Magnetic resonance imaging of shoulder arthroplasty: review article

Imaging in shoulder arthroplasty: Current applications and future perspectives

Shoulder arthroplasty has become a standard surgical procedure for treating a variety of complex shoulder disorders, including those with degenerative and traumatic aetiologies. The ever-improving success rates of shoulder arthroplasty could be attributed to advancements in endoprosthesis design, improvements in the biomechanics of endoprosthetic components, and improvements in surgical techniques. It improves patient outcomes and helps restore shoulder joint function and mobility. Imaging plays a vital role by enabling surgeons to plan arthroplasty procedures, help guide endoprosthesis placement, and monitor postoperative outcomes. In addition, imaging plays a role in assessing the residual bone stock and status of rotator cuff integrity and in correcting the placement of prosthetic components to restore shoulder mobility. CT-guided navigation aids surgeons by helping them choose appropriate components for implants and ensuring that implants are placed optimally during surgery. It can lead to better surgical results with reduced patient morbidity and a longer duration of prosthetic stability. After surgery, it is crucial to use imaging techniques to detect issues such as periprosthetic loosening, infections, or fractures to start effective management strategies to enhance patient recovery. This article aims to provide orthopaedic surgeons and radiologists with knowledge on the imaging methods used in shoulder arthroplasty and their role in presurgical planning, intraoperative guidance and postoperative assessment. In this study, we aimed to investigate the rationale behind utilising various types of shoulder replacements: total shoulder replacement (TSA), reverse total shoulder arthroplasty (RTSA), and hemiarthroplasty; methods, their respective advantages and limitations; and outcomes. Our objective is to comprehensively analyse the procedures mentioned above and highlight their unique features and benefits to facilitate a better understanding of these approaches. Additionally, we will discuss how these imaging techniques help identify issues such as loose components, fractures around the implant site, joint instability and infections.

No difference in complications between two-week vs. six-week duration of sling immobilization after reverse total shoulder arthroplasty

Background

The purpose of our study was to compare the outcomes and complications after a two- vs. six-week duration of sling immobilization following reverse total shoulder arthroplasty (rTSA).

Methods

We conducted a retrospective review from our institutional database on 960 patients treated by primary rTSA between 2011 and 2021. Patients were separated into two cohorts of postoperative sling immobilization (a two-week and six-week group). Multivariate analysis was conducted to evaluate what factors were associated with patients experiencing either a postoperative complication or requiring reoperation.

Results

A total of 276 patients were instructed to keep their operative arm in a sling for six weeks postoperatively, and 684 patients discontinued use at two weeks. There was no difference in postoperative complication rate (15.0% vs. 12.0%, P = .21), dislocation rate (P = .79), acromion stress fractures (P = .06), implant loosening (P = .15), and periprosthetic joint infections (P = .48) between the six- and two-week sling cohorts. In the immediate 90-day postoperative time period, no difference was seen in the reoperation rates (P = .73).

Discussion

Shorter duration of sling immobilization (two weeks) does not incur additional risk of complications compared to standard duration (six weeks) of sling immobilization following rTSA.

Reliability and validity of a new deltoid muscle area measurement method after reverse shoulder arthroplasty

Background

Accurate deltoid muscle assessment after reverse shoulder arthroplasty (RSA) is difficult using magnetic resonance imaging due to metal artifacts. We hypothesized that measuring the deltoid muscle area (DA) in the middle part of the deltoid's total length postoperatively would reduce metal artifacts and allow for an accurate assessment. This study aimed to assess the reliability and reproducibility of magnetic resonance imaging and evaluate its impact on postoperative outcomes.

Methods

The DA in the middle part of the muscle's total length was measured twice by four examiners using pre and postoperative magnetic resonance imaging in 60 patients who underwent RSA (22 men, 38 women; mean age: 77.4 years). The DA at the greater tuberosity was measured preoperatively, and its correlation with the middle part of the deltoid's total length was evaluated. The Constant-Murley Score was measured at 2 years postoperatively, and its correlation with the DA in the middle part of the deltoid's total length pre- and postoperatively was assessed.

Results

Intraclass correlation coefficients for intraobserver measurements of preoperative and postoperative DA in the middle part of the deltoid's total length were almost perfect, with mean values of 0.98 and 0.97, respectively. The intraclass correlation coefficients for interobserver reliability regarding the first and second DA measurements in the middle part of the deltoid's total length were 0.95 and 0.95 (preoperatively) and 0.89 and 0.90 (postoperatively). The Constant-Murley Score was assessed at 2 years postoperatively in 51 patients. Muscle strength was weakly and moderately correlated with preoperative DA (r = 0.33, P = .02) and postoperative DA (r = 0.49, P < .01), respectively.

Conclusion

DA measurement in the middle part of the deltoid's total length after RSA was not affected by metal artifacts and had excellent reproducibility. This measurement method positively correlated with postoperative muscle strength, suggesting its usefulness for predicting postoperative muscle strength.

Diagnostic Performance of Advanced Metal Artifact Reduction MRI for Periprosthetic Shoulder Infection

BACKGROUND

The diagnosis of periprosthetic shoulder infection (PSI) in patients with a painful arthroplasty is challenging. Magnetic resonance imaging (MRI) may be helpful, but shoulder implant-induced metal artifacts degrade conventional MRI. Advanced metal artifact reduction (MARS) improves the visibility of periprosthetic bone and soft tissues. The purpose of our study was to determine the reliability, repeatability, and diagnostic performance of advanced MARS-MRI findings for diagnosing PSI.

METHODS

Between January 2015 and December 2019, we enrolled consecutive patients suspected of having PSI at our academic hospital. All 89 participants had at least 1-year clinical follow-up and underwent standardized clinical, radiographic, and laboratory evaluations and advanced MARS-MRI. Two fellowship-trained musculoskeletal radiologists retrospectively evaluated the advanced MARS-MRI studies for findings associated with PSI in a blinded and independent fashion. Both readers repeated their evaluations after a 2-month interval. Interreader reliability and intrareader repeatability were assessed with κ coefficients. The diagnostic performance of advanced MARS-MRI for PSI was quantified using sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC). When applying the International Consensus Meeting (ICM) 2018 criteria, of the 89 participants, 22 (25%) were deemed as being infected and 67 (75%) were classified as being not infected (unlikely to have PSA and not requiring a surgical procedure during 1-year follow-up).

RESULTS

The interreader reliability and intrareader repeatability of advanced MARS-MRI findings, including lymphadenopathy, joint effusion, synovitis, extra-articular fluid collection, a sinus tract, rotator cuff muscle edema, and periprosthetic bone resorption, were good (κ = 0.61 to 0.80) to excellent (κ > 0.80). Lymphadenopathy, complex joint effusion, and edematous synovitis had sensitivities of >85%, specificities of >90%, odds ratios of >3.6, and AUC values of >0.90 for diagnosing PSI. The presence of all 3 findings together yielded a PSI probability of >99%, per logistic regression analysis.

CONCLUSIONS

Our study shows the clinical utility of advanced MARS-MRI for diagnosing PSI when using the ICM 2018 criteria as the reference standard. Although the reliability and diagnostic accuracy were high, these conclusions are based on our specific advanced MARS-MRI protocol interpreted by experienced musculoskeletal radiologists. Investigations with larger sample sizes are needed to confirm these results.

LEVEL OF EVIDENCE

Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

The painful shoulder arthroplasty: appropriate work-up and review of interventional pain treatments

Shoulder arthroplasty is a successful surgical procedure for several conditions when patients become refractory to conservative management modalities. Unfortunately, some patients experience persistent chronic pain after shoulder arthroplasty. These individuals should undergo a comprehensive evaluation by an orthopedic surgeon to determine whether structural pathology is responsible for the pain and to decide whether reoperation is indicated. At times, a surgical solution does not exist. In these circumstances, a thorough and specific plan for the management of persistent chronic pain should be developed and instituted. In this article, we review common reasons for persistent pain after shoulder arthroplasty and outline the evaluation of the painful shoulder arthroplasty. We then provide a thorough review of interventional pain management strategies. Finally, we hypothesize developments in our field that might provide better outcomes in the future for patients suffering with chronic intractable pain after shoulder arthroplasty.

ACR Appropriateness Criteria® Imaging After Shoulder Arthroplasty: 2021 Update

Shoulder arthroplasty is a common orthopedic procedure with a complication rate reported to be as high as 39.8% and revision rates as high as 11%. Symptoms related to postoperative difficulties include activity-related pain, decreased range of motion, and apprehension. Some patients report immediate and persistent dissatisfaction, although others report a symptom-free postoperative period followed by increasing pain and decreasing shoulder function and mobility. Imaging plays an important role in diagnosing postoperative complications of shoulder arthroplasties. The imaging algorithm should always begin with radiographs. The selection of the next imaging modality depends on several factors, including findings on the initial imaging study, clinical suspicion of an osseous versus soft-tissue injury, and clinical suspicion of infection.The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Magnetic Resonance Imaging Around Metal at 1.5 Tesla: Techniques From Basic to Advanced and Clinical Impact

ABSTRACT

During the last decade, metal artifact reduction in magnetic resonance imaging (MRI) has been an area of intensive research and substantial improvement. The demand for an excellent diagnostic MRI scan quality of tissues around metal implants is closely linked to the steadily increasing number of joint arthroplasty (especially knee and hip arthroplasties) and spinal stabilization procedures. Its unmatched soft tissue contrast and cross-sectional nature make MRI a valuable tool in early detection of frequently encountered postoperative complications, such as periprosthetic infection, material wear-induced synovitis, osteolysis, or damage of the soft tissues. However, metal-induced artifacts remain a constant challenge. Successful artifact reduction plays an important role in the diagnostic workup of patients with painful/dysfunctional arthroplasties and helps to improve patient outcome. The artifact severity depends both on the implant and the acquisition technique. The implant's material, in particular its magnetic susceptibility and electrical conductivity, its size, geometry, and orientation in the MRI magnet are critical. On the acquisition side, the magnetic field strength, the employed imaging pulse sequence, and several acquisition parameters can be optimized. As a rule of thumb, the choice of a 1.5-T over a 3.0-T magnet, a fast spin-echo sequence over a spin-echo or gradient-echo sequence, a high receive bandwidth, a small voxel size, and short tau inversion recovery-based fat suppression can mitigate the impact of metal artifacts on diagnostic image quality. However, successful imaging of large orthopedic implants (eg, arthroplasties) often requires further optimized artifact reduction methods, such as slice encoding for metal artifact correction or multiacquisition variable-resonance image combination. With these tools, MRI at 1.5 T is now widely considered the modality of choice for the clinical evaluation of patients with metal implants.

Reverse total shoulder arthroplasty: an imaging overview

Although not as common as hip or knee arthroplasty, shoulder arthroplasty is becoming a more common procedure. Reverse total shoulder arthroplasty (RTSA) is known to be an effective surgical procedure for massive irreparable rotator cuff tears, comminuted proximal humerus fractures, and revision shoulder arthroplasty. The utilization of RTSA has been increasing, and although complications following reverse arthroplasty have been reported, there are few reports in the literature that focus on the imaging features of RTSA. Herein, we demonstrate the biomechanics of RTSA, prosthesis components, indications, and imaging features of the normal postoperative appearance and various complications after RTSA. Familiarization with the normal and abnormal imaging appearances after RTSA can be helpful for appropriate management of patients.

Imaging of shoulder arthroplasties and their complications: a pictorial review

Currently, an increasing number of patients benefit from shoulder prosthesis implantation. Radiologists are therefore more often confronted with imaging examinations involving shoulder arthroplasty, whether during a dedicated examination or incidentally. Standard radiography is the first-line imaging modality in the follow-up of these implants, before the possible use of cross-sectional imaging modalities (computed tomography and magnetic resonance imaging), ultrasound, or nuclear medicine examinations. Shoulder arthroplasties are divided into three categories: reverse shoulder arthroplasty, total shoulder arthroplasty, and partial shoulder joint replacement (including humeral hemiarthroplasty and humeral head resurfacing arthroplasty). Each of these prostheses can present complications, either shared by all types of arthroplasty or specific to each. Infection, periprosthetic fractures, humeral component loosening, heterotopic ossification, implant failure, and nerve injury can affect all types of prostheses. Instability, scapular notching, and acromial fractures can be identified after reverse shoulder arthroplasty implantation. Glenoid component loosening and rotator cuff tear are specific complications of total shoulder arthroplasty. Progressive wear of the native glenoid is the only specific complication observed in partial shoulder joint replacement. Knowledge of different types of shoulder prostheses and their complications’ radiological signs is crucial for the radiologist to initiate prompt and adequate management.

Imaging of Shoulder Arthroplasties

OBJECTIVE

In this article, we review the preoperative imaging features used for planning shoulder arthroplasty as well as review the various shoulder arthroplasty component types, discussing the expected normal imaging features and specific complications to look for with each.

CONCLUSION

Given the increasing use of shoulder arthroplasty, it is important to understand the imaging features of the various shoulder arthroplasty complications.

Advances in MRI around metal

The prevalence of orthopedic metal implants is continuously rising in the aging society. Particularly the number of joint replacements is increasing. Although satisfying long-term results are encountered, patients may suffer from complaints or complications during follow-up, and often undergo magnetic resonance imaging (MRI). Yet metal implants cause severe artifacts on MRI, resulting in signal-loss, signal-pileup, geometric distortion, and failure of fat suppression. In order to allow for adequate treatment decisions, metal artifact reduction sequences (MARS) are essential for proper radiological evaluation of postoperative findings in these patients. During recent years, developments of musculoskeletal imaging have addressed this particular technical challenge of postoperative MRI around metal. Besides implant material composition, configuration and location, selection of appropriate MRI hardware, sequences, and parameters influence artifact genesis and reduction. Application of dedicated metal artifact reduction techniques including high bandwidth optimization, view angle tilting (VAT), and the multispectral imaging techniques multiacquisition variable-resonance image combination (MAVRIC) and slice-encoding for metal artifact correction (SEMAC) may significantly reduce metal-induced artifacts, although at the expense of signal-to-noise ratio and/or acquisition time. Adding advanced image acquisition techniques such as parallel imaging, partial Fourier transformation, and advanced reconstruction techniques such as compressed sensing further improves MARS imaging in a clinically feasible scan time. This review focuses on current clinically applicable MARS techniques. Understanding of the main principles and techniques including their limitations allows a considerate application of these techniques in clinical practice. Essential orthopedic metal implants and postoperative MR findings around metal are presented and highlighted with clinical examples.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:972-991.