Multidetector CT arthrography in shoulder instability and its comparison with MR arthrography and arthroscopy

INTRODUCTION

Shoulder instability is a common problem with annual incidence between 0.084%-1.7%.¹ There are 46%-100% incidence of recurrent dislocation for patients aged less than 40 years without surgical intervention, which decreases to 7%-15% after surgical stablization.¹ To improve the pre-operative planning and post-operative result of surgery, exact diagnosis of pathology and anatomy of labroligamentous structure is essential.

Conventional computerized tomographic arthrography (CTA) has limited soft tissue contrast and spatial resolution which has led to it being replaced by conventional and contrast enhanced magnetic resonance imaging (MRI) of shoulder.^2-6 At present, magnetic resonance arthrography (MRA) of shoulder is well proven and useful technique for diagnosis of intra-articular lesions.^5,11 However it is still expensive and metal in the vicinity interferes with the true signal.

Since multidetector CT (MDCT) was introduced in 1988, cross-sectional imaging has been revolutionized by the capacity for routine acquisition of substantial anatomic volumes with an isotropic sub-millimeter spatial resolution and scan times of less than 10 seconds for 300 mm of coverage.^5,7-9 The use of MDCTA as a diagnostic method in various joints, including the shoulder, has been reported.^2,10-14

The purpose of this study was to determine the utility of MDCTA in evaluation of lesions associated with shoulder instability and its comparison with MRA and arthroscopy, taking arthroscopy as gold standard. We hypothesized that MDCTA would be cost effective and comparable with MRA for assessing lesions in shoulder instability.

METHODS

It was a cross sectional study. The study was approved by the institutional ethical committee and conducted in the period from August 2012 to April 2014. Written informed consent was obtained from all patients. 20 consecutive patients with symptomatic shoulder instability were included in the study group. Patients with history of previous shoulder surgery, shoulder sepsis, any fracture and time delay between imaging and arthroscopy longer than 6 weeks were excluded. All patients underwent MDCTA and MRA after a single injection of contrast media under fluoroscopic control. Contrast media mixture used was 25% iodinated contrast media (Iomeron 250) and 1.25 mmol/L gadolinium contrast media (Dotarem 0.5 mmol/ml diluted to 1/400 dilution).¹² 12-20 ml of this combined contrast media was injected followed by MDCTA and MRA.

MDCTA was performed using 128 slice CT scan (Seimens, Forchheim, Germany) in axial, oblique coronal, sagittal coronal plane with 3mm section thickness. Oblique coronal images were reconstructed parallel to supraspinatus muscle and oblique sagittal images parallel to joint surface of glenoid with an identical section thickness and reconstruction interval.

MRA was performed on 1.5 T System (Seimens, Forchheim, Germany). Fat suppressed T1-wiegted spin echo images were obtained in transverse plane, in oblique coronal and oblique sagittal plane.

MDCTA and MRA were blinded and randomly evaluated in consensus by two musculoskeletal radiologists with more than 5 years of experience. The different lesions found in shoulder instability were assessed independently on each imaging modality.

H- Humeral head, G- Glenoid, L- Labrum.

All patients were subsequently underwent arthroscopic examination of shoulder within 6 weeks of the radiographic study. The lesions identified during arthroscopy were noted for the comparison with the findings in MDCTA and MRA (Figure 1 to 3).

Considering the arthroscopic findings as gold standard; sensitivity, specificity, positive predictive value (PPV) and negative productive value (NPV) were calculated. Agreement was calculated between each imaging modality and arthroscopy using kappa coefficient (к) as follows: 0-poor agreement, 0.01-0.20- slight agreement, 0.21-0.40-fair agreement, 0.41-0.60-moderate agreement, 0.61-0.80- substantial agreement, 0.81-1.00-almost perfect agreement.

Cohen’s Kappa coefficient is a statistic tool which measures inter-rater agreement for qualitative (categorical) items.

RESULTS

Out of 20 patients in the study group, 16 were males and the rest 4 were females. Four patients were professional sports persons, 6 were body building professionals, and the rest 10 were not involved in any heavy physical or sports activity (Table 1). All patients had history of trauma either during sports, weight lifting or fall as a cause of shoulder dislocation. Three patients had more than 10 dislocations, 4 patients had 5-10 episodes, 7 patients had 4 episodes of dislocation and six patients had 3 episodes of dislocation. Two patients (one had more than 10 times dislocation and other had 5 times dislocation) gave history of dislocation during sleep. 16 patients were presented after 6 months but within a year. There was a patient who presented with 11 year of shoulder pain and history of dislocation.

At arthroscopy, 10 Bankart’s lesions, 7 Hill Sach’s lesion, 6 SLAP lesions, 1 ALPSA, 1 capsular laxity, 1 partial subscapularis tear and 1 supraspinatus fraying was seen. Lesions detected by MRA and MDCTA were noted in Table 2. Diagnostic efficacy of both imaging modality were excellent in detecting labral lesions. Sensitivity, specificity, positive predictive value and negative predictive value were same for SLAP lesions and ALPSA lesions and comparable for Bankart’s and Hill Sachs lesions. The agreement of MDCTA and MRA with arthroscopic correlation was 0.60 and 0.55 respectively which was moderate agreement (Table 3 and 4).

*Lesions were not included in these studies.

Kappa coefficient (к) 0-Poor agreement, 0.01-0.20- Slight agreement, 0.21-0.40- Fair agreement, 0.41-0.60- Moderate agreement, 0.61-0.80- Substantial agreement, 0.81-1.00- almost perfect agreement.

DISCUSSION

In shoulder instability and pain during throwing, diagnosis of pathology and knowledge of its exact anatomy is crucial for proper preoperative planning and treatment. History taking, physical examination and plain radiograph are usually sufficient for the diagnosis of instability, but to know exact causative lesion higher imaging modalities are often necessary.

MRI has been widely used for definitive diagnosis and preoperative assessment because of its inherent soft tissue contrast, oblique plane imaging capability and excellent resolution using surface coil. If contrast media is used along with MRI then diagnostic efficacy is increased due to filling of contrast media in the defects. So, the MRA is being used as imaging modality of choice in intra-articular derangement of shoulder joint. However MRI has following limitations; cost factor, time consuming, claustrophobic in some patients, and altered signals in presence of metal in vicinity.

CT shows high accuracy for detecting bony lesions. MDCTA has the advantages of isotropic sub millimeter spatial resolution, reduced examination time with decreased motion artifacts, imaging in abduction external rotation (ABER) position even when apprehension test is positive, possibility of reconstruction images with 1mm or thinner section in any direction, cost effectiveness, and can be useful even if metal is in vicinity.

In previously published studies by Oh et al, Acid et al and Mahmoud et al also have shown efficacy of MDCTA in diagnosing pathologies in shoulder instability.^1,15,16 The outcomes of these studies in comparison to ours in Table 5 and 6.

The study has following strength. It demonstrates the possibility of performing a one shot MDCTA-MRA of shoulder using mixture of iodinated and paramagnetic contrast agent. The MDCTA-MRA examination did not create any particular problem in performing or reading of images. By performing one shot MDCTA-MRA, we were able to compare the effectiveness of two imaging modalities simultaneously in the same patient. These were compared with arthroscopic findings and diagnostic efficacy of each imaging modality was demonstrated.

This study has the following limitations. First, although arthroscopy is supposed to be the best reference standard used in this study, it remains an operator dependent method. Second, because the decision to perform arthroscopy was based not only on clinical symptoms but also on preoperative imaging findings, a verification bias might have been introduced. Third, because all MDCTA and MRA examinations were analyzed by two radiologists in consensus, inter-observer variation was not studied. Fourth, although sample size was based on the sensitivity and specificity shown in previous studies, the number of each elemental lesion was too small to allow further statistical analysis. Fifth, mixed contrast material was used in this study. The stability of the mixture of gadolinium chelates and iodinated contrast agents has already been reported on, and its clinical safety was certain for performing CTA and MRA of the ankle and wrist as a one-shot CTA- MRA examination. Nevertheless, a decrease in the signal intensity on MRA was seen due to the dilution of the gadolinium chelate mixed with the iodinated contrast agent. This might have reduced the sensitivity of MRA for Bankart’s variants in this study, as compared to previous studies.

CONCLUSION

In shoulder instability and pain in activity, both MRA and MDCTA demonstrate the labroligamentous lesions effectively. Although soft tissue lesions were better picked by MRA and bony lesions by CTA, both modality show moderate agreement (к for MDCTA is 0.55 and for MRA it is 0.60) when compared with arthroscopy.

Considering availability, cost, time consumption, superiority in detecting bony lesions and comparable in soft tissue lesions detection MDCTA can be used as single investigation of choice in shoulder instability.

ACKNOWLEDGEMENTS

Lodhi Jeetendra selected the patients, examined them, injected contrast agents for MDCTA and MRA, worked them up for arthroscopy and prepared the manuscript. Sabat Dhananjay helped in editing the manuscript. Kumar Vinod gave concepts of study, designed the study and performed diagnostic arthroscopy in all patients. Sehrawat Rakesh and Gupta Deepak helped in statistical analysis of data.

We sincerely thank to Dr. Pradhan Gaurav and Dr. Singh Sapna from department of Radiology who helped in interpreting the MDCTA and MRA images.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the institutional ethics committee

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