Relationship Between Glenoid Component Shift and Osteolysis After Anatomic Total Shoulder Arthroplasty: Three-Dimensional Computed Tomography Analysis

Effect of vitamin E-enhanced highly cross-linked polyethylene on wear rate and particle debris in anatomic total shoulder arthroplasty: a biomechanical comparison to ultrahigh-molecular-weight polyethylene

BACKGROUND

Particle-induced osteolysis resulting from polyethylene wear remains a source of implant failure in anatomic total shoulder designs. Modern polyethylene components are irradiated in an oxygen-free environment to induce cross-linking, but reducing the resulting free radicals with melting or heat annealing can compromise the component's mechanical properties. Vitamin E has been introduced as an adjuvant to thermal treatments. Anatomic shoulder arthroplasty models with a ceramic head component have demonstrated that vitamin E-enhanced polyethylene show improved wear compared with highly cross-linked polyethylene (HXLPE). This study aimed to assess the biomechanical wear properties and particle size characteristics of a novel vitamin E-enhanced highly cross-linked polyethylene (VEXPE) glenoid compared to a conventional ultrahigh-molecular-weight polyethylene (UHMWPE) glenoid against a cobalt chromium molybdenum (CoCrMo) head component.

METHODS

Biomechanical wear testing was performed to compare the VEXPE glenoid to UHMWPE glenoid with regard to pristine polyethylene wear and abrasive endurance against a polished CoCrMo alloy humeral head in an anatomic shoulder wear-simulation model. Cumulative mass loss (milligrams) was recorded, and wear rate calculated (milligrams per megacycle [Mc]). Under pristine wear conditions, particle analysis was performed, and functional biologic activity (FBA) was calculated to estimate particle debris osteolytic potential. In addition, 95% confidence intervals for all testing conditions were calculated.

RESULTS

The average pristine wear rate was statistically significantly lower for the VEXPE glenoid compared with the HXLPE glenoid (0.81 ± 0.64 mg/Mc vs. 7.00 ± 0.45 mg/Mc) (P < .05). Under abrasive wear conditions, the VEXPE glenoid had a statistically significant lower average wear rate compared with the UHMWPE glenoid comparator device (18.93 ± 5.80 mg/Mc vs. 40.47 ± 2.63 mg/Mc) (P < .05). The VEXPE glenoid demonstrated a statistically significant improvement in FBA compared with the HXLPE glenoid (0.21 ± 0.21 vs. 1.54 ± 0.49 (P < .05).

CONCLUSIONS

A new anatomic glenoid component with VEXPE demonstrated significantly improved pristine and abrasive wear properties with lower osteolytic particle debris potential compared with a conventional UHMWPE glenoid component. Vitamin E-enhanced polyethylene shows early promise in shoulder arthroplasty components. Long-term clinical and radiographic investigation needs to be performed to verify if these biomechanical wear properties translate to diminished long-term wear, osteolysis, and loosening.

Does glenoid version and its correction affect outcomes in anatomic shoulder arthroplasty? A systematic review

BACKGROUND

Correction of glenoid retroversion is commonly performed in anatomic total shoulder arthroplasty (TSA) to increase component contact area and decrease eccentric loading of the glenoid component. Despite demonstrated biomechanical advantages, limited information exists on the clinical benefit of correcting glenoid retroversion. The purpose of this systematic review is to critically evaluate the existing literature on the effect of preoperative and postoperative glenoid retroversion on clinical functional and radiologic outcomes in patients who underwent anatomic TSA.

METHODS

A systematic literature review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses using PubMed, Embase, and Cochrane Library evaluating the impact of glenoid retroversion on clinical and radiologic outcomes of TSA. English-language studies of level I through IV evidence were included. Blinded reviewers conducted multiple screens and methodological quality was appraised using the Modified Coleman Methodology Score.

RESULTS

Sixteen studies, including 3 level III and 13 level IV studies (1211 shoulders), satisfied all inclusion criteria. To address glenoid retroversion, 9 studies used corrective reaming techniques, and 4 studies used posteriorly augmented glenoids. Two studies used noncorrective reaming techniques. Mean preoperative retroversion ranged from 12.7° to 24° across studies. Eleven studies analyzed the effect of glenoid retroversion on clinical outcomes, including patient-reported outcome scores (PROs), range of motion (ROM), or clinical failure or revision rates. Most studies (8 of 11) did not report any significant association of pre- or postoperative glenoid retroversion on any clinical outcome. Of the 3 studies that reported significant effects, 1 study reported a negative association between preoperative glenoid retroversion and PROs, 1 study reported inferior postoperative abduction in patients with postoperative glenoid retroversion greater than 15°, and 1 study found an increased clinical failure rate in patients with higher postoperative retroversion. Ten studies reported radiographic results (medial calcar resorption, Central Peg Lucency [CPL] grade, Lazarus lucency grade) at follow-up. Only 1 study reported a significant effect of pre- and postoperative retroversion greater than 15° on CPL grade.

CONCLUSION

There is currently insufficient evidence that pre- or postoperative glenoid version influences postoperative outcomes independent of other morphologic factors such as joint line medialization. Given that noncorrective reaming demonstrated favorable postoperative outcomes, and postoperative glenoid version was not significantly and consistently found to impact outcomes, there is inconclusive evidence that correcting glenoid retroversion is routinely required.

Comparing outcomes of central ingrowth peg vs. noningrowth pegged glenoid components during revision to reverse total shoulder arthroplasty

Background

One innovation to reduce glenoid loosening in total shoulder arthroplasty (TSA) is a large, central ingrowth peg. However, when bone ingrowth fails to occur, there is often increased bone loss surrounding the central peg which may increase complexity of subsequent revisions. Our goal was to compare outcomes between central ingrowth pegs and noningrowth pegged glenoid components during revision to reverse total shoulder arthroplasty.

Methods

In a comparative retrospective case series, all patients who underwent TSA-to-reverse TSA revision between 2014 and 2022 were reviewed. Demographic varibles as well as clinical and radiographic outcomes were collected. Ingrowth central peg and noningrowth pegged glenoid groups were compared using t-test, Mann-Whitney U, Chi-Square, or Fisher's exact tests where indicated.

Results

Overall, 49 patients were included: 27 underwent revision from noningrowth and 22 from central ingrowth components. Females more commonly had noningrowth components (74% vs. 45%, P = .04) and preoperative external rotation was higher in central ingrowth components (P = .02). Time to revision was significantly earlier in central ingrowth components (2.4 vs. 7.5 years, P = .01). Structural glenoid allografting was required more with noningrowth components (30% vs. 5%, P = .03) and time to revision in patients ultimately requiring allograft reconstruction was significantly later (9.96 vs. 3.68 years, P = .03).

Conclusion

Central ingrowth pegs on glenoid components were associated with decreased need for structural allograft reconstruction during revision; however, time to revision was earlier in these components. Further research should focus on whether glenoid failure is due to glenoid component design, time to revision, or both.

Short-term clinical and radiographic outcomes of a hybrid all-polyethylene glenoid based on preoperative glenoid morphology

BACKGROUND

The primary purpose of this study was to compare 2-year anatomic total shoulder arthroplasty (TSA) functional and radiographic outcomes between Walch type A and B glenoids treated with an all-polyethylene glenoid designed for hybrid fixation with peripheral cement and central osseous integration. The secondary purpose was to evaluate outcomes based on central peg technique. The hypotheses were that there would be no difference in short-term radiographic or functional outcome scores based on preoperative glenoid morphology or central peg technique.

METHODS

We performed a multicenter retrospective review of patients who underwent TSA with the same hybrid all-polyethylene glenoid and had minimum 2-year follow-up. Patient-reported outcomes and radiographic outcomes were analyzed based on preoperative Walch morphology and central peg technique. Radiographic analysis included preoperative glenoid morphology; preoperative and postoperative glenoid version, glenoid inclination, and posterior humeral head subluxation; and postoperative glenoid radiolucencies according to the Wirth and Lazarus classifications.

RESULTS

A total of 266 patients with a mean age of 64.9 ± 8.2 years were evaluated at a mean of 28 months postoperatively. Postoperatively, there were significant improvements in all functional outcome measures (P < .001), range-of-motion measures (forward elevation, external rotation at 0°, external rotation at 90°, internal rotation by spinal level, and internal rotation at 90°; P < .001), and strength measures (Constant, external rotation, and modified belly press; P < .001). There were no clinically meaningful differences in functional outcomes or statistically significant differences in radiographic appearance between Walch type A and B glenoids. Subgroup analysis revealed that glenoids with a cemented central peg had the worst radiographic outcomes based on Lazarus scoring.

CONCLUSION

Patients undergoing TSA with a hybrid in-line pegged glenoid have excellent clinical outcomes at short-term follow-up regardless of preoperative glenoid morphology. Different central peg techniques do not appear to play a significant role in the risk of glenoid component lucencies at 2 years postoperatively.

Anatomic total shoulder glenoid component inclination affects glenohumeral kinetics during abduction: a cadaveric study

BACKGROUND

Although typically favorable in outcome, anatomic total shoulder arthroplasty (aTSA) can require long-term revision. The most common cause for revision is glenoid loosening, which may result from eccentric cyclic forces and joint translations. "Rocking" of the glenoid component may be exacerbated by the joint geometry, such as glenoid inclination and version. Restoration of premorbid glenoid inclination may be preferable, although laboratory and computational models indicate that both superior inclination and inferior inclination have benefits. This discrepancy may arise because previous studies were limited by a lack of physiological conditions to test inclination. Therefore, a cadaveric shoulder simulator with 3-dimensional human motion was used to study joint contact and muscle forces with isolated changes in glenoid inclination.

METHODS

Eight human cadaveric shoulders were tested before and after aTSA. Scapular-plane abduction kinematics from human subjects were used to drive a cadaveric shoulder simulator with 3-dimensional scapulothoracic and glenohumeral motion. Glenoid inclination was varied from -10° to +20°, whereas compressive, superior-inferior shear, and anterior-posterior shear forces were collected with a 6-df load cell during motion. Outputs also included muscle forces of the deltoid and rotator cuff. Data were evaluated with statistical parametric mapping repeated-measures analysis of variance and t tests.

RESULTS

Inferior glenoid inclination (-10°) reduced both compressive and superior-inferior shear forces vs. neutral 0° inclination by up to 40%, and even more when compared with superior inclination (P < .001). Superior inclinations (+10° and +20°) tended to increase deltoid and rotator cuff forces vs. neutral 0° inclination or inferior inclination, on the order of 20%-40% (P ≤ .045). All force metrics except anterior-posterior shear were lowest for inferior inclination. Most aTSA muscle forces for neutral 0° inclination were not significantly different from native shoulders and decreased 45% and 15% in the posterior deltoid and supraspinatus, respectively (P ≤ .003). Joint translations were similar to prior reports in aTSA patients and did not differ between any inclinations or compared with native shoulders. Joint reaction forces were similar to those observed in human subjects with instrumented aTSA implants, providing confidence in the relative magnitude of our results.

CONCLUSIONS

Inferior inclination reduces overall forces in the shoulder. Superior inclinations increase the muscle effort required for the shoulder to achieve similar motion, thus increasing the forces exerted on the glenoid component. These results suggest that a preference toward aTSA glenoid components in inferior inclination may reduce the likelihood of glenoid loosening by reducing excessive muscle and joint contact forces.

Early clinical and radiographic outcomes of anatomic total shoulder arthroplasty with a biconvex posterior augmented glenoid for patients with posterior glenoid erosion: minimum 2-year follow-up

BACKGROUND

Glenoid bone loss in anatomic total shoulder arthroplasty (aTSA) remains a controversial and challenging clinical problem. Previous studies have shown high rates of glenoid loosening for aTSA in shoulders with retroversion, posterior bone loss, and posterior humeral head subluxation. This study is the first to present minimum 2-year follow-up data of an all-polyethylene, biconvex augmented anatomic glenoid component for correction of glenoid retroversion and posterior humeral head subluxation.

METHODS

This study is a multicenter, retrospective review of prospectively collected data on consecutive patients from 7 global clinical sites. All patients underwent aTSA using the biconvex posterior augmented glenoid (PAG). Inclusion criteria were preoperative computed tomographic (CT) scan, minimum 2 years since surgery, preoperative and minimum 2-year postoperative range of motion examination, and patient-reported outcome measures (PROMs). Glenoid classification, glenoid retroversion, and posterior humeral head subluxation were measured from preoperative CT and radiography and postoperative radiography. Statistical comparisons between pre- and postoperative values were performed with a paired t test.

RESULTS

Eighty-six of 110 consecutive patients during the study period (78% follow-up) met the inclusion criteria and were included in our analysis. Mean follow-up was 35 ± 10 months, with a mean age of 68 ± 8 years (range 48-85). Range of motion statistically improved in all planes from pre- to postoperation. Mean visual analog scale score improved from 5.2 preoperation to 0.7 postoperation, Single Assessment Numeric Evaluation score from 43.2 to 89.5, Constant score from 41.8 to 76.9, and American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form score from 49.8 to 86.7 (all P < .0001). Mean glenoid retroversion improved from 19.3° to 7.4° (P < .0001). Posterior subluxation improved from 69.1% to 53.5% and posterior decentering improved from 5.8% to -3.0% (P < .0001). There was 1 patient with both a prosthetic joint infection and radiographic glenoid loosening that required revision. Seventy-nine of 86 patients had a Lazarus score of 0 (no radiolucency seen about peg or keel) at final follow-up.

CONCLUSIONS

This study shows that at minimum 2-year follow-up, a posterior-augmented all-polyethylene glenoid can correct glenoid retroversion and posterior humeral head subluxation. Clinically, there was significant improvement in both range of motion and PROMs.

The Definition of Periprosthetic Osteolysis in Shoulder Arthroplasty: A Systematic Review of Grading Schemes and Criteria

BACKGROUND

Periprosthetic osteolysis is a known complication after shoulder arthroplasty that may lead to implant loosening and revision surgery. To date, there is no consensus in the shoulder arthroplasty literature regarding the definition of osteolysis or the grading criteria, thus making it difficult to quantify and compare outcomes involving this complication. The purpose of this study was to perform a systematic review of the literature to assess how periprosthetic osteolysis in shoulder arthroplasty is defined and evaluated radiographically.

METHODS

A systematic review of MEDLINE, Scopus, Cochrane, and CINAHL was performed in August 2021 for studies that provided a definition and/or grading criteria for osteolysis in shoulder arthroplasty. Only studies with a minimum of 2 years of radiographic follow-up were included.

RESULTS

Thirty-four articles met the inclusion criteria. After consolidating studies by the same primary author that included the same grading criteria, 29 studies were examined for their definition and grading criteria for osteolysis. Of these, 19 (65.5%) evaluated osteolysis surrounding the glenoid and 18 (62.1%) evaluated osteolysis surrounding the humerus. There was considerable heterogeneity in the systems used to grade periprosthetic osteolysis surrounding the glenoid, whereas humeral periprosthetic osteolysis was often categorized via visualization into binary or categorical groups (e.g., presence versus absence; mild, moderate, or severe; partial versus complete). Four studies (13.8%) provided novel measurements for assessing either glenoid or humeral osteolysis.

CONCLUSIONS

Considerable heterogeneity exists in the assessment and grading of periprosthetic osteolysis in shoulder arthroplasty. The most common grading systems were binary and used qualitative visual interpretation, making them relatively subjective and prone to bias. Quantitative measurements of osteolysis were infrequently utilized. A standardized method of assessing osteolysis would be of value to facilitate communication and research efforts.

Stepped Augmented Glenoid Component in Anatomic Total Shoulder Arthroplasty for B2 and B3 Glenoid Pathology: A Study of Early Outcomes

BACKGROUND

Posterior glenoid bone loss is commonly associated with primary glenohumeral osteoarthritis. Surgical management of bone loss in anatomic total shoulder arthroplasty (aTSA) remains controversial. We studied the use of a stepped augmented glenoid component for management of Walch B2 and B3 glenoids and compared the radiographic and clinical outcomes at short-term follow-up with those achieved with a non-augmented component of the same design in Walch A1 glenoids.

METHODS

Ninety-two patients (42 A1, 29 B2, and 21 B3 glenoids) were prospectively followed after aTSA. Sequential 3-dimensional (3D) computed tomography (CT) imaging was performed preoperatively, within 3 months postoperatively with metal artifact reduction (MAR) to define implant position, and at a minimum of 2 years postoperatively with MAR. Scapular 3D registration with implant registration allowed 3D measurement of glenoid implant position, implant shift, and central peg osteolysis (CPO).

RESULTS

CPO with or without implant shift occurred in a higher percentage of B3 glenoids treated with the augmented glenoid component (29%) than A1 glenoids treated with a standard component (5%) (p = 0.028). There was no significant difference in the frequency of CPO between B2 glenoids with the augmented component (10%) and A1 glenoids with the standard component. There was no difference in postoperative glenoid component version and inclination between groups. B3 glenoids were associated with more component medialization relative to the premorbid joint line compared with A1 and B2 glenoids (p < 0.001).

CONCLUSIONS

A stepped augmented glenoid component can restore premorbid glenoid anatomy in patients with asymmetric biconcave glenoid bone loss (Walch B2), with short-term clinical and radiographic results equivalent to those for patients without glenoid bone loss (Walch A1) treated with a non-augmented component. There is a greater risk of CPO in patients with moderate-to-severe B3 glenoid pathology with this stepped augmented glenoid component. Longer follow-up will help define the clinical implications of CPO over time.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Subluxation in the Arthritic Shoulder

»

The term "subluxation" means partial separation of the joint surfaces. In the arthritic shoulder, "arthritic glenohumeral subluxation" refers to displacement of the humeral head on the surface of the glenoid.

»

The degree of arthritic glenohumeral subluxation can be measured using radiography with standardized axillary views or computed tomography (CT).

»

Shoulders with a type-B1 or B2 glenoid may show more posterior subluxation on an axillary radiograph that is made with the arm in an elevated position than on a CT scan that is made with the arm at the side.

»

The degree of arthritic glenohumeral subluxation is not closely related to glenoid retroversion.

»

The position of the humeral head with respect to the plane of the scapula is related to glenoid retroversion and is not a measure of glenohumeral subluxation.

»

Studies measuring glenohumeral subluxation before and after arthroplasty should clarify its importance to the clinical outcomes of shoulder reconstruction.