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Shoulder Arthroplasty & Arthritis MCQs

Practice Set 14 of 14

This practice set contains high-yield board review questions covering key concepts in Shoulder Arthroplasty & Arthritis. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 261

Topic: Shoulder Arthroplasty & Arthritis

You are describing the technique for a total shoulder arthroplasty. The examiner abruptly asks, 'What is the most common and often devastating complication unique to reverse total shoulder arthroplasty (rTSA) compared to anatomic TSA, and how do you mitigate it?'

. Aseptic loosening of the humeral component, mitigated by cementing the stem.
. Axillary nerve palsy due to surgical dissection, mitigated by careful nerve identification.
. Scapular notching, caused by impingement of the humeral polyethylene liner on the inferior glenoid neck. It is mitigated by appropriate glenosphere lateralization, inferior placement, and proper soft tissue tensioning.
. Infection, mitigated by strict sterile technique and perioperative antibiotics.
. Rotator cuff failure, mitigated by preserving the subscapularis.

Correct Answer & Explanation

. Scapular notching, caused by impingement of the humeral polyethylene liner on the inferior glenoid neck. It is mitigated by appropriate glenosphere lateralization, inferior placement, and proper soft tissue tensioning.

Explanation

Scapular notching is a complication unique and relatively common to reverse total shoulder arthroplasty, where the humeral polyethylene liner impinges on the inferior aspect of the scapular neck during adduction and internal rotation, leading to erosion of the bone. It can lead to pain, reduced range of motion, and implant loosening. Mitigation strategies include lateralizing the glenosphere, inferomedial placement of the glenosphere, and achieving appropriate soft tissue tension. Axillary nerve palsy (B) can occur in both, but scapular notching is unique to rTSA. Aseptic loosening (A) is a general arthroplasty complication, not unique. Infection (D) is also a general complication. Rotator cuff failure (E) is thereasonfor rTSA in many cases, not a unique complicationofrTSA in the context of anatomic TSA comparison.

Question 262

Topic: Shoulder Arthroplasty & Arthritis

To minimize the risk of scapular notching during a Reverse Total Shoulder Arthroplasty (RTSA), how should the glenosphere ideally be positioned?

. Superior tilt and superior translation
. Inferior tilt and inferior translation
. Superior tilt and inferior translation
. Inferior tilt and superior translation

Correct Answer & Explanation

. Inferior tilt and inferior translation

Explanation

Scapular notching occurs when the medial aspect of the humeral component impinges on the inferior scapular neck. This complication is minimized by placing the glenosphere with an inferior tilt and inferior translation, allowing it to overhang the inferior rim of the glenoid.

Question 263

Topic: Shoulder Arthroplasty & Arthritis

A 72-year-old female undergoes reverse total shoulder arthroplasty for cuff tear arthropathy. Which of the following best describes the biomechanical alteration achieved by this prosthesis compared to native anatomy?

. Lateralizes and superiorly translates the center of rotation
. Medializes and inferiorly translates the center of rotation
. Medializes and superiorly translates the center of rotation
. Lateralizes and inferiorly translates the center of rotation
. Maintains the native center of rotation but increases the deltoid moment arm

Correct Answer & Explanation

. Medializes and inferiorly translates the center of rotation

Explanation

Reverse total shoulder arthroplasty medializes and inferiorly translates the center of rotation. This alteration increases the deltoid moment arm and tension, compensating for the deficient rotator cuff to allow active elevation.

Question 264

Topic: Shoulder Arthroplasty & Arthritis

In a reverse total shoulder arthroplasty (RTSA), scapular notching is a well-recognized complication. Which of the following glenosphere positioning strategies is most effective in minimizing the incidence of scapular notching?

. Inferior placement and inferior tilt
. Superior placement and superior tilt
. Neutral placement with superior tilt
. Lateralized placement with superior tilt
. Medialized placement with neutral tilt

Correct Answer & Explanation

. Inferior placement and inferior tilt

Explanation

Inferior placement and inferior tilt of the glenosphere in RTSA are key surgical strategies to prevent impingement of the humeral component against the scapular neck. This configuration reduces the risk of inferior scapular notching.

Question 265

Topic: Shoulder Arthroplasty & Arthritis

The Grammont design principles for a reverse total shoulder arthroplasty (RTSA) revolutionized the treatment of cuff tear arthropathy. Which of the following statements best describes the primary biomechanical changes achieved by this design compared to normal shoulder anatomy?

. It lateralizes the center of rotation and shifts the humerus proximally to increase tension on the rotator cuff.
. It medializes the center of rotation and shifts the humerus distally to optimize the tension and moment arm of the deltoid.
. It shifts the center of rotation superiorly and maintains humeral length to preserve subscapularis function.
. It perfectly recreates the native anatomical center of rotation to restore normal joint kinematics.
. It lateralizes both the center of rotation and the humerus to increase the lever arm of the supraspinatus.

Correct Answer & Explanation

. It medializes the center of rotation and shifts the humerus distally to optimize the tension and moment arm of the deltoid.

Explanation

The Grammont reverse shoulder arthroplasty design is based on two key biomechanical principles: 1) Medializing the center of rotation, which recruits more deltoid fibers and significantly increases the deltoid moment arm (making it more efficient as an elevator). 2) Distalizing (lowering) the humerus, which increases tension on the deltoid muscle, optimizing its length-tension curve to compensate for the absent superior rotator cuff.

Question 266

Topic: Shoulder Arthroplasty & Arthritis

A 72-year-old with pseudoparalysis and severe rotator cuff tear arthropathy is indicated for a reverse total shoulder arthroplasty (RTSA). Which biomechanical alteration explains the success of RTSA in restoring forward elevation?

. It medializes and inferiorly displaces the center of rotation, tensioning the deltoid
. It lateralizes and superiorly displaces the center of rotation
. It relies heavily on an intact supraspinatus for overhead mechanics
. It restores the anatomical neck-shaft angle of the native humerus
. It shifts the center of rotation to the anatomic center of the humeral head

Correct Answer & Explanation

. It medializes and inferiorly displaces the center of rotation, tensioning the deltoid

Explanation

RTSA shifts the center of rotation medially and inferiorly. This effectively lengthens the deltoid lever arm and increases its resting tension, allowing the deltoid to compensate for the deficient rotator cuff.

Question 267

Topic: Shoulder Arthroplasty & Arthritis

Which of the following describes the most common radiographic finding for a Walch Type B1 glenoid?

. Concentric glenoid wear without posterior subluxation.
. Posterior glenoid erosion with less than 25 degrees of retroversion and the humeral head centered.
. Posterior glenoid erosion with greater than 25 degrees of retroversion and posterior humeral head subluxation.
. Biconcave glenoid erosion with significant retroversion.
. Dysplastic glenoid with severe retroversion (>25 degrees).

Correct Answer & Explanation

. Posterior glenoid erosion with less than 25 degrees of retroversion and the humeral head centered.

Explanation

A Walch Type B1 glenoid is characterized by posterior glenoid erosion, but with less than 25 degrees of retroversion, and crucially, the humeral head is still relatively centered on the glenoid, not significantly subluxated posteriorly. The posterior erosion is typically uniconcave. Option A describes a Walch A2. Option C and D describe Walch B2. Option E describes a Walch C.

Question 268

Topic: Shoulder Arthroplasty & Arthritis

A 62-year-old male presents with chronic shoulder pain. MRI findings include extensive chondral delamination, subchondral bone cysts, and full-thickness supraspinatus tear with retraction. What is the most appropriate long-term management consideration for this patient?

. Physical therapy focusing on rotator cuff strengthening.
. Diagnostic arthroscopy with debridement.
. Reverse total shoulder arthroplasty (rTSA).
. Subacromial decompression and rotator cuff repair.
. Long-term NSAIDs and activity modification.

Correct Answer & Explanation

. Reverse total shoulder arthroplasty (rTSA).

Explanation

The combination of extensive chondral delamination, subchondral bone cysts (advanced OA features), and a retracted full-thickness supraspinatus tear indicates rotator cuff tear arthropathy (RCAT) with significant articular destruction. In such cases, standard rotator cuff repair is often not feasible or durable due to tissue quality and retraction, and the arthritis component is significant. Reverse total shoulder arthroplasty (rTSA) is typically the most effective surgical treatment for RCAT, as it provides stability and restores function by bypassing the deficient rotator cuff. Physical therapy, debridement alone, or subacromial decompression/cuff repair are generally inadequate for this advanced pathology. Long-term NSAIDs are palliative but not curative for such advanced disease.

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