Osteoarthritis sa AC Joint

This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Overview¶

• Asymptomatic acromioclavicular osteoarthritis remained asymptomatic in 90% of cases over a seven-year course [1].
• Treatment choice for acromioclavicular dislocation should not be influenced by the potential development of acromioclavicular osteoarthritis [2].
• Further characterisation is needed to identify patients in whom mild arthroscopic findings of acromioclavicular joint osteoarthritis are clinically significant and warrant resection [3].
• Persistent pain and osteoarthritis progression remain concerns following revision of failed open anterior stabilization of the shoulder [4].
• Both open and arthroscopic resection arthroplasty techniques provide predictable pain relief for symptomatic acromioclavicular osteoarthritis [5].
• Symptomatic acromioclavicular joint osteoarthritis occurred in 15.9% of patients after total anatomic shoulder replacement with follow-up of up to 12 years [6].
• Untreated acromioclavicular joint osteoarthritis, symptomatic or not, encountered during arthroscopic rotator cuff repair is associated with a low percentage of failure [8].
• Biplanar reconstruction with pectoralis minor tendon and coracoacromial ligament transfer aims to preserve the lateral portion of the clavicle whenever possible, limiting resection exclusively to cases of acromioclavicular joint osteoarthritis or irreducible joints [9].
• Radiographic acromioclavicular joint osteoarthritis is common in patients undergoing reverse shoulder arthroplasty [10].
• Clinicians should consider overreduction of the acromioclavicular joint because it may lead to favorable radiological results [11].
• A distinction between symptomatic and asymptomatic radiographic acromioclavicular osteoarthritis is unnecessary, as all patients were equally satisfied with the outcome following preoperative acromioclavicular injection [12].
• Open and arthroscopic acromioclavicular joint reconstruction techniques have no differences in loss of reduction, the complication rate, and the revision rate [13].
• Arthroscopic debridement of the acromioclavicular joint can produce a favorable result in young patients presenting with isolated acromioclavicular joint-related pain but with normal imaging [15].
• Limited distal clavicle excision of patients with acromioclavicular joint osteoarthritis resistant to conservative treatment reduced pain and improved shoulder function at midterm follow-up [17].
• All patients undergoing free tissue graft reconstruction of the acromioclavicular joint are satisfied with their surgery and demonstrate good reduction of the acromioclavicular joint on radiographs, although follow-up periods are less than 1 year [21].
• Additional research is needed to determine the main cause of pain and compare clinical outcomes of intra-articular versus extra-articular injections for isolated acromioclavicular osteoarthritis [23].
• Nanoscopic distal clavicle resection offers advantages including decreased morbidity, less risk to the acromioclavicular joint ligaments, and decreased loss and need for fluid [44].

Anatomy & Pathophysiology¶

Bony Anatomy and Joint Structure¶

• The acromioclavicular (AC) joint is a diarthrodial joint that supports the shoulder girdle through the clavicular “strut” [36].
• The AC joint serves as a primary link between the axial skeleton and the upper extremity [122].
• The AC joint is movable in all planes and is not a rigid structure [122].
• The normal AC joint is capable of translating 4 to 6 mm in the anterior, posterior, and superior planes under 70-N loads [122].
• The AC joint accommodates rotary motion of 5° to 8° during scapulothoracic motion and 40° to 45° with shoulder abduction and elevation [122].
• The scapula and clavicle are linked into a single segment referred to as the “claviscapula” [112].

Ligamentous Anatomy and Stability¶

• The AC and coracoclavicular (CC) ligaments are the static stabilizers of the AC joint, whereas the deltoid and trapezius muscles are the dynamic stabilizers [122].
• The horizontal plane stability of the clavicle is provided by the AC ligaments, specifically the posterior and superior portions [25].
• The AC and CC ligaments play a role in torque transduction and horizontal and vertical stability [112].
• Injury to the AC joint results in progressive disruption of the ligamentous support, beginning with the capsular ligaments and progressing to the CC ligaments [30].

Pathophysiology of Degeneration¶

• AC joint osteoarthritis is more common with advanced age following degeneration of the intra-articular disk [25].
• Arthritic deterioration of the AC joint starts in early middle age [25].
• AC joint osteoarthritis is more common in patients engaged in repetitive overhead or lifting activities [25].
• Previous low-grade AC joint separations can result in painful arthritis [25].
• The radiographic severity of AC joint arthritis does not always correlate with patient symptoms [25].
• Asymptomatic AC joint degeneration is frequent and does not always correlate with the presence of symptoms [36].
• Degeneration of the AC joint is classified as primary osteoarthritis, posttraumatic osteoarthritis, or distal clavicle osteolysis [123].
• The process of AC joint degeneration begins in the second decade of life and can progress to complete obliteration of the joint [123].
• Complete obliteration of the AC joint can lead to subclavicular spurring, which contributes to subacromial impingement of the supraspinatus [123].
• Asymptomatic AC osteoarthritis remained asymptomatic in 90% of cases over a seven-year course [1].
• Patients with loss of immediate postoperative reduction after AC joint dislocation more often developed radiologic and symptomatic AC osteoarthritis than those in whom the AC joint was anatomically restored [7].
• Kinematic changes associated with AC joint dislocation could be a potential source of pain and dysfunction in the shoulder [59].
• Scapular and clavicular kinematics are affected in AC separation models [60].
• Decoupling the claviscapular segment has deleterious effects on the functional integrity of the AC joint complex within scapulohumeral rhythm [112].

Distal Clavicle Osteolysis¶

• Distal clavicle osteolysis is characterized by localized hyperemia of the distal clavicle, resulting in inflammation, bone resorption, microfractures, and secondary arthritis of the AC joint [25].
• Distal clavicle osteolysis is more common in males and seen in younger patients [25].
• Distal clavicle osteolysis is associated with heavy lifting or repetitive motions [25].
• Osteolysis of the distal clavicle was first reported in conjunction with acute trauma [121].
• Intraarticular distal clavicle fractures and AC separations can lead to osteolysis [121].
• Other causes of distal clavicle osteolysis include rheumatoid arthritis, hyperparathyroidism, and repetitive microtrauma [121].
• The most common cause of distal clavicle osteolysis is repetitive microtrauma [121].
• Radiographic findings indicative of distal clavicle osteolysis include loss of subchondral bone detail, cystic reabsorption of the distal clavicle, and generalized osteopenia of the distal clavicle [121].

Classification¶

• Asymptomatic acromioclavicular osteoarthritis diagnosed by MRI remained asymptomatic in 90% of cases over a seven-year course [1].
• Treatment choice for acromioclavicular dislocation should not be influenced by the potential development of acromioclavicular osteoarthritis based on available evidence [2].
• Patients with loss of immediate postoperative reduction following arthroscopically assisted reduction of acute acromioclavicular joint dislocation more often developed radiologic and symptomatic acromioclavicular osteoarthritis than those in whom the joint was anatomically restored [7].
• Untreated acromioclavicular joint osteoarthritis, whether symptomatic or not, encountered during arthroscopic rotator cuff repair is associated with a low percentage of failure [8].
• Biplanar reconstruction with pectoralis minor tendon and coracoacromial ligament transfer aims to preserve the lateral portion of the clavicle, limiting resection exclusively to cases of acromioclavicular joint osteoarthritis or irreducible joints [9].
• Open and arthroscopic acromioclavicular joint reconstruction techniques have no differences in loss of reduction, complication rate, and revision rate based on available literature [13].
• A study evaluated three groups of patients: 84 acromioclavicular joints without clinical or radiological pathology, 39 patients with signs of osteoarthritis on CT without symptoms, and 30 patients with acromioclavicular joint pain [14].
• In the study of acromion-clavicle relationships, Group 2 included patients with signs of osteoarthritis on CT (joint space narrowing, osteophytes, and/or bone cyst) who were asymptomatic based on physical examination and negative cross-body adduction test [14].
• In the study of acromion-clavicle relationships, Group 3 included patients with acromioclavicular joint pain confirmed by tenderness and temporary pain relief with intra-articular injection, who were treated with open distal clavicle resection after failure of non-operative treatment [14].
• The occurrence of acromioclavicular joint osteoarthrosis was surprisingly frequent in a study of shoulder pain [18].
• Anatomic techniques that address both coracoclavicular ligaments and the acromioclavicular capsule are recommended to restore horizontal and vertical stability while allowing physiological rotation [19].
• The acromial center line to dorsal clavicle radiographic measurement and use of the Alexander view provides a more realistic appreciation of true acromioclavicular joint displacement, especially in defining watershed cases (IIIA/IIB/IV) [22].
• Osteolytic changes seemed to be associated with incongruity of the acromioclavicular joint but did not correlate with clinical results in a review of surgical treatment for acromioclavicular dislocation [24].
• A procedure for exact anatomical acromioclavicular joint reconstruction using acromioclavicular and coracoclavicular FiberWire cerclage shows good objective results with high Constant and Rowe scores for shoulder function [27].
• Preoperative radiographs were evaluated to determine whether there was any osteolysis of the distal clavicle in a study of preoperative factors associated with subsequent distal clavicle resection after rotator cuff repair [31].
• Preoperative radiographs were graded for severity of arthritis per the Petersson classification by two attending orthopaedic surgeons blinded to each other's grade in a study of preoperative factors associated with subsequent distal clavicle resection after rotator cuff repair [31].
• Type V acromioclavicular dislocations may be given a trial of conservative therapy [35].
• Non-operative reduction and stabilization of high-grade acromioclavicular joint separations seems to be a valuable treatment option [45].
• Evaluating the integrity of the capsuloligamentous structures stabilizing the acromioclavicular joint is reproducible and gives additional information on the severity of the injury, which might also influence the treatment decision [49].
• Severe chronic symptomatic acromioclavicular joint separations (Rockwood types III through V) can be repaired entirely by arthroscopy safely and effectively by transferring the coracoacromial ligament with a bone block in the distal clavicle [50].
• The treatment of Type III acromioclavicular joint separation has remained controversial, with many studies demonstrating good results with nonoperative management and most series failing to document the superiority of either operative or nonoperative management [51].
• Surgical management of acromioclavicular joint injuries is associated with a relatively high complication profile and common loss of reduction, though the revision surgery rate is low [53].
• Arthroscopically assisted treatment of acute acromioclavicular joint dislocation provides good clinical results and few complications, though the rate of recurrence and postoperative loss of reduction requires better definition of indications and improvement of surgical implants and technique [55].
• In every coracoclavicular loop repair, regardless of hole placement, complete acromioclavicular joint congruity is not restored [86].
• Given that more than 100 surgical stabilization techniques have been proposed for acromioclavicular joint injuries, a deeper understanding of the underlying anatomy integrated with biomechanical evidence may help guide the development of a standardized, evidence-based approach to treatment [88].
• Early and delayed surgical interventions of high-grade acromioclavicular joint dislocation provide equivalent clinical scores when combined coracoclavicular and acromioclavicular joint fixation is used for stabilization [95].
• Acromioclavicular joint osteoarthritis was graded using the Kellgren-Lawrence classification system in a retrospective cohort study of concomitant open distal clavicle excision after reverse total shoulder arthroplasty [101].

Clinical Presentation¶

History and Symptoms¶

• Patients report activity-related pain localized to the AC joint [25].
• Pain may radiate anteriorly or along the trapezius [25].
• Pain is reported with heavy lifting or when sleeping on the affected side [25].
• AC joint osteoarthrosis is a frequent cause of shoulder pain [18].
• In patients with rheumatoid arthritis, clinical symptoms and radiologic appearances are often poor indicators of the source of pain in the shoulder joint complex [64].

Physical Examination¶

• Point tenderness is seen at the AC joint [25].
• Horizontal stability of the AC joint should be assessed [25].
• Pain at the AC joint with terminal elevation and cross-body motion is often seen [25].
• The adduction sign, where pain is produced in the AC joint during maximal adduction of the internally rotated arm, was positive in all 20 patients with AC joint arthritis in one study [63].
• An average decrease of 5 cm in the distance from the ipsilateral antecubital fossa to the contralateral anterior shoulder was noted during cross-body adduction in patients with AC joint arthritis [63].
• Selective injection of anesthetic into the AC joint can confirm the diagnosis [25].
• Patients with ACJ pain showed clinical signs including AC joint tenderness to palpation and temporary pain relief with intra-articular injection [14].

Imaging¶

• An AP view and/or a Zanca view of the shoulder provides good visualization of the AC joint [25].
• Osteophyte formation, sclerotic reaction, and bone cysts are commonly seen on radiographs of the AC joint [25].
• Bone and joint edema on MRI correlate with AC joint pain [25].
• The radiographic severity of arthritis does not always correlate with patient symptoms [25].
• Radiographic ACJ osteoarthritis is common in patients undergoing reverse shoulder arthroplasty [10].
• Asymptomatic AC-OA remained asymptomatic in 90% of patients over a seven-year course [1].
• A distinction between symptomatic and asymptomatic radiographic AC OA may be unnecessary, as all patients were equally satisfied with the outcome in one study [12].
• Osteolytic changes seemed to be associated with incongruity of the AC joint but did not correlate with clinical results [24].

Investigations¶

Clinical Evaluation¶

• Patients with AC joint osteoarthritis report activity-related pain localized to the AC joint, with occasional radiation anteriorly or along the trapezius [25].
• Pain with heavy lifting or when sleeping on the affected side is reported in patients with AC joint osteoarthritis [25].
• Physical examination of the AC joint reveals point tenderness at the joint [25].
• Horizontal stability of the AC joint should be assessed during physical examination [25].
• Pain at the AC joint with terminal elevation and cross-body motion is often seen in patients with AC joint osteoarthritis [25].
• Selective injection of anesthetic into the AC joint can confirm the diagnosis of symptomatic AC osteoarthritis [25].
• A distinction between symptomatic and asymptomatic radiographic AC OA is unnecessary, as all patients were equally satisfied with the outcome following preoperative injection [12].

Imaging¶

• Patients with edema on MRI were more likely to present pain than patients without edema [92].
• Subchondral bone edema on histologic examination was more frequent in patients with pain [92].
• The AC-DC measurement and use of the Alexander view provides a more realistic appreciation of true AC joint displacement, especially in defining watershed cases (ie, IIIA/IIB/IV) [22].
• Preoperative radiographs are evaluated to determine whether there is any osteolysis of the distal clavicle [31].
• The Petersson classification is used to grade the severity of arthritis on preoperative radiographs [31].
• In a study of AC joint osteoarthrosis, the occurrence was surprisingly frequent [18].

Treatment¶

Non-Operative Management¶

• Rest, ice, and NSAIDs are used initially for AC joint osteoarthritis [25].
• Corticosteroid injections can be used for diagnostic or therapeutic purposes in AC joint osteoarthritis [25].
• AC injections offer a 1-year success rate of 47% [33].
• Conservative and surgical treatments are both effective in acromioclavicular joint osteoarthritis management [38].
• A distinction between symptomatic and asymptomatic radiographic AC OA is unnecessary, as all patients were equally satisfied with the outcome following injection [12].
• Additional research is needed to determine the main cause of pain and compare clinical outcomes of intra-articular versus extra-articular injections [23].

Operative Management: Distal Clavicle Resection¶

• Surgical indications for AC joint osteoarthritis include persistent pain and failure of nonsurgical treatment [25].
• Both open and arthroscopic resection arthroplasty techniques provide predictable pain relief for symptomatic AC osteoarthritis [5].
• Arthroscopic distal clavicle excision provides reliable pain relief in >90% of patients in the absence of instability [25].
• Previous traumatic instability is associated with persistent pain in 30% to 40% of cases following distal clavicle excision [25].
• One systematic review showed slightly better results with arthroscopic excision than with open distal clavicle excision [25].
• Direct comparison studies have shown similar or better results with arthroscopic excision than with open techniques [25].
• Biomechanical evidence suggests a resection of 5 mm is needed to prevent contact between the clavicle and the acromion in the absence of instability [25].
• Care should be taken to preserve the posterior and superior AC ligaments during arthroscopic distal clavicle excision [25].
• Between 5 and 10 mm of the distal clavicle should be resected during an open Mumford procedure [25].
• Meticulous repair of the deltotrapezial fascia is important during open distal clavicle resection [25].
• Limited distal clavicle excision of patients with AC joint osteoarthritis resistant to conservative treatment reduced pain and improved shoulder function at midterm follow-up [17].
• Arthroscopic debridement of the AC joint can produce a favorable result in young patients presenting with isolated AC joint-related pain but with normal imaging [15].
• The nanoscopic distal clavicle resection technique offers advantages including decreased morbidity, less risk to the AC joint ligaments, and decreased loss and need for fluid [44].
• Patients with AC joint instability have poor results after distal clavicle resection [36].
• The optimal amount of distal clavicle resection remains elusive [36].

Operative Management: Concomitant Procedures and Specific Populations¶

• Preventive arthroscopic distal clavicle resection is not recommended in patients with radiological but asymptomatic ACJ arthritis and rotator cuff tears [34].
• Untreated ACJ osteoarthritis, symptomatic or not, encountered during arthroscopic rotator cuff repair is associated with a low percentage of failure [8].
• Further characterisation of patients in whom mild arthroscopic findings of OA of AC joint are clinically significant and warrant resection is needed [3].
• Symptomatic ACJ OA occurred in 15.9% of patients after total anatomic shoulder replacement with follow-up of up to 12 years [6].
• Osteoarthritis is associated with poorer final clinical outcomes after rotator cuff repair, and an unhealed or re-torn cuff increases the risk of osteoarthritis [26].

Operative Management: Reconstruction and Stabilization¶

• Open and arthroscopic AC joint reconstruction techniques have no differences in loss of reduction, the complication rate, and the revision rate based on the available literature [13].
• Treatment choice for AC dislocation should not be influenced by the potential development of AC OA [2].
• Achieving and maintaining satisfactory joint reduction is a factor of good prognosis, both radiologically and functionally, in AC dislocation treatment [7].
• Patients with loss of immediate postoperative reduction more often developed radiologic and symptomatic AC osteoarthritis than those in whom the AC joint was anatomically restored [7].
• Clinicians should consider overreduction of the AC joint because it may lead to favorable radiological results [11].
• Ensuring good initial recovery of the coracoclavicular distance and precise placement of the AC joints was important in maintaining the proper AC position at the final follow-up [46].
• Combined stabilization of the AC capsule and CC ligaments demonstrated the greatest capacity to restore native stability against translational and rotational loads [81].
• The biplanar reconstruction procedure aims to preserve the lateral portion of the clavicle whenever possible, limiting resection exclusively to cases of AC joint osteoarthritis or irreducible joints [9].
• Some persistent pain and osteoarthritis progression remain concerns following revision of failed open anterior stabilization of the shoulder [4].

Complications¶

Natural History and Progression¶

• Patients who experienced loss of immediate postoperative reduction after acute acromioclavicular dislocation more often developed radiologic and symptomatic acromioclavicular osteoarthritis than those in whom the joint was anatomically restored [7].
• Osteoarthritis is associated with poorer final clinical outcomes following rotator cuff repair [26].
• An unhealed or re-torn rotator cuff increases the risk of developing osteoarthritis [26].
• Severe acromioclavicular joint osteoarthritis is associated with acromial stress fractures after reverse shoulder arthroplasty [10].

Surgical Complications and Outcomes¶

• Treatment of acromioclavicular dislocation by synthetic ligament reconstruction carries a risk of significant early osteolysis [56].
• Complications such as anterior shoulder pain, acromioclavicular joint asymmetry, and activity-related weakness are common sequelae of coracoclavicular ligament reconstruction [43].
• Three patients with old acromioclavicular separations had prominence of the distal clavicle or symptoms due to residual hypermobility of the clavicle despite concurrent coracoclavicular stabilization [114, 115, 116, 117].
• A patient who did not undergo anterior acromioplasty despite subacromial impingement had unchanged impingement symptoms after distal clavicle resection [114, 115, 116, 117].
• Open and arthroscopic resection arthroplasty techniques for symptomatic acromioclavicular osteoarthritis each have a unique set of potential complications that may be minimized with improved understanding of anatomy, biomechanics, and meticulous surgical technique [5].

Recovery¶

Natural History and Prognosis¶

• Asymptomatic acromioclavicular osteoarthritis diagnosed by MRI remained asymptomatic in 90% of patients over a seven-year course [1].
• Osteolytic changes associated with incongruity of the acromioclavicular joint did not correlate with clinical results in a review of 39 patients [24].
• An unhealed or re-torn rotator cuff increases the risk of osteoarthritis following rotator cuff repair [26].

Impact of Joint Reduction and Stability¶

• Patients with loss of immediate postoperative reduction after arthroscopically assisted reduction of acute acromioclavicular joint dislocation more often developed radiologic and symptomatic acromioclavicular osteoarthritis than those in whom the joint was anatomically restored [7].
• Achieving and maintaining satisfactory joint reduction is a factor of good prognosis, both radiologically and functionally [7].
• Ensuring good initial recovery of the coracoclavicular distance and precise placement of the acromioclavicular joints was important in maintaining the proper acromioclavicular position at final follow-up [46].

Surgical Considerations Regarding Osteoarthritis¶

• Further characterisation of patients in whom mild arthroscopic findings of acromioclavicular joint osteoarthritis are clinically significant and warrant resection is needed [3].
• Biplanar reconstruction for chronic acromioclavicular joint dislocations aims to preserve the lateral portion of the clavicle, limiting resection exclusively to cases of acromioclavicular joint osteoarthritis or irreducible joints [9].
• The average angle from the central portion of the acromioclavicular joint anteriorly for a novel anterior portal for arthroscopic distal clavicle excision was 6 degrees, with a range of 0 to 15 degrees [29].

Non-Operative Management and Diagnostic Implications¶

• Acromioclavicular injections offer a 1-year success rate of 47% in patients with acromioclavicular osteoarthritis [33].

Key Evidence¶

• [L2] Asymptomatic AC-OA remained asymptomatic in 90% over 7 years. [1] (10.1016/j.jse.2019.04.004)
• [L4] Based on the available evidence, treatment choice for AC dislocation should not be influenced by the potential development of AC OA. [2] (10.2106/jbjs.rvw.24.00085)
• [L2] Further characterisation of patients in whom mild arthroscopic findings of OA of AC joint are clinically significant and warrant resection is needed. [3] (10.1007/s00167-014-3114-2)
• [L4] Some persistent pain and osteoarthritis progression remain concerns. [4] (10.1016/j.arthro.2009.04.073)
• [L5] Both open and arthroscopic resection arthroplasty techniques provide predictable pain relief for symptomatic AC osteoarthritis, though each has a unique set of potential complications that may be minimized with improved understanding of anatomy, biomechanics, and meticulous surgical technique. [5] (10.1177/0363546513485359)
• [L4] Symptomatic ACJ OA occurred in 15.9% of patients after total anatomic shoulder replacement with follow-up of up to 12 years. [6] (10.1177/17585732221114796)
• [L4] [7] (10.1016/j.otsr.2017.11.001)
• [L2] Untreated ACJ osteoarthritis, symptomatic or not, encountered during arthroscopic RCR is associated with a low percentage of failure. [8] (10.1007/s00167-020-06098-y)
• [L5] The procedure aims to preserve the lateral portion of the clavicle whenever possible, limiting resection exclusively to cases of AC joint osteoarthritis or irreducible joints. [9] (10.1016/j.eats.2024.103104)
• [L3] Radiographic ACJ osteoarthritis is common in patients undergoing RSA. [10] (10.1016/j.jseint.2021.11.008)
• [L3] Clinicians should consider overreduction of the AC joint because it may lead to favorable radiological results. [11] (10.1177/0363546519862850)
• [L4] The outcomes of this study seem to suggest that a distinction between symptomatic and asymptomatic radiographic AC OA is unnecessary, as all patients were equally satisfied with the outcome. [12] (10.5397/cise.2023.00073)
• [L1] Open and arthroscopic AC joint reconstruction techniques have no differences in loss of reduction, the complication rate, and the revision rate based on the available literature. [13] (10.1177/0363546518795147)
• [L3] [14] (10.1007/s00402-019-03258-9)
• [L4] Arthroscopic debridement of the AC joint can produce a favorable result in this difficult group of young patients presenting with isolated AC joint-related pain but with normal imaging. [15] (10.1097/bte.0b013e31816276cb)
• [L4] Limited distal clavicle excision of patients with AC joint osteoarthritis resistant to conservative treatment reduced pain and improved shoulder function at midterm follow-up. [17] (10.1016/j.otsr.2016.01.008)
• [L3] In this study the occurrence of AC joint osteoarthrosis was surprisingly frequent. [18] (10.1016/s1058-2746(96)80122-4)
• [L5] Anatomic techniques that address both coracoclavicular ligaments and the AC capsule are recommended to restore horizontal and vertical stability while allowing physiological rotation. [19] (10.1016/j.arthro.2019.01.038)
• [L4] Although the follow-up periods are less than 1 year, all patients are satisfied with their surgery and demonstrate good reduction of the AC joint on radiographs. [21] (10.1097/bte.0b013e31818a5dd9)
• [L4] The AC-DC measurement and use of the Alexander view provides the clinician with a more realistic appreciation of true AC joint displacement, especially in defining watershed cases (ie, IIIA/IIB/IV) and may better inform the decision-making process regarding management options and recommendations. [22] (10.1016/j.jse.2019.12.014)
• [L4] Additional research is needed to determine the main cause of pain and compare clinical outcomes of intra-articular versus extra-articular injections. [23] (10.5397/cise.2023.00311)
• [L4] Osteolytic changes seemed to be associated with incongruity of the AC joint, but did not correlate with clinical results. [24] (10.1016/0020-1383(83)90092-x)
• [L4] Osteoarthritis is associated with poorer final clinical outcomes, and an unhealed or re-torn cuff increases the risk of osteoarthritis. [26] (10.1016/j.otsr.2017.03.007)
• [L4] This procedure for an exact anatomical AC joint reconstruction shows good objective results with a high Constant and Rowe scores for shoulder function. [27] (10.1055/s-2008-1038577)
• [L4] The average angle from the central portion of the AC joint anteriorly was 6 degrees (range, 0 to 15 degrees). [29] (10.1097/bte.0000000000000033)
• [L3] [31] (10.1177/2325967119844295)
• [L4] AC injections offer a 1-year success rate of 47%. [33] (10.5397/cise.2023.00031)
• [L1] Preventive arthroscopic DCR is not recommended in patients with radiological but asymptomatic ACJ arthritis. [34] (10.1177/0363546514547254)
• [L4] This suggests that Type V AC dislocations may be given a trial of conservative therapy. [35] (10.1177/2325967115s00017)
• [L5] [36] (10.5435/00124635-199905000-00004)
• [L4] Conservative and surgical treatments are both effective in acromioclavicular joint osteoarthritis management. [38] (10.1007/s00167-020-06377-8)
• [L4] Most patients were ultimately treated surgically, although complications such as anterior shoulder pain, AC joint asymmetry, and activity-related weakness were common sequelae resulting in physical limitations and separation from military service. [43] (10.1177/03635465211036713)
• [L5] The technique offers advantages including decreased morbidity, less risk to the AC joint ligaments, and decreased loss and need for fluid. [44] (10.1016/j.eats.2021.12.006)
• [L4] Non-operative reduction and stabilization of high-grade AC joint separations seems to be a valuable treatment option. [45] (10.1007/s00402-020-03630-0)
• [L4] Ensuring good initial recovery of the CCD and precise placement of the AC joints was important in maintaining the proper AC position at the final follow-up. [46] (10.1016/j.arthro.2018.07.007)
• [L1] Evaluating the integrity of the capsuloligamentous structures stabilizing the AC joint is reproducible and gives additional information on the severity of the injury, which might also influence the treatment decision. [49] (10.1016/j.jse.2020.10.026)
• [L4] Severe chronic symptomatic AC joint separations (Rockwood types III through V) can be repaired entirely by arthroscopy safely and effectively by transferring the coracoacromial ligament with a bone block in the distal clavicle. [50] (10.1016/j.arthro.2009.08.008)
• [L5] [51] (10.1097/00132589-200603000-00004)
• [L4] Surgical management of AC joint injuries is associated with a relatively high complication profile and common loss of reduction, though the revision surgery rate is low. [53] (10.1016/j.jse.2023.03.019)
• [L4] [55] (10.1016/j.otsr.2010.10.004)
• [L4] Treatment of ACD by synthetic ligament reconstruction gave satisfactory results, notably in terms of recovery of strength, but evolution is not risk-free with onset of significant early osteolysis. [56] (10.1016/j.otsr.2010.06.004)
• [L5] The kinematic changes could be a potential source of pain and dysfunction in the shoulder with AC joint dislocation. [59] (10.1177/0363546512458571)
• [L5] Scapular and clavicular kinematics were affected in AC separation models. [60] (10.1016/j.jse.2013.01.004)
• [L4] [63] (10.1177/036354659302100113)
• [L4] Clinical symptoms and radiologic appearances are often poor indicators of the source of pain in the shoulder joint complex in patients with rheumatoid arthritis. [64] (10.1016/s1058-2746(09)80111-0)
• [L5] Combined stabilization of the AC capsule and CC ligaments demonstrated the greatest capacity to restore native stability against translational and rotational loads. [81] (10.1177/0363546518807908)
• [L5] In every CC loop repair, regardless of hole placement, complete AC joint congruity is not restored. [86] (10.1016/s1058-2746(03)00050-8)
• [L5] Given that more than 100 surgical stabilization techniques have been proposed for AC-joint injuries, a deeper understanding of the underlying anatomy, integrated with biomechanical evidence, may help to guide the development of a standardized, evidence-based approach to the treatment of AC-joint instability. [88] (10.2106/jbjs.25.01392)
• [L4] Patients with edema on MRI were more likely to present pain than patients without edema, and subchondral bone edema on histologic examination was more frequent in patients with pain. [92] (10.1016/j.jseint.2020.03.007)
• [L3] Early and delayed surgical interventions of high-grade AC joint dislocation provide equivalent clinical scores when combined CC and AC joint fixation is used for stabilization. [95] (10.1016/j.jse.2020.06.026)
• [L3] [101] (10.5397/cise.2023.00465)
• [L5] [112] (10.5435/jaaos-d-24-00360)
• [L4] [114] (10.1016/s1058-2746(96)80521-0)
• [L4] [115] (10.1016/s1058-2746(96)80520-9)
• [L4] [116] (10.1016/s1058-2746(96)80523-4)
• [L3] [117] (10.1016/s1058-2746(96)80522-2)
• [L4] [121] (10.1016/s1058-2746(10)80007-2)
• [L4] [122] (10.1302/2058-5241.3.170027)
• [L5] [123] (10.1016/s0278-5919(02)00102-3)

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