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The influence of humeral neck shaft angle and glenoid lateralization on range of motion in reverse shoulder arthroplasty
ARTICLE IN PRESS J Shoulder Elbow Surg (2017) ■■, ■■–■■
www.elsevier.com/locate/ymse
ORIGINAL ARTICLE
The influence of humeral neck shaft angle and glenoid lateralization on range of motion in reverse shoulder arthroplasty Birgit S. Werner, MDa,b,*, Jean Chaoui, PhDc, Gilles Walch, MDb a
Clinic for Shoulder and Elbow Surgery, Bad Neustadt, Saale, Germany Centre Orthopédique Santy, Hôpital Jean Mermoz, Lyon, France c Imascap, Brest, France b
Background: Recent developments in reverse shoulder arthroplasty (RSA) have focused on changes in several design-related parameters, including humeral component design, to allow for easier convertibility. Alterations in humeral inclination and offset on shoulder kinematics may have a relevant influence on postoperative outcome. This study used a virtual computer simulation to evaluate the influence of humeral neck shaft angle and glenoid lateralization on range of motion in onlay design RSA. Methods: Three-dimensional RSA computer templating was created from computed tomography (CT) scans in 20 patients undergoing primary total shoulder arthroplasty for concentric osteoarthritis (Walch A1). Two concurrent factors were tested for impingement-free range of motion: humeral inclination (135° vs. 145°) and glenoid lateralization (0 mm vs. 5 mm). Results: Decreasing the humeral neck shaft angle demonstrated a significant increase in impingementfree range of motion. Compared to the 145° configuration, extension was increased by 42.3° (−8.5° to 73.5°), adduction by 15° (10° to 23°), and external rotation with the arm at side by 15.1° (8.5° to 26.5°); however, abduction was decreased by 6.5° (−1° to 12.5°). Glenoid lateralization led to comparable results, but an additional increase in abduction of 7.6° (−1° to 16.5°) and forward flexion of 26.6° (6.5° to 62°) was observed. Conclusion: Lower humeral neck shaft angle and glenoid lateralization are effective for improvement in range of motion after RSA. The use of the 135° model with 5 mm of glenoid lateralization provided the best results in impingement-free range of motion, except for abduction. Level of evidence: Basic Science Study; Computer Modeling © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Reverse shoulder arthroplasty; range of motion; onlay design; humeral inclination; impingement; preoperative planning
The Centre Orthopédique Santy/Hôpital Privé Jean Mermoz, Lyon, France, Institutional Review Board and Ethics Committee approved this study (ref. study 2016-15). *Reprint requests: Birgit S. Werner, MD, Clinic for Shoulder and Elbow Surgery, Salzburger Leite 1, Bad Neustadt, D-97616 Bad Neustadt/Saale, Germany. E-mail address: [email protected] (B.S. Werner).
Reverse shoulder arthroplasty (RSA) is a beneficial treatment option for cuff-deficient shoulders. The traditional Grammont prosthesis relies on medialization and inferiorization of the center of rotation to restore mobility. However, some problems have been observed at long-term follow-up because
1058-2746/$ - see front matter © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. http://dx.doi.org/10.1016/j.jse.2017.03.032
ARTICLE IN PRESS 2 of the prosthetic design. Scapular notching is the most common complication, occurring in up to 88% of patients, with an increasing rate of grade 3 and 4 notching over time.6,13,14,17,18,21 In addition to a mechanical abutment of the humeral component at the scapular neck, Lädermann et al11 recently described the friction-type, occurring in a combined movement of extension and rotation with the arm at side. Moreover, some authors observed a decrease in active rotation,4,21 despite an improvement in active elevation and abduction for the Grammont-type prosthesis.4,6,17,18,21 The concept of bony or metallic lateralization of the glenoid component has been reported to be a viable option to increase impingement-free range of motion (ROM),.3,7,8,20 Lateralization of the glenoid component leads to increased internal and external rotation3,7,8 and has been reported to decrease the incidence of scapular notching.1 Prostheses with new designs have been developed to allow for easier convertibility from anatomic shoulder arthroplasty to RSA. Some authors have suggested that more anatomic humeral inclination would reduce scapular notching.5,9,10 To date, there are no guidelines for the ideal configuration of both humeral and glenoid positioning to obtain the best functional results in elevation and rotation. This study used computer simulation to evaluate the influence of humeral neck shaft angle and glenoid lateralization on ROM as well as impingement in onlay design RSA. We hypothesized that decreased humeral inclination and glenoid lateralization would increase impingement-free mobility.
Materials and methods We analyzed 20 computed tomography (CT) scans obtained from patients for whom primary total shoulder arthroplasty for concentric osteoarthritis (Walch A1) by the senior author (G.W.) was planned. Patients met inclusion criteria if they demonstrated an anteroposterior glenoid width of less than 30 mm to exclude any bony overhang with use of a 29-mm baseplate. All CT scans were processed by Glenosys, a validated 3-dimensional (3D) software program (Imascap, Brest, France).15 After segmentation and 3D reconstruction, the software automatically provides measurements of glenoid version with respect to the scapular plane and glenoid inclination in the frontal plane with respect to the transverse axis of the scapula. The mean superior inclination was 7.6° (standard deviation, 6.4°), and glenoid retroversion averaged 7.8° (standard deviation, 5.5°). The software program allows for virtual implantation of the humeral and glenoid components. Inclination of the humeral component is related to the level of the humeral cut with respect to the diaphyseal axis. A virtual RSA model was used to test 4 different configurations in all 20 patients. In all cases, a 29-mm baseplate was positioned at the inferior part of the glenoid with the central peg placed in the middle of the glenoid width to avoid bony overhang. All configurations consisted of a 36-mm glenosphere with 2-mm inferior eccentricity. A neutral position was used for inclination and version. The humeral cut was virtually performed at the anatomic neck, respecting the patient’s anatomic humeral version. The onlay design prosthesis (Aequalis Ascend Flex; Wright Medical,
B.S. Werner et al. Bloomington, MN, USA) was inserted with the humeral tray inevitably positioned in the same offset position at the level of the greater tuberosity. Two concurrent factors were tested: glenoid lateralization and humeral neck shaft angle. The glenoid component was inserted flush with the inferior rim of the glenoid, with or without additional 5 mm of bony lateralization. The neck shaft angle of 135° or 145° was simulated using a prosthetic inclination of 127.5° combined with an asymmetric 7.5° polyethylene insert and a prosthetic inclination of 132.5° with a 12.5° polyethylene insert, respectively (Fig. 1). All configurations were tested for impingement-free ROM in abduction-adduction, forward flexion-extension, and external and internal rotation with the arm at side. Global ROM defined as a sum of all 6 motions using the Glenosys 3D software. The ROM simulation is based on collision detection between 2 or more objects. The 3D computer model allows for a resolution of 1°. The maximum values for each motion until encountering bone-to-bone or bone-to-implant impingement on the scapula or acromion were documented.
Statistics All statistical analysis was performed using MedCalc 12.0 software (MedCalc Software bvba, Ostend, Belgium). A multivariable linear regression analysis was used to analyze the effect of glenoid lateralization and humeral inclination on ROM. A multivariate analysis of variance was performed for each of the ROM variables. The level of significance was set at P < .05.
Results Influence of humeral inclination on ROM The use of a 135° model demonstrated a mean increase in impingement-free ROM of 77.5° (20° to 112.5°, P < .0001), with superior values for each motion tested but abduction. This was statistically significant for adduction (P < .001), external rotation (P < .05), extension in the lateralized glenoid configuration (P < .001), and internal rotation in standard glenoid positioning (P = .02). The results for pairwise comparison are presented in Table I. The 135° configuration led to doubled values for extension, with a mean increase of 42.3° (−8.5° to 73.5°). Adduction was improved by 15° (10° to 23°), whereas a mean decrease of 6.5° (−1° to 12.5°) in abduction was observed. Internal rotation with the arm at side was increased by 7° (2.5° to 15°), and external rotation improved by 15.1° (8.5° to 26.5°) with the 135° model. There was no significant difference in forward flexion.
Influence of glenoid lateralization on ROM Glenoid lateralization of 5 mm in the center of the peg resulted in significantly improved ROM, with a mean of 106.3° (44° to 148°, P < .0001), regardless of the humeral inclination. This was statistically significant for adduction, with a mean increase of 14.2° (10.5° to 19°), forward flexion, external rotation, and extension with use of the 135° model.
ARTICLE IN PRESS Humeral inclination in onlay RSA
3
a
b
Figure 1 (A) Three-dimensional computed tomography planning of the 135° humeral neck shaft angle model with the glenoid component inserted flush with the inferior rim of the glenoid without bony lateralization. In abduction, bone-to-implant impingement was present at the superior edge of the glenoid. (B) Three-dimensional computed tomography planning of the 145° model with an additional 5 mm of bony lateralization of the glenoid component.
ARTICLE IN PRESS .009 331.5 ± 59.5 434.9 ± 63.2
Abduction was improved by 7.6° (−1° to 16.5°) in glenoid lateralization; however, this was not statistically significant. Forward flexion was increased by 26.6° (6.5° to 62°), and extension improved by 35.7° (−28.5° to 60°). Amelioration in external and internal rotation with the arm at the side was comparable to the values obtained in decreasing the humeral inclination, with an increase of 17.7° (9.5° to 25°) and 4.7° (−2.5° to 12), respectively.
Impingement Impingement of the greater tuberosity at the superior edge of the glenoid was more frequently observed in standard glenoid positioning, whereas glenoid lateralization led to acromial impingement in 85% of cases regardless of the humeral configuration (Table II). This was most apparent for forward flexion, with 82% of glenoid impingement in standard positioning. The 135° model demonstrated increased values for extension and rotation, reducing the risk for friction-type impingement. Changing the humeral neck shaft angle demonstrated the most important influence on impingementfree adduction (P < .0001), extension (P < .0001), internal and external rotation (P < .0001), and global ROM (P < .0001), whereas glenoid lateralization was more effective on abduction (P = .0002) and forward flexion (P = .0002). No correlation was found between preoperative glenoid morphology and postoperative ROM.
Discussion
NS, not significant. * All values are reported in degrees ± standard deviation.
.001 434.9 ± 63.2 515.3 ± 54 .004
406.1 ± 62.5 515.3 ± 54
.0003
<.0001 50.1 ± 11.3 29.2 ± 16.5 .049 50.1 ± 11.3 61.9 ± 9.4 .0001
47.5 ± 12.5
61.9 ± 9.4
.004
NS <.0001 <.0001 NS NS .05 <.0001 .008 .0001 NS 72.4 ± 5.9 80.6 ± 9.1 29.2 ± 8.9 43.3 ± 8.2 105.3 ± 13.6 126.7 ± 18.2 58.4 ± 40 106.3 ± 26.3 93.5 ± 7.7 96.6 ± 9.4 NS <.0001 NS <.0001 NS 86.4 ± 10.3 28.3 ± 7.8 127.2 ± 12.2 51.7 ± 33.8 91.2 ± 7.9 80.6 ± 9.1 43.3 ± 8.2 126.7 ± 18.2 106.3 ± 26.3 96.6 ± 9.4 NS <.0001 NS NS .02
Abduction 72.4 ± 5.9 79.5 ± 7.8 Adduction 29.2 ± 8.9 14.1 ± 8.5 Forward flexion 105.3 ± 13.6 95.5 ± 22.4 Extension 58.4 ± 40 28.3 ± 30.4 Internal rotation 93.5 ± 7.7 85 ± 9.2 at 0° External rotation 47.5 ± 12.5 29.2 ± 16.5 at 0° Global range of 406.1 ± 62.5 331.5 ± 59.5 motion
135° P value 145° model +5 mm model P value 135° 145° P value 135° model +5 mm model +5 mm model 145° model
Pairwise comparison of the influence of humeral neck shaft angle on range of motion for all different configurations
135° model Variable*
Table I
79.5 ± 7.8 86.4 ± 10.3 14.1 ± 8.5 28.3 ± 7.8 95.5 ± 22.4 127.2 ± 12.2 28.3 ± 30.4 51.7 ± 33.8 85 ± 9.2 91.2 ± 7.9
B.S. Werner et al. 145° P value +5 mm model
4
Impingement on the inferior part of the scapula leading to scapular notching is one of the main complications in RSA. To minimize scapular notching and enhance functional results, different strategies and prosthetic designs for RSA have been proposed and are currently on the market. Nyffeler et al16 demonstrated that baseplate positioning at the inferior border of the glenoid decreases notching because the glenosphere extends below the inferior border of the glenoid. Variations in design parameters are inherent with each company’s prosthesis, including the offset of the center of rotation and the humeral neck shaft angle. The implications of these variables on shoulder kinematics are poorly understood and may have a significant effect on the outcome after RSA. We used CT scans of patients with primary osteoarthritis and minimally deformed glenoids to evaluate the biomechanical effect of glenoid lateralization and humeral component inclination on ROM and impingement in onlay RSA. This preselection of scapula morphology allows for testing of the inherent differences in ROM related to the geometry of the devices independent of glenoid erosion. The purpose of our study was not to create a surgical technique but to determine how different parameters contribute to the total glenohumeral abduction ROM and adduction deficit in a reverse shoulder model.
ARTICLE IN PRESS Humeral inclination in onlay RSA Table II
5
Distribution of abutment during abduction and forward flexion with regard to the prosthetic configurations in percentage
Variable
135° 145° 135° +5 mm 145° +5 mm
Abduction
Forward flexion
Glenoid
Acromion
Coracoid
Glenoid
Acromion
Coracoid
(%)
(%)
(%)
(%)
(%)
(%)
55 35 10 15
45 65 85 85
0 0 5 0
75 90 15 10
25 5 85 85
0 5 0 5
According to our results, glenoid lateralization improved all directions of ROM. This was statistically significant for adduction, forward flexion, and external rotation with the arm at the side. Glenoid lateralization is known to improve ROM but has an additional influence on scapular impingement and notching.3,7,8,20 Langohr et al12 reported the influence of glenosphere configuration on ROM in a cadaveric study. They found that glenoid lateralization significantly increased the abduction and adduction angle without any difference at varying glenosphere sizes. Berhouet et al2 demonstrated that glenoid lateralization and the use of a larger glenosphere size is successful in reducing scapular notching. Using a 2D computer model, De Wilde et al5 found that a lateralization of the center of rotation to 5 mm led to a gain of 16° in adduction, similar to our results. The humeral neck shaft angle has also been reported to influence ROM. De Wilde et al5 showed that a reduction of the humeral neck shaft angle from 155° to 145° resulted in a gain of 10° in impingement-free adduction. Gutierrez et al9 found that decreasing the humeral neck shaft angle up to 130° had the largest effect on decreasing the adduction deficit. However, they analyzed only 1 sawbone model, and there was a lack of significant difference to the matched control group. Consequently, impingement-free abduction is limited.5,17 In our study, the use of a 145° model resulted in inferior values for all directions of ROM tested except abduction. Changing the humeral inclination from 145° to 135° improved adduction by 15°, whereas abduction was reduced by 6.5°. This is comparable to Lädermann et al,10 who reported an increase of 6° for adduction and an abduction deficit of almost 6° in a 3D computer model for onlay RSA. However, in contrast to both Gutierrez et al9 and Lädermann et al,10 we observed a significant difference in improving adduction ROM by lowering the humeral neck shaft angle. Abduction in RSA is limited to impingement on the acromion or the superior edge of the glenoid. In our study, the decrease of humeral inclination to a 135° configuration led to a decrease in abduction ROM. The lowest values for abduction were noted in the 135° configuration without glenoid lateralization. Lateralization of the glenoid baseplate improved abduction to an average of 8°. This finding is supported by a virtual computer simulation performed by Gutierrez et al9
in which they found glenoid lateralization was the most effective factor for improvement in abduction ROM. Tashjian et al19 confirmed this finding in a cadaveric model. According to our results, the 135° model with 5 mm of glenoid lateralization was the best compromise in impingementfree abduction, adduction, and global function. Lowering of the humeral neck shaft angle led to a similar increase in external and internal rotation when compared with glenoid lateralization. Moreover, we observed that glenoid and humeral positioning influenced the localization of bony impingement. In standard glenoid positioning, impingement occurred at the superior edge of the glenoid, whereas acromial impingement was present in lateralized center of rotation. Superior values for extension and rotation were noted in the decreased neck shaft angle model, indicating a potential benefit in limiting scapular notching by reducing friction. Our study found that changing the humeral inclination had the largest effect on impingement-free adduction, extension, rotation, and global ROM, whereas glenoid lateralization was the most important parameter for impingement-free abduction and forward flexion. We therefore conclude that humeral and glenoid positioning both influence the type of impingement. Limitations of this study include the restriction to an onlay design prosthesis, the use of a single size of glenosphere, and the lack of variation in baseplate positioning in version, inferiorization, and inclination as well as humeral retroversion. We used a computational model without any soft tissue or muscle simulation; therefore, we are not able to comment on the influence of muscle and tendon forces. We are aware that the prosthetic configurations and positioning used in this study may be unfeasible clinically because of soft tissue contractures or stretching. Our model consisted of small glenoids with little glenoid erosion; therefore, our results may not be applicable to all clinical situations in which an RSA is proposed, especially in glenoid and humeral bone loss. We are not able to validate our results in larger glenoids extending beyond the anterior and posterior border of the baseplate. However, the aim of our study was to analyze the best ROM obtainable in a normal shoulder using the RSA. It should be stated that we did not aim at determining the safe limits of any parameter tested.
ARTICLE IN PRESS 6
B.S. Werner et al.
Conclusions We found that lower humeral neck shaft angle and glenoid lateralization are effective for improvement in ROM after RSA. The use of the 135° model with 5 mm of glenoid lateralization provided the best results in impingementfree ROM, except for abduction.
Disclaimer Birgit S. Werner, her immediate family, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article. Jean Chaoui has equity in Imascap related to the subject of this article. Gilles Walch receives royalties from Tornier and equity from Imascap related to the subject of this article.
References 1. Athwal GS, MacDermid JC, Reddy KM, Marsh JP, Faber KJ, Drosdowech D. Does bony increased-offset reverse shoulder arthroplasty decrease scapular notching? J Shoulder Elbow Surg 2015;24:468-73. http://dx.doi.org/10.1016/j.jse.2014.08.015 2. Berhouet J, Garaud P, Favard L. Evaluation of the role of glenosphere design and humeral component retroversion in avoiding scapular notching during reverse shoulder arthroplasty. J Shoulder Elbow Surg 2014;23:151-8. http://dx.doi.org/10.1016/j.jse.2013.05.009 3. 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;469:2558-67. http://dx.doi.org/10.1007/s11999-011-1775-4 4. Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg 2005;14(Suppl S):147S-61S. http://dx.doi.org/10.1016/j.jse.2004.10.006 5. 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;81:719-26. http://dx.doi.org/10 .3109/17453674.2010.538354 6. 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;469:2469-75. http://dx.doi.org/10.1007/s11999-011-1833-y 7. 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;87:1697-705. http://dx.doi .org/10.2106/JBJS.D.02813
8. Greiner S, Schmidt C, Herrmann S, Pauly S, Perka C. Clinical performance of lateralized versus non-lateralized reverse shoulder arthroplasty: a prospective randomized study. J Shoulder Elbow Surg 2015;24:1397-404. http://dx.doi.org/10.1016/j.jse.2015.05.041 9. Gutiérrez S 4th, Comiskey CA, Luo ZP, Pupello DR, Frankle MA. Range of impingement-free abduction and adduction deficit after reverse shoulder arthroplasty. Hierarchy of surgical and implant- design-related factors. J Bone Joint Surg Am 2008;90:2606-15. http://dx.doi.org/10 .2106/JBJS.H.00012 10. Lädermann A, Denard PJ, Boileau P, Farron A, Deransart P, Terrier A, et al. Effect of humeral stem design on humeral position and range of motion in reverse shoulder arthroplasty. Int Orthop 2015;39:2205-13. http://dx.doi.org/10.1007/s00264-015-2984-3 11. Lädermann A, Gueorguiev B, Charbonnier C, Stimec BV, Fasel JH, Zderic I, et al. Scapular notching on kinematic simulated range of motion after reverse shoulder arthroplasty is not the result of impingement in adduction. Medicine (Baltimore) 2015;94:e1615. http://dx.doi.org/10 .1097/MD.0000000000001615 12. Langohr GD, Giles JW, Athwal GS, Johnson JA. The effect of glenosphere diameter in reverse shoulder arthroplasty on muscle force, joint load, and range of motion. J Shoulder Elbow Surg 2015;24:972-9. http://dx.doi.org/10.1016/j.jse.2014.10.018 13. Lévigne C, Boileau P, Favard L, Garaud P, Molé D, Sirveaux F, et al. Scapular notching in reverse shoulder arthroplasty. J Shoulder Elbow Surg 2008;17:925-35. http://dx.doi.org/10.1016/j.jse.2008.02.010 14. Melis B, DeFranco M, Lädermann A, Molé D, Favard L, Nérot C, et al. An evaluation of the radiological changes around the Grammont reverse geometry shoulder arthroplasty after eight to 12 years. J Bone Joint Surg Br 2011;93:1240-6. http://dx.doi.org/10.1302/0301-620X.93B9.25926 15. Moineau G, Levigne C, Boileau P, Young A, Walch G. Threedimensional measurement method of arthritic glenoid cavity morphology: feasibility and reproducibility. Orthop Traumatol Surg Res 2012;98(Suppl):S139-45. http://dx.doi.org/10.1016/j.otsr.2012.06.007 16. 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;14:524-8. http://dx.doi.org/10.1016/ j.jse.2004.09.010 17. Roche C, Flurin PH, Wright T, Crosby LA, Mauldin M, Zuckerman JD. An evaluation of the relationships between reverse shoulder design parameters and range of motion, impingement, and stability. J Shoulder Elbow Surg 2009;18:734-41. http://dx.doi.org/10.1016/j.jse.2008.12.008 18. Sirveaux F, Favard L, Oudet D, Huguet D, Walch G, Mole 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;86:388-95. http://dx.doi.org/10.1302/0301-620X.86B3.14024 19. Tashjian RZ, Burks RT, Zhang Y, Henninger HB. Reverse total shoulder arthroplasty: a biomechanical evaluation of humeral and glenosphere hardware configuration. J Shoulder Elbow Surg 2015;24:e68-77. http://dx.doi.org/10.1016/j.jse.2014.08.017 20. Valenti P, Sauzières P, Katz D, Kalouche I, Kilinc AS. Do less medialized reverse shoulder prostheses increase motion and reduce notching? Clin Orthop Relat Res 2011;469:2550-7. http://dx.doi.org/10.1007/ s11999-011-1844-8 21. Werner CM, Steinmann PA, Gilbart M, Gerber C. Treatment of painful pseudoparesis due to irreparable rotator cuff dysfunction with the Delta III reverse-ball-and-socket total shoulder prosthesis. J Bone Joint Surg Am 2005;87:1476-86. http://dx.doi.org/10.2106/JBJS.D.02342
www.elsevier.com/locate/ymse
ORIGINAL ARTICLE
The influence of humeral neck shaft angle and glenoid lateralization on range of motion in reverse shoulder arthroplasty Birgit S. Werner, MDa,b,*, Jean Chaoui, PhDc, Gilles Walch, MDb a
Clinic for Shoulder and Elbow Surgery, Bad Neustadt, Saale, Germany Centre Orthopédique Santy, Hôpital Jean Mermoz, Lyon, France c Imascap, Brest, France b
Background: Recent developments in reverse shoulder arthroplasty (RSA) have focused on changes in several design-related parameters, including humeral component design, to allow for easier convertibility. Alterations in humeral inclination and offset on shoulder kinematics may have a relevant influence on postoperative outcome. This study used a virtual computer simulation to evaluate the influence of humeral neck shaft angle and glenoid lateralization on range of motion in onlay design RSA. Methods: Three-dimensional RSA computer templating was created from computed tomography (CT) scans in 20 patients undergoing primary total shoulder arthroplasty for concentric osteoarthritis (Walch A1). Two concurrent factors were tested for impingement-free range of motion: humeral inclination (135° vs. 145°) and glenoid lateralization (0 mm vs. 5 mm). Results: Decreasing the humeral neck shaft angle demonstrated a significant increase in impingementfree range of motion. Compared to the 145° configuration, extension was increased by 42.3° (−8.5° to 73.5°), adduction by 15° (10° to 23°), and external rotation with the arm at side by 15.1° (8.5° to 26.5°); however, abduction was decreased by 6.5° (−1° to 12.5°). Glenoid lateralization led to comparable results, but an additional increase in abduction of 7.6° (−1° to 16.5°) and forward flexion of 26.6° (6.5° to 62°) was observed. Conclusion: Lower humeral neck shaft angle and glenoid lateralization are effective for improvement in range of motion after RSA. The use of the 135° model with 5 mm of glenoid lateralization provided the best results in impingement-free range of motion, except for abduction. Level of evidence: Basic Science Study; Computer Modeling © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Reverse shoulder arthroplasty; range of motion; onlay design; humeral inclination; impingement; preoperative planning
The Centre Orthopédique Santy/Hôpital Privé Jean Mermoz, Lyon, France, Institutional Review Board and Ethics Committee approved this study (ref. study 2016-15). *Reprint requests: Birgit S. Werner, MD, Clinic for Shoulder and Elbow Surgery, Salzburger Leite 1, Bad Neustadt, D-97616 Bad Neustadt/Saale, Germany. E-mail address: [email protected] (B.S. Werner).
Reverse shoulder arthroplasty (RSA) is a beneficial treatment option for cuff-deficient shoulders. The traditional Grammont prosthesis relies on medialization and inferiorization of the center of rotation to restore mobility. However, some problems have been observed at long-term follow-up because
1058-2746/$ - see front matter © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. http://dx.doi.org/10.1016/j.jse.2017.03.032
ARTICLE IN PRESS 2 of the prosthetic design. Scapular notching is the most common complication, occurring in up to 88% of patients, with an increasing rate of grade 3 and 4 notching over time.6,13,14,17,18,21 In addition to a mechanical abutment of the humeral component at the scapular neck, Lädermann et al11 recently described the friction-type, occurring in a combined movement of extension and rotation with the arm at side. Moreover, some authors observed a decrease in active rotation,4,21 despite an improvement in active elevation and abduction for the Grammont-type prosthesis.4,6,17,18,21 The concept of bony or metallic lateralization of the glenoid component has been reported to be a viable option to increase impingement-free range of motion (ROM),.3,7,8,20 Lateralization of the glenoid component leads to increased internal and external rotation3,7,8 and has been reported to decrease the incidence of scapular notching.1 Prostheses with new designs have been developed to allow for easier convertibility from anatomic shoulder arthroplasty to RSA. Some authors have suggested that more anatomic humeral inclination would reduce scapular notching.5,9,10 To date, there are no guidelines for the ideal configuration of both humeral and glenoid positioning to obtain the best functional results in elevation and rotation. This study used computer simulation to evaluate the influence of humeral neck shaft angle and glenoid lateralization on ROM as well as impingement in onlay design RSA. We hypothesized that decreased humeral inclination and glenoid lateralization would increase impingement-free mobility.
Materials and methods We analyzed 20 computed tomography (CT) scans obtained from patients for whom primary total shoulder arthroplasty for concentric osteoarthritis (Walch A1) by the senior author (G.W.) was planned. Patients met inclusion criteria if they demonstrated an anteroposterior glenoid width of less than 30 mm to exclude any bony overhang with use of a 29-mm baseplate. All CT scans were processed by Glenosys, a validated 3-dimensional (3D) software program (Imascap, Brest, France).15 After segmentation and 3D reconstruction, the software automatically provides measurements of glenoid version with respect to the scapular plane and glenoid inclination in the frontal plane with respect to the transverse axis of the scapula. The mean superior inclination was 7.6° (standard deviation, 6.4°), and glenoid retroversion averaged 7.8° (standard deviation, 5.5°). The software program allows for virtual implantation of the humeral and glenoid components. Inclination of the humeral component is related to the level of the humeral cut with respect to the diaphyseal axis. A virtual RSA model was used to test 4 different configurations in all 20 patients. In all cases, a 29-mm baseplate was positioned at the inferior part of the glenoid with the central peg placed in the middle of the glenoid width to avoid bony overhang. All configurations consisted of a 36-mm glenosphere with 2-mm inferior eccentricity. A neutral position was used for inclination and version. The humeral cut was virtually performed at the anatomic neck, respecting the patient’s anatomic humeral version. The onlay design prosthesis (Aequalis Ascend Flex; Wright Medical,
B.S. Werner et al. Bloomington, MN, USA) was inserted with the humeral tray inevitably positioned in the same offset position at the level of the greater tuberosity. Two concurrent factors were tested: glenoid lateralization and humeral neck shaft angle. The glenoid component was inserted flush with the inferior rim of the glenoid, with or without additional 5 mm of bony lateralization. The neck shaft angle of 135° or 145° was simulated using a prosthetic inclination of 127.5° combined with an asymmetric 7.5° polyethylene insert and a prosthetic inclination of 132.5° with a 12.5° polyethylene insert, respectively (Fig. 1). All configurations were tested for impingement-free ROM in abduction-adduction, forward flexion-extension, and external and internal rotation with the arm at side. Global ROM defined as a sum of all 6 motions using the Glenosys 3D software. The ROM simulation is based on collision detection between 2 or more objects. The 3D computer model allows for a resolution of 1°. The maximum values for each motion until encountering bone-to-bone or bone-to-implant impingement on the scapula or acromion were documented.
Statistics All statistical analysis was performed using MedCalc 12.0 software (MedCalc Software bvba, Ostend, Belgium). A multivariable linear regression analysis was used to analyze the effect of glenoid lateralization and humeral inclination on ROM. A multivariate analysis of variance was performed for each of the ROM variables. The level of significance was set at P < .05.
Results Influence of humeral inclination on ROM The use of a 135° model demonstrated a mean increase in impingement-free ROM of 77.5° (20° to 112.5°, P < .0001), with superior values for each motion tested but abduction. This was statistically significant for adduction (P < .001), external rotation (P < .05), extension in the lateralized glenoid configuration (P < .001), and internal rotation in standard glenoid positioning (P = .02). The results for pairwise comparison are presented in Table I. The 135° configuration led to doubled values for extension, with a mean increase of 42.3° (−8.5° to 73.5°). Adduction was improved by 15° (10° to 23°), whereas a mean decrease of 6.5° (−1° to 12.5°) in abduction was observed. Internal rotation with the arm at side was increased by 7° (2.5° to 15°), and external rotation improved by 15.1° (8.5° to 26.5°) with the 135° model. There was no significant difference in forward flexion.
Influence of glenoid lateralization on ROM Glenoid lateralization of 5 mm in the center of the peg resulted in significantly improved ROM, with a mean of 106.3° (44° to 148°, P < .0001), regardless of the humeral inclination. This was statistically significant for adduction, with a mean increase of 14.2° (10.5° to 19°), forward flexion, external rotation, and extension with use of the 135° model.
ARTICLE IN PRESS Humeral inclination in onlay RSA
3
a
b
Figure 1 (A) Three-dimensional computed tomography planning of the 135° humeral neck shaft angle model with the glenoid component inserted flush with the inferior rim of the glenoid without bony lateralization. In abduction, bone-to-implant impingement was present at the superior edge of the glenoid. (B) Three-dimensional computed tomography planning of the 145° model with an additional 5 mm of bony lateralization of the glenoid component.
ARTICLE IN PRESS .009 331.5 ± 59.5 434.9 ± 63.2
Abduction was improved by 7.6° (−1° to 16.5°) in glenoid lateralization; however, this was not statistically significant. Forward flexion was increased by 26.6° (6.5° to 62°), and extension improved by 35.7° (−28.5° to 60°). Amelioration in external and internal rotation with the arm at the side was comparable to the values obtained in decreasing the humeral inclination, with an increase of 17.7° (9.5° to 25°) and 4.7° (−2.5° to 12), respectively.
Impingement Impingement of the greater tuberosity at the superior edge of the glenoid was more frequently observed in standard glenoid positioning, whereas glenoid lateralization led to acromial impingement in 85% of cases regardless of the humeral configuration (Table II). This was most apparent for forward flexion, with 82% of glenoid impingement in standard positioning. The 135° model demonstrated increased values for extension and rotation, reducing the risk for friction-type impingement. Changing the humeral neck shaft angle demonstrated the most important influence on impingementfree adduction (P < .0001), extension (P < .0001), internal and external rotation (P < .0001), and global ROM (P < .0001), whereas glenoid lateralization was more effective on abduction (P = .0002) and forward flexion (P = .0002). No correlation was found between preoperative glenoid morphology and postoperative ROM.
Discussion
NS, not significant. * All values are reported in degrees ± standard deviation.
.001 434.9 ± 63.2 515.3 ± 54 .004
406.1 ± 62.5 515.3 ± 54
.0003
<.0001 50.1 ± 11.3 29.2 ± 16.5 .049 50.1 ± 11.3 61.9 ± 9.4 .0001
47.5 ± 12.5
61.9 ± 9.4
.004
NS <.0001 <.0001 NS NS .05 <.0001 .008 .0001 NS 72.4 ± 5.9 80.6 ± 9.1 29.2 ± 8.9 43.3 ± 8.2 105.3 ± 13.6 126.7 ± 18.2 58.4 ± 40 106.3 ± 26.3 93.5 ± 7.7 96.6 ± 9.4 NS <.0001 NS <.0001 NS 86.4 ± 10.3 28.3 ± 7.8 127.2 ± 12.2 51.7 ± 33.8 91.2 ± 7.9 80.6 ± 9.1 43.3 ± 8.2 126.7 ± 18.2 106.3 ± 26.3 96.6 ± 9.4 NS <.0001 NS NS .02
Abduction 72.4 ± 5.9 79.5 ± 7.8 Adduction 29.2 ± 8.9 14.1 ± 8.5 Forward flexion 105.3 ± 13.6 95.5 ± 22.4 Extension 58.4 ± 40 28.3 ± 30.4 Internal rotation 93.5 ± 7.7 85 ± 9.2 at 0° External rotation 47.5 ± 12.5 29.2 ± 16.5 at 0° Global range of 406.1 ± 62.5 331.5 ± 59.5 motion
135° P value 145° model +5 mm model P value 135° 145° P value 135° model +5 mm model +5 mm model 145° model
Pairwise comparison of the influence of humeral neck shaft angle on range of motion for all different configurations
135° model Variable*
Table I
79.5 ± 7.8 86.4 ± 10.3 14.1 ± 8.5 28.3 ± 7.8 95.5 ± 22.4 127.2 ± 12.2 28.3 ± 30.4 51.7 ± 33.8 85 ± 9.2 91.2 ± 7.9
B.S. Werner et al. 145° P value +5 mm model
4
Impingement on the inferior part of the scapula leading to scapular notching is one of the main complications in RSA. To minimize scapular notching and enhance functional results, different strategies and prosthetic designs for RSA have been proposed and are currently on the market. Nyffeler et al16 demonstrated that baseplate positioning at the inferior border of the glenoid decreases notching because the glenosphere extends below the inferior border of the glenoid. Variations in design parameters are inherent with each company’s prosthesis, including the offset of the center of rotation and the humeral neck shaft angle. The implications of these variables on shoulder kinematics are poorly understood and may have a significant effect on the outcome after RSA. We used CT scans of patients with primary osteoarthritis and minimally deformed glenoids to evaluate the biomechanical effect of glenoid lateralization and humeral component inclination on ROM and impingement in onlay RSA. This preselection of scapula morphology allows for testing of the inherent differences in ROM related to the geometry of the devices independent of glenoid erosion. The purpose of our study was not to create a surgical technique but to determine how different parameters contribute to the total glenohumeral abduction ROM and adduction deficit in a reverse shoulder model.
ARTICLE IN PRESS Humeral inclination in onlay RSA Table II
5
Distribution of abutment during abduction and forward flexion with regard to the prosthetic configurations in percentage
Variable
135° 145° 135° +5 mm 145° +5 mm
Abduction
Forward flexion
Glenoid
Acromion
Coracoid
Glenoid
Acromion
Coracoid
(%)
(%)
(%)
(%)
(%)
(%)
55 35 10 15
45 65 85 85
0 0 5 0
75 90 15 10
25 5 85 85
0 5 0 5
According to our results, glenoid lateralization improved all directions of ROM. This was statistically significant for adduction, forward flexion, and external rotation with the arm at the side. Glenoid lateralization is known to improve ROM but has an additional influence on scapular impingement and notching.3,7,8,20 Langohr et al12 reported the influence of glenosphere configuration on ROM in a cadaveric study. They found that glenoid lateralization significantly increased the abduction and adduction angle without any difference at varying glenosphere sizes. Berhouet et al2 demonstrated that glenoid lateralization and the use of a larger glenosphere size is successful in reducing scapular notching. Using a 2D computer model, De Wilde et al5 found that a lateralization of the center of rotation to 5 mm led to a gain of 16° in adduction, similar to our results. The humeral neck shaft angle has also been reported to influence ROM. De Wilde et al5 showed that a reduction of the humeral neck shaft angle from 155° to 145° resulted in a gain of 10° in impingement-free adduction. Gutierrez et al9 found that decreasing the humeral neck shaft angle up to 130° had the largest effect on decreasing the adduction deficit. However, they analyzed only 1 sawbone model, and there was a lack of significant difference to the matched control group. Consequently, impingement-free abduction is limited.5,17 In our study, the use of a 145° model resulted in inferior values for all directions of ROM tested except abduction. Changing the humeral inclination from 145° to 135° improved adduction by 15°, whereas abduction was reduced by 6.5°. This is comparable to Lädermann et al,10 who reported an increase of 6° for adduction and an abduction deficit of almost 6° in a 3D computer model for onlay RSA. However, in contrast to both Gutierrez et al9 and Lädermann et al,10 we observed a significant difference in improving adduction ROM by lowering the humeral neck shaft angle. Abduction in RSA is limited to impingement on the acromion or the superior edge of the glenoid. In our study, the decrease of humeral inclination to a 135° configuration led to a decrease in abduction ROM. The lowest values for abduction were noted in the 135° configuration without glenoid lateralization. Lateralization of the glenoid baseplate improved abduction to an average of 8°. This finding is supported by a virtual computer simulation performed by Gutierrez et al9
in which they found glenoid lateralization was the most effective factor for improvement in abduction ROM. Tashjian et al19 confirmed this finding in a cadaveric model. According to our results, the 135° model with 5 mm of glenoid lateralization was the best compromise in impingementfree abduction, adduction, and global function. Lowering of the humeral neck shaft angle led to a similar increase in external and internal rotation when compared with glenoid lateralization. Moreover, we observed that glenoid and humeral positioning influenced the localization of bony impingement. In standard glenoid positioning, impingement occurred at the superior edge of the glenoid, whereas acromial impingement was present in lateralized center of rotation. Superior values for extension and rotation were noted in the decreased neck shaft angle model, indicating a potential benefit in limiting scapular notching by reducing friction. Our study found that changing the humeral inclination had the largest effect on impingement-free adduction, extension, rotation, and global ROM, whereas glenoid lateralization was the most important parameter for impingement-free abduction and forward flexion. We therefore conclude that humeral and glenoid positioning both influence the type of impingement. Limitations of this study include the restriction to an onlay design prosthesis, the use of a single size of glenosphere, and the lack of variation in baseplate positioning in version, inferiorization, and inclination as well as humeral retroversion. We used a computational model without any soft tissue or muscle simulation; therefore, we are not able to comment on the influence of muscle and tendon forces. We are aware that the prosthetic configurations and positioning used in this study may be unfeasible clinically because of soft tissue contractures or stretching. Our model consisted of small glenoids with little glenoid erosion; therefore, our results may not be applicable to all clinical situations in which an RSA is proposed, especially in glenoid and humeral bone loss. We are not able to validate our results in larger glenoids extending beyond the anterior and posterior border of the baseplate. However, the aim of our study was to analyze the best ROM obtainable in a normal shoulder using the RSA. It should be stated that we did not aim at determining the safe limits of any parameter tested.
ARTICLE IN PRESS 6
B.S. Werner et al.
Conclusions We found that lower humeral neck shaft angle and glenoid lateralization are effective for improvement in ROM after RSA. The use of the 135° model with 5 mm of glenoid lateralization provided the best results in impingementfree ROM, except for abduction.
Disclaimer Birgit S. Werner, her immediate family, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article. Jean Chaoui has equity in Imascap related to the subject of this article. Gilles Walch receives royalties from Tornier and equity from Imascap related to the subject of this article.
References 1. Athwal GS, MacDermid JC, Reddy KM, Marsh JP, Faber KJ, Drosdowech D. Does bony increased-offset reverse shoulder arthroplasty decrease scapular notching? J Shoulder Elbow Surg 2015;24:468-73. http://dx.doi.org/10.1016/j.jse.2014.08.015 2. Berhouet J, Garaud P, Favard L. Evaluation of the role of glenosphere design and humeral component retroversion in avoiding scapular notching during reverse shoulder arthroplasty. J Shoulder Elbow Surg 2014;23:151-8. http://dx.doi.org/10.1016/j.jse.2013.05.009 3. 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;469:2558-67. http://dx.doi.org/10.1007/s11999-011-1775-4 4. Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg 2005;14(Suppl S):147S-61S. http://dx.doi.org/10.1016/j.jse.2004.10.006 5. 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;81:719-26. http://dx.doi.org/10 .3109/17453674.2010.538354 6. 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;469:2469-75. http://dx.doi.org/10.1007/s11999-011-1833-y 7. 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;87:1697-705. http://dx.doi .org/10.2106/JBJS.D.02813
8. Greiner S, Schmidt C, Herrmann S, Pauly S, Perka C. Clinical performance of lateralized versus non-lateralized reverse shoulder arthroplasty: a prospective randomized study. J Shoulder Elbow Surg 2015;24:1397-404. http://dx.doi.org/10.1016/j.jse.2015.05.041 9. Gutiérrez S 4th, Comiskey CA, Luo ZP, Pupello DR, Frankle MA. Range of impingement-free abduction and adduction deficit after reverse shoulder arthroplasty. Hierarchy of surgical and implant- design-related factors. J Bone Joint Surg Am 2008;90:2606-15. http://dx.doi.org/10 .2106/JBJS.H.00012 10. Lädermann A, Denard PJ, Boileau P, Farron A, Deransart P, Terrier A, et al. Effect of humeral stem design on humeral position and range of motion in reverse shoulder arthroplasty. Int Orthop 2015;39:2205-13. http://dx.doi.org/10.1007/s00264-015-2984-3 11. Lädermann A, Gueorguiev B, Charbonnier C, Stimec BV, Fasel JH, Zderic I, et al. Scapular notching on kinematic simulated range of motion after reverse shoulder arthroplasty is not the result of impingement in adduction. Medicine (Baltimore) 2015;94:e1615. http://dx.doi.org/10 .1097/MD.0000000000001615 12. Langohr GD, Giles JW, Athwal GS, Johnson JA. The effect of glenosphere diameter in reverse shoulder arthroplasty on muscle force, joint load, and range of motion. J Shoulder Elbow Surg 2015;24:972-9. http://dx.doi.org/10.1016/j.jse.2014.10.018 13. Lévigne C, Boileau P, Favard L, Garaud P, Molé D, Sirveaux F, et al. Scapular notching in reverse shoulder arthroplasty. J Shoulder Elbow Surg 2008;17:925-35. http://dx.doi.org/10.1016/j.jse.2008.02.010 14. Melis B, DeFranco M, Lädermann A, Molé D, Favard L, Nérot C, et al. An evaluation of the radiological changes around the Grammont reverse geometry shoulder arthroplasty after eight to 12 years. J Bone Joint Surg Br 2011;93:1240-6. http://dx.doi.org/10.1302/0301-620X.93B9.25926 15. Moineau G, Levigne C, Boileau P, Young A, Walch G. Threedimensional measurement method of arthritic glenoid cavity morphology: feasibility and reproducibility. Orthop Traumatol Surg Res 2012;98(Suppl):S139-45. http://dx.doi.org/10.1016/j.otsr.2012.06.007 16. 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;14:524-8. http://dx.doi.org/10.1016/ j.jse.2004.09.010 17. Roche C, Flurin PH, Wright T, Crosby LA, Mauldin M, Zuckerman JD. An evaluation of the relationships between reverse shoulder design parameters and range of motion, impingement, and stability. J Shoulder Elbow Surg 2009;18:734-41. http://dx.doi.org/10.1016/j.jse.2008.12.008 18. Sirveaux F, Favard L, Oudet D, Huguet D, Walch G, Mole 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;86:388-95. http://dx.doi.org/10.1302/0301-620X.86B3.14024 19. Tashjian RZ, Burks RT, Zhang Y, Henninger HB. Reverse total shoulder arthroplasty: a biomechanical evaluation of humeral and glenosphere hardware configuration. J Shoulder Elbow Surg 2015;24:e68-77. http://dx.doi.org/10.1016/j.jse.2014.08.017 20. Valenti P, Sauzières P, Katz D, Kalouche I, Kilinc AS. Do less medialized reverse shoulder prostheses increase motion and reduce notching? Clin Orthop Relat Res 2011;469:2550-7. http://dx.doi.org/10.1007/ s11999-011-1844-8 21. Werner CM, Steinmann PA, Gilbart M, Gerber C. Treatment of painful pseudoparesis due to irreparable rotator cuff dysfunction with the Delta III reverse-ball-and-socket total shoulder prosthesis. J Bone Joint Surg Am 2005;87:1476-86. http://dx.doi.org/10.2106/JBJS.D.02342