The hybrid glenoid - is this innovation of value?

 Hybrid Glenoid Designs in Anatomic Total Shoulder Arthroplasty:A Systematic Review 

Hybrid glenoid components have been designed with the aim of combining the initial stability provided by cementing a polyethylene component with the long-term potential of biologic fixation through ongrowth of metal components. These components are marketed in the hope that they will provide better clinical outcomes and lower revision rates than standard all polyethylene glenoid components in total shoulder arthroplasty (TSA) 

These authors sought to systematically review the literature for studies that assessed outcomes of TSA performed using hybrid glenoid components. 

Their hypothesis was that hybrid glenoid components offered greater initial stability and had lower complication rates than all-polyethylene and metal-backed glenoid components.

They found seven studies with 593 shoulders for inclusion in this review. The mean age of patients was 65 ± 1 years, and 46% of the population was male. Mean follow-up was 50 months (4.2 years). 

The overall complication rate was 7% and rate of revision was 2.5%; glenoid radiolucency was present in 33% of shoulders at mean follow-up of 50 months. 

Mean improvements in forward elevation, external rotation, internal rotation score, and abduction were 49°, 28°, 2 points, and 42°, respectively. Mean improvements in Constant, American Shoulder and Elbow Surgeons (ASES), and University of California, Los Angeles (UCLA) scores were 36 points,

52 points, and 17 points, respectively.

The rate of complications was reported by 6 studies with a total of 548 shoulders. Complications occurred in 38 shoulders giving an overall complication rate of 7%. The most common complications were rotator cuff tears in 6 shoulders (1%) and infection in 5 shoulders (1%). Regarding complications specifically related to the glenoid component, glenoid aseptic loosening and glenoid fracture each occurred in 4 shoulders (0.7%). There was 1 case of the polyethylene component shearing off the post at the screw-in mechanism. Other complications included articular surface dissociation, postoperative pain, nerve injuries, clavicular fractures, aseptic humeral loosening, acromioclavicular joint injuries, and hematomas.

Five studies with radiographic follow-up for 351 shoulders reported the percentage of

shoulders with radiolucency. Of these shoulders, 33% had some degree of radiolucency.

There were 15 reported revisions in this review resulting in an overall rate of revision of 2.5%. The reasons for revision were aseptic glenoid loosening (4), articular surface dissociation (8), posterior instability (1), glenoid fractures (3) rotator cuff tear plus polyethylene wear (1), and 1 case of the polyethylene component shearing off the post at the base of the screw-in mechanism.

Three cohort studies compared TSA performed with hybrid glenoid components and all polyethylene glenoid components; all found that improvements in ROM and patient-reported outcome scores were not inferior to those found in all-polyethylene glenoid components

Comment: This is an interesting review of the hybrid glenoid. 

The article points out that the hybrid glenoid has some unique failure modes not seen with conventional all-polyethylene glenoid components: articular surface dissociation, shearing of the poly off the post, and glenoid fracture.

It appears that the authors' did not find evidence to support the hypothesis " that hybrid glenoid components offered greater initial stability and had lower complication rates than all-polyethylene and metal-backed glenoid components." 

Here are a few articles related to hybrid glenoids: 

Uncemented fixation of a monoblock ingrowth polyethylene glenoid: early follow-up

These authors reviewed their experience with uncemented fixation of a hybrid cage monoblock
polyethylene glenoid component in 51shoulders with a minimum follow-up of 2 years. 

Twelve glenoid components (24%) had radiolucent lines. Glenoid lines were rated grade 1,grade 2, and grade 5 (6, 4, and 2 shoulders, respectively). Six shoulders (12%) had humeral lucent lines. Two shoulders (4%) underwent reoperation, only 1 of these occurring due to isolated failure of the glenoid component. As a group, mean ROM and PROMs improved significantly compared with preoperative values and exceeded the minimal clinically important difference.

One patient had failure of the glenoid after a motorcycle accident

Comment: The clinical and radiographic outcomes of this glenoid do not appear to be superior to those with a standard all-polyethylene glenoid component.

See below for a discussion of another recent paper describing the use of this component.

Clinical and radiographic comparison of a hybrid cage glenoid to a cemented polyethylene glenoid in anatomic total shoulder arthroplasty

These authors report the clinical and radiographic outcomes of 316 Exactech hybrid cage glenoids below left) to an age-matched, sex-matched, and follow-up–matched cohort of 316 Exactech cemented all polyethylene glenoid (below right) in patients undergoing anatomic total shoulder arthroplasty with 2 years’ minimum follow-up.

The Exactech cage glenoid patients had significantly lower rates of radiolucent glenoid lines (9.0% vs. 37.6%, P < .0001) and radiolucent humeral lines (3.0% vs. 9.1%, P . .0088) than the Exactech all-polyethylene peg glenoid patients. In the cage glenoid cohort, 4 cases of aseptic glenoid loosening (1.3%) and 4 cases of articular surface dissociation (1.3%) occurred as shown below.

In the all-polyethylene peg cohort, 12 cases of aseptic loosening (3.8%) occurred. Cage glenoid patients had a significantly lower revision rate than all-polyethylene peg glenoid patients (2.5% vs. 6.9%, P . .0088).

Comment: These authors point out the importance of exact alignment of the drilled holes and the direction of impaction required by the metal-coated  pegs.

The required direction and accuracy may be difficult to achieve because of challenges with exposure, especially in retroverted glenoids.

Failure to achieve the desired alignment of the holes with the reamed bony surface can result in failure of the component as shown below.

In contrast to the all-polyethylene component with smooth pegs used in this study, we prefer a component with a fluted central peg.

This component has several advantages, including (1) the flexibility of the pegs that can better accommodate minor degrees of malalignment in comparison to the more rigid hybrid pegs and (2) the fluted central peg that allows bone ingrowth which cannot occur with the smooth pegs used in this study.

To see a YouTube of our technique for total shoulder arthroplasty, click on this link.

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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)

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).

Shoulder rehabilitation exercises (see this link).

The hybrid cage glenoid - is it of value?

Uncemented fixation of a monoblock ingrowth polyethylene glenoid: early follow-up

These authors reviewed their experience with uncemented fixation of a hybrid cage monoblock
polyethylene glenoid component in 51shoulders with a minimum follow-up of 2 years. 

Twelve glenoid components (24%) had radiolucent lines. Glenoid lines were rated grade 1,grade 2, and grade 5 (6, 4, and 2 shoulders, respectively). Six shoulders (12%) had humeral lucent lines. Two shoulders (4%) underwent reoperation, only 1 of these occurring due to isolated failure of the glenoid component. As a group, mean ROM and PROMs improved significantly compared with preoperative values and exceeded the minimal clinically important difference.

One patient had failure of the glenoid after a motorcycle accident

Comment: The clinical and radiographic outcomes of this glenoid do not appear to be superior to those with a standard all-polyethylene glenoid component.

See below for a discussion of another recent paper describing the use of this component.

Clinical and radiographic comparison of a hybrid cage glenoid to a cemented polyethylene glenoid in anatomic total shoulder arthroplasty

These authors report the clinical and radiographic outcomes of 316 Exactech hybrid cage glenoids below left) to an age-matched, sex-matched, and follow-up–matched cohort of 316 Exactech cemented all polyethylene glenoid (below right) in patients undergoing anatomic total shoulder arthroplasty with 2 years’ minimum follow-up.

The Exactech cage glenoid patients had significantly lower rates of radiolucent glenoid lines (9.0% vs. 37.6%, P < .0001) and radiolucent humeral lines (3.0% vs. 9.1%, P . .0088) than the Exactech all-polyethylene peg glenoid patients. In the cage glenoid cohort, 4 cases of aseptic glenoid loosening (1.3%) and 4 cases of articular surface dissociation (1.3%) occurred as shown below.

In the all-polyethylene peg cohort, 12 cases of aseptic loosening (3.8%) occurred. Cage glenoid patients had a significantly lower revision rate than all-polyethylene peg glenoid patients (2.5% vs. 6.9%, P . .0088).

Comment: These authors point out the importance of exact alignment of the drilled holes and the direction of impaction required by the metal-coated  pegs.

The required direction and accuracy may be difficult to achieve because of challenges with exposure, especially in retroverted glenoids.

Failure to achieve the desired alignment of the holes with the reamed bony surface can result in failure of the component as shown below.

In contrast to the all-polyethylene component with smooth pegs used in this study, we prefer a component with a fluted central peg.

This component has several advantages, including (1) the flexibility of the pegs that can better accommodate minor degrees of malalignment in comparison to the more rigid hybrid pegs and (2) the fluted central peg that allows bone ingrowth which cannot occur with the smooth pegs used in this study.

To see a YouTube of our technique for total shoulder arthroplasty, click on this link.

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To see our new series of youtube videos on important shoulder surgeries and how they are done, click here.

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  arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Rocking horse loosening of a hybrid glenoid component

A patient presented one year after a total shoulder using a hybrid glenoid component

for glenohumeral arthritis

The postoperative films are shown below.

Over the next months the shoulder became weak, painful and anteriorly unstable, along with rocking horse loosening of the glenoid component.

Revision of this failed arthroplasty will be complicated by the glenoid bone deficiency, the need to remove the bone-ingrowth humeral component, and the fixed anterosuperior contracture.

A video of our approach to total shoulder arthroplasty can be seen by clicking this link.

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We have a new set of shoulder youtubes about the shoulder, check them out at this link.

Be sure to visit "Ream and Run - the state of the art" regarding this radically conservative approach to shoulder arthritis at this link and this link

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 arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Total shoulder arthroplasty - selecting the glenoid component

Clinical and radiographic comparison of a hybrid cage glenoid to a cemented polyethylene glenoid in anatomic total shoulder arthroplasty

These authors report the clinical and radiographic outcomes of 316 Exactech hybrid cage glenoids below left) to an age-matched, sex-matched, and follow-up–matched cohort of 316 Exactech cemented all polyethylene glenoid (below right) in patients undergoing anatomic total shoulder arthroplasty with 2 years’ minimum follow-up.

The Exactech cage glenoid patients had significantly lower rates of radiolucent glenoid lines (9.0% vs. 37.6%, P < .0001) and radiolucent humeral lines (3.0% vs. 9.1%, P . .0088) than the Exactech all-polyethylene peg glenoid patients. In the cage glenoid cohort, 4 cases of aseptic glenoid loosening (1.3%) and 4 cases of articular surface dissociation (1.3%) occurred as shown below.

In the all-polyethylene peg cohort, 12 cases of aseptic loosening (3.8%) occurred. Cage glenoid patients had a significantly lower revision rate than all-polyethylene peg glenoid patients (2.5% vs. 6.9%, P . .0088).

Comment: These authors point out the importance of exact alignment of the drilled holes and the direction of impaction required by the metal-coated  pegs.

The required direction and accuracy may be difficult to achieve because of challenges with exposure, especially in retroverted glenoids.

Failure to achieve the desired alignment of the holes with the reamed bony surface can result in failure of the component as shown below.

In contrast to the all-polyethylene component with smooth pegs used in this study, we prefer a component with a fluted central peg.

This component has several advantages, including (1) the flexibility of the pegs that can better accommodate minor degrees of malalignment in comparison to the more rigid hybrid pegs and (2) the fluted central peg that allows bone ingrowth which cannot occur with the smooth pegs used in this study.

To see a YouTube of our technique for total shoulder arthroplasty, click on this link.

=====

To see our new series of youtube videos on important shoulder surgeries and how they are done, click here.

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  arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Hybrid glenoid - possibility of stress shielding and fatigue fracture

Five-year minimum clinical and radiographic outcomes of total shoulder arthroplasty using a hybrid glenoid component with a central porous titanium post

These authors evaluated clinical and radiographic outcomes at a minimum 5-year followup in 45 shoulders that underwent total shoulder arthroplasty (TSA) using a system with a central porous titanium post to augment the cemented peripheral pegs as shown below

The mean American Shoulder and Elbow Surgeons score improved from 40.4 to 83.7 (P < .0001). Radiographs showed glenoid component radiolucency in 29 of 45 shoulders. Radiolucencies were confined to the area under the glenoid faceplate in 6 and were around the central post in 13. Nine TSAs (20%) demonstrated 2 or more columns of involvement but were not judged to be at-risk. One implant (2.2%) had glenoid component failure and was revised to a hemiarthroplasty. 

The authors point out that previous hybrid glenoid designs have manifested problems with fatigue fracture of the titanium (Results of total shoulder arthroplasty with a monoblock porous tantalum glenoid component: a prospective minimum 2-year follow-up study).

Comment: There are two potential issues with hybrid glenoid components. One is the risk of fatigue fracture - the breakage of the metal from repeated rocking forces applied to the glenoid face while the titanium peg or pegs are securely fixed to the bone of the glenoid. The second is the risk of stress shielding that arises because the titanium is stiffer than bone and polyethylene. Just as in the case of stress shielding in humeral component fixation, when the metal is stiffer than the bone in which it is inserted, the unloaded bone tends to lose mineral. Loss of bone beneath the polyethylene face of the component can give rise to increased rocking of the component with increased risk of fatigue fracture of the metal.

The reader may wish to look at these links regarding Young's Modulus for bone, titanium, and polyethylene. Correlation between Young's Modulus and Porosity in Porous Materials  and Young's Modulus for Some Common Materials and Microstructure and Mechanical Properties of Porous Titanium Based on Controlling Young’s Modulus

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The reader may also be interested in these posts:

Healing through joint replacement

Supporting progress in shoulder surgery

Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book.

Click here to see the new Rotator Cuff Book

Information about shoulder exercises can be found at this link.

Use the "Search" box to the right to find other topics of interest to you.

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'

See from which cities our patients come.

See the countries from which our readers come on this post.

Failed total shoulder, difficult revision

One year after a total shoulder arthroplasty, this patient presented with a draining right shoulder wound, a red arm, and a painful shoulder

 and these x-rays showing glenoid osteolysis, a fractured hybrid fixation peg and stress shielding of the upper humerus with a bone-ingrowth press fit humeral stem.

At surgery, the sinus track was excised along with chronic inflammatory tissue. Frozen sections were negative for white cells.

The retrieved glenoid showed a fractured peg

The portion of the peg remaining in the glenoid was removed with a trephine.

Removal of the humeral component was difficult because of the tight diaphysial fit and the fragile osteopenic metaphyseal bone.

A cement spacer was inserted because of the suspicion of infection.

The patient will be placed on the 'red' protocol of IV antibiotics until the cultures are finalize.

This case demonstrates (1) the ever present risk of infection in shoulder arthroplasty, (2) the susceptibility of fatigue fracture of a metal post, (3) the problems created by a tight press-fit bone ingrowth stem should prosthesis removal become necessary.

The potential for fatigue fracture of a hybrid post has been shown in a recent article

Five-year minimum clinical and radiographic outcomes of total shoulder arthroplasty using a hybrid glenoid component with a central porous titanium post.

Here is a radiograph from that article.

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The reader may also be interested in these posts:

Healing through joint replacement

Supporting progress in shoulder surgery

Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book.

Click here to see the new Rotator Cuff Book

Information about shoulder exercises can be found at this link.

Use the "Search" box to the right to find other topics of interest to you.

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'

See from which cities our patients come.

See the countries from which our readers come on this post.

Acute failure of a hybrid glenoid component

Acute Failure of a Glenoid Component in Anatomic Shoulder Arthroplasty.


The authors remind us that glenoid loosening is the most common cause of failure in primary total shoulder arthroplasty and often occurs years after the initial surgery. In this case report, they present an unrecognized acute failure of a cemented hybrid glenoid component.

The patient was a 65-year-old man with persistent right shoulder pain and severely restricted range of motion approximately 10 months after a primary anatomic total shoulder performed for longstanding severe osteoarthritis with an intact cuff. The shoulder system was used for the index procedure included pegged, caged glenoid.

A CT arthrogram was ordered to evaluate if there was a rotator cuff tear but instead found that the glenoid component had dissociated and was sitting posterior to the humeral head .  The polyethylene glenoid component had disengaged from its metallic cage. One of the three metallic peg caps remained seated in the glenoid. 

Close inspection of the postoperative films, as early as those immediately following surgery in the postanesthesia care unit, confirmed that the glenoid had failed acutely.

At revision surgery, the glenoid component was retrieved from the posterior capsule. The component failure was seen to have occurred at the interface between one of the pegs and its metallic cap as well as at the cage component, which had disengaged from the polyethylene.

The authors point out that there have been prior recognized failures of this central cage locking mechanism. They suggest that this component requires “straight line” glenoid impaction, directly perpendicular to the face of the glenoid to prevent damage to the locking mechanism of the central peg as it engages the drilled hole. Failure to do so may disengage the central peg from the polyethylene.

Comment: This is points that each implant system has its particular features and that these need to be understood by the surgeon.

In our practice we use an all polyethylene component

our total shoulder arthroplasty is shown in this link.

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Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book.

Click here to see the new Rotator Cuff Book

Use the "Search" box to the right to find other topics of interest to you.

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'

See from which cities our patients come.

See the countries from which our readers come on this post.