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T HE J OURNAL
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S URGERY, I NCORPORATED
A Comparison of Concentric and Eccentric Glenospheres in Reverse Shoulder Arthroplasty A Randomized Controlled Trial Peter C. Poon, MBChB, FRACS, Justin Chou, MBChB, Simon W. Young, MBChB, FRACS, and Tim Astley, MBChB, FRACS Investigation performed at the Department of Orthopaedic Surgery, North Shore Hospital, North Shore City, New Zealand
Background: Inferior scapular notching following reverse shoulder arthroplasty is due to mechanical impingement and, in some studies, has been associated with poorer functional scores, lower patient satisfaction, and more limited shoulder motion. We aimed to test the hypothesis that inferior positioning of the center of rotation with eccentric glenosphere designs decreases the adduction deficit before impingement occurs and improves clinical outcome. Methods: A randomized, controlled, double-blinded trial was performed. According to the results of a power analysis, fifty patients undergoing reverse shoulder arthroplasty for the diagnosis of cuff tear arthropathy were randomized intraoperatively to receive either a concentric or eccentric glenosphere. The glenoid baseplate was positioned flush to the inferior border of the glenoid before the glenosphere was then attached. Notching was assessed using an anteroposterior radiograph, and clinical outcome was assessed using the visual analog pain scale score, shoulder function rating, American Shoulder and Elbow Surgeons score, and Oxford shoulder score. Active forward elevation and external rotation were assessed. The outcome assessor was blinded to the treatment group. The mean follow-up period for the groups was forty-three and forty-seven months. Results: Patient demographics and preoperative scores were similar between the groups. At the time of the final followup, four patients (14.8%) in the concentric group had developed inferior scapular notching (two with Nerot grade I and two with Nerot grade II), ranging in size from 1.1 to 7.4 mm, compared with one patient (4.3%; Nerot grade I) in the eccentric group (p = 0.36). No notching occurred in any patient with glenoid overhang of >3.5 mm. No significant difference between the groups was seen with respect to functional outcome scores, patient satisfaction, or shoulder motion. Conclusions: There were no differences in notching rates or clinical outcomes between concentric and eccentric glenospheres following reverse shoulder arthroplasty. Inferior glenosphere overhang of >3.5 mm, however, prevented notching. This may be achieved with a modified surgical technique, but eccentric glenospheres provide an additional option. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
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nferior scapular notching is a recognized complication following reverse shoulder arthroplasty, with rates reported to range from 0% to 96%1-24 (see Appendix). Notching occurs because of mechanical impingement between the humeral component and the lateral scapular pillar, causing osteolysis through either direct mechanical contact or as a biological response to wear debris3.
The influence of scapular notching on outcome is unclear. While some studies have found no difference in clinical outcome7,15, others have noted that scapular notching is associated with poorer functional outcomes, lower patient satisfaction, and more limited shoulder motion2,6,10. Additionally, notching progresses with time8,11 and is associated with the development of
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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but a clinical reduction in notching rates has yet to be demonstrated13. The aim of the present study was therefore to assess whether the use of an eccentric glenosphere would lead to a reduction in notching rates and improved clinical outcomes. Materials and Methods Study Design
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Fig. 1
Patient enrollment according to the inclusion and exclusion criteria.
periprosthetic radiolucent lines10, causing concern that notching may eventually lead to glenoid component loosening. A number of strategies aiming to minimize impingement and subsequent notching have been proposed. Placing the glenoid baseplate flush with the inferior border of the glenoid, to allow inferior overhang of the glenosphere, has been shown in biomechanical studies25,26 to maximize the amount of adduction before humeral prosthesis-scapular impingement occurs. Simovitch et al. confirmed in a clinical series6 that inferior positioning of the glenosphere was correlated with reduced scapular notching, and this strategy has been widely adopted. Inferior positioning of the glenosphere is, however, limited by the degree to which the surgeon can position the baseplate on the glenoid without compromising osseous fixation. This has led to the development of eccentric glenospheres, which allow the surgeon to achieve further inferior overhang of the glenosphere. Biomechanical studies26,27 have suggested that eccentric glenospheres permit increased adduction before impingement occurs,
e conducted a single-center, randomized controlled trial in which consecutive patients undergoing primary reverse shoulder arthroplasty were randomized to one of two groups (Fig. 1). Patients in Group A received a standard SMR 36-mm concentric glenosphere (Shoulder Modular Replacement; Lima Corporate, San Daniele del Friuli, Italy), and patients in Group B had an SMR 36-mm eccentric glenosphere (Fig. 2). The glenoid baseplate has a superior to inferior length of 28 mm. Fixation is by one superior and one inferior 6.5-mm variable angle screw. The glenosphere is attached to the center of the baseplate by a double-ended Morse taper and a central screw. The concentric 36-mm glenosphere is a 180° hemisphere and has the Morse taper attachment in its center. The 36-mm eccentric glenosphere has a Morse taper attachment that is 4 mm superior to its center and thereby the center of rotation is positioned 4 mm inferiorly (Fig. 3). It has three different sections (Fig. 3). The superior part is less than a hemisphere. The middle part is a true hemisphere (18 mm thick). The inferior part is more than a hemisphere. The eccentric position of the glenosphere allows continuation of the inferior aspect of the glenosphere to a position slightly medial to the baseplate. This extension or ‘‘hook’’ has no influence on the center of rotation and does not have any additional effect on the position of the humeral articulation. The glenoid baseplate has a curved back design and this lateralizes the center of rotation of the glenosphere approximately 4 mm from the most medial point of the glenoid bone-baseplate interface. However, the degree of lateralization of the center of rotation of the glenosphere is the same for both 27 the concentric and eccentric design . The humeral inclination angle of this prosthesis is 150°. The clinical trial was approved by and registered with the New Zealand Northern X Ethics Committee (NTX/07/05/045). Patients were enrolled from August 2007 to January 2011. Randomization involved the use of computer-generated, sequentially numbered, and sealed opaque envelopes. Written informed consent was obtained from the patients during consultation for surgery. Patients were blinded to the type of glenosphere and were informed that the type to be used had been randomly allocated in a concealed envelope. The surgeon was blinded to the type of glenosphere until after implantation of the glenoid baseplate. The circulating nurse would then open the concealed envelope to reveal the type of glenosphere to be provided to the operating surgeon. Sample size calculation was based on a power analysis using data on the rate of scapular notching from a previously published study from the same
Fig. 2
The prosthesis-scapular neck angle (Fig. 2-A) and the scapular neck to inferior glenosphere rim distance (Fig. 2-B).
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deficient glenoid bone stock and an abnormal deltoid muscle. Demographic data recorded for each participant included age, sex, side, and arm dominance.
Treatment
Fig. 3
Concentric (Fig. 3-A) versus eccentric (Fig. 3-B) glenosphere designs. The eccentric glenosphere has an additional 4 mm of inferior positioning achieved by an off-center attachment in the glenosphere. (Reproduced with permission from Springer Science1Business Media: De Biase CF, Ziveri G, Delcogliano M, de Caro F, Gumina S, Borroni M, Castagana A, Postacchini R. The use of an eccentric glenosphere compared with a concentric glenosphere in reverse total shoulder arthroplasty: two-year minimum follow-up results. Int Orthop. 2013 Oct;37(10):1949-55. Epub 2013 Jun 9.) 17
surgical center and using the same implant , which showed a notching rate of 28% (twelve of forty-three patients) with a concentric glenosphere versus 0% (zero of six patients) with an eccentric glenosphere. For an alpha level of 0.05 and power of 80%, it was calculated that a minimum of twenty-three patients in each arm would be required to detect a significant difference in notching rates.
Eligibility and Exclusion Criteria Patients over the age of sixty-five years who were referred to the tertiary orthopaedic surgical center with clinical and radiographic evidence of cuff tear arthropathy were considered for inclusion in the study. Exclusion criteria were
All patients were initially assessed by two experienced orthopaedic upper limb 28 specialists at our tertiary referral center. Grashey anteroposterior and axillary lateral radiographs of the affected shoulder were made and digitized on a computerized image viewer system (WEB1000; Agfa). The preoperative ra29 diographs were graded on the basis of the Hamada grading system . Additionally, the morphology of the scapular neck was also assessed with digital 6 measurement of the scapular neck angle . All reverse shoulder arthroplasties were performed by two experienced upper limb shoulder specialists. The surgical approaches were standardized with the patient in the beach-chair position. The deltopectoral approach was used with subscapularis tenotomy. The surgeon attempted to position the glenoid baseplate flush at the most inferior border of the glenoid fossae for patients in both the eccentric and concentric groups. The glenoid was reamed in neutral or a slight inferior inclination. The humeral prosthesis was positioned between 0° and 20° of retroversion. Postoperatively, all patients underwent a standardized physiotherapy rehabilitation program. For the first six weeks, the patients wore a sling and were allowed passive range-of-motion exercises only. Between six and twelve weeks after surgery, active range-of-motion exercise began, supervised by physiotherapists. Three months after surgery, gradual strengthening exercises were encouraged. Grashey anteroposterior and axillary lateral radiographs were made at three, six, twelve, and eighteen months after surgery and then yearly thereafter. Radiographs were reviewed at the time they were made by one of the two senior shoulder surgeons as part of a general follow-up evaluation. Radiographs that were suboptimal were replaced with repeat radiographs.
Outcome Measures The primary outcome measure was the rate of scapular notching, defined as disruption of cortical continuity at the contact point between the inferior scapular neck and the rim of the humeral cup on an anteroposterior shoulder radiograph. We measured the size of the notch in millimeters and also used the 1 Nerot grading system . Radiographs were independently measured by two trained assessors (J.C. and S.W.Y.) who were not blinded because of the distinctive radiographic appearances of the glenospheres (Fig. 4). Secondary outcomes were assessed by an independent research nurse blinded to the treatment groups. These included patient-based visual analog
Fig. 4
Scapular notching (arrows) in a patient with a concentric glenosphere (Fig. 4-A) and in a patient with an eccentric glenosphere (Fig. 4-B).
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inferior glenosphere rim was an additional assessment of inferior positioning and 18 degree of inferior glenosphere overhang (see Appendix) .
TABLE I Demographic Data on the Patients
Demographic Age*(yr)
Concentric Group (n = 27)
Eccentric Group (n = 23)
81 (65-91)
81 (67-91)
Sex (M:F)
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8:19
7:16
Dominant arm affected (no. [%] of patients)
11 (41)
16 (70)
Duration of follow-up* (mo)
43 (24-60)
47 (24-72)
Data Analysis All categorical data were analyzed using the chi-square test and continuous data were analyzed using the Mann-Whitney U test. In all cases, a p value of 3.5 mm developed notching in either group. All five patients who had an inferior glenosphere overhang of £3.5 mm developed scapular notching (Table IV). There were three complications. One patient in the concentric group developed instability following a fall; she had a revision to a 44-mm glenosphere and exchange of the humeral insert. One patient in the concentric group and one patient in the eccentric group developed an acromial stress fracture. Both healed with nonoperative treatment, but the range of motion remained impaired, accounting for the poorest forward elevation in each study group. Discussion number of strategies have been proposed to avoid inferior impingement and scapular notching following reverse shoulder arthroplasty. These include placement of the baseplate flush with the inferior border of the glenoid25 or inferior tilt14 of the glenoid baseplate, inverted bearing surfaces30, and increased lateral offset through either glenoid bone-grafting12 or a lateralized glenosphere design19. Nyffeler et al.25 demonstrated in a cadaver model that inferior overhang of the glenosphere beyond the glenoid rim allowed maximum adduction before impingement occurred. In that study, placing the glenosphere between 2 and 4 mm distally improved adduction by 11° and 24°, respectively. Similarly, Middernacht et al.31 demonstrated that a 36-mm concentric glenosphere with a 2-mm overhang from the osseous glenoid rim increases the adduction angle by 13°. In another study, de Wilde et al.26 used a computer model to assess six different strategies to prevent notching, including lateralizing the
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center of rotation and larger glenosphere sizes, and concluded that inferior glenosphere overhang was the most effective. The amount of inferior glenosphere overhang that can be achieved is limited by the degree to which the glenoid baseplate can be placed in a more inferior position without compromising fixation. This led to the development of eccentric glenospheres, which can further increase inferior overhang. Chou et al. demonstrated in a biomechanical study that, compared with a concentric design, a 4-mm eccentric glenosphere improved adduction by 14.5° before impingement occurred27. The eccentric glenosphere had a trend toward a lower rate of notching, but our study failed to show a significant difference in notching rates between the concentric (14.8%) and eccentric (4.3%) groups. However, the notching rate seen in the concentric group was lower than anticipated from our past experience17, and considerably lower than that reported in previous series1-24 (see Appendix). The lower notching rate may be due to improvements in surgical technique, since placing the glenoid baseplate flush with the inferior border of the glenoid is now a routine surgical technique and reduces notching rates with whichever type of glenosphere is used. The mean inferior overhang in the concentric group was 5.5 mm, which is greater than that recommended by biomechanical studies to prevent notching25,26,31. No patient in either group with >3.5 mm of overhang developed notching. Eccentric glenospheres may be a useful addition to the surgeons’ armamentarium to achieve such inferior glenoid overhang in an individual patient, particularly if high placement of the glenoid baseplate was either mistakenly done or deliberately done to optimize other factors such as osseous coverage or screw placement. However, if the baseplate is placed too high, notching can occur even with an eccentric glenosphere (as occurred in one patient). Two previous studies have described the clinical use of eccentric glenospheres13,18. De Biase et al.18 retrospectively reviewed the cases of twenty-five patients who underwent reverse shoulder arthroplasty with a 4-mm eccentric 36-mm glenosphere, the same prosthesis used in the present study. The glenoid baseplate was positioned next to the inferior glenoid rim. No inferior scapular notching was seen at an average follow-up of twenty-eight months. Mizuno et al.13 reported on forty-seven patients managed with an eccentric reverse shoulder arthroplasty design, which provides an
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additional 2 mm of inferior offset. The notching rate at a mean follow-up of thirty months was 40%, with 95% of those nineteen patients having Nerot grade-I or II notching. The authors concluded that the eccentric design did not prevent notching but reduced the severity. The eccentric design used in our study differed from that in the study by Mizuno et al. by the degree of eccentricity (4 mm versus 2 mm) and the presence of the small inferior hook (Fig. 3). As this hook represents the medial continuation of the normal glenosphere curve, it is unlikely to alter humeral motion and therefore it is unclear what effect it may have on scapular notching. Aside from the degree of eccentricity, the prosthesis used by Mizuno et al. has other design differences, including the humeral inclination of 155°. Other prosthetic modifications have also been successful in reducing notching rates. Frankle et al. reported no scapular notching in sixty patients who had received the reverse shoulder prosthesis19, which included a built-in offset in the glenosphere that lateralizes the center of rotation. This strategy has also been used to varying degrees in other reverse shoulder arthroplasty designs23,24. It may also be a factor in the prosthesis used in this study, as the curved baseplate design lateralizes the glenosphere center of rotation approximately 4 mm from the most medial point of the glenoid bone-baseplate interface27, in both concentric and eccentric designs. However, in contrast to eccentric glenospheres, the lateralization in the reverse shoulder prosthesis places the center of rotation substantially more lateral to the prosthetic-bone interface, which can potentially increase stresses and compromise fixation. Harman et al.32 showed this design resulted in a 44% to 69% greater moment at the bonemetal back interface, and a failure rate of 12% was reported at the time of the thirty-three-month follow-up19. Improved fixation with larger screws appeared to alleviate this problem, with Cuff et al.22 reporting no baseplate failures and a 9% notching rate in ninety-four patients with a minimum follow-up of five years with the modified prosthetic design. Poon et al. investigated the effect of eccentric glenospheres on micromotion at the baseplate-bone interface using a biomechanical model33. Eccentric glenospheres increased micromotion in comparison with concentric designs of the same size. However, the increase in micromotion was small, and the maximum baseplate micromotion (22.2 mm) was well within the accepted limit for osseous ingrowth into uncemented prostheses (150 mm). This finding contrasts with that in the study of a lateralized prosthesis by Harman et al.32, which showed micromotion values of >100 mm, even with the use of 5-mm screws. In the only previous prospective trial investigating strategies to reduce notching, Edwards et al.14 randomized forty-two patients to a standard reverse shoulder arthroplasty technique or implantation with a 10° inferior tilt of the glenoid component, using the Aequalis prosthesis. Notching occurred in fifteen (75%) of twenty patients in the inferior tilt group and in nineteen (86%) of twenty-two patients in the control group (p = 0.5). The authors concluded that inferior tilt of the glenoid component does not decrease scapular notching. The higher notching rates seen in that study may be related to implant factors, as there is significant variation in reported notching rates between different prostheses (see Appendix). Of note, Gutie´ rrez et al. found in a computer model that inferior tilt combined with
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an eccentric glenosphere resulted in uneven force distribution across the baseplate and is therefore not recommended in contrast to concentric or lateralized designs34. Patients doubled their range of forward elevation from preoperative to postoperative evaluations (Table II). During the present study, it was our practice intraoperatively to make the reverse prosthesis articulation ‘‘tight,’’ which may be a reason why the final forward elevation in our patients was lower than that reported by others7,13,22. In our early experience, prior to this study, we had some patients who had postoperative dislocations that required revision to a thicker humeral polyethylene. Postoperative dislocation has since become an uncommon complication. We have also become more confident in our intraoperative assessment of impingement, soft-tissue tension, and stability of the reverse prosthesis. There are a number of limitations to our study. First, follow-up was relatively short and the long-term effects of eccentric glenospheres on baseplate fixation are unknown. While other reports have suggested that most patients who develop notching will do so within two years postoperatively6,10, notching rates and severity can continue to increase even after this period10,22. As the mean follow-up period was similar between the groups in the present study, the comparison of notching remains valid, but we were unable to report the long-term clinical effects. Second, as discussed above, the low notching rate seen in the concentric group suggests that with this prosthesis, routine use of eccentric glenospheres may be of limited additional benefit. However, these data may be specific to this prosthesis and may not apply to other reverse shoulder arthroplasty designs with higher reported notching rates (see Appendix). Finally, we did not evaluate anterior or posterior notching, which has been described previously6, partly because making standardized radiographs to assess notching is difficult. The clinical relevance of scapular notching remains controversial, with some authors reporting no impact on postoperative function3,7,8. In contrast, Sirveaux et al.2 found that patients with more extensive notching (grades III and IV) had lower postoperative Constant scores. Simovitch et al.6 reported that patients with notching had lower mean Constant scores, a lower subjective shoulder score, inferior shoulder strength, and worse postoperative range of motion, with a 17° decrease in active forward elevation and a 16° decrease in abduction. In the present study, no difference in clinical outcome was seen between patients with or without notching; however, both the size of the notches and the number of patients with notching were small. In conclusion, we found no significant differences in notching rates or clinical outcomes between concentric and eccentric glenospheres following reverse shoulder arthroplasty with this prosthetic design. Inferior glenosphere overhang appears relevant, however, as notching did not occur in any patient with an overhang of >3.5 mm. Eccentric glenospheres appear to be a viable option if required to achieve such overhang in an individual patient. Appendix A figure demonstrating the concentric and eccentric glenosphere designs and a table showing the published notching rates for reverse shoulder arthroplasty are available
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with the online version of this article as a data supplement at jbjs.org. n
Peter C. Poon, MBChB, FRACS Justin Chou, MBChB
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Simon W. Young, MBChB, FRACS Tim Astley, MBChB, FRACS Department of Orthopaedic Surgery, North Shore Hospital, Private Bag 93 503, Takapuna, North Shore City 0740, New Zealand. E-mail address for P.C. Poon: [email protected]
References 1. Valenti PH, Boutens D, Nerot C. Delta 3 reversed prosthesis for osteoarthritis with massive rotator cuff tear: long-term results (> 5 years). In: Walch G, Boileau P, Mole D, editors. Shoulder prosthesis: two to ten year follow-up. Montpellier, France: Sauramps Medical; 2001. p 253–9. 2. Sirveaux F, Favard L, Oudet D, Huquet D, Walch G, Mol´e D. Grammont inverted total shoulder arthroplasty in the treatment of glenohumeral osteoarthritis with massive rupture of the cuff. Results of a multicentre study of 80 shoulders. J Bone Joint Surg Br. 2004 Apr;86(3):388-95. 3. Werner CM, Steinmann PA, Gilbart M, Gerber C. Treatment of painful pseudoparesis due to irreparable rotator cuff dysfunction with the Delta III reverse-ball-andsocket total shoulder prosthesis. J Bone Joint Surg Am. 2005 Jul;87(7):1476-86. 4. Seebauer L. Reverse prosthesis through a superior approach for cuff tear arthropathy. Tech Shoulder Elbow Surg. 2006;7(1):13. 5. Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg. 2005 Jan-Feb; 14(1)(Suppl S):147S-61S. 6. Simovitch RW, Zumstein MA, Lohri E, Helmy N, Gerber C. Predictors of scapular notching in patients managed with the Delta III reverse total shoulder replacement. J Bone Joint Surg Am. 2007 Mar;89(3):588-600. 7. Wall B, Nov´e-Josserand L, O’Connor DP, Edwards TB, Walch G. Reverse total shoulder arthroplasty: a review of results according to etiology. J Bone Joint Surg Am. 2007 Jul;89(7):1476-85. 8. L´evigne C, Boileau P, Favard L, Garaud P, Mol´e D, Sirveaux F, Walch G. Scapular notching in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2008 NovDec;17(6):925-35. Epub 2008 Jun 16. 9. Wierks C, Skolasky RL, Ji JH, McFarland EG. Reverse total shoulder replacement: intraoperative and early postoperative complications. Clin Orthop Relat Res. 2009 Jan;467(1):225-34. Epub 2008 Aug 7. 10. L´evigne C, Garret J, Boileau P, Alami G, Favard L, Walch G. Scapular notching in reverse shoulder arthroplasty: is it important to avoid it and how? Clin Orthop Relat Res. 2011 Sep;469(9):2512-20. 11. Favard L, Levigne C, Nerot C, Gerber C, De Wilde L, Mole D. Reverse prostheses in arthropathies with cuff tear: are survivorship and function maintained over time? Clin Orthop Relat Res. 2011 Sep;469(9):2469-75. 12. Boileau P, Moineau G, Roussanne Y, O’Shea K. Bony increased-offset reversed shoulder arthroplasty: minimizing scapular impingement while maximizing glenoid fixation. Clin Orthop Relat Res. 2011 Sep;469(9):2558-67. 13. Mizuno N, Denard PJ, Raiss P, Walch G. The clinical and radiographical results of reverse total shoulder arthroplasty with eccentric glenosphere. Int Orthop. 2012 Aug;36(8):1647-53. Epub 2012 Apr 26. 14. Edwards TB, Trappey GJ, Riley C, O’Connor DP, Elkousy HA, Gartsman GM. Inferior tilt of the glenoid component does not decrease scapular notching in reverse shoulder arthroplasty: results of a prospective randomized study. J Shoulder Elbow Surg. 2012 May;21(5):641-6. Epub 2011 Nov 12. 15. Walch G, Bacle G, L¨adermann A, Nov´e-Josserand L, Smithers CJ. Do the indications, results, and complications of reverse shoulder arthroplasty change with surgeon’s experience? J Shoulder Elbow Surg. 2012 Nov;21(11):1470-7. Epub 2012 Feb 22. 16. Bufquin T, Hersan A, Hubert L, Massin P. Reverse shoulder arthroplasty for the treatment of three- and four-part fractures of the proximal humerus in the elderly: a prospective review of 43 cases with a short-term follow-up. J Bone Joint Surg Br. 2007 Apr;89(4):516-20. 17. Young SW, Everts NM, Ball CM, Astley TM, Poon PC. The SMR reverse shoulder prosthesis in the treatment of cuff-deficient shoulder conditions. J Shoulder Elbow Surg. 2009 Jul-Aug;18(4):622-6. Epub 2009 Apr 11.
18. De Biase CF, Delcogliano M, Borroni M, Castagna A. Reverse total shoulder arthroplasty: radiological and clinical result using an eccentric glenosphere. Musculoskelet Surg. 2012 May;96(Suppl 1):S27-34. Epub 2012 Apr 20. 19. Frankle M, Siegal S, Pupello D, Saleem A, Mighell M, Vasey M. The Reverse Shoulder Prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency. A minimum two-year follow-up study of sixty patients. J Bone Joint Surg Am. 2005 Aug;87(8):1697-705. 20. Cuff D, Pupello D, Virani N, Levy J, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency. J Bone Joint Surg Am. 2008 Jun;90(6): 1244-51. 21. Mulieri P, Dunning P, Klein S, Pupello D, Frankle M. Reverse shoulder arthroplasty for the treatment of irreparable rotator cuff tear without glenohumeral arthritis. J Bone Joint Surg Am. 2010 Nov 3;92(15):2544-56. 22. Cuff D, Clark R, Pupello D, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency: a concise follow-up, at a minimum of five years, of a previous report. J Bone Joint Surg Am. 2012 Nov 7;94(21):1996-2000. 23. Roche CP, Marczuk Y, Wright TW, Flurin PH, Grey S, Jones R, Routman HD, Gilot G, Zuckerman JD. Scapular notching and osteophyte formation after reverse shoulder replacement: Radiological analysis of implant position in male and female patients. Bone Joint J. 2013 Apr;95-B(4):530-5. 24. Valenti P, Sauzi`eres P, Katz D, Kalouche I, Kilinc AS. Do less medialized reverse shoulder prostheses increase motion and reduce notching? Clin Orthop Relat Res. 2011 Sep;469(9):2550-7. 25. Nyffeler RW, Werner CM, Gerber C. Biomechanical relevance of glenoid component positioning in the reverse Delta III total shoulder prosthesis. J Shoulder Elbow Surg. 2005 Sep-Oct;14(5):524-8. 26. de Wilde LF, Poncet D, Middernacht B, Ekelund A. Prosthetic overhang is the most effective way to prevent scapular conflict in a reverse total shoulder prosthesis. Acta Orthop.2010 Dec;81(6):719-26. 27. Chou J, Malak SF, Anderson IA, Astley T, Poon PC. Biomechanical evaluation of different designs of glenospheres in the SMR reverse total shoulder prosthesis: range of motion and risk of scapular notching. J Shoulder Elbow Surg. 2009 MayJun;18(3):354-9. 28. Lee JHE, Van Raalte V, Malian V. Diagnosis of SLAP lesions with Grasheyview arthrography. Skeletal Radiol. 2003 Jul;32(7):388-95. Epub 2003 May 21. 29. Hamada K, Yamanaka K, Uchiyama Y, Mikasa T, Mikasa M. A radiographic classification of massive rotator cuff tear arthritis. Clin Orthop Relat Res. 2011 Sep;469(9):2452-60. 30. Kohut G, Dallmann F, Irlenbusch U. Wear-induced loss of mass in reversed total shoulder arthroplasty with conventional and inverted bearing materials. J Biomech. 2012 Feb 2;45(3):469-73. Epub 2011 Dec 27. 31. Middernacht B, De Roo PJ, Van Maele G, De Wilde LF. Consequences of scapular anatomy for reversed total shoulder arthroplasty. Clin Orthop Relat Res. 2008 Jun;466(6):1410-8. Epub 2008 Mar 6. 32. Harman M, Frankle M, Vasey M, Banks S. Initial glenoid component fixation in ‘‘reverse’’ total shoulder arthroplasty: a biomechanical evaluation. J Shoulder Elbow Surg. 2005 Jan-Feb;14(1)(Suppl S):162S-7S. 33. Poon PC, Chou J, Young D, Malak SF, Anderson IA. Biomechanical evaluation of different designs of glenospheres in the SMR reverse shoulder prosthesis: micromotion of the baseplate and risk of loosening. Shoulder & Elbow. 2010;2(2):94-9. 34. Guti´errez S, Walker M, Willis M, Pupello DR, Frankle MA. Effects of tilt and glenosphere eccentricity on baseplate/bone interface forces in a computational model, validated by a mechanical model, of reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2011 Jul;20(5):732-9. Epub 2011 Feb 2.
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BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
A Comparison of Concentric and Eccentric Glenospheres in Reverse Shoulder Arthroplasty A Randomized Controlled Trial Peter C. Poon, MBChB, FRACS, Justin Chou, MBChB, Simon W. Young, MBChB, FRACS, and Tim Astley, MBChB, FRACS Investigation performed at the Department of Orthopaedic Surgery, North Shore Hospital, North Shore City, New Zealand
Background: Inferior scapular notching following reverse shoulder arthroplasty is due to mechanical impingement and, in some studies, has been associated with poorer functional scores, lower patient satisfaction, and more limited shoulder motion. We aimed to test the hypothesis that inferior positioning of the center of rotation with eccentric glenosphere designs decreases the adduction deficit before impingement occurs and improves clinical outcome. Methods: A randomized, controlled, double-blinded trial was performed. According to the results of a power analysis, fifty patients undergoing reverse shoulder arthroplasty for the diagnosis of cuff tear arthropathy were randomized intraoperatively to receive either a concentric or eccentric glenosphere. The glenoid baseplate was positioned flush to the inferior border of the glenoid before the glenosphere was then attached. Notching was assessed using an anteroposterior radiograph, and clinical outcome was assessed using the visual analog pain scale score, shoulder function rating, American Shoulder and Elbow Surgeons score, and Oxford shoulder score. Active forward elevation and external rotation were assessed. The outcome assessor was blinded to the treatment group. The mean follow-up period for the groups was forty-three and forty-seven months. Results: Patient demographics and preoperative scores were similar between the groups. At the time of the final followup, four patients (14.8%) in the concentric group had developed inferior scapular notching (two with Nerot grade I and two with Nerot grade II), ranging in size from 1.1 to 7.4 mm, compared with one patient (4.3%; Nerot grade I) in the eccentric group (p = 0.36). No notching occurred in any patient with glenoid overhang of >3.5 mm. No significant difference between the groups was seen with respect to functional outcome scores, patient satisfaction, or shoulder motion. Conclusions: There were no differences in notching rates or clinical outcomes between concentric and eccentric glenospheres following reverse shoulder arthroplasty. Inferior glenosphere overhang of >3.5 mm, however, prevented notching. This may be achieved with a modified surgical technique, but eccentric glenospheres provide an additional option. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
I
nferior scapular notching is a recognized complication following reverse shoulder arthroplasty, with rates reported to range from 0% to 96%1-24 (see Appendix). Notching occurs because of mechanical impingement between the humeral component and the lateral scapular pillar, causing osteolysis through either direct mechanical contact or as a biological response to wear debris3.
The influence of scapular notching on outcome is unclear. While some studies have found no difference in clinical outcome7,15, others have noted that scapular notching is associated with poorer functional outcomes, lower patient satisfaction, and more limited shoulder motion2,6,10. Additionally, notching progresses with time8,11 and is associated with the development of
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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but a clinical reduction in notching rates has yet to be demonstrated13. The aim of the present study was therefore to assess whether the use of an eccentric glenosphere would lead to a reduction in notching rates and improved clinical outcomes. Materials and Methods Study Design
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Fig. 1
Patient enrollment according to the inclusion and exclusion criteria.
periprosthetic radiolucent lines10, causing concern that notching may eventually lead to glenoid component loosening. A number of strategies aiming to minimize impingement and subsequent notching have been proposed. Placing the glenoid baseplate flush with the inferior border of the glenoid, to allow inferior overhang of the glenosphere, has been shown in biomechanical studies25,26 to maximize the amount of adduction before humeral prosthesis-scapular impingement occurs. Simovitch et al. confirmed in a clinical series6 that inferior positioning of the glenosphere was correlated with reduced scapular notching, and this strategy has been widely adopted. Inferior positioning of the glenosphere is, however, limited by the degree to which the surgeon can position the baseplate on the glenoid without compromising osseous fixation. This has led to the development of eccentric glenospheres, which allow the surgeon to achieve further inferior overhang of the glenosphere. Biomechanical studies26,27 have suggested that eccentric glenospheres permit increased adduction before impingement occurs,
e conducted a single-center, randomized controlled trial in which consecutive patients undergoing primary reverse shoulder arthroplasty were randomized to one of two groups (Fig. 1). Patients in Group A received a standard SMR 36-mm concentric glenosphere (Shoulder Modular Replacement; Lima Corporate, San Daniele del Friuli, Italy), and patients in Group B had an SMR 36-mm eccentric glenosphere (Fig. 2). The glenoid baseplate has a superior to inferior length of 28 mm. Fixation is by one superior and one inferior 6.5-mm variable angle screw. The glenosphere is attached to the center of the baseplate by a double-ended Morse taper and a central screw. The concentric 36-mm glenosphere is a 180° hemisphere and has the Morse taper attachment in its center. The 36-mm eccentric glenosphere has a Morse taper attachment that is 4 mm superior to its center and thereby the center of rotation is positioned 4 mm inferiorly (Fig. 3). It has three different sections (Fig. 3). The superior part is less than a hemisphere. The middle part is a true hemisphere (18 mm thick). The inferior part is more than a hemisphere. The eccentric position of the glenosphere allows continuation of the inferior aspect of the glenosphere to a position slightly medial to the baseplate. This extension or ‘‘hook’’ has no influence on the center of rotation and does not have any additional effect on the position of the humeral articulation. The glenoid baseplate has a curved back design and this lateralizes the center of rotation of the glenosphere approximately 4 mm from the most medial point of the glenoid bone-baseplate interface. However, the degree of lateralization of the center of rotation of the glenosphere is the same for both 27 the concentric and eccentric design . The humeral inclination angle of this prosthesis is 150°. The clinical trial was approved by and registered with the New Zealand Northern X Ethics Committee (NTX/07/05/045). Patients were enrolled from August 2007 to January 2011. Randomization involved the use of computer-generated, sequentially numbered, and sealed opaque envelopes. Written informed consent was obtained from the patients during consultation for surgery. Patients were blinded to the type of glenosphere and were informed that the type to be used had been randomly allocated in a concealed envelope. The surgeon was blinded to the type of glenosphere until after implantation of the glenoid baseplate. The circulating nurse would then open the concealed envelope to reveal the type of glenosphere to be provided to the operating surgeon. Sample size calculation was based on a power analysis using data on the rate of scapular notching from a previously published study from the same
Fig. 2
The prosthesis-scapular neck angle (Fig. 2-A) and the scapular neck to inferior glenosphere rim distance (Fig. 2-B).
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deficient glenoid bone stock and an abnormal deltoid muscle. Demographic data recorded for each participant included age, sex, side, and arm dominance.
Treatment
Fig. 3
Concentric (Fig. 3-A) versus eccentric (Fig. 3-B) glenosphere designs. The eccentric glenosphere has an additional 4 mm of inferior positioning achieved by an off-center attachment in the glenosphere. (Reproduced with permission from Springer Science1Business Media: De Biase CF, Ziveri G, Delcogliano M, de Caro F, Gumina S, Borroni M, Castagana A, Postacchini R. The use of an eccentric glenosphere compared with a concentric glenosphere in reverse total shoulder arthroplasty: two-year minimum follow-up results. Int Orthop. 2013 Oct;37(10):1949-55. Epub 2013 Jun 9.) 17
surgical center and using the same implant , which showed a notching rate of 28% (twelve of forty-three patients) with a concentric glenosphere versus 0% (zero of six patients) with an eccentric glenosphere. For an alpha level of 0.05 and power of 80%, it was calculated that a minimum of twenty-three patients in each arm would be required to detect a significant difference in notching rates.
Eligibility and Exclusion Criteria Patients over the age of sixty-five years who were referred to the tertiary orthopaedic surgical center with clinical and radiographic evidence of cuff tear arthropathy were considered for inclusion in the study. Exclusion criteria were
All patients were initially assessed by two experienced orthopaedic upper limb 28 specialists at our tertiary referral center. Grashey anteroposterior and axillary lateral radiographs of the affected shoulder were made and digitized on a computerized image viewer system (WEB1000; Agfa). The preoperative ra29 diographs were graded on the basis of the Hamada grading system . Additionally, the morphology of the scapular neck was also assessed with digital 6 measurement of the scapular neck angle . All reverse shoulder arthroplasties were performed by two experienced upper limb shoulder specialists. The surgical approaches were standardized with the patient in the beach-chair position. The deltopectoral approach was used with subscapularis tenotomy. The surgeon attempted to position the glenoid baseplate flush at the most inferior border of the glenoid fossae for patients in both the eccentric and concentric groups. The glenoid was reamed in neutral or a slight inferior inclination. The humeral prosthesis was positioned between 0° and 20° of retroversion. Postoperatively, all patients underwent a standardized physiotherapy rehabilitation program. For the first six weeks, the patients wore a sling and were allowed passive range-of-motion exercises only. Between six and twelve weeks after surgery, active range-of-motion exercise began, supervised by physiotherapists. Three months after surgery, gradual strengthening exercises were encouraged. Grashey anteroposterior and axillary lateral radiographs were made at three, six, twelve, and eighteen months after surgery and then yearly thereafter. Radiographs were reviewed at the time they were made by one of the two senior shoulder surgeons as part of a general follow-up evaluation. Radiographs that were suboptimal were replaced with repeat radiographs.
Outcome Measures The primary outcome measure was the rate of scapular notching, defined as disruption of cortical continuity at the contact point between the inferior scapular neck and the rim of the humeral cup on an anteroposterior shoulder radiograph. We measured the size of the notch in millimeters and also used the 1 Nerot grading system . Radiographs were independently measured by two trained assessors (J.C. and S.W.Y.) who were not blinded because of the distinctive radiographic appearances of the glenospheres (Fig. 4). Secondary outcomes were assessed by an independent research nurse blinded to the treatment groups. These included patient-based visual analog
Fig. 4
Scapular notching (arrows) in a patient with a concentric glenosphere (Fig. 4-A) and in a patient with an eccentric glenosphere (Fig. 4-B).
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inferior glenosphere rim was an additional assessment of inferior positioning and 18 degree of inferior glenosphere overhang (see Appendix) .
TABLE I Demographic Data on the Patients
Demographic Age*(yr)
Concentric Group (n = 27)
Eccentric Group (n = 23)
81 (65-91)
81 (67-91)
Sex (M:F)
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8:19
7:16
Dominant arm affected (no. [%] of patients)
11 (41)
16 (70)
Duration of follow-up* (mo)
43 (24-60)
47 (24-72)
Data Analysis All categorical data were analyzed using the chi-square test and continuous data were analyzed using the Mann-Whitney U test. In all cases, a p value of 3.5 mm developed notching in either group. All five patients who had an inferior glenosphere overhang of £3.5 mm developed scapular notching (Table IV). There were three complications. One patient in the concentric group developed instability following a fall; she had a revision to a 44-mm glenosphere and exchange of the humeral insert. One patient in the concentric group and one patient in the eccentric group developed an acromial stress fracture. Both healed with nonoperative treatment, but the range of motion remained impaired, accounting for the poorest forward elevation in each study group. Discussion number of strategies have been proposed to avoid inferior impingement and scapular notching following reverse shoulder arthroplasty. These include placement of the baseplate flush with the inferior border of the glenoid25 or inferior tilt14 of the glenoid baseplate, inverted bearing surfaces30, and increased lateral offset through either glenoid bone-grafting12 or a lateralized glenosphere design19. Nyffeler et al.25 demonstrated in a cadaver model that inferior overhang of the glenosphere beyond the glenoid rim allowed maximum adduction before impingement occurred. In that study, placing the glenosphere between 2 and 4 mm distally improved adduction by 11° and 24°, respectively. Similarly, Middernacht et al.31 demonstrated that a 36-mm concentric glenosphere with a 2-mm overhang from the osseous glenoid rim increases the adduction angle by 13°. In another study, de Wilde et al.26 used a computer model to assess six different strategies to prevent notching, including lateralizing the
A
center of rotation and larger glenosphere sizes, and concluded that inferior glenosphere overhang was the most effective. The amount of inferior glenosphere overhang that can be achieved is limited by the degree to which the glenoid baseplate can be placed in a more inferior position without compromising fixation. This led to the development of eccentric glenospheres, which can further increase inferior overhang. Chou et al. demonstrated in a biomechanical study that, compared with a concentric design, a 4-mm eccentric glenosphere improved adduction by 14.5° before impingement occurred27. The eccentric glenosphere had a trend toward a lower rate of notching, but our study failed to show a significant difference in notching rates between the concentric (14.8%) and eccentric (4.3%) groups. However, the notching rate seen in the concentric group was lower than anticipated from our past experience17, and considerably lower than that reported in previous series1-24 (see Appendix). The lower notching rate may be due to improvements in surgical technique, since placing the glenoid baseplate flush with the inferior border of the glenoid is now a routine surgical technique and reduces notching rates with whichever type of glenosphere is used. The mean inferior overhang in the concentric group was 5.5 mm, which is greater than that recommended by biomechanical studies to prevent notching25,26,31. No patient in either group with >3.5 mm of overhang developed notching. Eccentric glenospheres may be a useful addition to the surgeons’ armamentarium to achieve such inferior glenoid overhang in an individual patient, particularly if high placement of the glenoid baseplate was either mistakenly done or deliberately done to optimize other factors such as osseous coverage or screw placement. However, if the baseplate is placed too high, notching can occur even with an eccentric glenosphere (as occurred in one patient). Two previous studies have described the clinical use of eccentric glenospheres13,18. De Biase et al.18 retrospectively reviewed the cases of twenty-five patients who underwent reverse shoulder arthroplasty with a 4-mm eccentric 36-mm glenosphere, the same prosthesis used in the present study. The glenoid baseplate was positioned next to the inferior glenoid rim. No inferior scapular notching was seen at an average follow-up of twenty-eight months. Mizuno et al.13 reported on forty-seven patients managed with an eccentric reverse shoulder arthroplasty design, which provides an
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additional 2 mm of inferior offset. The notching rate at a mean follow-up of thirty months was 40%, with 95% of those nineteen patients having Nerot grade-I or II notching. The authors concluded that the eccentric design did not prevent notching but reduced the severity. The eccentric design used in our study differed from that in the study by Mizuno et al. by the degree of eccentricity (4 mm versus 2 mm) and the presence of the small inferior hook (Fig. 3). As this hook represents the medial continuation of the normal glenosphere curve, it is unlikely to alter humeral motion and therefore it is unclear what effect it may have on scapular notching. Aside from the degree of eccentricity, the prosthesis used by Mizuno et al. has other design differences, including the humeral inclination of 155°. Other prosthetic modifications have also been successful in reducing notching rates. Frankle et al. reported no scapular notching in sixty patients who had received the reverse shoulder prosthesis19, which included a built-in offset in the glenosphere that lateralizes the center of rotation. This strategy has also been used to varying degrees in other reverse shoulder arthroplasty designs23,24. It may also be a factor in the prosthesis used in this study, as the curved baseplate design lateralizes the glenosphere center of rotation approximately 4 mm from the most medial point of the glenoid bone-baseplate interface27, in both concentric and eccentric designs. However, in contrast to eccentric glenospheres, the lateralization in the reverse shoulder prosthesis places the center of rotation substantially more lateral to the prosthetic-bone interface, which can potentially increase stresses and compromise fixation. Harman et al.32 showed this design resulted in a 44% to 69% greater moment at the bonemetal back interface, and a failure rate of 12% was reported at the time of the thirty-three-month follow-up19. Improved fixation with larger screws appeared to alleviate this problem, with Cuff et al.22 reporting no baseplate failures and a 9% notching rate in ninety-four patients with a minimum follow-up of five years with the modified prosthetic design. Poon et al. investigated the effect of eccentric glenospheres on micromotion at the baseplate-bone interface using a biomechanical model33. Eccentric glenospheres increased micromotion in comparison with concentric designs of the same size. However, the increase in micromotion was small, and the maximum baseplate micromotion (22.2 mm) was well within the accepted limit for osseous ingrowth into uncemented prostheses (150 mm). This finding contrasts with that in the study of a lateralized prosthesis by Harman et al.32, which showed micromotion values of >100 mm, even with the use of 5-mm screws. In the only previous prospective trial investigating strategies to reduce notching, Edwards et al.14 randomized forty-two patients to a standard reverse shoulder arthroplasty technique or implantation with a 10° inferior tilt of the glenoid component, using the Aequalis prosthesis. Notching occurred in fifteen (75%) of twenty patients in the inferior tilt group and in nineteen (86%) of twenty-two patients in the control group (p = 0.5). The authors concluded that inferior tilt of the glenoid component does not decrease scapular notching. The higher notching rates seen in that study may be related to implant factors, as there is significant variation in reported notching rates between different prostheses (see Appendix). Of note, Gutie´ rrez et al. found in a computer model that inferior tilt combined with
A C O M PA R I S O N O F C O N C E N T R I C A N D E C C E N T R I C G L E N O S P H E R E S IN REVERSE SHOULDER ARTHROPLASTY
an eccentric glenosphere resulted in uneven force distribution across the baseplate and is therefore not recommended in contrast to concentric or lateralized designs34. Patients doubled their range of forward elevation from preoperative to postoperative evaluations (Table II). During the present study, it was our practice intraoperatively to make the reverse prosthesis articulation ‘‘tight,’’ which may be a reason why the final forward elevation in our patients was lower than that reported by others7,13,22. In our early experience, prior to this study, we had some patients who had postoperative dislocations that required revision to a thicker humeral polyethylene. Postoperative dislocation has since become an uncommon complication. We have also become more confident in our intraoperative assessment of impingement, soft-tissue tension, and stability of the reverse prosthesis. There are a number of limitations to our study. First, follow-up was relatively short and the long-term effects of eccentric glenospheres on baseplate fixation are unknown. While other reports have suggested that most patients who develop notching will do so within two years postoperatively6,10, notching rates and severity can continue to increase even after this period10,22. As the mean follow-up period was similar between the groups in the present study, the comparison of notching remains valid, but we were unable to report the long-term clinical effects. Second, as discussed above, the low notching rate seen in the concentric group suggests that with this prosthesis, routine use of eccentric glenospheres may be of limited additional benefit. However, these data may be specific to this prosthesis and may not apply to other reverse shoulder arthroplasty designs with higher reported notching rates (see Appendix). Finally, we did not evaluate anterior or posterior notching, which has been described previously6, partly because making standardized radiographs to assess notching is difficult. The clinical relevance of scapular notching remains controversial, with some authors reporting no impact on postoperative function3,7,8. In contrast, Sirveaux et al.2 found that patients with more extensive notching (grades III and IV) had lower postoperative Constant scores. Simovitch et al.6 reported that patients with notching had lower mean Constant scores, a lower subjective shoulder score, inferior shoulder strength, and worse postoperative range of motion, with a 17° decrease in active forward elevation and a 16° decrease in abduction. In the present study, no difference in clinical outcome was seen between patients with or without notching; however, both the size of the notches and the number of patients with notching were small. In conclusion, we found no significant differences in notching rates or clinical outcomes between concentric and eccentric glenospheres following reverse shoulder arthroplasty with this prosthetic design. Inferior glenosphere overhang appears relevant, however, as notching did not occur in any patient with an overhang of >3.5 mm. Eccentric glenospheres appear to be a viable option if required to achieve such overhang in an individual patient. Appendix A figure demonstrating the concentric and eccentric glenosphere designs and a table showing the published notching rates for reverse shoulder arthroplasty are available
e138(7) TH E JO U R NA L O F B O N E & JO I N T SU RG E RY J B J S . O RG V O L U M E 9 6-A N U M B E R 16 A U G U S T 20, 2 014 d
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Peter C. Poon, MBChB, FRACS Justin Chou, MBChB
A C O M PA R I S O N O F C O N C E N T R I C A N D E C C E N T R I C G L E N O S P H E R E S IN REVERSE SHOULDER ARTHROPLASTY
Simon W. Young, MBChB, FRACS Tim Astley, MBChB, FRACS Department of Orthopaedic Surgery, North Shore Hospital, Private Bag 93 503, Takapuna, North Shore City 0740, New Zealand. E-mail address for P.C. Poon: [email protected]
References 1. Valenti PH, Boutens D, Nerot C. Delta 3 reversed prosthesis for osteoarthritis with massive rotator cuff tear: long-term results (> 5 years). In: Walch G, Boileau P, Mole D, editors. Shoulder prosthesis: two to ten year follow-up. Montpellier, France: Sauramps Medical; 2001. p 253–9. 2. Sirveaux F, Favard L, Oudet D, Huquet D, Walch G, Mol´e D. Grammont inverted total shoulder arthroplasty in the treatment of glenohumeral osteoarthritis with massive rupture of the cuff. Results of a multicentre study of 80 shoulders. J Bone Joint Surg Br. 2004 Apr;86(3):388-95. 3. Werner CM, Steinmann PA, Gilbart M, Gerber C. Treatment of painful pseudoparesis due to irreparable rotator cuff dysfunction with the Delta III reverse-ball-andsocket total shoulder prosthesis. J Bone Joint Surg Am. 2005 Jul;87(7):1476-86. 4. Seebauer L. Reverse prosthesis through a superior approach for cuff tear arthropathy. Tech Shoulder Elbow Surg. 2006;7(1):13. 5. Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg. 2005 Jan-Feb; 14(1)(Suppl S):147S-61S. 6. Simovitch RW, Zumstein MA, Lohri E, Helmy N, Gerber C. Predictors of scapular notching in patients managed with the Delta III reverse total shoulder replacement. J Bone Joint Surg Am. 2007 Mar;89(3):588-600. 7. Wall B, Nov´e-Josserand L, O’Connor DP, Edwards TB, Walch G. Reverse total shoulder arthroplasty: a review of results according to etiology. J Bone Joint Surg Am. 2007 Jul;89(7):1476-85. 8. L´evigne C, Boileau P, Favard L, Garaud P, Mol´e D, Sirveaux F, Walch G. Scapular notching in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2008 NovDec;17(6):925-35. Epub 2008 Jun 16. 9. Wierks C, Skolasky RL, Ji JH, McFarland EG. Reverse total shoulder replacement: intraoperative and early postoperative complications. Clin Orthop Relat Res. 2009 Jan;467(1):225-34. Epub 2008 Aug 7. 10. L´evigne C, Garret J, Boileau P, Alami G, Favard L, Walch G. Scapular notching in reverse shoulder arthroplasty: is it important to avoid it and how? Clin Orthop Relat Res. 2011 Sep;469(9):2512-20. 11. Favard L, Levigne C, Nerot C, Gerber C, De Wilde L, Mole D. Reverse prostheses in arthropathies with cuff tear: are survivorship and function maintained over time? Clin Orthop Relat Res. 2011 Sep;469(9):2469-75. 12. Boileau P, Moineau G, Roussanne Y, O’Shea K. Bony increased-offset reversed shoulder arthroplasty: minimizing scapular impingement while maximizing glenoid fixation. Clin Orthop Relat Res. 2011 Sep;469(9):2558-67. 13. Mizuno N, Denard PJ, Raiss P, Walch G. The clinical and radiographical results of reverse total shoulder arthroplasty with eccentric glenosphere. Int Orthop. 2012 Aug;36(8):1647-53. Epub 2012 Apr 26. 14. Edwards TB, Trappey GJ, Riley C, O’Connor DP, Elkousy HA, Gartsman GM. Inferior tilt of the glenoid component does not decrease scapular notching in reverse shoulder arthroplasty: results of a prospective randomized study. J Shoulder Elbow Surg. 2012 May;21(5):641-6. Epub 2011 Nov 12. 15. Walch G, Bacle G, L¨adermann A, Nov´e-Josserand L, Smithers CJ. Do the indications, results, and complications of reverse shoulder arthroplasty change with surgeon’s experience? J Shoulder Elbow Surg. 2012 Nov;21(11):1470-7. Epub 2012 Feb 22. 16. Bufquin T, Hersan A, Hubert L, Massin P. Reverse shoulder arthroplasty for the treatment of three- and four-part fractures of the proximal humerus in the elderly: a prospective review of 43 cases with a short-term follow-up. J Bone Joint Surg Br. 2007 Apr;89(4):516-20. 17. Young SW, Everts NM, Ball CM, Astley TM, Poon PC. The SMR reverse shoulder prosthesis in the treatment of cuff-deficient shoulder conditions. J Shoulder Elbow Surg. 2009 Jul-Aug;18(4):622-6. Epub 2009 Apr 11.
18. De Biase CF, Delcogliano M, Borroni M, Castagna A. Reverse total shoulder arthroplasty: radiological and clinical result using an eccentric glenosphere. Musculoskelet Surg. 2012 May;96(Suppl 1):S27-34. Epub 2012 Apr 20. 19. Frankle M, Siegal S, Pupello D, Saleem A, Mighell M, Vasey M. The Reverse Shoulder Prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency. A minimum two-year follow-up study of sixty patients. J Bone Joint Surg Am. 2005 Aug;87(8):1697-705. 20. Cuff D, Pupello D, Virani N, Levy J, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency. J Bone Joint Surg Am. 2008 Jun;90(6): 1244-51. 21. Mulieri P, Dunning P, Klein S, Pupello D, Frankle M. Reverse shoulder arthroplasty for the treatment of irreparable rotator cuff tear without glenohumeral arthritis. J Bone Joint Surg Am. 2010 Nov 3;92(15):2544-56. 22. Cuff D, Clark R, Pupello D, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency: a concise follow-up, at a minimum of five years, of a previous report. J Bone Joint Surg Am. 2012 Nov 7;94(21):1996-2000. 23. Roche CP, Marczuk Y, Wright TW, Flurin PH, Grey S, Jones R, Routman HD, Gilot G, Zuckerman JD. Scapular notching and osteophyte formation after reverse shoulder replacement: Radiological analysis of implant position in male and female patients. Bone Joint J. 2013 Apr;95-B(4):530-5. 24. Valenti P, Sauzi`eres P, Katz D, Kalouche I, Kilinc AS. Do less medialized reverse shoulder prostheses increase motion and reduce notching? Clin Orthop Relat Res. 2011 Sep;469(9):2550-7. 25. Nyffeler RW, Werner CM, Gerber C. Biomechanical relevance of glenoid component positioning in the reverse Delta III total shoulder prosthesis. J Shoulder Elbow Surg. 2005 Sep-Oct;14(5):524-8. 26. de Wilde LF, Poncet D, Middernacht B, Ekelund A. Prosthetic overhang is the most effective way to prevent scapular conflict in a reverse total shoulder prosthesis. Acta Orthop.2010 Dec;81(6):719-26. 27. Chou J, Malak SF, Anderson IA, Astley T, Poon PC. Biomechanical evaluation of different designs of glenospheres in the SMR reverse total shoulder prosthesis: range of motion and risk of scapular notching. J Shoulder Elbow Surg. 2009 MayJun;18(3):354-9. 28. Lee JHE, Van Raalte V, Malian V. Diagnosis of SLAP lesions with Grasheyview arthrography. Skeletal Radiol. 2003 Jul;32(7):388-95. Epub 2003 May 21. 29. Hamada K, Yamanaka K, Uchiyama Y, Mikasa T, Mikasa M. A radiographic classification of massive rotator cuff tear arthritis. Clin Orthop Relat Res. 2011 Sep;469(9):2452-60. 30. Kohut G, Dallmann F, Irlenbusch U. Wear-induced loss of mass in reversed total shoulder arthroplasty with conventional and inverted bearing materials. J Biomech. 2012 Feb 2;45(3):469-73. Epub 2011 Dec 27. 31. Middernacht B, De Roo PJ, Van Maele G, De Wilde LF. Consequences of scapular anatomy for reversed total shoulder arthroplasty. Clin Orthop Relat Res. 2008 Jun;466(6):1410-8. Epub 2008 Mar 6. 32. Harman M, Frankle M, Vasey M, Banks S. Initial glenoid component fixation in ‘‘reverse’’ total shoulder arthroplasty: a biomechanical evaluation. J Shoulder Elbow Surg. 2005 Jan-Feb;14(1)(Suppl S):162S-7S. 33. Poon PC, Chou J, Young D, Malak SF, Anderson IA. Biomechanical evaluation of different designs of glenospheres in the SMR reverse shoulder prosthesis: micromotion of the baseplate and risk of loosening. Shoulder & Elbow. 2010;2(2):94-9. 34. Guti´errez S, Walker M, Willis M, Pupello DR, Frankle MA. Effects of tilt and glenosphere eccentricity on baseplate/bone interface forces in a computational model, validated by a mechanical model, of reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2011 Jul;20(5):732-9. Epub 2011 Feb 2.
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