Eccentric Reaming for B2 Glenoids: History, Preoperative Planning, Surgical Technique, and Outcome
These authors discuss the biconcave (B2) glenoid, characterized by preservation of the anterior portion of the native glenoid with asymmetric wear of the posterior glenoid. They point to the importance of returning the humeral head to a centered position on the glenoid.
These authors discuss the biconcave (B2) glenoid, characterized by preservation of the anterior portion of the native glenoid with asymmetric wear of the posterior glenoid. They point to the importance of returning the humeral head to a centered position on the glenoid.
They suggest that asymmetric remaining can be used to address up to 15 of version correction without compromise of cortical bone.
They advocate for the use of preoperative CT scans
And 3D planning software
However, in reviewing their case example one can make serval observations:
(1) the preoperative CT scan
did not reveal the pathoanatomy as clearly as the preoperative axillary view
(2) in their case example of "corrective reaming", the version of the glenoid was not changed from before surgery
and
(3) the prosthetic humeral head is centered on the humeral head in spite of 30 degrees of postoperative glenoid retroversion (measure it yourself).
We conclude that what matters is centering of the humeral head on the glenoid and preservation of glenoid bone stock. These goals can be achieved in almost all cases without preoperative CT planning and without "corrective reaming" or augmented glenoids.
More on this topic can be see here:
Outcomes of anatomic total shoulder arthroplasty in patients with excessive glenoid retroversion: a case-control study
These authors used a case-controlled study to evaluate the effect of severe preoperative glenoid retroversion on clinical and radiographic total shoulder (TSA) outcomes using a standard non-augmented glenoid component.
They compared 40 patients with more than 20 of glenoid retroversion preoperatively (average follow-up, 53 months) vs. a matched cohort of 80 patients with less than 20 of retroversion (average follow-up, 49 months). In all patients, the surgical technique, implant design, and postoperative rehabilitation protocol were identical. Peg components were predominantly used unless the glenoid vault was determined to be narrow based on preoperative imaging. There were 2 keeled glenoid components used in the retroversion group and 5 keeled glenoid components used in the control group. The glenoid was prepared using noncannulated reaming instrumentation with a goal of preparing the glenoid surface to create a minimum of 80% backside concentric support without violation of subchondral bone support. In cases of eccentric wear, the glenoid was reamed to match the backside of the glenoid component, typically preferentially reaming the anterior glenoid and partially correcting glenoid version. Patients were matched based on sex, age, indication, and prosthetic size.
Preoperatively and postoperatively, both groups demonstrated similar patient reported outcome measures and measured motion.
No significant differences were observed in the postoperative radiographic findings. Postoperative glenoid version was not measured, so the degree of "partial correction" is not known.
The authors concluded that at midterm follow-up, preoperative severe glenoid retroversion does not appear to influence clinical or radiographic outcomes of TSA using a standard glenoid component.
No significant differences were observed in the postoperative radiographic findings. Postoperative glenoid version was not measured, so the degree of "partial correction" is not known.
The authors concluded that at midterm follow-up, preoperative severe glenoid retroversion does not appear to influence clinical or radiographic outcomes of TSA using a standard glenoid component.
Comment: It is of note that a major industry has sprung up around measuring and managing preoperative glenoid retroversion. By contrast, the authors of this paper did not use a guide wire placed based on preoperative measurements and instead adjusted their glenoid reamer to produce a single concavity with minimal bone removal.
This paper can be considered along with the one described below in which postoperative glenoid retroversion was measured and found not to have a negative effect on the outcome.
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
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.
This paper can be considered along with the one described below in which postoperative glenoid retroversion was measured and found not to have a negative effect on the outcome.
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.
Comment: 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 altering this glenoid retroversion that is commonly found in osteoarthritic glenohumeral joints. Methods used include posterior glenoid bone grafts, reaming the anterior aspect of the glenoid, and posteriorly augmented glenoid components. This study 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.
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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