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Cemented humeral shoulder arthroplasty: Because it works!
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Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/sart
Cemented humeral shoulder arthroplasty: Because it works! Brian Grogana, Daniel J. Songb, and Charles M. Jobinc,* a Department of Orthopedics and Rehabilitation, University of Wisconsin School of Medicine and Public Health, UW Health at The American Center, WI, USA b Elbow and Sports Surgery, Department of Orthopedic Surgery, NYP/Columbia University Medical Center, New York, NY, USA c Department of Orthopedic Surgery, NYP/Columbia University Medical Center, 622 West 168th Street, PH-1117, New York, NY 10032, USA
A R T I C L E I N F O
ABSTRA CT
Key Words:
Durable humeral component fixation in shoulder arthroplasty is important to prevent loos-
Cemented stem
ening. Humeral component designs include metaphyseal fitting, diaphyseal fitting with tra-
Shoulder
ditional stem length, short stem, and stemless designs. Stem geometry helps resist
Arthroplasty
rotational and axial stress. Stem collars may prevent subsidence, and may be smooth for
Humeral
full cementation or textured proximally for bone ingrowth. Ideally, the humeral compo-
Radiolucent lines
nent has solid initial fixation, durable long-term fixation, minimizes humeral stress shield-
Loosening
ing, has low intra-operative complication rates, and can easily be revised. Excellent
Stemless
outcomes can be achieved, but there remain relative indications and contraindications for
Short stem
cementing or press-fitting the humeral component.
Reverse
Ó 2018 Elsevier Inc. All rights reserved.
Uncemented
1. Introduction to the geometry of the proximal humerus Humeral component design and fixation techniques are directly tied to the morphology of the proximal humerus. Modern components are generally modular to account for the wide variability between patients. Textured proximal coating may promote bone ingrowth or ongrowth to create biologic implant fixation, while cementation eliminates this biologic fixation [1]. While fixation is paramount, recreating the geometry of the proximal humerus is important to restore the mechanics of the glenohumeral joint. The arc of the articular surface of the humeral head extends approximately 150°; the head thickness ranges from 12 24 mm and is linked to the humeral head radius of curvature in a 3:4 ratio [2 5]. Work by Robertson and coauthors has demonstrated an average humeral retroversion of 19° (range 9 31) * Corresponding author: E-mail address: [email protected] (C.M. Jobin). https://doi.org/10.1053/j.sart.2018.10.009 1045-4527/Ó 2018 Elsevier Inc. All rights reserved.
and canal diameters ranging from 9 16 mm [2]. When considering the placement of a stemmed humeral component, it is important to note that the proximal humeral endosteal canal is not round, but ellipsoid, with its long axis running from medial to lateral in the axial plane. This axis becomes increasingly retroverted more distally in the humerus. The center of rotation of the humeral head is offset posteriorly by a mean of 2 mm and medially by a mean of 7 mm. There is also an approximately 4-fold tapering of the of the canal from the 1300 mm2 at the surgical neck to 340 mm2 at the diaphysis [2].
2. Humeral stem fixation Stemmed humeral components have long been cemented in the humeral canal. Cement can be placed down the diaphysis to fill the canal all the way to the humeral neck cut to
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provide a complete mantel surrounding the implant (Fig. 1). Alternatively, it can be packed around the metaphyseal aspect of the implant in a more limited partial proximal cementation technique. Both techniques have been shown to be equivalent to press-fitting a smooth-stemmed diaphyseal fitting component with regard to initial axial micromotion [6]. Initial rotational stability in this setting is better with cementation. No difference was seen between partial proximal and full cementation [7]. To improve initial purchase and prevent loosening, humeral components intended to achieve metaphyseal fit have been introduced (Fig. 2). They do not rely on three-point contact between a straight stem and an ellipsoid canal, but instead obtain purchase by reaming the metaphysis to accept an implant of corresponding size [8]. Some implants incorporate a textured surface to promote boney ingrowth or ongrowth. This coating may cover the proximal metaphyseal portion of the implant or extend down the length of the implant to the diaphyseal portion of the stem [9].
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3. Stem loosening Aseptic loosening of standard length humeral components, cemented or press-fit, is fortunately rare. Barrett reported on 44 patients undergoing total shoulder arthroplasty using a cemented humeral component. At an average of 3.5 years of follow-up, only one humeral component had been revised; humeral component survival was 98% in the series [10]. A study by Throckmorton reported zero loosening in 76 patients undergoing total shoulder arthroplasty using a circumferential metaphyseal porous-coated press-fit stem at an average of 52 months of follow-up [9]. Cil and colleagues found that humeral stem loosening occurred in isolation in only 4 of 1,112 (0.03%) of total shoulder arthroplasty cases. Examining revision for any reason, there was 96.2% survival of cemented components and 91.2% survival of noncemented components at 10 year follow-up (p < 0.1) [11]. In a prospective randomized controlled trial of 161 patients, Litchfield found
Figure 1 – Cemented humeral stem during total shoulder arthroplasty. 4 years after cemented humeral stem during TSA without loosening of stem, nor significant stress shielding.
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Figure 2 – Press-fit metaphyseal fitting humeral stem during total shoulder arthroplasty. 2 years after press-fit metaphyseal fitting humeral stem during total shoulder arthroplasty without evidence of calcar resorption, but mild tuberosity stress shielding.
no evidence of humeral loosening in either cemented or noncemented humeral components [12]. Keener and coauthors pooled the results of several large shoulder arthroplasty studies [8,9,11 14]. They found a weighted mean aseptic loosening rate of 0.2% with cemented implants and 0.9% for noncemented implants and an overall revision rate of 2.6% for cemented implants and 7.47% for noncemented implants [15]. Keener also noted that some bias may be inherent in these series, as cemented humeral stems can be difficult to revise and have a significant complication rate [15,16].
4. Radiographic evaluation of humeral stems Radiographic changes and functional outcomes have been studied in standard length cemented and uncemented stems. As described by Denard, stress shielding of the proximal humerus results from sharing of physiologic load between
the remaining humeral bone and the implanted humeral prosthesis. Stress shielding may manifest as tuberosity resorption, cortical thinning, or calcar osteolysis (Fig. 3). It has been linked to humeral implant characteristics such as stem length and diameter fill ratio [1]. Osteolysis may result from stress shielding, but it has also been linked to glenoid polyethylene wear and debris [13]. Glenoid component wear characteristics may introduce confounding variables into the evaluation of stress shielding of the proximal humerus based on humeral implant design and fixation technique. Humeral implants that are circumferentially proximally cemented or coated with an ongrowth surface may be less susceptible to distal particulate-induced osteolysis [13,15]. At long term follow-up, high rates of radiolucent lines can be seen in both cemented (Fig. 4) and uncemented components, but these lines have not been linked to loosening or revision [13,17]. Looking at functional outcomes, the only Level 1 data available suggests that cemented humeral components may
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Figure 3 – Calcar resorption and stress shielding after cemented hemiarthroplasty. Calcar resorption and greater tuberosity stress shielding 6 years after well cemented humeral stem without evidence of loosening.
outperform uncemented non-coated diaphyseal press-fit components at 24 months of follow-up. Cemented components demonstrated a significant improvement in the Western Ontario Osteoarthritis of the Shoulder (WOOS) score over uncemented components. There was no significant difference in the American Shoulder and Elbow Surgeons (ASES) Standardized Shoulder Assessment or McMaster-Toronto Arthritis Patient Preference Disability Questionnaire (MACTAR) [12].
5. Short and stemless humeral stems In recent years, there has been increasing usage of short stem and stemless humeral components. While these implants may
be compatible with cemented fixation, many surgeons are moving toward press-fit implantation of these components [18 21]. The use of short stems may preserve bone stock in the setting of a revision surgery. Stemless components not only preserve bone, but may they be useful in settings where the distortion of native proximal humeral anatomy makes the use of a stemmed humeral component difficult (Fig. 5). Many of these short stem and stemless components also feature ingrowth or ongrowth surface coatings [19]. There is significant design variation in short stem shape, taper, and collar. There are also a variety of metaphyseal engagement mechanisms among the stemless humeral components [1]. Because short-stem and stemless implants are relatively new, little long-term data on loosening and revision is
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with the addition of a proximal ingrowth coating [19]. In their comparison of 34 proximally coated and 34 uncoated implants at an average of 27. 3 months of follow-up, they found a significantly higher incidence of humeral lucency and “at-risk” humeral stems among the uncoated group. No humeral component required revision. Only one stem was found to be loose, and it was in the uncoated group. Romeo reported on the use of a short-stem press-fit humeral component and found 9% of stems to be “at-risk” for loosening on radiographs but no gross loosening or revision for any reason at mean 25 months of post-operative follow-up [20].
6. Reverse shoulder humeral stems Reverse total shoulder arthroplasty was designed to alter the fundamental biomechanics of the shoulder joint to compensate for a deficient rotator cuff. Reverse total shoulder arthroplasty changes the joint center of rotation to maximize the function of the deltoid and minimize stress on the glenoid component [23]. The effects of altered joint compression and shear forces upon loosening and stress shielding of the humeral component of the reverse prosthesis are not completely known [15]. A systematic review by Phadnis of 41 clinical studies including 1455 cemented and 329 uncemented reverse total shoulder arthroplasty humeral components demonstrated equivalent clinical outcomes and no difference in rates of loosening or revision [24]. Uncemented stems (Fig. 6) did have higher rates of non-progressive radiolucent lines and stem migration, while cemented stems had higher rates of acromial fracture, infection, nerve injury, and thromboembolism. A systematic review and meta-analysis by Grey comprised of 65 studies including 1,660 cemented and 805 uncemented reverse total shoulder arthroplasty humeral components revealed no difference in rates of aseptic loosening or revision between the two groups [25]. Figure 4 – Aseptic loosening of cemented humeral stem during hemiarthroplasty for fracture. Aseptic stem loosening 4 years after hemiarthroplasty for fracture with tuberosity resorption, radiolucent lines around the cemented stem. This constellation of findings was concerning for deep infection therefore an open biopsy of the bone-implant interface did not demonstrate infection and a revision reverse replacement was performed 1 month later.
available. However, short-term follow-up results using a grit blasted short-stem press-fit humeral component without a proximal porous coating demonstrated aseptic humeral loosening in 4/73 (5.48%) patients, 2 (2.74%) of whom underwent revision arthroplasty for aseptic humeral loosening. There were radiolucent zones noted on 71% of radiographs at 24 months follow-up [18]. A mid-term follow-up on the same implant by Schnetzke reported a 37% rate of high boney adaptation and a 66% rate of cortical narrowing and osteopenia at the calcar in a group of 66 patients at a mean follow-up of 5.3 years. The authors reported no evidence of humeral component loosening [22]. Morwood and coauthors reported outcomes following the release of an new version of the implant
7. Comparing cemented and uncemented humeral stems While outcomes of anatomic and reverse arthroplasty with both cemented and noncemented humeral components are generally comparable, there exist distinct advantages and disadvantages to selecting a cemented technique. Cementation of the humeral component during shoulder arthroplasty has the advantage of providing immediate fixation with minimal broaching or reaming in patients with poor bone quality. Cement can fill gaps between bone and the humeral component when proximal humeral morphology or bone loss create a bone/prosthesis mismatch [2,8]. A good cement mantle may also prevent osteolysis by excluding glenoid wear debris from the humeral canal [13]. Cement can also serve as a carrier for antibiotics. The use of cement for initial fixation does have disadvantages. It increases operative time and complexity. In the revision setting, cemented stems can be difficult to revise [26]. Retained cement at the time of revision surgery for infection may serve as a nidus for subsequent relapse and treatment failure. The decision to use cement should be based on
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Figure 5 – Stemless hemiarthroplasty. Stemless hemiarthoplasty in a 44 year old man. This design utilizes ingrowth metaphyseal fins. The 2 year radiographic outcomes are encouraging.
careful consideration of each patient’s overall clinical picture and the likelihood of future surgical intervention.
8. Conclusions Immediate solid, durable fixation of the humeral component in total shoulder arthroplasty is key to the long term success. Using standard length stems, both cemented and uncemented stems of a very low rate of aseptic loosening and revision. Osteolysis may occur in response to stress shielding proximal to cemented or large diameter press-fit humeral components, but glenoid wear likely plays a role in bone resorption as well. Short stem and stemless components have theoretical advantages, but long-term data is limited and early reports suggest high rates of loosening and radiographic changes with some implants. Data on reverse total
shoulder arthroplasty suggests that cemented and uncemented humeral components both perform well. Surgeons should recognize the relative indications and contraindications for the use of a cemented humeral component and allow individual case characteristics to guide clinical decision making.
Disclosures This study did not receive any grant or research support. Dr. Charles M Jobin is a consultant for Acumed, DePuy-Synthes, Wright-Tornier, Zimmer-Biomet and is Deputy Editor for JAAOS. Dr. Brian Grogan and Dr. Daniel J. Song, and their immediate families, and any research foundation with which they are affiliated have not received any financial or
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Figure 6 – Press-fit reverse humeral stem. Press-fit reverse shoulder arthroplasty humeral stem with metaphyseal ingrowth and diaphyseal fill.
other benefits from any commercial entity related to the subject of this article.
B I B L I O G R A PH Y
[1] Denard PJ, Raiss P, Gobezie R, Edwards TB, Lederman E. Stress shielding of the humerus in press-fit anatomic shoulder
arthroplasty: review and recommendations for evaluation. J Shoulder Elbow Surg 2018. Feb 5. [2] Robertson DD, Yuan J, Bigliani LU, Flatow EL, Yamaguchi K. Three-dimensional analysis of the proximal part of the humerus: relevance to arthroplasty. JBJS 2000;82(November (11)):1594–602. [3] Iannotti JP, Gabriel JP, Schneck SL, Evans BG, Misra S. The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders. J Bone Joint Surg Am 1992;74(April(4)):491–500.
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[4] Hertel R, Knothe U, Ballmer FT. Geometry of the proximal humerus and implications for prosthetic design. J Shoulder Elbow Surg 2002;11(July (4)):331–8. [5] Pearl ML. Proximal humeral anatomy in shoulder arthroplasty: implications for prosthetic design and surgical technique. J Shoulder Elbow Surg 2005;14(January(1)):S99–104. [6] Peppers TA, Jobe CM, Dai QG, Williams PA, Libanati C. Fixation of humeral prostheses and axial micromotion. J Shoulder Elbow Surg 1998;7(July (4)):414–8. [7] Harris TE, Jobe CM, Dai QG. Fixation of proximal humeral prostheses and rotational micromotion. J Shoulder Elbow Surg 2000;9(May (3)):205–10. [8] Matsen III FA, Iannotti JP, Rockwood Jr CA. Humeral fixation by press-fitting of a tapered metaphyseal stem: a prospective radiographic study. JBJS 2003;85(February(2)):304–8. [9] Throckmorton TW, Zarkadas PC, Sperling JW, Cofield RH. Radiographic stability of ingrowth humeral stems in total shoulder arthroplasty. Clin Orthop Relat ResÒ 2010;468 (August (8)):2122–8. [10] Barrett WP, Franklin JL, Jackins SE, Wyss CR. Total shoulder arthroplasty. J Bone Joint Surg Am 1987;69(July(6)):865–72. [11] Cil A, Veillette CJ, Sanchez-Sotelo J, Sperling JW, Schleck CD, Cofield RH. Survivorship of the humeral component in shoulder arthroplasty. J Shoulder Elbow Surg 2010;19(January (1)):143–50. [12] Litchfield RB, McKee MD, Balyk R, Mandel S, Holtby R, Hollinshead R, Drosdowech D, Wambolt SE, Griffin SH, McCormack R. Cemented versus uncemented fixation of humeral components in total shoulder arthroplasty for osteoarthritis of the shoulder: a prospective, randomized, double-blind clinical trial—A JOINTs Canada Project. J Shoulder Elbow Surg 2011;20(June (4)):529–36. [13] Raiss P, Edwards TB, Deutsch A, Shah A, Bruckner T, Loew M, Boileau P, Walch G. Radiographic changes around humeral components in shoulder arthroplasty. JBJS 2014;96(April(7)):e54. che A, Boileau P, Favard L, Le Huec JC, Le vigne C, [14] Godene -Josserand L, Walch G, Edwards TB. Prosthetic replaceNove ment in the treatment of osteoarthritis of the shoulder: early results of 268 cases. J Shoulder Elbow Surg 2002;11(January (1)):11–8. [15] Keener JD, Chalmers PN, Yamaguchi K. The humeral implant in shoulder arthroplasty. JAAOS 2017;25(June (6)):427–38.
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[16] Cil A, Veillette CJ, Sanchez-Sotelo J, Sperling JW, Schleck C, Cofield RH. Revision of the humeral component for aseptic loosening in arthroplasty of the shoulder. J Bone Joint Surg Br 2009;91(January (1)):75–81. [17] Khan A, Bunker TD, Kitson JB. Clinical and radiological follow-up of the Aequalis third-generation cemented total shoulder replacement: a minimum ten-year study. J Bone Joint Surg Br 2009;91(December (12)):1594–600. [18] Casagrande DJ, Parks DL, Torngren T, Schrumpf MA, Harmsen SM, Norris TR, Kelly II JD. Radiographic evaluation of short-stem press-fit total shoulder arthroplasty: short-term follow-up. J Shoulder Elbow Surg 2016;25(July (7)):1163–9. [19] Morwood MP, Johnston PS, Garrigues GE. Proximal ingrowth coating decreases risk of loosening following uncemented shoulder arthroplasty using mini-stem humeral components and lesser tuberosity osteotomy. J Shoulder Elbow Surg 2017;26(July (7)):1246–52. [20] Romeo AA, Thorsness RJ, Sumner SA, Gobezie R, Lederman ES, Denard PJ. Short-term clinical outcome of an anatomic short-stem humeral component in total shoulder arthroplasty. J Shoulder Elbow Surg 2018;27(January (1)):70–4. [21] Schnetzke M, Coda S, Raiss P, Walch G, Loew M. Radiologic bone adaptations on a cementless short-stem shoulder prosthesis. J Shoulder Elbow Surg 2016;25(April (4)):650–7. [22] Schnetzke M, Rick S, Raiss P, Walch G, Loew M. Mid-term results of anatomical total shoulder arthroplasty for primary osteoarthritis using a short-stemmed cementless humeral component. Bone Joint J 2018;100(May (5)):603–9. [23] Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg 2005;14(January (1)):S147–61. [24] Phadnis J, Huang T, Watts A, Krishnan J, Bain GI. Cemented or cementless humeral fixation in reverse total shoulder arthroplasty? A systematic review. Bone Joint J 2016;98(January (1)):65–74. [25] Grey B, Rodseth RN, Roche SJ. Humeral stem loosening following reverse shoulder arthroplasty: a systematic review and meta-analysis. JBJS Rev 2018;6(May (5)):e5. [26] Wieser K, Borbas P, Ek ET, Meyer DC, Gerber C. Conversion of stemmed hemi-or total to reverse total shoulder arthroplasty: advantages of a modular stem design. Clin Orthop Relat Res 2015;473(February (2)):651–60.
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Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/sart
Cemented humeral shoulder arthroplasty: Because it works! Brian Grogana, Daniel J. Songb, and Charles M. Jobinc,* a Department of Orthopedics and Rehabilitation, University of Wisconsin School of Medicine and Public Health, UW Health at The American Center, WI, USA b Elbow and Sports Surgery, Department of Orthopedic Surgery, NYP/Columbia University Medical Center, New York, NY, USA c Department of Orthopedic Surgery, NYP/Columbia University Medical Center, 622 West 168th Street, PH-1117, New York, NY 10032, USA
A R T I C L E I N F O
ABSTRA CT
Key Words:
Durable humeral component fixation in shoulder arthroplasty is important to prevent loos-
Cemented stem
ening. Humeral component designs include metaphyseal fitting, diaphyseal fitting with tra-
Shoulder
ditional stem length, short stem, and stemless designs. Stem geometry helps resist
Arthroplasty
rotational and axial stress. Stem collars may prevent subsidence, and may be smooth for
Humeral
full cementation or textured proximally for bone ingrowth. Ideally, the humeral compo-
Radiolucent lines
nent has solid initial fixation, durable long-term fixation, minimizes humeral stress shield-
Loosening
ing, has low intra-operative complication rates, and can easily be revised. Excellent
Stemless
outcomes can be achieved, but there remain relative indications and contraindications for
Short stem
cementing or press-fitting the humeral component.
Reverse
Ó 2018 Elsevier Inc. All rights reserved.
Uncemented
1. Introduction to the geometry of the proximal humerus Humeral component design and fixation techniques are directly tied to the morphology of the proximal humerus. Modern components are generally modular to account for the wide variability between patients. Textured proximal coating may promote bone ingrowth or ongrowth to create biologic implant fixation, while cementation eliminates this biologic fixation [1]. While fixation is paramount, recreating the geometry of the proximal humerus is important to restore the mechanics of the glenohumeral joint. The arc of the articular surface of the humeral head extends approximately 150°; the head thickness ranges from 12 24 mm and is linked to the humeral head radius of curvature in a 3:4 ratio [2 5]. Work by Robertson and coauthors has demonstrated an average humeral retroversion of 19° (range 9 31) * Corresponding author: E-mail address: [email protected] (C.M. Jobin). https://doi.org/10.1053/j.sart.2018.10.009 1045-4527/Ó 2018 Elsevier Inc. All rights reserved.
and canal diameters ranging from 9 16 mm [2]. When considering the placement of a stemmed humeral component, it is important to note that the proximal humeral endosteal canal is not round, but ellipsoid, with its long axis running from medial to lateral in the axial plane. This axis becomes increasingly retroverted more distally in the humerus. The center of rotation of the humeral head is offset posteriorly by a mean of 2 mm and medially by a mean of 7 mm. There is also an approximately 4-fold tapering of the of the canal from the 1300 mm2 at the surgical neck to 340 mm2 at the diaphysis [2].
2. Humeral stem fixation Stemmed humeral components have long been cemented in the humeral canal. Cement can be placed down the diaphysis to fill the canal all the way to the humeral neck cut to
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provide a complete mantel surrounding the implant (Fig. 1). Alternatively, it can be packed around the metaphyseal aspect of the implant in a more limited partial proximal cementation technique. Both techniques have been shown to be equivalent to press-fitting a smooth-stemmed diaphyseal fitting component with regard to initial axial micromotion [6]. Initial rotational stability in this setting is better with cementation. No difference was seen between partial proximal and full cementation [7]. To improve initial purchase and prevent loosening, humeral components intended to achieve metaphyseal fit have been introduced (Fig. 2). They do not rely on three-point contact between a straight stem and an ellipsoid canal, but instead obtain purchase by reaming the metaphysis to accept an implant of corresponding size [8]. Some implants incorporate a textured surface to promote boney ingrowth or ongrowth. This coating may cover the proximal metaphyseal portion of the implant or extend down the length of the implant to the diaphyseal portion of the stem [9].
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3. Stem loosening Aseptic loosening of standard length humeral components, cemented or press-fit, is fortunately rare. Barrett reported on 44 patients undergoing total shoulder arthroplasty using a cemented humeral component. At an average of 3.5 years of follow-up, only one humeral component had been revised; humeral component survival was 98% in the series [10]. A study by Throckmorton reported zero loosening in 76 patients undergoing total shoulder arthroplasty using a circumferential metaphyseal porous-coated press-fit stem at an average of 52 months of follow-up [9]. Cil and colleagues found that humeral stem loosening occurred in isolation in only 4 of 1,112 (0.03%) of total shoulder arthroplasty cases. Examining revision for any reason, there was 96.2% survival of cemented components and 91.2% survival of noncemented components at 10 year follow-up (p < 0.1) [11]. In a prospective randomized controlled trial of 161 patients, Litchfield found
Figure 1 – Cemented humeral stem during total shoulder arthroplasty. 4 years after cemented humeral stem during TSA without loosening of stem, nor significant stress shielding.
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Figure 2 – Press-fit metaphyseal fitting humeral stem during total shoulder arthroplasty. 2 years after press-fit metaphyseal fitting humeral stem during total shoulder arthroplasty without evidence of calcar resorption, but mild tuberosity stress shielding.
no evidence of humeral loosening in either cemented or noncemented humeral components [12]. Keener and coauthors pooled the results of several large shoulder arthroplasty studies [8,9,11 14]. They found a weighted mean aseptic loosening rate of 0.2% with cemented implants and 0.9% for noncemented implants and an overall revision rate of 2.6% for cemented implants and 7.47% for noncemented implants [15]. Keener also noted that some bias may be inherent in these series, as cemented humeral stems can be difficult to revise and have a significant complication rate [15,16].
4. Radiographic evaluation of humeral stems Radiographic changes and functional outcomes have been studied in standard length cemented and uncemented stems. As described by Denard, stress shielding of the proximal humerus results from sharing of physiologic load between
the remaining humeral bone and the implanted humeral prosthesis. Stress shielding may manifest as tuberosity resorption, cortical thinning, or calcar osteolysis (Fig. 3). It has been linked to humeral implant characteristics such as stem length and diameter fill ratio [1]. Osteolysis may result from stress shielding, but it has also been linked to glenoid polyethylene wear and debris [13]. Glenoid component wear characteristics may introduce confounding variables into the evaluation of stress shielding of the proximal humerus based on humeral implant design and fixation technique. Humeral implants that are circumferentially proximally cemented or coated with an ongrowth surface may be less susceptible to distal particulate-induced osteolysis [13,15]. At long term follow-up, high rates of radiolucent lines can be seen in both cemented (Fig. 4) and uncemented components, but these lines have not been linked to loosening or revision [13,17]. Looking at functional outcomes, the only Level 1 data available suggests that cemented humeral components may
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Figure 3 – Calcar resorption and stress shielding after cemented hemiarthroplasty. Calcar resorption and greater tuberosity stress shielding 6 years after well cemented humeral stem without evidence of loosening.
outperform uncemented non-coated diaphyseal press-fit components at 24 months of follow-up. Cemented components demonstrated a significant improvement in the Western Ontario Osteoarthritis of the Shoulder (WOOS) score over uncemented components. There was no significant difference in the American Shoulder and Elbow Surgeons (ASES) Standardized Shoulder Assessment or McMaster-Toronto Arthritis Patient Preference Disability Questionnaire (MACTAR) [12].
5. Short and stemless humeral stems In recent years, there has been increasing usage of short stem and stemless humeral components. While these implants may
be compatible with cemented fixation, many surgeons are moving toward press-fit implantation of these components [18 21]. The use of short stems may preserve bone stock in the setting of a revision surgery. Stemless components not only preserve bone, but may they be useful in settings where the distortion of native proximal humeral anatomy makes the use of a stemmed humeral component difficult (Fig. 5). Many of these short stem and stemless components also feature ingrowth or ongrowth surface coatings [19]. There is significant design variation in short stem shape, taper, and collar. There are also a variety of metaphyseal engagement mechanisms among the stemless humeral components [1]. Because short-stem and stemless implants are relatively new, little long-term data on loosening and revision is
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with the addition of a proximal ingrowth coating [19]. In their comparison of 34 proximally coated and 34 uncoated implants at an average of 27. 3 months of follow-up, they found a significantly higher incidence of humeral lucency and “at-risk” humeral stems among the uncoated group. No humeral component required revision. Only one stem was found to be loose, and it was in the uncoated group. Romeo reported on the use of a short-stem press-fit humeral component and found 9% of stems to be “at-risk” for loosening on radiographs but no gross loosening or revision for any reason at mean 25 months of post-operative follow-up [20].
6. Reverse shoulder humeral stems Reverse total shoulder arthroplasty was designed to alter the fundamental biomechanics of the shoulder joint to compensate for a deficient rotator cuff. Reverse total shoulder arthroplasty changes the joint center of rotation to maximize the function of the deltoid and minimize stress on the glenoid component [23]. The effects of altered joint compression and shear forces upon loosening and stress shielding of the humeral component of the reverse prosthesis are not completely known [15]. A systematic review by Phadnis of 41 clinical studies including 1455 cemented and 329 uncemented reverse total shoulder arthroplasty humeral components demonstrated equivalent clinical outcomes and no difference in rates of loosening or revision [24]. Uncemented stems (Fig. 6) did have higher rates of non-progressive radiolucent lines and stem migration, while cemented stems had higher rates of acromial fracture, infection, nerve injury, and thromboembolism. A systematic review and meta-analysis by Grey comprised of 65 studies including 1,660 cemented and 805 uncemented reverse total shoulder arthroplasty humeral components revealed no difference in rates of aseptic loosening or revision between the two groups [25]. Figure 4 – Aseptic loosening of cemented humeral stem during hemiarthroplasty for fracture. Aseptic stem loosening 4 years after hemiarthroplasty for fracture with tuberosity resorption, radiolucent lines around the cemented stem. This constellation of findings was concerning for deep infection therefore an open biopsy of the bone-implant interface did not demonstrate infection and a revision reverse replacement was performed 1 month later.
available. However, short-term follow-up results using a grit blasted short-stem press-fit humeral component without a proximal porous coating demonstrated aseptic humeral loosening in 4/73 (5.48%) patients, 2 (2.74%) of whom underwent revision arthroplasty for aseptic humeral loosening. There were radiolucent zones noted on 71% of radiographs at 24 months follow-up [18]. A mid-term follow-up on the same implant by Schnetzke reported a 37% rate of high boney adaptation and a 66% rate of cortical narrowing and osteopenia at the calcar in a group of 66 patients at a mean follow-up of 5.3 years. The authors reported no evidence of humeral component loosening [22]. Morwood and coauthors reported outcomes following the release of an new version of the implant
7. Comparing cemented and uncemented humeral stems While outcomes of anatomic and reverse arthroplasty with both cemented and noncemented humeral components are generally comparable, there exist distinct advantages and disadvantages to selecting a cemented technique. Cementation of the humeral component during shoulder arthroplasty has the advantage of providing immediate fixation with minimal broaching or reaming in patients with poor bone quality. Cement can fill gaps between bone and the humeral component when proximal humeral morphology or bone loss create a bone/prosthesis mismatch [2,8]. A good cement mantle may also prevent osteolysis by excluding glenoid wear debris from the humeral canal [13]. Cement can also serve as a carrier for antibiotics. The use of cement for initial fixation does have disadvantages. It increases operative time and complexity. In the revision setting, cemented stems can be difficult to revise [26]. Retained cement at the time of revision surgery for infection may serve as a nidus for subsequent relapse and treatment failure. The decision to use cement should be based on
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Figure 5 – Stemless hemiarthroplasty. Stemless hemiarthoplasty in a 44 year old man. This design utilizes ingrowth metaphyseal fins. The 2 year radiographic outcomes are encouraging.
careful consideration of each patient’s overall clinical picture and the likelihood of future surgical intervention.
8. Conclusions Immediate solid, durable fixation of the humeral component in total shoulder arthroplasty is key to the long term success. Using standard length stems, both cemented and uncemented stems of a very low rate of aseptic loosening and revision. Osteolysis may occur in response to stress shielding proximal to cemented or large diameter press-fit humeral components, but glenoid wear likely plays a role in bone resorption as well. Short stem and stemless components have theoretical advantages, but long-term data is limited and early reports suggest high rates of loosening and radiographic changes with some implants. Data on reverse total
shoulder arthroplasty suggests that cemented and uncemented humeral components both perform well. Surgeons should recognize the relative indications and contraindications for the use of a cemented humeral component and allow individual case characteristics to guide clinical decision making.
Disclosures This study did not receive any grant or research support. Dr. Charles M Jobin is a consultant for Acumed, DePuy-Synthes, Wright-Tornier, Zimmer-Biomet and is Deputy Editor for JAAOS. Dr. Brian Grogan and Dr. Daniel J. Song, and their immediate families, and any research foundation with which they are affiliated have not received any financial or
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Figure 6 – Press-fit reverse humeral stem. Press-fit reverse shoulder arthroplasty humeral stem with metaphyseal ingrowth and diaphyseal fill.
other benefits from any commercial entity related to the subject of this article.
B I B L I O G R A PH Y
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arthroplasty: review and recommendations for evaluation. J Shoulder Elbow Surg 2018. Feb 5. [2] Robertson DD, Yuan J, Bigliani LU, Flatow EL, Yamaguchi K. Three-dimensional analysis of the proximal part of the humerus: relevance to arthroplasty. JBJS 2000;82(November (11)):1594–602. [3] Iannotti JP, Gabriel JP, Schneck SL, Evans BG, Misra S. The normal glenohumeral relationships. An anatomical study of one hundred and forty shoulders. J Bone Joint Surg Am 1992;74(April(4)):491–500.
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