Increased Risk of Posterior Glenoid Labrum Tears in Football Players

Transcription

1 Escobedo et al. Posterior Labral Tears in Football Players Musculoskeletal Imaging Clinical Observations 193.FM 11/30/06 A C M E D E N T U R I C A L I M A G I N G Eva M. Escobedo 1,2 Michael L. Richardson 1 Yousuf B. E. Schulz 1,3 John C. Hunter 1,2 John R. Green III 4 Kevin J. Messick 5 AJR 2007; 188: X/07/ American Roentgen Ray Society Y O F Escobedo EM, Richardson ML, Schulz YBE, Hunter JC, Green JR III, Messick KJ Keywords: glenoid labrum, MR arthrography, MRI, musculoskeletal imaging, shoulder, sports medicine, trauma DOI: /AJR Received February 17, 2005; accepted after revision August 12, Department of Radiology, University of Washington Medical Center, Roosevelt Clinic, Seattle, WA Present address: Department of Radiology, University of California Davis Medical Center, 4860 Y St., Ste. 3100, Sacramento, CA Address correspondence to E. M. Escobedo. 3 Present address: Desert Radiologists, Las Vegas, NV Departments of Orthopaedics and Sports Medicine, University of Washington Medical Center, Seattle, WA University of Washington Intercollegiate Athletics, Seattle, WA Increased Risk of Posterior Glenoid Labrum Tears in Football Players OBJECTIVE. This study was designed to test our hypothesis that football players with shoulder pain, shoulder instability, or both requiring MR arthrography for evaluation are at an increased likelihood relative to non football players for having a tear of the posterior glenoid labrum. CONCLUSION. We conclude that posterior glenoid labrum tears are more prevalent in football players than in non football players. his study has its genesis in an anecdotal observation that our uni- T versity football team seemed to have an unusually high number of players with injuries of the posterior glenoid labrum. A literature review turned up surprisingly little prior work in this area. Consultation with our orthopedics colleagues revealed that the prevalence and mechanism of posterior labral tears remain poorly understood. Classically, posterior shoulder instability has been considered to be less common than its anterior counterpart in the general population [1 3]. There has been a relative paucity of clinical research regarding this injury in contact-sports athletes and, specifically, in football players. However, two series have described posterior glenoid labrum injuries in athletes [4, 5], predominately football players. In both of these studies the patient cohort was small with no control group used. Mair et al. [4] suggested that these posterior labral injuries might be a type of occupational hazard for contact athletes. The mechanism they proposed is that this injury is the result of posteriorly directed forces on the shoulder during blocking, leading to excessive shear forces directed against the posterior labrum. They further postulated that repeated episodes of this microtrauma eventually lead to posterior labral tears. We sought to evaluate our population of patients presenting with shoulder pain or instability to test our hypothesis that football players are at increased risk relative to non football players for development of a tear of the posterior glenoid labrum. Materials and Methods Patients After obtaining written approval from our human subjects committee, a retrospective chart review was performed of all MR arthrograms of the shoulder obtained in our department from May 2001 through February A total of 171 shoulder MR arthrograms in 162 patients were obtained during that time period. Twenty-one of these patients had undergone shoulder surgery before imaging. Five of these surgeries involved the posterior glenoid labrum: two labral tear repairs, two débridements for osteoarthritis, and one removal of a spinoglenoid ganglion. Because we were primarily evaluating the posterior labrum, those five studies were excluded. Thus, 166 shoulder MR arthrograms from 157 patients were used for our study. All of these patients presented with shoulder pain, clinically suspected instability, or both. The patients ranged in age from 15 to 74 years (mean age, 32 years) and included 56 females and 101 males. Twenty patients (all male; age range, years; mean age, 20 years) were competitive football players. One player was at the high school level and the others were at the collegiate level. The football players included three defensive linemen, one offensive lineman, three running backs, four defensive backs, four linebackers, three receivers, one center, and one quarterback. Only two of the 20 players reported a clear history of a single trauma to the shoulder. One hundred thirty-seven patients (age range, years; mean age, 34 years) did not play football (male female ratio, 81:56). Of these, 13 patients were known on the basis of their clinical history to be competitive athletes. This included three softball players, three baseball pitchers, three volleyball players, two swimmers, one gym- AJR:188, January

2 Escobedo et al. Fig year-old male collegiate football player with posterior labral tear. Axial T1-weighted gradient-echo MR arthrographic image shows posterior labral detachment (arrow). nast, and one hockey player. All were at the collegiate level except two: a high school softball player and baseball pitcher. From the 137 non football players group, a subgroup of patients who were age- and sex-matched to the football players was separated out. This subgroup comprised 20 males who ranged in age from 15 to 22 years (mean, 19 years). All of the football players in our study engaged in weight training, including the bench press. The number of non football players engaging in weight training is not known. Imaging Evaluation MR arthrographic imaging was performed on a 1.5-T unit (Signa, GE Healthcare). Before imaging, we injected each shoulder under fluoroscopic guidance with ml of gadolinium solution containing a 50:50 mixture of 3.25 mmol/l gadodiamide (Omniscan, Amersham Health) and 30.5% iopamidol (Isovue-M 300, Bracco Diagnostics). Each patient was imaged using the following protocol: fast spin-echo T1-weighted fat-saturated sequences (TR range/te, /12; matrix, ; echo train, 2) in the coronal oblique and sagittal oblique planes; fast spin-echo T2-weighted fatsaturated sequences (3,450 4,300/61; matrix, ; echo train, 12) in the coronal oblique, sagittal oblique, and axial planes; and axial T1-weighted gradient-echo sequences (TR/TE, 52/10; matrix, ; slice thickness, mm). Fig year-old male collegiate football player with posterior labral detachment due to posterior labrocapsular periosteal sleeve avulsion and with associated cartilage injury. Axial T1-weighted gradient-echo MR arthrographic image shows posterior labral avulsion remains attached by periosteum (arrow). There is also associated articular cartilage injury (arrowhead). All shoulder MR arthrograms were interpreted and dictated by a fellowship-trained musculoskeletal radiologist at the time they were obtained. These radiology reports were reviewed for a mention of posterior labral tear. Six reports were considered equivocal for posterior labral tear. These MR arthrography studies were reviewed again in consensus by two fellowship-trained musculoskeletal radiologists, and a decision was made about whether a posterior labral tear was present or absent. Fraying was not considered to be a tear. The MR arthrograms considered positive for posterior labral tears were reviewed by the same two musculoskeletal radiologists who determined the nature of the tear: Each was categorized as either a labral substance tear or a labral detachment. A substance tear was diagnosed when contrast material on T1-weighted images or fluid on T2-weighted images extended into the substance of the posterior labrum, interrupting its normal contour. An avulsion of the labrum was considered a detachment. Detachments included reverse Bankart type lesions, which were characterized by a labrocapsular avulsion with torn periosteum, and posterior labrocapsular periosteal sleeve avulsions (POLPSAs), in which the posterior labrum is avulsed but remains attached to the glenoid by a sleeve of periosteum [5, 6]. For each study, the presence of anterior and superior labrum anterior-to-posterior (SLAP) tears, cartilaginous lesions, rotator cuff tears, and biceps tendon tears was also noted. Fig year-old male collegiate football player with posterior labral tear and cartilage injury. Axial T1- weighted gradient-echo MR arthrographic image shows posterior labral detachment (arrow) and associated articular cartilage injury (arrowhead). The results of these MR studies were then compared with surgical results when available. Arthroscopic or surgical correlation was available for 21 of the 27 football players shoulders and in 41 of the 137 non football players shoulders. Statistics Statistical analysis was performed using 2 2 contingency table analysis and the exact permutation test with StatXact (Cytel Software). The odds ratio and its CI were also calculated using the exact permutation test. Results Football Players Twenty-seven shoulder MR arthrograms (10 left, 17 right) were obtained in 20 football players (seven bilateral). Twenty-six (96%) of the 27 football players shoulder MR arthrograms revealed some type of labral tear. Fifteen (56%) of 27 showed a posterior labral tear. Considering the number of players rather than the number of shoulders, 11 (55%) of the 20 players had at least one posterior labral tear. Ten (67%) of the 15 posterior labral tears in football players were considered to be labral detachments (Fig. 1). The remaining five tears were considered substance tears. Of the 10 detachments, three (30%) were considered POLPSA lesions (Fig. 2). Six (60%) of the 10 detachments were associated with posterior glenoid articular cartilage injuries (Figs. 2 and 3). 194 AJR:188, January 2007

3 Posterior Labral Tears in Football Players TABLE 1: Posterior Labral Tears in Football Players Versus Football Players Total Posterior labral tear 11 (55) 10 (7) 21 (13) No posterior labral tear Total TABLE 2: Age- and Sex-Matched Comparison of Football Players Versus Football Players Total Posterior labral tear 11 (55) 2 (10) 13 (33) No posterior labral tear Total TABLE 3: Posterior Labral Tears in Competitive Athletes Versus Nonathletes All Competitive Athletes Nonathletes Total Posterior labral tear 13 (39) 8 (6) 21 (13) No posterior labral tear Total TABLE 4: Posterior Labral Tears in Football Players Versus Other Athletes Football Players Other Competitive Athletes Total Posterior labral tear 11 (55) 2 (15) 13 (39) No posterior labral tear Total Of the 15 shoulders with posterior labral tears, four (27%) also had associated anterior labral tears and four (27%) also had SLAP tears (one extending into a posterior labral tear). Eleven (41%) of the 27 football players shoulders had other types of labral injuries depicted on MR arthrograms without associated posterior labral tears. These included seven shoulders with isolated anterior labral tears, two with isolated SLAP lesions, and two with both. One hundred thirty-nine MR arthrograms were obtained in 137 non football players (two bilateral). Of the 137 non football players, 10 (7%) showed posterior labral tears, none of which was bilateral. Six (60%) of 10 posterior labral tears were detachments. Two of these six were considered to be POLPSA lesions. The remaining four were substance tears. Of the 10 posterior labral tears, two were associated with anterior labral tears and two with SLAP lesions. Twenty-one (15%) of 139 non football players shoulders showed anterior labral tears, SLAP tears, or both with no associated posterior tear. One hundred eight (78%) of 139 had no labral abnormalities. Two (15%) of the 13 competitive athletes who were not football players had a posterior labral tear; one was considered a detachment. Thus, of the 25 shoulder MR arthrograms that showed posterior labral tears, 15 were in football players, two were in non footballplaying competitive athletes, and eight were in nonathletes. Inciting activities in the nonathletes included two falls, one motor vehicle accident, one boating accident, one waterskiing accident, an injury while power lifting, and two unknown events. Surgical correlation was available for 16 of the 25 MR arthrograms that showed posterior labral tears. There was agreement in 14 of the 16 cases. Of the two discordant cases, one was called a probable healed tear on MRI and was not seen on arthroscopy, and in the second case, there was no mention of the posterior labrum in the operative report. Data Analysis Statistical analysis was performed using 2 2 contingency table analysis and the exact permutation test with StatXact (Cytel Software). The odds ratio and its CI were also calculated using the exact permutation test. When we compared the 20 football players with the other 137 subjects in our study, we found a highly statistically significant association between playing football and the presence of posterior labral injury (p = ) (Table 1). We also calculated the common odds ratio for this comparison and found that football players are 15.0 times more likely to have a posterior labral injury than non football players (p = ). The 95% CI for this odds ratio was Considering that the presence of other associated injuries in addition to posterior labral tears had the potential of skewing the data, we eliminated these studies (eight football players and four non football players) and recalculated the data for those with isolated posterior labral tears. Repeat statistics continue to indicate a strong association between football playing and posterior labral injuries (p =0.028). Comparing the 20 football players with the age- and sex-matched group of non football players, we again found a highly significant association between playing football and posterior labral tear, with a p value of (Table 2). The common odds ratio was 10.3, with a 95% CI of Next, we combined the 20 football players with the 13 other competitive athletes and compared these athletes against the remaining 124 subjects in our study (Table 3). Again we found a highly statistically significant association between competitive athletics and the presence of posterior labral injury (p = ). When we calculated the common odds ratio for this comparison, we found that these athletes are 9.23 times more likely to have a posterior labral injury than nonathletes (p = ). The 95% CI for this odds ratio was Finally, we compared the 20 football players with the 13 other competitive athletes in AJR:188, January

4 Escobedo et al. our study (Table 4). We found a statistically significant association between the type of athletics and the presence of posterior labral injury (p = 0.033). The common odds ratio for this comparison was 6.3. The p value of and the 95% CI of indicate that the odds ratio is marginally statistically significant and suggest that a larger sample size might reveal a more statistically significant odds ratio between the two groups. There was no statistically significant association between playing football and the presence of a posterior detachment (p =1.0). Discussion There has been much confusion and controversy related to the classification, terminology, and treatment of posterior labral and capsular injuries [1, 3, 7 9]. In terms of classification, differentiation of acute traumatic posterior dislocations from recurrent atraumatic instability has been emphasized. In reality, there is a wide continuum of the degree of force that may lead to posterior labral injury, posterior capsular injury, or both injuries, ranging from a single frank posterior dislocation; to a single acute force that is severe, but not severe enough to cause posterior dislocation; to multiple episodes of posteriorly directed microtrauma. Finally, some patients with posterior instability have no history of trauma [4, 8 11]. Glenoid dysplasia has been implicated as a cause of posterior instability [10] and more recently has been associated with posterior labral tears [12]. We strongly suspect that most of the lesions seen in our population of football players were caused by repetitive microtrauma because most of the football players did not report a single inciting episode of trauma. We did not evaluate for the presence of glenoid dysplasia in our study. In addition to the various causes of posterior labral tears and instability, the findings at surgery in those with posterior instability may be varied and may include posterior labral tears or detachments, glenoid rim cartilage or bone fractures, and posterior capsular injuries [1, 11, 13]. There is also a poor understanding of the mechanism leading to traumatic posterior labral and capsular injuries and posterior instability. A mechanism often described is injury occurring when the arm is flexed to 90, adducted, and internally rotated at the time of contact [1, 9, 11]. A mechanism for a specific type of posterior labral tear in contact-sports athletes such as football players has been proposed by Mair et al. [4], who described posterior labral detachments in nine athletes: eight football players, seven of whom were offensive linemen, and one lacrosse player. Five also had glenoid chondral surface injuries, but none had capsular injuries or instability. The proposed mechanism of injury was blocking of an opponent when the shoulder is positioned in 90 of flexion with the elbows locked. With contact, the shoulder undergoes a posteriorly directed force leading to a significant shearing force that is transferred to the posterior labrum. The preponderance of labral detachments and articular cartilage injuries as opposed to labral substance tears and capsular injuries in these athletes was thought to be caused by a major compressive force due to protracting the shoulders in anticipation of contact. This results in a shear force directed at the glenoid and labrum. Multiple episodes of this form of microtrauma eventually lead to posterior labral detachment or tears. Yu et al. [5] described POLPSA lesions in six patients, four of whom were football players. Because POLPSA lesions are considered a form of labral detachment, the findings reported by Yu et al. also support the theory of a shear-type injury directed at the labrum. With POLPSA lesions, even though the capsule remains intact, generally there is instability due to stripping of the periosteum, resulting in a more patulous posterior capsule [5, 6]. Instability was detected in all subjects in that study [5], unlike the study by Mair et al. [4]. In the two studies mentioned [4, 5], subjects were selected on the basis of having a particular posterior labral injury: either a detachment without capsular injury [4] or a POLPSA lesion [5]. Although the labral detachments seen in the former study were not clearly described, it is possible that these were also POLPSA lesions and not reverse Bankart type lesions, which by definition involve disruption of the capsule [13]. Because other types of posterior labral injuries were not addressed, we chose to look at all posterior labral injuries in our general population of people with shoulder pain or instability to assess the prevalence in football players versus a control group. We found that posterior labral injuries in general are more prevalent in football players than in non football players. Although we found a preponderance of labral detachments versus labral substance tears, the difference was not statistically significant when compared with non football players. We believe that the mechanism leading to posterior labral injury proposed by Mair et al. [4] is at least partially a valid one. The injuries they described were thought to be specific to offensive linemen [4]. However, in our population of football players, we found posterior labral tears in those playing other positions as well. One explanation could be that the defensive players may be countering the offensive technique of blocking with outstretched arms using a similar technique. In our non football player group, posterior labral tears occurred in a hockey player, a patient injured in an automobile accident, a yard maintenance worker who had fallen off of a ladder, a collegiate softball catcher, and a patient injured in a waterskiing accident. Other studies have shown posterior labral injuries from a variety of activities in addition to football. Injuries in weightlifters, wrestlers, hockey players, and lacrosse players and traumatic injuries from falls, waterskiing, and motor vehicle accidents have been mentioned in more than one other study [2, 4 7, 9 11, 14, 15]. The finding of this injury in non football players suggests that posterior labral tears could potentially be seen in any patient who undergoes a force that displaces the humeral head posteriorly relative to the glenoid. For a number of reasons, the presence or absence of instability in our subjects was not specifically addressed. First, we had incomplete information regarding the clinical examinations of our patients. Also, the presence or absence of instability while the patient was under anesthesia was not consistently noted in the operative reports. Finally, the definition and diagnosis of instability can vary among individual orthopedic surgeons [3]. Thus, we believe that this determination is beyond the scope of our study. One controversial consideration in our study is whether aspects of an athletic training regimen could be contributing to these posterior labral injuries. Weight training, for example, is almost universal in football players, including all of the players in our series. One patient in the series reported by Yu et al. [5] was a non football playing weightlifter. Mair et al. [4] do not believe weight training contributes significantly to the development of posterior labral injuries because they have not seen this injury in bench-pressing athletes who were not involved in football or in any of the previously mentioned sports. Bench-pressing did, however, exacerbate shoulder symptoms in their subjects. We find it plausible that bench-pressing heavy weights could at least contribute to posterior labral injuries by the previously discussed mechanism of an anticipated posteriorly directed force to the shoulder, and we think that this issue deserves further study. 196 AJR:188, January 2007

5 Posterior Labral Tears in Football Players Limitations A potential weakness of our study is its relatively small patient cohort. However, our study population is significantly larger than that of previous studies [4, 5] and also includes a control group. Despite this relatively small cohort of players, the association between playing football and posterior labral tear is highly statistically significant. Likewise, the odds ratio of the proportion of football players to non football players with posterior labral tears is highly significant, both statistically and clinically. Admittedly, our patient population is a select subgroup of patients seen by sports medicine physicians and may not truly represent the general population. However, we believe that our patient population is representative of the patient population seen by other sports medicine physicians, orthopedic surgeons, and musculoskeletal radiologists. The comparison of football players to an age- and sexmatched control group lends further credence to our findings. Because our study was limited to examining the prevalence of posterior labral tears, we did not discuss the high percentage of other shoulder injuries that were present as well. Whether these injuries are associated with the same mechanism that produces posterior labrocapsular injuries or whether they have been caused by a separate mechanism of injury cannot be determined. Perhaps these posterior labral injuries are not a result of a single simple mechanism of injury, but of a more complex mechanism that involves other quadrants of the glenohumeral joint as well. The training regimen of football players is rigorous and could also play a part in the development of these varied injuries. A final limitation of our study is that we have surgical proof of the MR diagnosis for only 16 of 25 labral tears. However, MR arthrography has been shown to be an accurate technique for evaluating the capsuloligamentous complex and labrum [13, 16], and we are confident diagnosing posterior labral lesions using this technique, especially with the exclusion of equivocal findings. Conclusions Our study results suggest that posterior labral injuries are almost 15 times more common in football players than in the general population. In addition, similar injuries occur in non football players whose shoulders are likely subjected to a similar posteriorly directed force leading to posterior translation of the humeral head relative to the glenoid. We think that most of the posterior labral tears in our population resulted from multiple episodes of microtrauma. Given this mechanism, it is plausible that weighttraining regimens may also play a significant role in the development of these injuries. Further study of these and other etiologic factors is warranted. If significant associations can be shown between posterior labral tears and injuries specific to a sport or type of weight training, those findings could lead to changes in playing practices, athletic gear, and weight-training regimens. Finally, an increased awareness of posterior labral tears among interested physicians may lead to a better understanding of the injury. References 1. Pollock RG, Bigliani LU. Recurrent posterior shoulder instability: diagnosis and treatment. Clin Orthop 1993; 291: Abrams JS. Arthroscopic repair of posterior instability and reverse humeral glenohumeral ligament avulsion lesions. Orthop Clin N Am 2003; 34: Minkoff J, Stecker S, Cavaliere G. Glenohumeral instabilities and the role of MR imaging techniques: the orthopedic surgeon s perspective. Magn Reson Imaging Clin N Am 1997; 5: Mair S, Zarzour R, Speer K. Posterior labral injury in contact athletes. Am J Sports Med 1998; 26: Yu J, Ashman C, Jones G. 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