each of loose shoulder and habitual dislocation relapsed after spontaneous recovery. All in all, in our follow-up, 22.9% of the cases in this study (131 of 573 cases) exhibited some change in shoulder joint instability, be it improvement in shoulder stability, increase in shoulder instability, shift of disorder, or spontaneous recovery. The age of onset of atraumatic shoulder instability among those who exhibited change in shoulder joint instability ranged from 4 to 39 years, with an average age of 14.6 ± 5.4 years (mean ± SD). On the other hand, the age of onset of atraumatic shoulder instability among those who did not exhibit change in shoulder joint instability ranged from 4 to 50 years, with an average of 19.4 ± 9.4 years. There was a statistically significant difference in the age of onset between these two groups (P .01).
DISCUSSION As is well known, atraumatic shoulder instability commonly strikes the young. In the course of our long-term follow-up, we frequently encountered shifts of disorder and spontaneous recoveries. We came to see that in many cases, atraumatic shoulder joint instability changes often. The shift of disorder among loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation led us to the conclusion that they are all variations of the same disorder: atraumatic shoulder instability. The age of onset in patients who exhibited change in shoulder joint instability was statistically significantly lower than for those patients who did not exhibit change in shoulder joint instability. Except in the cases of general joint laxity and Endo type III loose shoulder, atraumatic shoulder instability that develops at an early age is easily influenced by the amount of physical activity in which patients engage, making it reasonable to expect spontaneous recovery. The incidence of spontaneous recovery in the group that discontinued overhead sports was 8.7 times greater than in the group that continued to play overhead sports. Furthermore, in the group that changed from non-overhead sports to overhead sports, there were no sponta-
J Shoulder Elbow Surg March/April 2001
Table I Change in shoulder instability without any shift of disorder Disorder (N)
Improvement
Increase in shoulder instability
26 (5.6%) 1 (1.8%)
2 (0.4%) 2 (3.6%)
Loose shoulder (476) Habitual dislocation (56)
Table II Shifts of disorder Shifts of disorder
Shoulders
LS → VD LS → HD VD → HD LS → VD → LS LS → VD → HD → VD VD → HD → LS LS → VD → HD → LS LS → VD → HD LS → VD → HD → LS → HD LS → HD → LS HD → LS → HD HD → VD VD → LS HD → LS VD → SS
8 11 8 1 1 3 1 2 1 3 1 3 4 2 1
LS, Loose shoulder; VD, voluntary dislocation; HD, habitual dislocation; SS, sustained subluxation.
Table III Spontaneous recovery Disorder (N) Loose shoulder (476) Habitual dislocation (56)
Shoulders
Incidence
43 7
9.2% 12.5%
neous recoveries. When we consider these facts, we can see that overhead sports are an impediment to atraumatic shoulder instability healing naturally. The possibility of spontaneous recovery should be an extremely important consideration when deciding on the need for surgery. For instance, habitual dislocation is involuntary. It is easy to think that surgery is appropriate as soon as a diagnosis is made. Indeed, we ourselves thought so until we encountered the spontaneous recovery of atraumatic shoulder instability. However, since confirming that spontaneous recovery of atraumatic shoulder instability does occur, we set a follow-up period of at least 2 years before considering surgery. If pain occurs during that period, or if use of the shoulder in daily activities becomes severely restricted, then the time has come for operative treatment. Even when a loose shoulder joint goes through repeated dislocations or subluxations, there is little risk of intra-articular lesions. However, when pain occurs, the possibility of intra-articular lesion becomes impossible
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Figure 1 Incidence of spontaneous recovery in the group that discontinued overhead sports and in the group that continued overhead sports.
Figure 2 Incidence of spontaneous recovery in the group that discontinued non-overhead sports and in the group that continued non-overhead sports.
to deny, and it is no longer possible to leave atraumatic shoulder instability untreated. Once this view is adopted, operative treatment of atraumatic shoulder instability can be seen as deciding itself. Loose shoulder is a stubborn complaint, but overall symptoms are mild. This is why the need for operative treatment is rare. In the case of voluntary dislocation, it is possible to teach the patient to prevent dislocation through greater awareness. If a person can learn to prevent voluntary dislocation that has become
a habit, surgery is not necessary. The real problematic types of atraumatic shoulder instability are voluntary dislocation that a patient cannot learn to control and habitual dislocation. However, even in the case of these two types of atraumatic shoulder instability, unless pain appears or daily activities become severely restricted, it is best to set a follow-up period of several years with the hope of eventual spontaneous recovery, and avoid unnecessary surgery as much as possible. An exception to this rule should be made for
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patients with habitual dislocation who become depressed because they are unable to play sports. In such cases, surgeons should not hesitate to operate.
We would like to express our thanks to Mr Charles Thorpe for his help in preparing this paper.
Summary We followed 573 cases of atraumatic shoulder instability for 3 years or more. In 31 cases (5.4%) in this study, we found a change in shoulder instability with no shift of disorder. In 50 cases (8.7%), there was a shift of disorder between loose shoulder, voluntary dislocation, habitual dislocation, and sustained subluxation. In 50 cases (8.7%), we observed spontaneous recovery. The incidence of spontaneous recovery in the group that gave up overhead sports was 8.7 times greater than in the group that continued to play overhead sports. The incidence of spontaneous recovery in the group that gave up non-overhead sports was only 1.4 times greater than in the group that continued to play non-overhead sports. Before deciding on operative treatment for atraumatic shoulder instability, it is best to bear in mind the possibility of spontaneous recovery and set an adequate follow-up period.
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