MR imaging of the intraarticular disk of the acromioclavicular joint: a comparison with anatomical, histological and in-vivo findings

Anatomical variants of the acromioclavicular joint influence its visibility in the standard MRI protocol in patients aged 18-31 years

Purpose

Visualization of a structure in orthogonal planes is essential for correct radiological assessment. The aim was to assess the utility of the standard MRI protocol for the shoulder in the assessment of the acromioclavicular joint (ACJ).

Methods

A total of 204 MRI scans of the shoulder were re-reviewed. Visibility of the ACJ in orthogonal planes was assessed, and the type of acromion and the angle between the ACJ and the glenoid cavity were assessed by two observers.

Results

Agreement in the assessment of ACJ visibility was moderate to substantial. The ACJ was visible in the three anatomical views in 48% (confidence interval [CI] 95% = [41–54%]) of the examinations, and no significant difference regarding gender or age was noticed. The mean angle between the ACJ and the glenoid cavity was 41.12 deg. CI95% = (39.72, 42.53) in the axial plane, 33.39 deg. CI95% = (31.33, 35.45) in the coronal plane and 52.49 deg. CI95% = (50.10, 54.86) in the sagittal plane. When the ACJ was visible in the sagittal and axial planes, significant differences were noticed in the remaining planes (p < .05).

Conclusion

Anatomical variations of the ACJ influence its visibility in the standard MRI protocol for examining the shoulder, making this protocol insufficient for ACJ assessment in the examined population.

The Morphology of the Acromioclavicular Joint Does Not Influence the Postoperative Outcome Following Acute Stabilization—A Case Series of 81 Patients

Purpose

To specifically evaluate the influence of the acromioclavicular (AC)-joint morphology on the outcome after arthroscopically assisted coracoclavicular (CC) stabilization surgery with suspensory fixation systems and to investigate whether an additional open AC-joint reduction and AC cerclage improves the clinical outcome for patients with certain morphologic AC-joint subtypes.

Methods

Patients with an acute acromioclavicular joint injury, who underwent arthroscopically assisted CC stabilization with suspensory fixation systems with or without concomitant AC cerclage between January 2009 and June 2017 were identified and included in this retrospective cohort analysis. AC-joint morphology was assessed on preoperative radiographs and categorized as “flat” or “non-flat” (“oblique”/“curved”) subtypes. After a minimum of 2 years of follow-up, postoperative Single Assessment Numeric Evaluation (SANE), American Shoulder and Elbow Surgeons (ASES), and visual analog scale (VAS) scores for pain were collected. A subgroup analysis of clinical outcomes depending on the surgical technique and morphological subtype of the AC joint was performed.

Results

Eighty-one patients (95% male, mean age 35 ± 12 years) could be included at a mean follow-up of 57 ± 14 months. Radiographic assessment of AC-joint morphology showed 24 (30%) cases of flat type, 38 (47%) cases of curved type, and 19 (23%) cases of oblique morphology. Postoperatively, no clinically significant difference could be detected after the treatment of AC joint injury via CC stabilization with or without concomitant AC cerclage (VAS_rest: P = .067; VAS_max: P = .144, ASES: P = .548; SANE: P = .045). No clinically significant differences were found between the surgical techniques for the flat morphologic subtype (VAS_rest: P = .820; VAS_max: P = .251; SANE: P = .104; ASES: P = .343) or the non-flat subtype (VAS_res: P = .021; VAS_max: P = .488; SANE: P = .243, ASES: P = .843).

Conclusions

In arthroscopically assisted AC stabilization surgery with suspensory fixation systems for acute AC-joint injury, the AC-joint morphology did not influence the postoperative outcome, independent of the surgical technique. No clinical benefit of performing an additional horizontal stabilization could be detected in our collective at mid-term follow-up.

Level of Evidence

Level IV, therapeutic case series.

Acromioclavicular Disk as a Potential Source of Pain in AC Joint Injuries

BACKGROUND

Injuries of the acromioclavicular joint (ACJ) are common shoulder injuries that often lead to pain and dysfunction of the affected shoulder. Regardless of operative or nonoperative treatment, a relatively large number of patients remain symptomatic and experience pain. However, the specific source of persistent pain in the ACJ remains ambiguous.

PURPOSE

To investigate the presence of sensory nerve fibers or pain-generating neurotransmitters within the intra-articular disk of the ACJ to determine its potential role as an independent pain generator in ACJ disorders.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twelve paired ACJs from 6 fresh human cadavers (mean age, 56 years; range, 41-82 years) were harvested and freed from surrounding soft tissues, leaving only the ACJ capsule intact. The specimens were placed in 4.5% formaldehyde fixative for a minimum of 48 hours. Coronal plane sections were obtained and demineralized in EDTA for a week, embedded in paraffin for 12 hours, and dehydrated overnight. With a rotation microtome, 2-μm sections were cut and stained with hematoxylin and eosin to investigate tissue architecture and confirm the presence of a fibrocartilaginous intra-articular disk. The sections were immunohistochemically stained with antisera against S100, neuropeptide Y (NPY), and substance P (SP) to detect for neural tissue. Additionally, a nerve fiber count per 10 high-power fields representing an area of 0.2 mm² was conducted for S100 stains. All sections were examined for the presence of positive immunoreactivity to S100, NPY, and SP.

RESULTS

The presence of a fibrocartilaginous intra-articular disk could be observed in all 12 examined ACJs. In all specimens, an immunoreactivity to S100, NPY, and SP could be observed within the superior peripheral region of the intra-articular disk. High-power field nerve counts of the S100 stains revealed a mean ± SD of 7.9 ± 2.28 nerves per 10 high-power fields (range, 4-12).

CONCLUSION

The documented immunoreactivity to S100, NPY, and SP indicates the presence of somatic and autonomic nerve fibers within the intra-articular disk of the ACJ.

CLINICAL RELEVANCE

Confirming the presence of nerve fibers within the intra-articular disk of the ACJ suggests that the disk itself could be an independent source of pain after injury and thus a possible explanation for recalcitrant pain after treatment.

Acromioclavicular Joint: What to Look for

Acromioclavicular joint (ACJ) pathology is a common source of shoulder girdle pain, frequently coexisting with and sharing overlapping clinical features of rotator cuff and glenohumeral articular lesions. ACJ trauma and osteoarthritis dominate clinical presentation; however, an array of pathologies can affect the joint. MR imaging of the ACJ is a powerful secondary diagnostic tool in early diagnosis of ACJ pathology and in accurate assessment of ACJ injuries, helping to resolve clinically challenging cases and allowing for individualized treatment planning. Knowledge of ACJ anatomy, biomechanics, and pathology is fundamental to interpreting and providing a clinically relevant ACJ MR imaging report.

Successful injection of the acromioclavicular joint with use of ultrasound: anatomy, technique, and follow-up

BACKGROUND

Injection into the acromioclavicular (AC) joint is often inaccurate (approximately 50%) even in experienced hands. In light of new anatomic observations, we evaluate accuracy of an innovative ultrasound-guided method and follow the clinical course of successful therapeutic injections.

METHOD

Relevant anatomy was investigated in 200 three-dimensional computed tomography scans, 100 magnetic resonance images, and 14 cadavers. Baseline measurements of joint depth and width were performed ultrasonically in 100 normal volunteers; 50 symptomatic patients were injected. Uniquely in a clinical ultrasound study, injection success was documented by arthrography. Outcomes after concomitant steroid instillation were observed for 6 months by visual analog scale (VAS) scores and pain provocation test results.

RESULTS

Anatomic studies showed that the widest area for joint penetration was anterior superior. Injection success rate was 96%, overwhelmingly on the first needle pass. Shallow joint depth allowed access with a standard 3-cm needle. Joint width diminished with age but did not reduce injection success. Cadaveric joints admitted 1.2 ± 0.5 mL, but fluid ingress was initially blocked by soft tissues in one third of both cadaveric and clinical cases. Diligent follow-up after steroid injection showed sustained pain relief in the majority with isolated AC disease but significantly less in those with concomitant shoulder disorders.

CONCLUSION

This high level of clinical injection success, irrefutably substantiated with arthrography, has not been previously demonstrated. The anterior superior aspect of the joint is the preferred place for entry. Initial intra-articular blockage to fluid inflow is common but can be surmounted. Encouraging 6-month results of steroid instillation in isolated AC disease do not apply to patients with coexisting shoulder pathologic processes.

Acromioclavicular joint instability: anatomy, biomechanics and evaluation

Acromioclavicular (AC) joint instability is a common source of pain and disability. The injury is most commonly a result of a direct impact to the AC joint. The AC joint is surrounded by a capsule and has an intra-articular synovium and an articular cartilage interface. An articular disc is usually present in the joint, but this varies in size and shape. The AC joint capsule is quite thin, but has considerable ligamentous support; there are four AC ligaments: superior, inferior, anterior and posterior. The coracoclavicular (CC) ligament complex consists of the conoid and trapezoid ligaments. They insert on the posteromedial and anterolateral region of the undersurface of the distal clavicle, respectively. The coracoid origin of the trapezoid covers the posterior half of the coracoid dorsum; the conoid origin is more posterior on the base of the coracoid. Several biomechanical studies showed that horizontal stability of the AC joint is mediated by the AC ligaments while vertical stability is mediated by the CC ligaments. The radiographic classification of AC joint injuries described by Rockwood includes six types: in type I injuries the AC ligaments are sprained, but the joint is intact; in type II injuries, the AC ligaments are torn, but the CC ligaments are intact; in type III injuries both the AC and the CC ligaments are torn; type IV injuries are characterized by complete dislocation with posterior displacement of the distal clavicle into or through the fascia of the trapezius; type V injuries are characterized by a greater degree of soft tissue damage; type VI injuries are inferior AC joint dislocations into a subacromial or subcoracoid position. The diagnosis of AC joint instability can be based on historical data, physical examination and imaging studies. The cross body adduction stress test has the greatest sensitivity, followed by the AC resisted extension test and the O'Brien test. Proper radiographic evaluation of the AC joint is necessary. The Zanca view is the most accurate view for examining the AC joint. The axial view of the shoulder is important in differentiating a type III AC joint injury from a type IV injury.

Acromioclavicular joint acceleration-deceleration injury as a cause of persistent shoulder pain: Outcome after arthroscopic resection

BACKGROUND

Shoulder pain in general and acromioclavicular joint (ACJ) pain specifically is common after acceleration-deceleration injury following road traffic accident (RTA). The outcome of surgical treatment in this condition is not described in the literature. The aim of the present study was to report the outcome of arthroscopic resection of the ACJ in these cases.

MATERIALS AND METHODS

Nine patients with localized ACJ pain, resistant to nonoperative treatment were referred on an average 18 months after the injury. There were 3 male and 6 females. The right shoulder was involved in seven patients and the left in two. The average age was 38.9 years (range 29-46 years). All presented with normal X-rays but with torn acromioclavicular joint disc and effusion on magnetic resonance imaging (MRI). Arthroscopic ACJ excision arthroplasty was performed in all patients.

RESULTS

At a mean followup of 18 month, all patients had marked improvement. The Constant score improved from 36 to 81, the pain score from 3/15 to 10/15 and the patient satisfaction improved from 3.5/10 to 9.3/10.

CONCLUSION

Arthroscopic ACJ excision arthroplasty, gives good outcomes in patients not responding to conservative management in ACJ acceleration-deceleration injury.

MRI versus radiography of acromioclavicular joint dislocation

OBJECTIVE

Acromioclavicular joint injuries are usually diagnosed by clinical and radiographic assessment with the Rockwood classification, which is crucial for treatment planning. In view of the implementation of MRI for visualization of the acromioclavicular joint, the purpose of this study was to describe the MRI findings of acromioclavicular joint dislocation in comparison with the radiographic findings.

SUBJECTS AND METHODS

Forty-four patients with suspected unilateral acromioclavicular joint dislocation after acute trauma were enrolled in this prospective study. All patients underwent digital radiography and 1-T MRI with a surface phased-array coil. MRI included coronal proton density-weighted turbo spin-echo and coronal 3D T1-weighted fast field-echo water-selective sequences. The Rockwood classification was used to assess acromioclavicular joint injuries at radiography and MRI. An adapted Rockwood classification was used for MRI evaluation of the acromioclavicular joint ligaments. The classifications of acromioclavicular joint dislocations diagnosed with radiography and MRI were compared.

RESULTS

Among 44 patients with Rockwood type I-IV injuries on radiographs, classification on radiographs and MR images was concordant in 23 (52.2%) patients. At MRI, the injury was reclassified to a less severe type in 16 (36.4%) patients and to a more severe type in five (11.4%) patients. Compared with the findings according to the original Rockwood system, with the adapted system that included MRI findings, additional ligamentous lesions were found in 11 (25%) patients.

CONCLUSION

In a considerable number of patients, the MRI findings change the Rockwood type determined with radiography. In addition to clinical assessment and radiography, MRI may yield important findings on ligaments that may influence management.

Dynamic radiologic evaluation of horizontal instability in acute acromioclavicular joint dislocations

BACKGROUND

Biplane radiologic evaluation is indispensable for the correct diagnosis of acute acromioclavicular (AC) joint injuries. Thus far, no functional radiographic techniques have been quantified to evaluate horizontal instability in acute AC joint dislocations.

HYPOTHESIS

Supine dynamic axillary lateral shoulder views detect horizontal instability of the distal clavicle in patients with acute AC joint dislocations.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 2.

METHODS

Twenty-five consecutive patients with a mean age of 39 +/- 14 years 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 degrees of abduction and 60 degrees 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.

RESULTS

Superior dislocation of the lateral clavicle in the Zanca view was classified as Rockwood type II in 7 patients, type III in 15, and type V in 3. The axillary lateral view in a sitting position showed posterior dislocation of the distal clavicle in 8 patients (Rockwood type IV injury). Dynamic radiologic evaluation revealed an average GACA difference between the neutral and anterior position of the arm of 7.1 degrees +/- 5.5 degrees for the unaffected shoulder. In the injured AC joints, 11 patients showed no radiologic evidence of horizontal instability (group A) with a GACA difference of 7.1 degrees +/- 4.8 degrees . Increased anteroposterior translation was evident in 14 patients (group B) with a GACA difference of 30.3 degrees +/- 14.3 degrees (P < .001).

CONCLUSION

Functional axillary radiologic evaluation seems to represent a simple imaging tool to reveal dynamic horizontal instability.

CLINICAL RELEVANCE

Horizontal instability of the distal clavicle in acute AC joint injuries represents an indication for surgical treatment. Dynamic axillary radiologic evaluation may detect previously missed unstable injuries. This evaluation might be relevant when deciding on surgical AC joint stabilization.

Prevalence of concomitant intraarticular lesions in patients treated operatively for high-grade acromioclavicular joint separations

The purpose of this study is to investigate the prevalence of concomitant intraarticular lesions to the glenohumeral joint or to surrounding soft tissue structures with non-randomized prospective case series. High-grade acromioclavicular (AC) joint dislocations result from direct or indirect force impact to the shoulder girdle. Fourty consecutive patients (2 female, 38 male) with high-grade acromioclavicular joint dislocations (Rockwood III: n = 3; IV: n = 3; V: n = 34) who underwent diagnostic arthroscopy at the time of acromioclavicular joint repair were evaluated. Associated pathologic lesions were documented and treated by an all-arthroscopic approach. As a result, traumatic intraarticular lesions were found in 15% (n = 6/40) of cases. Two patients had an isolated partial tear of the subscapularis tendon. One patient had a combined tear of the subscapularis and supraspinatus tendon (PASTA type lesion). Two patients showed a type II SLAP-lesion and one patient had a type VI SLAP-lesion. Arthroscopic treatment included rotator cuff reconstruction in two cases and debridement of the partially torn tendon in one case. Two patients underwent an arthroscopic SLAP-repair and in one patient a debridement of a labral flap tear was performed. Acromioclavicular joint reconstruction was achieved via an open technique using suture anchors in 14 cases and via an all-arthroscopic approach using a double Tight-rope technique in 26 cases. To conclude, in number of cases, high-grade AC-separations may be associated with traumatic concomitant glenohumeral pathologies resulting from the same trauma impact to the shoulder girdle. A combined or an all-arthroscopic approach allows to accurately diagnose and treat associated intraarticular pathologies.

MR imaging appearances of acromioclavicular joint dislocation

The key structures involved in dislocation of the acromioclavicular joint (ACJ) are the joint itself and the strong accessory coracoclavicular ligament. ACJ dislocations are classified with the Rockwood system, which comprises six grades of injury. Treatment planning requires accurate grading of the ACJ disruption, but correct classification can be difficult with clinical assessment. Magnetic resonance (MR) imaging has a well-established role in evaluation of ACJ pain. MR imaging performed in the coronal oblique plane parallel to the distal clavicle allows assessment of the acromioclavicular and coracoclavicular ligaments owing to its in-plane orientation in relation to these structures. This technique enables distinction between grade 2 and grade 3 injuries, which can be difficult with conventional clinical and radiographic evaluation. In addition, diagnosis of grade 1 injuries is possible by demonstration of a ruptured superiodorsal acromioclavicular ligament. Resultant thickening of the acromioclavicular or coracoclavicular ligament allows identification of chronic ACJ injuries.