Effect of reverse shoulder arthroplasty humeral component retroversion on acromial strain.

MedStar author(s):
Citation: Journal of Shoulder & Elbow Surgery. 32(6S):S69-S74, 2023 Jun.PMID: 36828287Institution: MedStar Union Memorial HospitalDepartment: Orthopaedic Surgery | Orthopaedic Surgery Residency | OrthopedicsForm of publication: Journal ArticleMedline article type(s): Journal ArticleSubject headings: *Arthroplasty, Replacement, Shoulder | *Fractures, Stress | *Shoulder Joint | Acromion/su [Surgery] | Arthroplasty, Replacement, Shoulder/ae [Adverse Effects] | Fractures, Stress/et [Etiology] | Humans | Humerus/su [Surgery] | Range of Motion, Articular | Shoulder Joint/su [Surgery] | Year: 2023Local holdings: Available online from MWHC library: 1995 - present, Available in print through MWHC library:2004 - 2007ISSN:
  • 1058-2746
Name of journal: Journal of shoulder and elbow surgeryAbstract: CONCLUSIONS: This biomechanical study found no significant difference in scapular spine and acromion strain after RSA when comparing variations in humeral stem version. There does appear to be lower strain at both the acromion and scapular spine at 60degree of abduction when compared to 0degree of abduction regardless of stem version. Copyright © 2023 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.INTRODUCTION: Acromion and scapular spine stress fractures can be catastrophic complications following reverse shoulder arthroplasty (RSA). A variety of host, implant, and technical factors have been identified that increase the risk of this complication. The glenoid component in particular has been closely evaluated for its impact on rates of stress fractures following RSA. The goal of this biomechanical study is to evaluate if humeral stem version has an impact on acromion and scapular spine strain after RSA.METHODS: Eight cadaveric specimens were tested on a custom dynamic shoulder frame. Commercially available RSA components were implanted with the humeral component inserted in 0degree of retroversion. Acromion and scapular spine strain were measured at 0degree, 30degree, and 60degree of abduction using strain rosettes secured to the acromion and scapular spine in the typical locations for Levy type II and type III stress fractures, respectively. The humeral stem was then removed and reimplanted in 30degree of retroversion and the measurements were repeated. Student t test was performed to analyze the relationship between humeral stem version and acromion and scapular spine strain at various abduction angles.RESULTS: Strain at the both the acromion and scapular spine were found to have no significant difference at any abduction angle when comparing 0degree and 30degree version of the humeral stem. With 0degree and 30degree versions pooled together, there is significantly lower acromion and scapular spine strain at 60degree of abduction when compared to 0degree of abduction (strain at 0degree abduction - strain at 60degree abduction: acromion 313.1 mu ; P = .0409, Scapular spine 304.9 mu ; P = .0407). There was no significant difference in strain at either location when comparing 0degree of abduction to 30degree of abduction and when comparing 30degree of abduction to 60degree of abduction.All authors: Abbasi P, Austin L, Gillin T, Haislup B, Murthi AM, O'Leary M, Wright MFiscal year: FY2023Digital Object Identifier: Date added to catalog: 06/01/2023
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Journal Article MedStar Authors Catalog Article 36828287 Available 36828287

Available online from MWHC library: 1995 - present, Available in print through MWHC library:2004 - 2007

CONCLUSIONS: This biomechanical study found no significant difference in scapular spine and acromion strain after RSA when comparing variations in humeral stem version. There does appear to be lower strain at both the acromion and scapular spine at 60degree of abduction when compared to 0degree of abduction regardless of stem version. Copyright © 2023 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

INTRODUCTION: Acromion and scapular spine stress fractures can be catastrophic complications following reverse shoulder arthroplasty (RSA). A variety of host, implant, and technical factors have been identified that increase the risk of this complication. The glenoid component in particular has been closely evaluated for its impact on rates of stress fractures following RSA. The goal of this biomechanical study is to evaluate if humeral stem version has an impact on acromion and scapular spine strain after RSA.

METHODS: Eight cadaveric specimens were tested on a custom dynamic shoulder frame. Commercially available RSA components were implanted with the humeral component inserted in 0degree of retroversion. Acromion and scapular spine strain were measured at 0degree, 30degree, and 60degree of abduction using strain rosettes secured to the acromion and scapular spine in the typical locations for Levy type II and type III stress fractures, respectively. The humeral stem was then removed and reimplanted in 30degree of retroversion and the measurements were repeated. Student t test was performed to analyze the relationship between humeral stem version and acromion and scapular spine strain at various abduction angles.

RESULTS: Strain at the both the acromion and scapular spine were found to have no significant difference at any abduction angle when comparing 0degree and 30degree version of the humeral stem. With 0degree and 30degree versions pooled together, there is significantly lower acromion and scapular spine strain at 60degree of abduction when compared to 0degree of abduction (strain at 0degree abduction - strain at 60degree abduction: acromion 313.1 mu ; P = .0409, Scapular spine 304.9 mu ; P = .0407). There was no significant difference in strain at either location when comparing 0degree of abduction to 30degree of abduction and when comparing 30degree of abduction to 60degree of abduction.

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