Posterior Labral Injury in Contact Athletes*

Transcription

1 /98/ $02.00/0 THE AMERICAN JOURNAL OF SPORTS MEDICINE, Vol. 26, No American Orthopaedic Society for Sports Medicine Posterior Labral Injury in Contact Athletes* Scott D. Mair, MD, Robert Hap Zarzour, ATC, and Kevin P. Speer, MD From the Division of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina ABSTRACT Nine athletes (seven football offensive linemen, one defensive lineman, and one lacrosse player) were found at arthroscopy to have posterior labral detachment from the glenoid. In our series, this lesion is specific to contact athletes who engage their opponents with arms in front of the body. All patients had pain with bench pressing and while participating in their sport, diminishing their ability to play effectively. Conservative measures were ineffective in relieving their symptoms. Examination under anesthesia revealed symmetric glenohumeral translation bilaterally, without evidence of posterior instability. Treatment consisted of glenoid rim abradement and posterior labral repair with a bioabsorbable tack. All patients returned to complete at least one full season of contact sports and weightlifting without pain (minimum follow-up, 2 years). Although many injuries leading to subluxation of the glenohumeral joint occur when an unanticipated force is applied, contact athletes ready their shoulder muscles in anticipation of impact with opponents. This leads to a compressive force at the glenohumeral joint. We hypothesize that, in combination with a posteriorly directed force at impact, the resultant vector is a shearing force to the posterior labrum and articular surface. Repeated exposure leads to posterior labral detachment without capsular injury. Posterior labral reattachment provides consistently good results, allowing the athlete to return to competition. Sport-specific injury resulting from cumulative stress to a particular area of the body is a commonly reported injury. Lateral epicondylitis occurs with such frequency in participants of racquet sports that the term tennis elbow is well known to the general public. Footballer s ankle was * Presented at the 23rd annual meeting of the AOSSM, Sun Valley, Idaho, June Address correspondence and reprint requests to Kevin P. Speer, MD, Box 3371, Duke University Medical Center, Durham, NC No author or related institution has received any financial benefit from research in this study. first described in 1950, and more recent reports have documented the cumulative trauma inherent to the ankles of soccer players. 6,12 Other well-documented sport-specific injuries attributed to repetitive stress include valgus extension overload in the elbow of the baseball pitcher and wrist pain syndrome in the gymnast. 8,9,20 We describe an injury, posterior glenoid labral detachment, which in our series is unique to contact athletes, with a particularly high incidence in football offensive linemen. This lesion appears to be part of a spectrum of injury to the posterior labrum and posterior glenoid chondral surface that occurs in contact sports. Bench pressing, universally practiced by contact athletes, exacerbates symptoms and may further contribute to this injury. We believe that posterior labral detachment is the result of repeated exposure to posteriorly directed shear forces to the shoulder, which could be considered to be a type of occupational hazard of contact athletics. In 1981, the National Collegiate Athletic Association (NCAA) changed its rules to allow an offensive lineman to block with his arms fully extended and hands open while retreating. In 1985, the rules were further liberalized to allow blocking in this manner in all situations. We believe that when the lineman blocks with his arms in front of his body and his elbows extended, he places himself at risk for posterior labral injury. This may be particularly true when an undersized lineman attempts to gain an advantage by locking out (straightening) his elbows to compensate for inferior triceps strength as compared with his opponent. We hypothesize that a posteriorly directed blow with the arm in this position results in a forceful posterior shear stress transmitted to a shoulder in which a large glenohumeral compressive force already exists. We report on nine contact athletes found to have posterior labral detachment from the glenoid without evidence of clinically discernible posterior instability. The purpose of this report is to describe the hypothesized cause of this lesion and to make recommendations with regard to diagnosis and treatment. MATERIALS AND METHODS Nine contact athletes were found to have a posterior labral detachment, all confirmed at the time of shoulder arthro- 753

2 754 Mair et al. American Journal of Sports Medicine scopy by the senior author (KPS). Eight of these athletes were football linemen (seven offensive, one defensive) and the other athlete was a lacrosse player. Seven patients were college athletes and the other two were high school athletes. The average age of these male athletes was 18.8 years (range, 16 to 21). The dominant arm was involved in six patients. None had prior shoulder symptoms, history of dislocation (anterior or posterior), or had undergone prior shoulder surgery. Three patients had seen another physician and been diagnosed as having a rotator cuff strain or tendinopathy and treated conservatively. Only two players could recall a specific moment of injury. Each of these athletes, an offensive lineman who was blocking and a lacrosse player holding his stick in front of his body, suffered a posteriorly directed blow with the shoulder forward-flexed and the elbow locked in extension. The remaining players had an insidious onset of symptoms. Complaints about the shoulder were vague and only three athletes implicated a posterior source of discomfort. All described a diffuse aching that was greatly exacerbated by contact sports and bench pressing. Consistently, the pain described with weightlifting was not associated with locking out but occurred in the early phase of the press. The majority of the patients were symptom-free when not participating in athletic endeavors; only one had symptoms with activities of daily living, and these were mild. Among the nine patients, duration of symptoms before surgical intervention averaged 7.4 months (range, 3 to 20). Physical examination revealed that all patients had posterior joint line tenderness; three also had anterior tenderness. All patients had a full range of motion, and only two had mild pain with full active elevation of the shoulder. All patients had equivocal to positive impingement signs. Four patients had notable clicking with posterior translation of the loaded shoulder. None had clicking in the contralateral shoulder preoperatively. One patient subsequently developed symptoms after his return to play, along with clicking on examination and a positive CT arthrogram in the opposite shoulder. Posterior translation during instability examination of the injured shoulder was painful in all patients; however, none of the athletes had increased posterior translation as compared with the contralateral shoulder. No patients had positive anterior apprehension tests nor evidence of anterior instability. Plain radiographs were normal in all patients. Seven patients underwent CT arthrography and two underwent MRI. In our experience, MRI is less accurate in patients with a coat size of 50 or above. In these patients, we use CT arthrogram rather than MRI. In five of the seven patients undergoing CT arthrogram, and one of two imaged by MRI, the posterior labral injury was seen or suggested. In those patients with a positive CT arthrogram, a sliver of contrast could be visualized interspersed between the posterior labrum and glenoid (Fig. 1). In the patient with a positive MRI, the labrum could be seen to be detached from the glenoid rim. All patients were treated conservatively for a minimum of 6 weeks before surgery with physical therapy for rotator Figure 1. A CT arthrogram showing posterior labral detachment. Contrast material (white, marked by arrow) is seen between the glenoid rim and labrum (gray area). cuff and periscapular strengthening exercises. Symptomatic treatment included cryotherapy to the affected shoulder and nonsteroidal antiinflammatory medications. No patient had significant improvement with conservative treatment; all were unable to bench press with heavy weights or play football effectively. Surgical Technique The arthroscopic procedure was done in the beach-chair position in all patients. A complete glenohumeral arthroscopy was performed with the arthroscope in a posteriorly placed portal. The camera was then changed to an anterior portal. A rasp was used to abrade the glenoid rim in the area of the labral detachment, back to a surface of bleeding bone. A cannulated drill provided by the manufacturer for the 8-mm SURETAC bioabsorbable implant (Acufex Microsurgical, Norwood, Massachusetts) was placed through the posterior portal. The drill bit was then used to engage the detached labrum and place it in its reduced position. A drill hole was placed at the chondral margin. A wire was fitted through this drill with a few millimeters protruding so that the wire remained fixed in bone when the drill itself was withdrawn. The bioabsorbable (polyglycolate) tack was then impacted over this wire by means of a cannulated impactor placed through the posterior cannula (Fig. 2). The tack was inserted under direct arthroscopic visualization. One or two tacks were used to perform the reattachment, depending on the size of the lesion. Postoperative Rehabilitation Patients remained with the arm in a sling for 4 weeks postoperatively. From 4 to 8 weeks, they were allowed active and passive range of motion restricted to 40 of external rotation, 140 of elevation, and internal rotation

3 Vol. 26, No. 6, 1998 Posterior Labral Injury in Contact Athletes 755 Figure 3. Arthroscopic appearance of posterior labral detachment. Figure 2. Bioabsorbable tack placed through a posterior portal, holding the labrum in a reduced position. The glenoid rim has been abraded to promote healing before placing the tack. to the first lumbar vertebra. They also underwent physical therapy for periscapular and rotator cuff strengthening. At 2 months, full range of motion was allowed and strengthening continued. At 3 months, they were allowed to resume lifting weights, and at 4 months they were allowed to return to contact athletics. RESULTS Examination Under Anesthesia All patients were found to have a symmetrical translational examination, including posterior translation. No patient had multidirectional laxity. Arthroscopic Findings The presence of a posterior labral injury, consisting of detachment from the glenoid, was confirmed in all nine patients (Fig. 3). The lesions varied in size, with the largest extending from the 7 o clock to 11 o clock position on the glenoid. The posterior capsule showed no evidence of injury in all patients. The anterior glenoid labrum had a normal appearance, as did the inferior glenohumeral ligament. Five patients had some irregularity in the posterior third of the glenoid chondral surface. In addition to detachment, all nine patients had notable fraying of the posterior labrum or small tears in its substance (Fig. 4). The remainder of the arthroscopic shoulder examination was normal in all cases. There were no intraoperative complications. Figure 4. Severe fraying of posterior labrum in addition to detachment. Postoperative Results All of the nine athletes in this series have had a complete return to unlimited contact sports and bench pressing without pain. All have a full range of motion, equal to preoperative motion and to motion in the opposite side. None of the athletes have a positive impingement sign, posterior apprehension, or pain with loaded posterior translation. There have been no athletes with recurrence of symptoms. The average follow-up was 30 months (range, 24 to 42). Each athlete has completed at least one full season of participation in his sport. Linemen were counseled on return to sports participation to modify their technique, blocking with elbows slightly flexed. Particular attention was given to increasing upper body strength,

4 756 Mair et al. American Journal of Sports Medicine especially the triceps and pectoralis muscles. One athlete in this series was found to have (by history, examination, and CT arthrogram) a similar lesion in the contralateral shoulder during his final season of football, but he elected to attempt to participate without surgical treatment. Since his retirement from competitive contact athletics, he has had no further symptoms. DISCUSSION Bankart 3 first described anterior detachment of the glenoid labrum and its association with shoulder dislocations in More recently, numerous other patterns of labral injury and treatment options for labral abnormalities have been described. In 1983, Pappas et al. 15 contributed the concept of functional instability, describing 19 patients with symptomatic labral injury in the absence of glenohumeral joint instability. These authors concluded that the injured labrum can cause symptoms in a manner analogous to a torn meniscus in the knee, and they obtained consistently good results with open excision of the labral fragments. With the increasing use of shoulder arthroscopy, reports of labral injury have become more common. Series of injuries related to a specific portion of the labrum have been presented and their characteristic symptoms described. Snyder et al. 16 described a series of patients with injury to the superior labrum in the region of the origin of the long head of the biceps tendon (superior labrum from anterior to posterior, or SLAP lesion). In a series of throwing athletes with labral injuries, Andrews et al. 1 noted that 83% (61 of 73) of the tears were in the anterosuperior region. McMaster 11 has described a pattern of anterior labral fraying or tearing producing mechanical symptoms in swimmers. Reports of injury to the posterior labrum have encompassed a wide variety of patient populations and injury mechanisms. Only 2 of the 19 patients with functional instability in the study by Pappas et al. 15 had posterior labral injury. Martin and Garth 10 recently reported 12 posterior labral flap tears in a series of 24 shoulders, predominantly throwing athletes, treated with labral debridement. Three of these athletes were noted to have posterior subluxation during examination under anesthesia. Davidson et al. 5 have described a continuum of the internal impingement lesion in throwing athletes with increased glenohumeral rotation, angulation, and anterior translation resulting in undersurface rotator cuff injury and posterior-superior labral fraying. Finally, numerous authors have reported a variable incidence of posterior labral detachment (reverse Bankart lesion) in patients undergoing surgery for overt posterior glenohumeral instability. Hawkins and Janda 7 noted a posterior labral detachment in 1 of 14 patients; Bigliani et al., 4 in4of35 patients; Papendick and Savoie, 14 in 20 of 41 patients; and Tibone et al., 17 in all 10 of their patients. In our series of nine patients with posterior labral detachment, posterior glenohumeral instability could not be documented by side-to-side translational testing under anesthesia. While a Bankart lesion is thought to be pathognomonic for anterior instability, Hawkins and Janda 7 noted that there are significant structural differences between the anterior and posterior glenohumeral joint with resultant differences in instability patterns. These authors stated that the posterior labrum is loosely attached to the surrounding capsule without ligamentous reinforcement, providing less support than the anterior labrum. The posterior band of the inferior glenohumeral ligament complex is the primary static stabilizer to posterior translation in the shoulder in 90 of abduction. 13 However, Warren et al. 18 found that in the flexed, adducted, and internally rotated shoulder, no posterior subluxation resulted from cutting the infraspinatus muscle, teres minor muscle, and posterior capsule. Only additional incision of the anterosuperior capsule from the 12 o clock to 3 o clock position allowed posterior dislocation. Weber and Caspari 19 were able to produce posterior instability by dislocating cadaveric specimens in the flexed, neutral adducted, and internally rotated position. They found no injury to the anterior capsule or the superior, middle, and inferior glenohumeral ligaments. All specimens had splitting of the posterior capsule, which the authors considered the essential lesion in posterior instability. Six of nine specimens did have posterior labral injury or detachment, although no posterior glenoid articular scuffing was seen. The authors attributed the lack of chondral injury to the absence of muscle tension presupposed in cadaveric testing. These data support our premise that posterior labral detachment need not be associated with posterior glenohumeral instability if injury to the posterior capsule has not occurred. We believe that contact athletics, in particular offensive line play, provide a unique mechanism for production of injury to the posterior labrum without associated capsular injury. Our proposed mechanism of injury differs from the tensile failure of the posterior capsule/ labrum complex that can be seen in throwing athletes, and this difference may account for the lack of discernible posterior glenohumeral instability seen in our patients. While many injuries leading to subluxation of the shoulder joint occur when an unanticipated force is applied, contact athletes are subjected to fully anticipated posteriorly directed forces. With the arm in a position of approximately 90 of flexion, the athlete prepares to take on an opponent with the shoulder musculature fully ready. A powerful compressive force at the glenohumeral joint is thus present. The position of the arm as the player engages his opponent causes a posteriorly directed shearing force to be delivered to the athlete s shoulder (Fig. 5). We hypothesize that, because of the high compressive force at the glenohumeral joint, the shear stress is transmitted to the posterior glenoid and labrum, but the humeral head does not skip over the labrum. This could lead to injury to the posterior glenoid articular surface and labrum without overt evidence of injury to the posterior capsule. This lack of capsular injury is supported by symmetric posterior translation on examination under anesthesia. It has been mentioned to us that these athletes may have subtle posterior instability in both shoulders, as

5 Vol. 26, No. 6, 1998 Posterior Labral Injury in Contact Athletes 757 Figure 5. Proposed mechanism of injury. Compressive forces at the glenohumeral joint are present as the offensive lineman prepares to meet an opponent with shoulder musculature ready. A posteriorly directed force at impact leads to a resultant vector of shear force to the posterior glenoid and labrum. they would be subjected to repeated posterior stresses bilaterally. We cannot disprove this as posterior translation varies from patient to patient. However, each of these patients was asymptomatic in the contralateral shoulder at the time of surgery, and surgical reattachment of the labrum without addressing the capsule led to alleviation of symptoms in the injured shoulder. An analogy to our hypothesized mechanism of injury is the chock block around an airplane tire. The plane exerts a high compressive force toward the pavement: as it rolls forward it moves the chock block out of the way (Fig. 6). Our proposed mechanism of posterior labral detachment is somewhat similar to those mentioned in previous discussions of labral injury. Andrews et al. 2 have stated that both anterior and posterior labral injury can occur from forceful entrapment of the labrum between the humeral Figure 6. Chock blocks around airplane tire are analogous to action of the glenoid labrum. The plane exerts a compressive force to the pavement. If the plane rolls forward, the chock block is moved out of the way. Figure 7. Posterior glenoid chondral injury in an offensive lineman undergoing arthroscopy for distal clavicle osteolysis. The posterior labrum is frayed but has not become detached. head and the glenoid rim...[which] may result in a shear injury to the interposed labral tissue. Snyder et al. 16 believe that the SLAP lesion is the result of a fall on the outstretched abducted arm, which entraps the superior labrum under the humeral head. The resultant shearing and compressive force leads to tearing of the labrum. This proposed mechanism is similar to ours except for the position of the arm when the force occurs. The two patients in our series who could pinpoint the advent of their symptoms reported mechanisms similar to those we have proposed. Each had his shoulder in a position of flexion near 90 and the elbow in full extension when he suffered a posteriorly directed blow that was transferred up the arm to the shoulder. While the remainder of the athletes in this series could not recall a specific event inciting their symptoms, all were football linemen and would have had occasion to be subjected to the mechanism we have described. All of these athletes also attempted to bench press regularly as part of a conditioning program. Bench pressing results in additional posteriorly directed forces at the glenohumeral joint. In a shoulder that has sustained injury to the posterior labrum, this could potentially result in worsening of the lesion. Certainly, in our patients it exacerbated shoulder symptoms. However, we do not believe that bench pressing produced the posterior labral detachment as we have not seen this lesion in bench-pressing athletes not involved in sports that allow exposure to posteriorly directed forces at the shoulder. In addition to the nine athletes in this reported series, we have seen five other contact athletes with irregularity in the posterior labrum noted at the time of shoulder arthroscopy for other lesions (predominantly distal clavicle osteolysis). These irregularities consisted of fraying or

6 758 Mair et al. American Journal of Sports Medicine small tears, or both, in the substance of the labrum without evidence of labral detachment. Four of these five athletes also had injury to the posterior glenoid chondral surface (Fig. 7). These patients did not appear to have symptoms related to the observed posterior labral irregularity. We believe that injury or wear to the posterior labrum and chondral surface is a type of occupational hazard for contact athletes (particularly offensive linemen), analogous to sport-specific repetitive trauma lesions seen in other endeavors. The posterior aspect of the shoulder is subjected to repeated shear stresses with activities such as blocking an onrushing defensive lineman. This is manifested by the fraying of the labrum seen in all the athletes we have described in this series and by the posterior glenoid chondral injury in 9 of 14 total athletes observed. It may be that it is not until a threshold is reached and the labrum becomes detached that this repetitive shearing force produces an injury that becomes symptomatic. Posterior labral detachment is likely a part of a spectrum of injury to the posterior labrum in an athlete exposed to repeated posterior shear forces. It is possible that posterior glenohumeral instability could be the end of this spectrum, but we did not see this develop in our relatively young group of patients. In general, patients with posterior labral detachment are free of symptoms during activities of daily living and require no treatment if they retire from their sport. However, an offensive lineman who has pain while blocking and bench pressing is unable to function effectively if he wishes to continue to participate in sports. Repair of the posterior labral detachment has been effective in allowing these athletes to return to sports. CONCLUSIONS Posterior labral detachment, as observed in the practice of the senior author, is specific to contact sports in which players engage their opponent with arms held out in front of the body. The diagnosis is difficult because clinical symptoms are not specific. Posterior joint line tenderness may suggest this lesion. Imaging by MRI or CT arthrography can be helpful to make the diagnosis, but in some cases the posterior labral detachment was missed by imaging studies and in all cases it was relatively subtle. In a contact athlete with vague symptoms of shoulder pain that is manifest during contact sports and bench pressing, the diagnosis of posterior labral detachment should be considered. Consistently good results have been obtained with stabilization of these lesions with a bioabsorbable tack. ACKNOWLEDGMENT The authors thank Ms. Marsha Dohrmann for her illustration (Fig. 5). REFERENCES 1. 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