Lateralized reverse total shoulder: abduction damage to the acromion

Lateralization of a reverse total shoulder is used by some surgeons with the goal of enhancing stability, improving strength, and reducing scapular notching.

One of the potential drawbacks of this approach is unwanted contact between the tuberosity and the undersurface of the acromion when the arm is abducted.

The authors of Subacromial notching after reverse total shoulder arthroplasty suggest that damage to the acromion may be caused by abduction impingement after reverse total shoulder arthroplasty (RSA) with a lateralized design. They reviewed the medical records of 125 patients who underwent RSA with the design shown below

They defined subacromial notching (SaN) as subacromial erosion observed at the final follow-up but not on the X-ray three months after surgery. They found that SaN occurred in 12.8% (16/125) of enrolled patients. Greater postoperative humeral lateralization offset (HL) was a risk factor for subacromial notching.

The VAS and ASES scores at the final follow-up were significantly worse in patients with subacromial notching. 

Comment: Contact between the greater tuberosity and the acromion can limit the range of abduction and can weaken the acromion.

On AP radiographs it is straightforward to see the risk of acromion-tuberosity contact. 

First, fit a circle to the glenosphere

then draw a line segment from the center of the glenosphere to the tip of the tuberosity

finally draw a second line segment of the same length from the glenosphere center to the acromion and note whether there would be contact in abduction.

Of course it is desirable to check for this unwanted contact while surgical the incision is still open. This can be simply done by abducting the arm to see if the tuberosity clears the acromion. If it does not, it may be possible to avoid unwanted contact by shaving bone from the tuberosity. If this is insufficient, the surgeon can consider modifying the implant or its position.

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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).

Reverse total shoulder - does geometry affect the outcome ? Part 2

In a prior post, What determines the outcome of reverse total shoulder arthroplasty - does geometry matter?, a substantial amount of evidence was presented showing a lack of correlation between clinical outcomes and radiographic measurements after reverse total shoulder arthroplasty (RSA). In a recent study, the authors of Radiographic and anatomic variations on postoperative acromion fractures after inlay and lateralized reverse shoulder arthroplasty attempted to identify associations between the occurrence of acromial fractures after RSA and the relative humeral and glenoid positioning as well as the geometry of the acromioclavicular (AC) joint .

Of a total of 920 RSAs performed, 47 (5.1%) patients suffered a postoperative acromion fracture. Patients with a postoperative acromion fracture were matched in a 3:1 ratio based on sex, indication, and age to those without a fracture and with a 2-year minimum follow-up.

Preoperative and the immediate postoperative radiographs were reviewed to measure critical shoulder angle (A), delta angle (B), global lateralization (C), acromion-humeral interval (D), the level of inlay or onlay of the humeral stem (E) and the preoperative glenoid height.

The morphology, width, and stigmata of osteoarthritis in the AC joint were assessed using computed tomography scans taken preoperatively.

The authors found no significant differences between the fracture and nonfracture groups with respect to the critical shoulder angle, acromion-humeral interval, global lateralization, delta angle both preoperatively and postoperatively, preoperative glenoid height, postoperative degree of inset or offset of humeral implant relative to the anatomic neck, and AC joint morphology, joint space, and stigma of osteoarthritis.

Comment: In the absence of associations among preoperative and postoperative radiographic findings and postoperative acromion fractures, other risk factors such as osteoporosis, inflammatory arthropathy, chronic dislocations, and rotator cuff tear arthropathy may be more important in the pathogenesis of acromion fractures.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

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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).

Scapular spine and acromial fractures after reverse total shoulder - which ones might best be left alone?

Nonoperative Treatment of Acromial Fractures Following Reverse Shoulder Arthroplasty: Clinical and Radiographic Outcomes

These authors reported on clinical and radiographic outcomes of nonoperative treatment of acromial and scapular spine fractures (ASF) after reverse total shoulder arthroplasty. 

44 patients diagnosed with ASF following RSA were matched 1:3 to a control group based upon gender, age, and preoperative function. 

ASF were identified at a median of 2 months and were followed for a median of 37 months. All ASF patients were treated nonoperatively.

Overall, patients with ASF had inferior clinical outcomes with a higher rate of dissatisfaction when compared to controls. 

Lateral fracture subtypes (I and IIA) were similar to controls and had little impact on outcomes. 

Medial fracture subtypes (Type-IIB, IIC, and III) demonstrated inferior outcomes when compared to controls, with Type-III fracture patients demonstrating no improvement from baseline. 

The overall non-union rate was 61.4%, with high rates of scapular rotation and osteolysis in medial fracture subtypes. Nonunion was associated with a higher incidence of secondary radiographic findings, including scapular rotation, progressive notching, and osteolysis.

The authors concluded that fractures which occur at or medial to the glenoid face demonstrated high rates of unsatisfactory results and worse clinical outcomes as well as increased rates of scapular tilt, progressive scapular notching and osteolysis

Comment: For good reason, there has been substantial interest in the prevention, diagnosis and treatment of acromial and spine fractures after reverse total shoulder arthroplasty. It seems that the symptoms from these fractures are related both to the location of the fracture and the amount of displacement.

Here's a case: a middle aged man had a reverse total shoulder after multiple failed cuff repairs of the left shoulder. At the six week checkup, all was well clinically and radiographically.

He started gentle assisted flexion exercises. Two days after the office visit while reaching up he had sudden pain in the shoulder and heard a 'crack'. He returned to the office at which time tenderness was noted at the posterior acromion. The AP view was not remarkable.

However, the axillary view showed a non-displaced crack in the acromion.

This case reveals the potential of fracture of an acromion that is not used to being loaded.

Here's another case:
An 85 year old lady presented with severe cuff tear arthropathy as shown below.

She had a reverse total shoulder in early 2012. Two years after surgery she had excellent comfort and function. An axillary x-ray at that point is shown below.

Three and a half years after her procedure she developed the atraumatic onset of posterior shoulder pain. Her axillary x-ray shows a fatigue fracture of the scapular spine (to the left of the red line).

These minimally displaced fractures healed with non operative management.

Research is ongoing to determine the effect of prosthesis type and position that influence the risk of these fractures.

However, the type of patient at greatest risk is becoming clearer:

Patient risk factors for acromial stress fractures after reverse shoulder arthroplasty: a multicenter study

These authors investigated the incidence of acromial stress fractures (ASFs) after reverse total shoulder and and sought to identify preoperative patient characteristics associated with their occurrence.

They identified 1479 patients undergoing either primary or revision RTSA between 2013 and 2018 with minimum 3-month follow-up. ASFs were defined as radiographic evidence of an acromial or scapular spine fracture with clinical symptoms (eg, tenderness over the acromion or scapular spine). 

Overall, 54 (3.7%) patients were diagnosed with an ASF after RTSA. Patient-related factors independently associated with the development of an ASF included female sex, rheumatoid arthritis, osteoporosis, a diagnosis of degenerative joint disease with rotator cuff tear, and fracture malunion/nonunion (OR, 5.21; 95% CI, 1.20-22.76; P < .05).

This is an interesting study, although the followup time is short. Many acromial fractures occur more than 3 months after surgery.

The article below dives a bit deeper into the local changes in scapular bone density associated with age and sex.

Changes in Scapular Bone Density Vary by Region and are Associated with Age and Sex

They studied 97 three-dimensional models of the scapula that were segmented from routine clinical computed tomography (CT) scans, and obtained detailed calibrated bone density measurements for each bone model. The effects of age and sex on cortical and trabecular bone density were assessed for the entire scapula.

They found that cortical bone loss averaged to 1.0 mg/cc and 0.3 mg/cc per year. 

Trabecular bone loss was 1.6 mg/cc and 1.2 mg/cc for female and males respectively. 

Areas that were significantly affected by age included the acromion, the scapular spine, the base of the coracoid, the inferior glenoid neck as well as the glenoid vault. 

Areas that were significantly affected by sex were the scapular spine and body. These findings are consistent with the risk factors for acromial and scapular spine fractures after reverse total shoulder.

Here are some other links relating to acromial and scapular spine fractures after reverse total shoulder: link 1, link 2, link 3, link 4, link 5 and this link.

Follow on twitter: https://twitter.com/shoulderarth

Follow on facebook: https://www.facebook.com/frederick.matsen

Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

Shoulder arthritis - x-ray appearance (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Acromial and spine fractures after reverse total shoulder

There has been substantial interest in the prevention, diagnosis and treatment of acromial and spine fractures after reverse total shoulder arthroplasty. 

Here's a case: a middle aged man had a reverse total shoulder after multiple failed cuff repairs of the left shoulder. At the six week checkup, all was well clinically and radiographically.

He started gentle assisted flexion exercises. Two days after the office visit while reaching up he had sudden pain in the shoulder and heard a 'crack'. He returned to the office at which time tenderness was noted at the posterior acromion. The AP view was not remarkable.

However, the axillary view showed a non-displaced crack in the acromion.

This case reveals the potential of fracture of an acromion that is not used to being loaded.

Here's another case:
An 85 year old lady presented with severe cuff tear arthropathy as shown below.

She had a reverse total shoulder in early 2012. Two years after surgery she had excellent comfort and function. Here x-rays at that point are shown below.

Three and a half years after her procedure she developed the atraumatic onset of posterior shoulder pain. Her axillary x-ray shows a fatigue fracture of the scapular spine (to the left of the red line).

We anticipate that these will heal with non operative management.

Here are a couple of recent relevant articles.

Patient risk factors for acromial stress fractures after reverse shoulder arthroplasty: a multicenter study

These authors investigated the incidence of acromial stress fractures (ASFs) after reverse total shoulder and and sought to identify preoperative patient characteristics associated with their occurrence.

They identified 1479 patients undergoing either primary or revision RTSA between 2013 and 2018 with minimum 3-month follow-up. ASFs were defined as radiographic evidence of an acromial or scapular spine fracture with clinical symptoms (eg, tenderness over the acromion or scapular spine). 

Overall, 54 (3.7%) patients were diagnosed with an ASF after RTSA. Patient-related factors independently associated with the development of an ASF included female sex, rheumatoid arthritis, osteoporosis, a diagnosis of degenerative joint disease with rotator cuff tear, and fracture malunion/nonunion (OR, 5.21; 95% CI, 1.20-22.76; P < .05).

Comment: This is an interesting study, although the followup time is short. Many acromial fractures occur more than 3 months after surgery (see this link).

The article below dives a bit deeper into the local changes in scapular bone density associated with age and sex.

Changes in Scapular Bone Density Vary by Region and are Associated with Age and Sex

They studied 97 three-dimensional models of the scapula that were segmented from routine clinical computed tomography (CT) scans, and obtained detailed calibrated bone density measurements for each bone model. The effects of age and sex on cortical and trabecular bone density were assessed for the entire scapula.

They found that cortical bone loss averaged to 1.0 mg/cc and 0.3 mg/cc per year. 

Trabecular bone loss was 1.6 mg/cc and 1.2 mg/cc for female and males respectively. 

Areas that were significantly affected by age included the acromion, the scapular spine, the base of the coracoid, the inferior glenoid neck as well as the glenoid vault. 

Areas that were significantly affected by sex were the scapular spine and body.

Comment: These findings are consistent with the risk factors for acromial and scapular spine fractures after reverse total shoulder.

Here are some other links relating to acromial and scapular spine fractures after reverse total shoulder: link 1, link 2, link 3, link 4, and link 5.

 How you can support research in shoulder surgery Click on this link.

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 total shoulder arthroplasty (see this link).

The ream and run technique is shown in 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).

Scapular fractures after reverse total shoulder arthroplasty

 Predictors of Acromial and Scapular Stress Fracture after Reverse Shoulder Arthroplasty: An ASES Multicenter Study from the Complications of Reverse Arthroplasty Group

These authors point out that acromial (ASF) and scapular spine (SSF) stress fractures are well-recognized complications of reverse shoulder arthroplasty (RSA).

They conducted a 15 center study to determine the incidence of ASF/SSF after RSA, and the preoperative patient characteristics associated with their occurrence.

They included patients undergoing either primary or revision RSA with a minimum three-month follow-up. Only symptomatic ASF/SSF diagnosed by radiograph or computed tomography were considered. 

They identified 6,755 RSAs with an average follow-up of 19.8 months (range, 3-94). About 1 in 26 patients undergoing RSA developed a symptomatic ASF or SSF, usually within the first year of surgery. The total scapular fracture incidence rate was 3.9% (n=264), of which 3.0% (n=200) were ASF and 0.9% (n=64) were SSF. 

Fractures occurred at an average 8.2 months (0-64) following RSA with 21.2% (n=56) following a trauma. 

Patient-related factors independently predictive of ASF were: chronic dislocation (OR, 3.67), massive rotator cuff tear without arthritis (OR, 2.51), rotator cuff arthropathy (OR, 2.14), self-reported osteoporosis (OR, 2.21), inflammatory arthritis (OR, 2.18), female sex (OR, 1.51), and older age (OR, 1.02 per 1-year increase). 

Factors independently associated with the development of SSF included: osteoporosis (OR, 2.63), female sex (OR, 2.34), rotator cuff arthropathy (OR, 2.12), and inflammatory arthritis (OR, 2.05).

The authors did not report on the relationship of prosthesis type or positioning on ASF or SSF.

Comment: This is an important study in that it points out the typical time of presentation of ASF and SSF and the risk factors for these complications that can be devastating for the patient.

Surgeons and patients may wish to consider alternative methods of management of rotator cuff arthropathy (see this link) and massive cuff tear (see this link) in high risk patients.

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How you can support research in shoulder surgery Click on this link.

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).

Complication of reverse total shoulder: acromial and scapular spine fracture

Acromial spine fracture after reverse total shoulder arthroplasty: a systematic review


These authors performed a systematic review of the literature to analyze the occurrence and outcomes of acromial and spine fractures after reverse total shoulder (RSA).

Among 3838 RSAs, 159 acromial fractures were reported, for an overall incidence of 4.14%; the mean time to diagnosis from surgery was 9 months (range, 1.3-24 months). 

Regardless of treatment, patients reported inferior function after fracture compared with their function immediately after RSA. 

Forward flexion was 95° (range, 30°-110°), abduction was 76° (range, 30°-180°), the Constant score was 63 (range, 59-67.5), and the American Shoulder and Elbow Surgeons score was 57 (range, 7-83); all values were reduced compared with patients without fractures.

This study suggests the occurrence of acromial fractures after RSA is a common event, with a rate of over 4%. These fractures correlate with worse postoperative outcomes regardless of treatment method; open reduction–internal fixation was not shown to be clinically superior despite a limited complication rate.

Comment: This article points to the frequency of this complication, which is not seen with other types of shoulder arthroplasty. It does not, however, discuss the factors other than osteoporosis that may contribute to acromial and spine fractures, such as over lengthening, screw placement, and activity level. For more information see this link, this link, and this link.
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When is the acromion likely to break after a reverse total shoulder?

Acromial Fractures in Reverse Shoulder Arthroplasty: A Clinical and Radiographic Analysis

The authors reviewed 12 patients diagnosed with a postoperative acromial stress fracture after a reverse total shoulder and compared them to a case matched control group of 48 shoulders having reverse total shoulders but no fracture.  The rate of acromial fracture in this series was 1.11%. Compared to controls, patients with fractures were less satisfied with their outcome.

Only 1 of the 12 fractures had a history of direct trauma, while the 11 others were considered stress fractures. The mean time from surgery to fracture diagnosis was 9 months (range, 2–38 months). Five (42%) occurred less than 3 months after surgery, 3 (25%) from 3 to 6 months after surgery, 1 (8%) from 6 to 12 months, 1 (8%) between 1 and 2 years, and 2 (17%) occurred greater than 2 years postoperatively. 

 Four (33%) of the fractures were displaced.

Osteoporosis,  smaller lateral offset of the greater tuberosity, greater arm lengthening, and a thinner acromion were more common in the fracture group.

The authors concluded that the combination of a thin acromion and superior migration of the humeral head increase the risk of acromial fracture.
Comment: It is apparent that the quality of the acromial bone prior to a reverse total shoulder is likely to be diminished by wear, disuse local osteopenia, and systemic osteoporosis.  A reverse total shoulder dramatically increases the loads on the acromion by restoring use and by increasing the static and dynamic tension on the deltoid origin. Indeed it is surprising that these stress fractures are not recognized more often.

The observations in article suggest that surgeons performing reverse total shoulders should warn their patients of this possible event and it should be suspected with the onset of posterior scapular or acromial area complaints of pain. Surgeons may also wish to avoid excessive deltoid tension when implanting a reverse total shoulder, especially in patients at increased risk.
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Use the "Search" box to the right to find other topics of interest to you. 

How you can support progress in shoulder surgery

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

A sudden 'crack' after a reverse total shoulder.

A middle aged man had a reverse total shoulder after multiple failed cuff repairs of the left shoulder. At the six week checkup, all was well clinically and radiographically.

He started gentle assisted flexion exercises. Two days after the office visit while reaching up he had sudden pain in the shoulder and heard a 'crack'. He returned to the office at which time tenderness was noted at the posterior acromion. The AP view was not remarkable.

However, the axillary view showed a non-displaced crack in the acromion.

This case reveals the potential of fracture of an acromion that is not used to being loaded.

Here's a similar case:
An 85 year old lady presented with severe cuff tear arthropathy as shown below.

She had a reverse total shoulder in early 2012. Two years after surgery she had excellent comfort and function. Here x-rays at that point are shown below.

Three and a half years after her procedure she developed the atraumatic onset of posterior shoulder pain. Her axillary x-ray shows a fatigue fracture of the scapular spine (to the left of the red line).

We anticipate that these will heal with non operative management.

Comment: It is worthwhile informing patients of this risk and advising a slow return to activities after a reverse total shoulder.

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You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, reverse total shoulder patient information,  CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

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