Sunday, July 23, 2017

Addressing glenoid retroversion in total shoulder arthroplasty

Posterior glenoid bone grafting in total shoulder arthroplasty for osteoarthritis with severe posterior glenoid wear

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.

These authors report the minimum two year results of TSA with posterior glenoid bone grafting (PGBG) with humeral head autograft in 28 patients with shoulder osteoarthritis and posterior glenoid wear. Note in the figure below, both the plain film and the CT scan show glenoid retroversion, but only the axillary view taken with the arm away from the side (the 'truth view') shows posterior decentering of the humeral head on the face of the glenoid in contrast to the humeral head centering seen on the CT scan obtained with the arm at the side.

Plain x-rays showed that glenoid retroversion had changed from  −28° ± 4° preoperatively to −4° ±  2°.

After surgery, the humeral head subluxation improved with respect to the scapular axis and to the midglenoid face. 
All PGBGs incorporated. 
Three patients (10.7%) had a total of 5 broken or displaced screws. 
Three patients (10.7%) had a broken metal marker in the center peg of the glenoid component. 

No patients required component revision surgery by final follow-up. Only 1 reoperation occurred for capsular release. Patients showed significant improvements in all patient reported outcomes. The average SST score improved from 4±3 to 10±2

Comment: These results in 28 patients with an average of 28±4 degrees of preoperative retroversion treated with posterior glenoid bone grafting (postoperative glenoid version 4±2 degrees) can be compared to those recently reported for 21 patients with an average of 21.1° ± 9.9° degrees of preoperative retroversion treated with a standard glenoid component inserted without attempting to alter glenoid version (postoperative glenoid version 20.7± 5.3):
Does Postoperative Glenoid Retroversion Affect the 2-Year Clinical and Radiographic Outcomes for Total Shoulder Arthroplasty? That study analyzed the two year outcomes in 71 TSAs, comparing the 21 in a "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 results in the retroverted group were not inferior to those for the non-retroverted group. 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).

In conclusion, glenoid retroversion is a relatively common finding in arthritic glenohumeral joints coming to shoulder arthroplasty. Shoulders with preoperative glenoid retroversion tend to have poorer preoperative shoulder comfort and function, posterior decentering, and glenoid biconcavity, all indicating a more severe form of the disease. There is currently great interest in methods for managing this glenoid retroversion commonly found in osteoarthritic glenohumeral joints using posterior glenoid bone grafts, reaming the anterior aspect of the glenoid, and posteriorly augmented glenoid components. The first study reviewed above reports the result of shoulders managed by altering the glenoid version with a posterior humeral head autograft. The second study reviewed above reports the two year results of a more conservative approach in which minimal glenoid bone is removed by reaming and specific attempts to alter glenoid version are not used.

Here is the two year radiographic followup on a 55 year old patient from our practice. Preoperative films show a type B2 genoid with retroversion, biconcavity and posterior humeral subluxation.

Here are the 2 year films of this shoulder after conservative shoulder arthroplasty using a standard glenoid component without attempts to modify glenoid version. The humeral head is centered in the prosthetic glenoid. At two years after surgery the patient was able to perform all 12 functions of the Simple Shoulder Test.

Note that sufficient bone stock remains to perform a revision total or a reverse total shoulder arthroplasty shoulder these procedures become necessary in the future of this young person.

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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