Implant impingement during internal rotation after reverse shoulder arthroplasty. The effect of implant configuration and scapula anatomy: A biomechanical study

doi:10.1016/j.clinbiomech.2016.02.015

Clinical Biomechanics

Volume 33, March 2016, Pages 111-116

https://doi.org/10.1016/j.clinbiomech.2016.02.015 Get rights and content

Highlights

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No influence of scapular anatomy on maximum internal rotation
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Internal rotation can be improved biomechanically by the use of eccentric glenospheres.
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Internal rotation can be improved biomechanically by the use of shallow humeral cups.
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Improved internal rotation may reduce restrictions in daily living activities.

Abstract

Background

Internal rotation after reverse shoulder arthroplasty is essential to perform fundamental daily living activities. The purpose of this study was to examine the impact of anatomical and implant related factors on impingement-free internal rotation of the glenohumeral joint.

Methods

CT-scans of 13 human shoulder specimens with implanted reverse shoulder prostheses were carried out and scapula neck length, lateral pillar angle, and implantation height of the metaglene were measured. Internal rotation testing of all specimens was performed by the use of a robot assisted shoulder simulator. Biomechanical variables were analyzed using a three-way ANOVA. Spearman's rank correlations were performed to determine the relationship between biomechanical and anatomical data.

Findings

The maximum internal rotation angle for a 38 mm centric glenosphere and a standard onlay was 93.4(SD 34.9°). The change of the diameter of the glenosphere resulted in no significant increase of the maximum rotation angle (P = 0.16), while change of the glenosphere type from concentric to eccentric (P = 0.005) as well as the change of the onlay type from standard to a more shallow one (P = 0.002) both had a significant effect on the internal rotation.

The distance between the inferior rim of the metaglene and the inferior aspect of the glenoid (P = 0.21), scapula pillar angle (P = 0.13) as well as the scapula neck length (P = 0.81) showed no significant correlation with the maximum internal rotation angle.

Interpretation

Implant component selection shows strong influence on the impingement-free internal rotation. The use of an eccentric glenosphere and a shallow humeral cup may improve internal rotation after reverse shoulder arthroplasty.

Introduction

Reverse shoulder arthroplasty is a well accepted treatment for patients with a symptomatic cuff tear arthropathy, failed total shoulder arthroplasty and sequelae of trauma (Frankle et al., 2005, Guery et al., 2006, Levy et al., 2007a, Levy et al., 2007b, Sirveaux et al., 2004, Wall et al., 2007, Werner et al., 2005). Nonetheless some challenges remain, scapular notching which was originally described by Sirveaux et al. (2004) is the most frequently reported complication in reverse shoulder arthroplasty caused by the reversed implant design concept. Notching is reported with a high prevalence ranging from 44 to 96% (Boileau et al., 2005, Simovitch et al., 2007; Werner et al., 2005). Scapular notching is a consequence of repeated impingement between the humeral implant component and the scapular neck during adduction of the arm which in time results in bony erosion and polyethylene wear of the onlay (Boileau et al., 2005, Simovitch et al., 2007). Impingement can further restrict the range of motion of the arm and notching may lead to early implant loosening caused by bone loss and wear particle induced weakening of the bone-implant interface (Nyffeler et al., 2004, Vanhove and Beugnies, 2004). Because of the proposed mechanical explanation for scapular notching, research groups have investigated surgical, anatomical and implant associated influence factors, with the aim to reduce scapular impingement and notching. Simovitch et al. investigated 77 consecutive shoulders of patients that had developed scapular notching and found a high correlation of inferior notching with the angle between the glenosphere and the scapular neck as well as with the position of the glenosphere on the proximal humerus (Simovitch et al., 2007). In subsequent studies, the influence of glenosphere positioning has been confirmed and several authors have recommended an increased inferior overlap (Gutiérrez et al., 2008; Lévigne et al., 2008, Middernacht et al., 2008). In a biomechanical study on scapular bone models, Chou et al. investigated the range of motion of reverse shoulder prostheses with different glenosphere configurations and found eccentric and larger diameter glenospheres to improve the amount of maximum adduction (Chou et al., 2009). Furthermore a, reduced humeral neck-shaft angle and cup depth tends to result in improved adduction deficit in reverse shoulder arthroplasty (Boileau et al., 2005, Gutiérrez et al., 2008).

In most of the clinical and biomechanical studies addressing the notching phenomenon, the factors that influence scapular notching are associated with the impingement of the humeral implant with the scapular bone during arm adduction. Nonetheless, clinically patients often show limited abilities in performing internal rotation tasks after reverse shoulder arthroplasty (Levy et al., 2014, Sirveaux and Mole, 2010, Stevens et al., 2014, Triplet et al., 2014) which may lead to reduced mobility in daily living activities and may limit the ability to perform perineal care, which requires a maximum of internal rotation (Raiss et al., 2007; Sirveaux and Mole, 2010). Possible reasons for this limited function in internal rotation might be soft tissue related, but also could be a result of the reverse biomechanical joint function caused by the implant design, or by impingement of the humeral prosthesis with the scapular bone although these have not been investigated or verified. The purpose of this biomechanical study was therefore to investigate the influence of the glenosphere position and implant design features on the mechanical conflict between the humeral component and the scapula during internal rotation of the arm. Furthermore, in the same context, the effect of the individual scapular anatomy on the internal rotation was evaluated. The hypothesis we posed was that the size and position of the glenosphere, humeral cup depth, and the anatomy of the scapula all have a combined influence on the inferior scapular impingement of reverse shoulder arthroplasty during internal rotation.

Section snippets

Specimen preparation and mounting

Thirteen human cadaveric shoulder specimens with no radiographic evidence of glenohumeral osteoarthritis or cuff tear arthropathy were obtained for the study (median age 75 years, range 52 to 85). Prior to preparation and biomechanical testing all specimens were evaluated by CT scans defining different parameters of scapula anatomy. The specimens were subsequently thawed at room temperature for 12 h. For fixation of the shoulders in the testing apparatus, the soft tissue of the medial scapula

Results

The maximum internal rotation angle (IRA) when using a 38 mm centric glenosphere and a standard onlay was found to be 93.4 (SD 34.9°). The IRA was increased by 10.8 (SD 11.9°) with changing the diameter of the glenosphere from 38 mm to 42 mm (Fig. 3). Comparing the 38 mm concentric glenosphere with the 38 mm eccentric glenosphere increased the IRA by 21.9 (SD 10.7°) (Fig. 3). An increase of the IRA by 17.1 (SD 14.5°) was observed when changing the glenosphere with a diameter of 42 mm from concentric

Discussion

The development of shoulder implants with a reverse, non-anatomical joint design allows a sufficient management of shoulders with cuff-deficiencies. Although several studies have basically shown an improvement in the range of motion after reverse shoulder arthroplasty (Frankle et al., 2005, Guery et al., 2006, Levy et al., 2007a, Sirveaux et al., 2004, Wall et al., 2007, Werner et al., 2005), the impingement of the prosthetic socket with the neck of the scapula during certain motions still

Conclusions

This study provides further insight into the effects of the implant component selection of the reverse shoulder arthroplasty. The influence of scapular anatomy on internal rotation could not be shown in this study. Internal rotation of the Grammont style reverse shoulder arthroplasty can be improved biomechanically by the use of eccentric glenospheres and a shallow humeral cup design. Improved internal rotation may reduce restrictions in daily living activities such as perineal care, may minor

Conflict of interest statement

Manuel Krämer, Alexandra Bäunker, Mathias Wellmann, and Christof Hurschler have no conflict of interest to disclose.

Tomas Smith is a consultant for shoulder surgery for DePuy Synthes.

Acknowledgments

The financial and material support of DePuy Synthes (2012-0006), Warsaw, USA is gratefully acknowledged.

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Cited by (25)

Discordance between patient-reported and objectively measured internal rotation after reverse shoulder arthroplasty
2023, Journal of Shoulder and Elbow Surgery
Patient satisfaction after reverse shoulder arthroplasty (RSA) partly relies on restoring functional internal rotation (IR). Although postoperative assessment of IR includes objective appraisal by the surgeon and subjective report from the patient, these evaluations may not vary together uniformly. We assessed the relationship between objective, surgeon-reported assessments of IR and subjective, patient-reported ability to perform IR-related activities of daily living (IRADLs).
Our institutional shoulder arthroplasty database was queried for patients undergoing primary RSA with a medialized-glenoid lateralized-humerus design between 2007-2019 and minimum 2-year follow-up. Patients who were wheelchair bound or had a preoperative diagnosis of infection, fracture, and tumor were excluded. Objective IR was measured to the highest vertebral level reached with the thumb. Subjective IR was reported based on patients’ rating (normal, slightly difficult, very difficult, or unable) of their ability to perform 4 IRADLs (tuck in shirt with hand behind back, wash back or fasten bra, personal hygiene, and remove object from back pocket). Objective IR was assessed preoperatively and at latest follow-up and reported as median and interquartile ranges.
A total of 443 patients were included (52% female) at a mean follow-up of 4.4 ± 2.3 years. Objective IR improved pre- to postoperatively from L4-L5 (buttocks to L1-L3) to L1-L3 (L4-L5 to T8-T12) (P < .001). Preoperatively reported IRADLs of “very difficult” or “unable” significantly decreased postoperatively for all IRADLs (P ≤ .004) except those unable to perform personal hygiene (3.2% vs. 1.8%, P > .99). The proportions of patients who improved, maintained, and lost objective and subjective IR was similar between IRADLs; 14%-20% improved objective IR but lost or maintained subjective IR and 19%-21% lost or maintained the same objective IR but improved subjective IR depending on the specific IRADL assessed. When ability to perform IRADLs improved postoperatively, objective IR also increased (P < .001). In contrast, when subjective IRADLs worsened postoperatively, objective IR did not significantly worsen for 2 of 4 IRADLs assessed. When examining patients who reported no change in ability to perform IRADLs pre- vs. postoperatively, statistically significant increases in objective IR were found for 3 of 4 IRADLs assessed.
Objective improvement in IR parallels improvements in subjective functional gains uniformly. However, in patients with worse or equivalent IR, the ability to perform IRADLs postoperatively does not uniformly correlate with objective IR. When attempting to elucidate how surgeons can ensure patients will have sufficient IR after RSA, future investigations may need to use patient-reported ability to perform IRADLs as the primary outcome measure rather than objective measures of IR.
The impact of coracoid morphometry on internal rotation outcome in patients with cuff tear arthropathy treated with reverse shoulder arthroplasty
2023, Seminars in Arthroplasty JSES
Functional internal rotation (fIR) motion remains a concern after reverse shoulder arthroplasty (RSA). The extreme variability of the coracoid morphometry together with the gain in tension of the conjoint tendon could impact internal rotation (IR) after RSA. Our aim was to evaluate the relationship between postoperative IR outcome and coracoid morphometry, evaluated as anteroposterior (AP) and mediolateral (ML) glenocoracoid distances in a 3-dimensional preoperative computed tomography scans, in a consecutive series of patients undergoing the same RSA implant.
A retrospective analysis of a prospectively collected series of 40 patients (18 male, 22 female; mean age (standard deviation [SD]), 73.4 years [4.1]) submitted to RSA for cuff tear arthropathy was performed. fIR function was measured as the highest midline segment of the back that can be reached and converted into 5 range segments of motion. Participants were divided into 2 groups according to the fIR (group A, ≤6; group B, >6). Passive IR was also measured. The AP and ML glenocoracoid distances were measured, in millimeters, on the preoperative 3-dimensional computed tomography scans. Statistics were performed.
The mean follow-up was 29 months (range, 24-39). The mean score for fIR was 6.45 (SD: 1.81) while the mean score for passive IR was 6.84 (SD: 1.75). No difference was found between fIR and passive IR (P = .328). No statistical difference was found between fIR and glenosphere size (P = .562) and fIR and size of the liner (P = .429). Significant statistical correlations have been found between AP and ML coracoid distances and the two groups (AP in group A: 28.50 and B: 31.265, P = .034; ML in group A: 23.053 and B: 14.27, P < .001).
Our study demonstrated that coracoid morphometry, evaluated as glenocoracoid distance, significantly impact IR outcomes in a 145° neck shaft angle RSA; in particular, a high ML glenocoracoid distance (>23 mm) was found to be determinant. This anatomical parameter should be considered in the preoperative planning of RSA and additional surgical strategies addressed in order to gain satisfactory fIR.
Does isolated glenosphere lateralization affect outcomes in reverse shoulder arthroplasty?
2023, Orthopaedics and Traumatology: Surgery and Research
While lateralization of the glenohumeral center of rotation during reverse shoulder arthroplasty (RSA) has benefits of maintaining tension on the remaining rotator cuff and decreasing implant impingement on the glenoid, few clinical studies have evaluated the isolated effect of glenoid lateralization in RSA. The purpose of this study was to evaluate if clinical outcomes are affected by isolated glenosphere lateralization using a single implant design.
A retrospective review from a multicenter shoulder arthroplasty research database was performed between 2011 and 2018 using a single implant system to perform this case-controlled study. Inclusion criteria included primary RSAs with adequate preoperative and postoperative active and passive range of motion (ROM) measurements, outcome scores, and a minimum two-year follow-up. Revision shoulder arthroplasties and RSA for fractures were excluded from analysis. 102 RSAs (61 females, 41 males) using a +4 mm lateralized glenosphere were compared to 102 sex, age, and glenosphere diameter matched control shoulders with standard glenospheres (whose center of rotation (CoR) is 2 mm lateral to the glenoid fossa). The mean age at surgery was 70.4 years. Mean follow up was 43.6 + 18.9 months. All RSAs were performed with the same implant system (Equinoxe, Exactech, Gainesville, FL). Clinical outcome measures included ROM, ASES, Constant, UCLA, SST, SPADI scores, and VAS pain scores. We used the chi-squared test and Fisher exact test for bivariate analysis and the student t-test for continuous variables.
Both groups were of similar average age and follow-up. They also had comparable rates of prior surgery and comorbidities. The lateralized glenosphere group had a slightly higher BMI (31.2 vs. 29.2, p = 0.04). Both groups demonstrated significant improvements in all outcome scores that exceeded the MCID and the SCB. The groups demonstrated similar preoperative, postoperative and improvements in ROM as well as outcome scores. The overall complication rate was similar between groups (4% in lateralized and 5% in controls, p = 0.73). Scapular or acromial fractures differences were not statistically significant between groups (1% in lateralized group vs. 3% in standard group, p = 0.31). Scapular notching was more frequent in the standard group compared to the lateralized group (9% vs. 2%, p = 0.03).
In a medialized glenosphere/lateralized humerus design, a +4 mm lateralized glenosphere provided no significant advantage in postoperative pain, ROM, or outcome scores. However, lateralized glenospheres did demonstrate significantly lower scapular notching rates.
III; retrospective cohort comparison; treatment study.
Factors affecting internal rotation following total shoulder arthroplasty
2022, JSES Reviews, Reports, and Techniques
Reverse shoulder arthroplasty (RSA) was developed in the late twentieth century to provide a stable arthroplasty option for patients with rotator cuff deficiency arthropathy. Since its inception, there have been changes in materials, design, and positioning. One of the persistent clinical issues has been difficulty with internal rotation (IR) and the associated difficulty with behind the back activities. Implant design, positioning, and the available soft tissues may influence IR after RSA. The purpose of this systematic review is to assess factors that impact IR following RSA.
The literature search, based on PRISMA guidelines, used 4 databases: Pubmed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials. We included clinical trials that compared different implantation and design modifications and assessed IR.
Of the 617 articles identified in the initial search, 46 satisfied the inclusion criteria. The articles explored multiple factors of RSA and their effects on IR, including humeral and glenoid components and muscle function and integrity. Among humeral factors affecting rotation, there was a broad consensus that: IR decreases as retroversion increases, humeral neck-shaft angle less than 155° improves IR, lateralized humeral offset does not improve IR, and shallow cups improve IR. Insert thickness was not associated with a reproducible effect. Of the studies evaluating the effect of glenoid components, there was majority agreement that glenosphere lateralization improved IR, and there were mixed results regarding the effects of glenosphere size and tilt. Others included one study in each: glenoid overhang, retroversion, and baseplate. One study found an association between teres minor insufficiency and improved IR, with mixed results in the presence of fatty infiltration in both teres minor and subscapularis. Most studies noted subscapularis repair had no effect on IR.
Prosthetic variables affecting IR are not widely studied. Based on the existing literature, evidence is conflicting. More research needs to be undertaken to gain a greater understanding regarding which factors can be modified to improve IR in RSA patients.
Factors associated with improvement or loss of internal rotation after reverse shoulder arthroplasty
2022, Journal of Shoulder and Elbow Surgery
Citation Excerpt :
The prosthesis used in this study uses an onlay lateralized humeral component with a 145° neck angle and a slightly lateralized glenosphere positioned inferior on the glenoid face.33 Biomechanical and clinical studies suggest that a lateralized glenosphere, inferior glenosphere positioning, and larger glenosphere diameter can improve impingement-free motion and rotation.19,2025,27,28,32,33,45 The finding that larger glenosphere diameter (and larger humeral stems) is associated with loss of IR is contradictory but is very likely confounded by male sex as male patients typically receive larger-diameter humeral stems and glenospheres than female patients.
Internal rotation (IR) with reverse total shoulder arthroplasty (rTSA) can be unpredictable. Identifying the factors associated with loss of or improved IR could aid preoperative patient counseling. This study quantifies the change in IR experienced by rTSA patients with nonfracture indications and identifies the patient, implant, and operative factors associated with IR loss or gain at 2-year minimum follow-up.
A total of 1978 primary rTSA patients were analyzed from an international database of a single rTSA prosthesis to quantify IR at 2 years’ minimum follow-up. rTSA patients were divided into 2 cohorts based on their preoperative IR score, with group 1 patients having less active IR as defined by a preoperative IR score ≤3 and group 2 patients having greater active IR as defined by a preoperative IR score ≥4 (ie, L5 or higher). For both group 1 and 2 patients, univariate and multivariate analyses were performed to quantify the risk factors associated with IR loss after rTSA.
Overall, 58.9% of rTSA patients experienced IR improvement and 17.0% lost IR after rTSA. The occurrence of IR loss or gain was dependent on preoperative IR score, as 73.2% of group 1 patients improved IR and only 40.1% of group 2 patients improved IR, whereas 31.0% of group 2 patients lost IR and only 6.3% of group 1 patients lost IR after rTSA. Numerous risk factors for IR loss were identified. For group 1 patients, male sex (P = .004, odds ratio [OR] = 2.056), tobacco usage (P = .004, OR = 0.348), larger humeral stem diameter (P = .008, OR = 0.852), and not having subscapularis repaired (P = .002, OR = 2.654) were significant risk factors for IR loss. For group 2 patients, male sex (P = .005, OR = 1.656), higher body mass index (P = .002, OR = 0.946), a diagnosis other than osteoarthritis (P < .001, OR = 2.189), nonaugmented baseplate usage (P < .001, OR = 2.116), and not having subscapularis repaired (P < .001, OR = 3.052) were significant risk factors for IR loss.
The majority of patients improve IR after rTSA in the nonfracture setting. rTSA patients with substantial IR prior to surgery had a greater probability for losing IR compared to patients with poor preoperative IR. Numerous risk factors for IR loss were identified; these risk factors are useful for counseling patients considering rTSA, as some patients are more likely to lose IR than others.
Extension of the shoulder is essential for functional internal rotation after reverse total shoulder arthroplasty
2022, Journal of Shoulder and Elbow Surgery
Disabling loss of functional internal rotation (fIR) after reverse total shoulder arthroplasty (RTSA) is frequent but not well understood. This study tested the hypothesis that limitation of fIR after RTSA is not primarily related to a deficit in internal rotation.
Fifty patients (mean age at RTSA, 74 ± 11.7 years) who were consecutively seen at a yearly follow-up visit at 1-10 years (median, 4 years) after RTSA were prospectively examined with special attention to fIR. Patients with axillary nerve or deltoid dysfunction were excluded. Relative (age- and sex-adjusted) Constant-Murley scores (CSs) and Subjective Shoulder Values were assessed preoperatively and at final follow-up. In addition, active extension and 4 postoperative activities of daily living (ADLs) requiring fIR were tested at follow-up. Rotator cuff fatty infiltration and notching were evaluated radiographically. For analysis, patients were divided into a group with poor fIR (fIR–, n = 19), defined as ≤2 internal-rotation points in the CS, and a group with good fIR (fIR+, n = 31), defined as ≥4 internal-rotation points in the CS.
Active extension of the contralateral shoulders was comparable in the fIR– group (mean, 60.3° [standard deviation (SD), 11.2°]) and fIR+ group (66.1° [SD, 14.2°]). Postoperatively, a difference in active extension between the unaffected and operated sides was present in both groups and averaged 16° (55° [SD, 14.3°] in fIR+ group and 39.1° [SD, 10.8°] in fIR– group; P < .001). No patient in the fIR+ group had active extension < 40° (range, 40°-85°). Shoulders with extension ≥ 40° but unsatisfactory fIR had restricted passive internal rotation in extension. The ability to perform ADLs behind the back correlated better with shoulder extension than with so-called fIR measurements in the CS.
Functional internal rotation after RTSA requires at least 40° of shoulder extension. If fIR is unsatisfactory despite 40° of extension, passive restriction of internal rotation in full extension is the limiting factor. It is crucial to preserve or restore active shoulder extension to allow ADLs involving internal rotation.

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Implant impingement during internal rotation after reverse shoulder arthroplasty. The effect of implant configuration and scapula anatomy: A biomechanical study

Highlights

Abstract

Background

Methods

Findings

Interpretation

Introduction

Section snippets

Specimen preparation and mounting

Results

Discussion

Conclusions

Conflict of interest statement

Acknowledgments

J. Shoulder Elb. Surg.

J. Shoulder Elb. Surg.

J. Shoulder Elb. Surg.

Clin. Biomech.

J. Shoulder Elb. Surg.

J. Shoulder Elb. Surg.

J. Shoulder Elb. Surg.

J. Shoulder Elb. Surg.

J. Shoulder Elb. Surg.

J. Biomech.

Prosthetic overhang is the most effective way to prevent scapular conflict in a reverse total shoulder prosthesis

Acta Orthop.

The reverse shoulder prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency

J. Bone Joint Surg.