Tauber, et al., Dynamic Radiologic Evaluation of Horizontal Instability in Acute Acromioclavicular Joint Dislocations, AJSM 2010

  • Methods:
    • Cohort Study, Level II:
    • Twenty-five consecutive patients, mean age of 39years with acute AC joint injury underwent biplane radiologic evaluation, including a conventional Zanca view and an axillary lateral view in a sitting position.
    • In addition, supine axillary lateral views with the arm in 90° of abduction and 60° of flexion and extension were taken to evaluate the horizontal dynamics of the distal clavicle.
    • The gleno-acromio-clavicular angle (GACA) was introduced and used to quantify the horizontal clavicular dynamics in terms of angle differences. The unaffected shoulders served as the control group.
    • Inclusion criteria:
      • (1) AC joint injury within 7 days, (2) no previous injuries or surgical procedures of the affected shoulder, (3) no AC joint injuries of the contralateral shoulder, and (4) no deforming musculoskeletal or neurologic disorders involving the shoulder girdle
  • Results:
    • An attempt to establish a classification system and to develop a simple, practical, and available imaging tool to diagnose horizontal AC joint instability. The next reason- able step is the implementation of these radiologic findings into a therapeutic process. This technique could be used to identify patients who need surgical treatment. Further- more, this technique can reveal dynamic horizontal AC instability independent of the grade of superior dislocation of the distal clavicle in the coronal plane.
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 Vaisman, et al.: A Novel Radiographic Index for the Diagnosis of Posterior Acromioclavicular Joint Dislocations, AJSM 2013

  • Methods:
    • Cohort Study, Level II: analytic, descriptive study
    • 150 patients with different grades of AC injuries, Rockwood classification (30 patients for each grade of injury: I, II, III, IV, and V).
      The diagnosis of an AC injury was made both clinically and radiographically by using comparative Zanca and axillary views. Two measurements were performed in Zanca views: the cora- coclavicular distance and the AC width distance. A width index was calculated for each patient. The Student t test, Bonferroni test, logistic regression, linear regression, and receiver operating characteristic (ROC) curves were used for statistical analysis. Forty cases were impartially selected to obtain a k concordance value.
    • Inclusion criteria:
      • Adult patients (aged 􏰁18 years) with a recent unilateral AC traumatic event who arrived at the emergency room and underwent complete and standardized radiographic assessments.
    • Exclusion criteria:
      • Patients with a degenerative disease of the AC joint or associated acromion, coracoid, or clavicle fractures, or a previous AC joint surgery
  • Results:
    • There was a significant difference between the average width index in the patients with type IV injuries and those in the remaining groups (P \ .05). The ROC curve showed that a width index of 60% has a sensitivity of 95.7% and specificity of 97.5%, with a positive predictive value of 96.7% and negative predictive value of 95.6% to predict a type IV injury. Intraobserver reliability was rated as substantial agreement for each of 3 observers; the inter- observer reliability of the 3 independent raters was almost perfect.
  • Conclusion:
    • Introducing AC-Index
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Melenevsky, et al.: Clavicle and acromioclavicular joint injuries: a review of imaging, treatment, and complications , Skeletal Radiology 2011

  • Methods: Review
  • Results:
    • Simultaneous bilateral AP views provide reference for normal AC and CC distances in uninjured shoulders.
    • Lateral and axial views beneficial in diagnosis of posterior clavicle dislocation.
    • Bilateral Zanca views (beam directed 10 cephalad toward AC joint) and cross-arm adduction AP views can be performed.
    • Weighted views of AC joint may unmask difference between type II and III injuries. Traditionally, performed by comparing views of AC joint with and without a 10 pound weight affixed to the patient’s ipsilateral wrist. However, these are controversial and fall into disfavor because uncomfortable for the patient and add no new information to clinical examination.
    • Growing interest using MRI to delineate AC and CC ligamentous disruption and degree of concomitant soft tissue injury with AC joint separations. MRI very useful in classifying the types of AC joint injury preferentially to radiography as coracoclavicular ligaments can be directly visualized on MRI, whereas their integrity is only inferred on radiography. MRI also useful to characterize postoperative changes and to distinguish degenerative changes from acute injury. A specialized coronal plane of imaging parallel to the anterior acromion has been described.
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Zumstein, et al.: New quantitative radiographic parameters for vertical and horizontal instability in acromioclavicular joint dislocations , KSSTA 2017

  • Methods:
    • Sawbone scapula/clavicle model. ACJ dislocations per Rockwood simulated with addition of horizontal posterior displacement. Performed projectional variations for each injury type. Radiographic imaging anterior–posterior Zanca view and lateral Alexander view for each injury type and each projectional variation.
      Five newly defined radiographic parameters for assessing horizontal and vertical displacement as well as commonly used coracoclavicular distance view measured. Reliability, validity and the effect of projectional variation investigated for these radiographic measurements.
  • Results:
    • All radiographic parameters showed excellent intra- and interobserver reliability.
    • The validity was excellent for the acromial centre line to dorsal clavicle (AC–DC) in vertical displacement and for the glenoid centre line to posterior clavicle (GC–PC) in horizontal displacement, whilst the remaining measurements showed moderate validity.
    • For AC–DC and GC–PC, convergent validity expressed strong correlation to the effective distance and discriminant validity demonstrated its ability to differentiate between various grades of ACJ dislocations.
    • Effect of projectional variation increased with degree of deviation and was maximal (3 mm) for AC–DC in 20° anteverted malpositioning and for GC–PC in 20° ret- roverted malpositioning.
  • Conclusion:
    • AC–DC and the GC–PC are two novel quantitative radiographic parameters of vertical and horizontal instability in ACJ dislocations that demonstrate excellent reliability and validity with reasonable inertness to malpositioning.
    • The use of AC–DC for assessing vertical displacement and GC–PC for assessing horizontal displacement in a single Alexander view is recommended to guide the appropriate management of ACJ dislocations.
    • A better appreciation of the degree of horizontal instability, especially in lower Rockwood grades (II, III) of ACJ dis- locations, may improve management of these controversial injuries.
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Ibrahim, et al.: Bilateral weighted radiographs are required for accurate classification of acromioclavicular separation: An observational study of 59 cases , Injury 2015

  • Methods: Observational:
    • Complete bilateral non-weighted and weighted sets of radiographs for patients presenting with an acromioclavicular separation over a 10-year period were analysed retrospectively, and they were graded I–VI according to Rockwood’s criteria. Comparison was made between grading based on (1) a single antero-posterior (AP) view of the injured side, (2) bilateral non-weighted views and (3) bilateral weighted views. Radiographic measurements for cases that changed grade after weighted views were statistically compared to see if this could have been predicted beforehand.
  • Results:
    • Weighted bilateral views needed
  • Conclusion:
    • The accurate classification of ACJ separation requires weighted bilateral comparative views. Attempts to predict grade on a single AP radiograph result in a gross underestimation of severity. The value of bilateral weighted views is to ‘unmask’ a grade V injury, and it is recommended as a first-line investigation.
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Kim, et al., Acromioclavicular joint injuries and reconstructions: a review of expected imaging findings and potential complications, Emerg Radiol 2012

  • Results:
    • The AC joints should ideally be imaged bilaterally, even when unilateral injury is suspected. This is due to the natural anatomic variation inherent to this joint, requiring the opposite side for comparison An AP view of the AC joints with or without cephalic tube angulation serves as the standard for initial imaging. While a straight AP view allows for more anatomical positioning of the joint, angulat- ing the tube in a cephalic direction does have the advantage of projecting the AC joint with increased separation from the proximal aspect of the acromion. On occasion, it may be helpful to further exaggerate the suspected separation by utilizing other views. To this end, a weight-bearing or stress view is utilized at some institutions, including our own, to help differentiate between grades of injury. In particular, this view is thought to be helpful in differentiating between grade 2 and 3 separations. It may also be useful in ascertaining whether or not a separation truly exists. However, the ultimate utility of the weight- bearing view is somewhat controversial. Another view that can be useful is a Zanca view (Fig. 4). In order to obtain a Zanca view, the X-ray tube is centered at the AC joint with a 10–15 ° cephalic tilt. The standard kilovoltage is also decreased up to 50 % in order to better visualize the soft tissues and to increase joint detail [10]. If there is continued suspicion for an AC joint separation, but the separation remains poorly demonstrated on the standard views, additional stress views while placing the patient’s arm on the affected side in a variety of positions may help accentuate the separation. Advanced methods for imaging the AC joint include CT and MRI. CT image acquisition is generally straightforward as imaging in the transaxial plane utilizing bone and soft tissue windows can be reconstructed in the sagittal and coronal planes. In addition, 3D volume rendering can be helpful in difficult cases to improve visualization of the degree and trajectory of bony displacement. Furthermore, CT may better demonstrate subtle fractures, which can be missed on the plain radiographs. However, while subtle fractures may be more readily apparent on CT, the findings compatible with AC joint separation are similar to those of plain film radiography but with the disadvantage of a much larger radiation dose to the patient. In general, CT is best reserved for cases in which there is a higher index of suspicion for a fracture rather than an AC separation. MRI is an ideal imaging modality for soft tissue evaluation, especially ligamentous injury. As a supplement, administration of intravenous gadolinium can further assist in depicting the path and full extent of soft tissue injury in fine detail. has been suggested that patients with more advanced degrees of injury requiring surgical reconstruction may ben- efit from having an MRI performed prior to surgery to define the full extent of injury, though the role of MRI in AC separations is not clearly defined [9]. Overall, MRI provides incomparable detail of the anatomy of the soft tissues surrounding the AC articulation. As a caveat regard- ing both CT and MR imaging, it is important to remember that the study is acquired with the patient in a recumbent position. Thus, the relative positions of the clavicle and acromion may be altered, particularly in less severe injuries. Furthermore, the advantage of gravitational assistance gar- nered from having the patient in an upright position when acquiring radiographs is lost, which again may mask the true extent of separation.
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Gastaud, et al.: Reliability of radiographic measurements for acromioclavicular joint separations, Orthopaedics & Traumatology: Surgery & Research 2015

  • Methods:
    • prospective radiographic study using protocol-based data from the 2014 symposium of the French Society of Arthroscopy (SFA). Fifteen anonymized radiological records were analysed by six independent examiners on two occasions, 1 week apart. The records consisted of a comparative A/P view of the two acromioclavicular joints (Zanca view), an axillary lateral view and dynamic lateral views (Tauber protocol) to uncover dynamic horizontal instability. A detailed analysis protocol was implemented that included absolute and relative measurements on each view; the relative measurements were used to account for radiographic magnification.
  • Radiographs:
    • Bilateral Zanca / AX (Bernagou/Patte) / dynamic axillary lateral radiographs with the arm in 0◦ and 60◦ forward flexion
  • Results:
    • The inter- and intra-observer reproducibility on the A/P radiographs was good to excellent. The reproducibility was fair to good on the lateral views, but the measurements varied greatly from one subject to another, and significant errors were found with certain records. The reproducibility of the dynamic views proposed by Tauber was poor to fair.
  • Conclusion:
    • Radiographic analysis of AC joint separations is reproducible in the vertical plane, which makes it possible to diagnose Rockwood type II, III and V injuries. On the other hand, static and dynamic analyses in the horizontal plane do not have good reproducibility and do not contribute to make an accurate diagnosis of Rockwood type IV injuries.
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Mazocca, et al.: Evaluation and Treatment of Acromioclavicular Joint Injuries, AJSM 2007

  • Methods:
    • Review
  • Results:
    • Anteroposterior, lateral, and axial views are standard views taken for the shoulder; however, a Zanca view is the most accurate view to look at the AC joint. This view is performed by tilting the x-ray beam 10° to 15° toward the cephalic direction and using only 50% of the standard shoulder anteroposterior penetration strength (Figure 2). The axial view of the shoulder is important in differenti- ating a type III AC joint injury from a type IV injury. Visualization of the scapula anterior to the clavicle will indicate a type IV lesion. When there is a normal coraco- clavicular interspace but a complete dislocation of the AC joint, a coracoid fracture should be suspected. A Stryker notch view is helpful in diagnosing this condition.
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Beitzel, et al.: ISAKOS Upper Extremity Committee Consensus Statement on the Need for Diversification of the Rockwood Classification for Acromioclavicular Joint Injuries , Arthroscopy 2014

  • Methods:
    • Scientific Committee Report
  • Results:
    • Clinical decision making is often a process based solely on 2-dimensional and static anteroposterior (AP) radio- graphic views without specific guidelines relating to radiographic technique. posterior subluxation of the clavicle into the trapezius. Currently, this is thought to be best seen on axillary radiographs. This technique, however, does not safely allow for 3- dimensional and functional evaluation of this lesion. Radiographic evaluation should include a bilateral Zanca view, which visualizes the ipsilateral and contra- lateral AC joints on a single x-ray cassette while main- taining the same orientation of the x-ray beam (Fig 1).6 The view is obtained by tilting the x-ray beam 10 to 15 toward the cephalic direction and using only 50% of the standard shoulder AP penetration strength. By visual- izing both AC joints on the same cassette, the CC distance can be compared from side to side, also allowing for future comparison of preoperative and postoperative examination findings. An axillary view is particularly helpful in visualizing a type IV AC joint injury that results in an anteromedial displacement of the scapula because radiographic analysis will allow for visualization of a posteriorly displaced distal clavicle in relation to the acromion. The Stryker notch view is useful for determining a coracoid fracture in a complete AC dislocation with normal CC interspace. Coracoid process fracture should be suspected when radiographs show AC dislocations with a normal CC distance.
      According to our recommendations, additional radio- graphs should be taken to allow for differentiation between clinically relevant stable and unstable AC joint injuries. Because these findings are more associated with functional problems, the diagnostic imaging should take these into account and try to objectively evaluate the function of the AC joint.
  • Conclusion:
    • New addition to Rockwood: III A / B added: Grade IIIA injuries would be defined by a stable AC joint without overriding of the clavicle on the cross-body adduction view and without significant scapular dysfunction. The unstable grade IIIB injury would be further defined by therapy-resistant scapular dysfunction and an overriding clavicle on the cross-body adduction view.
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