Monday, February 13, 2023

Conservative management of the B2 glenoid

Concerns about the management of the biconcave, retroverted "B2" glenoid has given rise to a dramatic increase in the use of preoperative 3D CT-based planning, patient specific instrumentation, augmented anatomic glenoid components, and reverse total shoulder as was observed in a recent post (see link).

The authors of Total Shoulder Arthroplasty in Patients with a B2 Glenoid Addressed with Corrective Reaming: Mean 8-year Follow-up investigated the mid term radiographic and clinical outcomes with a more conservative approach for the B2 glenoid: "high-side reaming" and anatomic total shoulder (aTSA) with a pegged, cemented, non-augmented, all-polyethylene glenoid component.

Of the original cohort of 59 patients (6 now deceased), 34 shoulders in 33 patients with B2 glenoids available for follow-up at a mean of 8.6 years (range 5.5-11.2). 

The preoperative glenoid retroversion averaged 18.9° (range 4° to 32°).  The postoperative glenoid version was not presented, so the extent of "correction" of glenoid version is not known,

Three (5.1%) of the original 59 shoulder were revised. At final follow-up, 3 of 30 (10.0%) shoulders had radiographic glenoid component failure, but were unrevised. Glenoid component failure was associated with worse ASES (88 vs. 73) and VAS pain (0.8 vs. 2.1) scores. At a mean of 8.6 years, 88% of shoulders available for follow-up had well-fixed glenoid components.

Humeral head decentering was measured as the percentage of the humeral head lying posterior to a line bisecting the line segment connecting the anterior and posterior edges of the glenoid as shown below.

Glenoid failure was associated with increased posterior humeral head decentering at final follow-up: intact glenoids had a mean of 7.0% decentering whereas failed glenoids had a mean of 21% decentering. 

Glenoid component failure was also associated with worse initial glenoid component seating, with failed components having an average of 25% of the glenoid component not seated. 

There was no association between glenoid component failure and preoperative retroversion or inclination. The possible association between glenoid component failure and postoperative retroversion was not examined in this study.

Comment: Centering the prosthetic humeral head on the glenoid component and excellent glenoid component seating on the reamed glenoid bone are essential for optimizing the outcome of anatomic total shoulder arthroplasty for B2 pathoanatomy.

Our practice is to accept glenoid retroversion (bottom figure), avoiding removal of the supporting sclerotic bone by attempting to "correct" glenoid version (top figure). 

As the authors point out, poor seating of the glenoid component is a cause of glenoid component failure. This is often due to incomplete reaming of the glenoid to a single concavity that matches the back side of the component. Adequacy of glenoid reaming can be checked by using a pegless trial and making sure there is no tipping with loading of the front, back, top or bottom of the trial.

We also concur with the authors that failure to center the humeral head on the glenoid component increases the risk of failure.  The adequacy of centering is determined at surgery, making sure that there is not excessive posterior translation of the head on the glenoid component. If there is excessive translation, this can be addressed using an anteriorly eccentric humeral head component

and/or by a rotator interval plication.

Two recent papers address the topic managing the retroverted and biconcave glenoid with a non-augmented glenoid component: 

These authors studied a population of patients undergoing anatomic total shoulder arthroplasty (TSA) stratified into two groups: those with the glenoid implanted in ≥ 15 degrees of retroversion and those with the glenoid implanted in <15 degrees of retroversion. The 21 retroverted glenoids had an average of 21±5 degrees of postoperative retroversion in comparison to the 50 non-retroverted glenoids with an average of 6±7 degrees of postoperative version.

The mean improvement in the SST (6.7) for the retroverted group was comparable to that for the nonretroverted group (5.8). The percent of maximal possible improvement (%MPI) for the retroverted glenoids (70%) was comparable to that for the nonretroverted glenoids (67%). The 2-year SST scores for the retroverted (9.3) and the nonretroverted glenoid groups (9.4) were similar.

The radiographic results for the retroverted glenoid group were similar to those for the nonretroverted group with respect to central peg lucency, Lazarus radiolucency score, humeral head centering on the glenoid. No patient in either group had problems with instability. None of the glenoid components placed in retroversion had revision, while 6% of the non-retroverted glenoid were revised.
The results for type B glenoids were comparable for the retroverted and non retroverted components.

(2) Anatomic Total Shoulder Arthroplasty with All-Polyethylene Glenoid Component for Primary Osteoarthritis with Glenoid Deficiencies

The authors identified 66 shoulders with type-B2 glenoids (n = 40) or type-B3 glenoids (n = 26) undergoing total shoulder arthroplasties with a non-augmented glenoid component inserted without attempting to normalize glenoid version and with clinical and radiographic follow-up of a minimum of 2 years. The Simple Shoulder Test (SST), the percentage of humeral-head decentering on the glenoid face, and bone ingrowth into the central peg were the main outcome variables of interest. Similar analyses were made for concurrent patients with type-A1, A2, B1, and D glenoid pathoanatomy to determine if the outcomes for type-B2 and B3 glenoids were inferior to those for the other types.

Glenoid version and humeral head centering was determined on standardized axillary views obtained before surgery and at followup.

The SST score (and standard deviation) improved 
from 3.2 ± 2.1 points preoperatively to 9.9 ± 2.4 points postoperatively (p < 0.001) at a mean time of 2.8 ± 1.2 years for type-B2 glenoids and 
from 3.0 ± 2.5 points preoperatively to 9.4 ± 2.1 points postoperatively (p < 0.001) at a mean time of 2.9 ± 1.5 years for type-B3 glenoids; 
these results were not inferior to those for shoulders with other glenoid types.

Postoperative glenoid version was not significantly different from preoperative glenoid version.

The mean humeral-head posterior decentering on the glenoid face was reduced for type-B2 glenoids from 14% ± 7% preoperatively to 1% ± 2% postoperatively and for type-B3 glenoids from 4% ± 6% preoperatively to 1% ± 3% postoperatively .

The rates of bone integration into the central peg for type-B2 glenoids (83%) and type-B3 glenoids (81%) were not inferior to those for other glenoid types.

While anterior penetration of the central peg did occur, it did not interfere with osseous integration or the clinical outcome.

The authors concluded that total shoulder arthroplasty with a standard glenoid component inserted without changing version can significantly improve patient comfort and function and consistently center the humeral head on the glenoid face in shoulders with type-B2 and B3 glenoids, achieving >80% osseous integration into the central peg. These clinical and radiographic outcomes for type- B2 and B3 glenoids were not inferior to those outcomes for other glenoid types.

Here are a few examples. Note the glenoid bone preservation, the glenoid component seating, and the bone ingrowth into the central peg. 

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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).