Multimodality imaging in shoulder arthroplasties Part 2: Immediate pre- and intra-operative imaging and imaging of early and late complications – A pictorial review
How to cite this article: Sarvesvaran M, Srinivasan S, Brar RS, Bhatt R, Gupta H, Thaker S. Multimodality imaging in shoulder arthroplasties Part 2: Immediate pre- and intra-operative imaging and imaging of early and late complications – A pictorial review. Indian J Musculoskelet Radiol 2021;3:88-93.
Shoulder arthroplasty imaging requires a thorough understanding of surgical techniques, biomechanics involved during and after the joint replacement surgery and complications unique to shoulder arthroplasties. One may believe that imaging of complications requires excessive complex imaging modalities such as MRI or nuclear imaging. However, contrary to such beliefs, one can diagnose such complications mostly on radiographs. We will describe advances in immediate pre-operative imaging and utility of imaging to diagnose shoulder arthroplasty- related complications in part 2 of our two-part pictorial review series.
We have described indications for shoulder arthroplasties, enumerated their types, and illustrated pre-operative imaging pictorially in the part 1 of two-part article series. In the part 2, we narrate perioperative imaging and introduce concepts of pre- and intra-operative CT navigation. We shall also discuss shoulder arthroplasty contraindications [Table 1] as well as both, general and arthroplasty-specific complications.
SHOULDER SURGEON’S PERSPECTIVE
Use of CT in pre-operative planning, implant selection, and 3D printing
CT using bespoke Software protocols assists with preoperative planning and is powerful tools in the surgeon’s armamentarium. It helps the surgeon to understand the altered anatomy, glenoid wear, and version when specialized surgical techniques (e.g. augmentation using bone or metal to recreate the glenoid in reverse TSR, or specialized polyethylene for anatomic TSR) are necessary. It further aids in using patient-specific instrumentation (PSI) and/or executing navigation for a correct implant placement, minimizing human error, and possibly improving the longevity of the implant. New artificial intelligence algorithms incorporated in the software can predict the best implant and procedure combination based on the CT [Figure 1]. 3D printing provides the surgeon a platform to rehearse the procedure in a safe environment to help minimize errors during surgery and makes the surgical procedure safer.
It helps the surgeon by providing real-time feedback, allowing the surgeon to make necessary adjustments when presented with altered anatomy, particularly in cases where there has been a delay between acquisition of the pre- operative imaging and the surgical procedure. It further aids the surgeon by determining the correct scapular and glenoid axis, glenoid version and depth of reaming for the glenoid, avoiding areas of potentially weak bone [Figure 2], and ensuring correct placement of screws, including their direction and length.
EARLY POST-OPERATIVE COMPLICATIONS
Despite advances in more sophisticated imaging modalities, imaging of shoulder arthroplasty complications is still heavily reliant on plain film radiography. Ultrasound may be helpful in some suspected rotator cuff tears, and CT may be necessary when fractures are radiographically occult and clinical suspicion is high.
Deep prosthetic joint infection is the most common complication in the first 2 years following total shoulder arthroplasty (TSA). Its incidence can range up to 3.9% for anatomic TSA and up to 5% for reverse TSA. Diagnosis and management of prosthetic infections are evaluated using the Musculoskeletal Infection Society criteria. This advocates a multidisciplinary approach, predominantly based on clinical and biochemical parameters with minimal involvement of radiology. Treatment options include long-term antibiotic suppression, debridement, antibiotics, and implant retention, and two-stage revision (considered the gold standard, Figure 3b).
In early loosening, the role of radiological investigations could involve anteroposterior and lateral radiographs to look for prosthetic loosening [Figure 3a]. CT is very useful in assessing for implant loosening, bone stock on the glenoid and humeral side, as well as helping with pre-operative planning or customized computer-aided design/manufacture (CADCAM) prosthesis. Bone scans are unable to differentiate between aseptic and septic loosening.[3,4]
Periprosthetic fractures have 1.5–3% prevalence and can occur intraoperatively, secondary to trauma post-surgery, or following chronic stress shielding. Stress shielding is the adaptation of periprosthetic bone to changes in stress forces distributed from the humeral stem [Figure 4]. It is seen in 9% of arthroplasty cases and is a risk factor for aseptic loosening and periprosthetic fracture. Stress shielding manifests radiologically as a central radiodensity and/or cortical thinning.
|Charcot’s neuroarthropathy following brachial plexus injury or other neuropathies|
|Ankylosed/arthrodesed shoulder following end-stage inflammatory or tubercular arthropathy which is functional and painless|
|Flail shoulder due to loss of axillary nerve function or stroke or poliomyelitis|
|Poor glenoid bone stock (very rare)|
Rotator cuff tears, particularly of the subscapularis, can be seen acutely (mean follow-up time – 1.9 years) following anatomical TSA. They become clinically evident soon after arthroplasty as an intact rotator cuff is necessary for adequate function. Plain film [Figure 5], ultrasound, and MRI with metal reduction sequences can be used to confirm the diagnosis. Revision to a reverse TSA can be performed in such cases. Rotator cuff tears can occur in either the early or late post-operative period.
A common complication following reverse TSA is anterior shoulder dislocation which can occur in up to 20% of patients [Figure 6]. It occurs in the anterosuperior direction rather than the usual anteroinferior direction, due to unopposed deltoid contraction.
LATE POST-OPERATIVE COMPLICATIONS
Periprosthetic loosening occurs most frequently in anatomical total shoulder arthroplasties. The glenoid component [Figure 7] is preferentially affected over the humeral stem component [Figure 8]. Typical radiographic findings are periprosthetic lucencies of more than 1.5 mm thickness and progression overtime. Loosening can progress to periprosthetic fracture. Periprosthetic movement can also manifest as metalwork fractures [Figure 9] or inferior glenoid resorption [Figure 10], characteristically seen in reverse TSA with medialized placement or when a smaller sized glenosphere is used.
Acromion and scapular spine fractures are exclusively seen in reverse total shoulder arthroplasties and are essential review areas for the radiologist. Early plain film changes are sclerosis and periosteal reaction at the site of pathology. Occasionally, plain films are unremarkable despite a strong clinical concern for stress fractures of the acromion or spine of the scapula, with the patient experiencing focal tenderness in these regions [Figure 11]. CT or bone scintigraphy is more sensitive subsequent investigations and may reveal abnormalities occult on plain film radiography.
EFFECTS OF IMAGING FINDINGS ON SURGICAL DECISIONS DURING SHOULDER ARTHROPLASTIES
A strategic use of imaging helps to plan an appropriate surgical procedure. Specifically, it helps while selecting specialist instrumentation and kit design (using CADCAM). 3D printing can help counsel patients and allow simulation of the surgical procedure if necessary. Aforementioned technical factors along with patient and surgeon-related human factors allow fully informed and optimal decision making. Patient motivation, realistic expectations, and the likelihood of adhering to post-operative rehabilitation including physiotherapy support are critical non-imaging considerations for prognostic assessment.
Pre-operative planning using CT helps foster better understanding and execution of shoulder replacements, especially in challenging scenarios. It has led to incremental use of either navigation-based operative procedures or custom-designed PSI for shoulder arthroplasties.
Complications are infrequent if meticulous attention is paid to correct patient selection, pre-operative optimization, managing patient expectations, and ensuring correct planning and appropriate execution.
Declaration of patient consent
Patient’s consent not required as patients identity is not disclosed or compromised.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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