- Email: [email protected]
Reverse TSA with an augmented baseplate: Dealing with glenoid deficiency
Accepted Manuscript
Reverse TSA with an Augmented Baseplate: Dealing with Glenoid Deficiency Ian Power MD Sports Medicine Fellow , Thomas W. Throckmorton MD Professor PII: DOI: Reference:
S1045-4527(18)30057-9 https://doi.org/10.1053/j.sart.2018.10.006 YSART 50820
To appear in:
Seminars in Arthroplasty
Please cite this article as: Ian Power MD Sports Medicine Fellow , Thomas W. Throckmorton MD Professor , Reverse TSA with an Augmented Baseplate: Dealing with Glenoid Deficiency, Seminars in Arthroplasty (2018), doi: https://doi.org/10.1053/j.sart.2018.10.006
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Reverse TSA with an Augmented Baseplate: Dealing with Glenoid Deficiency Ian Power, MD1 and Thomas W. Throckmorton, MD2 Professor, Campbell Clinic-University of Tennessee Department of Orthopaedic Surgery & Biomedical Engineering
Sports Medicine Fellow, Campbell Clinic-University of Tennessee Department of Orthopaedic
Surgery & Biomedical Engineering 1211 Union Avenue, Suite 510, Memphis TN 38104
2
Fax: 901-759-3278
Email: [email protected]
AN US
Phone: 901-759-3270
CR IP T
1
Professor, Campbell Clinic-University of Tennessee Department of Orthopaedic Surgery &
Biomedical Engineering
Fax: 901-759-3278
Email: [email protected]
ED
Phone: 901-759-3270
M
1211 Union Avenue, Suite 510, Memphis TN 38104
From: Campbell Clinic-University of Tennessee Department of Orthopaedic Surgery &
PT
Biomedical Engineering
CE
Funding: No funds were received in support of this study.
AC
Address for reprints: As above.
Abstract
ACCEPTED MANUSCRIPT
Glenoid deficiencies are present in 40% of patients who have reverse shoulder arthroplasty; these deficiencies must be treated to ensure correct orientation of the glenoid baseplate to optimize fixation and function and reduce complications. Small defects can be managed with eccentric reaming, bone
grafting, or glenoid augmentation; larger defects generally are treated with bone grafting or more
CR IP T
recently glenoid augmentation. Augmented glenoids have shown good results, roughly equivalent to bone grafting. They may be advantageous in decreasing operative time, graft
osteolysis, subsidence, and non-union, though there is little mid-term and no long-term clinical
AN US
data.
INTRODUCTION
Because of the success of reverse total shoulder arthroplasty (RTSA), indications for this
M
procedure have expanded from rotator cuff arthropathy to include proximal humeral fractures, irreparable rotator cuff tears, revision shoulder arthroplasty, and severe glenoid bone loss and/or
ED
retroversion [1,2]. The most common glenoid wear patterns that must be considered during reverse total shoulder arthroplasty are posterior, posteroinferior, and superior [3,4].
PT
Glenoids with eccentric wear, particularly Walch type B2 glenoids, are present in 40% of
CE
patients who have shoulder arthroplasty for osteoarthritis [3]. In patients with eccentric wear, almost half have posterior erosion [5]. Severe posterior wear, defined as retroversion of more
AC
than 25 degrees, was previously thought to be present in approximately 9% of patients with glenohumeral osteoarthritis [6], but more recently has been estimated to be present in as many as 37.5% of patients undergoing rTSA [5]. In patients with significant wear, conventional reaming will result in unsupported glenoid components in almost half [3]. Glenoid deficiency not only contributes to decreased bone stock, but also changes the version as well as inclination of the glenoid. These multi-planar deformities must be corrected to
ACCEPTED MANUSCRIPT
reduce notching and increase range of motion and prosthesis survival [7]. Failure to correct superior erosion can lead to superior tilt of the glenoid baseplate, which contributes to instability, increased shear forces, and aseptic loosening, as well as inferior impingement and scapular notching [8-11].
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A variety of techniques are available for treating glenoid bone loss during RTSA, including eccentric reaming, humeral head allograft, impaction grafting, hybrid graft and
baseplate constructs, and use of augmented glenoid and patient-specific components [12,13]. TREATMENT OPTIONS
AN US
Eccentric Reaming
Small glenoid bone defects can be treated with glenoid reaming alone [5]. Eccentric, “high-side,” reaming also has been described for retroversion up to 32 degrees. In a group of 42 consecutive
M
patients with primary glenohumeral osteoarthritis, intact rotator cuffs, and Walch type A2, B2, or C glenoids, McFarland et al. found notching in eight patients (19%), and baseplate failure in one
ED
patient with a Walch C-type glenoid and two peripheral baseplate screws [14]. With larger defects, eccentric reaming may result in loss of subchondral bone and medialization of the joint
PT
line. Medialization can reduce deltoid wrapping, cause shortening of the remaining rotator cuff
CE
musculature, and result in inferomedial impingement with scapular notching [15,16]. Bone Grafting
AC
Bone grafting may involve humeral head or iliac crest tricortical autograft, as well as allograft [17]. In addition to lateralizing the center of rotation, it can be used in primary and revision arthroplasties [18]. Allograft generally is obtained from the tibial plateau; however, proximal femoral allograft also has been described [18]. The use of humeral head autograft or structural allograft has reduced the morbidity of iliac crest bone graft [7,18].
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For significant glenoid bone loss, single-stage impaction grafting has been shown to be effective in 92.5% of patients with complex glenoid defects [17]; however, the authors reported a 13% complication rate in 54 patients, including one patient with early graft failure and loss of fixation. Similarly, in a group of 20 patients undergoing primary or revision RTSA with single-
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stage autograft or allograft, all showed good functional improvement and 95% graft healing on postoperative CT. They had a 20% complication rate: one patient with aseptic loosening and three patients with symptomatic scapular notching at a minimum 2-year follow-up. The aseptic loosening was due to graft failure and required revision surgery [18]. Structural allograft taken
AN US
from the humeral head also has been successful at correcting glenoid defects up to 35 degrees with 100% graft incorporation on radiographs and 93% baseplate survival at a minimum of 2 years. In another series, complications occurred in four of 14 patients, including one failure due
M
to migration of the baseplate because of partial healing of the graft [19]. The BIO-RSA technique using a trapezoidal autograft described by Boileau et al. [7] also has shown good results for
ED
multiplanar glenoid deformity of more than 25 degrees. Graft incorporation was 94% in their 54 patients; one patient had septic loosening and two (3.7%) had aseptic baseplate loosening in the
PT
first month. One of these was due to trauma, and the second due to uncorrected superior
CE
inclination of the baseplate.
Use of a supplementary plate on the glenoid for additional fixation has been described to
AC
stabilize and compress the autograft in an attempt to decrease the risk of graft subsidence, erosion or loss of fixation [12] In a series of 16 patients, all grafts were healed on postoperative CT, although two patients had graft resorption of less than 25% [12]. Glenoid Augmentation
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Tantulum metal augments are commonly used for lower extremity arthroplasty. Clinical data for wedge-shaped tantulum augments for total shoulder arthroplasty (TSA) have shown correction of version in B2 and C glenoids without complications or implant failures and with reliable incorporation of the augment and satisfied patients with improved clinical outcomes [12]. In
CR IP T
RTSA the fixation of the baseplate allows more durable fixation than in anatomic TSA. Custom porous tantalum augments have been described for use in RTSA for salvage situations where there is severe bone loss and medialization of the joint line and no local autograft due to the revision setting [21]. Standard glenoid-based component augmentation for RTSA was introduced
AN US
as an alternative to bone grafting or eccentric reaming [22]. Use of augmented baseplates
eliminates excess bone removal and mitigates issues of graft healing, resorption, and possible failure [23].
M
Biomechanical data comparing standard baseplates with eccentric reaming to augmented baseplates to correct simulated eccentric wear in composite scapulas showed no difference in
ED
initial fixation, though the augmented components required removal of less bone [24,25]. Other biomechanical testing has shown that failure to correct simulated bony defects in RTSA leads to
PT
micromotion of the baseplate after cyclic testing, which may lead to aseptic loosening and failure
CE
[26]. Allred et al. [27], in finite element models of arthritic scapulae, compared four glenoid implant configurations: standard in neutral alignment with eccentric reaming, standard in
AC
retroversion, augmented with a posterior wedge in neutral alignment, and augmented with a posterior step in neutral aligment. They found that eccentric reaming for a standard implant in neutral version required the most bone removal, resulted in the lowest percentage of back surface supported by cortical bone, and generated strain levels that risked damage to the most bone volume.
ACCEPTED MANUSCRIPT
Both posterior and superior augmented baseplates have been shown to be successful, with improved outcomes at 2-year follow-up. In a report of 39 patients with RSTA, scapular notching was found in twice as many patients with superior augments as those with posterior augments; those with posterior augments also had higher outcomes scores and better active
CR IP T
forward flexion, with no complications. This may be due to posterior wear patterns being more common with osteoarthritis and superior wear with rotator cuff arthropathy [23].
In a larger study of 139 patients who had reverse shoulder arthroplasty with posterior, superior, or posterosuperior augmentation of the glenoid baseplate, all had improvements in
AN US
functional outcomes [22], with the most significant improvements in external rotation and
forward flexion occurring in patients with posterosuperior augmentation. Patients with posterior augmentation had the most improvement in American Shoulder and Elbow Surgeons (ASES)
M
and Constant Scores. Complications occurred in 13% of those with superior augmentation, 8% of those with posterior augmentation, and 13% of those with posterosuperior augmentation. The
ED
most frequent complication was aseptic baseplate loosening, which accounted for over half the complications in the posterosuperior augmentations.
PT
Jones et al. retrospectively compared 80 patients with primary RTSA with either an
CE
augmented glenoid baseplate or structural bone graft [28]. Both groups showed improvement from preoperative objective functional scores and range of motion. There was a 14.6%
AC
complication rate in the bone graft group compared with none in the augmented group. The augmented group also had less scapular notching (10% vs 18.5%). Michael et al suggested using an augmented baseplate to correct glenoids with more than
25 degrees of deformity in young healthy patients or when bony contact is less than 50% with a standard glenoid baseplate [22].
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Author’s Preferred Surgical Technique We routinely use preoperative CT and/or MRI to evaluate the degree and position of glenoid bone loss. It is important to keep in mind that intraoperatively, even with thorough exposure, the glenoid tends to face away from the surgeon, which can lead to a misunderstanding of the
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glenoid deformity during surgery. Careful preparation and understanding of the glenoid erosion are vital for accurate component placement in patients with glenoid bone loss.
We perform RTSA through a standard deltopectoral approach with the patient in the beach chair position. Thorough subdeltoid, subcoraoid, and subacromial releases facilitate
AN US
exposure. The subscapularis typically is managed with tenotomy for later repair when feasible, followed by an extensive inferior capsular release. The humeral head cut is made with the shoulder in 30 degrees of retroversion before preparation of the glenoid.
M
After excision of the labrum and soft tissue to expose the bony glenoid, a glenoid targeting guide is used to place a guidewire in 10 degrees of inferior tilt. The cannulated glenoid
ED
reamer is used to ream the glenoid until 50% of the baseplate will sit on native bone. The appropriate-sized augment guide is measured for the amount of bone loss and placed in the
PT
defect in the correct orientation to match the preoperative imaging. The augment guide must be
CE
of sufficient depth, or there will not be bony contact of the defect with the reamer or implant once it is impacted. A guide is used to drill a positioning hole 180 degrees opposite the defect to
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guide orientation of the reamer and implant. The augment reaming guide is placed and secured with a screw. A bushing can be then placed on the guide and the “low side” of the glenoid defect reamed. Appropriate reaming is confirmed with the trial augment baseplate. If reaming is accurate, the augmented baseplate is impacted into position. Care must be taken to ensure proper orientation, using the previously drilled positioning hole, because the augments are specific to
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the depth and rotation of the prepared defect. A central screw is placed through the baseplate in compression, followed by the four peripheral locking screws and standard glenosphere insertion. Completion of the humeral preparation, trialing, and implantation are done in standard fashion (Figure 1).
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Conclusion
Several options are available to treat eccentric glenoid wear in RTSA. For small defects, eccentric reaming, bone grafting, or glenoid augmentation may be successful. For larger
deficiencies, bone grafting and use of augmented glenoid components have been shown to be
AN US
successful, with roughly equivalent results and complications. Augmented glenoid components may be advantageous to correct glenoid deformity while avoiding concerns about joint-line medialization due to overreaming, osteolysis, non-union, graft availability, and component
M
loosening.
ED
DISCLOSURE
Thomas Throckmorton reports stock or stock options, Gilead; IP royalties, paid presenter or
PT
speaker, Zimmer Biomet; publishing royalties, Elsevier.
CE
Ian Power reports no proprietary or commercial interest in any produce mentioned or concept
AC
discussed in this article.
REFERENCES 1. Hsu JE, Ricchetti ET, Huffman GR, et al. Addressing glenoid bone deficiency and asymmetric posterior erosion in shoulder arthroplasty. J Shoulder Elbow Surg 22:12981308, 2013.
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2. Seidl AJ, Williams GR, Boileau P. Challenges in reverse shoulder arthroplasty: addressing glenoid bone loss. Orthopedics 39(1):14-23, 2016. 3. Churchill RS, Spencer EE Jr, Fehringer EV. Quantification of B2 glenoid morphology in total shoulder arthroplasty. J Shoulder Elbow Surg 24:1212-1217, 2015. 4. Sirveaux F, Favard L, Oudet D, et al. Grammont inverted total shoulder arthroplasty in
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the treatment of glenohumeral osteoarthritis with massive rupture of the cuff. J Bone Joint Surg Br 86:388-395, 2004.
5. Frankle MA, Teramoto A, Luo Z-P, et al. Glenoid morphology in reverse shoulder
arthroplasty: classification and surgical implications. J Shoulder Elbow Surg 18:874-885, 2009.
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6. Walch G, Badet R, Boulahia A, et al. Morphologic study of the glenoid in primary glenohumeral osteoarthritis. J Arthroplasty 14(6):756-760, 1999.
7. Boileau P, Morin-Salvo N, Gauci M-O, et al. Angled BIO-RSA (bony-increased offsetreverse shoulder arthroplasty): a solution for the management of glenoid bone loss and erosion. J Shoulder Elbow Surg 26:2133-2142, 2017.
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8. Frankle MA, Siegal S, Pupello DR, et al. Coronal plane tilt angle affects risk of catastrophic failure in patients treated with a reverse shoulder prosthesis. J Shoulder
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Elbow Surg 16:e46, 2007.
9. Gutiérrez S, Greiwe M, Frankle MA, et al. Biomechanical comparison of component position and hardward failure in the reverse shoulder prosthesis. J Shoulder Elbow Surg
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16(3 Suppl):S9-S12, 2007.
10. Gutiérrez S, Walker M, Willis M, et al. Effects of tilt and glenosphere eccentricity on
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baseplate/bone interface forces in a computational model, validated by a mechanical model, of reverse shoulder arthroplasty. J Shoulder Elbow Surg 20:732-739, 2011.
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11. Lévigne C, Garret J, Boileau P, et al. Scapular notching in reverse shoulder arthroplasty: is it important to avoid it and how? Clin Orthop Relat Res 469:2512-2520, 2011.
12. Lanzone R, Carbone S, Albino P, et al. Retroverted glenoid reconstruction using glenoid plate in reverse shoulder arthroplasty. Musculoskelet Surg 101 (Suppl 2):S121-S127, 2017. 13. Norris TR. Glenoid bone loss in reverse shoulder arthroplasty treated with bone graft techniques. Am J Orthop (Belle Mead NJ) 47(3), March 23, 2018.
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14. McFarland EG, Huri G, Hyun YS, et al. Reverse total shoulder arthroplasty without bone-grafting for severe glenoid bone loss in patients with osteoarthritis and intact rotator cuff. J Bone Joint Surg Am 98:1801-1807, 2016. 15. Boileau P, Watkinson D, Hatzidakis AM, et al. Neer Award 2005: The Grammont reverse shoulder prosthesis: results in cuff tear arthritis, fracture sequelae, and revision
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arthroplasty. J Shoulder Elbow Surg 15(5):527-540, 2006. 16. Roche CP, Diep P, Hamilton M, et al. Impact of inferior glenoid tilt, humeral
retroversion, bone grafting, and design parameters on muscle length and deltoid wrapping in reverse shoulder arthroplasty. Bull Hosp Jt Dis 71(4):284-293, 2013.
17. Gupta A, Thussbas C, Koch M, et al. Management of glenoid bone defects with reverse
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shoulder arthroplasty—surgical technique and clinical outcomes. J Shoulder Elbow Surg 27:853-862, 2018.
18. Lopiz Y, García-Fernández C, Arriaza A, et al. Midterm outcomes of bone grafting in glenoid defects treated with reverse shoulder arthroplasty. J Shoulder Elbow Surg 26:1581-1588, 2017.
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19. Tashjian RZ, Granger E, Chalmers PN. Structural glenoid grafting during primary reverse total shoulder arthoplasty using humeral head autograft. J Shoulder Elbow Surg 27:e1-e8,
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2018.
20. Sandow M, Schutz C. Total shoulder arthroplasty using trabecular metal augments to address glenoid retroversion: the preliminary result of 10 patients with minimum 2-year
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follow-up. J Shoulder Elbow Surg 25:598-607, 2016. 21. Ivaldo N, Mangano T, Caione G, et al. Customized tantalum-augmented reverse shoulder
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arthroplasty for glenoid bone defect and excessive medialization: description of the technique. Musculoskelet Surg 100 (Suppl 1):13-18, 2016.
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22. Michael RJ, Schoch BS, King JJ, et al. Managing glenoid bone deficiency—the augment experience in anatomic and reverse shoulder arthroplasty. Am J Orthop (Belle Mead NJ) 47(2), March 5, 2018.
23. Wright TW, Roche CP, Wright L, et al. Reverse shoulder arthroplasty augments for glenoid wear. Comparison of posterior augments to superior augments. Bull Hosp Jt Dis 73(Suppl 1):S124-128, 2015.
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24. Friedman R, Stroud N, Glattke K, et al. The impact of posterior wear on reverse shoulder glenoid fixation. Bull Hosp Jt Dis 73(Suppl 1):S15-20. 2015. 25. Roche CP, Stroud NJ, Martin BL, et al. Achieving fixation in glenoids with superior wear using reverse shoulder arthroplasty. J Shoulder Elbow Surg 22:1695-1701, 2013. 26. Martin EJ, Duquin TR, Ehrensberger MT. Reverse total shoulder glenoid baseplate
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stability with superior glenoid bone loss. J Shoulder Elbow Surg 26:1748-1755, 2017. 27. Allred JJ, Flores-Hernandez C, Hoenecke HR Jr, et al. Posterior augmented glenoid
implants require less bone removal and generate lower stresses: a finite element analysis. J Shoulder Elbow Surg 25:823-830, 2016.
28. Jones R, Wright TW, Roche CP. Bone grafting the glenoid versus use of augmented
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glenoid baseplates with reverse shoulder arthroplasty. Bull Hosp Jt Dis 73(Suppl 1):S129-135, 2015.
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LEGEND FOR ILLUSTRATION
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Figure 1. Reverse total shoulder arthroplasty with baseplate augmentation in a patient with large
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glenoid defect.
Reverse TSA with an Augmented Baseplate: Dealing with Glenoid Deficiency Ian Power MD Sports Medicine Fellow , Thomas W. Throckmorton MD Professor PII: DOI: Reference:
S1045-4527(18)30057-9 https://doi.org/10.1053/j.sart.2018.10.006 YSART 50820
To appear in:
Seminars in Arthroplasty
Please cite this article as: Ian Power MD Sports Medicine Fellow , Thomas W. Throckmorton MD Professor , Reverse TSA with an Augmented Baseplate: Dealing with Glenoid Deficiency, Seminars in Arthroplasty (2018), doi: https://doi.org/10.1053/j.sart.2018.10.006
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Reverse TSA with an Augmented Baseplate: Dealing with Glenoid Deficiency Ian Power, MD1 and Thomas W. Throckmorton, MD2 Professor, Campbell Clinic-University of Tennessee Department of Orthopaedic Surgery & Biomedical Engineering
Sports Medicine Fellow, Campbell Clinic-University of Tennessee Department of Orthopaedic
Surgery & Biomedical Engineering 1211 Union Avenue, Suite 510, Memphis TN 38104
2
Fax: 901-759-3278
Email: [email protected]
AN US
Phone: 901-759-3270
CR IP T
1
Professor, Campbell Clinic-University of Tennessee Department of Orthopaedic Surgery &
Biomedical Engineering
Fax: 901-759-3278
Email: [email protected]
ED
Phone: 901-759-3270
M
1211 Union Avenue, Suite 510, Memphis TN 38104
From: Campbell Clinic-University of Tennessee Department of Orthopaedic Surgery &
PT
Biomedical Engineering
CE
Funding: No funds were received in support of this study.
AC
Address for reprints: As above.
Abstract
ACCEPTED MANUSCRIPT
Glenoid deficiencies are present in 40% of patients who have reverse shoulder arthroplasty; these deficiencies must be treated to ensure correct orientation of the glenoid baseplate to optimize fixation and function and reduce complications. Small defects can be managed with eccentric reaming, bone
grafting, or glenoid augmentation; larger defects generally are treated with bone grafting or more
CR IP T
recently glenoid augmentation. Augmented glenoids have shown good results, roughly equivalent to bone grafting. They may be advantageous in decreasing operative time, graft
osteolysis, subsidence, and non-union, though there is little mid-term and no long-term clinical
AN US
data.
INTRODUCTION
Because of the success of reverse total shoulder arthroplasty (RTSA), indications for this
M
procedure have expanded from rotator cuff arthropathy to include proximal humeral fractures, irreparable rotator cuff tears, revision shoulder arthroplasty, and severe glenoid bone loss and/or
ED
retroversion [1,2]. The most common glenoid wear patterns that must be considered during reverse total shoulder arthroplasty are posterior, posteroinferior, and superior [3,4].
PT
Glenoids with eccentric wear, particularly Walch type B2 glenoids, are present in 40% of
CE
patients who have shoulder arthroplasty for osteoarthritis [3]. In patients with eccentric wear, almost half have posterior erosion [5]. Severe posterior wear, defined as retroversion of more
AC
than 25 degrees, was previously thought to be present in approximately 9% of patients with glenohumeral osteoarthritis [6], but more recently has been estimated to be present in as many as 37.5% of patients undergoing rTSA [5]. In patients with significant wear, conventional reaming will result in unsupported glenoid components in almost half [3]. Glenoid deficiency not only contributes to decreased bone stock, but also changes the version as well as inclination of the glenoid. These multi-planar deformities must be corrected to
ACCEPTED MANUSCRIPT
reduce notching and increase range of motion and prosthesis survival [7]. Failure to correct superior erosion can lead to superior tilt of the glenoid baseplate, which contributes to instability, increased shear forces, and aseptic loosening, as well as inferior impingement and scapular notching [8-11].
CR IP T
A variety of techniques are available for treating glenoid bone loss during RTSA, including eccentric reaming, humeral head allograft, impaction grafting, hybrid graft and
baseplate constructs, and use of augmented glenoid and patient-specific components [12,13]. TREATMENT OPTIONS
AN US
Eccentric Reaming
Small glenoid bone defects can be treated with glenoid reaming alone [5]. Eccentric, “high-side,” reaming also has been described for retroversion up to 32 degrees. In a group of 42 consecutive
M
patients with primary glenohumeral osteoarthritis, intact rotator cuffs, and Walch type A2, B2, or C glenoids, McFarland et al. found notching in eight patients (19%), and baseplate failure in one
ED
patient with a Walch C-type glenoid and two peripheral baseplate screws [14]. With larger defects, eccentric reaming may result in loss of subchondral bone and medialization of the joint
PT
line. Medialization can reduce deltoid wrapping, cause shortening of the remaining rotator cuff
CE
musculature, and result in inferomedial impingement with scapular notching [15,16]. Bone Grafting
AC
Bone grafting may involve humeral head or iliac crest tricortical autograft, as well as allograft [17]. In addition to lateralizing the center of rotation, it can be used in primary and revision arthroplasties [18]. Allograft generally is obtained from the tibial plateau; however, proximal femoral allograft also has been described [18]. The use of humeral head autograft or structural allograft has reduced the morbidity of iliac crest bone graft [7,18].
ACCEPTED MANUSCRIPT
For significant glenoid bone loss, single-stage impaction grafting has been shown to be effective in 92.5% of patients with complex glenoid defects [17]; however, the authors reported a 13% complication rate in 54 patients, including one patient with early graft failure and loss of fixation. Similarly, in a group of 20 patients undergoing primary or revision RTSA with single-
CR IP T
stage autograft or allograft, all showed good functional improvement and 95% graft healing on postoperative CT. They had a 20% complication rate: one patient with aseptic loosening and three patients with symptomatic scapular notching at a minimum 2-year follow-up. The aseptic loosening was due to graft failure and required revision surgery [18]. Structural allograft taken
AN US
from the humeral head also has been successful at correcting glenoid defects up to 35 degrees with 100% graft incorporation on radiographs and 93% baseplate survival at a minimum of 2 years. In another series, complications occurred in four of 14 patients, including one failure due
M
to migration of the baseplate because of partial healing of the graft [19]. The BIO-RSA technique using a trapezoidal autograft described by Boileau et al. [7] also has shown good results for
ED
multiplanar glenoid deformity of more than 25 degrees. Graft incorporation was 94% in their 54 patients; one patient had septic loosening and two (3.7%) had aseptic baseplate loosening in the
PT
first month. One of these was due to trauma, and the second due to uncorrected superior
CE
inclination of the baseplate.
Use of a supplementary plate on the glenoid for additional fixation has been described to
AC
stabilize and compress the autograft in an attempt to decrease the risk of graft subsidence, erosion or loss of fixation [12] In a series of 16 patients, all grafts were healed on postoperative CT, although two patients had graft resorption of less than 25% [12]. Glenoid Augmentation
ACCEPTED MANUSCRIPT
Tantulum metal augments are commonly used for lower extremity arthroplasty. Clinical data for wedge-shaped tantulum augments for total shoulder arthroplasty (TSA) have shown correction of version in B2 and C glenoids without complications or implant failures and with reliable incorporation of the augment and satisfied patients with improved clinical outcomes [12]. In
CR IP T
RTSA the fixation of the baseplate allows more durable fixation than in anatomic TSA. Custom porous tantalum augments have been described for use in RTSA for salvage situations where there is severe bone loss and medialization of the joint line and no local autograft due to the revision setting [21]. Standard glenoid-based component augmentation for RTSA was introduced
AN US
as an alternative to bone grafting or eccentric reaming [22]. Use of augmented baseplates
eliminates excess bone removal and mitigates issues of graft healing, resorption, and possible failure [23].
M
Biomechanical data comparing standard baseplates with eccentric reaming to augmented baseplates to correct simulated eccentric wear in composite scapulas showed no difference in
ED
initial fixation, though the augmented components required removal of less bone [24,25]. Other biomechanical testing has shown that failure to correct simulated bony defects in RTSA leads to
PT
micromotion of the baseplate after cyclic testing, which may lead to aseptic loosening and failure
CE
[26]. Allred et al. [27], in finite element models of arthritic scapulae, compared four glenoid implant configurations: standard in neutral alignment with eccentric reaming, standard in
AC
retroversion, augmented with a posterior wedge in neutral alignment, and augmented with a posterior step in neutral aligment. They found that eccentric reaming for a standard implant in neutral version required the most bone removal, resulted in the lowest percentage of back surface supported by cortical bone, and generated strain levels that risked damage to the most bone volume.
ACCEPTED MANUSCRIPT
Both posterior and superior augmented baseplates have been shown to be successful, with improved outcomes at 2-year follow-up. In a report of 39 patients with RSTA, scapular notching was found in twice as many patients with superior augments as those with posterior augments; those with posterior augments also had higher outcomes scores and better active
CR IP T
forward flexion, with no complications. This may be due to posterior wear patterns being more common with osteoarthritis and superior wear with rotator cuff arthropathy [23].
In a larger study of 139 patients who had reverse shoulder arthroplasty with posterior, superior, or posterosuperior augmentation of the glenoid baseplate, all had improvements in
AN US
functional outcomes [22], with the most significant improvements in external rotation and
forward flexion occurring in patients with posterosuperior augmentation. Patients with posterior augmentation had the most improvement in American Shoulder and Elbow Surgeons (ASES)
M
and Constant Scores. Complications occurred in 13% of those with superior augmentation, 8% of those with posterior augmentation, and 13% of those with posterosuperior augmentation. The
ED
most frequent complication was aseptic baseplate loosening, which accounted for over half the complications in the posterosuperior augmentations.
PT
Jones et al. retrospectively compared 80 patients with primary RTSA with either an
CE
augmented glenoid baseplate or structural bone graft [28]. Both groups showed improvement from preoperative objective functional scores and range of motion. There was a 14.6%
AC
complication rate in the bone graft group compared with none in the augmented group. The augmented group also had less scapular notching (10% vs 18.5%). Michael et al suggested using an augmented baseplate to correct glenoids with more than
25 degrees of deformity in young healthy patients or when bony contact is less than 50% with a standard glenoid baseplate [22].
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Author’s Preferred Surgical Technique We routinely use preoperative CT and/or MRI to evaluate the degree and position of glenoid bone loss. It is important to keep in mind that intraoperatively, even with thorough exposure, the glenoid tends to face away from the surgeon, which can lead to a misunderstanding of the
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glenoid deformity during surgery. Careful preparation and understanding of the glenoid erosion are vital for accurate component placement in patients with glenoid bone loss.
We perform RTSA through a standard deltopectoral approach with the patient in the beach chair position. Thorough subdeltoid, subcoraoid, and subacromial releases facilitate
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exposure. The subscapularis typically is managed with tenotomy for later repair when feasible, followed by an extensive inferior capsular release. The humeral head cut is made with the shoulder in 30 degrees of retroversion before preparation of the glenoid.
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After excision of the labrum and soft tissue to expose the bony glenoid, a glenoid targeting guide is used to place a guidewire in 10 degrees of inferior tilt. The cannulated glenoid
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reamer is used to ream the glenoid until 50% of the baseplate will sit on native bone. The appropriate-sized augment guide is measured for the amount of bone loss and placed in the
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defect in the correct orientation to match the preoperative imaging. The augment guide must be
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of sufficient depth, or there will not be bony contact of the defect with the reamer or implant once it is impacted. A guide is used to drill a positioning hole 180 degrees opposite the defect to
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guide orientation of the reamer and implant. The augment reaming guide is placed and secured with a screw. A bushing can be then placed on the guide and the “low side” of the glenoid defect reamed. Appropriate reaming is confirmed with the trial augment baseplate. If reaming is accurate, the augmented baseplate is impacted into position. Care must be taken to ensure proper orientation, using the previously drilled positioning hole, because the augments are specific to
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the depth and rotation of the prepared defect. A central screw is placed through the baseplate in compression, followed by the four peripheral locking screws and standard glenosphere insertion. Completion of the humeral preparation, trialing, and implantation are done in standard fashion (Figure 1).
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Conclusion
Several options are available to treat eccentric glenoid wear in RTSA. For small defects, eccentric reaming, bone grafting, or glenoid augmentation may be successful. For larger
deficiencies, bone grafting and use of augmented glenoid components have been shown to be
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successful, with roughly equivalent results and complications. Augmented glenoid components may be advantageous to correct glenoid deformity while avoiding concerns about joint-line medialization due to overreaming, osteolysis, non-union, graft availability, and component
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loosening.
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DISCLOSURE
Thomas Throckmorton reports stock or stock options, Gilead; IP royalties, paid presenter or
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speaker, Zimmer Biomet; publishing royalties, Elsevier.
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Ian Power reports no proprietary or commercial interest in any produce mentioned or concept
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discussed in this article.
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LEGEND FOR ILLUSTRATION
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Figure 1. Reverse total shoulder arthroplasty with baseplate augmentation in a patient with large
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glenoid defect.