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Monday, February 16, 2026

Humeral and glenoid component malposition in revised shoulder arthroplasty - Part I - what might have been done differently?

The authors of Humeral and glenoid component malposition in patients requiring revision shoulder arthroplasty: a retrospective, cross-sectional study explored 234 cases of revised shoulder arthroplasty and reported "quantitative analysis demonstrated that the majority of glenoid components in these revision cases were malpositioned in both TSA (51%) and RSA (93%) when all measures were considered. Similarly, there was humeral component malposition in 57% of TSA cases, 62% of RSA cases, and 54% of hemiarthroplasty cases when all measures were considered. When asked if there was glenoid component malposition, the independent reviewer considered 17% of glenoid components to be malpositioned in TSA cases and 54% in RSA cases. The investigative institutions reported similar rates. For the humeral side, the independent reviewer felt that 71% of TSA cases, 24% of RSA cases, and 74% of hemiarthroplasty implants were malpositioned in some direction. The investigative institutions reported similar rates."

This article is very thought provoking: it merits two posts. Here's the first.

The authors conclude:  "Improved component positioning is needed, including the development of more effective intra-operative techniques to ensure proper humeral and glenoid component position to minimize the risk of revision surgery." 

The authors' examples of malposition are shown below, providing an opportunity to consider what might have been done differently in each case to avoid the malpostion (see Of successful mammoth hunting and glenoid component failure - modeling causation).

Knowing full well that many of this blog's readers would consider a high-tech approach, here's how we'd try to avoid these malpositions in my practice.

A. Humeral head too high








The "head high" problem may be avoided by assuring that the humeral head is placed just below the berm. 


Note also in both of these cases the diaphysis of the humeral component was too large, causing stem incarceration, preventing full seating of the component. Stem incarceration may be prevented by using a smaller diameter humeral component with impaction grafting, 



using a short stem, or using a stemless component.




B. Insufficient humeral resection



The "long neck" problem may be avoided by full exposure of the anatomic neck for the cut.


C. Too high baseplate


The "Baseplate High" problem may be avoided by making preoperative measurements on a plain preoperative Grashey view. Below left, a line segment equal to half the baseplate diameter is drawn from the inferior glenoid to the articular surface perpendicular to the supraspinatus fossa line. A second line segment is drawn from the inferior glenoid lip to the intersection of the first line segment with the articular surface. This distance can me measured at surgery. This intersection indicates the starting point for the drill.



D. Superior tilt of baseplate. 


The "baseplate looking up" problem may be avoided by making preoperative measurements on a plain preoperative Grashey view. Below left a line (yellow) is drawn from the drill insertion point (see "C" above) parallel to the supraspinatus fossa line. This is the drill trajectory. Below right the angle between the drill trajectory and the superior face of the glenoid is noted and used to define the tilt of the drill for insertion of the baseplate.




Looking forward to your comments!


Northern Flicker
Matsen Backyard
2022



Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link)
The total shoulder arthroplasty (see this link)
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link)
Shoulder rehabilitation exercises (see this link). 
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