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Shoulder Arthroplasty & Arthritis MCQs

Practice Set 3 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 41

Topic: Shoulder Arthroplasty & Arthritis

The best candidate for a reverse total shoulder arthroplasty is a patient with rotator cuff tear arthropathy with Review Topic

. anterior superior escape.
. rheumatoid arthritis.
. an acromial stress fracture.
. a centered head and an external rotation lag sign of 50 degrees.
. active forward elevation of 130 degrees.

Correct Answer & Explanation

. anterior superior escape.

Explanation

Reverse total shoulder arthroplasty is relatively contraindicated in patients with acromial stress fractures and rheumatoid arthritis. A patient with active forward elevation to 130 degrees is better treated with a hemiarthroplasty because the motion already exceeds the average forward elevation attained in most studies using the reverse prosthesis. A centered case of rotator cuff tear arthropathy is also better treated with a hemiarthroplasty, especially in patients with a large external rotation lag sign because the reverse prosthesis has been shown to decrease active external rotation. However, hemiarthroplasties have not performed well in patients with anterior superior escape and in this group of patients, the reverse prosthesis is best.

Question 42

Topic: Shoulder Arthroplasty & Arthritis

A 76-year-old woman has longstanding right shoulder pain affecting overhead function. Figures A and B are her original radiographs. She undergoes reverse total shoulder arthroplasty (rTSA) with iliac crest bone grafting behind the baseplate and is discharged from the hospital the following day. She returns for follow-up at 2 weeks. The incisions have healed and she has minimal pain, which is improving. What is the most accurate description for the cause of failure? Review Topic

. Central peg error
. Insufficient inferior tilt
. Excessive inferior tilt
. Component dissociation
. Glenosphere too small

Correct Answer & Explanation

. Central peg error

Explanation

The metaglen (glenoid baseplate) failed because the central peg of the baseplate was not implanted in the glenoid, and the metaglen did not have a long enough central peg. This was the technical error during baseplate implantation.Glenoid complications are the primary concern of rTSA. Historically, rTSA fail at the glenoid interface because of inadequate fixation. The Grammont-style prosthesis has a medialized center of rotation to circumvent this, but this lead to inferior scapular notching. Newer prosthesis include locking peripheral screws and 15° inferior tilt of the base plate. Further, changing the neck-shaft angle from 155 deg to 143 deg or 135 deg has reduced notching and instability, and reduced the need to for subscapularis repair.Boileau et al. examined revision surgery for rTSA. They found that the most common cause for revision was prosthetic instability (48%). Humeral complications (loosening/derotation/fracture) were 2nd most common and infection was 3rd most common. Underestimation of humeral shortening and excessive medialization were common causes of recurrent prosthetic instability. Proximal humeral bone loss was found to be a cause for humeral loosening or derotation.Holcomb et al. reviewed failure of the rTSA glenoid baseplate in 14 patients, which was defined as shift of the baseplate with or without screw breakage. Strategies for success include: (1) Incorporating increased inferior baseplate tilt in post-revision prosthesis-scapular neck angle (PSNA) compared to pre-failure PSNA because inferior tilt maximizes compressive force across the baseplate-glenoid interface. (2) Locking peripheral 5.0mm screws (rather than non-locking 3.5mm screws). (3) Using larger glenospheres to tighten the patulous soft tissue envelope and secure the glenoid allograft. Four patients required structural allograft (2 iliac crest, 2 femoral head).Figures A shows Hamada 4A cuff tear arthropathy. Figure B shows severe static posterior instability of the humeral head and posterior Walch B2 erosion of the glenoid. Figure C shows the same patient treated with rTSA and iliac crest bone graft. Because of technical error, the central peg was not implanted in the native glenoid. Illustration A shows catastrophic failure of the glenoid baseplate. Illustration B shows the PSNA, with increase in the PSNA from initial rTSA to revision rTSA. Illustration C shows baseplate-glenosphere dissociation. Illustration D shows correction of technical error/too short peg with exchange to a baseplate with a longer peg. Illustration E shows and algorithm for treating unstable rTSA.Incorrect Answers:

Question 43

Topic: Shoulder Arthroplasty & Arthritis

A 72-year-old female undergoes a reverse total shoulder arthroplasty for cuff tear arthropathy. How does the biomechanical design of the prosthesis primarily improve active elevation?

. It lateralizes and superiorizes the center of rotation to tension the remaining rotator cuff.
. It medializes and inferiorizes the center of rotation to increase the deltoid moment arm.
. It increases deltoid wrapping without altering the anatomical center of rotation.
. It decreases the deltoid moment arm to prevent secondary acromial stress fractures.
. It restores the normal anatomic center of rotation but limits external rotation.

Correct Answer & Explanation

. It medializes and inferiorizes the center of rotation to increase the deltoid moment arm.

Explanation

A reverse total shoulder arthroplasty shifts the center of rotation medially and inferiorly. This change recruits more deltoid muscle fibers and significantly increases its moment arm, compensating for the absent rotator cuff.

Question 44

Topic: Shoulder Arthroplasty & Arthritis

In reverse total shoulder arthroplasty (RTSA), inferior tilt and inferior overhang of the glenosphere are primarily designed to prevent which of the following complications?

. Scapular notching
. Glenoid aseptic loosening
. Acromial stress fracture
. Anterior dislocation
. Greater tuberosity resorption

Correct Answer & Explanation

. Scapular notching

Explanation

Scapular notching is a common complication of RTSA caused by mechanical impingement of the humeral component against the scapular neck. Inferior tilt and overhang of the glenosphere laterally clear the implant from the bone, significantly reducing this risk.

Question 45

Topic: Shoulder Arthroplasty & Arthritis

What prosthetic factor has the most impact on decreasing the rate of scapular notching in a Grammont-style reverse total shoulder arthroplasty? Review Topic

. Posterior tilt of the glenoid component
. Inferior tilt of the glenoid component
. Inferior positioning of the glenoid component
. Use of a cemented humeral component
. Use of locking screws in the glenoid component

Correct Answer & Explanation

. Posterior tilt of the glenoid component

Explanation

A low position of the glenoid base plate has been shown to have the greatest effect on decreasing scapular notching with a Grammont-style prosthesis. Scapular notching is the phenomena seen after reverse total shoulder arthroplasty when bone along the inferior scapular neck is lost. It is thought to be the result of repeated contact between the humeral component and the bone. The Grammont-style reverse total shoulder arthroplasty has a medialized center of rotation that decreases strain at the glenoid component but has less space for the humerus to clear the scapula. Scapular notching was seen least in components that are placed low on the glenoid. Posterior and inferior tilt has minimal effect on scapular notching and may even increase notching by bringing the humerus closer to the scapula. The use of locking screws and a cemented humeral stem had no influence on notching.

Question 46

Topic: Shoulder Arthroplasty & Arthritis



In reverse total shoulder arthroplasty, placing the glenosphere with an inferior tilt rather than neutral or superior tilt achieves which of the following biomechanical advantages?

. Decreases the moment arm of the deltoid
. Increases the risk of scapular notching
. Decreases inferior shear forces on the baseplate
. Increases superior shear forces on the baseplate
. Reduces the impingement-free range of motion

Correct Answer & Explanation

. Decreases inferior shear forces on the baseplate

Explanation

Inferior tilt of the glenosphere in RTSA converts deleterious superior shear forces into compressive forces, improving baseplate fixation. It also helps decrease the rate of inferior scapular notching by providing better clearance.

Question 47

Topic: Shoulder Arthroplasty & Arthritis

What is the average version of the humeral head (with respect to the transepicondylar axis)? Review Topic

. 60 degrees retroversion
. 40 degrees retroversion
. 20 degrees retroversion
. 20 degrees anteversion
. 40 degrees anteversion

Correct Answer & Explanation

. 20 degrees retroversion

Explanation

Although there is considerable variability in humeral head retroversion among individuals, multiple anatomic studies have found mean humeral head retroversion to be approximately 20 degrees.One of the goals of primary anatomic total shoulder arthroplasty (TSA) is recreation and reconstruction of proximal humeral anatomy. Modular prostheses have evolved to provide surgeons with better capability to recreate proximal humeral morphology based on humeral head inclination, retroversion, offset, height and size. In terms of size, humeral head thickness has been found in cadaver studies to be 70% of its radius of curvature. This can be helpful to avoid 'over-stuffing' the joint or leaving it too loose.Boileau and Walch took digitized measurements of 65 humeri in order to create a computer model for proximal humeral morphology. They found that retroversion varied from -6.7 to 47.5 degrees, with a mean of 17.9. They advocate for prosthetic adaptability to recreate proximal humeral anatomy in a way that earlier generations of more geometrically constrained TSA implants could not.Robertson et al. made 3D computed tomographic models of 60 humeri (30 pairs) to study proximal humeral morphology. They found mean retroversion to be 19 degrees, with a range of 9 to 31 degrees. They found that proximal canal version was similar to head version but that canal version in the middle and distal sections of the canal was variable.Illustration A shows key proximal humeral morphologic parameters found by Robertson et al. in comparison with earlier studies (including Boileau's).Incorrect Answers:

Question 48

Topic: Shoulder Arthroplasty & Arthritis

A 72-year-old male with severe rotator cuff tear arthropathy undergoes a reverse total shoulder arthroplasty (rTSA). How does the rTSA implant alter the biomechanics of the shoulder joint compared to the native anatomy?

. Medializes and inferiorizes the center of rotation
. Medializes and superiorizes the center of rotation
. Lateralizes and inferiorizes the center of rotation
. Lateralizes and superiorizes the center of rotation
. Maintains the anatomic center of rotation but increases the deltoid lever arm

Correct Answer & Explanation

. Medializes and inferiorizes the center of rotation

Explanation

Reverse total shoulder arthroplasty (Grammont design) biomechanically alters the shoulder by medializing and inferiorizing the center of rotation. Medialization recruits more deltoid muscle fibers and decreases the torque on the glenoid component, while inferiorization tensions the deltoid and increases its moment arm, allowing the deltoid to compensate for the deficient rotator cuff to elevate the arm.

Question 49

Topic: Shoulder Arthroplasty & Arthritis

In reverse total shoulder arthroplasty (rTSA), which of the following glenosphere configurations is most effective at minimizing the risk of inferior scapular notching?

. Superior placement and superior tilt
. Superior placement and neutral tilt
. Inferior placement and inferior tilt
. Medialization and superior tilt
. Medialization and neutral tilt

Correct Answer & Explanation

. Inferior placement and inferior tilt

Explanation

Inferior placement and inferior tilt of the glenosphere help lateralize the humerus slightly and clear the inferior scapular neck, significantly reducing the mechanical impingement that causes scapular notching. Superior or medial placement increases impingement risk.

Question 50

Topic: Shoulder Arthroplasty & Arthritis

In reverse total shoulder arthroplasty, moving the center of rotation medially and inferiorly alters the biomechanics of the deltoid. Which of the following best describes this effect?

. Increases the deltoid moment arm and decreases deltoid tension
. Increases the deltoid moment arm and increases deltoid tension
. Decreases the deltoid moment arm and increases deltoid tension
. Decreases the deltoid moment arm and decreases deltoid tension
. Has no effect on the deltoid moment arm

Correct Answer & Explanation

. Increases the deltoid moment arm and increases deltoid tension

Explanation

The Grammont design of rTSA medializes and distalizes the center of rotation. This increases the deltoid moment arm, which improves its mechanical advantage, and increases deltoid tension, which improves stability and recruits more anterior and posterior deltoid fibers for elevation.

Question 51

Topic: Shoulder Arthroplasty & Arthritis

Which of the following component positioning strategies is most effective at reducing the incidence of scapular notching in reverse total shoulder arthroplasty?

. Superior placement of the glenosphere and neutral tilt
. Medialization of the glenosphere and superior tilt
. Inferior placement of the glenosphere with an inferior tilt
. Decreasing the lateral offset of the glenosphere
. Increasing the neck-shaft angle of the humeral component to 155 degrees

Correct Answer & Explanation

. Inferior placement of the glenosphere with an inferior tilt

Explanation

Scapular notching is a frequent complication of rTSA where the medial aspect of the humeral tray impinges on the inferior scapular neck. To minimize notching, the glenosphere should be placed inferiorly (overhanging the inferior glenoid rim) and tilted inferiorly. Lateralizing the center of rotation (either with a lateralized glenosphere or bone graft) and decreasing the humeral neck-shaft angle (e.g., to 135 or 145 degrees instead of 155) also reduce notching.

Question 52

Topic: Shoulder Arthroplasty & Arthritis

A 65-year-old female is scheduled for a total shoulder arthroplasty for primary osteoarthritis. Preoperative CT reveals a Walch B2 glenoid. What does a B2 glenoid signify, and what is a common surgical strategy for addressing it in anatomic TSA?

. Central wear with intact margins; addressed by concentric reaming.
. Biconcave glenoid with posterior wear; addressed by asymmetric reaming to correct retroversion, or bone grafting/augmented components if wear is severe.
. Dysplastic glenoid with severe retroversion (>25 degrees); requires reverse TSA.
. Anterior wear with anterior subluxation; requires anterior bone grafting.
. Superior migration of the humeral head; requires reverse TSA.

Correct Answer & Explanation

. Biconcave glenoid with posterior wear; addressed by asymmetric reaming to correct retroversion, or bone grafting/augmented components if wear is severe.

Explanation

The Walch classification describes glenoid morphology. A B2 glenoid is characterized by asymmetric posterior wear creating a biconcave surface and posterior subluxation of the humeral head. In anatomic TSA, this can be addressed by asymmetric anterior reaming (up to 10-15 degrees of retroversion correction, provided enough subchondral bone remains), posterior bone grafting, or using a posteriorly augmented glenoid component. If correction isn't possible without violating the glenoid vault, rTSA is indicated.

Question 53

Topic: Shoulder Arthroplasty & Arthritis

A 72-year-old male presents with inability to actively elevate his right arm past 45 degrees, despite having full passive range of motion. MRI demonstrates a massive, retracted tear of the supraspinatus and infraspinatus with Goutallier grade 4 fatty infiltration. The subscapularis and teres minor are intact. What is the most appropriate definitive surgical intervention?

. Arthroscopic primary rotator cuff repair
. Superior capsular reconstruction
. Latissimus dorsi tendon transfer
. Reverse total shoulder arthroplasty
. Anatomic total shoulder arthroplasty

Correct Answer & Explanation

. Reverse total shoulder arthroplasty

Explanation

This patient presents with pseudoparalysis (inability to actively elevate >90 degrees with preserved passive motion) secondary to a massive, irreparable rotator cuff tear (Goutallier 4 fatty infiltration implies irreversibility and irreparability). In an older patient with pseudoparalysis and an irreparable tear, reverse total shoulder arthroplasty (rTSA) is the treatment of choice, as it relies on the deltoid for elevation and does not require a functioning superior rotator cuff. Superior capsular reconstruction or tendon transfers are less predictable for reversing true pseudoparalysis in the elderly, and anatomic TSA is contraindicated in the absence of a functional cuff.

Question 54

Topic: Shoulder Arthroplasty & Arthritis

A 70-year-old female presents with sudden, sharp shoulder pain 6 months after an uncomplicated reverse total shoulder arthroplasty (rTSA). Radiographs reveal a new stress fracture of the acromion base (Levy Type II). What biomechanical factor of the rTSA construct most significantly contributed to this complication?

. Superior positioning of the glenosphere
. Medialization of the center of rotation
. Excessive lengthening of the humerus (increased deltoid tension)
. Undersizing of the humeral stem
. Use of a cemented humeral stem

Correct Answer & Explanation

. Excessive lengthening of the humerus (increased deltoid tension)

Explanation

Acromial stress fractures after rTSA occur due to the altered biomechanics and increased tension on the deltoid, which originates on the acromion. Excessive distalization (lengthening of the humerus) significantly increases deltoid resting tension, placing a high load on the acromion and increasing the risk of a stress fracture. Other factors include superior screw placement in the base of the acromion or severe osteoporosis.

Question 55

Topic: Shoulder Arthroplasty & Arthritis

To minimize the risk of scapular notching in reverse total shoulder arthroplasty (RTSA), how should the glenosphere baseplate optimally be positioned?

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

Correct Answer & Explanation

. Inferior translation and inferior tilt

Explanation

Scapular notching is a well-known complication of RTSA resulting from mechanical impingement of the humeral component against the inferior scapular neck during arm adduction. Positioning the glenosphere with inferior translation (overhanging the inferior rim) and inferior tilt alters the biomechanics to increase the impingement-free range of motion and drastically reduces the incidence of notching.

Question 56

Topic: Shoulder Arthroplasty & Arthritis

In reverse total shoulder arthroplasty (RTSA), scapular notching is a recognized complication. Which of the following surgical techniques or implant designs is most effective in minimizing the incidence of inferior scapular notching?

. Superior inclination of the glenosphere
. Placement of the baseplate with superior tilt
. Inferior placement of the baseplate with glenosphere overhang
. Decreasing the humeral neck-shaft angle to 135 degrees without lateralization
. Using a smaller diameter glenosphere

Correct Answer & Explanation

. Superior inclination of the glenosphere

Explanation

Inferior placement of the baseplate with an inferior glenosphere overhang of 2 to 4 mm significantly reduces the risk of scapular notching. This position limits the mechanical impingement of the medial humeral cup against the scapular neck during adduction.

Question 57

Topic: Shoulder Arthroplasty & Arthritis

A 75-year-old female sustains a displaced 4-part proximal humerus fracture.

Which of the following is the most important biomechanical and clinical factor favoring reverse total shoulder arthroplasty (RTSA) over hemiarthroplasty in this scenario?

. The presence of an intact and functioning rotator cuff
. The high predictability of greater tuberosity healing with hemiarthroplasty
. The preservation of the coracoacromial arch
. The decreased reliance on tuberosity healing for forward elevation with RTSA
. The inherent risk of axillary nerve neuropraxia with hemiarthroplasty

Correct Answer & Explanation

. The decreased reliance on tuberosity healing for forward elevation with RTSA

Explanation

RTSA is increasingly preferred over hemiarthroplasty for displaced 3- and 4-part proximal humerus fractures in the elderly because forward elevation is driven by the deltoid muscle rather than the rotator cuff. Hemiarthroplasty heavily relies on predictable healing of the greater and lesser tuberosities in their anatomic positions for a good functional outcome; tuberosity nonunion or malunion frequently leads to pseudoparalysis. RTSA circumvents this unpredictability.

Question 58

Topic: Shoulder Arthroplasty & Arthritis

In a reverse total shoulder arthroplasty (RTSA) performed for cuff tear arthropathy, what is the primary biomechanical advantage conferred by the implant design?

. Medialization and inferiorization of the center of rotation, which increases the deltoid moment arm
. Lateralization and superiorization of the center of rotation, which tension the remaining rotator cuff
. Medialization and superiorization of the center of rotation to restore the anatomic joint line
. Lateralization and inferiorization of the center of rotation to increase the subacromial space
. Preservation of the anatomic center of rotation while constraining the joint

Correct Answer & Explanation

. Medialization and inferiorization of the center of rotation, which increases the deltoid moment arm

Explanation

The Grammont design of the reverse total shoulder arthroplasty (RTSA) medializes and inferiorizes the center of rotation. Inferiorization increases the resting tension of the deltoid, and medialization increases the deltoid moment arm (specifically the middle and posterior heads) by moving the center of rotation closer to the deltoid tuberosity line of pull. This allows the deltoid to effectively elevate the arm in the absence of a functional rotator cuff.

Question 59

Topic: Shoulder Arthroplasty & Arthritis

A 72-year-old female undergoes a reverse total shoulder arthroplasty (rTSA). To minimize the risk of inferior scapular notching, how should the glenosphere baseplate be optimally positioned?

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

Correct Answer & Explanation

. Inferior tilt and inferior translation

Explanation

Scapular notching is a common complication of rTSA, particularly with Grammont-style implants, where the humeral component abuts the inferior scapular neck. To minimize this, biomechanical and clinical studies recommend placing the baseplate (glenosphere) with inferior translation (overhanging the inferior glenoid rim by 2-4mm) and inferior tilt (approximately 10-15 degrees). This allows the humeral cup to clear the inferior scapular neck during adduction.

Question 60

Topic: Shoulder Arthroplasty & Arthritis

A 70-year-old male presents 3 months after an anatomic total shoulder arthroplasty with an acute loss of active internal rotation and anterior instability. Imaging confirms a complete, retracted subscapularis failure. What is the most reliable definitive surgical treatment?

. Direct primary repair of the subscapularis
. Pectoralis major tendon transfer
. Revision to reverse total shoulder arthroplasty
. Achilles tendon allograft reconstruction
. Arthroscopic superior capsule reconstruction

Correct Answer & Explanation

. Direct primary repair of the subscapularis

Explanation

Complete subscapularis failure after anatomic TSA leads to anterior instability and significant dysfunction. Revision to a reverse total shoulder arthroplasty (rTSA) provides the most reliable outcome, as direct repairs or tendon transfers in this setting have unacceptably high failure rates.

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