A gender and size specific evaluation of inlay versus onlay stem designs in achieving lateralization and distalization in reverse shoulder arthroplasty

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Aim of this study was to gender- and size-specifically assess the best implant design selection in order to reduce the risk of SSFF and to optimize lateralization, distalization, and bony impingement-free range of motion (ROM) in patients undergoing RSA. Methods: Computed tomography scans from 30 osteoarthritic patients (f:15, m:15) and 20 cuff tear arthropathy patients (f:10, m:10) were used to virtually simulate a RSA. The efficacy of inlay vs onlay stems combined with two glenospheres (36mm vs 42mm) in achieving ROM, lateralization, and distalization was evaluated. Moreover, gender and patients constitution were correlated to humeral size by radiologically measuring the best-fit circle of the humeral head. Results: A different amount of relative lateralization was achieved in both genders using large glenospheres and onlay designs. Latter yielded a higher ROM in all planes for men and women with a 42 mm glenosphere; with the 36mm glenosphere, an increased ROM was observed only in men. In women, this configuration only improved abduction. When adjusting the absolute amount of lateralization to humerus’ size and regardless of implant type, women received greater relative lateralization than men; with a 42mm glenosphere and an onlay system, women lateralized 19% vs 8.0% observed in men. Conclusion : The relative lateralization achieved using onlay design is much higher in women than men. Humeral lateralization using onlay designs should be used cautiously in women, as they may enhance the risk for developing SSFF. Our results point out that glenoid lateralization should be used instead to reduce inferior notching and to improve ROM, especially in small women. Level of Evidence: Basic Science Study, Computer Modeling reverse shoulder arthroplasty lateralization distalization onlay inlay humeral stem Gender Medicine Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Reverse shoulder arthroplasty (RSA) is a reliable treatment option to restore joint mobility and reduce pain for cuff-deficient or severe arthritic shoulders. Yet, worse postoperative outcomes have been reported in female patients compared with men [1, 2]. For example, in a cohort of 660 patients undergoing RSA, Friedman et al., reported a better postoperative range of motion (ROM) in male patients, who displayed higher abduction (ABD), forward flexion, and passive external rotation (ER) compared with their female counterparts [1]. This gender disparity can be partially attributed to the anatomical shoulder differences observed between men and women, which influence joint biomechanics. RSA “reverses” the native articular concavities of the glenoid and humerus, which results in several biomechanical advantages relative to the native shoulder [3, 4]. By the medialization of the center of rotation (COR)[4], the traditional “Grammont-designed RSA” improves ROM and reduces the risk of implant failure. However, this technique it is not exempt of complications: a scapular notching rate of approximately 75% have been previously described in patients undergoing Grammont-designed RSA, increasing up to 95% among young patients [5]. To prevent scapular notching and enhance ROM, designs lateralizing the glenosphere, humeral tray, or both components, have recently emerged [6-8]. Moreover, onlay-curved stem designs and decreasing the humeral neck-shaft angle (NSA) to 145° NSA provide a higher degree of lateralization and bony impingement-free ROM[8, 9] than implants with 155°NSA (inlay or Grammont-type designs). Lateralization improves the torque generated by remnants of the rotator cuff but decreasing the lever arm especially of the mid deltoid muscle and therefore enhances fiber recruitment, which results in greater shearing forces[10, 11]. This augmented load on the acromion can result in an increased incidence of scapular spine fatigue fractures (SSFF)[12]. For example, a clinical comparison of both designs showed that the modified onlay system was superior than the inlay design in achieving higher ROM and reducing the risk of scapular notching, but these benefits come at the expense of a a three-fold increased SSFF incidence [10, 12]. Notably, SSFF occur predominantly in women, and a positive correlation between osteoporosis and risk of developing an SSFF has been previously established [13, 14]. Hence, it is possible that the greater levels of humeral lateralization achieved by onlay designs might translate into a higher risk of experiencing SSFFs in female patients. However, studies addressing the impact of implant design and component lateralization on the clinical outcomes of RSA specifically in female patients are scarce. Therefore, we used a virtual computer simulation to evaluate the influence of onlay vs. inlay stems in addition to glenosphere size on lateralization, distalization, and bony impingement-free ROM with regards to gender and patient’s constitution. We hypothesized that small women will receive greater lateralization with modular onlay systems than men. Our second hypothesis was that inlay and onlay designs yield different ROM. Our null hypothesis was that both stems achieve the same lateralization and ROM in both female and male patients. Methods We analyzed computed tomography (CT) scans and standardized preoperative true anteroposterior (AP) and axial radiographs from 25 male and 25 female patients that have suffered from primary osteoarthritis (OA) (n=30) or cuff tear arthropathy (CTA) (n=20) and were treated with a RSA by the senior author (F.G.). In addition to skeletal size and weight from the patients’ files, radiographic measurements from preoperative x-rays were used to evaluate patients’ constitution more accurately. To determine humeral head size, a best-fit circle was drawn onto the humeral head and aligned from the humeral joint surface up to the greater tuberosity in true AP and axial radiographs, which enabled us to determine best-fit circle’s radius. Glenoid’s height was measured in true AP and glenoid’s width was determined using axial radiographs (Fig.1). A correlation among these four measurements and patients’ height, weight, and body mass index (BMI) was performed (Table 1 and Table 2). All CT scans were processed by a validated three-dimensional (3D) software program ( Glenosys , Imascap, Brest, France)[15]. This software enables the virtual implantation of the humeral and glenoid components and generates a 3D reconstruction of the joint while measuring glenoid version, inclination, and posterior humerus subluxation by a multiple spot analysis of the scapula [16]. A RSA was virtually simulated in all 50 patients to reconstruct each patient’s shoulder using four possible configurations: i) a 36mm glenosphere and an inlay stem; ii) a 36mm glenosphere and an onlay stem; iii) a 42mm glenosphere and an inlay stem; and iv) a 42mm glenosphere and an onlay design. On the glenoid side, a standardized angled bone block was used for augmentation behind the base plate to neutralize all posterior and cranial glenoid defects similar to those conducted by the surgeon in real life. This angled bony augmentation was placed to achieve a neutral inclination and version on the inferior glenoid to allow for baseplate placement with no inferior bony overhang at the most lateral point allowing for maximum glenoid seating by the software. In all patients, either a small centered 36 mm glenosphere or a large 42mm glenosphere with no eccentricity was virtually implanted. On the humeral side two different systems were used: the onlay design modular platform Tonier Flex prosthesis (Stryker Corp., Kalamazoo, MI, USA) with a NSA of 145° and the inlay design “Grammont-style” Aequalis Reverse II (Stryker Corp., Kalamazoo, MI, USA) with a NSA of 155° (both shown in Figure 2). The humeral cut was performed at the anatomic neck with the lateral metaphyseal component aligned at the greater tuberosity. For each configuration, the global ROM defined as bony impingement-free in adduction (ADD), abduction (ABD), forward flexion (FLX), extension (EXT), external rotation (ER) and internal rotation (IR) was tested with the arm at the side. The impingement-free ROM simulation is based on either the collision between two bony structures or the implant and the bone (e.g. scapula or acromion). The software allows for a resolution of 1°. The maxim values for each bony-free impingement ROM were documented for each configuration and patient. Due to the sample size, we have performed (non)-parametric tests. The Man-Whitney-U test was performed for both concurrent factors (i.e., glenosphere size and stem design). Significance level was set at 0.05. Results Patients characteristics In our study population, women had a smaller mean (SD) height (162.6 ±5.3cm) and lower mean weight (80.4±16.1kg) than men (175.8±6.2 cm and 92.2±16.2kg), respectively (Table 1). Accordingly, all two-dimensional (2D) radiographic measurements (i.e. humerus radius, glenoid height, and glenoid width) were smaller in women than in men and are displayed in Table 1. We observed that the greatest correlation between patient’s skeletal size and joint anatomy was defined by the radius of best-fit circus of the humeral head and was therefore used from here on when referring to humeral size (Table 2). At the pathology level, glenoid inclination and retroversion were on average marginally higher in female than in male patients (Table 1).Patients with primary OA showed on average a greater amount of glenoid retroversion and posterior humerus subluxation compared with CTA patients. A higher glenoid inclination was observed in CTA patients compared to OA patients (Supplementary Table 1). Influence of glenosphere size on lateralization and range of motion The use of a 42mm glenoshpere combined with the onlay system led to greater lateralization in both genders compared to the one achieved when using a 36mm glenosphere (Table 3). The results for pairwise comparison achieved with each configuration are presented in Table 3 and Figure 3. A significant increase in ADD ( P ≤ 0.046), EXT ( P ≤ 0.018), and ER ( P ≤ 0.025) was observed in both genders with the use of a 42mm glenosphere and an onlay implant, which led to a greater impingement free zone with the arm at the side. In contrast, an increased glenosphere size in combination with the inlay design did not improve ROM neither in men nor in women, with the exception of IRO in men (Table 3 and Figure 3). Forward flexion was not improved when increasing glenosphere size in none of the cohorts regardless of the implant type. Influence of stem design on lateralization, distalization, and range of motion Onlay systems were superior over inlay systems in achieving a higher level of lateralization, regardless of the glenosphere size or gender (Table 4). The pairwise comparison for each parameter and each configuration is shown in Table 4. When combined with a 42mm glenosphere, the onlay system yielded a significant improvement in both men and women in ADD ( P ≤ 0.001), ABD ( P ≤ 0.001), IRO ( P ≤ 0.023), ER ( P ≤ 0.001), and EXT ( P ≤ 0.001) (Figure 4). However, no significant differences were observed in the amount of distalization achieved by both implants. The inlay design, however, led to an impingement between greater tuberosity and the acromion, which increased abduction in this static shoulder simulation. No significant changes in distalization were observed with both type of implants (Table 4). Absolute and relative lateralization depending on patient’s constitution Comparison of the absolute and relative lateralization achieved by each configuration is displayed in Figure 5. The greatest amount of lateralization in male patients was obtained with the use of onlay systems combined with a 42mm glenosphere, which resulted in an absolute lateralization of 4.08 mm and represents an increase of 8% of lateralization relative to the humeral size. However, a similar degree of absolute lateralization (5.44 mm) can be accomplished in female patients with the use of smaller glenospheres, which corresponds to a relative lateralization of 12% (Figure 5). Indeed, onlay systems combined with 42mm glenospheres yielded an increase of 19% relative lateralization in women, which is almost three times the amount of lateralization achieved in men with the optimal configuration (Figure 5). This high degree of relative lateralization observed in female patients can translate in higher shearing forces into the acromion, which can eventually lead to the development of SSFFs[17]. Discussion Reverse shoulder arthroplasty was evolving towards systems that increase lateralization both on the glenoid and humeral side, with the ultimate goal to prevent scapular notching and improve ROM. However, the “ideal amount of lateralization”, especially in female patients, remains unknown to date. The purpose of our study was to evaluate the biomechanical effects of glenoid and humeral lateralization on ROM on female and male patients. As variations in implant design impact on shoulder kinematics, and in turn, on functional outcomes, we performed a gender-specific virtual simulation of a RSA with onlay and inlay systems combined with the two common glenosphere sizes. Our study showed that increasing humeral lateralization with the use of onlay systems had a greater effect in achieving free-impingement passive ROM compared with the use of larger glenospheres. Even when combined with 36mm glenospheres, the use of onlay systems in women, whose physical constitution tends to be smaller than men, resulted in a relative lateralization much higher than in men implanted with large glenospheres. However, one of the main drawback of high levels of lateralization is the risk of stressing the acromion, which can lead to the development of SSFFs. Our data suggests that women are more susceptible to complications due to the higher lateralization that they received compared with men when treated with either onlay or inlay systems. The gender-specific changes to bone density remain a large confounder. We observed that the use of large glenosphers translated into higher lateralization and greater impingement-free ROM in silico. These results are in agreement with previous studies, where glenoid lateralization can improve ROM regardless of the humeral inclination [8, 18, 19]. In a cadaveric study, Berhouet et al., demonstrated that greater ADD and free-impingement ROM was achieved when using a 42 mm glenosphere than when using a 36mm glenosphere [19]. A higher level of lateralization was theorized to minimize scapular notching. This was recently demonstrated in a multicenter clinical study including 61 female and 41 male patients undergoing RSA and receiving either a medialized or lateralized glenosphere. While the reported scapular notching rate was lower in the lateralized group, the incidence of SSFF was similar between groups [20]. Our study demonstrated that humeral lateralization together with 145° inclination had the greatest impact on impingement-free passive ROM compared to the classic Grammont-design. Comparison of ROM achieved by inlay versus onlay designs revealed superior results in ADD, EXT, and ER angles for both genders with the use of onlay systems. The use of inlay systems improved IRO, but this improvement was only significant for men. Our results supports Werthel’s theoretical findings that more than double of lateralization can be achieved on the humeral side compared with the glenoid side[17]. However, we found that ABD was significantly lower when increasing humeral lateralization, probably due to the lateralization of the greater tuberosity and abutment at the acromion which in vivo may be compensated by scapulothoracic movement, which is not present in our simulating system. Contrary to lateralization, which clearly increased with the use of onlay systems, no significant changes in distalization were observed with the use of any type of implant. This may be due to different resection planes of humerus cuts when using inlay or onlay design stems. Moreover, the resection angle is altered with a different NSA as the greater tuberosity is aligned to the humeral metaphysis. This may explain the lack of differences in distalization when using different stem systems. The increase in glenosphere size results in a mean increase of distalization of 1mm regardless of implant configuration.. We postulate that with the use of implants currently available on the market, and the male patients-based assumption that a higher lateralization improves ROM, women are predisposed to receive an excessive amount of lateralization relative to their joint and body sizes. While the classical 155° Grammont inlay prosthesis led in our study to the medialization of the COR in men, the same design already let to lateralization of COR and the onlay design resulted in a high degree of relative lateralization in female patients. Indeed, we observed that women with a 36mm glenosphere and onlay design obtained over 4% of lateralization more (compared to joint size) than men when using a 42 mm glenosphere and onlay design. These totally disproportionate effects of standard implant sizes on men and women should be targeted by prostheses’ manufactures, as there should be a greater variety of component sizes on the market to allow for individual risk analysis. Limitations of this study include that the evaluation of implants was restricted to one platform onlay design versus one curved inlay stem design, and that both were from the same manufacturer. Moreover, both stems had different NSA, which has been reported to influence the lateralization achieved on the humeral side[8]. Taken together, our results cannot be extrapolated to other prostheses available in the market, as a more comprehensive and precise comparison needs to be performed to reach conclusion about the optimal implant design for each gender [8, 21, 22]. An additional limitation is that a mixed configuration (i.e. 42mm glenosphere with a 36mm stem) could not be simulated with our software, even if such configuration is often used by surgeons and represents a viable option for some patients. This configuration presents several advantages over the ones above-described, such as greater ADD range with less lateralization. Furthermore, the computational simulation did not enable us to evaluate neither scapulothoracic movement nor soft tissue tensioning with regards to pre-tensioning of the delta muscle or the remaining cuff. Strength of this study is, that those two implant configurations represent the traditional Grammont design (155° inlay design) with one of the most common designs allowing for humeral lateralization. Our study suggests that surgeons should evaluate lateralization individually for each patient by 3D software-based planning and thoroughly assess the trade-off between increased ROM and biomechanical side effects based on patient’s constitution, gender, and bone quality. Conclusion In reverse shoulder arthroplasty, relative lateralization is much higher in women, especially when using an onlay designs and large glenospheres. Humeral lateralization using new modular onlay systems should be used cautiously especially for small women. Glenoid lateralization can help to reduce impingement by increasing ROM and can therefore be used more effectively for small women. Large glenospheres in combination with lateralizing onlay stems for women bear therefore high risks of developing scapular spine fatigue fractures. Declarations Ethical approval The study was performed in accordance with the ethical standards of the Charité Ethics Committee (Charitéplatz 1, 10117 Berlin, Germany Nr. EA1/016/24), and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all subjects. Consent for publication All authors made substantial contributions to the drafting, revision and final approval of the version to be submitted, believe the manuscript represents honest work and give consent for publication. Availability of data The datasets used and/or analyzed during the current study available from the corresponding author upon reasonable request. Declaration of competing interest Prof. Gohlke was consultant for Tornier/Wright/Stryker medical company but without accepting any royalties. There is no conflict of interest regarding the subject of this article. The rest of the authors and none of their family relatives received any royalties or fees from any company. Role of funding source No funding was received for this study. Acknowledgements The authors thank A. Rodrigues-Villalon, PhD for the editing and final preparation of this manuscript. Authorship contribution statement All authors contributed to the conception and design of the study, acquisition of data, and analysis and interpretation of data. All authors contributed to the drafting and revision of the manuscript. Specific contributions are as follows: JPI and FG designed and conceptualized the study; JPI and TI analyzed the data; JPI wrote the manuscript; JPI, PA, LE, TI, and FG revised the manuscript; JPI and FG took joint responsibility for the integrity of the work as a whole. References R. J. 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King et al. , "Does isolated glenosphere lateralization affect outcomes in reverse shoulder arthroplasty?," (in eng), Orthop Traumatol Surg Res, vol. 109, no. 4, p. 103401, Jun 2023, doi: 10.1016/j.otsr.2022.103401. A. Lädermann et al. , "Effect of humeral stem and glenosphere designs on range of motion and muscle length in reverse shoulder arthroplasty," (in eng), Int Orthop, vol. 44, no. 3, pp. 519-530, Mar 2020, doi: 10.1007/s00264-019-04463-2. G. D. Langohr, R. Willing, J. B. Medley, G. S. Athwal, and J. A. Johnson, "Contact mechanics of reverse total shoulder arthroplasty during abduction: the effect of neck-shaft angle, humeral cup depth, and glenosphere diameter," J Shoulder Elbow Surg, vol. 25, no. 4, pp. 589-97, Apr 2016, doi: 10.1016/j.jse.2015.09.024. Tables Tables 1-4 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Onlayvsinlaytable1.docx Onlayvsinlaytable2.docx Onlayvsinlaytable3.docx Onlayvsinlaytable4.docx Onlayvsinlaysuppl1.docx Cite Share Download PDF Status: Published Journal Publication published 04 Sep, 2024 Read the published version in BMC Musculoskeletal Disorders → Version 1 posted Editorial decision: Revision requested 15 Apr, 2024 Reviews received at journal 08 Apr, 2024 Reviewers agreed at journal 29 Mar, 2024 Reviews received at journal 28 Mar, 2024 Reviewers agreed at journal 27 Mar, 2024 Reviewers invited by journal 15 Mar, 2024 Editor assigned by journal 15 Mar, 2024 Editor invited by journal 09 Mar, 2024 Submission checks completed at journal 09 Mar, 2024 First submitted to journal 26 Feb, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3990719","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":277746198,"identity":"d2477c8c-be1f-4fba-8c76-1ad9f529deea","order_by":0,"name":"Jan-Phillip 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Universitaetsmedizin","correspondingAuthor":false,"prefix":"","firstName":"Nevin","middleName":"","lastName":"Abu-Zeid","suffix":""},{"id":277746200,"identity":"d4ca68ca-d3e6-471d-8184-6b6d5732cb97","order_by":2,"name":"Larissa Eckl","email":"","orcid":"","institution":"Schulthess Clinic","correspondingAuthor":false,"prefix":"","firstName":"Larissa","middleName":"","lastName":"Eckl","suffix":""},{"id":277746201,"identity":"a2e6b75a-8c39-4816-b3f0-f8b03e5088ab","order_by":3,"name":"Tankred Imiolczyk","email":"","orcid":"","institution":"University of Mannheim","correspondingAuthor":false,"prefix":"","firstName":"Tankred","middleName":"","lastName":"Imiolczyk","suffix":""},{"id":277746202,"identity":"1b6241b1-d161-41ae-b736-b9c5d242eab6","order_by":4,"name":"Frank Gohlke","email":"","orcid":"","institution":"Rhoen Klinik, Bad Neustadt/Saale","correspondingAuthor":false,"prefix":"","firstName":"Frank","middleName":"","lastName":"Gohlke","suffix":""}],"badges":[],"createdAt":"2024-02-26 11:00:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3990719/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3990719/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12891-024-07818-y","type":"published","date":"2024-09-04T16:05:32+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":52618499,"identity":"a03315fd-8966-4a9c-962b-edf67fc3f2eb","added_by":"auto","created_at":"2024-03-13 16:30:16","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":258670,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend.\u003c/p\u003e","description":"","filename":"Onlayvsinlayfig11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3990719/v1/a76e164026f451ce955a1eba.jpg"},{"id":52617785,"identity":"8c294b98-d464-448c-9617-e1be36128cd4","added_by":"auto","created_at":"2024-03-13 16:22:16","extension":"jpg","order_by":2,"title":"Figure 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16:26:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1917973,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3990719/v1/2d50df1a-a073-407d-9c0e-e01df43273b1.pdf"},{"id":52617783,"identity":"8a08096d-17fa-4311-bd66-98895a7951d8","added_by":"auto","created_at":"2024-03-13 16:22:16","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":16786,"visible":true,"origin":"","legend":"","description":"","filename":"Onlayvsinlaytable1.docx","url":"https://assets-eu.researchsquare.com/files/rs-3990719/v1/fb4c2c6addf2d52db2532ad5.docx"},{"id":52617788,"identity":"d0dfa2ab-eae6-4424-85ef-4ddb7afa3bf9","added_by":"auto","created_at":"2024-03-13 16:22:16","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":15372,"visible":true,"origin":"","legend":"","description":"","filename":"Onlayvsinlaytable2.docx","url":"https://assets-eu.researchsquare.com/files/rs-3990719/v1/0e9ad424727e099cc1da7473.docx"},{"id":52617791,"identity":"56537b13-a4ef-439e-a462-60a8a9ba5a59","added_by":"auto","created_at":"2024-03-13 16:22:16","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":17110,"visible":true,"origin":"","legend":"","description":"","filename":"Onlayvsinlaytable3.docx","url":"https://assets-eu.researchsquare.com/files/rs-3990719/v1/8ca89d860293c03746058bf9.docx"},{"id":52617790,"identity":"d8676602-198a-47e0-80c8-4d0dd96ff01e","added_by":"auto","created_at":"2024-03-13 16:22:16","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":17132,"visible":true,"origin":"","legend":"","description":"","filename":"Onlayvsinlaytable4.docx","url":"https://assets-eu.researchsquare.com/files/rs-3990719/v1/83b254fe3e199d84749fb7a2.docx"},{"id":52617792,"identity":"a8ad0185-c07d-4cbf-9796-ed67dda672ea","added_by":"auto","created_at":"2024-03-13 16:22:16","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":19005,"visible":true,"origin":"","legend":"","description":"","filename":"Onlayvsinlaysuppl1.docx","url":"https://assets-eu.researchsquare.com/files/rs-3990719/v1/538cf58bfb9e58dc25ca398e.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"A gender and size specific evaluation of inlay versus onlay stem designs in achieving lateralization and distalization in reverse shoulder arthroplasty","fulltext":[{"header":"Introduction","content":"\u003cp\u003eReverse shoulder arthroplasty (RSA) is a reliable treatment option to restore joint mobility and reduce pain for cuff-deficient or severe arthritic shoulders. Yet, worse postoperative outcomes have been reported in female patients compared with men [1, 2]. For example, in a cohort of 660 patients undergoing RSA, Friedman et al., reported a better postoperative range of motion (ROM) in male patients, who displayed higher abduction (ABD), forward flexion, and passive external rotation (ER) compared with their female counterparts [1]. This gender disparity can be partially attributed to the anatomical shoulder differences observed between men and women, which influence joint biomechanics. RSA \u0026ldquo;reverses\u0026rdquo; the native articular concavities of the glenoid and humerus, which results in several biomechanical advantages relative to the native shoulder [3, 4]. By the medialization of the center of rotation (COR)[4], the traditional \u0026ldquo;Grammont-designed RSA\u0026rdquo; improves ROM and reduces the risk of implant failure. However, this technique it is not exempt of complications: a scapular notching rate of \u0026nbsp; approximately 75% \u0026nbsp;have been previously described in patients undergoing Grammont-designed RSA, increasing up to 95% among young patients [5]. To prevent scapular notching and enhance ROM, designs lateralizing the glenosphere, humeral tray, or both components, have recently emerged [6-8]. Moreover, onlay-curved stem designs and decreasing the humeral neck-shaft angle (NSA) to 145\u0026deg; NSA provide a higher degree of lateralization and bony impingement-free ROM[8, 9] than implants with 155\u0026deg;NSA (inlay or Grammont-type designs). Lateralization improves the torque generated by remnants of the rotator cuff but decreasing the lever arm especially of the mid deltoid muscle and therefore enhances fiber recruitment, which results in greater shearing forces[10, 11]. This augmented load on the acromion can result in an increased incidence of scapular spine fatigue fractures (SSFF)[12]. For example, a clinical comparison of both designs showed that the modified onlay system was superior than the inlay design in achieving higher ROM and reducing the risk of scapular notching, but these benefits come at \u0026nbsp;the expense of a a three-fold increased SSFF incidence [10, 12]. Notably, SSFF occur predominantly in women, and a positive correlation between osteoporosis and risk of developing an SSFF has been previously established [13, 14]. Hence, it is possible that the greater levels of humeral lateralization achieved by onlay designs might translate into a higher risk of experiencing SSFFs in female patients. However, studies addressing the impact of implant design and component lateralization on the clinical outcomes of RSA specifically in female patients are scarce. Therefore, we used a virtual computer simulation to evaluate the influence of onlay vs. inlay stems in addition to glenosphere size on lateralization, distalization, and bony impingement-free ROM with regards to gender and patient\u0026rsquo;s constitution. We hypothesized that small women will receive greater lateralization with modular onlay systems than men. Our second hypothesis was that inlay and onlay designs yield different ROM. Our null hypothesis was that both stems achieve the same lateralization and ROM in both female and male patients.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eWe analyzed computed tomography (CT) scans and standardized preoperative true anteroposterior (AP) and axial radiographs from 25 male and 25 female patients that have suffered from primary osteoarthritis (OA) (n=30) or cuff tear arthropathy (CTA) (n=20) and were treated with a RSA by the senior author (F.G.). In addition to skeletal size and weight from the patients\u0026rsquo; files, radiographic measurements from preoperative x-rays were used to evaluate patients\u0026rsquo; constitution more accurately. To determine humeral head size, a best-fit circle was drawn onto the humeral head and aligned from the humeral joint surface up to the greater tuberosity in true AP and axial radiographs, which enabled us to determine best-fit circle\u0026rsquo;s radius. Glenoid\u0026rsquo;s height was measured in true AP and glenoid\u0026rsquo;s width was determined using axial radiographs (Fig.1). A correlation among these four measurements and patients\u0026rsquo; height, weight, and body mass index (BMI) was performed (Table 1 and Table 2).\u003c/p\u003e\n\u003cp\u003eAll CT scans were processed by a validated three-dimensional (3D) software program (\u003cem\u003eGlenosys\u003c/em\u003e, Imascap, Brest, France)[15]. This software enables the virtual implantation of the humeral and glenoid components and generates a 3D reconstruction of the joint while measuring glenoid version, inclination, and posterior humerus subluxation by a multiple spot analysis of the scapula [16]. A RSA was virtually simulated in all 50 patients to reconstruct each patient\u0026rsquo;s shoulder using four possible configurations: i) a 36mm glenosphere and an inlay stem; ii) a 36mm glenosphere and an onlay stem; iii) a 42mm glenosphere and an inlay stem; and iv) a 42mm glenosphere and an onlay design. On the glenoid side, a standardized angled bone block was used for augmentation behind the base plate to neutralize all posterior and cranial glenoid defects similar to those conducted by the surgeon in real life. This angled bony augmentation was placed to achieve a neutral inclination and version on the inferior glenoid to allow for baseplate placement with no inferior bony overhang at the most lateral point allowing for maximum glenoid seating by the software. In all patients, either a small centered 36 mm glenosphere or a large 42mm glenosphere with no eccentricity was virtually implanted. On the humeral side two different systems were used: the onlay design modular platform Tonier Flex prosthesis (Stryker Corp., Kalamazoo, MI, USA) with a NSA of 145\u0026deg; and the inlay design \u0026ldquo;Grammont-style\u0026rdquo; Aequalis Reverse II (Stryker Corp., Kalamazoo, MI, USA) with a NSA of 155\u0026deg; (both shown in Figure 2). The humeral cut was performed at the anatomic neck with the lateral metaphyseal component aligned at the greater tuberosity. For each configuration, the global ROM defined as bony impingement-free in adduction (ADD), abduction (ABD), forward flexion (FLX), extension (EXT), external rotation (ER) and internal rotation (IR) was tested with the arm at the side. The impingement-free ROM simulation is based on either the collision between two bony structures or the implant and the bone (e.g. scapula or acromion). The software allows for a resolution of 1\u0026deg;. The maxim values for each bony-free impingement ROM were documented for each configuration and patient. Due to the sample size, we have performed (non)-parametric tests. The Man-Whitney-U test was performed for both concurrent factors (i.e., glenosphere size and stem design). Significance level was set at 0.05.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cem\u003ePatients characteristics\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eIn our study population, women had a smaller mean (SD) height (162.6 \u0026plusmn;5.3cm) and lower mean weight (80.4\u0026plusmn;16.1kg) than men (175.8\u0026plusmn;6.2 cm and 92.2\u0026plusmn;16.2kg), respectively (Table 1). Accordingly, all two-dimensional (2D) radiographic measurements (i.e. humerus radius, glenoid height, and glenoid width) were smaller in women than in men and are displayed in Table 1. We observed that the greatest correlation between patient\u0026rsquo;s skeletal size and joint anatomy was defined by the radius of best-fit circus of the humeral head and was therefore used from here on when referring to humeral size (Table 2).\u003c/p\u003e\n\u003cp\u003eAt the pathology level, glenoid inclination and retroversion were on average marginally higher in female than in male patients (Table 1).Patients with primary OA showed on average a greater amount of glenoid retroversion and posterior humerus subluxation compared with CTA patients. A higher glenoid inclination was observed in CTA patients compared to OA patients (Supplementary Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eInfluence of glenosphere size on lateralization and range of motion\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe use of a 42mm glenoshpere combined with the onlay system led to greater lateralization in both genders compared to the one achieved when using a 36mm glenosphere (Table 3). The results for pairwise comparison achieved with each configuration are presented in Table 3 and Figure 3. A significant increase in ADD (\u003cem\u003eP\u003c/em\u003e \u0026le; 0.046), EXT (\u003cem\u003eP\u0026nbsp;\u003c/em\u003e\u0026le; 0.018), and ER (\u003cem\u003eP\u003c/em\u003e \u0026le; 0.025) was observed in both genders with the use of a 42mm glenosphere and an onlay implant, which led to a greater impingement free zone with the arm at the side. In contrast, an increased glenosphere size in combination with the inlay design did not improve ROM neither in men nor in women, with the exception of IRO in men (Table 3 and Figure 3). Forward flexion was not improved when increasing glenosphere size in none of the cohorts regardless of the implant type. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eInfluence of stem design on lateralization, distalization, and range of motion\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eOnlay systems were superior over inlay systems in achieving a higher level of lateralization, regardless of the glenosphere size or gender (Table 4). The pairwise comparison for each parameter and each configuration is shown in Table 4. When combined with a 42mm glenosphere, the onlay system yielded a significant improvement in both men and women in ADD (\u003cem\u003eP\u003c/em\u003e \u0026le; 0.001), ABD (\u003cem\u003eP\u003c/em\u003e \u0026le; 0.001), IRO (\u003cem\u003eP\u003c/em\u003e \u0026le; 0.023), ER (\u003cem\u003eP\u003c/em\u003e \u0026le; 0.001), and EXT (\u003cem\u003eP\u003c/em\u003e \u0026le; 0.001) (Figure 4). However, no significant differences were observed in the amount of distalization achieved by both implants. The inlay design, however, led to an impingement between greater tuberosity and the acromion, which increased abduction in this static shoulder simulation. No significant changes in distalization were observed with both type of implants (Table 4).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAbsolute and relative lateralization depending on patient\u0026rsquo;s constitution\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eComparison of the absolute and relative lateralization achieved by each configuration is displayed in Figure 5. The greatest amount of lateralization in male patients was obtained with the use of onlay systems combined with a 42mm glenosphere, which resulted in an absolute lateralization of 4.08 mm and represents an increase of 8% of lateralization relative to the humeral size. However, a similar degree of absolute lateralization (5.44 mm) can be accomplished in female patients with the use of smaller glenospheres, which corresponds to a relative lateralization of 12% (Figure 5). Indeed, onlay systems combined with 42mm glenospheres yielded an increase of 19% relative lateralization in women, which is almost three times the amount of lateralization achieved in men with the optimal configuration (Figure 5). This high degree of relative lateralization observed in female patients can translate in higher shearing forces into the acromion, which can eventually lead to the development of SSFFs[17].\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eReverse shoulder arthroplasty was evolving towards systems that increase lateralization both on the glenoid and humeral side, with the ultimate goal to prevent scapular notching and improve ROM. However, the \u0026ldquo;ideal amount of lateralization\u0026rdquo;, especially in female patients, remains unknown to date. The purpose of our study was to evaluate the biomechanical effects of glenoid and humeral lateralization on ROM on female and male patients. As variations in implant design impact on shoulder kinematics, and in turn, on functional outcomes, we performed a gender-specific virtual simulation of a RSA with onlay and inlay systems combined with the two common glenosphere sizes.\u003c/p\u003e\n\u003cp\u003eOur study showed that increasing humeral lateralization with the use of onlay systems had a greater effect in achieving free-impingement passive ROM compared with the use of larger glenospheres. Even when combined with 36mm glenospheres, the use of onlay systems in women, whose physical constitution tends to be smaller than men, resulted in a relative lateralization much higher than in men implanted with large glenospheres. However, one of the main drawback of high levels of lateralization is the risk of stressing the acromion, which can lead to the development of SSFFs. Our data suggests that women are more susceptible to complications due to the higher lateralization that they received compared with men when treated with either onlay or inlay systems. The gender-specific changes to bone density remain a large confounder.\u003c/p\u003e\n\u003cp\u003eWe observed that the use of large glenosphers translated into higher lateralization and greater impingement-free ROM in silico. These results are in agreement with previous studies, where glenoid lateralization can improve ROM regardless of the humeral inclination\u0026nbsp;[8, 18, 19]. In a cadaveric study, Berhouet et al., demonstrated that greater ADD and free-impingement ROM was achieved when using a 42 mm glenosphere than when using a 36mm glenosphere\u0026nbsp;[19]. A higher level of lateralization was theorized to minimize scapular notching. This was recently demonstrated in a multicenter clinical study including 61 female and 41 male patients undergoing RSA and receiving either a medialized or lateralized glenosphere. While the reported scapular notching rate was lower in the lateralized group, the incidence of SSFF was similar between groups\u0026nbsp;[20].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOur study demonstrated that humeral lateralization together with 145\u0026deg; inclination had the greatest impact on impingement-free passive ROM compared to the classic Grammont-design. Comparison of ROM achieved by inlay versus onlay designs revealed superior results in ADD, EXT, and ER angles for both genders with the use of onlay systems. The use of inlay systems improved IRO, but this improvement was only significant for men. Our results supports Werthel\u0026rsquo;s theoretical findings that more than double of lateralization can be achieved on the humeral side compared with the glenoid side[17]. However, we found that ABD was significantly lower when increasing humeral lateralization, probably due to the lateralization of the greater tuberosity and abutment at the acromion which in vivo may be compensated by scapulothoracic movement, which is not present in our simulating system.\u003c/p\u003e\n\u003cp\u003eContrary to lateralization, which clearly increased with the use of onlay systems, no significant changes in distalization were observed with the use of any type of implant. This may be due to different resection planes of humerus cuts when using inlay or onlay design stems. Moreover, the resection angle is altered with a different NSA as the greater tuberosity is aligned to the humeral metaphysis. This may explain the lack of differences in distalization when using different stem systems. The increase in glenosphere size results in a mean increase of distalization of 1mm regardless of implant configuration..\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe postulate that with the use of implants currently available on the market, and the male patients-based assumption that a higher lateralization improves ROM, women are predisposed to receive an excessive amount of lateralization relative to their joint and body sizes. While the classical 155\u0026deg; Grammont inlay prosthesis led in our study to the medialization of the COR in men, the same design already let to lateralization of COR and the onlay design resulted in a high degree of relative lateralization in female patients. Indeed, we observed that women with a 36mm glenosphere and onlay design obtained over 4% of lateralization more (compared to joint size) than men when using a 42 mm glenosphere and onlay design. These totally disproportionate effects of standard implant sizes on men and women should be targeted by prostheses\u0026rsquo; manufactures, as there should be a greater variety of component sizes on the market to allow for individual risk analysis.\u003c/p\u003e\n\u003cp\u003eLimitations of this study include that the evaluation of implants was restricted to one platform onlay design versus one curved inlay stem design, and that both were from the same manufacturer. Moreover, both stems had different NSA, which has been reported to influence the lateralization achieved on the humeral side[8]. Taken together, our results cannot be extrapolated to other prostheses available in the market, as a more comprehensive and precise comparison needs to be performed to reach conclusion about the optimal implant design for each gender\u0026nbsp;[8, 21, 22]. An additional limitation is that a mixed configuration (i.e. 42mm glenosphere with a 36mm stem) could not be simulated with our software, even if such configuration is often used by surgeons and represents a viable option for some patients. This configuration presents several advantages over the ones above-described, such as greater ADD range with less lateralization.\u0026nbsp;Furthermore, the computational simulation did not enable us to evaluate neither scapulothoracic movement nor soft tissue tensioning with regards to pre-tensioning of the delta muscle or the remaining cuff. Strength of this study is, that those two implant configurations represent the traditional Grammont design (155\u0026deg; inlay design) with one of the most common designs allowing for humeral lateralization.\u003c/p\u003e\n\u003cp\u003eOur study suggests that surgeons should evaluate lateralization individually for each patient by 3D software-based planning and thoroughly assess the trade-off between increased ROM and biomechanical side effects based on patient\u0026rsquo;s constitution, gender, and bone quality.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn reverse shoulder arthroplasty, relative lateralization is much higher in women, especially when using an onlay designs and large glenospheres. Humeral lateralization using new modular onlay systems should be used cautiously especially for small women. Glenoid lateralization can help to reduce impingement by increasing ROM and can therefore be used more effectively for small women. Large glenospheres in combination with lateralizing onlay stems for women bear therefore high risks of developing scapular spine fatigue fractures.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was performed in accordance with the ethical standards of the Charit\u0026eacute; Ethics Committee (Charit\u0026eacute;platz 1, 10117 Berlin, Germany Nr. EA1/016/24), and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all subjects.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors made substantial contributions to the drafting, revision and final approval of the version to be submitted, believe the manuscript represents honest work and give consent for publication.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eProf. Gohlke was consultant for Tornier/Wright/Stryker medical company but without accepting any royalties. There is no conflict of interest regarding the subject of this article. The rest of the authors and none of their family relatives received any royalties or fees from any company.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRole of funding source\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was received for this study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors thank A. Rodrigues-Villalon, PhD for the editing and final preparation of this manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the conception and design of the study, acquisition of data, and analysis and interpretation of data. All authors contributed to the drafting and revision of the manuscript. Specific contributions are as follows: JPI and FG designed and conceptualized the study; JPI and TI analyzed the data; JPI wrote the manuscript; JPI, PA, LE, TI, and FG revised the manuscript; JPI and FG took joint responsibility for the integrity of the work as a whole.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eR. J. Friedman\u003cem\u003e et al.\u003c/em\u003e, \u0026quot;Are Age and Patient Gender Associated With Different Rates and Magnitudes of Clinical Improvement After Reverse Shoulder Arthroplasty?,\u0026quot; (in eng), \u003cem\u003eClin Orthop Relat Res, \u003c/em\u003evol. 476, no. 6, pp. 1264-1273, Jun 2018, doi: 10.1007/s11999.0000000000000270.\u003c/li\u003e\n\u003cli\u003eS. E. 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O\u0026apos;Shea, \u0026quot;Bony increased-offset reversed shoulder arthroplasty: minimizing scapular impingement while maximizing glenoid fixation,\u0026quot; (in eng), \u003cem\u003eClin Orthop Relat Res, \u003c/em\u003evol. 469, no. 9, pp. 2558-67, Sep 2011, doi: 10.1007/s11999-011-1775-4.\u003c/li\u003e\n\u003cli\u003eB. S. Werner, J. Chaoui, and G. Walch, \u0026quot;The influence of humeral neck shaft angle and glenoid lateralization on range of motion in reverse shoulder arthroplasty,\u0026quot; (in eng), \u003cem\u003eJ Shoulder Elbow Surg, \u003c/em\u003evol. 26, no. 10, pp. 1726-1731, Oct 2017, doi: 10.1016/j.jse.2017.03.032.\u003c/li\u003e\n\u003cli\u003eG. 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Shah\u003cem\u003e et al.\u003c/em\u003e, \u0026quot;Influence of implant design and parasagittal acromial morphology on acromial and scapular spine strain after reverse total shoulder arthroplasty: a cadaveric and computer-based biomechanical analysis,\u0026quot; \u003cem\u003eJ Shoulder Elbow Surg, \u003c/em\u003evol. 29, no. 11, pp. 2395-2405, Nov 2020, doi: 10.1016/j.jse.2020.04.004.\u003c/li\u003e\n\u003cli\u003eD. Cuff, D. Pupello, N. Virani, J. Levy, and M. Frankle, \u0026quot;Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency,\u0026quot; (in eng), \u003cem\u003eJ Bone Joint Surg Am, \u003c/em\u003evol. 90, no. 6, pp. 1244-51, Jun 2008, doi: 10.2106/jbjs.G.00775.\u003c/li\u003e\n\u003cli\u003eS. T. Yeazell, J. Inacio, A. Malige, H. Dailey, and G. F. Carolan, \u0026quot;Bone density and its relation to the development of acromial stress fracture following reverse total shoulder arthroplasty,\u0026quot; (in eng), \u003cem\u003eShoulder Elbow, \u003c/em\u003evol. 14, no. 2, pp. 135-141, Apr 2022, doi: 10.1177/1758573220949992.\u003c/li\u003e\n\u003cli\u003eR. J. Otto, N. A. Virani, J. C. Levy, P. T. Nigro, D. J. Cuff, and M. A. Frankle, \u0026quot;Scapular fractures after reverse shoulder arthroplasty: evaluation of risk factors and the reliability of a proposed classification,\u0026quot; (in eng), \u003cem\u003eJ Shoulder Elbow Surg, \u003c/em\u003evol. 22, no. 11, pp. 1514-21, Nov 2013, doi: 10.1016/j.jse.2013.02.007.\u003c/li\u003e\n\u003cli\u003eG. Moineau, C. Levigne, P. Boileau, A. Young, and G. Walch, \u0026quot;Three-dimensional measurement method of arthritic glenoid cavity morphology: feasibility and reproducibility,\u0026quot; (in eng), \u003cem\u003eOrthop Traumatol Surg Res, \u003c/em\u003evol. 98, no. 6 Suppl, pp. S139-45, Oct 2012, doi: 10.1016/j.otsr.2012.06.007.\u003c/li\u003e\n\u003cli\u003eP. Boileau, D. Cheval, M. O. Gauci, N. Holzer, J. Chaoui, and G. Walch, \u0026quot;Automated Three-Dimensional Measurement of Glenoid Version and Inclination in Arthritic Shoulders,\u0026quot; (in eng), \u003cem\u003eJ Bone Joint Surg Am, \u003c/em\u003evol. 100, no. 1, pp. 57-65, Jan 3 2018, doi: 10.2106/jbjs.16.01122.\u003c/li\u003e\n\u003cli\u003eJ. D. Werthel, G. Walch, E. Vegehan, P. Deransart, J. Sanchez-Sotelo, and P. Valenti, \u0026quot;Lateralization in reverse shoulder arthroplasty: a descriptive analysis of different implants in current practice,\u0026quot; (in eng), \u003cem\u003eInt Orthop, \u003c/em\u003evol. 43, no. 10, pp. 2349-2360, Oct 2019, doi: 10.1007/s00264-019-04365-3.\u003c/li\u003e\n\u003cli\u003eE. G. Huish, Jr., G. S. Athwal, L. Neyton, and G. Walch, \u0026quot;Adjusting Implant Size and Position Can Improve Internal Rotation After Reverse Total Shoulder Arthroplasty in a Three-dimensional Computational Model,\u0026quot; (in eng), \u003cem\u003eClin Orthop Relat Res, \u003c/em\u003evol. 479, no. 1, pp. 198-204, Jan 1 2021, doi: 10.1097/corr.0000000000001526.\u003c/li\u003e\n\u003cli\u003eJ. Berhouet, P. Garaud, and L. Favard, \u0026quot;Influence of glenoid component design and humeral component retroversion on internal and external rotation in reverse shoulder arthroplasty: A cadaver study,\u0026quot; \u003cem\u003eOrthopaedics \u0026amp; Traumatology: Surgery \u0026amp; Research, \u003c/em\u003evol. 99, no. 8, pp. 887-894, 2013/12/01/ 2013, doi: https://doi.org/10.1016/j.otsr.2013.08.008.\u003c/li\u003e\n\u003cli\u003eJ. J. King\u003cem\u003e et al.\u003c/em\u003e, \u0026quot;Does isolated glenosphere lateralization affect outcomes in reverse shoulder arthroplasty?,\u0026quot; (in eng), \u003cem\u003eOrthop Traumatol Surg Res, \u003c/em\u003evol. 109, no. 4, p. 103401, Jun 2023, doi: 10.1016/j.otsr.2022.103401.\u003c/li\u003e\n\u003cli\u003eA. L\u0026auml;dermann\u003cem\u003e et al.\u003c/em\u003e, \u0026quot;Effect of humeral stem and glenosphere designs on range of motion and muscle length in reverse shoulder arthroplasty,\u0026quot; (in eng), \u003cem\u003eInt Orthop, \u003c/em\u003evol. 44, no. 3, pp. 519-530, Mar 2020, doi: 10.1007/s00264-019-04463-2.\u003c/li\u003e\n\u003cli\u003eG. D. Langohr, R. Willing, J. B. Medley, G. S. Athwal, and J. A. Johnson, \u0026quot;Contact mechanics of reverse total shoulder arthroplasty during abduction: the effect of neck-shaft angle, humeral cup depth, and glenosphere diameter,\u0026quot; \u003cem\u003eJ Shoulder Elbow Surg, \u003c/em\u003evol. 25, no. 4, pp. 589-97, Apr 2016, doi: 10.1016/j.jse.2015.09.024.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1-4 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"reverse shoulder arthroplasty, lateralization, distalization, onlay, inlay, humeral stem, Gender Medicine","lastPublishedDoi":"10.21203/rs.3.rs-3990719/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3990719/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction:\u003c/strong\u003e In reverse shoulder arthroplasty (RSA) new designs enable greater amounts of lateralization to prevent instability and scapular notching and increase range of motion, however, excessive lateralization leads to stress upon the acromion that can result in scapular spine fatigue fractures (SSFF). Aim of this study was to gender- and size-specifically assess the best implant design selection in order to reduce the risk of SSFF and to optimize lateralization, distalization, and bony impingement-free range of motion (ROM) in patients undergoing RSA.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e Computed tomography scans from 30 osteoarthritic patients (f:15, m:15) and 20 cuff tear arthropathy patients (f:10, m:10) were used to virtually simulate a RSA. The efficacy of inlay vs onlay stems combined with two glenospheres (36mm vs 42mm) in achieving ROM, lateralization, and distalization was evaluated. Moreover, gender and patients constitution were correlated to humeral size by radiologically measuring the best-fit circle of the humeral head.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e A different amount of relative lateralization was achieved in both genders using large glenospheres and onlay designs. Latter yielded a higher ROM in all planes for men and women with a 42 mm glenosphere; with the 36mm glenosphere, an increased ROM was observed only in men. In women, this configuration only improved abduction. When adjusting the absolute amount of lateralization to humerus’ size and regardless of implant type, women received greater relative lateralization than men; with a 42mm glenosphere and an onlay system, women lateralized 19% vs 8.0% observed in men.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e: The relative lateralization achieved using onlay design is much higher in women than men. Humeral lateralization using onlay designs should be used cautiously in women, as they may enhance the risk for developing SSFF. Our results point out that glenoid lateralization should be used instead to reduce inferior notching and to improve ROM, especially in small women.\u003c/p\u003e\n\u003cp\u003eLevel of Evidence: Basic Science Study, Computer Modeling\u003c/p\u003e","manuscriptTitle":"A gender and size specific evaluation of inlay versus onlay stem designs in achieving lateralization and distalization in reverse shoulder arthroplasty","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-13 16:22:11","doi":"10.21203/rs.3.rs-3990719/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-04-15T13:40:15+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-04-08T20:14:36+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"70ccf100-e2a8-4b6b-888f-5956b68cf0b0","date":"2024-03-29T14:50:08+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-03-28T23:22:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"764175a0-2fce-4fa9-a58a-7ac12f856d34","date":"2024-03-27T15:19:53+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-03-15T23:58:18+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-03-15T23:56:54+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-03-09T18:18:04+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-03-09T18:14:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2024-02-26T10:47:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"203b02df-0e38-412c-9e83-3cba52769ed2","owner":[],"postedDate":"March 13th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-09-09T16:19:12+00:00","versionOfRecord":{"articleIdentity":"rs-3990719","link":"https://doi.org/10.1186/s12891-024-07818-y","journal":{"identity":"bmc-musculoskeletal-disorders","isVorOnly":false,"title":"BMC Musculoskeletal Disorders"},"publishedOn":"2024-09-04 16:05:32","publishedOnDateReadable":"September 4th, 2024"},"versionCreatedAt":"2024-03-13 16:22:11","video":"","vorDoi":"10.1186/s12891-024-07818-y","vorDoiUrl":"https://doi.org/10.1186/s12891-024-07818-y","workflowStages":[]},"version":"v1","identity":"rs-3990719","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3990719","identity":"rs-3990719","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}