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Management of acute acromioclavicular joint dislocation with a double-button fixation system
Injury, Int. J. Care Injured 44 (2013) 288–292
Contents lists available at SciVerse ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Management of acute acromioclavicular joint dislocation with a double-button fixation system Alexander Beris *, Marios Lykissas, Ioannis Kostas-Agnantis, Marios Vekris, Gregory Mitsionis, Anastasios Korompilias Orthopaedic Department, University Hospital of Ioannina, Greece
A R T I C L E I N F O
A B S T R A C T
Keywords: Acromioclavicular joint Coracoclavicular ligament complex Conoid ligament Trapezoid ligament TightRope system
Introduction: Numerous static and dynamic techniques have been described for the management of acute acromioclavicular (AC) joint dislocation. To date, no standard technique has been established and several complications have been described for each of these techniques. The purpose of the present study was to evaluate the functional and radiographic outcomes of acute AC joint reconstruction after a miniopen technique using the double-button fixation system. Patients and methods: Twelve patients with acute AC joint dislocation treated with the double-button fixation system by one surgeon were retrospectively reviewed. Functional assessment was performed by an independent reviewer using the DASH, Constant and the VAS scores. The coracoclavicular (CC) distance of the affected shoulder was assessed on a standard radiograph and compared with the contralateral normal one. Results: Eight patients were operated on for grade III AC joint dislocation and 4 for grade IV. The mean age of the patients at the time of surgery was 27.5 years. The mean follow-up was 18.25 months (range: 12–30 months). At the most recent follow-up, the mean Constant score was 94.8 (range: 84–100) showing a significant increase compared with the mean pre-operative value of 34.4 (range: 25–52) (p < 0.001). The mean DASH score was significantly decreased from 19.6 (range: 14–28) preoperatively to 0.25 (range: 0–3) at the last follow-up (p < 0.001). The mean VAS score showed a significant decrease from 5.75 (range: 4–7) to 0.2 (range: 0–2) (p < 0.001). The mean CC distance on the operated shoulder was found to have no significant difference from the CC distance on the contralateral normal side (10.5 vs. 10 mm) (p > 0.05). There was no evidence of AC joint osteoarthrosis, CC calcification or osteolysis of the distal clavicle or the coracoid process. Conclusions: The proposed mini-open technique provides adequate exposure of the base of the coracoid with minimal damage to the soft tissues surrounding the CC ligaments while ensures an excellent cosmetic result. We recommend this fast and relatively simple technique for all type IV injuries and for type III injuries in heavy manual workers and high-demand upper extremities athletes. ß 2013 Elsevier Ltd. All rights reserved.
Introduction Acromioclavicular (AC) joint dislocation is one of the most common injuries of the upper extremity and usually involves young athletes.1 It is considered the most common shoulder injury in contact sports players with an incidence of 41% among the collegiate football players and 40% of National Football League quarterbacks in the United States.2,3 Conservative management is indicated for Rockwood types I and II.4 In contrast, surgical intervention is reserved for more severe types IV–VI with involvement of the coracoclavicular (CC) ligaments resulting in
* Corresponding author at: 15 Charilaou Trikoupi Street, 45332 Ioannina, Greece. Tel.: +30 26510 37788/99684; fax: +30 26510 97018. E-mail address: [email protected] (A. Beris). 0020–1383/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.injury.2013.01.002
a relative dislocation of the clavicle. Restoration of the normal anatomy of the AC joint corrects the obvious deformity and prevents a potentially unsatisfactory outcome that may include persistent discomfort and secondary AC joint degenerative changes.5,6 The management of Rockwood type III AC joint dislocation remains controversial with most authors recommending an operative approach in case of manual workers.7 When surgery is indicated, restoration of the AC joint congruency and the anatomy of the CC ligament complex are prerequisites for the development of rigid scar tissue healing.8 Numerous static and dynamic techniques have been described for the management of acute AC joint dislocation, including AC joint pinning, CC loop cerclage, hook plates, CC screws, CC ligament repair, coracoid transfer, distal clavicle excision, ligament or muscle transfer.9–15 To date, no standard technique has been established and several complications have been described for each of these techniques.
A. Beris et al. / Injury, Int. J. Care Injured 44 (2013) 288–292
289
Recently, anatomic reconstruction techniques have been adopted in an effort to provide physiologic conditions that restore the strength and stiffness of the normal AC joint complex. Anatomic reconstruction using the TightRope device (Arthrex, Naples, FL) has been proven an effective technique for the management of acute AC joint dislocations in both biomechanical and clinical studies.8,16–20 The purpose of the present study was to evaluate the functional and radiographic outcomes of acute AC joint reconstruction after a mini-open technique using the doublebutton fixation system. Patients and methods Study population After obtaining Institutional Review Board approval, the medical records and shoulder radiographs of patients with the diagnosis of traumatic AC joint dislocation who had undergone surgical management with a double-button fixation system between January 2008 and July 2011 were retrospectively reviewed. Diagnosis was suspected initially on clinical examination, and confirmed radiographically. The classification system proposed by Rockwood4 was used to assess the severity of the deformity based on anteroposterior, axillary, and Zanca views21 of both shoulders. Inclusion criteria were: (1) acute AC joint dislocation, (2) no previous shoulder complains or surgery, (3) no associated injuries, and (4) follow-up time of at least 12 months. The diagnosis of acute AC joint dislocation was established when both clinical and radiographic findings of the condition were identified within 3 weeks from injury.22 Clinical and radiographic assessment Clinical data was collected on age, gender, hand dominance, mechanism of injury, time from injury to surgery, range of motion of the affected shoulder, time from surgery to return to work, and length of follow-up. Functional assessment was performed by an independent reviewer using the Disability of Arm, Shoulder and Hand (DASH) scoring system,23 Constant score,24 and Visual Analogue Scale (VAS) score. The vertical distance between the anterior–inferior border of the clavicle and the superior border of the coracoid process (CC distance) was calculated on standard anteroposterior views of the AC arch pre-operatively, and at the time of the last follow-up on both shoulders (Fig. 1). The affected AC joint was also evaluated for any signs of postoperative degenerative arthritis. Surgical technique and rehabilitation The patient was placed in the beach chair and examination under anesthesia was performed to assess the stability of the shoulder and the reducibility of the AC joint. The upper extremity was prepped and draped in the usual sterile fashion and appropriate antibiotic prophylaxis was administered before the incision. A mini-open technique was used in all cases. A vertical 1cm skin incision was made over the top of the clavicle, 2.5 cm medial to the AC joint. A second 2.5-cm incision was made over the coracoid process followed by meticulous dissection down to the base of the coracoid process. Under C-arm visualization, the bony tunnels to the clavicle and coracoid process were drilled in separate steps. First, a 2.4-mm guide pin was inserted in a cephalad to caudal direction at the base of the coracoid process. The guide pin was aimed at the center of the coracoid process and close to the neck where the coracoid gives off the scapula. This was overdrilled with a 4.0-mm cannulated drill taking care not to advance the guide pin while drilling. Then, the bony tunnel to the clavicle was
Fig. 1. Radiograph illustrating the coracoclavicular distance as the vertical distance between the anterior–inferior border of the clavicle and the superior border of the coracoid process.
drilled in a similar fashion at the center of the distance between anterior and posterior border of the clavicle. The guide wire and the drill were removed and the TightRope device (Arthrex, Naples, FL) was inserted first through the clavicle and then through the coracoid tunnel using the Button Inserter. The oblong button was flipped and seated underneath the coracoid process by pulling one of the two traction sutures. Finally, the AC joint was reduced into anatomical position under fluoroscopic visualization, the round button was advanced to the cephalad surface of the clavicle and the ends were secured by a minimum of 5 alternating knots while an assistant held the reduction. Postoperative protocol included shoulder immobilization in a sling for 4 weeks followed by progressive range of motion and strengthening exercises. Daily activities are resumed after 3 months and return to sports activities was allowed after 6 months. Statistical analysis Statistical comparison of functional scores and radiographic measurements was performed using the paired t-test. All tests were calculated with use of the SPSS, version 16.0 (SPSS Inc., Chicago, IL) statistic package for personal computers. In all instances, pvalues < 0.05 were regarded as statistically significant. Results Twelve patients who met the inclusion criteria were followedup for a mean of 18.25 months (range: 12–30 months) (Table 1). The mean age of the patients at the time of surgery was 27.5 years (range: 19–39 years). There were 9 male and 3 female patients. The involved side was the right shoulder in 8 cases and the left in 4. The dominant shoulder was involved in 10 patients. Eight patients were operated on for grade III AC joint dislocation and 4 for grade IV. All patients with grade III AC joint dislocation were men and manual laborers (6 patients) or high-demand upper extremities athletes (2 patients). Initial trauma involved motor vehicle accidents in 6 cases (50%), sport injuries in 3 (25%), and falls in 3 cases (25%). The mean time from injury to surgical management was 5 days (range: 2–14). All patients were operated by the same surgeon. Functional results At the most recent follow-up, the mean Constant score was 94.8 (range: 84–100) showing a significant increase compared with the mean pre-operative value of 34.4 (range: 25–52) (p < 0.001). All
A. Beris et al. / Injury, Int. J. Care Injured 44 (2013) 288–292
8 8 12 10 18 12 14 13 11 12 10 8
Return to work (weeks)
9.2 10.3 11 9 10.2 12.2 10.3 10 8.3 10.8 10.4 9.2 9.6 11.8 12.4 9 12.1 12.8 11.4 10.1 8.8 12 10.4 9.7
Radiographic results
Fall Sports MVA Fall MVA Sports MVA MVA Fall MVA Sports MVA
2 3 2 6 14 3 4 4 11 2 7 3
12 18 20 14 24 12 18 15 30 18 14 24
32 52 33 44 28 38 31 25 39 30 28 33
98 100 100 100 90 99 89 94 98 84 84 100
6 5 5 7 5 5 7 7 4 4 7 7
0 0 0 0 0 0 0 0 0 2 0 0
21 18 15 23 16 14 22 26 18 14 20 28
0 0 0 0 0 0 0 0 0 3 0 0
At the last follow-up, radiological assessment revealed complete reduction of the AC joint. The mean CC distance on the operated shoulder did not show a significant difference from the mean CC distance on the contralateral normal side (10.5 vs. 10 mm) (p > 0.05). In all cases both metallic buttons remained in the correct position (Fig. 2). There was no evidence of AC joint
MVA: motor vehicle accident. * According to Rockwood classification. ** CC distance: coracoclavicular distance.
III IV III III III III IV IV III III III IV Right Right Left Right Right Right Left Right Left Right Right Left M M M M M M F F M M M F 1 2 3 4 5 6 7 8 9 10 11 12
29 21 31 26 22 19 24 29 34 23 33 39
Yes Yes Yes Yes No Yes Yes Yes No Yes Yes Yes
Pre-op. Post-op. Pre-op.
Post-op.
Pre-op.
Post-op.
Affected side
Contralateral side
Excellent Excellent Excellent Excellent Good Excellent Excellent Excellent Excellent Good Good Excellent
Subjective result CC Distance** (mm) DASH score VAS score Constant score Follow-up (months) Time interval from injury to surgery (days) Mechanism Grading of injury* Dominant extremity Side Age Gender No.
Table 1 Patients’ details.
parameters of the Constant score, including pain, daily life activity, range of motion, and strength were significantly higher at the last follow-up. The mean DASH score was significantly decreased from 19.6 (range: 14–28) preoperatively to 0.25 (range: 0–3) at the last follow-up (p < 0.001). Similarly, the mean VAS score showed a significant decrease from 5.75 (range: 4–7) to 0.2 (range: 0–2) (p < 0.001). Nine patients (75%) were very satisfied with the postoperative result while 3 (25%) were satisfied. All patients reported that would undergo the same procedure if sustain a similar lesion to the contralateral shoulder. All patients resumed their former work with a mean time to resumption of 10 weeks (range: 9–11 weeks). There were no complications. None of the patients required additional procedures for recurrent AC joint dislocation.
None None None None None None None None None Shoulder pain None None
Complications
290
Fig. 2. (A) Preoperative radiograph of the right shoulder of a 26-year-old male patient who sustained a type III acromioclavicular joint dislocation after fall. His coracoclavicular distance measured 23 mm and his Constant score 44. (B) Radiograph of the right, dominant shoulder at the final follow-up 14 months after surgery demonstrating anatomical reduction of the acromioclavicular joint with coracoclavicular distance measured 9 mm on both shoulders. His Constant score was 100.
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osteoarthrosis, CC calcification, or osteolysis of the distal clavicle or the coracoid process. Discussion The high complication rate associated with the great variety of methods reported in the literature for the management of acute AC joint dislocation reflects the ineffectiveness to restore the normal physiology of the AC joint complex. Temporary fixation with pins or cerclage is no longer recommended because of the increase incidence of degenerative AC joint changes, bony erosion, pin breakage and intrathoracic migration.25,26 A second procedure for implant removal is also needed. Coracoid process transfer provides a dynamic stabilization with high rate of complications including injury to the musculocutaneous nerve.27 The concept of the popular coracoacromial ligament transfer or Weaver–Dunn procedure with its various modifications is that the transfer will allow the CC ligaments to heal and withstand forces equivalent to tensile strength. However, it has been proven that the coracoacromial ligament is biomechanically inferior in comparison to tendon graft reconstruction and may lead to subluxation or dislocation of the AC joint in 30% of the cases in the chronic setting.28 In order to overcome these complications, anatomic reconstruction of the main restraints of the AC joint has been proposed. It has been shown that CC ligaments contribute two-thirds of the restraining force to vertical translation, whereas the AC ligaments and capsule limit horizontal displacement.29–32 More recently, biomechanical studies support the unique role of each ligament of the CC ligament complex with the conoid ligament being the prime suspensor in anterior and superior translation of the clavicle, especially under high loads, and the less important role of the trapezoid ligament.33,34 By placing a prosthetic device, such as the TightRope, in place of CC ligaments a single structure is used to reduce distal clavicle. No auto- or allograft and no implant removal are required. Two titanium buttons, one round clavicular and one long coracoidal, are used to allow homogenous distribution of loads on bone surfaces and thus avoid the sawing effect of the sutures associated with failure in other anchor and suture techniques.35,36 A continues loop of No. 5 FiberWire suture (Arthrex, Naples, FL) organized as a pulley is used to connect the two buttons placed on the top of the clavicle and under the coracoid. Imhoff and Chernchujit37 showed that No. 5 FiberWire failed at 485 N whereas the native CC ligament complex failed at 589 N. Thus, the tensile strength of two strands of No. 5 FiberWire is higher than the tensile strength of intact CC ligament complex. Although there is no longterm study evaluating the effectiveness of this technique, Walz et al.16 based on second-look arthroscopy findings of biologic reaction around the TightRope device after 6 weeks and 3 months hypothesized that long-term stability may be achieved by scarring the ligament stumps with soft tissue complexes. First generation of double-button fixation system has been associated with unacceptable rate of loss of reduction because of the small size, round proximal button that resulted in erosion of the superior surface of the clavicle.19,38,39 This is also a characteristic finding in synthetic ligament reconstruction technique that uses a polyester ligament threaded under the coracoid and fixed to the clavicle by means of 2 polyethylene plugs.40 Newer devices consist of a large clavicle button that prevents bone erosion. In our series, a second generation TightRope with a big proximal titanium button was used in all cases. After a mean follow-up of 18.25 months, we did not record any bone erosion or loss of reduction secondary to implant failure. Accurate placement of the device is also of paramount importance. The coracoid process should be drilled at its center on the coronal plane and close to the neck were the coracoid give off the scapula. This area
291
has greater resistance compared with the anterior part of the coracoid which is important in order to avoid erosion and cephalad migration of the button. In addition, the clavicle tunnel should be drilled halfway between the anterior and posterior border of the clavicle. Recently, double-button fixation system has been used for anatomic reconstruction of the CC complex by placing 2 TightRope devices through individual tunnels in the clavicle.16 Based on the cadaver study of Rios et al.41 reconstruction of the trapezoid and conoid ligaments was performed by placing two independent tunnels medial from the lateral clavicular edge in a distance equal with 17% and 30% of the total clavicle length, respectively. The study was performed in 40 fresh-frozen cadaveric shoulders and showed that the mean maximum static load until failure in native CC complex for vertical force measured 598 N and stiffness 99 N/ mm, and for anterior static force 338 N and stiffness 140 N/mm. The mean maximum static load until failure in double TightRope reconstruction for vertical force measured 982 N and stiffness 80 N/mm, and for anterior static force 627 N and stiffness 78 N/ mm. The authors concluded that this method withstand much higher forces than the native ligament complex with only the bicortical CC screw technique showing more strength. The lower stiffness of the reconstructed complex was attributed to the quadrupled FiberWire. These findings were in accordance with La¨dermann et al.8 biomechanical study in which the Twin Tail TightRope system (Arthrex, Naples, FL) was compared with AC and CC cerclages and locking compression superior and anterior clavicle plate. The Twin Tail TightRope and the AC and CC cerclage systems demonstrated similar biomechanical performances with the former showing higher superoinferior and anteroposterior stiffness. The authors supported that the increased stiffness and the lower motion in the superior direction noted with the Twin Tail TightRope system may have prevented the progressive relaxation noticed with the AC and CC cerclage system. The main pattern of failure associated with the Twin Tail TightRope system was the complete cutout of the coracoid button. Acute AC joint reconstruction with the double-button fixation system can be performed through an open or an arthroscopic approach. The theoretical advantages of the arthroscopic approach are the better cosmetic results, and the ability to address any associated conditions to AC joint dislocation, such as associated glenohumeral pathology.19 The excellent functional outcomes that have been reported after arthroscopic AC joint reconstruction have made some authors to recommend this procedure in any acute AC joint reconstruction and reserve open approach for subacute and chronic cases.18 In the present study, we describe a mini-open approach that can effectively restore the AC joint and CC ligament complex anatomy. The procedure is fast and relatively simple. Through 2 small skin incisions of 1 and 2.5 cm made over the top of the clavicle and the coracoid process, respectively, both bone tunnels can be drilled with minimal damage to the soft tissues surrounding the CC ligaments while allowing adequate visualization of the coracoid for accurate tunnel placement. Limitations of our study include its retrospective design, the small number of patients, and the relative short-term follow-up. Because of the favorable functional and radiographic results we continue to use the same technique in all our patients with acute AC joint dislocation requiring surgical management. We also continue to follow-up the already operated patients in order to evaluate whether the promising outcomes will be maintained on a mid- and long-term basis. Conclusions Treatment of acute type III and IV AC joint dislocation with TightRope system gave satisfactory functional and radiographic
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results. In the light of these findings we recommend this technique for all type IV injuries and for type III injuries in heavy manual workers and high-demand upper extremities athletes, such as throwers. Accurate placement of the device at the centre of the base of the coracoid process is of paramount importance. The proposed mini-open technique provides adequate exposure of the base of the coracoid with minimal damage to the soft tissues surrounding the CC ligaments while ensures an excellent cosmetic result. Conflict of interest statement There are no financial and personal relationships with other people or organisations that could inappropriately influence (bias) this work. References 1. Kocher MS, Dupre MM, Feagin Jr JA. Shoulder injuries from alpine skiing and snowboarding: aetiology, treatment, and prevention. Sports Medicine 1998; 25:201–11. 2. Kaplan LD, Flanigan DC, Norwig J, Jost P, Bradley J. Prevalence and variance of shoulder injuries in elite collegiate football players. American Journal of Sports Medicine 2005;33:1142–6. 3. Kelly BT, Barnes RP, Powell JW, Warren RF. Shoulder injuries to quarterbacks in the national football league. American Journal of Sports Medicine 2004;32:328– 31. 4. Rockwood Jr CA. Injuries to the acromioclavicular joint. In: Rockwood Jr CA, Green DP, editors. Fractures in Adults. 2nd ed. Philadelphia, PA: JB Lippincott; 1984. p. 860. 5. Rawes ML, Dias JJ. Long-term results of conservative treatment for acromioclavicular dislocation. Journal of Bone and Joint Surgery British Volume 1996;78:410–2. 6. Calvo E, Lopez-Franco M, Arribas IM. Clinical and radiologic outcomes of surgical and conservative treatment of type III acromioclavicular joint injury. Journal of Shoulder and Elbow Surgery 2006;15:300–5. 7. Nuber GW, Bowen MK. Acromioclavicular joint injuries and distal clavicle fractures. Journal of the American Academy of Orthopaedic Surgeons 1997; 5:11–8. 8. La¨dermann A, Gueorguiev B, Stimec B, Fasel J, Rothstock S, Hoffmeyer P. Acromioclavicular joint reconstruction: a comparative biomechanical study of three techniques. Journal of Shoulder and Elbow Surgery 2012, in press. 9. De Tullio V, Orsi R, Celenza M. Surgical treatment of Allman type III acromioclavicular dislocation. A long-term follow-up study. Acta Orthopaedica Belgica 1994;60:300–2. 10. Sim E, Schwarz N, Hocker K, Berzlanovich A. Repair of complete acromioclavicular separations using the acromioclavicular-hook plate. Clinical Orthopaedics and Related Research 1995;314:134–42. 11. Sundaram N, Patel DV, Porter DS. Stabilization of acute acromioclavicular dislocation by a modified Bosworth technique: a long-term follow-up study. Injury 1992;23:189–93. 12. Tienen TG, Oyen JF, Eggen PJ. A modified technique of reconstruction for complete acromioclavicular dislocation: a prospective study. American Journal of Sports Medicine 2003;31:655–9. 13. Mazzocca AD, Santangelo SA, Johnson ST, Rios CG, Dumonski ML, Arciero RA. A biomechanical evaluation of an anatomical CC ligament reconstruction. American Journal of Sports Medicine 2006;34:236–46. 14. Greiner S, Braunsdorf J, Perka C, Herrmann S, Scheffler S. Mid to long-term results of open acromioclavicular-joint reconstruction using polydioxansulfate cerclage augmentation. Archives of Orthopaedic and Trauma Surgery 2009; 129:735–40. 15. Heitemeyer U, Hierholzer G, Schneppendahl G, Haines J. The operative treatment of fresh ruptures of the acromioclavicular joint (Tossy III). Archives of Orthopaedic and Trauma Surgery 1986;104:371–3. 16. Walz L, Salzmann GM, Fabbro T, Eichhorn S, Imhoff AB. The anatomic reconstruction of acromioclavicular joint dislocations using 2 TightRope devices: a biomechanical study. American Journal of Sports Medicine 2008;36:2398–406.
17. Basyoni Y, El-Ganainy AE, Aboul-Saad M. Acromioclavicular joint reconstruction using anchor sutures: surgical technique and preliminary results. Acta Orthopaedica Belgica 2010;76:307–11. 18. Defoort S, Verborgt O. Functional and radiological outcome after arthroscopic and open acromioclavicular stabilization using a double-button fixation system. Acta Orthopaedica Belgica 2010;76:585–91. 19. Murena L, Vulcano E, Ratti C, Cecconello L, Rolla PR, Surace MF. Arthroscopic treatment of acute acromioclavicular joint dislocation with double flip button. Knee Surgery Sports Traumatology Arthroscopy 2009;17:1511–5. 20. Salzmann GM, Walz L, Schoettle PB, Imhoff AB. Arthroscopic anatomical reconstruction of the acromioclavicular joint. Acta Orthopaedica Belgica 2008;74:397–400. 21. Zanca P. Shoulder pain: involvement of the acromio-clavicular joint (analysis of 1,000 cases). American Journal of Roentgenology Radium Therapy and Nuclear Medicine 1971;12:93–506. 22. Glorion B, Delplace J. Surgical treatment of acromio-clavicular dislocations by the Dewar–Barrington technic, critical study and results apropos of 41 cases. Revue de Chirurgie Orthopedique et Reparatrice de l Appareil Moteur 1973;59:667– 79. 23. De Smet L. the DASH questionnaire and score in the evaluation of hand and wrist disorders. Acta Orthopaedica Belgica 2008;74:575–81. 24. Constant CR, Murley AH. A clinical method of functional assessment of the shoulder. Clinical Orthopaedics and Related Research 1987;214:42–8. 25. Mazet RJ. Migration of a Kirschner-wire from the shoulder region into the lung: report of two cases. Journal of Bone and Joint Surgery 1943;25:477–83. 26. Norell H, Liewellyn RC. Migration of threaded Steinmann pin from an acromioclavicular joint into the spinal canal: a case report. Journal of Bone and Joint Surgery 1965;47:1024–6. 27. Ferris BD, Bhamra M, Paton DF. Coracoid process transfer for acromioclavicular dislocations. A report of 20 cases. Clinical Orthopaedics and Related Research 1989;242:184–94. 28. Weaver JK, Dunn HK. Treatment of acromioclavicular injuries, especially complete acromioclavicular separation. Journal of Bone and Joint Surgery 1972;54:1187–94. 29. Fukuda K, Craig EV, An KN, Cofield RH, Chao EY. Biomechanical study of the ligamentous system of the acromioclavicular joint. Journal of Bone and Joint Surgery 1986;68:434–40. 30. Grutter PW, Petersen SA. Anatomical acromioclavicular ligament reconstruction: a biomechanical comparison of reconstructive techniques of the acromioclavicular joint. American Journal of Sports Medicine 2005;33:1723–8. 31. Harris RI, Wallace AL, Harper GD. Structural properties of the intact and the reconstructed CC ligament complex. American Journal of Sports Medicine 2000;28:103–8. 32. Breslow MJ, Jazrawi LM, Bernstein AD, Kummer FJ, Rokito AS. Treatment of acromioclavicular joint separation: suture or suture anchors? Journal of Shoulder and Elbow Surgery 2002;11:225–9. 33. Costic RS, Labriola JE, Rodosky MW, Debski RE. Biomechanical rationale for development of anatomical reconstructions of CC ligaments after complete acromioclavicular joint dislocations. American Journal of Sports Medicine 2004;32:1929–36. 34. Harris RI, Vu DH, Sonnabend DH, Goldberg JA, Walsh WR. Anatomic variance of the CC ligaments. Journal of Shoulder and Elbow Surgery 2001;10:585–8. 35. Somers JF, Van der Linden D. Arthroscopic fixation of type III acromioclavicular dislocations. Acta Orthopaedica Belgica 2007;73:566–70. 36. Wellmann M, Zantop T, Weimann A, Raschke MJ, Petersen W. Biomechanical evaluation of minimally invasive repairs for complete acromioclavicular joint dislocation. American Journal of Sports Medicine 2007;35:955–61. 37. Imhoff AB, Chernchujit B. Arthroscopic anatomic stabilization of acromioclavicular joint dislocation. Operative Techniques in Sports Medicine 2004;12:43–8. 38. Bishop JY, Kaeding C. Treatment of the acute traumatic acromioclavicular separation. Sports Medicine and Arthroscopy Review 2006;14:237–44. 39. Hosseini H, Friedmann S, Tro¨ger M, Lobenhoffer P, Agneskirchner JD. Arthroscopic reconstruction of chronic AC joint dislocations by transposition of the coracoacromial ligament augmented by the Tight Rope device: a technical note. Knee Surgery Sports Traumatology Arthroscopy 2009;17:92–7. 40. Mares O, Luneau S, Staquet V, Beltrand E, Bousquet PJ, Maynou C. Acute grade III and IV acromioclavicular dislocations: outcomes and pitfalls of reconstruction procedures using a synthetic ligament. Orthopaedics & Traumatology Surgery & Research 2010;96:721–6. 41. Rios CG, Arciero RA, Mazzocca AD. Anatomy of the clavicle and coracoid process for reconstruction of the CC ligaments. American Journal of Sports Medicine 2007;35:811–7.
Contents lists available at SciVerse ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Management of acute acromioclavicular joint dislocation with a double-button fixation system Alexander Beris *, Marios Lykissas, Ioannis Kostas-Agnantis, Marios Vekris, Gregory Mitsionis, Anastasios Korompilias Orthopaedic Department, University Hospital of Ioannina, Greece
A R T I C L E I N F O
A B S T R A C T
Keywords: Acromioclavicular joint Coracoclavicular ligament complex Conoid ligament Trapezoid ligament TightRope system
Introduction: Numerous static and dynamic techniques have been described for the management of acute acromioclavicular (AC) joint dislocation. To date, no standard technique has been established and several complications have been described for each of these techniques. The purpose of the present study was to evaluate the functional and radiographic outcomes of acute AC joint reconstruction after a miniopen technique using the double-button fixation system. Patients and methods: Twelve patients with acute AC joint dislocation treated with the double-button fixation system by one surgeon were retrospectively reviewed. Functional assessment was performed by an independent reviewer using the DASH, Constant and the VAS scores. The coracoclavicular (CC) distance of the affected shoulder was assessed on a standard radiograph and compared with the contralateral normal one. Results: Eight patients were operated on for grade III AC joint dislocation and 4 for grade IV. The mean age of the patients at the time of surgery was 27.5 years. The mean follow-up was 18.25 months (range: 12–30 months). At the most recent follow-up, the mean Constant score was 94.8 (range: 84–100) showing a significant increase compared with the mean pre-operative value of 34.4 (range: 25–52) (p < 0.001). The mean DASH score was significantly decreased from 19.6 (range: 14–28) preoperatively to 0.25 (range: 0–3) at the last follow-up (p < 0.001). The mean VAS score showed a significant decrease from 5.75 (range: 4–7) to 0.2 (range: 0–2) (p < 0.001). The mean CC distance on the operated shoulder was found to have no significant difference from the CC distance on the contralateral normal side (10.5 vs. 10 mm) (p > 0.05). There was no evidence of AC joint osteoarthrosis, CC calcification or osteolysis of the distal clavicle or the coracoid process. Conclusions: The proposed mini-open technique provides adequate exposure of the base of the coracoid with minimal damage to the soft tissues surrounding the CC ligaments while ensures an excellent cosmetic result. We recommend this fast and relatively simple technique for all type IV injuries and for type III injuries in heavy manual workers and high-demand upper extremities athletes. ß 2013 Elsevier Ltd. All rights reserved.
Introduction Acromioclavicular (AC) joint dislocation is one of the most common injuries of the upper extremity and usually involves young athletes.1 It is considered the most common shoulder injury in contact sports players with an incidence of 41% among the collegiate football players and 40% of National Football League quarterbacks in the United States.2,3 Conservative management is indicated for Rockwood types I and II.4 In contrast, surgical intervention is reserved for more severe types IV–VI with involvement of the coracoclavicular (CC) ligaments resulting in
* Corresponding author at: 15 Charilaou Trikoupi Street, 45332 Ioannina, Greece. Tel.: +30 26510 37788/99684; fax: +30 26510 97018. E-mail address: [email protected] (A. Beris). 0020–1383/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.injury.2013.01.002
a relative dislocation of the clavicle. Restoration of the normal anatomy of the AC joint corrects the obvious deformity and prevents a potentially unsatisfactory outcome that may include persistent discomfort and secondary AC joint degenerative changes.5,6 The management of Rockwood type III AC joint dislocation remains controversial with most authors recommending an operative approach in case of manual workers.7 When surgery is indicated, restoration of the AC joint congruency and the anatomy of the CC ligament complex are prerequisites for the development of rigid scar tissue healing.8 Numerous static and dynamic techniques have been described for the management of acute AC joint dislocation, including AC joint pinning, CC loop cerclage, hook plates, CC screws, CC ligament repair, coracoid transfer, distal clavicle excision, ligament or muscle transfer.9–15 To date, no standard technique has been established and several complications have been described for each of these techniques.
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Recently, anatomic reconstruction techniques have been adopted in an effort to provide physiologic conditions that restore the strength and stiffness of the normal AC joint complex. Anatomic reconstruction using the TightRope device (Arthrex, Naples, FL) has been proven an effective technique for the management of acute AC joint dislocations in both biomechanical and clinical studies.8,16–20 The purpose of the present study was to evaluate the functional and radiographic outcomes of acute AC joint reconstruction after a mini-open technique using the doublebutton fixation system. Patients and methods Study population After obtaining Institutional Review Board approval, the medical records and shoulder radiographs of patients with the diagnosis of traumatic AC joint dislocation who had undergone surgical management with a double-button fixation system between January 2008 and July 2011 were retrospectively reviewed. Diagnosis was suspected initially on clinical examination, and confirmed radiographically. The classification system proposed by Rockwood4 was used to assess the severity of the deformity based on anteroposterior, axillary, and Zanca views21 of both shoulders. Inclusion criteria were: (1) acute AC joint dislocation, (2) no previous shoulder complains or surgery, (3) no associated injuries, and (4) follow-up time of at least 12 months. The diagnosis of acute AC joint dislocation was established when both clinical and radiographic findings of the condition were identified within 3 weeks from injury.22 Clinical and radiographic assessment Clinical data was collected on age, gender, hand dominance, mechanism of injury, time from injury to surgery, range of motion of the affected shoulder, time from surgery to return to work, and length of follow-up. Functional assessment was performed by an independent reviewer using the Disability of Arm, Shoulder and Hand (DASH) scoring system,23 Constant score,24 and Visual Analogue Scale (VAS) score. The vertical distance between the anterior–inferior border of the clavicle and the superior border of the coracoid process (CC distance) was calculated on standard anteroposterior views of the AC arch pre-operatively, and at the time of the last follow-up on both shoulders (Fig. 1). The affected AC joint was also evaluated for any signs of postoperative degenerative arthritis. Surgical technique and rehabilitation The patient was placed in the beach chair and examination under anesthesia was performed to assess the stability of the shoulder and the reducibility of the AC joint. The upper extremity was prepped and draped in the usual sterile fashion and appropriate antibiotic prophylaxis was administered before the incision. A mini-open technique was used in all cases. A vertical 1cm skin incision was made over the top of the clavicle, 2.5 cm medial to the AC joint. A second 2.5-cm incision was made over the coracoid process followed by meticulous dissection down to the base of the coracoid process. Under C-arm visualization, the bony tunnels to the clavicle and coracoid process were drilled in separate steps. First, a 2.4-mm guide pin was inserted in a cephalad to caudal direction at the base of the coracoid process. The guide pin was aimed at the center of the coracoid process and close to the neck where the coracoid gives off the scapula. This was overdrilled with a 4.0-mm cannulated drill taking care not to advance the guide pin while drilling. Then, the bony tunnel to the clavicle was
Fig. 1. Radiograph illustrating the coracoclavicular distance as the vertical distance between the anterior–inferior border of the clavicle and the superior border of the coracoid process.
drilled in a similar fashion at the center of the distance between anterior and posterior border of the clavicle. The guide wire and the drill were removed and the TightRope device (Arthrex, Naples, FL) was inserted first through the clavicle and then through the coracoid tunnel using the Button Inserter. The oblong button was flipped and seated underneath the coracoid process by pulling one of the two traction sutures. Finally, the AC joint was reduced into anatomical position under fluoroscopic visualization, the round button was advanced to the cephalad surface of the clavicle and the ends were secured by a minimum of 5 alternating knots while an assistant held the reduction. Postoperative protocol included shoulder immobilization in a sling for 4 weeks followed by progressive range of motion and strengthening exercises. Daily activities are resumed after 3 months and return to sports activities was allowed after 6 months. Statistical analysis Statistical comparison of functional scores and radiographic measurements was performed using the paired t-test. All tests were calculated with use of the SPSS, version 16.0 (SPSS Inc., Chicago, IL) statistic package for personal computers. In all instances, pvalues < 0.05 were regarded as statistically significant. Results Twelve patients who met the inclusion criteria were followedup for a mean of 18.25 months (range: 12–30 months) (Table 1). The mean age of the patients at the time of surgery was 27.5 years (range: 19–39 years). There were 9 male and 3 female patients. The involved side was the right shoulder in 8 cases and the left in 4. The dominant shoulder was involved in 10 patients. Eight patients were operated on for grade III AC joint dislocation and 4 for grade IV. All patients with grade III AC joint dislocation were men and manual laborers (6 patients) or high-demand upper extremities athletes (2 patients). Initial trauma involved motor vehicle accidents in 6 cases (50%), sport injuries in 3 (25%), and falls in 3 cases (25%). The mean time from injury to surgical management was 5 days (range: 2–14). All patients were operated by the same surgeon. Functional results At the most recent follow-up, the mean Constant score was 94.8 (range: 84–100) showing a significant increase compared with the mean pre-operative value of 34.4 (range: 25–52) (p < 0.001). All
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8 8 12 10 18 12 14 13 11 12 10 8
Return to work (weeks)
9.2 10.3 11 9 10.2 12.2 10.3 10 8.3 10.8 10.4 9.2 9.6 11.8 12.4 9 12.1 12.8 11.4 10.1 8.8 12 10.4 9.7
Radiographic results
Fall Sports MVA Fall MVA Sports MVA MVA Fall MVA Sports MVA
2 3 2 6 14 3 4 4 11 2 7 3
12 18 20 14 24 12 18 15 30 18 14 24
32 52 33 44 28 38 31 25 39 30 28 33
98 100 100 100 90 99 89 94 98 84 84 100
6 5 5 7 5 5 7 7 4 4 7 7
0 0 0 0 0 0 0 0 0 2 0 0
21 18 15 23 16 14 22 26 18 14 20 28
0 0 0 0 0 0 0 0 0 3 0 0
At the last follow-up, radiological assessment revealed complete reduction of the AC joint. The mean CC distance on the operated shoulder did not show a significant difference from the mean CC distance on the contralateral normal side (10.5 vs. 10 mm) (p > 0.05). In all cases both metallic buttons remained in the correct position (Fig. 2). There was no evidence of AC joint
MVA: motor vehicle accident. * According to Rockwood classification. ** CC distance: coracoclavicular distance.
III IV III III III III IV IV III III III IV Right Right Left Right Right Right Left Right Left Right Right Left M M M M M M F F M M M F 1 2 3 4 5 6 7 8 9 10 11 12
29 21 31 26 22 19 24 29 34 23 33 39
Yes Yes Yes Yes No Yes Yes Yes No Yes Yes Yes
Pre-op. Post-op. Pre-op.
Post-op.
Pre-op.
Post-op.
Affected side
Contralateral side
Excellent Excellent Excellent Excellent Good Excellent Excellent Excellent Excellent Good Good Excellent
Subjective result CC Distance** (mm) DASH score VAS score Constant score Follow-up (months) Time interval from injury to surgery (days) Mechanism Grading of injury* Dominant extremity Side Age Gender No.
Table 1 Patients’ details.
parameters of the Constant score, including pain, daily life activity, range of motion, and strength were significantly higher at the last follow-up. The mean DASH score was significantly decreased from 19.6 (range: 14–28) preoperatively to 0.25 (range: 0–3) at the last follow-up (p < 0.001). Similarly, the mean VAS score showed a significant decrease from 5.75 (range: 4–7) to 0.2 (range: 0–2) (p < 0.001). Nine patients (75%) were very satisfied with the postoperative result while 3 (25%) were satisfied. All patients reported that would undergo the same procedure if sustain a similar lesion to the contralateral shoulder. All patients resumed their former work with a mean time to resumption of 10 weeks (range: 9–11 weeks). There were no complications. None of the patients required additional procedures for recurrent AC joint dislocation.
None None None None None None None None None Shoulder pain None None
Complications
290
Fig. 2. (A) Preoperative radiograph of the right shoulder of a 26-year-old male patient who sustained a type III acromioclavicular joint dislocation after fall. His coracoclavicular distance measured 23 mm and his Constant score 44. (B) Radiograph of the right, dominant shoulder at the final follow-up 14 months after surgery demonstrating anatomical reduction of the acromioclavicular joint with coracoclavicular distance measured 9 mm on both shoulders. His Constant score was 100.
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osteoarthrosis, CC calcification, or osteolysis of the distal clavicle or the coracoid process. Discussion The high complication rate associated with the great variety of methods reported in the literature for the management of acute AC joint dislocation reflects the ineffectiveness to restore the normal physiology of the AC joint complex. Temporary fixation with pins or cerclage is no longer recommended because of the increase incidence of degenerative AC joint changes, bony erosion, pin breakage and intrathoracic migration.25,26 A second procedure for implant removal is also needed. Coracoid process transfer provides a dynamic stabilization with high rate of complications including injury to the musculocutaneous nerve.27 The concept of the popular coracoacromial ligament transfer or Weaver–Dunn procedure with its various modifications is that the transfer will allow the CC ligaments to heal and withstand forces equivalent to tensile strength. However, it has been proven that the coracoacromial ligament is biomechanically inferior in comparison to tendon graft reconstruction and may lead to subluxation or dislocation of the AC joint in 30% of the cases in the chronic setting.28 In order to overcome these complications, anatomic reconstruction of the main restraints of the AC joint has been proposed. It has been shown that CC ligaments contribute two-thirds of the restraining force to vertical translation, whereas the AC ligaments and capsule limit horizontal displacement.29–32 More recently, biomechanical studies support the unique role of each ligament of the CC ligament complex with the conoid ligament being the prime suspensor in anterior and superior translation of the clavicle, especially under high loads, and the less important role of the trapezoid ligament.33,34 By placing a prosthetic device, such as the TightRope, in place of CC ligaments a single structure is used to reduce distal clavicle. No auto- or allograft and no implant removal are required. Two titanium buttons, one round clavicular and one long coracoidal, are used to allow homogenous distribution of loads on bone surfaces and thus avoid the sawing effect of the sutures associated with failure in other anchor and suture techniques.35,36 A continues loop of No. 5 FiberWire suture (Arthrex, Naples, FL) organized as a pulley is used to connect the two buttons placed on the top of the clavicle and under the coracoid. Imhoff and Chernchujit37 showed that No. 5 FiberWire failed at 485 N whereas the native CC ligament complex failed at 589 N. Thus, the tensile strength of two strands of No. 5 FiberWire is higher than the tensile strength of intact CC ligament complex. Although there is no longterm study evaluating the effectiveness of this technique, Walz et al.16 based on second-look arthroscopy findings of biologic reaction around the TightRope device after 6 weeks and 3 months hypothesized that long-term stability may be achieved by scarring the ligament stumps with soft tissue complexes. First generation of double-button fixation system has been associated with unacceptable rate of loss of reduction because of the small size, round proximal button that resulted in erosion of the superior surface of the clavicle.19,38,39 This is also a characteristic finding in synthetic ligament reconstruction technique that uses a polyester ligament threaded under the coracoid and fixed to the clavicle by means of 2 polyethylene plugs.40 Newer devices consist of a large clavicle button that prevents bone erosion. In our series, a second generation TightRope with a big proximal titanium button was used in all cases. After a mean follow-up of 18.25 months, we did not record any bone erosion or loss of reduction secondary to implant failure. Accurate placement of the device is also of paramount importance. The coracoid process should be drilled at its center on the coronal plane and close to the neck were the coracoid give off the scapula. This area
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has greater resistance compared with the anterior part of the coracoid which is important in order to avoid erosion and cephalad migration of the button. In addition, the clavicle tunnel should be drilled halfway between the anterior and posterior border of the clavicle. Recently, double-button fixation system has been used for anatomic reconstruction of the CC complex by placing 2 TightRope devices through individual tunnels in the clavicle.16 Based on the cadaver study of Rios et al.41 reconstruction of the trapezoid and conoid ligaments was performed by placing two independent tunnels medial from the lateral clavicular edge in a distance equal with 17% and 30% of the total clavicle length, respectively. The study was performed in 40 fresh-frozen cadaveric shoulders and showed that the mean maximum static load until failure in native CC complex for vertical force measured 598 N and stiffness 99 N/ mm, and for anterior static force 338 N and stiffness 140 N/mm. The mean maximum static load until failure in double TightRope reconstruction for vertical force measured 982 N and stiffness 80 N/mm, and for anterior static force 627 N and stiffness 78 N/ mm. The authors concluded that this method withstand much higher forces than the native ligament complex with only the bicortical CC screw technique showing more strength. The lower stiffness of the reconstructed complex was attributed to the quadrupled FiberWire. These findings were in accordance with La¨dermann et al.8 biomechanical study in which the Twin Tail TightRope system (Arthrex, Naples, FL) was compared with AC and CC cerclages and locking compression superior and anterior clavicle plate. The Twin Tail TightRope and the AC and CC cerclage systems demonstrated similar biomechanical performances with the former showing higher superoinferior and anteroposterior stiffness. The authors supported that the increased stiffness and the lower motion in the superior direction noted with the Twin Tail TightRope system may have prevented the progressive relaxation noticed with the AC and CC cerclage system. The main pattern of failure associated with the Twin Tail TightRope system was the complete cutout of the coracoid button. Acute AC joint reconstruction with the double-button fixation system can be performed through an open or an arthroscopic approach. The theoretical advantages of the arthroscopic approach are the better cosmetic results, and the ability to address any associated conditions to AC joint dislocation, such as associated glenohumeral pathology.19 The excellent functional outcomes that have been reported after arthroscopic AC joint reconstruction have made some authors to recommend this procedure in any acute AC joint reconstruction and reserve open approach for subacute and chronic cases.18 In the present study, we describe a mini-open approach that can effectively restore the AC joint and CC ligament complex anatomy. The procedure is fast and relatively simple. Through 2 small skin incisions of 1 and 2.5 cm made over the top of the clavicle and the coracoid process, respectively, both bone tunnels can be drilled with minimal damage to the soft tissues surrounding the CC ligaments while allowing adequate visualization of the coracoid for accurate tunnel placement. Limitations of our study include its retrospective design, the small number of patients, and the relative short-term follow-up. Because of the favorable functional and radiographic results we continue to use the same technique in all our patients with acute AC joint dislocation requiring surgical management. We also continue to follow-up the already operated patients in order to evaluate whether the promising outcomes will be maintained on a mid- and long-term basis. Conclusions Treatment of acute type III and IV AC joint dislocation with TightRope system gave satisfactory functional and radiographic
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results. In the light of these findings we recommend this technique for all type IV injuries and for type III injuries in heavy manual workers and high-demand upper extremities athletes, such as throwers. Accurate placement of the device at the centre of the base of the coracoid process is of paramount importance. The proposed mini-open technique provides adequate exposure of the base of the coracoid with minimal damage to the soft tissues surrounding the CC ligaments while ensures an excellent cosmetic result. Conflict of interest statement There are no financial and personal relationships with other people or organisations that could inappropriately influence (bias) this work. References 1. Kocher MS, Dupre MM, Feagin Jr JA. Shoulder injuries from alpine skiing and snowboarding: aetiology, treatment, and prevention. Sports Medicine 1998; 25:201–11. 2. Kaplan LD, Flanigan DC, Norwig J, Jost P, Bradley J. Prevalence and variance of shoulder injuries in elite collegiate football players. American Journal of Sports Medicine 2005;33:1142–6. 3. Kelly BT, Barnes RP, Powell JW, Warren RF. Shoulder injuries to quarterbacks in the national football league. American Journal of Sports Medicine 2004;32:328– 31. 4. Rockwood Jr CA. Injuries to the acromioclavicular joint. In: Rockwood Jr CA, Green DP, editors. Fractures in Adults. 2nd ed. Philadelphia, PA: JB Lippincott; 1984. p. 860. 5. Rawes ML, Dias JJ. Long-term results of conservative treatment for acromioclavicular dislocation. Journal of Bone and Joint Surgery British Volume 1996;78:410–2. 6. Calvo E, Lopez-Franco M, Arribas IM. Clinical and radiologic outcomes of surgical and conservative treatment of type III acromioclavicular joint injury. Journal of Shoulder and Elbow Surgery 2006;15:300–5. 7. Nuber GW, Bowen MK. Acromioclavicular joint injuries and distal clavicle fractures. Journal of the American Academy of Orthopaedic Surgeons 1997; 5:11–8. 8. La¨dermann A, Gueorguiev B, Stimec B, Fasel J, Rothstock S, Hoffmeyer P. Acromioclavicular joint reconstruction: a comparative biomechanical study of three techniques. Journal of Shoulder and Elbow Surgery 2012, in press. 9. De Tullio V, Orsi R, Celenza M. Surgical treatment of Allman type III acromioclavicular dislocation. A long-term follow-up study. Acta Orthopaedica Belgica 1994;60:300–2. 10. Sim E, Schwarz N, Hocker K, Berzlanovich A. Repair of complete acromioclavicular separations using the acromioclavicular-hook plate. Clinical Orthopaedics and Related Research 1995;314:134–42. 11. Sundaram N, Patel DV, Porter DS. Stabilization of acute acromioclavicular dislocation by a modified Bosworth technique: a long-term follow-up study. Injury 1992;23:189–93. 12. Tienen TG, Oyen JF, Eggen PJ. A modified technique of reconstruction for complete acromioclavicular dislocation: a prospective study. American Journal of Sports Medicine 2003;31:655–9. 13. Mazzocca AD, Santangelo SA, Johnson ST, Rios CG, Dumonski ML, Arciero RA. A biomechanical evaluation of an anatomical CC ligament reconstruction. American Journal of Sports Medicine 2006;34:236–46. 14. Greiner S, Braunsdorf J, Perka C, Herrmann S, Scheffler S. Mid to long-term results of open acromioclavicular-joint reconstruction using polydioxansulfate cerclage augmentation. Archives of Orthopaedic and Trauma Surgery 2009; 129:735–40. 15. Heitemeyer U, Hierholzer G, Schneppendahl G, Haines J. The operative treatment of fresh ruptures of the acromioclavicular joint (Tossy III). Archives of Orthopaedic and Trauma Surgery 1986;104:371–3. 16. Walz L, Salzmann GM, Fabbro T, Eichhorn S, Imhoff AB. The anatomic reconstruction of acromioclavicular joint dislocations using 2 TightRope devices: a biomechanical study. American Journal of Sports Medicine 2008;36:2398–406.
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