Augmented wedge-shaped glenoid component for the correction of glenoid retroversion: a finite element analysis

doi:10.1016/j.jse.2013.06.008

Journal of Shoulder and Elbow Surgery

Volume 23, Issue 3, March 2014, Pages 347-354

https://doi.org/10.1016/j.jse.2013.06.008 Get rights and content

Background

This study undertook a computational analysis of a wedged glenoid component for correction of retroverted glenoid arthritic deformity to determine whether a wedge-shaped glenoid component design with a built-in correction for version reduces excessive stresses in the implant, cement, and glenoid bone. Recommendations for correcting retroversion deformity are asymmetric reaming of the anterior glenoid, bone grafting of the posterior glenoid, or a glenoid component with posterior augmentation. Eccentric reaming has the disadvantages of removing normal bone, reducing structural support for the glenoid component, and increasing the risk of bone perforation by the fixation pegs. Bone grafting to correct retroverted deformity does not consistently generate successful results.

Methods

Finite element models of 2 scapulae models representing a normal and an arthritic retroverted glenoid were implanted with a standard glenoid component (in retroversion or neutral alignment) or a wedged component. Glenohumeral forces representing in vivo loading were applied and stresses and strains computed in the bone, cement, and glenoid component.

Results

The retroverted glenoid components generated the highest compressive stresses and decreased cyclic fatigue life predictions for trabecular bone. Correction of retroversion by the wedged glenoid component significantly decreased stresses and predicted greater bone fatigue life. The cement volume estimated to survive 10 million cycles was the lowest for the retroverted components and the highest for neutrally implanted glenoid components and for wedged components.

Conclusion

A wedged glenoid implant is a viable option to correct severe arthritic retroversion, reducing the need for eccentric reaming and the risk for implant failure.

Section snippets

Materials and methods

Two whole scapula bone models were selected from CT scan data sets: 1 from a normal, healthy scapula with neutral glenoid alignment (55-year-old man) and 1 from an osteoarthritic scapula with 17° retroversion (62-year-old man). Surface meshes were generated for both cortical and cancellous bone layers using Mimics 3-dimensional image segmentation software (Materialise, Leuven, Belgium). These surface meshes were converted to solid 4-node tetrahedral element meshes with HyperMesh (Altair

Stress on bone model structures

The retroverted glenoid components of both normal and arthritic models generated the highest minimal principal stresses (23 and 24 MPa, respectively), with stress distributed posteriorly toward the edge of the glenoid face. As determined from the bone strength assigned to our models, these stress values were high enough to place the cortical bone of the scapula neck at risk for single cycle failure. Correction of glenoid retroversion by the wedged-glenoid component decreased stress magnitudes

Discussion

Most patients requiring total shoulder arthroplasty have an arthritic glenoid deformity that results in retroversion.8, 12 Implanting the glenoid component without correcting moderate to severe retroversion can have adverse biomechanical effects. The 3 options for correcting retroversion deformity are asymmetric reaming of the anterior glenoid, bone grafting of the posterior glenoid, and implanting a specialized glenoid component with posterior augmentation. Eccentric reaming to correct

Conclusion

Our study indicates that an appropriately wedged glenoid implant is an option to correct severe arthritic retroversion and to reduce the risk for implant or bone failure without the need for eccentric reaming. This study is a biomechanical analysis and therefore requires appropriate clinical studies for validation.

Disclaimer

The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.

References (30)

G. Bergmann et al.
In vivo glenohumeral contact forces–measurements in the first patient 7 months postoperatively
J Biomech
(2007)
P. Buchler et al.
A finite element model of the shoulder: application to the comparison of normal and osteoarthritic joints
Clin Biomech (Bristol, Avon)
(2002)
W.E. Caler et al.
Bone creep-fatigue damage accumulation
J Biomech
(1989)
P. Clavert et al.
Glenoid resurfacing: what are the limits to asymmetric reaming for posterior erosion?
J Shoulder Elbow Surg
(2007)
B. Couteau et al.
In vivo characterization of glenoid with use of computed tomography
J Shoulder Elbow Surg
(2001)
L.H. Frich et al.
Bone strength and material properties of the glenoid
J Shoulder Elbow Surg
(1997)
S.M. Haddock et al.
Similarity in the fatigue behavior of trabecular bone across site and species
J Biomech
(2004)
H.R. Hoenecke et al.
Optimizing glenoid component position using three-dimensional computed tomography reconstruction
J Shoulder Elbow Surg
(2008)
H.R. Hoenecke et al.
Glenoid morphology rather than version predicts humeral subluxation: a different perspective on the glenoid in total shoulder arthroplasty
J Shoulder Elbow Surg
(2012)
S.M. Kurtz et al.
The yielding, plastic flow, and fracture behavior of ultra-high molecular weight polyethylene used in total joint replacements
Biomaterials
(1998)

J.P. Landau et al.

Genetic and biomechanical determinants of glenoid version: implications for glenoid implant placement in shoulder arthroplasty

J Shoulder Elbow Surg

(2009)

P. Mansat et al.

Evaluation of the glenoid implant survival using a biomechanical finite element analysis: influence of the implant design, bone properties, and loading location

J Shoulder Elbow Surg

(2007)

F.A. Matsen et al.

Shoulder arthroplasty: the socket perspective

J Shoulder Elbow Surg

(2007)

B.P. Murphy et al.

On the magnitude and variability of the fatigue strength of acrylic bone cement

Int J Fatigue

(2000)

R.W. Nyffeler et al.

Effects of glenoid component version on humeral head displacement and joint reaction forces: an experimental study

J Shoulder Elbow Surg

(2006)

Cited by (53)

Optimizing glenoid bone preservation in reverse total shoulder arthroplasty using augmented baseplates
2023, JSES Reviews, Reports, and Techniques
As techniques and implants for reverse total shoulder arthroplasty (rTSA) evolve, a greater emphasis is being placed on preserving glenoid bone stock and optimizing shoulder biomechanics. Augmented baseplates preserve glenoid bone and improve shoulder range of motion by lateralizing the center of rotation of the glenosphere, while also reducing postoperative complications after rTSA. The technique for bone preservation with use of augmented baseplates in the absence of bone loss and the outcomes of a series of cases are contained in this report.
A retrospective chart review was conducted for 37 patients with Walch type A1/Sirveaux E0 glenoids who underwent primary rTSA using a bone preserving technique with an augmented baseplate between January 2018 and January 2019 at a single site by a single surgeon. The primary outcome measures were range of motion, strength, and patient-reported clinical outcomes (pain and function rated on a visual analog scale; single assessment numeric evaluation; American Shoulder and Elbow Surgeons score; and disabilities of the arm, shoulder, and hand score). Preoperative radiographs were analyzed for the presence of glenoid bone loss and postoperative radiographs were assessed for evidence of component loosening and scapular notching. A repeated measures design was used, and preoperative and postoperative comparisons were made using parametric t-tests.
At an average follow-up of 23.3 ± 6.3 months, there was a significant improvement in active forward flexion and abduction and nonsignificant improvement in external rotation. There was no radiographic evidence of glenoid notching in any of the patients and optimal glenoid inclination was observed. Patient-reported outcome scores after an average of 25.2 ± 10.0 months indicated a significant improvement in pain, function, and scores for the American Shoulder and Elbow Surgeons and disabilities of the arm, shoulder, and hand assessments. There were no substantial postoperative radiographic findings, intra/postoperative complications, or revisions/reoperations.
rTSA with augmented baseplates for glenoid bone preservation in patients with minimal or no bone loss is effective for preserving glenoid bone stock and significantly improves the range of motion and patient-reported outcomes after approximately 2 years.
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
2022, Journal of Shoulder and Elbow Surgery
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.
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.
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.
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.
Defining deformity thresholds for the use of augmented glenoids in arthritic shoulders with posterior glenoid bone loss
2021, Seminars in Arthroplasty JSES
Despite increasing utilization, little guidance is offered regarding appropriate indications for posterior augmented glenoid implants. The purpose of this study is to virtually assess the effect of implant selection on glenoid resurfacing and joint line restoration in osteoarthritic shoulders with posterior glenoid wear.
Thirty-three CT scans were randomly selected from a cohort of osteoarthritic shoulders with Walch B2 or B3 deformities. Imascap SAS (Wright Medical, Memphis, TN) was used to assess bony deformities and plan glenoid resurfacing. Implants simulated included: standard Pegged Cortiloc, and 15° and 25° half-wedge augments. Each component was planned for a version correction to neutral and 10° retroversion, inclination was maintained within 5° of neutral and the component was medialized until bony support reached 80%. Implantation failure was defined as: greater than 20% cancellous bone support, central peg perforation, or joint line medialization relative to the pathologic joint (accounting for polyethylene thickness). Excessive lateralization was defined as creation of a joint-line >4 mm lateral to the pathologic joint-line.
The mean retroversion deformity in this cohort was 23.7° (range: 13°-37°). When correcting to neutral, the corrective reaming alone failed in 72.7% (24/33) of cases compared to 15.2% (5/33) when correcting to 10° of implant retroversion. When correcting to neutral version failure was decreased with a 15° (27.3%; 9/33; P < .001) and 25° augment (15.2%; 5/33; P < .001). Receiver operating characteristic (ROC) analysis found that an augment is useful to resolve standard implant failure for retroversion deformities greater than 27° (area under the curve [AUC] = 0.91) and 22° (AUC = 0.77) for correcting version to neutral and 10° retroversion, respectively. When placing a 25° augment, there was high risk of overstuffing the joint for both correction to neutral (27.3%) and 10° retroversion (66.7%). Overstuffing was likely to occur when correcting deformities less than 19° (AUC = 0.96) to neutral with a 25° augment. Likewise, implanting 15° or 25° augmented glenoids in 10° of retroversion is likely to overstuff the joint for pathologic retroversion deformities smaller than 18° (AUC = 0.94) and 28° (AUC = 0.69), respectively.
This study helps to clarify the severity of glenoid deformities more appropriately addressed with the use of a half-wedged augmented glenoid. Both the severity of glenoid deformity and the desired implant version affect appropriate indications for the use of augmented glenoids. The risk of excessive joint-line lateralization in shoulders with less severe deformities should not be ignored. These considerations, in addition to individual soft tissue tension should be considered when planning and performing glenoid resurfacing.
Level III; Treatment Study
Joint-line medialization after anatomical total shoulder replacement requires more rotator cuff activity to preserve joint stability
2021, JSES International
The biomechanical effects of joint-line medialization during shoulder surgery are poorly understood. It was therefore the purpose of this study to investigate whether medialization of the joint line especially associated with total shoulder arthroplasty leads to changes in the rotator cuff muscle forces required to stabilize the arm in space.
A validated computational 3-D rigid body simulation model was used to calculate generated muscle forces, instability ratios, muscle-tendon lengths and moment arms during scapular plane elevation. Measurements took place with the anatomical and a 2 mm and 6 mm lateralized or medialized joint line.
When the joint line was medialized, increased deltoid muscle activity was recorded throughout glenohumeral joint elevation. The rotator cuff muscle forces increased with medialization of the joint line in the early phases of elevation. Lateralization of the joint line led to higher rotator cuff muscle forces after 52° of glenohumeral elevation and to higher absolute values in muscle activity. A maximum instability ratio of >0.6 was recorded with 6 mm of joint-line medialization.
In this biomechanical study, medialization and lateralization of the normal joint line during total shoulder arthroplasty led to substantial load changes on the shoulder muscles used for stabilizing the arm in space. Specifically, medialization does not only lead to muscular shortening but also to increased load on the supraspinatus tendon during early arm elevation, the position which is already most loaded in the native joint.
Does acromion anatomy affect the risk of acromion stress fracture after reverse shoulder arthroplasty?
2021, Seminars in Arthroplasty JSES
Reverse shoulder arthroplasty (RSA) alters normal anatomic relationships and results in increased deltoid forces. Which alter physiologic stress patterns in the acromion resulting in fractures. The purpose of this study was to evaluate the effect of acromion anatomy on the stress levels and risk of acromial fracture after RSA.
A lateralization onlay design of the Exactech Equinoxe RSA standard stem was used for all four different acromial sizes (ranging from −5.0 mm to +5.0 mm) and compared to standard normal shoulder model (acromial size 0). A finite element analysis (FEA) model was then constructed for each case and quasi-static analysis was carried out to determine the highest minimum principal stress (HMPS) for each case and this was used to predict fatigue life percentage (FLP) of the acromion.
For smaller acromion sizes of −5 mm and -2.5 mm, the HMPS was found to be 1.87 and 1.24 times higher than the standard, respectively. The HMPS for the +2.5 mm acromial size was 0.95 times compared to the standard and 1.04 times higher for the +5 mm acromial size. According to our model, the highest FLP was seen when the acromion size was +2.5 mm (case 4 - 178%) and the lowest FLP was seen when it was -5 mm (−0.06%).
Our results suggest that there is an optimal acromion size (+2.5 mm from normal male) that leads to the lowest fracture risk in RSA. Surgeons must be aware of acromion size as a critical factor in deltoid tensioning, acromial stress, and risk of acromial fracture when selecting optimal implant designs and sizes for RSA.
Level of evidence: Basic Science Study
Outcomes of anatomic shoulder arthroplasty performed on B2 vs. A1 type glenoids
2020, Journal of Shoulder and Elbow Surgery
Glenoid component malpositioning and glenoid component retroversion have been associated with higher rates of radiolucencies, raising concerns about its implications on glenoid loosening and ultimate failure of anatomic total shoulder arthroplasty (TSA). Although there is literature regarding the relative advantages of techniques to address posterior glenoid bone loss, we are not aware of studies comparing outcomes of TSA on these challenging Walch type B2 glenoids vs. more common A1 glenoids. The purpose of this study is to compare outcomes of TSA performed on A1 glenoids and B2 glenoids treated with asymmetric glenoid reaming.
We identified 1045 shoulders that had primary TSAs performed for osteoarthritis in a prospective shoulder arthroplasty registry. Two hundred eighty-nine shoulders met inclusion criteria of a preoperative Walch type A1 (178) or B2 (111) glenoid morphology, treatment with TSA, asymmetric reaming in the B2 group, and a minimum of 2-year clinical and radiographic follow-up. Postoperative radiographs were assessed for lucencies, and patient-reported outcome measures were collected at all follow-up visits.
Follow-up averaged 40 ± 15 months for all patients, and more men presented with a B2 glenoid (80 of 111; 72%) compared with A1 (101 of 178; 57%) (P = .009). Age at surgery (P = .166), dominant-sided surgery (P = .281), body mass index (P = .501), smoking (P = .155), preoperative opioid use (P = .154), and diabetes (P = .331) were not significantly different between groups. Both groups had similar Constant Strength scores preoperatively (A1: 4.7 ± 7.1, and B2: 4.3 ± 7.3) but the B2 group improved significantly more at final follow-up (A1: 10.3 ± 6.2 vs. B2: 12.7 ± 6.7, P = .005). The Total Constant score was also significantly better at follow-up in the B2 glenoid group (P = .039). All other Constant subscales, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), and Single Assessment Numerical Evaluation (SANE) measures showed significant improvement preoperatively to final follow-up (all P <.001) but there were no significant differences between the A1 and B2 glenoid groups (all P > .05). A similar proportion of patients rated their satisfaction as either very satisfied or satisfied between the A1 (160; 90%) and B2 (100; 90%) (P = .613). Lazarus scores were also similar between the A1 and B2 groups (P = .952) as were the rates of humeral radiolucent lines (P = .749) and humeral osteolysis (P = .507).
Although patients with B2 glenoids may present a more technically challenging anatomic total shoulder arthroplasty, treatment with concurrent asymmetric glenoid reaming produced similar, successful clinical and radiographic early to midterm outcomes for patients undergoing TSA compared with A1 glenoids. Additional follow-up on this cohort will be important to confirm the durability of these early results.

View all citing articles on Scopus

: Investigational Review Board approval was obtained for the use of de-identified clinical CT scans.

View full text

Basic ScienceAugmented wedge-shaped glenoid component for the correction of glenoid retroversion: a finite element analysis

Background

Methods

Results

Conclusion

Section snippets

Materials and methods

Stress on bone model structures

Discussion

Conclusion

Disclaimer

J Biomech

Clin Biomech (Bristol, Avon)

J Biomech

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Biomech

J Shoulder Elbow Surg

J Shoulder Elbow Surg

Biomaterials

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Shoulder Elbow Surg

Int J Fatigue

J Shoulder Elbow Surg

Basic Science
Augmented wedge-shaped glenoid component for the correction of glenoid retroversion: a finite element analysis