UW Shoulder and Elbow Academy: tilt

Thursday, July 10, 2025

Preoperative planning for reverse total shoulder using plain films.

A major component of the success of reverse total shoulder arthroplasty is the position and orientation of the base plate on the glenoid bone. While many different planning systems are available, the challenge is transferring the plan to the patient without relying on expensive and time-consuming approaches, such patient specific instrumentation or augmented reality.

Our usual target is to have the inferior edge of the baseplate at the inferior aspect of the reamed glenoid and tilted inferiorly with the central screw or peg inclined so that it is parallel to the floor of the supraspinous fossa.

For routine cases, we plan for rTSA using plain x-rays obtained in the plane of the scapula (Grashey view). The scaled image is uploaded to the universally available PACS (Picture Archiving and Communication System). PACS tools are used to find the location of insertion point and the inclination of the drill for the central screw or post. These scaled measurements are then used to position and orient the drill on the patient's glenoid in the operating room. This generic approach does not encourage the surgeon to select implants from any particular company.

Here's an example: a 70 year old man with a massive irreparable cuff tear and pseudo paralysis.

On the PACS screen a line segment (yellow) with a length equal to the radius of the base plate is drawn perpendicular to the floor of the supraspinatus fossa (red line) from the glenoid articular surface to the glenoid neck. The upper end of this line is the insertion point (yellow dot)

The distance of this point along the glenoid articular surface (green line) from the inferior glenoid lip is measured on the scaled PACS image. The insertion point can be found at surgery by measuring this distance using a flexible ruler.

The angle of drill insertion (dotted gold line) relative to the joint surface at the insertion point (black line) is noted on PACS and duplicated at surgery.

Favard et al have described four types of glenoid pathoanatomy in cuff tear arthropathy.

For some cases, such as types E1 and E3, this planning approach may indicate that excessive reaming of inferior glenoid bone would be necessary to achieve the desired baseplate position and orientation. In such cases superior bone grafting or an augmented baseplate may be called for.

While more sophisticated proprietary systems can be used for more complex pathoanatomy, this generic approach can be effective for a large percentage of rTSA cases.

We use a similar plain films/PACS approach to planning a stemless anatomic arthroplasty - see this link.

Sometimes a convenient solution is staring right at us

Sooty Grouse

Mt. Rainier

July 4, 2025

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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).

Friday, July 15, 2016

Reverse total shoulder arthroplasty - tilting the baseplate

Accuracy of the Subchondral Smile and Surface Referencing Techniques in Reverse Shoulder Arthroplasty.

These authors point out that inferior glenoid baseplate tilt relative to the coronal axis of the scapular body has been associated with improved results and fewer postoperative complications in reverse shoulder arthroplasty. They evaluated the accuracy of the "subchondral smile" and cannulated surface guide techniques in achieving inferior glenoid baseplate tilt by using 3-dimensional preoperative planning software. Virtual glenoid baseplate preparation and implantation were performed using computed tomography scans of 16 shoulders with rotator cuff deficiency. Two techniques were used: a subchondral smile technique that preferentially reams the interior glenoid, resulting in the appearance of a smile, and a cannulated surface guide technique that references the native glenoid face to place the baseplate in 10° of inferior tilt.

Using the subchondral smile technique, the glenoid baseplate was implanted at a mean of 8.9° of superior tilt relative to the transverse scapular axis. Using the surface guide technique, the glenoid baseplate was implanted at a mean of 2.8° of superior tilt.

Neither the subchondral smile technique nor the 10° cannulated surface guide technique is a reliable method to produce inferior glenoid tilt relative to the transverse axis of the scapula.

They suggest that three-dimensional preoperative planning software may be useful for glenoid baseplate positioning in reverse shoulder arthroplasty.

Comment: Our practice is to obtain a preoperative true anteroposterior radiograph in the plane of the scapula and then use that image to envision a line perpendicular to the glenoid center. At surgery, the drill for the central screw of the baseplate is oriented by eye with a slight inferior tilt in reference to this perpendicular to the glenoid center. No guides or special instrumentation is used. In cases where the preoperative true anteroposterior radiograph in the plane of the scapula indicates a superior inclination of the perpendicular to the glenoid center, the angle of the drill is adjusted accordingly.

This approach is shown for the left and right shoulders of a patient having had a failed hemiarthroplasty on one side and pseudo paralysis on the other.

Our approach to reverse total shoulder arthroplasty is shown in this link. Our goal, whenever possible, is a cementless impaction grafted humeral stem with a 135 degree angle and a laterally offset glenopshere securely fixed with screws in the high quality bone at the base of the subscapularis fossa with minimal inferior placement to avoid excess tension on the acromion and the brachial plexus. The use of a glenosphere with lateral offset makes the exact inclination of the component less critical.