Secondary Logo

Share this article on:

Challenges in Treating Acromioclavicular Separations: Current Concepts

Cook, Jay B., MD; Krul, Kevin P., MD

JAAOS - Journal of the American Academy of Orthopaedic Surgeons: October 1, 2018 - Volume 26 - Issue 19 - p 669–677
doi: 10.5435/JAAOS-D-16-00776
Review Article

Injuries to the acromioclavicular joint constitute approximately 3.2% of shoulder injuries. Although the overall goal of treatment continues to be return to activity with a pain-free shoulder, the treatment of acromioclavicular joint separations has been fraught with conflict since the earliest reports in both ancient and modern literature. Accurate diagnosis and classification are important to determine the optimal treatment. Nonsurgical therapy remains the mainstay for treatment of low- and most mid-grade injuries, although recent biomechanical and biokinetic data might suggest that patients are more affected than traditionally thought. High-grade injuries often necessitate surgical intervention, although little consensus exists on the timing or technique. New surgical techniques continue to evolve as more biomechanical data emerge and kinematic understanding improves. Challenges associated with management of this injury abound from diagnosis to reconstruction.

From the Department of Orthopaedics, the Winn Army Community Hospital, Fort Stewart, Georgia (Dr. Cook), and the Department of Orthopaedics, the Tripler Army Medical Center, Honolulu, Hawaii (Dr. Krul).

Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Cook and Dr. Krul.

Acromioclavicular joint (ACJ) separations are common injuries and compose a sizeable portion of shoulder injuries.1 Rates of ACJ injuries are higher in men and contact athletes, specifically those who participate in rugby, wrestling, and hockey.2 Traditional management has largely been nonsurgical for low-grade injuries and surgical for high-grade injuries.1 Controversy has persisted on the optimal treatment of the mid-grade injury type. Changes in surgical techniques and biomechanical analysis have created new areas of interest with regard to treatment of this injury and introduced questions on how, when, and why the injury should be optimally treated.

Back to Top | Article Outline

Anatomy

The ACJ is a true synovial joint with the articular cartilage, a capsule, and several stabilizing ligaments. It is an important stabilizer to the shoulder girdle, providing support to the entire suspensory complex. When a complete ACJ separation occurs, this suspensory complex is no longer able to provide support to the shoulder and the acromion, scapula, and upper extremity sag creating the appearance of the “shoulder separation.”3 , 4

The stability of the ACJ is twofold: the stability of the acromion is bony with contributions from the coracoacromial ligament, whereas the stability of the distal clavicle is largely ligamentous. The acromioclavicular (AC) ligaments provide stability directly at the ACJ; they are the primary restraint to the anterior and posterior motion of the distal clavicle and consist of the anterior, posterior, superior, and inferior ligaments.5 The coracoclavicular (CC) ligaments connect the coracoid to the clavicle and provide the main restraint to superior translation of the clavicle through the laterally based trapezoid and the medial conoid ligaments.5

The locations of the conoid and trapezoid ligament insertion sites have been studied rather extensively. The coracoid insertions sites are located near the base of the coracoid, with the conoid more medial and posterior than the trapezoid.4 The clavicular insertions are described in terms of distances from the lateral border of the clavicle and ratios of this distance with respect to clavicular length.6 The center of the trapezoid attachment is roughly 26 mm from the ACJ, with an average ratio of approximately 0.17; the medial border of the conoid insertion is approximately 46 mm from the ACJ, with an average ratio of 0.31 (note measurements to the center of the conoid insertion average 35 mm or a ratio of 0.24)6 (Figure 1).

Figure 1

Figure 1

Back to Top | Article Outline

Physical Examination

ACJ separations are characterized by pain, tenderness, and swelling at the ACJ. Because of the mechanism of injury, a complete evaluation of the appendicular and axial skeleton is warranted. Most patients will have difficulty complying with a complete shoulder examination. A 1 to 2 mL injection of local analgesic may assist with the examination. If there is gross deformity, the reducibility of the ACJ has been used to define the lesion.7 For displaced injuries, because the injury represents depression of the scapula and not true elevation of the clavicle, the reduction maneuver must include a superior directed force on the scapula, shoulder, or elbow and an inferiorly directed force on the clavicle. An irreducible ACJ represents interposition of fascia or cartilage and has been described as an indication for surgery.7

Back to Top | Article Outline

Radiographic Evaluation

Standard radiographs with or without stress are usually sufficient to make the radiographic diagnosis. Typically, the radiographic examination begins with a shoulder series (ie, AP, scapular Y, and axillary views) but may also include weighted, cross-arm AP, or Zanca views. The cranial tilt of a Zanca view allows better visualization of the ACJ. An axillary view can demonstrate posterior displacement of the distal clavicle. Weighted views can differentiate grades of injury, and a cross-arm (adducted) view may demonstrate dynamic instability if the clavicle rides over the acromion. Imaging of bilateral shoulders is required for accurate classification purposes (discussed later).

MRI can provide further information, but it is not routinely necessary for making the diagnosis. It can assist with identifying associated injuries such as labral tears or rotator cuff injuries requiring treatment, which have been cited to be present in up to 30% of injuries.8 Typically, the authors order MRI to assist with surgical planning if the ACJ injury meets indications for surgery or if there is suspicion for concomitant injuries based on the examination in lower-grade ACJ injuries.

Back to Top | Article Outline

Classification

The classification of ACJ separations is based on the type or amount of displacement associated with the injury. Rockwood adapted the original work of Tossy into the current classification that is used by most surgeons.3 , 9

This classification uses AP radiographs of the shoulder. The amount of displacement is traditionally measured using the CC distance defined as the distance from the superior aspect of the coracoid vertically to the clavicle. Once the measurement on the injured side is complete, it is compared with the contralateral side to determine displacement. Displacement has also been measured from the superior-medial border of the acromion to the superior-lateral aspect of the clavicle to determine the percentage of displacement (Figure 2). The anatomic correlations to the radiographic findings are described later and summarized in Table 1.

Figure 2

Figure 2

Table 1

Table 1

Type I injury: characterized by injury to the AC ligaments without complete tear. The CC ligaments are uninjured. No deformity exists.

Type II injury: represents an injury to the AC ligaments with complete disruption; the CC ligaments are partially injured without a complete tear. Complete disruption of the AC ligaments leads to horizontal instability and frequently some slight radiographic asymmetry.

Type III injury: complete tears of both the CC and AC ligaments exist. Because of the horizontal and vertical instability, there will be gross deformity at the joint. The deltoid origin and trapezius are completely detached. Alternatively, the force of injury is transmitted to the coracoid and results in a fracture at the insertion of the CC ligaments.

Type IV injury: posterior separation of the ACJ exists. The force at the lateral edge of the acromion results in the anterior displacement of the acromion and the posterior displacement of the clavicle. The result is complete tears of the CC and AC ligaments and notable deformity of the posteriorly displaced clavicle.

Type V injury: a more severe type III injury. The CC and AC ligaments are completely detached, as are the fibers of the trapezius and anterior deltoid attachments, with increased displacement of the joint versus a type III.

Type VI injury: an inferior separation of the clavicle. The clavicle is displaced either below the acromion or below the coracoid. The AC ligaments are disrupted. The CC ligaments, trapezial fascia, and anterior deltoid are all likely to be injured.

Although there is some controversy with regard to clinical validation, the Rockwood classification was introduced to provide an anatomic description that guides treatment. The randomized controlled trials that have defined modern nonsurgical treatment used the older classifications of either Tossy or Allman.10 , 11 In contrast to the older classifications, the Rockwood classification further delineates the mid- to high-grade injuries and recommends surgical intervention in grades IV, V, and VI. In the previous trials, a Tossy or Allman grade III would include Rockwood types III and V, making the applicability of these classification systems questionable in high-grade injuries.9 Furthermore, type III injuries can include both stable and unstable injuries. Although these injuries are traditionally treated nonsurgically, some patients do poorly with nonsurgical management and require surgical intervention. A statement by the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine suggests the need for a IIIa and IIIb modification; the former refers to an inherently stable injury likely to be successfully treated with nonsurgical management, and the latter refers to an unstable injury likely to result in continued pain, instability, and scapular dyskinesia if treated nonsurgically.12 Currently, the most accepted classification is the Rockwood classification. However, the authors agree that stable and unstable type III injuries need to be differentiated.

Back to Top | Article Outline

Nonsurgical Treatment

Type I and II Injuries

Nonsurgical treatment has been the mainstay of treatment for type I and type II injuries.7 Evidence to support this treatment is limited, but several studies have demonstrated its efficacy. Pallis et al2 reported on 145 college athletes with low-grade (type I and type II) injuries, and only 6 patients failed nonsurgical treatment and went on to surgery. Mouhsine et al13 also examined the outcome of nonsurgical treatment for low-grade injuries and reported that half became asymptomatic with time.

Back to Top | Article Outline

Type III Injuries

The optimal treatment of type III injuries has long been the subject of debate. The review by Johansen et al11 thoroughly discusses the several prospective randomized articles, performed nearly 20 to 40 years ago, that have shown no benefit to surgical treatment because the nonsurgical cohorts had fewer complications and faster return to work. Systematic reviews, the most recent by Beitzel et al14 in 2013, have not shown significant functional outcome benefit with surgical treatment compared with nonsurgical treatment. Despite more anatomic outcomes, surgical treatment results in higher complication rates, slower return to work, and equivalent range of motion.14 Consequently, type III injuries have largely been treated nonsurgically the past few decades. However, more recent studies have described altered shoulder mechanics and scapular dyskinesia with AC separations.15 , 16

Back to Top | Article Outline

Type V Injuries

Type V injuries are treated surgically, although little evidence exists to support this treatment. The only level I or level II published data on non–surgically treated severe Tossy type III separations come from Bannister's10 randomized controlled trial. These patients had 2 cm of displacement, and, in the authors' opinion, these would be consistent with a Rockwood type V. In the nonsurgical group, four of five patients had fair or poor outcomes.10 A more recent study examined nonsurgical management of type V injuries demonstrating that most patients will return to work; however, those with >2 cm of displacement of the clavicle above the acromion were more likely to fail nonsurgical therapy.17 One other review examined type V injuries and noted that 77% of patients were able to return to work with nonsurgical management, half being manual laborers, despite modest ASES (American Shoulder and Elbow Society) and DASH (Disabilities of the Arm, Shoulder, and Hand) scores.18

Back to Top | Article Outline

Author's Preferred Nonsurgical Treatment Protocol

Multiple methods of casting and sling wear attempting to externally hold an AC reduction have been used.7 Notably, patient compliance is low, and no method has been proven to be more effective than a simple sling or shoulder immobilizer and activity modification.7 , 14 Patients undergoing nonsurgical treatment are removed from sport until symptoms resolve.

Currently, the authors do not attempt a reduction when undergoing nonsurgical treatment. Patients are treated with a sling for 2 to 3 weeks until much of the acute pain resolved, followed by therapy and early range of motion. For type I and II injuries, surgery is considered if patients remain symptomatic or unable to return to sport after 3 to 6 months of therapy and rehabilitation. Patients with a type III injury or a type V injury with <2 cm displacement and without medial-lateral instability with the clavicle not overriding acromion are brought back after 3 to 4 weeks from injury for repeat evaluation. Those who report significant improvement in pain and motion, as well as minimal scapular dyskinesia, are counseled to continue nonsurgical management. If the patients are noted to have marked scapular dysfunction and minimal improvement in pain, stability of the joint is evaluated clinically and radiographically, and surgical intervention may be offered at this point. Other considerations with regard to work demands and the ability to comply with postoperative restrictions are also taken into account in the treatment algorithm.19

Back to Top | Article Outline

Surgical Treatment

More than 150 techniques for surgical treatment of AC injuries have been described.14 These techniques have generally fallen into several categories: AC fixation, CC fixation, or ligament reconstruction. On principle, acute injuries with the capacity to heal can do well with techniques that hold the reduction and allow for healing. Typically, chronic injuries require some form of biologic augmentation, most commonly with the use of a tendon graft. In the low-grade, symptomatic type I and II injuries that have failed nonsurgical treatment, an open or arthroscopic distal clavicle excision may be appropriate to provide pain relief.

AC fixation has historically involved plates, screws, or wires across the ACJ in the acute setting.7 Most commonly today, this consists of hook plates, which are secured to the clavicle with screws and span the ACJ maintaining reduction by hooking under the acromion. The plates are frequently removed approximately 3 months postoperatively. The hook plate has previously been demonstrated to result in higher outcome scores compared with nonsurgical treatment, however lower scores compared with a modified Weaver-Dunn technique.20 A more recent randomized control trial demonstrated equally good functional outcome scores between hook plate fixation and nonsurgical treatment.21

CC fixation was traditionally performed with a screw from the clavicle to the coracoid; however, modern techniques have used suspensory fixation for CC fixation in place of the rigid screw, particularly with acute injuries.22 One study compared the Bosworth screw with a suture button for treatment of acute injuries and noted no difference in maintenance of reduction, but increased patient satisfaction with the suture button.23 Fixation with one or two suture buttons as an acute repair technique has been shown to have high biomechanical stability.24 This technique is optimal for repair of acutely torn ligaments, providing stabilization to allow the native ligaments to heal.25

Modern techniques have also moved toward anatomic reconstructions using tendon grafts with or without suspensory devices used in conjunction with the graft, particularly for more chronic injuries.19 , 26 - 29 Multiple biomechanical studies have shown anatomic CC ligament reconstruction to have biomechanical properties similar to the native joint, significantly better than older techniques.30 , 31 The anatomic reconstruction was first described by Mazzocca et al32 over a decade ago. Since this description, the technique has been modified with regard to graft type, graft configuration, graft placement, fixation method, augmentation, and incorporation of graft limbs into the AC ligaments.1 , 14 , 19 , 28 , 31 - 34 As of yet, there has been no establishment of a single modification of the anatomic technique that is superior to the rest, although anatomic reconstruction seems to be preferable to nonanatomic reconstruction, given available data.14

Back to Top | Article Outline

Other Controversies in Surgical Treatments

Timing

Early versus delayed treatment continues to be a subject of debate. Few articles have compared early surgery versus delayed treatment, but the existing data trend toward improved patient satisfaction and radiographic outcomes with early treatment.35 - 37 Nevertheless, there is some difficulty drawing generalized conclusions because the available data include low-level studies with different definitions on “acute.”14 Conceptually, acute surgical treatment affords the ability to stabilize the ACJ and allows the native ligaments to heal, ideal for techniques not including biologics.25 However, the recommendation cannot be made to treat all potentially surgical ACJ separations with an acute repair, given the available data on surgical versus nonsurgical treatments. Such an algorithm would result in a potentially high number of patients undergoing surgery who would otherwise do well nonsurgically.

The counterargument is that delayed reconstruction better selects those patients who require surgery as they have failed nonsurgical management. Despite the aforementioned literature suggesting that acute repairs have better outcomes, delayed reconstructions improve outcomes from preoperative levels without subjecting patients to potentially unnecessary surgery (see Outcomes section). Delaying the reconstruction maximizes the number of patients who can be successfully treated nonsurgically.

If patients could be identified who would fail nonsurgical management, rehabilitation would be expedited if early surgery were performed. Several factors have been identified that might suggest which patients will likely fail nonsurgical management. The first is highly unstable injuries, types IV and VI specifically.7 The second is type V injuries, but specifically, if there is >2 cm displacement at the ACJ as some type V injuries can do well with nonsurgical treatment.17 , 18 Finally, dynamically unstable type III injuries will often fail nonsurgical treatment and merit consideration for surgery as recommended by International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports; these can be identified by a cross-arm AP radiograph noting the clavicle overriding the acromion or axillary radiographs with the arm abducted and adducted to evaluate for posterior displacement.12 , 19 However, these factors have not yet been prospectively validated.

Back to Top | Article Outline

Distal Clavicle Excision

Reduction of the ACJ can usually be achieved without much difficulty in the more acute setting. However, a distal clavicle excision is sometimes required to obtain reduction of chronically dislocated ACJs. Although it has been argued to retain the distal clavicle for bony stability, two recent biomechanical studies have shown that there does not appear to be a significant increase of strain on the graft with a small excision of the distal clavicle. Beitzel et al38 showed that with an intact posterior-superior AC capsule, a 5-mm resection added minimal anterior or posterior translation, but this increased with a 10-mm resection. The authors recommended maintaining the posterior-superior capsule or considering AC capsule reconstruction if needed in the setting of an AC separation.38 Beaver et al39 demonstrated no increased anterior to posterior or superior to inferior translation with biomechanical testing of a CC ligament reconstruction with and without 7 mm of distal clavicle resection.

Two studies have examined the presence or absence of distal clavicle excision as it related to early radiographic failure, but did not show any statistically significant difference between the two groups with regard to loss of reduction postoperatively.36 , 40 No other study has directly compared reconstructions with and without a distal clavicle excision with regard to functional outcome scores or revision rates. Currently, the authors' preferred approach is to attempt a closed reduction visualized with fluoroscopy after the patient is placed under anesthesia prior to prepping the shoulder. If the ACJ is unable to be reduced fully, the incision will be extended to allow for removal of the meniscal homologue or any interposed tissue and then proceed with a 5-mm distal clavicle resection with an imbrication of the capsule and possible augmentation with a limb from the graft.

Back to Top | Article Outline

Graft Type

Most techniques describe the use of allograft as a tendon source, but autograft has also been described.19 , 26 - 29 , 36 One study looked at allograft versus autograft as a risk factor for early radiographic failure, noting a higher failure rate in the allograft group (37.5% versus 16.7%) but was underpowered to show significance with regard to radiographic failure.36 There are no studies designed to directly comparing allograft and autograft for use in biologic augmentation in CC ligament reconstruction, and it is unknown at this time what role graft type plays in failure or loss of reduction in CC ligament reconstruction.

Back to Top | Article Outline

Author's Preferred Surgical Technique

As stated previously, most patients are given a trial of nonsurgical treatment for Rockwood types I, II, III, and V with <2 cm of ACJ displacement. Early surgical indications include Rockwood types IV, VI, and V with >2 cm of displacement or with medial-lateral instability resulting in the clavicle overriding the acromion in a high demand patient. Other surgical indications include open injuries, or injuries with neurologic deficits, or low-grade injuries (types I and II) that have failed nonsurgical therapy for 3 to 6 months. Patients with types III or V injuries who have failed nonsurgical treatment as mentioned above are also indicated for surgical intervention.

Patients with low-grade injuries and persistent pain can often be treated with a simple distal clavicle excision. Those with higher-grade injuries, symptomatic instability, or significant deformity who have failed nonsurgical management undergo arthroscopically assisted, anatomic reconstruction using biologic and synthetic fixation. As surgical intervention is rarely undertaken within the first 2 to 3 weeks from injury, the same technique is used for both subacute and chronic injuries.

The clavicle is preoperatively templated to place the conoid tunnel at 20% to 25% of the clavicular length from the distal clavicle, and the trapezoid tunnel is placed 1.5 to 2 cm lateral to this (near the anatomic insertion at 17% of clavicular length) (Figure 3). Both the tendon graft and the Dog Bone (Arthrex) are shuttled from the medial tunnel, under the coracoid, up the lateral tunnel. The ACJ is reduced and the suture button is secured, then the graft is secured on top of the clavicle. The remaining limbs may be brought over laterally to augment the AC ligament if desired (Figure 4).

Figure 3

Figure 3

Figure 4

Figure 4

Postoperative rehabilitation includes strict sling wear for 6 weeks. Motion is gradually increased after cessation of sling wear with a goal of full motion at 3 months. Strengthening begins at this point, and patients are allowed back to contact sports or combat missions in the military at 6 months.

Back to Top | Article Outline

Complications

Given the vast number of techniques described for ACJ separations, the array of complications accompanying them has also been quite large. This discussion will focus on those that are specific to recent techniques and are summarized in Table 2. Other, more infrequent complications can include adhesive capsulitis, neuropathy, distal clavicle hypertrophy, and ACJ pain.

Table 2

Table 2

A frequently reported complication is partial or complete loss of reduction.41 Two studies have examined the causes of failure and noted tunnel position, particularly medialization of the conoid tunnel, to be a statistically significant risk factor.36 , 40 Both studies recommend preoperatively templating tunnel position based on the clavicular length, placing the tunnels at the center of the native insertions. However, despite rates of radiographic “failure” reaching up to 53% in these military cohorts, over 82% of patients were functionally able to return to their military duties.36 , 40

Clavicle fractures have been a reported postoperative complication.26 , 33 Biomechanical studies have shown that the holes drilled for bone tunnels in the clavicle render the bone more susceptible to fracture.42 One alternative is to wrap the graft around the clavicle in lieu of placing bone tunnels. Coracoid fractures can also occur, particularly in techniques involving a coracoid tunnel.33 The graft or suture may be placed under the coracoid in a sling fashion to avoid creating a coracoid tunnel. The size of the tunnel and orientation can affect the biomechanical properties of the coracoid and risk of fracture; coracoid tunnels should be as small as possible and placed center-center from superior to inferior to minimize the risk of fracture.43 , 44 The overall rate of fracture, either coracoid or clavicle, has been calculated at 5.3% in a recent systematic review.41

Back to Top | Article Outline

Outcomes

Patient outcomes of anatomic reconstructions are frequently reported as highly successful (Table 3). Many of these reconstructions are chronic injuries. However, even in a military population, return to full duty in service has been reported in over 82%.36 , 40 Acute repairs have also reported high rates of maintenance of reduction and good patient outcomes (Table 4).41

Table 3

Table 3

Table 4

Table 4

As mentioned earlier, many studies have examined acute reconstruction or repair for type III injuries versus nonsurgical treatment and have not found significant differences in outcome measures.11 , 14 A more recent study, including types III, IV, and V, demonstrated again no significant difference in outcome scores at 2 years between surgical intervention with a hook plate and nonsurgical management of acute injuries.21 This study, though well performed, did not describe activity levels of the patients. All patients did return to work; nonsurgical patients tended to have improved outcomes earlier, decreased chance of complications, yet had an increased chance of being dissatisfied with cosmesis.21

Nonsurgical management has been shown to result in altered shoulder mechanics and scapular dyskinesia, decreased bench press strength, and decreased intensity in sport.15 , 16 , 49 Still, there remains a paucity of data evaluating the biomechanics of shoulder motion and strength in a comparison study between a surgical and nonsurgical shoulder. Yet, although scapular dyskinesia is thought to contribute to failure of nonsurgical management, it can persist even after surgical reconstruction.50 This fact again raises the question of whether early treatment with modern reconstruction techniques can lead to better outcomes than nonsurgical treatment.

Back to Top | Article Outline

Summary

ACJ separations are common in the athletic population, yet continue to be challenging to treat. Most ACJ injuries are low or middle grade and should be treated nonsurgically. Surgical intervention is traditionally reserved only for those who fail nonsurgical treatment or those who have the most severe of injuries. However, evidence of good or better results with acute surgical intervention may lead to a change in this treatment algorithm. Currently, data have failed to show improved long-term outcomes with acute repair versus initial nonsurgical treatment. Finally, at present, there is no single superior surgical technique with quality long-term follow-up.

Back to Top | Article Outline

References

References printed in bold type are those published within the past 5 years.

1. Mazzocca AD, Arciero RA, Bicos J: Evaluation and treatment of acromioclavicular joint injuries. Am J Sports Med 2007;35:316–329.
2. Pallis M, Cameron KL, Svoboda SJ, Owens BD: Epidemiology of acromioclavicular joint injury in young athletes. Am J Sports Med 2012;40:2072–2077.
3. Tossy JD, Mead NC, Sigmond HM: Acromioclavicular separations: Useful and practical classification for treatment. Clin Orthop Relat Res 1963;28:111–119.
4. Salzmann GM, Paul J, Sandmann GH, Imhoff AB, Schottle PB: The coracoidal insertion of the coracoclavicular ligaments: An anatomic study. Am J Sports Med 2008;36:2392–2397.
5. Fukuda K, Craig EV, An KN, Cofield RH, Chao EY: Biomechanical study of the ligamentous system of the acromioclavicular joint. J Bone Joint Surg Am 1986;68:434–440.
6. Rios CG, Arciero RA, Mazzocca AD: Anatomy of the clavicle and coracoid process for reconstruction of the coracoclavicular ligaments. Am J Sports Med 2007;35:811–817.
7. Rockwood CA, Green DP, Bucholz RW: Rockwood and Green's Fractures in Adults, ed 7. Philadelphia, PA, Wolters Kluwer Health/Lippincott Williams & Wilkins, 2010.
8. Arrigoni P, Brady PC, Zottarelli L, et al: Associated lesions requiring additional surgical treatment in grade 3 acromioclavicular joint dislocations. Arthroscopy 2014;30:6–10.
9. Williams G, Nguyen V, Rockwood C: Classification and radiographic analysis of acromioclavicular dislocations. Appl Radiol 1989;18:29–34.
10. Bannister GC, Wallace WA, Stableforth PG, Hutson MA: The management of acute acromioclavicular dislocation: A randomised prospective controlled trial. J Bone Joint Surg Br 1989;71:848–850.
11. Johansen JA, Grutter PW, McFarland EG, Petersen SA: Acromioclavicular joint injuries: Indications for treatment and treatment options. J Shoulder Elbow Surg 2011;20(suppl 2):S70–S82.
12. Beitzel K, Mazzocca AD, Bak K, et al: ISAKOS upper extremity committee consensus statement on the need for diversification of the Rockwood classification for acromioclavicular joint injuries. Arthroscopy 2014;30:271–278.
13. Mouhsine E, Garofalo R, Crevoisier X, Farron A: Grade I and II acromioclavicular dislocations: Results of conservative treatment. J Shoulder Elbow Surg 2003;12:599–602.
14. Beitzel K, Cote MP, Apostolakos J, et al: Current concepts in the treatment of acromioclavicular joint dislocations. Arthroscopy 2013;29:387–397.
15. Oki S, Matsumura N, Iwamoto W, et al: Acromioclavicular joint ligamentous system contributing to clavicular strut function: A cadaveric study. J Shoulder Elbow Surg 2013;22:1433–1439.
16. Gumina S, Carbone S, Postacchini F: Scapular dyskinesis and SICK scapula syndrome in patients with chronic type III acromioclavicular dislocation. Arthroscopy 2009;25:40–45.
17. Krul KPC, Cook JB, Cage JM, Rowles DJ, Bottoni CR, Tokish JM: The displacement of the clavicle is a better predictor of surgical intervention in the non-operatively treated acromioclavicular dislocation than the increase in coracoclavicular distance. Orthop J Sports Med 2015;3(7 suppl 2):2325967115S00077.
18. Dunphy TR, Damodar D, Heckmann ND, Sivasundaram L, Omid R, Hatch GF III: Functional outcomes of type V acromioclavicular injuries with nonsurgical treatment. J Am Acad Orthop Surg 2016;24:728–734.
19. Cook JB, Tokish JM: Surgical management of acromioclavicular dislocations. Clin Sports Med 2014;33:721–737.
20. Gstettner C, Tauber M, Hitzl W, Resch H: Rockwood type III acromioclavicular dislocation: Surgical versus conservative treatment. J Shoulder Elbow Surg 2008;17:220–225.
21. Canadian Orthopaedic Trauma Society: Multicenter randomized clinical trial of nonoperative versus operative treatment of acute acromio-clavicular joint dislocation. J Orthop Trauma 2015;29:479–487.
22. Venjakob AJ, Salzmann GM, Gabel F, et al: Arthroscopically assisted 2-bundle anatomic reduction of acute acromioclavicular joint separations: 58-month findings. Am J Sports Med 2013;41:615–621.
23. Darabos N, Vlahovic I, Gusic N, Darabos A, Bakota B, Miklic D: Is AC TightRope fixation better than Bosworth screw fixation for minimally invasive operative treatment of Rockwood III AC joint injury? Injury 2015;46(suppl 6):S113–S118.
24. Beitzel K, Obopilwe E, Chowaniec DM, et al: Biomechanical comparison of arthroscopic repairs for acromioclavicular joint instability: Suture button systems without biological augmentation: Am J Sports Med 2011;39:2218–2225.
25. Di Francesco A, Zoccali C, Colafarina O, Pizzoferrato R, Flamini S: The use of hook plate in type III and V acromio-clavicular Rockwood dislocations: Clinical and radiological midterm results and MRI evaluation in 42 patients. Injury 2012;43:147–152.
26. Millett PJ, Horan MP, Warth RJ: Two-year outcomes after primary anatomic coracoclavicular ligament reconstruction. Arthroscopy 2015;31:1962–1973.
27. Frank RM, Trenhaile SW: Arthroscopic-assisted acromioclavicular joint reconstruction using the TightRope device with allograft augmentation: Surgical technique. Arthrosc Tech 2015;4:e293–e297.
28. Carofino BC, Mazzocca AD: The anatomic coracoclavicular ligament reconstruction: Surgical technique and indications. J Shoulder Elbow Surg 2010;19:37–46.
29. Spencer HT, Hsu L, Sodl J, Arianjam A, Yian EH: Radiographic failure and rates of re-operation after acromioclavicular joint reconstruction: A comparison of surgical techniques. Bone Joint J 2016;98-B:512–518.
30. Thomas K, Litsky A, Jones G, Bishop JY: Biomechanical comparison of coracoclavicular reconstructive techniques. Am J Sports Med 2011;39:804–810.
31. Tauber M, Gordon K, Koller H, Fox M, Resch H: Semitendinosus tendon graft versus a modified weaver-dunn procedure for acromioclavicular joint reconstruction in chronic cases: A prospective comparative study. Am J Sports Med 2009;37:181–190.
32. Mazzocca AD, Conway JE, Johnson S, et al: The anatomic coracoclavicular ligament reconstruction. Oper Tech Sports Med 2004;12:56–61.
33. Martetschlager F, Horan MP, Warth RJ, Millett PJ: Complications after anatomic fixation and reconstruction of the coracoclavicular ligaments. Am J Sports Med 2013;41:2896–2903.
34. Milewski MD, Tompkins M, Giugale JM, Carson EW, Miller MD, Diduch DR: Complications related to anatomic reconstruction of the coracoclavicular ligaments. Am J Sports Med 2012;40:1628–1634.
35. Rolf O, Hann von Weyhern A, Ewers A, Boehm TD, Gohlke F: Acromioclavicular dislocation Rockwood III-V: Results of early versus delayed surgical treatment. Arch Orthop Trauma Surg 2008;128:1153–1157.
36. Cook JB, Shaha JS, Rowles DJ, Bottoni CR, Shaha SH, Tokish JM: Clavicular bone tunnel malposition leads to early failures in coracoclavicular ligament reconstructions. Am J Sports Med 2013;41:142–148.
37. Weinstein DM, McCann PD, McIlveen SJ, Flatow EL, Bigliani LU: Surgical treatment of complete acromioclavicular dislocations. Am J Sports Med 1995;23:324–331.
38. Beitzel K, Sablan N, Chowaniec DM, et al: Sequential resection of the distal clavicle and its effects on horizontal acromioclavicular joint translation. Am J Sports Med 2012;40:681–685.
39. Beaver AB, Parks BG, Hinton RY: Biomechanical analysis of distal clavicle excision with acromioclavicular joint reconstruction. Am J Sports Med 2013;41:1684–1688.
40. Eisenstein ED, Lanzi JT, Waterman BR, Bader JM, Pallis MP: Medialized clavicular bone tunnel position predicts failure after anatomic coracoclavicular ligament reconstruction in young, active male patients. Am J Sports Med 2016;44:2682–2689.
41. Woodmass JM, Esposito JG, Ono Y, et al: Complications following arthroscopic fixation of acromioclavicular separations: A systematic review of the literature. Open Access J Sports Med 2015;6:97–107.
42. Spiegl UJ, Smith SD, Euler SA, Dornan GJ, Millett PJ, Wijdicks CA: Biomechanical consequences of coracoclavicular reconstruction techniques on clavicle strength. Am J Sports Med 2014;42:1724–1730.
43. Martetschlager F, Saier T, Weigert A, et al: Effect of coracoid drilling for acromioclavicular joint reconstruction techniques on coracoid fracture risk: A biomechanical study. Arthroscopy 2016;32:982–987.
44. Campbell ST, Heckmann ND, Shin SJ, et al: Biomechanical evaluation of coracoid tunnel size and location for coracoclavicular ligament reconstruction. Arthroscopy 2015;31:825–830.
45. Glanzmann MC, Buchmann S, Audige L, Kolling C, Flury M: Clinical and radiographical results after double flip button stabilization of acute grade III and IV acromioclavicular joint separations. Arch Orthop Trauma Surg 2013;133:1699–1707.
    46. Torkaman A, Bagherifard A, Mokhatri T, et al: Double-button fixation system for management of acute acromioclavicular joint dislocation. Arch Bone Joint Surg 2016;4:41–46.
      47. Loriaut P, Casabianca L, Alkhaili J, et al: Arthroscopic treatment of acute acromioclavicular dislocations using a double button device: Clinical and MRI results. Orthop Traumatol Surg Res 2015;101:895–901.
        48. Rosslenbroich SB, Schliemann B, Schneider KN, et al: Minimally invasive coracoclavicular ligament reconstruction with a flip-button technique (MINAR): Clinical and radiological midterm results. Am J Sports Med 2015;43:1751–1757.
          49. Schlegel TF, Burks RT, Marcus RL, Dunn HK: A prospective evaluation of untreated acute grade III acromioclavicular separations. Am J Sports Med 2001;29:699–703.
          50. Murena L, Canton G, Vulcano E, Cherubino P: Scapular dyskinesis and SICK scapula syndrome following surgical treatment of type III acute acromioclavicular dislocations. Knee Surg Sports Traumatol Arthrosc 2013;21:1146–1150.
          © 2018 by American Academy of Orthopaedic Surgeons