251 C OPYRIGHT Ó 2015
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T HE J OURNAL
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AND J OINT
S URGERY, I NCORPORATED
Current Concepts Review
Shoulder Arthroplasty in the Presence of Posterior Glenoid Bone Loss Scott P. Stephens, MD, Kevin C. Paisley, DO, Jeffrey Jeng, MPH, Anil K. Dutta, MD, and Michael A. Wirth, MD Investigation performed at the University of Texas Health Science Center at San Antonio, San Antonio, Texas
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Chronic osteoarthritis of the glenohumeral joint, traumatic injury, post-reconstruction arthropathy, and developmental conditions such as glenoid dysplasia can result in posterior glenoid bone loss and excessive retroversion of the glenoid. Shoulder replacement in this setting is technically challenging and characterized by higher rates of complications and revisions.
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Current options that should be considered for managing glenoid bone loss that results in >15° of retroversion include bone-grafting, augmented glenoid components, and reverse total shoulder replacement.
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Asymmetric reaming is commonly used to improve version but should be limited to correction of 10° to 15° of retroversion in order to preserve subchondral bone.
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Bone-grafting of glenoid defects has had mixed results and has been associated with graft-related complications, periprosthetic radiolucencies, and glenoid component failure; however, it provides a biologic option for patients with severe bone loss.
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Implantation of an augmented polyethylene glenoid component offers the potential to improve version while preserving subchondral bone, but the procedure is technically demanding and without clinical follow-up data at this point.
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Reverse total shoulder arthroplasty offers improved fixation and stability compared with an anatomic prosthesis for elderly patients with severe glenoid bone loss but is associated with a high complication rate.
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Glenoid dysplasia is defined as a deformity that results in >25° of glenoid retroversion. Advanced imaging needs to be obtained in order to ensure enough glenoid bone stock is present to allow anatomic glenoid component placement.
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. 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.
Osteoarthritis of the glenohumeral joint is one of the most common indications for shoulder replacement1. This pathology is characterized by loss of articular cartilage, glenoid bone loss,
and increased glenoid retroversion with posterior subluxation of the humeral head in advanced cases2,3. Long-standing osteoarthritis can alter glenoid morphology and potentially affect
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.
J Bone Joint Surg Am. 2015;97:251-9
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surgical planning2-7. Walch et al. reviewed serial computed tomography (CT) scans of 113 patients to evaluate the types of glenoid morphology in primary glenohumeral osteoarthritis and proposed a classification system based on the pattern of glenoid erosion and humeral head subluxation8 (Fig. 1). When conservative treatment has failed, shoulder arthroplasty is a reliable procedure to improve a patient’s function and decrease pain, but the technical aspect of joint replacement increases in complexity with increasing bone loss and posterior glenohumeral subluxation3,9,10. Although total shoulder arthroplasty has demonstrated good long-term survivorship, the predominant cause for revision is glenoid component loosening3,9,11-17. Studies have demonstrated a correlation between glenoid loosening and eccentric loading of the humeral head secondary to rotator cuff deficiency or excessive glenoid retroversion associated with posterior glenoid bone loss17-22. Ho et al. reported that shoulders with glenoid retroversion of >15° have increased odds of developing osteolysis around the central glenoid peg20. Although osteolysis was not found to affect clinical outcomes or reoperation rates at a mean follow-up of 3.8 years, it was associated with early signs of ra-
Fig. 1
Type-A glenoids have a well-centered humeral head and either minor (A1) or major (A2) central erosion. Type-B glenoids have posterior subluxation of the humeral head and either narrowing of the posterior joint space (B1) or asymmetric loading of the posterior glenoid resulting in biconcave morphology (B2). Type-C glenoids have retroversion of >25% regardless of bone loss.
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diographic component loosening. An implant retrieval study demonstrated posteroinferior polyethylene edge deformation in glenoid prostheses implanted in retroversion23. Walch et al. reviewed the results of shoulder arthroplasty in patients with primary osteoarthritis and a biconcave glenoid (i.e., substantial posterior glenoid erosion)24. They reported glenoid loosening in 20.6% and revision rates as high as 16.3% in a series of ninetytwo patients with a mean follow-up of six years. Revisions occurred because of loosening or dislocation in 73.3% (eleven) of fifteen patients. Factors associated with glenoid loosening were increased retroversion (24° versus 17.4°; p = 0.001), glenoid bone loss (9.5 versus 6.4 mm; p = 0.005), humeral head subluxation (80% versus 70.7%; p = 0.01), and postoperative follow-up time. Studies have established that preoperative posterior glenoid erosion is not only a risk factor for glenoid loosening but also results in worse outcomes for function and pain22,24,25. Diminished functional results are even seen with hemiarthroplasty in the presence of glenoid bone loss, indicating the role that concentric glenoid loading plays as a fulcrum for shoulder stability and activities22,26. The severity of glenoid deformity may vary, but the theoretical goal of shoulder arthroplasty is to restore native joint biomechanics by improving glenoid version and maintaining or restoring the glenohumeral joint line. This involves balancing glenoid version correction with preservation of glenoid bone stock. With shoulder replacements expected to increase with an aging population, it is essential to continue to improve implant survival, as well as function, following arthroplasty27. The goal of this article is to highlight and analyze recent studies that have focused on posterior glenoid bone loss during total shoulder arthroplasty. Biomechanics of Glenoid Retroversion and Posterior Bone Loss Glenoid bone loss can have a dramatic effect on shoulder biomechanics. Stability is achieved by dynamic compression of the humeral head into a congruent glenoid concavity28. The loss of posterior glenoid bone can alter joint reactive forces, resulting in humeral head displacement and eccentric stresses placed on the glenoid component. This may lead to polyethylene wear, component loosening, or instability. Loss of posterior glenoid bone results in the net humeral joint reaction forces passing outside the effective glenoid arc, creating joint instability (Fig. 2). Bryce et al. created a cadaveric biomechanical model to study the relationship between glenoid wear and humeral head subluxation29. They demonstrated that subluxation may occur with as little as 2.5° of glenoid retroversion. Glenohumeral forces and humeral head displacement are also directly influenced by the degree of bone loss and glenoid retroversion. Nyffeler et al. found that every 4° increase in retroversion resulted in a 2° shift of joint reactive forces away from the glenoid midline25. The resultant change in force vectors caused approximately 0.5 mm of posterior humeral head displacement for every corresponding degree of glenoid retroversion. Altered joint forces causing humeral head subluxation can result in eccentric loading of the glenoid component, which has been described as a “rocking-horse”
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Fig. 2
The effective glenoid arc is the arc of the glenoid that is able to support the net humeral joint reaction force. The balance stability angle is the maximum angle that the net humeral joint reaction force can make with the glenoid center line before dislocation occurs. The shape of the bone, cartilage, and labrum all contribute to the effective glenoid arc and the stability angle.
mechanism, creating high tensile forces across the glenoid-cementbone interface13,30. Farron et al. used three-dimensional finite element analysis to evaluate torque at the bone-cement interface of implants at various degrees of glenoid retroversion31. They found that retroversion of 20° created a posterior contact point on the glenoid, increasing stresses within the cement mantle and glenoid bone by 326% and 162%, respectively. Retroversion of just 10° resulted in an increase in micromotion at the bone-cement interface of >700%, and they concluded that retroversion beyond this point should be corrected. Shapiro et al. studied the effects of a glenoid component version on joint biomechanics in cadaveric shoulders32. Placing the glenoid implant in 15° of retroversion significantly decreased the glenohumeral contact area, increased contact pressures, and decreased inferior and posterior glenohumeral forces. Treatment Options Eccentric Reaming While eccentric reaming prior to component insertion is commonly used to improve excessive glenoid retroversion, overly aggressive reaming can reduce the subchondral bone available for implant support, medialize the joint line, and allow cortical perforation of the polyethylene implant. In reviewing the loosening patterns of all-polyethylene keeled glenoid components, Walch et al. found that motorized reaming to optimize the position and seating of the component was significantly associated with glenoid loosening for both subsidence and posterior tilt33. They suggested that subchondral bone be preserved to provide
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sufficient osseous support to withstand the stresses experienced by the glenoid implant. Studies have attempted to define the limits of eccentric reaming in order to minimize the removal of subchondral bone while maximizing version correction. Gillespie et al., after simulating posterior glenoid wear in 5° increments on eight cadaveric scapulae, corrected the deformity with eccentric reaming34. Attempting to correct 15° of retroversion resulted in either implant peg penetration or inadequate bone support in four of eight cadaveric specimens. Improving even 10° of version resulted in a significant decrease in anteroposterior glenoid diameter. Clavert et al. created posterior glenoid defects in five cadaveric scapulae and then reamed to neutral version and placed a pegged glenoid component35. Attempting to eccentrically ream 15° of retroversion to neutral resulted in at least one peg perforation in all five cadaveric specimens and one fracture of the anterior glenoid rim. They concluded that, if version exceeds 15°, the surgeon should consider alternatives to reaming the anterior aspect of the glenoid, such as posterior deficiency bone-grafting. Computer software has allowed investigators to simulate the effect that reaming has on glenoid component implantation. Iannotti et al. compared ideal versus actual retroversion correction in thirteen patients who had placement of the primary total shoulder prosthesis with the use of a three-dimensional surgical simulator36. They found that all five patients with retroversion of >19° would have had central peg perforation if ideal component placement had occurred. Nowak et al. used three-dimensional models created from nineteen patients with advanced osteoarthritis to predict how effective reaming could improve version37. They reported that glenoid surfaces with 18° resulted in peg penetration. Although peg perforation can potentially result in cement protrusion and diminished fixation, pegged glenoid perforation after a short-term follow-up period does not appear to have adverse effects on clinical or radiographic outcomes. Additional long-term studies will be needed to determine the effect, if any, of peg perforation38. There are few clinical studies evaluating the results of eccentric reaming. Habermeyer et al. evaluated seventy-seven patients undergoing primary total shoulder arthroplasty to determine if static posterior subluxation with posterior glenoid wear could be recentered by eccentric reaming39. In eight patients, bone-grafting was performed in addition to reaming because of a massive glenoid deformity. Of the seventy-seven patients, forty-nine (64%) had preoperative posterior glenoid wear and twenty-two (45%) of the forty-nine patients had posterior subluxation of the humeral head. On postoperative radiographs, no posterior subluxation was observed and fortytwo (86%) of the forty-nine humeral heads were centered, with the remainder being anterior to the center line. Functionally, patients with preoperative concentric wear demonstrated improved Constant-Murley scores compared with patients with eccentric glenoid wear39. In a study of thirty-three patients with static preoperative posterior humeral head subluxation who were managed with primary total shoulder arthroplasty and followed for a minimum of two years, Gerber et al. determined that
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version correction through reaming recentered the humeral head40. The preoperative subluxation index averaged 71%, and the mean preoperative glenoid retroversion was 18°. Corrective glenoid reaming with a cannulated system was used to restore version to within 0° to 10° without attempting >15° of correction. Subluxation was reversed in twenty-one patients at the time of the final follow-up, from a mean subluxation index of 71% to 50%. Glenoid retroversion was corrected to a mean of 9° and was 15° of retroversion4,41,42. Concerns with bone-grafting include nonunion, resorption, or subsidence, in addition to the technical demand of graft placement and fixation41,43-49. Few studies have evaluated the outcomes of glenoid bonegrafting for shoulder arthroplasty (Table I). Neer and Morrison reviewed the cases of nineteen patients with a mean follow-up of fifty-two months50. They reported that sixteen patients had excellent results. Two fixation screws broke, but none of the glenoid components loosened. Steinmann and Cofield reported on twenty-eight patients with a mean duration of follow-up of 5.3 years51. Twenty-three patients had either excellent or satisfactory results, while five patients were unsatisfied because of symptomatic glenoid loosening, instability, or persistent pain. Radiographically, three (11%) of the twenty-eight glenoids had become loose, although all glenoid bone grafts had apparently healed. Hill and Norris reported on seventeen shoulder arthroplasties that required grafting to address either anterior or posterior insufficient glenoid bone stock resulting from a variety of etiologies and prior surgeries41. All were considered to have instability. The mean version improved to 4° of retroversion, with a mean 33% of correction from preoperative version. They reported that the results were excellent for three patients, satisfactory for six, and unsatisfactory for eight. Three patients developed graft-related problems, including nonunion and loss of fixation. Five patients required revision surgery for glenoid failure. In a series of seventy-five patients with a biconcave glen-
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oid described by Walch et al., seven required structural bonegrafting because of the inability to correct retroversion to 20°42. The mean preoperative retroversion was 44°, and the mean glenoid bone loss was 15.2 mm. Their technique differed from other bone-grafting techniques in that the bone graft had a trapezoidal shape and was incorporated into a step-cut glenoid with posterior screw fixation. At the mean 4.4-year follow-up evaluation, ten patients had graft incorporation. Two patients had failure of graft incorporation and required revision surgery, and one of them was found to have an infection. Ten patients had good or excellent results. The clinical results for glenoid bone-grafting are mixed and have been associated with a high percentage of periprosthetic radiolucencies, glenoid component failure, graft complications, and instability53. These reports can be difficult to compare because of various grafting techniques, implants, and confounding patient variables. Augmented Glenoid Components Augmented glenoid components were designed as an alternative to eccentric reaming and bone-grafting to compensate for posterior glenoid bone loss. Rice et al. reviewed fourteen shoulders treated with an asymmetric wedge-shaped posteriorly augmented glenoid component with a mean follow-up of five years54. Functionally, five patients had excellent results, seven had satisfactory results, and two had unsatisfactory results. More than half of the glenoid components demonstrated radiolucent lines, and one-third demonstrated moderate or severe posterior glenohumeral subluxation, although no shoulder required revision surgery. Rice et al. concluded that the contribution of the modified glenoid component to overall correction of glenoid bone wear and humeral subluxation seemed marginal, and use of this implant was discontinued. The design of the augmentation, however, can have a substantial effect on the forces transferred to the implant. The development of a stepped, posteriorly augmented glenoid
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Fig. 3-A
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Fig. 3-B
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Fig. 3-A through 3-E The left shoulder of a patient with advanced osteoarthritic changes and a biconcave glenoid that was treated with a stepped augmented glenoid component. Fig. 3-A Preoperative axillary radiograph. Fig. 3-B Preoperative axial CT scan of the biconcave glenoid with approxi70
mately 5.5 mm of posterior glenoid bone loss and associated humeral head subluxation as measured with the technique described by Sabesan et al. . 4
The glenoid was in 17° of retroversion as measured using the technique described by Friedman et al. . This measurement is determined by placing a line between the anterior and posterior margins of the glenoid, excluding osteophytes. The transverse axis of the scapula is identified by placing a line from the medial aspect of the scapula through the glenoid fossa midpoint. The angle formed between these two lines defines the glenoid 4 71 version . The variability in this technique was found to be a mean (and standard deviation) of 5.1° ± 9.8° for two-dimensional CT scans . Fig. 3-C Postoperative axillary radiograph demonstrating improvement of version to 2° of retroversion and improved subluxation with placement of an augmented glenoid component (Global Steptech; DePuy, Warsaw, Indiana).
design places the component perpendicular to the vector of joint forces and allows for improved biomechanical properties55-57 (Figs. 3-A through 3-E). Iannotti et al. performed a biomechanical study of four different all-polyethylene augmentation designs, under both compressive and eccentric loads, to compare their resistance to anterior glenoid liftoff 57. The stepped glenoid was found to have lower initial and final liftoff values compared with the augmentation designs, although not all reached significance. They also found that the stepped glenoid was the only augmented device that was comparable with a standard glenoid
for final simulated long-term fixation. Sabesan et al. utilized computer models of twenty-nine patients with mean retroversion of 20.9° and mean bone loss of 4.8 mm to compare the use of stepped augmented glenoid components and standard glenoid components55. They demonstrated significantly less joint line medialization when they attempted to correct to both neutral (mean, 8.3 mm versus 3.8 mm) and 6° of retroversion (mean, 7.2 mm versus 3.36 mm). The augmented glenoid also provided up to 18° more version correction when the amount of bone removal was held constant. Five shoulders,
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Fig. 3-E
Fig. 3-D The stepped glenoid component with 3 mm of glenoid augmentation (Global Steptech). Fig. 3-E The prepared glenoid with a posterior step-cut (small arrowheads) and prepared central and peripheral peg holes is shown, with the axillary nerve indicated by the large arrow.
four of which had the standard glenoid component, had central peg perforation. Those authors concluded that augmentation or bone-grafting is necessary when there is glenoid retroversion of ‡16°. Glenoid implant augmentation can improve glenoid version while preventing implant perforation, joint line medialization, and subchondral bone loss, but clinical studies are lacking. Augmented glenoid implantation is a technically demanding procedure that requires precise creation of a glenoid bone bed to seat the augmented component. The inability to provide adequate seating of the posterior augment may predispose the implant to micromotion and the risk of loosening13,58,59. It is also still unclear whether augmented glenoid components improve posterior humeral subluxation, which if uncorrected may result in an increased risk of cold flow glenoid polyethylene deformation from mechanical forces13,23. Augmentation can be considered when retroversion is >15°, with the goal of correcting glenoid retroversion to 6°55. Future studies with long-term follow-up are needed to determine the effect of component augmentation on outcomes and implant survival. Reverse Total Shoulder Arthroplasty for Osteoarthritis with Bone Loss Rotator cuff tears can alter glenohumeral mechanics and predispose the glenoid to abnormal wear patterns60. Mizuno et al. reviewed twenty-seven reverse shoulder replacements performed for the treatment of primary glenohumeral osteoarthritis with a
biconcave glenoid with functional rotator cuffs61. Their indications included a patient age of greater than seventy years and retroversion and humeral head subluxation that was believed to be unreliably corrected by asymmetric reaming. The mean preoperative retroversion was 32°, and humeral head subluxation was 87%. Ten patients required a bone graft if version could not be corrected to within 10° of neutral or when the baseplate surface contact was 25° of retroversion regardless of bone loss as a type-C deformity8. This glenoid is distinguished from a Walch type-B2 glenoid by the lack of humeral head subluxation due to hypertrophy of posterior soft-tissue structures that have adapted to the altered morphology. Severe hypoplasia compromises the glenoid vault and may prevent placement of a glenoid implant; the results of hemiarthoplasty alone have been mixed67,68. Edwards et al. evaluated fifteen patients with dysplastic glenoids at a mean of thirty-seven months in a multicenter
Functional Outcome
Radiographic Outcome
Complications
study consisting of eleven total shoulder arthroplasties and four hemiarthroplasties69. The glenoid was replaced if ‡15 mm of glenoid bone stock was present on preoperative CT scans. Correction of version was not attempted as there was no humeral head subluxation. Subjectively, nine shoulders were rated as excellent, four as good, and one as fair. One glenoid component became loose and was removed. Postoperative mobility scores were reported to be better with glenoid resurfacing (mean, 36 versus 22.7; p = 0.011), but no difference was found for other parameters evaluated. Those authors recommended resurfacing the glenoid if bone stock is sufficient. Allen et al. reported on twenty-two dysplastic shoulders, fourteen of which were treated with total shoulder arthroplasty58. The mean duration of follow-up was six years. The decision to perform a hemiarthroplasty was based on the patient’s age and amount of bone loss. Pain was relieved in four of eight shoulders after hemiarthroplasty and in ten of fourteen shoulders after total shoulder arthroplasty; motion improvements were similar for both cohorts. Four shoulders that had a hemiarthroplasty were revised to total shoulder arthroplasty because of pain. Two total shoulder replacements were revised because of infections,
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and three underwent revisions for glenoid problems. The only unsatisfactory results for glenoid resurfacing were in patients who required revision surgery. Radiographically, greater than mild humeral head subluxation was seen in six shoulders that had a hemiarthroplasty but in only three that had a total shoulder arthroplasty. They concluded that total shoulder arthroplasty was more consistent in gaining pain relief and controlling humeral subluxation. Favorable results can be obtained with arthroplasty to treat glenohumeral arthritis related to a dysplastic glenoid. Advanced imaging, including three-dimensional imaging, should be done prior to surgical treatment and used to determine if enough glenoid bone is available to allow placement of a glenoid component. Overview Chronic glenohumeral arthritis, traumatic injury, postreconstruction arthropathy, and developmental conditions such as glenoid dysplasia can result in posterior glenoid bone erosion and alteration of joint reactive forces. Surgical management should attempt to restore glenoid version in order to minimize off-center loads applied to the glenoid implant and improve implant survival. The literature pertaining to the management of glenoid bone loss consists mainly of biomechanical studies and Level-IV case series but is limited with respect to guidelines for surgical options.
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Glenoid deformity that results in 10° to 15° of glenoid retroversion can be effectively managed with eccentric reaming. When bone loss results in retroversion that exceeds 15°, then correction necessitates using either bone-grafting or augmented implants. A reverse shoulder prosthesis offers another surgical option in elderly, sedentary patients. Posterior glenoid bone loss can affect implant longevity and clinical outcomes, and patients should be counseled on the potential risks associated with treating this condition. n
Scott P. Stephens, MD Fondren Orthopedic Group, 601 Rockmead Drive, Kingwood, TX 77339. E-mail address: [email protected] Kevin C. Paisley, DO Jeffrey Jeng, MPH Anil K. Dutta, MD Michael A. Wirth, MD Department of Orthopaedics, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MSC 7774, San Antonio, TX 78229-3900.
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29. Bryce CD, Davison AC, Okita N, Lewis GS, Sharkey NA, Armstrong AD. A biomechanical study of posterior glenoid bone loss and humeral head translation. J Shoulder Elbow Surg. 2010 Oct;19(7):994-1002. Epub 2010 Jul 24. 30. Collins D, Tencer A, Sidles J, Matsen F 3rd. Edge displacement and deformation of glenoid components in response to eccentric loading. The effect of preparation of the glenoid bone. J Bone Joint Surg Am. 1992 Apr;74(4):501-7. 31. Farron A, Terrier A, B¨uchler P. Risks of loosening of a prosthetic glenoid implanted in retroversion. J Shoulder Elbow Surg. 2006 Jul-Aug;15(4):521-6. 32. Shapiro TA, McGarry MH, Gupta R, Lee YS, Lee TQ. Biomechanical effects of glenoid retroversion in total shoulder arthroplasty. J Shoulder Elbow Surg. 2007 May-Jun;16(3)(Suppl):S90-5. Epub 2006 Dec 12. 33. Walch G, Young AA, Boileau P, Loew M, Gazielly D, Mol´e D. Patterns of loosening of polyethylene keeled glenoid components after shoulder arthroplasty for primary osteoarthritis: results of a multicenter study with more than five years of follow-up. J Bone Joint Surg Am. 2012 Jan 18;94(2):145-50. 34. Gillespie R, Lyons R, Lazarus M. Eccentric reaming in total shoulder arthroplasty: a cadaveric study. Orthopedics. 2009 Jan;32(1):21. 35. Clavert P, Millett PJ, Warner JJ. Glenoid resurfacing: what are the limits to asymmetric reaming for posterior erosion? J Shoulder Elbow Surg. 2007 Nov-Dec; 16(6):843-8. 36. Iannotti JP, Greeson C, Downing D, Sabesan V, Bryan JA. Effect of glenoid deformity on glenoid component placement in primary shoulder arthroplasty. J Shoulder Elbow Surg. 2012 Jan;21(1):48-55. Epub 2011 May 20. 37. Nowak DD, Bahu MJ, Gardner TR, Dyrszka MD, Levine WN, Bigliani LU, Ahmad CS. Simulation of surgical glenoid resurfacing using three-dimensional computed tomography of the arthritic glenohumeral joint: the amount of glenoid retroversion that can be corrected. J Shoulder Elbow Surg. 2009 Sep-Oct;18(5):680-8. Epub 2009 May 31. 38. Press CM, O’Connor DP, Elkousy HA, Gartsman GM, Edwards TB. Glenoid perforation does not affect the short-term outcomes of pegged all-polyethylene implants in total shoulder arthroplasty. J Shoulder Elbow Surg. 2014 Aug;23(8):1203-7. Epub 2014 Feb 20. 39. Habermeyer P, Magosch P, Lichtenberg S. Recentering the humeral head for glenoid deficiency in total shoulder arthroplasty. Clin Orthop Relat Res. 2007 Apr;457(457):124-32. 40. Gerber C, Costouros JG, Sukthankar A, Fucentese SF. Static posterior humeral head subluxation and total shoulder arthroplasty. J Shoulder Elbow Surg. 2009 Jul-Aug;18(4):505-10. Epub 2009 May 29. 41. Hill JM, Norris TR. Long-term results of total shoulder arthroplasty following bone-grafting of the glenoid. J Bone Joint Surg Am. 2001 Jun;83(6):877-83. 42. Sabesan V, Callanan M, Ho J, Iannotti JP. Clinical and radiographic outcomes of total shoulder arthroplasty with bone graft for osteoarthritis with severe glenoid bone loss. J Bone Joint Surg Am. 2013 Jul 17;95(14):1290-6. 43. Friedman RJ, Hawthorne KB, Genez BM. Glenoid augmentation for total shoulder arthroplasty. Orthop Trans. 1992;16:66. 44. Cheung EV, Sperling JW, Cofield RH. Reimplantation of a glenoid component following component removal and allogenic bone-grafting. J Bone Joint Surg Am. 2007 Aug;89(8):1777-83. 45. Phipatanakul WP, Norris TR. Treatment of glenoid loosening and bone loss due to osteolysis with glenoid bone grafting. J Shoulder Elbow Surg. 2006 Jan-Feb;15(1): 84-7. 46. Neyton L, Walch G, Nov´e-Josserand L, Edwards TB. Glenoid corticocancellous bone grafting after glenoid component removal in the treatment of glenoid loosening. J Shoulder Elbow Surg. 2006 Mar-Apr;15(2):173-9. 47. Frankle MA, Long RA. Glenoid component failure treated with a allograft for revision total surgery. Presented at the 18th Annual Meeting of the American Shoulder and Elbow Surgeons; October 24-27, 2001; Napa, California. 48. Scalise JJ, Iannotti JP. Bone grafting severe glenoid defects in revision shoulder arthroplasty. Clin Orthop Relat Res. 2008 Jan;466(1):139-45. Epub 2008 Jan 3. 49. Iannotti JP, Frangiamore SJ. Fate of large structural allograft for treatment of severe uncontained glenoid bone deficiency. J Shoulder Elbow Surg. 2012 Jun; 21(6):765-71. Epub 2012 Feb 3.
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50. Neer CS 2nd, Morrison DS. Glenoid bone-grafting in total shoulder arthroplasty. J Bone Joint Surg Am. 1988 Sep;70(8):1154-62. 51. Steinmann SP, Cofield RH. Bone grafting for glenoid deficiency in total shoulder replacement. J Shoulder Elbow Surg. 2000 Sep-Oct;9(5):361-7. 52. Klika BJ, Wooten CW, Sperling JW, Steinmann SP, Schleck CD, Harmsen WS, Cofield RH. Structural bone grafting for glenoid deficiency in primary total shoulder arthroplasty. J Shoulder Elbow Surg. 2014 Jul;23(7):1066-72. Epub 2013 Dec 14. 53. Sears BW, Johnston PS, Ramsey ML, Williams GR. Glenoid bone loss in primary total shoulder arthroplasty: evaluation and management. J Am Acad Orthop Surg. 2012 Sep;20(9):604-13. 54. Rice RS, Sperling JW, Miletti J, Schleck C, Cofield RH. Augmented glenoid component for bone deficiency in shoulder arthroplasty. Clin Orthop Relat Res. 2008 Mar;466(3):579-83. Epub 2008 Jan 8. 55. Sabesan V, Callanan M, Sharma V, Iannotti JP. Correction of acquired glenoid bone loss in osteoarthritis with a standard versus an augmented glenoid component. J Shoulder Elbow Surg. 2014 Jul;23(7):964-73. Epub 2014 Jan 7. 56. Kirane YM, Lewis GS, Sharkey NA, Armstrong AD. Mechanical characteristics of a novel posterior-step prosthesis for biconcave glenoid defects. J Shoulder Elbow Surg. 2012 Jan;21(1):105-15. Epub 2011 Mar 21. 57. Iannotti JP, Lappin KE, Klotz CL, Reber EW, Swope SW. Liftoff resistance of augmented glenoid components during cyclic fatigue loading in the posterior-superior direction. J Shoulder Elbow Surg. 2013 Nov;22(11):1530-6. Epub 2013 Mar 22. 58. Allen B, Schoch B, Sperling JW, Cofield RH. Shoulder arthroplasty for osteoarthritis secondary to glenoid dysplasia: an update. J Shoulder Elbow Surg. 2014 Feb;23(2):214-20. Epub 2013 Aug 9. 59. Collins D, Tencer A, Sidles J, Matsen F 3rd. Edge displacement and deformation of glenoid components in response to eccentric loading. The effect of preparation of the glenoid bone. J Bone Joint Surg Am. 1992 Apr;74(4):501-7. 60. Frankle MA, Teramoto A, Luo ZP, Levy JC, Pupello D. Glenoid morphology in reverse shoulder arthroplasty: classification and surgical implications. J Shoulder Elbow Surg. 2009 Nov-Dec;18(6):874-85. Epub 2009 May 30. 61. Mizuno N, Denard PJ, Raiss P, Walch G. Reverse total shoulder arthroplasty for primary glenohumeral osteoarthritis in patients with a biconcave glenoid. J Bone Joint Surg Am. 2013 Jul 17;95(14):1297-304. 62. 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. 63. Currarino G, Sheffield E, Twickler D. Congenital glenoid dysplasia. Pediatr Radiol. 1998 Jan;28(1):30-7. 64. Harper KW, Helms CA, Haystead CM, Higgins LD. Glenoid dysplasia: incidence and association with posterior labral tears as evaluated on MRI. AJR Am J Roentgenol. 2005 Mar;184(3):984-8. 65. Wirth MA, Lyons FR, Rockwood CA Jr. Hypoplasia of the glenoid. A review of sixteen patients. J Bone Joint Surg Am. 1993 Aug;75(8):1175-84. 66. Smith SP, Bunker TD. Primary glenoid dysplasia. A review of 12 patients. J Bone Joint Surg Br. 2001 Aug;83(6):868-72. 67. Sperling JW, Cofield RH, Steinmann SP. Shoulder arthroplasty for osteoarthritis secondary to glenoid dysplasia. J Bone Joint Surg Am. 2002 Apr;84(4):541-6. 68. Bonnevialle N, Mansat P, Mansat M, Bonnevialle P. Hemiarthroplasty for osteoarthritis in shoulder with dysplastic morphology. J Shoulder Elbow Surg. 2011 Apr;20(3):378-84. Epub 2010 Nov 3. 69. Edwards TB, Boulahia A, Kempf JF, Boileau P, N´emoz C, Walch G. Shoulder arthroplasty in patients with osteoarthritis and dysplastic glenoid morphology. J Shoulder Elbow Surg. 2004 Jan-Feb;13(1):1-4. 70. Sabesan VJ, Callanan M, Youderian A, Iannotti JP. 3D CT assessment of the relationship between humeral head alignment and glenoid retroversion in glenohumeral osteoarthritis. J Bone Joint Surg Am. 2014 Apr 16;96(8):e64. 71. Hoenecke HR Jr, Hermida JC, Flores-Hernandez C, D’Lima DD. Accuracy of CTbased measurements of glenoid version for total shoulder arthroplasty. J Shoulder Elbow Surg. 2010 Mar;19(2):166-71. Epub 2009 Dec 2.
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Current Concepts Review
Shoulder Arthroplasty in the Presence of Posterior Glenoid Bone Loss Scott P. Stephens, MD, Kevin C. Paisley, DO, Jeffrey Jeng, MPH, Anil K. Dutta, MD, and Michael A. Wirth, MD Investigation performed at the University of Texas Health Science Center at San Antonio, San Antonio, Texas
ä
Chronic osteoarthritis of the glenohumeral joint, traumatic injury, post-reconstruction arthropathy, and developmental conditions such as glenoid dysplasia can result in posterior glenoid bone loss and excessive retroversion of the glenoid. Shoulder replacement in this setting is technically challenging and characterized by higher rates of complications and revisions.
ä
Current options that should be considered for managing glenoid bone loss that results in >15° of retroversion include bone-grafting, augmented glenoid components, and reverse total shoulder replacement.
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Asymmetric reaming is commonly used to improve version but should be limited to correction of 10° to 15° of retroversion in order to preserve subchondral bone.
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Bone-grafting of glenoid defects has had mixed results and has been associated with graft-related complications, periprosthetic radiolucencies, and glenoid component failure; however, it provides a biologic option for patients with severe bone loss.
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Implantation of an augmented polyethylene glenoid component offers the potential to improve version while preserving subchondral bone, but the procedure is technically demanding and without clinical follow-up data at this point.
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Reverse total shoulder arthroplasty offers improved fixation and stability compared with an anatomic prosthesis for elderly patients with severe glenoid bone loss but is associated with a high complication rate.
ä
Glenoid dysplasia is defined as a deformity that results in >25° of glenoid retroversion. Advanced imaging needs to be obtained in order to ensure enough glenoid bone stock is present to allow anatomic glenoid component placement.
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. 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.
Osteoarthritis of the glenohumeral joint is one of the most common indications for shoulder replacement1. This pathology is characterized by loss of articular cartilage, glenoid bone loss,
and increased glenoid retroversion with posterior subluxation of the humeral head in advanced cases2,3. Long-standing osteoarthritis can alter glenoid morphology and potentially affect
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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surgical planning2-7. Walch et al. reviewed serial computed tomography (CT) scans of 113 patients to evaluate the types of glenoid morphology in primary glenohumeral osteoarthritis and proposed a classification system based on the pattern of glenoid erosion and humeral head subluxation8 (Fig. 1). When conservative treatment has failed, shoulder arthroplasty is a reliable procedure to improve a patient’s function and decrease pain, but the technical aspect of joint replacement increases in complexity with increasing bone loss and posterior glenohumeral subluxation3,9,10. Although total shoulder arthroplasty has demonstrated good long-term survivorship, the predominant cause for revision is glenoid component loosening3,9,11-17. Studies have demonstrated a correlation between glenoid loosening and eccentric loading of the humeral head secondary to rotator cuff deficiency or excessive glenoid retroversion associated with posterior glenoid bone loss17-22. Ho et al. reported that shoulders with glenoid retroversion of >15° have increased odds of developing osteolysis around the central glenoid peg20. Although osteolysis was not found to affect clinical outcomes or reoperation rates at a mean follow-up of 3.8 years, it was associated with early signs of ra-
Fig. 1
Type-A glenoids have a well-centered humeral head and either minor (A1) or major (A2) central erosion. Type-B glenoids have posterior subluxation of the humeral head and either narrowing of the posterior joint space (B1) or asymmetric loading of the posterior glenoid resulting in biconcave morphology (B2). Type-C glenoids have retroversion of >25% regardless of bone loss.
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diographic component loosening. An implant retrieval study demonstrated posteroinferior polyethylene edge deformation in glenoid prostheses implanted in retroversion23. Walch et al. reviewed the results of shoulder arthroplasty in patients with primary osteoarthritis and a biconcave glenoid (i.e., substantial posterior glenoid erosion)24. They reported glenoid loosening in 20.6% and revision rates as high as 16.3% in a series of ninetytwo patients with a mean follow-up of six years. Revisions occurred because of loosening or dislocation in 73.3% (eleven) of fifteen patients. Factors associated with glenoid loosening were increased retroversion (24° versus 17.4°; p = 0.001), glenoid bone loss (9.5 versus 6.4 mm; p = 0.005), humeral head subluxation (80% versus 70.7%; p = 0.01), and postoperative follow-up time. Studies have established that preoperative posterior glenoid erosion is not only a risk factor for glenoid loosening but also results in worse outcomes for function and pain22,24,25. Diminished functional results are even seen with hemiarthroplasty in the presence of glenoid bone loss, indicating the role that concentric glenoid loading plays as a fulcrum for shoulder stability and activities22,26. The severity of glenoid deformity may vary, but the theoretical goal of shoulder arthroplasty is to restore native joint biomechanics by improving glenoid version and maintaining or restoring the glenohumeral joint line. This involves balancing glenoid version correction with preservation of glenoid bone stock. With shoulder replacements expected to increase with an aging population, it is essential to continue to improve implant survival, as well as function, following arthroplasty27. The goal of this article is to highlight and analyze recent studies that have focused on posterior glenoid bone loss during total shoulder arthroplasty. Biomechanics of Glenoid Retroversion and Posterior Bone Loss Glenoid bone loss can have a dramatic effect on shoulder biomechanics. Stability is achieved by dynamic compression of the humeral head into a congruent glenoid concavity28. The loss of posterior glenoid bone can alter joint reactive forces, resulting in humeral head displacement and eccentric stresses placed on the glenoid component. This may lead to polyethylene wear, component loosening, or instability. Loss of posterior glenoid bone results in the net humeral joint reaction forces passing outside the effective glenoid arc, creating joint instability (Fig. 2). Bryce et al. created a cadaveric biomechanical model to study the relationship between glenoid wear and humeral head subluxation29. They demonstrated that subluxation may occur with as little as 2.5° of glenoid retroversion. Glenohumeral forces and humeral head displacement are also directly influenced by the degree of bone loss and glenoid retroversion. Nyffeler et al. found that every 4° increase in retroversion resulted in a 2° shift of joint reactive forces away from the glenoid midline25. The resultant change in force vectors caused approximately 0.5 mm of posterior humeral head displacement for every corresponding degree of glenoid retroversion. Altered joint forces causing humeral head subluxation can result in eccentric loading of the glenoid component, which has been described as a “rocking-horse”
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The effective glenoid arc is the arc of the glenoid that is able to support the net humeral joint reaction force. The balance stability angle is the maximum angle that the net humeral joint reaction force can make with the glenoid center line before dislocation occurs. The shape of the bone, cartilage, and labrum all contribute to the effective glenoid arc and the stability angle.
mechanism, creating high tensile forces across the glenoid-cementbone interface13,30. Farron et al. used three-dimensional finite element analysis to evaluate torque at the bone-cement interface of implants at various degrees of glenoid retroversion31. They found that retroversion of 20° created a posterior contact point on the glenoid, increasing stresses within the cement mantle and glenoid bone by 326% and 162%, respectively. Retroversion of just 10° resulted in an increase in micromotion at the bone-cement interface of >700%, and they concluded that retroversion beyond this point should be corrected. Shapiro et al. studied the effects of a glenoid component version on joint biomechanics in cadaveric shoulders32. Placing the glenoid implant in 15° of retroversion significantly decreased the glenohumeral contact area, increased contact pressures, and decreased inferior and posterior glenohumeral forces. Treatment Options Eccentric Reaming While eccentric reaming prior to component insertion is commonly used to improve excessive glenoid retroversion, overly aggressive reaming can reduce the subchondral bone available for implant support, medialize the joint line, and allow cortical perforation of the polyethylene implant. In reviewing the loosening patterns of all-polyethylene keeled glenoid components, Walch et al. found that motorized reaming to optimize the position and seating of the component was significantly associated with glenoid loosening for both subsidence and posterior tilt33. They suggested that subchondral bone be preserved to provide
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sufficient osseous support to withstand the stresses experienced by the glenoid implant. Studies have attempted to define the limits of eccentric reaming in order to minimize the removal of subchondral bone while maximizing version correction. Gillespie et al., after simulating posterior glenoid wear in 5° increments on eight cadaveric scapulae, corrected the deformity with eccentric reaming34. Attempting to correct 15° of retroversion resulted in either implant peg penetration or inadequate bone support in four of eight cadaveric specimens. Improving even 10° of version resulted in a significant decrease in anteroposterior glenoid diameter. Clavert et al. created posterior glenoid defects in five cadaveric scapulae and then reamed to neutral version and placed a pegged glenoid component35. Attempting to eccentrically ream 15° of retroversion to neutral resulted in at least one peg perforation in all five cadaveric specimens and one fracture of the anterior glenoid rim. They concluded that, if version exceeds 15°, the surgeon should consider alternatives to reaming the anterior aspect of the glenoid, such as posterior deficiency bone-grafting. Computer software has allowed investigators to simulate the effect that reaming has on glenoid component implantation. Iannotti et al. compared ideal versus actual retroversion correction in thirteen patients who had placement of the primary total shoulder prosthesis with the use of a three-dimensional surgical simulator36. They found that all five patients with retroversion of >19° would have had central peg perforation if ideal component placement had occurred. Nowak et al. used three-dimensional models created from nineteen patients with advanced osteoarthritis to predict how effective reaming could improve version37. They reported that glenoid surfaces with 18° resulted in peg penetration. Although peg perforation can potentially result in cement protrusion and diminished fixation, pegged glenoid perforation after a short-term follow-up period does not appear to have adverse effects on clinical or radiographic outcomes. Additional long-term studies will be needed to determine the effect, if any, of peg perforation38. There are few clinical studies evaluating the results of eccentric reaming. Habermeyer et al. evaluated seventy-seven patients undergoing primary total shoulder arthroplasty to determine if static posterior subluxation with posterior glenoid wear could be recentered by eccentric reaming39. In eight patients, bone-grafting was performed in addition to reaming because of a massive glenoid deformity. Of the seventy-seven patients, forty-nine (64%) had preoperative posterior glenoid wear and twenty-two (45%) of the forty-nine patients had posterior subluxation of the humeral head. On postoperative radiographs, no posterior subluxation was observed and fortytwo (86%) of the forty-nine humeral heads were centered, with the remainder being anterior to the center line. Functionally, patients with preoperative concentric wear demonstrated improved Constant-Murley scores compared with patients with eccentric glenoid wear39. In a study of thirty-three patients with static preoperative posterior humeral head subluxation who were managed with primary total shoulder arthroplasty and followed for a minimum of two years, Gerber et al. determined that
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version correction through reaming recentered the humeral head40. The preoperative subluxation index averaged 71%, and the mean preoperative glenoid retroversion was 18°. Corrective glenoid reaming with a cannulated system was used to restore version to within 0° to 10° without attempting >15° of correction. Subluxation was reversed in twenty-one patients at the time of the final follow-up, from a mean subluxation index of 71% to 50%. Glenoid retroversion was corrected to a mean of 9° and was 15° of retroversion4,41,42. Concerns with bone-grafting include nonunion, resorption, or subsidence, in addition to the technical demand of graft placement and fixation41,43-49. Few studies have evaluated the outcomes of glenoid bonegrafting for shoulder arthroplasty (Table I). Neer and Morrison reviewed the cases of nineteen patients with a mean follow-up of fifty-two months50. They reported that sixteen patients had excellent results. Two fixation screws broke, but none of the glenoid components loosened. Steinmann and Cofield reported on twenty-eight patients with a mean duration of follow-up of 5.3 years51. Twenty-three patients had either excellent or satisfactory results, while five patients were unsatisfied because of symptomatic glenoid loosening, instability, or persistent pain. Radiographically, three (11%) of the twenty-eight glenoids had become loose, although all glenoid bone grafts had apparently healed. Hill and Norris reported on seventeen shoulder arthroplasties that required grafting to address either anterior or posterior insufficient glenoid bone stock resulting from a variety of etiologies and prior surgeries41. All were considered to have instability. The mean version improved to 4° of retroversion, with a mean 33% of correction from preoperative version. They reported that the results were excellent for three patients, satisfactory for six, and unsatisfactory for eight. Three patients developed graft-related problems, including nonunion and loss of fixation. Five patients required revision surgery for glenoid failure. In a series of seventy-five patients with a biconcave glen-
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oid described by Walch et al., seven required structural bonegrafting because of the inability to correct retroversion to 20°42. The mean preoperative retroversion was 44°, and the mean glenoid bone loss was 15.2 mm. Their technique differed from other bone-grafting techniques in that the bone graft had a trapezoidal shape and was incorporated into a step-cut glenoid with posterior screw fixation. At the mean 4.4-year follow-up evaluation, ten patients had graft incorporation. Two patients had failure of graft incorporation and required revision surgery, and one of them was found to have an infection. Ten patients had good or excellent results. The clinical results for glenoid bone-grafting are mixed and have been associated with a high percentage of periprosthetic radiolucencies, glenoid component failure, graft complications, and instability53. These reports can be difficult to compare because of various grafting techniques, implants, and confounding patient variables. Augmented Glenoid Components Augmented glenoid components were designed as an alternative to eccentric reaming and bone-grafting to compensate for posterior glenoid bone loss. Rice et al. reviewed fourteen shoulders treated with an asymmetric wedge-shaped posteriorly augmented glenoid component with a mean follow-up of five years54. Functionally, five patients had excellent results, seven had satisfactory results, and two had unsatisfactory results. More than half of the glenoid components demonstrated radiolucent lines, and one-third demonstrated moderate or severe posterior glenohumeral subluxation, although no shoulder required revision surgery. Rice et al. concluded that the contribution of the modified glenoid component to overall correction of glenoid bone wear and humeral subluxation seemed marginal, and use of this implant was discontinued. The design of the augmentation, however, can have a substantial effect on the forces transferred to the implant. The development of a stepped, posteriorly augmented glenoid
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Fig. 3-A
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Fig. 3-B
Fig. 3-C
Fig. 3-A through 3-E The left shoulder of a patient with advanced osteoarthritic changes and a biconcave glenoid that was treated with a stepped augmented glenoid component. Fig. 3-A Preoperative axillary radiograph. Fig. 3-B Preoperative axial CT scan of the biconcave glenoid with approxi70
mately 5.5 mm of posterior glenoid bone loss and associated humeral head subluxation as measured with the technique described by Sabesan et al. . 4
The glenoid was in 17° of retroversion as measured using the technique described by Friedman et al. . This measurement is determined by placing a line between the anterior and posterior margins of the glenoid, excluding osteophytes. The transverse axis of the scapula is identified by placing a line from the medial aspect of the scapula through the glenoid fossa midpoint. The angle formed between these two lines defines the glenoid 4 71 version . The variability in this technique was found to be a mean (and standard deviation) of 5.1° ± 9.8° for two-dimensional CT scans . Fig. 3-C Postoperative axillary radiograph demonstrating improvement of version to 2° of retroversion and improved subluxation with placement of an augmented glenoid component (Global Steptech; DePuy, Warsaw, Indiana).
design places the component perpendicular to the vector of joint forces and allows for improved biomechanical properties55-57 (Figs. 3-A through 3-E). Iannotti et al. performed a biomechanical study of four different all-polyethylene augmentation designs, under both compressive and eccentric loads, to compare their resistance to anterior glenoid liftoff 57. The stepped glenoid was found to have lower initial and final liftoff values compared with the augmentation designs, although not all reached significance. They also found that the stepped glenoid was the only augmented device that was comparable with a standard glenoid
for final simulated long-term fixation. Sabesan et al. utilized computer models of twenty-nine patients with mean retroversion of 20.9° and mean bone loss of 4.8 mm to compare the use of stepped augmented glenoid components and standard glenoid components55. They demonstrated significantly less joint line medialization when they attempted to correct to both neutral (mean, 8.3 mm versus 3.8 mm) and 6° of retroversion (mean, 7.2 mm versus 3.36 mm). The augmented glenoid also provided up to 18° more version correction when the amount of bone removal was held constant. Five shoulders,
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Fig. 3-E
Fig. 3-D The stepped glenoid component with 3 mm of glenoid augmentation (Global Steptech). Fig. 3-E The prepared glenoid with a posterior step-cut (small arrowheads) and prepared central and peripheral peg holes is shown, with the axillary nerve indicated by the large arrow.
four of which had the standard glenoid component, had central peg perforation. Those authors concluded that augmentation or bone-grafting is necessary when there is glenoid retroversion of ‡16°. Glenoid implant augmentation can improve glenoid version while preventing implant perforation, joint line medialization, and subchondral bone loss, but clinical studies are lacking. Augmented glenoid implantation is a technically demanding procedure that requires precise creation of a glenoid bone bed to seat the augmented component. The inability to provide adequate seating of the posterior augment may predispose the implant to micromotion and the risk of loosening13,58,59. It is also still unclear whether augmented glenoid components improve posterior humeral subluxation, which if uncorrected may result in an increased risk of cold flow glenoid polyethylene deformation from mechanical forces13,23. Augmentation can be considered when retroversion is >15°, with the goal of correcting glenoid retroversion to 6°55. Future studies with long-term follow-up are needed to determine the effect of component augmentation on outcomes and implant survival. Reverse Total Shoulder Arthroplasty for Osteoarthritis with Bone Loss Rotator cuff tears can alter glenohumeral mechanics and predispose the glenoid to abnormal wear patterns60. Mizuno et al. reviewed twenty-seven reverse shoulder replacements performed for the treatment of primary glenohumeral osteoarthritis with a
biconcave glenoid with functional rotator cuffs61. Their indications included a patient age of greater than seventy years and retroversion and humeral head subluxation that was believed to be unreliably corrected by asymmetric reaming. The mean preoperative retroversion was 32°, and humeral head subluxation was 87%. Ten patients required a bone graft if version could not be corrected to within 10° of neutral or when the baseplate surface contact was 25° of retroversion regardless of bone loss as a type-C deformity8. This glenoid is distinguished from a Walch type-B2 glenoid by the lack of humeral head subluxation due to hypertrophy of posterior soft-tissue structures that have adapted to the altered morphology. Severe hypoplasia compromises the glenoid vault and may prevent placement of a glenoid implant; the results of hemiarthoplasty alone have been mixed67,68. Edwards et al. evaluated fifteen patients with dysplastic glenoids at a mean of thirty-seven months in a multicenter
Functional Outcome
Radiographic Outcome
Complications
study consisting of eleven total shoulder arthroplasties and four hemiarthroplasties69. The glenoid was replaced if ‡15 mm of glenoid bone stock was present on preoperative CT scans. Correction of version was not attempted as there was no humeral head subluxation. Subjectively, nine shoulders were rated as excellent, four as good, and one as fair. One glenoid component became loose and was removed. Postoperative mobility scores were reported to be better with glenoid resurfacing (mean, 36 versus 22.7; p = 0.011), but no difference was found for other parameters evaluated. Those authors recommended resurfacing the glenoid if bone stock is sufficient. Allen et al. reported on twenty-two dysplastic shoulders, fourteen of which were treated with total shoulder arthroplasty58. The mean duration of follow-up was six years. The decision to perform a hemiarthroplasty was based on the patient’s age and amount of bone loss. Pain was relieved in four of eight shoulders after hemiarthroplasty and in ten of fourteen shoulders after total shoulder arthroplasty; motion improvements were similar for both cohorts. Four shoulders that had a hemiarthroplasty were revised to total shoulder arthroplasty because of pain. Two total shoulder replacements were revised because of infections,
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and three underwent revisions for glenoid problems. The only unsatisfactory results for glenoid resurfacing were in patients who required revision surgery. Radiographically, greater than mild humeral head subluxation was seen in six shoulders that had a hemiarthroplasty but in only three that had a total shoulder arthroplasty. They concluded that total shoulder arthroplasty was more consistent in gaining pain relief and controlling humeral subluxation. Favorable results can be obtained with arthroplasty to treat glenohumeral arthritis related to a dysplastic glenoid. Advanced imaging, including three-dimensional imaging, should be done prior to surgical treatment and used to determine if enough glenoid bone is available to allow placement of a glenoid component. Overview Chronic glenohumeral arthritis, traumatic injury, postreconstruction arthropathy, and developmental conditions such as glenoid dysplasia can result in posterior glenoid bone erosion and alteration of joint reactive forces. Surgical management should attempt to restore glenoid version in order to minimize off-center loads applied to the glenoid implant and improve implant survival. The literature pertaining to the management of glenoid bone loss consists mainly of biomechanical studies and Level-IV case series but is limited with respect to guidelines for surgical options.
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Glenoid deformity that results in 10° to 15° of glenoid retroversion can be effectively managed with eccentric reaming. When bone loss results in retroversion that exceeds 15°, then correction necessitates using either bone-grafting or augmented implants. A reverse shoulder prosthesis offers another surgical option in elderly, sedentary patients. Posterior glenoid bone loss can affect implant longevity and clinical outcomes, and patients should be counseled on the potential risks associated with treating this condition. n
Scott P. Stephens, MD Fondren Orthopedic Group, 601 Rockmead Drive, Kingwood, TX 77339. E-mail address: [email protected] Kevin C. Paisley, DO Jeffrey Jeng, MPH Anil K. Dutta, MD Michael A. Wirth, MD Department of Orthopaedics, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MSC 7774, San Antonio, TX 78229-3900.
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