What is the value of posteriorly augmented glenoid components?

Augmented glenoid implants in anatomic total shoulder arthroplasty: review of available implants and current literature

These authors point out that although eccentric reaming, augmented glenoid implants, bone grafting, and reverse arthroplasty have been used to manage bone loss and retroversion, there is no consensus on treatment.

Posteriorly augmented glenoid components (full-wedged, half-wedged, and stepped polyethylene posteriorly) are currently available for use in the United States. 

Most clinical studies on augmented implants are case series, typically reported by the designers or consultants associated with the specific implant. 

Some reports show increased radiolucency and failure rates when posteriorly augmented glenoids are used.

With studies with low levels of evidence, small numbers of patients, and short-term followup periods, the theoretically superior results of stepped implants and wedged implants in comparison with traditional methods using conventional glenoid components have not been shown.

Comment: From this review, we cannot determine the indications for or the incremental clinical value to patients of augmented glenoid components.  

Furthermore, as shown in the article below, it is not clear how much "correction" of glenoid retroversion is  necessary in practice:

Does Postoperative Glenoid Retroversion Affect the 2-Year Clinical and Radiographic Outcomes for Total Shoulder Arthroplasty?


While glenoid retroversion and posterior humeral head decentering are common preoperative features of severely arthritic glenohumeral joints, the relationship of postoperative glenoid component retroversion to the clinical results of total shoulder arthroplasty (TSA) is unclear. Studies have indicated concern for inferior outcomes when glenoid components are inserted in 15° or more retroversion.

In a population of patients undergoing TSA in whom no specific efforts were made to change the version of the glenoid, these authors asked whether at 2 years after surgery patients having glenoid components implanted in 15° or greater retroversion had (1) less improvement in the Simple Shoulder Test (SST) score and lower SST scores; (2) higher percentages of central peg lucency, higher Lazarus radiolucency grades, higher mean percentages of posterior decentering, and more frequent central peg perforation; or (3) a greater percentage having revision for glenoid component failure compared with patients with glenoid components implanted in less than 15° retroversion. They examined the records of  201 TSAs performed using a standard all-polyethylene pegged glenoid component

inserted after conservative glenoid reaming without specific attempt to modify preoperative glenoid version.

Of these, 171 (85%) patients had SST scores preoperatively and between 18 and 36 months after surgery. Ninety-three of these patients had preoperative radiographs in the database and immediate postoperative radiographs and postoperative radiographs taken in a range of 18 to 30 months after surgery. Twenty-two patients had radiographs that were inadequate for measurement at the preoperative, immediate postoperative, or latest followup time so that they could not be included. In comparison to those included in the analysis, the excluded patients did not have substantially different mean age, sex distribution, time of followup, distribution of diagnoses, American Society of Anesthesiologists class, alcohol use, smoking history, BMI,  history of prior surgery or preoperative glenoid version. They analyzed the two year outcomes in the remaining 71 TSAs, comparing the 21 in the retroverted group (the glenoid component was implanted in 15° or greater retroversion (mean ± SD, 20.7° ± 5.3°)) with the 50 in the non-retroverted group ( the glenoid component was implanted in less than 15° retroversion (mean ± SD, 5.7° ± 6.9°)). 

The mean (± SD) improvement in the SST (6.7 ± 3.6; from 2.6 ± 2.6 to 9.3 ± 2.9) for the retroverted group was not inferior to that for the nonretroverted group (5.8 ± 3.6; from 3.7 ± 2.5 to 9.4 ± 3.0). The percent of maximal possible improvement (%MPI) for the retroverted glenoids (70% ± 31%) was not inferior to that for the nonretroverted glenoids (67% ± 44%).  The 2-year SST scores for the retroverted (9.3 ± 2.9) and the nonretroverted glenoid groups (9.4 ± 3.0) were similar (mean difference, 0.2; 95% CI, - 1.1 to 1.4; p = 0.697). No patient in either group reported symptoms of subluxation or dislocation. The radiographic results for the retroverted glenoid group were similar to those for the nonretroverted group with respect to central peg lucency (four of 21 [19%] versus six of 50 [12%]; p = 0.436; odds ratio, 1.7; 95% CI, 0.4-6.9), average Lazarus radiolucency scores (0.5 versus 0.7, Mann-Whitney U p value = 0.873; Wilcoxon rank sum test W = 512, p value = 0.836), and the mean percentage of posterior humeral head decentering (3.4% ± 5.5% versus 1.6% ± 6.0%; p = 0.223). The percentage of patients with retroverted glenoids undergoing revision (0 of 21 [0%]) was not inferior to the percentage of those with nonretroverted glenoids (three of 50; [6%]; p = 0.251).

The authors concluded that in this series of TSAs, postoperative glenoid retroversion was not associated with inferior clinical results at 2 years after surgery.


Here are two other articles on this interesting topic:

Total shoulder arthroplasty in patients with a B2 glenoid addressed with corrective reaming

These authors conducted a retrospective series of consecutive patients who underwent total shoulder arthroplasty with a Walch B2 glenoid addressed using partially corrective glenoid reaming and a standard (non-augmented) cemented all-polyethylene pegged glenoid prosthesis. The mean preoperative retroversion measured 18° (range, –1° to 36°), superior inclination was 8° (range, –11° to 27°), and posterior subluxation was 67% (range, 39%-91%).There were no exclusion criteria based on radiographic severity of glenoid deformity.

Glenoid deformities were addressed using a high side, corrective ream with the goal of achieving an estimated minimum of 80% glenoid support and a final retroversion angle within 10° to 15° of neutral. In more severe deformities, the implant was placed slightly more retroverted in favor of excessive reaming, which would compromise glenoid fixation.

Functional outcome scores were available for 59 of 92 eligible subjects (64%) at a mean of 50 months after surgery. The Simple Shoulder Test improved from 4.5 to 9.1; the visual analog scale improved from 7.4 to 1.4, and the American Shoulder and Elbow Shoulder Standardized Assessment improved from 35.4 to 84.3. 

Radiographs were evaluated at a mean of 31 months: 38 had no glenoid radiolucent lines, 13 glenoids had grade 1, 2 had grade 2, and 5 had grade 3 lucencies. 

22.7% of shoulders with > 20° of preoperative retroversion demonstrated progression of radiolucency of at least 1 grade in the Lazarus classification. 27.8

27.8% Of the shoulders with < 20° of preoperative retroversion developed progression of at least 1 grade of radiolucency. 

No shoulders had radiographic evidence of glenoid loosening or subsidence. No patients had subjective complaints of shoulder instability.




Total shoulder arthroplasty for glenohumeral arthritis associated with posterior glenoid bone loss: results of an all-polyethylene, posteriorly augmented glenoid component

Between May 2011 and January 2013, 22 shoulders in 19 patients (15 men and 4 women) underwent primary TSA by a single surgeon. In all cases, an all-polyethylene, posteriorly augmented, stepped glenoid component was implanted.

In these cases preoperative glenoid retroversion measured 15 degrees or greater (14 of these cases had retroversion of 25 degrees or less).

At a mean follow-up of 36 months, 12 shoulders had osseous integration between the central-peg flanges, 6 had bone adjacent to the central-peg flanges but without identifiable osseous integration, and 1 showed osteolysis. 

While the overall clinical results showed improvement, two patients sustained a total of 3 episodes of humeral dislocation, one anterior and two posterior.

The authors point out that " implantation of a stepped glenoid component requires removal of some posterior bone. In glenoids in which there is both retroversion and glenoid medialization, there may be insufficient subchondral bone, volume, and/or density after preparation to support the posterior component." This is shown by the figure below.

In the osteoarthritic shoulder with posterior wear, the bone and cartilage have failed to hold up under the loads applied by the humeral head. With a posteriorly augmented glenoid component, the hope is that the thickened posterior polyethylene will be able to hold up under these same loads. 

This report shows that achieving prosthetic balance with this prosthesis can be difficult, even in the hands of an experienced surgeon.

The indications for the use of the stepped prosthesis remain to be determined. Many of the shoulders in this series had relatively low amounts of preoperative retroversion that are in the range usually managed with conventional components and soft tissue balancing.

Should this implant fail, the bone defect would be greater than that present before the arthroplasty as diagrammed below.

See also "Posterior Glenoid Wear in Total Shoulder Arthroplasty: Eccentric Anterior Reaming Is Superior to Posterior Augment" at this link.

Long term followup of well-characterized patients treated with the different methods for managing glenoid retroversion will be required to define the relative risks, benefits, effectiveness and durability of each of them.

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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'

Shoulder arthroplasty - avoiding posterior instability

Management of intraoperative posterior decentering in shoulder arthroplasty using anteriorly eccentric humeral head components 

These authors report the use of anteriorly-eccentric humeral head components to manage posterior instability recognized at shoulder arthroplasty when standard trial components are in place. Radiographic centering was characterized before surgery and at follow-up on standardized axillary radiographs with the arm held in a position of functional elevation. Preoperative posterior humeral head decentering did not correlate with preoperative glenoid version.

In 33 shoulder arthroplasties with 2-year outcomes the preoperative radiographic humeral decentering was reduced from 10.4% ± 7.9% to 0.9% ± 2.3% postoperatively (P < .001). SST scores improved from 4.8 ± 2.3 to 10.0 ± 2.3 (P < .001).  Glenoid retroversion was 19.8° ± 8.9° preoperatively and 15.5° ± 7.5° postoperatively. Rotator interval plication was performed in 16 cases as an adjunctive stabilizing procedure.

Comment: Posterior instability after a shoulder arthroplasty can result in pain, functional loss and rocking horse loosening or rim wear of a glenoid component.

While posterior decentering can be identified before surgery by the 'truth' view (an axillary taken with the arm in a functional position of elevation in the plane of the scapula) as shown below

often this preoperative posterior instability will respond to soft tissue balancing and use of standard humeral components. In other cases, the posterior instability persists at surgery, being manifest by a posterior 'drop back' when the arm is elevated. 

Not infrequently a shoulder without apparent posterior instability before surgery becomes posteriorly unstable at surgery after osteophyte resection and soft tissue releases. 

In cases where posterior instability is identified at surgery when trial components are in place, centering of the humeral head can usually be established through the use of an anteriorly eccentric humeral head without or with a rotator interval plication.

resulting in a stabilized head without needing to change glenoid version. Below is the postoperative view of the case shown in the earlier x-ray in which these methods were used.

See these related posts:

Early recovery of motion after a ream and run for severe arthritic decentering
Ream and Run for the Bad Arthritic Triad - 6 year anniversary

Ream and Run - surgical technique

The ream and run procedure for shoulder arthritis

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Issues with posteriorly agumented glenoid components

Two studies with two year followup on posteriorly augmented glenoid components are presented here.

First

Augmented glenoid component for bone deficiency in shoulder arthroplasty.

These authors report on 14 shoulders having shoulder arthroplasty with an augmented glenoid component to treat posterior glenoid bone deficiency associated with advanced osteoarthritis.

According to a modified Neer result rating system, 36% of patients had an excellent result, 50% a satisfactory result, and 14% an unsatisfactory result.

At the most recent radiographs, four of the 12 shoulders that could be evaluated radiographically had more than mild glenohumeral subluxation. Three shoulders had moderate posterior subluxation, one shoulder had severe anterior subluxation. All of the shoulders with postoperative subluxation had some degree of subluxation present prior to surgery. 

The shoulder with severe anterior subluxation postoperatively had moderate posterior subluxation prior to surgery. This patient had Parkinsonism and sustained anterior instability resulting in dislocation, treated with closed reduction, followed by immobilization and physical therapy. 

There was no periprosthetic lucency in four shoulders, periprosthetic lucency was grade 1 in seven shoulders and grade 5 in one shoulder, and the glenoid component had shifted in position. This shoulder also had moderate posterior subluxation, and this glenoid component was considered radiographically loose.

The authors concluded, "Our results suggest patients undergoing total shoulder arthroplasty with an asymmetric glenoid component for osteoarthritis achieve satisfactory mid-term pain relief and improvement in function; however, instability is not always corrected. The advantage of this component seems marginal, and its use has been discontinued."


Second
Preliminary Results of a Posterior Augmented Glenoid Compared to an all Polyethylene Standard Glenoid in Anatomic Total Shoulder Arthroplasty

These authors report on 24 patients having total shoulder arthroplasty using a posteriorly augmented glenoid for arthritis with posterior glenoid wear. The degree of posterior wear and retroversion before surgery are not presented.

At two years after surgery, 60% of the shoulders had a periglenoid radiolucent line with an average radiographic line score of 1.10.

One glenoid was radiographically loose. 

Two shoulders demonstrated superior subluxation. 

Three were anteriorly subluxated.

Comment: These results speak to the challenges inherent in the use of posteriorly augmented components.

One of the rarely discussed concerns is the effects of using thick posterior polyethylene to manage the   posteriorly directed loads applied when the arm is elevated to the functional position of forward elevation, which is known to create the risk of functional decentering.

This is best explained by noting that when the arm is at the side with a posteriorly augmented glenoid, the net humeral joint reaction force (red arrow) is centered.

However, when the arm is elevated to a functional position, the net humeral joint reaction force (red arrow) is directed posteriorly against the posteriorly augmented polyethylene, subjecting it to the risk of cold flow.

 Furthermore, the point of application of the net humeral joint reaction force of the elevated arm creates an increased glenoid loosening moment (blue line), when the posterior polyethylene is thick.

It is possible that these mechanisms contributed to the development of lucent lines and instability with posteriorly augmented glenoid components in the series presented.


Our approach to the retroverted glenoid is simple - see this link..

(1) We do not rely on preoperative CT scans because they cannot image the shoulder in the functional  position of forward elevation. Instead we prefer the simple standardized axillary view taken with the arm elevated 90 degrees in the plane of the scapula as shown below (this shoulder demonstrates the bad arthritic triad).

(2) We do not use preoperative planning software or patient specific drill guides, but rather ream the glenoid conservatively without trying to 'normalize' glenoid version as shown in this link.

(3) Finally, in a total shoulder arthroplasty for a retroverted glenoid, we place a standard glenoid component on the conservatively reamed glenoid, using an anteriorly eccentric humeral humeral head component if necessary to achieve centering of the articulation. 

This type of reconstruction is shown below on an axillary view taken with the arm in the functional position of forward elevation. Note the centered humeral head and the lack of glenoid lucent lines after two years of implantation.

This approach perseveres the maximal amount of glenoid bone in contrast to what is required to fit the bone to a more complex back side geometry as explained 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.

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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'

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