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Journal of Shoulder and Elbow Surgery

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

      Background

      The purpose was to analyze the influence of deltoid lengthening due to different implant designs and anatomic variations of the acromion and scapular spine (SS) in the parasagittal plane on strain patterns after reverse shoulder arthroplasty (RSA).

      Methods

      Ten cadaveric shoulders with strain rosettes placed on the surface of the acromial body (Levy II) and SS (Levy III) were tested using a shoulder simulator. RSA using humeral onlay (+3, +5, +8, +10, +13 mm) and glenosphere lateralization (0, +6 mm) was performed. Arm lengthening and magnitude of strain on acromion/SS were measured. The length of deltoid was assessed using validated computer modeling. Anatomic variance of the SS angle and position of acromion in relation to the scapular plane was examined. For comparison of strain as a function of deltoid lengthening, 25 mm was used as a threshold value for comparison based on previous literature demonstrating a decrease in Constant score and active anterior elevation in patients with arm lengthening >25 mm.

      Results

      At maximal deltoid lengthening (30.8 mm), average strains were 1112 με (acromion) and 1165 με (SS) (P < .01). There was an 82.6% increase in acromial strain at maximum lengthening compared with 25 mm (P = .02) and a strain increase of 79 με/mm deltoid lengthening above a threshold of 25 mm. The strain results delineated 2 anatomic groups: 5 of 10 specimens (group A) showed higher strain on SS (1445 με) vs. acromion (862 με, P = .02). Group A had a more posteriorly oriented acromion, whereas group B was anteriorly oriented (P < .001).

      Conclusion

      Deltoid lengthening above 25 mm produced large strains on the acromion/SS. Anatomic variation may indicate that as the acromion is more posteriorly oriented, the SS takes more strain from the deltoid vs. the acromion. Our study's data may help surgeons identify a high-risk population for increased strain patterns after RSA.

      Level of evidence

      Keywords

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      References

        • Ackland D.C.
        • Roshan-Zamir S.
        • Richardson M.
        • Pandy M.G.
        Moment arms of the shoulder musculature after reverse total shoulder arthroplasty.
        J Bone Joint Surg Am. 2010; 92: 1221-1230https://doi.org/10.2106/JBJS.I.00001
        • Ascione F.
        • Kilian C.M.
        • Laughlin M.S.
        • Bugelli G.
        • Domos P.
        • Neyton L.
        • et al.
        Increased scapular spine fractures after reverse shoulder arthroplasty with a humeral onlay short stem: an analysis of 485 consecutive cases.
        J Shoulder Elbow Surg. 2018; 27: 2183-2190https://doi.org/10.1016/j.jse.2018.06.007
        • Bayraktar H.H.
        • Morgan E.F.
        • Niebur G.L.
        • Morris G.E.
        • Wong E.K.
        • Keaveny T.M.
        Comparison of the elastic and yield properties of human femoral trabecular and cortical bone tissue.
        J Biomech. 2004; 37: 27-35https://doi.org/10.1016/s0021-9290(03)00257-4
        • Charlton I.W.
        • Johnson G.R.
        A model for the prediction of the forces at the glenohumeral joint.
        Proc Inst Mech Eng H. 2006; 220: 801-812https://doi.org/10.1243/09544119JEIM147
        • Crosby L.A.
        • Hamilton A.
        • Twiss T.
        Scapula fractures after reverse total shoulder arthroplasty: classification and treatment.
        Clin Orthop Relat Res. 2011; 469: 2544-2549https://doi.org/10.1007/s11999-011-1881-3
        • Dubrow S.
        • Streit J.J.
        • Muh S.
        • Shishani Y.
        • Gobezie R.
        Acromial stress fractures: correlation with acromioclavicular osteoarthritis and acromiohumeral distance.
        Orthopedics. 2014; 37: e1074-e1079https://doi.org/10.3928/01477447-20141124-54
        • Farshad M.
        • Gerber C.
        Reverse total shoulder arthroplasty-from the most to the least common complication.
        Int Orthop. 2010; 34: 1075-1082https://doi.org/10.1007/s00264-010-1125-2
        • Garner B.A.
        • Pandy M.G.
        The obstacle-set method for representing muscle paths in musculoskeletal models.
        Comput Methods Biomech Biomed Engin. 2000; 3: 1-30
        • Garner B.A.
        • Pandy M.G.
        Musculoskeletal model of the upper limb based on the visible human male dataset.
        Comput Methods Biomech Biomed Engin. 2001; 4: 93-126
        • Giles J.W.
        • Langohr G.D.
        • Johnson J.A.
        • Athwal G.S.
        Implant design variations in reverse total shoulder arthroplasty influence the required deltoid force and resultant joint load.
        Clin Orthop Relat Res. 2015; 473: 3615-3626https://doi.org/10.1007/s11999-015-4526-0
        • Henninger H.B.
        • Barg A.
        • Anderson A.E.
        • Bachus K.N.
        • Burks R.T.
        • Tashjian R.Z.
        Effect of lateral offset center of rotation in reverse total shoulder arthroplasty: a biomechanical study.
        J Shoulder Elbow Surg. 2012; 21: 1128-1135https://doi.org/10.1016/j.jse.2011.07.034
        • Jobin C.M.
        • Brown G.D.
        • Bahu M.J.
        • Gardner T.R.
        • Bigliani L.U.
        • Levine W.N.
        • et al.
        Reverse total shoulder arthroplasty for cuff tear arthropathy: the clinical effect of deltoid lengthening and center of rotation medialization.
        J Shoulder Elbow Surg. 2012; 21: 1269-1277https://doi.org/10.1016/j.jse.2011.08.049
        • Levy J.C.
        • Anderson C.
        • Samson A.
        Classification of postoperative acromial fractures following reverse shoulder arthroplasty.
        J Bone Joint Surg Am. 2013; 95: e104https://doi.org/10.2106/JBJS.K.01516
        • Lädermann A.
        • Edwards T.B.
        • Walch G.
        Arm lengthening after reverse shoulder arthroplasty: a review.
        Int Orthop. 2014; 38: 991-1000https://doi.org/10.1007/s00264-013-2175-z
        • Mayne I.P.
        • Bell S.N.
        • Wright W.
        • Coghlan J.A.
        Acromial and scapular spine fractures after reverse total shoulder arthroplasty.
        Shoulder Elbow. 2016; 8: 90-100https://doi.org/10.1177/1758573216628783
        • Neyton L.
        • Erickson J.
        • Ascione F.
        • Bugelli G.
        • Lunini E.
        • Walch G.
        Grammont Award 2018: Scapular fractures in reverse shoulder arthroplasty (Grammont style): prevalence, functional, and radiographic results with minimum 5-year follow-up.
        J Shoulder Elbow Surg. 2019; 28: 260-267https://doi.org/10.1016/j.jse.2018.07.004
        • Otto R.J.
        • Virani N.A.
        • Levy J.C.
        • Nigro P.T.
        • Cuff D.J.
        • Frankle M.A.
        Scapular fractures after reverse shoulder arthroplasty: evaluation of risk factors and the reliability of a proposed classification.
        J Shoulder Elbow Surg. 2013; 22: 1514-1521https://doi.org/10.1016/j.jse.2013.02.007
        • Patterson D.C.
        • Chi D.
        • Parsons B.O.
        • Cagle P.J.
        Acromial spine fracture after reverse total shoulder arthroplasty: a systematic review.
        J Shoulder Elbow Surg. 2019; 28: 792-801https://doi.org/10.1016/j.jse.2018.08.033
        • Pattin C.A.
        • Caler W.E.
        • Carter D.R.
        Cyclic mechanical property degradation during fatigue loading of cortical bone.
        J Biomech. 1996; 29: 69-79
        • Routman H.D.
        • Flurin P.H.
        • Wright T.W.
        • Zuckerman J.D.
        • Hamilton M.A.
        • Roche C.P.
        Reverse shoulder arthroplasty prosthesis design classification system.
        Bull Hosp Jt Dis (2013). 2015; 73: S5-S14
        • Schaffler M.B.
        • Radin E.L.
        • Burr D.B.
        Mechanical and morphological effects of strain rate on fatigue of compact bone.
        Bone. 1989; 10: 207-214
        • Schaffler M.B.
        • Radin E.L.
        • Burr D.B.
        Long-term fatigue behavior of compact bone at low strain magnitude and rate.
        Bone. 1990; 11: 321-326
        • Schenk P.
        • Aichmair A.
        • Beeler S.
        • Ernstbrunner L.
        • Meyer D.C.
        • Gerber C.
        Acromial fractures following reverse total shoulder arthroplasty: a cohort controlled analysis.
        Orthopedics. 2020; 43: 15-22https://doi.org/10.3928/01477447-20191031-03
        • Teusink M.J.
        • Otto R.J.
        • Cottrell B.J.
        • Frankle M.A.
        What is the effect of postoperative scapular fracture on outcomes of reverse shoulder arthroplasty?.
        J Shoulder Elbow Surg. 2014; 23: 782-790https://doi.org/10.1016/j.jse.2013.09.010
        • Walch G.
        • Mottier F.
        • Wall B.
        • Boileau P.
        • Molé D.
        • Favard L.
        Acromial insufficiency in reverse shoulder arthroplasties.
        J Shoulder Elbow Surg. 2009; 18: 495-502https://doi.org/10.1016/j.jse.2008.12.002
        • Werner B.C.
        • Chen X.
        • Camp C.L.
        • Kontaxis A.
        • Dines J.S.
        • Gulotta L.V.
        Medial posterior capsular plication reduces anterior shoulder instability similar to remplissage without restricting motion in the setting of an engaging Hill-Sachs defect.
        Am J Sports Med. 2017; 45: 1982-1989https://doi.org/10.1177/0363546517700860
        • Werner B.S.
        • Ascione F.
        • Bugelli G.
        • Walch G.
        Does arm lengthening affect the functional outcome in onlay reverse shoulder arthroplasty?.
        J Shoulder Elbow Surg. 2017; 26: 2152-2157https://doi.org/10.1016/j.jse.2017.05.021
        • Werthel J.-D.
        • Schoch B.S.
        • van Veen S.C.
        • Elhassan B.T.
        • An K.-N.
        • Cofield R.H.
        • et al.
        Acromial fractures in reverse shoulder arthroplasty: a clinical and radiographic analysis.
        J Shoulder Elbow Arthroplasty. 2018; 2 (2471549218777628. https://doi.org/10.1177/2471549218777628)
        • Wong M.T.
        • Langohr G.D.G.
        • Athwal G.S.
        • Johnson J.A.
        Implant positioning in reverse shoulder arthroplasty has an impact on acromial stresses.
        J Shoulder Elbow Surg. 2016; 25: 1889-1895https://doi.org/10.1016/j.jse.2016.04.011