Clicking After Reverse Total Shoulder Arthroplasty: Causes
Clicking in the shoulder after reverse total shoulder arthroplasty is most commonly caused by impingement between the humeral component and the scapular neck (scapular notching), component instability or subluxation, polyethylene wear, or hardware-related mechanical issues including glenoid baseplate micromotion.
Primary Mechanical Causes
The clicking sensation typically originates from one of several biomechanical complications specific to the reverse shoulder design:
Scapular Notching and Impingement
Scapular notching is the most frequent radiographic finding after reverse total shoulder arthroplasty and represents a primary source of mechanical clicking. This occurs when the humeral implant impinges against the inferior scapular neck during adduction movements 1. The erosive lesion that develops can create audible and palpable clicking as the components interact 2. The incidence and severity relate directly to:
- Glenosphere size, shape, and positioning
- Humeral neck-shaft angle inclination
- Implant offset characteristics
- Native scapular anatomy 2
While the clinical significance of mild notching remains debated, severe notching can lead to functional deterioration and glenoid implant loosening 2.
Component Instability and Subluxation
Glenohumeral instability represents a critical cause of clicking that requires immediate attention, as it frequently precedes frank dislocation. The ACR guidelines identify instability as one of the most common complications specific to reverse total shoulder arthroplasty 1.
Key risk factors for instability-related clicking include:
- Male gender (82% in dislocation cohorts) 3
- Body mass index ≥30 kg/m² (82% association) 3
- Subscapularis deficiency or failed repair (64% of cases) 3, 4
- Previous shoulder surgery (64% of unstable patients) 3
- Revision arthroplasty (6.5% dislocation rate vs. 1.6% for primary) 4
A history of postoperative subluxations before confirmed dislocation carries a 19.52 odds ratio for subsequent dislocation 4, making clicking with a sensation of instability a critical warning sign.
Polyethylene Wear and Hardware Issues
Polyethylene wear between the humeral cup and glenosphere creates debris that can cause clicking sensations 1. Additionally, glenoid baseplate micromotion or early loosening produces mechanical symptoms before radiographic changes become apparent 1.
Diagnostic Approach
Begin with standard radiographs in multiple projections (AP, Grashey, scapular Y, and axillary views) to assess hardware alignment, component positioning, and scapular notching 1. The imaging algorithm should systematically evaluate:
- Hardware component integrity and alignment
- Scapular notching presence and severity (graded radiographically)
- Glenoid baseplate positioning and signs of loosening
- Humeral component position relative to glenosphere
- Periprosthetic bone quality
Advanced Imaging Indications
If radiographs are normal but clicking persists with concerning features:
- CT with metal artifact reduction for detailed hardware assessment, occult loosening, or subtle scapular notching not visible on plain films 1
- Ultrasound for soft tissue evaluation, particularly subscapularis integrity and fluid collections 5
- MRI with metal artifact protocols when rotator cuff pathology or soft tissue abnormalities are suspected 1
Clinical Significance and Management
Clicking alone without pain, instability symptoms, or functional decline may represent benign scapular notching or normal prosthetic mechanics and can be observed. However, clicking accompanied by:
- Pain with specific movements
- Sensation of instability or "giving way"
- Progressive functional decline
- Apprehension with certain positions
...requires thorough evaluation as these suggest impending complications that may progress to dislocation, component failure, or loosening 1, 6.
Common Pitfalls
Do not dismiss clicking in high-risk patients (male, BMI >30, subscapularis deficiency, revision cases) as this population has substantially elevated dislocation risk 3, 4. The median time to dislocation is only 7 weeks postoperatively, with 45% of unstable prostheses ultimately requiring polyethylene exchange 3.
Scapular notching on radiographs does not always correlate with symptoms, but progressive notching warrants closer monitoring as it may lead to glenoid loosening over time 2, 7. SPECT/CT can differentiate symptomatic from asymptomatic notching when clinical correlation is unclear 1.
Avoid attributing all clicking to "normal postoperative changes" beyond the first 3-6 months, as complications including loosening can manifest years after surgery, with notable radiographic changes appearing at least 5 years postoperatively 1.