New quantitative radiographic parameters for vertical and horizontal instability in acromioclavicular joint dislocations

Abstract

PurposeThe aim of this study was to identify the most accurate and reliable quantitative radiographic parameters for assessing vertical and horizontal instability in different Rockwood grades of acromioclavicular joint (ACJ) separations. Furthermore, the effect of projectional variation on these parameters was investigated in obtaining lateral Alexander view radiographs.MethodsA Sawbone model of a scapula with clavicle was mounted on a holding device, and acromioclavicular dislocations as per the Rockwood classification system were simulated with the addition of horizontal posterior displacement. Projectional variations for each injury type were performed by tilting/rotating the Sawbone construct in the coronal, sagittal or axial plane. Radiographic imaging in the form of an anterior–posterior Zanca view and a lateral Alexander view were taken 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 were measured. Reliability, validity and the effect of projectional variation were investigated for these radiographic measurements.ResultsAll 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. The effect of projectional variation increased with the degree of deviation and was maximal (3 mm) for AC–DC in 20° anteverted malpositioning and for GC–PC in 20° retroverted malpositioning.ConclusionsAC–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 dislocations, may improve management of these controversial injuries.

High degree of consensus achieved regarding diagnosis and treatment of acromioclavicular joint instability among ESA-ESSKA members

“…Since clinical data has shown a vast number of persistent horizontal instability following modern arthroscopic AC joint reconstruction techniques [23,24], not only the surgical management but also the clinical assessment have been reconsidered. It has been claimed that parameters assessable on AP and Zanca view do not allow for quantification of horizontal instability, therefore, the use of new radiographic parameters in a single lateral Alexander view has been recently recommended [15,29]. Anyhow, the ESA panel agreed that a true AP view or a bilateral Zanca view without loading the arm are still adequate for a correct diagnosis, with no need of modified Alexander view to seek for horizontal instability.…”

Improved identification of unstable acromioclavicular joint injuries in a clinical population using the acromial center line to dorsal clavicle radiographic measurement

“…15,19 In a previously published in vitro study, we demonstrated that the measured AC-DC distance in lateral Alexander views showed excellent interobserver reliability, as well as higher correlation with CT-measured vertical displacement, when compared with the CC distance. 20 An omission from that study was assessment of the accuracy of AC-DC in measuring the total AC joint displacement, that is, the vector magnitude of combined vertical and horizontal displacement. Although AC-DC showed excellent correlation with CT-measured vertical displacement, while allowing for 20 of variation in projection in 3 dimensions (r ¼ 0.939), further analysis of the data since that publication demonstrated even higher correlation between AC-DC and the total vector of displacement (r ¼ 0.972).…”

“…1). 20 The CC distance was measured from the top of the coracoid to the undersurface of the distal clavicle on AP Zanca views, whereas the AC-DC was measured from the middle acromial axis to the dorsal clavicle surface on the lateral Alexander views. All measurements were obtained using picture archiving and communication software (PACS) and presented in millimeters as the difference between the unaffected and injured shoulders.…”

“…The AC-DC measurement was originally designed to evaluate superior displacement of the distal clavicle from a lateral view and has been shown to tolerate projectional variation well in terms of effect on measurement accuracy. 20 The aim of the current study was to evaluate AC joint displacement at the time of presentation in a series of clinical cases by comparison of both the CC distance and the newly proposed AC-DC distance in addition to their relationship with Rockwood grade.…”

Verletzungen des Akromioklavikulargelenks

“…Einen quantitativen Ansatz der Bestimmung von vertikaler und horizontaler Instabilität an einer isolierten Alexander-Aufnahme haben Zumstein et al [39] vorgestellt. Als völlig neue Messparameter wurden dabei für die vertikale Instabilität die Distanz der "acromion centre line to dorsal clavicle" (AC-DC)…”