Institutional rev

*Reprint req

Orthopaedic Sur

44195, USA.

E-mail addre

J Shoulder Elbow Surg (2013) 22, 1530-1536

1058-2746/$ - s

http://dx.doi.org

www.elsevier.com/locate/ymse

Liftoff resistance of augmented glenoid componentsduring cyclic fatigue loading in the posterior-superiordirection

Joseph P. Iannotti, MD, PhDa,*, Kyle E. Lappin, BS, MBAb, Conrad L. Klotz, BS, MBAb,Erik W. Reber, MSb, Steve W. Swopeb

aOrthopaedic and Rheumatologic Institute, Cleveland Clinic, Cleveland, OH, USAbDePuy Orthopaedics, Warsaw, IN, USA

Background and hypothesis: Posterior glenoid bone loss is found in a majority of patients with advancedosteoarthritis of the shoulder. In total shoulder arthroplasty, several methods currently exist for manage-ment of this bone loss, including the use of an augmented glenoid component. Different augmented glenoiddesigns would be expected to vary in their resistance to loosening during mechanical bench-top testing.Our hypothesis is that a stepped augmented glenoid component will have less mechanical liftoff thanaugmented components of varying designs without a step.Materials and methods: Four glenoid prototypes articulated with a humeral head were loaded with a 170-lb compressive load and with 4 mm of posterior-superior translation of the humeral head to 100,000 cycles.Anterior glenoid liftoff was measured.Results: The stepped glenoid component had significantly lower liftoff values (P < .05) compared withseveral other designs at many of the test intervals.Discussion: A stepped design for an augmented glenoid component has superior fixation and less anteriorglenoid liftoff in the presence of eccentric loading and may have better long-term clinical results.Level of evidence: Basic Science Study, Biomechanics, Cadaveric Model.� 2013 Journal of Shoulder and Elbow Surgery Board of Trustees.

Keywords: Augmented glenoid components; mechanical testing; in vitro study; total shoulder arthroplasty;

glenoid bone loss; shoulder osteoarthritis

Total shoulder arthroplasty has shown more predictableoutcomes than hemiarthroplasty and is the preferred sur-gical treatment for most patients with end-stage gleno-humeral arthritis.8,16,19 A range of studies have shown

iew board approval: not applicable.

uests: Joseph P. Iannotti, MD, PhD, Department of

gery, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH

ss: iannotj@ccf.org (J.P. Iannotti).

ee front matter � 2013 Journal of Shoulder and Elbow Surgery

/10.1016/j.jse.2013.01.018

normal glenoid version to vary as much as 20�,5,7,12 whereasthe range of pathologic glenoid retroversion in the presenceof osteoarthritis has been shown to be 60�.14 There are a fewoptions for management of moderate to severe glenoid re-troversion due to posterior glenoid bone loss, and these haveyielded a wide range of clinical results.17,21 This includesasymmetric ‘‘high-side’’ reaming, glenoid bone grafting,reverse total shoulder arthroplasty, posterior cementbuildup, and retroverted positioning of a standard glenoidcomponent. These bone modifications also may be

Board of Trustees.

Figure 1 Five types of augmented glenoid designs tested: (A) spherical asymmetric glenoid, (B) spherical symmetric glenoid, (C) flatangled glenoid, (D) stepped glenoid, and (E) Anchor Peg Glenoid. The red lines represent the orientation of the back-side geometry on theaugmented designs.

Biomechanical evaluation of augmented glenoid designs 1531

associated with posterior capsulorrhaphy to improve hu-meral stability.

Bone grafting can present complications associated withgraft preparation, fixation, and graft incorporation, each ofwhich can result in loss of component fixation.15,16 It wouldbe desirable to have an augmented glenoid component toassist in the correction of glenoid retroversion with theintent of placing the component in a position of optimalversion and to minimize bone removal for correction of thepathologic version. Several types of glenoid augmentationcould be considered. A cemented polyethylene device withasymmetric thickness was implanted from 1995 to 1999and was discontinued because it did not offer enoughclinical improvement to warrant continued use.20 A metal-backed glenoid component was implanted from 1989 to1994 with the goal of enhancing glenoid fixation. The10-year survival rate without revision or radiographicfailure for all patients was estimated at 51.9%.22 Thisimplant is no longer available for clinical use.

We hypothesized that an augmented component havinga surface that articulates with the prepared bone surface tobe perpendicular to the vector of joint loading wouldprovide better in vitro mechanical properties.

Materials and methods

Proposed glenoid designs

Five different glenoid designs, each with a different back-sideconfiguration, were tested: a spherical asymmetric glenoid, a spher-ical symmetric glenoid, a flat angled glenoid, a posterior steppedglenoid, and a traditional non-augmented glenoid (Figs. 1 and 2).Of these 5 designs, 3 (asymmetric, spherical symmetric, and flatangled) were created as prototypes of an augmented glenoid designto replicate the amount of augmentation from a commercially

available glenoid component (stepped) and compared witha commercially available non-augmented component (DePuyOrthopaedics, Warsaw, IN, USA). All components were made frommoderately cross-linked, remelted ultrahigh–molecular weightpolyethylene. The glenoid size and bearing geometry were the sameoval shape with a superior-inferior dimension of 42 mm andanterior-posterior dimension of 31.5 mm. This shape and size ofglenoid matched those of a commercially available 56-mm AnchorPeg Glenoid (DePuy Orthopaedics) with a radius of curvature of thearticulating surface of 31 mm. The humeral head was spherical inshape, with a radius of curvature of 28 mm, resulting in a 3-mmradial mismatch between the components. The large componentsizes selected for in vitro testing represent a greater risk formechanical loosening, as defined in this study, from eccentricloading because of a larger moment arm to the center of thecomponent with superior-posterior edge loading.

The 5 glenoid types tested are shown in Figure 1: a sphericalasymmetric glenoid with 8.6 mm of correction on a spherical backside with a 33-mm radius of curvature, a spherical symmetricglenoid with 7.6 mm of correction on a spherical back side witha 33-mm radius of curvature, a flat angled glenoid with 7.7 mm ofcorrection with a flat back side, a stepped glenoid (Step TechAnchor Peg Glenoid; DePuy Orthopaedics) with an anterior back-side curvature of 33 mm and a conical step with 7.6 mm ofcorrection and a 33-mm radius of curvature on its back side, anda non-augmented glenoid that has a 33-mm back-side radius ofcurvature.

For all designs, the peripheral peg diameter was 4.78 mm andthe central peg diameter was 8.79 mm. Similarly, the Sawbonesblocks (Pacific Research Laboratories, Vashon, WA, USA) had thesame predrilled peripheral hole diameter of 5.18 mm and a pre-drilled central hole diameter of 9.54 mm. The peripheral peglength varied slightly from design to design because the geometryof the back side varied. These peripheral peg lengths ranged from6.9 to 10 mm. The central peg length was made consistent amongall designs with only slight variation, from 12.3 to 12.4 mm. Theslight variation in center peg length is related to the slight varia-tion of posterior augmentation between designs. The consistentdesign parameter was the 13.3� angle of correction that results

Figure 2 Cross sections of 5 glenoid designs: (A) spherical asymmetric glenoid, (B) spherical symmetric glenoid, (C) flat angled glenoid,(D) stepped glenoid, and (E) Anchor Peg Glenoid.

1532 J.P. Iannotti et al.

from the difference in anterior height and posterior height. For thesymmetric, angled, and stepped designs, this 13.3� angle is from theplane of the articular surface of the glenoid to the highest posterioredge of the implant. For the asymmetric design has a 8.6 mmaugmentation whereas the symmetric designs has correction of 7.6to 7.7 mm. The orientation of the angle of correction is shown withthe red lines in Figure 1.

Test design

To measure the resistance to anterior glenoid liftoff, the poste-rior glenoid was eccentrically loaded by translating the humeralhead 4 mm in the posterior-superior direction. This value wasdetermined by distracting the corresponding size of humeralhead until the head is 90% subluxated out of the glenoid cavity,as described by Anglin et al1 and American Society for Testingand Materials standard 2028.2 The posterior-superior directionwas selected because it is the area least supported by peri-pheral pegs and was expected to show the maximum amount ofliftoff.

To simulate both initial and long-term fixation, 2 methods ofcementing the glenoid were used. In the first technique, theperipheral pegs were cemented to simulate initial glenoid fixation.In the second testing method, the peripheral pegs were notcemented whereas the central peg was cemented to simulate long-term fixation in which bone apposition within the flanges of theAnchor Peg Glenoid would provide long-term fixation of theimplant.5,24 Custom-made blocks of 40-lb/ft3 polyurethane foam(Pacific Research Laboratories) were used for placement of theglenoid components. Each block was manufactured to have theperipheral and central holes and a surface matching the compo-nent back-side geometry. This configuration allowed for consistentplacement and seating of the implants with precise back-side andpeg contact. For both configurations, acrylic cement (Fastray self-curing plastics; Bosworth, Skokie, IL, USA) was poured into theappropriate holes. Each hole was carefully filled with cement so

as not to overfill the hole and the cement was not pressurized.The block had an angle of 90� with respect to the axial loadapplied and an angle of 45� in relation to the translation of thehumeral head.

The 4 prosthetic designs were statically loaded to 175 lb ofcompressive force and then cycled at 1 Hz in the posterior-superior direction for 100,000 cycles.1,2 The anterior glenoidliftoff was measured throughout testing (Fig. 3). Components weretested on an MTS 858 Bionix test system (MTS Systems, EdenPrairie, MN, USA). The load was controlled by use of a 562-lbcapacity load cell in load control and displacement withdisplacement control from an auxiliary actuator with a rangeof �10 mm. An MTS LX 500 Laser Extensometer (MTS Systems)was connected to the test frame and used to measure liftoff.The LX 500 has a resolution of 0.001 mm and repeatability of0.003 mm. Reflective tape was placed on the foam block andglenoid, and the laser measured the distance between the edge ofthe 2 pieces of tape.

The liftoff values at 1 and 100,000 cycles were recorded.A standard glenoid, used for the glenoid with minimal or noposterior erosion (Anchor Peg Glenoid) (Figs. 1, E, and 2, E),was also tested in the same configuration for comparison toa commercially available implant with the same type of fixationfeatures. Successful intermediate-term clinical results using thisimplant were recently reported.5,10,24 For statistical analysis, weused a Student t test with a 2-tailed distribution and 2-sampleunequal variance.

Results

The initial and final liftoff values were recorded (Figs. 4-7,Tables I-IV). For the peripheral peg–cemented condition, thestepped glenoid had lower initial and final liftoff values withstatistical significance (P ¼ .001 and P ¼ .018, respectively)when compared with the spherical asymmetric glenoid at all

Figure 4 Results of peripheral peg–cemented condition.

Figure 3 Anterior liftoff caused by posterior compressive loading.

Figure 5 Results of center peg–cemented condition.

Figure 6 Initial liftoff comparison within same design.

Figure 7 Final liftoff comparison within same design.

Biomechanical evaluation of augmented glenoid designs 1533

test intervals (Fig. 4, Table I). For the central peg–cementedcondition, the stepped glenoid had statistically significantlylower liftoff at initial and final measurement when comparedwith the spherical asymmetric design (P ¼ .09 and P ¼ .038,respectively) and the flat angled design (P ¼ .002 and

P ¼ .002, respectively) and a lower liftoff compared with thesymmetric design at initial liftoff (P¼ .035) (Fig. 5, Table II).In the peripheral peg–cemented condition, the initial and finalliftoff values were higher only in the spherical asymmetricdesign (P¼ .002 and P¼ .002, respectively) (Fig. 4, Table I).

Table I Results and statistics for peripheral peg–cemented condition

Group A: sphericalasymmetric

Group B: sphericalsymmetric

Group C: flat angled Group D: Step Tech Group E: APG

Initial (mm) 270 � 23 196 � 126 132 � 50 57 � 26 31 � 7Statistics vs Step Tech A > D, P ¼ .001 B > D, P ¼ .191 C > D, P ¼ .105Statistics vs APG A > E, P ¼ .002 B > E, P ¼ .151 C > E, P ¼ .071 D > E, P ¼ .227Final (mm) 310 � 23 294 � 174 334 � 179 87 � 66 34 � 0Statistics vs Step Tech A > D, P ¼ .018 B > D, P ¼ .164 C > D, P ¼ .127Statistics vs APG A > E, P ¼ .002 B > E, P ¼ .122 C > E, P ¼ .101 D > E, P ¼ .299

APG, Anchor Peg Glenoid.

Table II Results and statistics for center peg–cemented condition

Group A: sphericalasymmetric

Group B: sphericalsymmetric

Group C: flat angled Group D: Step Tech Group E: APG

Initial (mm) 205 � 22 166 � 19 237 � 19 122 � 15 55 � 19Statistics vs Step Tech A > D, P ¼ .009 B > D, P ¼ .035 C > D, P ¼ .002Statistics vs APG A > E, P ¼ .001 B > E, P ¼ .002 C > E, P < .001 D > E, P ¼ .009Final (mm) 220 � 12 192 � 23 342 � 23 129 � 36 72 � 32Statistics vs Step Tech A > D, P ¼ .038 B > D, P ¼ .076 C > D, P ¼ .002Statistics vs APG A > E, P ¼ .008 B > E, P ¼ .008 C > E, P ¼ .001 D > E, P ¼ .113

APG, Anchor Peg Glenoid.

Table III Initial liftoff comparison between cementing methods

Group A: sphericalasymmetric

Group B: sphericalsymmetric

Group C: flat angled Group D: Step Tech Group E: APG

CP PP CP PP CP PP CP PP CP PP

Initial (mm) 205 � 22 270 � 23 166 � 19 196 � 126 237 � 19 132 � 50 122 � 15 57 � 26 55 � 19 31 � 7Statistics CP < PP, P ¼ .025 CP < PP, P ¼ .722 CP > PP, P ¼ .054 CP > PP, P ¼ .029 CP > PP, P ¼ .142

APG, Anchor Peg Glenoid; CP, center peg; PP, peripheral peg.

Table IV Final liftoff comparison between cementing methods

Group A: sphericalasymmetric

Group B: sphericalsymmetric

Group C: flat angled Group D: Step Tech Group E: APG

CP PP CP PP CP PP CP PP CP PP

Final (mm) 220 � 12 310 � 23 192 � 23 294 � 174 342 � 23 334 � 179 129 � 36 87 � 66 72 � 32 34 � 0Statistics CP < PP, P ¼ .010 CP < PP, P ¼ .416 CP > PP, P ¼ .942 CP > PP, P ¼ .394 CP > PP, P ¼ .175

APG, Anchor Peg Glenoid; CP, center peg; PP, peripheral peg.

1534 J.P. Iannotti et al.

In the center peg–cemented condition, all augmented designshad higher initial liftoff compared with the non-augmenteddesign (P < .001 to P ¼ .009) (Fig. 5, Table II). For thecenter peg–cemented condition, all augmented designs hadhigher final liftoff values than the non-augmented design(P¼ .001 to P¼ .008) except the stepped glenoid, which wasnot statistically different (P ¼ .113) (Fig. 5, Tables I and II).

When we compared the initial and final liftoff ofthe same design under different loading conditions, theonly significant difference was in the initial and finalloading of the asymmetric design (P ¼ .025 andP ¼ .010, respectively) and the initial loading of thestepped design (P ¼ .029) (Figs. 6 and 7, Table IIIand IV).

Biomechanical evaluation of augmented glenoid designs 1535

Discussion

Posterior glenoid bone loss and increased retroversionmake placement of a glenoid component more difficult.Norris and Iannotti16 found that patients with moderate orsevere posterior glenoid wear have greater active externalrotation and forward elevation with total shoulder arthro-plasty than those who were treated with hemiarthroplasty.Placement of the glenoid in excessive retroversion leads toeccentric glenoid loading and premature glenoid loos-ening.3,6,10,18 Asymmetric reaming to correct for glenoidretroversion results in medialization of the joint line andcannot be performed with greater than 15� to 20� of cor-rection because of excessive bone removal and peg perfo-ration.11,13,16 In a computational model, Nowak et al17

found that glenoid retroversion of 18� could not be cor-rected with contemporary pegged devices without perfo-rating the glenoid wall. Iannotti et al11 showed in a clinicalcase series that glenoid retroversion of more than 19�

cannot be corrected by high-side reaming without perfo-ration of the glenoid wall. Lazarus and colleagues,13 usinga cadaveric model, showed an inability to correct more than15� of retroversion by high-side reaming. Use of an all-polyethylene augmented glenoid component would bea logical approach to management of moderate to severeglenoid bone loss. To date, no biomechanical data havebeen presented on such devices. A preliminary clinicalstudy of the stepped glenoid component showed its abilityto yield better correction of glenoid retroversion and lessmedialization of the joint line than with the use of a stan-dard non-augmented glenoid component.25 Our studyevaluated the biomechanical fixation of 4 types of all-polyethylene posterior augmented designs.

The peripheral peg–cemented configuration in this studyis intended to simulate the initial fixation of a device thathas a press-fit central peg before growth around the peg hasoccurred. The center peg–cemented configuration is inten-ded to simulate the long-term fixation of a central press-fitpeg.9,23 The Anchor Peg Glenoid is a clinically successfuldevice for resurfacing of the glenoid.9,24 The stepped gle-noid was the only design that did not have a higher liftoffthan the Anchor Peg Glenoid for the central peg–cementedconfiguration at the final liftoff measurement (P ¼ .113)(Table II). A device that is most resistant to liftoff after100,000 cycles with only central peg fixation may be morelikely to maintain long-term fixation.

In a mechanical study of cyclic loading and the resultingglenoid distraction, Budge et al4 found that all-polyethyleneglenoids secured with cement outperformed porous-backeddesigns used with or without cement. When the parametersof their study are compared with those of our study, theonly difference is the magnitude of translation and orien-tation of loading. Budge et al used 1.5 mm for translationin the superior direction, whereas we used 4 mm of trans-lation in the posterior-superior direction. The magnitude of

translation is substantially higher in this study, yet theamount of distraction in their study for an all-polyethylenecomponent was 50% to 400% higher than the distractionof the stepped glenoid.4 This potential difference maybe attributed to the cementing technique for the all-polyethylene glenoid, or it could suggest that the geom-etry of the stepped glenoid could contribute to stability andliftoff resistance.

Further clinical studies are needed to understand thepotential benefits and risks associated with posterior aug-mented glenoids. Other in vitro studies could include varia-tions in simulated bone density and the addition of shouldermuscles and tissues in a cadaveric simulation. In addition,the Sawbones blocks used in this study were prepared tohave an exact geometric match to the associated glenoidcomponent. This back-side conformity represents a best-casescenario for all configurations. Full back-side conformity isnot always achievable in a clinical setting, and variations inback-side support may be beneficial in further studies.Finally, the loading profile may be more appropriate ifmatched to a specific activity of daily living instead ofsimple cyclic translation with internal-external rotation.

Conclusion

This study showed that in vitro glenoid stability is betterin some conditions for a stepped augmented glenoiddevice when compared with a non-stepped augmenteddevice. In addition, the lift-off of the stepped glenoidwas the only augmented device that was not statisticallyhigher than a non-augmented device in the center pegfixation condition.

Disclaimer

Joseph P. Iannotti reports that he has received royaltyand consulting income from DePuy Johnson & Johnson.Drs Lappin, Klotz, Reber, and Swope are employed atDePuy Johnson & Johnson. Funded by DePuy Ortho-paedics, Warsaw, IN, USA.

References

1. Anglin C, Wyss U, Pichora D. Mechanical testing of shoulder

prosthesis and recommendations for glenoid design. J Shoulder

Elbow Surg 2000;9:323-31.

2. ASTM 2028-08. Standard test method for dynamic evaluation of

glenoid loosening or disassociation. West Conshohocken, PA: ASTM

International. American Society for Testing and Materials 2008.

3. Bryce C, Davison A, Okita N, Lewis G, Sharkey N, Armstrong A. A

biomechanical study of posterior bone loss on humeral head

1536 J.P. Iannotti et al.

translation. J Shoulder Elbow Surg 2010;19:994-1002. http://dx.doi.

org/10.1016/j.jse.2010.04.010

4. Budge M, Wiater J, Kurdzei M, Baker K. A biomechanical comparison

of three fixation methods of porous tantalum backed glenoid compo-

nents. Presented at the 2012 American Academy of Orthopaedic

Surgeons Annual Meeting. Paper #329. San Francisco, CA; Feb 8, 2012.

5. Churchill S, Brems J, Kotschi H. Glenoid size, inclination and version: an

anatomic study. J Shoulder Elbow Surg 2001;10:327-32.

6. Farron A, Terrier A, Buchler P. Risk of loosening of a prosthetic

glenoid implanted in retroversion. J Shoulder Elbow Surg 2006;15:

521-6. http://dx.doi.org/10.1016/j.jse.2005.10.003

7. Ganapathi A, McCarron J, Chen X, Iannotti J. Predicting normal

glenoid version from the pathologic scapula: a comparison of 4

methods in 2- and 3-dimensional models. J Shoulder Elbow Surg

2011;20:234-44. http://dx.doi.org/10.1016/j.jse.2010.05.024

8. Gartsman G, Roddey T, Hammerman S. Shoulder arthroplasty with or

without resurfacing of the glenoid in patients who have arthritis.

J Bone Joint Surg Am 2000;82:26-34.

9. Groh G. Survival and radiographic analysis of a glenoid component

with a cementless fluted central peg. J Shoulder Elbow Surg 2010;19:

1265-8. http://dx.doi.org/10.1016/j.jse.2010.03.012

10. Ho J, Sabesan V, Iannotti J. Clinical and radiographic factors associ-

ated with anchor peg glenoid component radiographic center peg

osteolysis. J Bone Joint Surg 2013 [in press].

11. Iannotti J, Greeson C, Downing D, Sabesan V, Bryan J. Effect of glenoid

deformity on glenoid component placement in primary shoulder

arthroplasty. J Shoulder Elbow Surg 2012;21:48-55. http://dx.doi.org/

10.1016/j.jse.2011.02.011

12. KwonY, PowellK,YumJK,Brems J, Iannotti J. Use of three-dimensional

computed topography for the analysis of the glenoid anatomy. J Shoulder

Elbow Surg 2005;14:85-90. http://dx.doi.org/10.1016/j.jse.2004.04.011

13. Gillespie R, Lyons R, Lazarus M. Eccentric reaming in total shoulder

arthroplasty: a cadaveric study. Orthopedics 2009;32:21. http://dx.doi.

org/10.3928/01477447-20090101-07

14. Mullaji A, Beddow F, Lamb G. Ct measurement of glenoid erosion in

arthritis. J Bone Joint Surg Br 1994;76:384-8.

15. Neer C, Morrison D. Glenoid bone grafting in total shoulder arthro-

plasty. J Bone Joint Surg Am 1988;70:1154-62.

16. Norris T, Iannotti J. Functional outcome after shoulder arthroplasty for

primary osteoarthritis: a multicenter study. J Shoulder Elbow Surg

2002;11:130-5. http://dx.doi.org/10.1067/mse.2002.121146

17. Nowak D, Bahu M, Gardner T, Dyrszka M, Levine W, Bigliani L, et al.

Simulation of surgical glenoid resurfacing using three-dimensional

computed tomography of the arthritic glenohumeral joint: the

amount of glenoid retroversion that can be corrected. J Shoulder Elbow

Surg 2009;18:680-8. http://dx.doi.org/10.1016/j.jse.2009.03.019

18. Nyffeler R, Sheikh R, Atkinson T, Jacob H, Favre P, Gerber C. Effects

of glenoid component version on humeral head displacement and joint

reaction forces: an experimental study. J Shoulder Elbow Surg 2006;

15:625-9. http://dx.doi.org/10.1016/j.jse.2005.09.016

19. Orfaly R, Rockwood C, Zeki-Esenyel C, Wirth M. A prospective

functional outcome study of shoulder arthroplasty for osteoarthritis

with an intact rotator cuff. J Shoulder Elbow Surg 2003;12:214-21.

http://dx.doi.org/10.1016/S1058-2746(02)86882-3

20. Rice R, Sperling J, Miletti J, Schleck C, Cofield R. Augmented gle-

noid component for bone deficiency in shoulder arthroplasty. Clin

Orthop Relat Res 2008;466:579-83. http://dx.doi.org/10.1007/s11999-

007-0104-4

21. Rodosky M, Bigliani L. Indications for glenoid resurfacing in shoulder

arthroplasty. J Shoulder Elbow Surg 1996;5:231-48.

22. Taunton M, McIntosh A, Sperling J, Cofield R. Total shoulder

arthroplasty with a metal-backed, bone-ingrowth glenoid component. J

Bone Joint Surg Am 2008;90:2180-8. http://dx.doi.org/10.2106/JBJS.

G.00966

23. Wirth M, Korvick D, Basamania C, Toro F, Aufdemort T,

Rockwood C. Radiologic, mechanical and histologic evaluation of 2

glenoid designs in a canine model. J Shoulder Elbow Surg 2001;10:

140-8.

24. Wirth M, Loredo R, Garcia G, Rockwood C, Southworth C, Iannotti J.

Total shoulder arthroplasty with an all-polyethylene pegged bone-

ingrowth glenoid component. J Bone Joint Surg Am 2012;94:260-7.

http://dx.doi.org/10.2106/JBJS.J.01400

25. Youderian AR, Napolitano LA, Davidson IU, Iannotti JP. Management

of glenoid bone loss with the use of a new augmented all-polyethylene

glenoid component. Tech Shoulder Elbow Surg 2012;13:163-9. http://

dx.doi.org/10.1097/BTE.0b013e318265354d