How to choose a humeral component in shoulder arthroplasty: ASES Podcast 155

Hat's off to Drs Chalmers and Waterman for yet another outstanding ASES podcast: Episode 155, in which they were joined by Drs Athwal, Cuff and Hatzidakis to discuss fixation of humeral arthroplasty components: "standard" length stems (100-150 mm), short stems (60-90 mm) and stemless designs. 

Here are some takeaways from that presentation coupled with some additional thoughts from the U.W..

(1) The evolution in humeral components is attributed to (a) mitigation of complications (periprosthetic fracture, stress shielding from high canal-filling ratios, early loosening from certain ingrowth surfaces), (b) matching competitor features, and (c) responding to market forces.

The Standard Stem

(2) A standard length stem uses the canal as an alignment guide. It can be stabilized in the canal by (a) a bony ingrowth surface, (b) cement, or (c) reaming to a tight diaphyseal fit, reaming that, in any case, removes cortical bone asymmetrically and unpredictably. [7]. As discussed later in this post, the standard stem can also be stabilized in the canal by impaction grafting. Much of the stress-shielding literature conflates two different things — stem length and canal fill — and they are not the same. Proximal stress shielding tracks with the filling ratio — how much of the canal the implant occupies and how much load it diverts away from proximal bone — far more than with the absolute length of the stem. [9,10]. A long stem that fills the canal shields bone; a long stem that sits loosely in the canal, transferring load through impacted cancellous bone, need not. 

(3) Osteoporosis or altered humeral anatomy may drive the use of a longer stem for better fixation and durability.

The Short Stem

(4) The short stem depends on loading at the metaphyseal level — in bone of variable shape and quality — making both fixation and orientation challenging.

CT of the proximal humerus showing the thin metaphyseal cortex 

The short stem may not have enough leverage to reduce loosening.

Canal filling can lead to stress shielding

And periprosthetic fracture

The absence of the control provided by a standard length stem 

can lead to malpositioning of a short stem

(5) Stemless implants depend on fixation at the anatomic neck, where a thin cortical shell surrounds cancellous bone. Bone density at this level is of variable quality, especially in patients in the arthroplasty age range. While some surgeons claim “100% stemless,” that claim is not realistic for every patient having shoulder arthroplasty. 

AP radiograph with the anatomic-neck fixation zone annotated

The big question about stemless is how a surgeon decides, in a given patient, whether good fixation can be achieved. Preoperative imaging may give some clues, but it comes down to the intraoperative findings. Some have advocated the “thumb” test;

a more reliable approach is to insert the trial nucleus and determine whether it is solid. When it is not solid because of “mushy” cancellous bone, the options are limited. In our experience, adding cancellous graft at the anatomic neck does not rescue fixation: the site is already failing in cancellous bone, and loose graft packed against soft cancellous bone has nothing rigid to lock against. 

The ability to improve fixation with longer fins is likewise limited; upsizing the trial to gain purchase can risk the lateral cortex.

 

It is also worth noting that even when stemless fixation is achieved, adaptive bone changes are common; at short-to-mid term, however, they have not reliably correlated with loosening or worse function.[6,8]

So in the real world, the stemless-loving surgeon needs a Plan “B” when trial fixation is unstable. Conversion to a stemmed component is the most attractive option. One caveat: if the problem is mushy cancellous bone, fixation of a short stem can itself be challenging — a fatter stem versus bone graft, and the same question of how to assure durability in the desired position.

Avoiding Trouble with the Stemless

Be aware of common technical mistakes - assure complete head resection and avoid excessive varus or valgus. 

Insufficient head resection

Varus cut

The free-hand cut is key.

Revision

(6) Two concerns arise when the humeral component needs revision. First, removal of a well-fixed implant can risk fracture of the tuberosity, bone loss, and shaft fracture, and may require a humeral osteotomy or window. Second, although some humeral implants are “convertible” (the humeral fixation system stays in place), retaining the implant only makes sense if it is well fixed at an appropriate height and acceptable version. One podcast participant reported that 25–40% of nominally convertible stems cannot actually be converted in practice. Taken together, the routine use of “convertible” implants seems unattractive.

Malrotation

Too low or too high position of the stem

Another approach

(7) Our experience is that secure, safely revisable humeral component fixation can be achieved with a smooth, standard-length stem set at a small filling ratio and fixed with impaction autografting — using bone from the resected humeral head that one of our fellows named “God’s Own Glue” (see "Procrustean Method") [2,3]. The graft is impacted between a smooth stem and the endosteal cortex, where it stabilizes the implant at the time of surgery, rather than relying on a bony ingrowth surface, cement, or a tight diaphyseal press fit. [4]. A low filling ratio protects the humerus from stress shielding. Because the stem is deliberately undersized, load is transferred through grafted cancellous bone rather than bypassed down a canal-filling implant — addressing stress shielding at the variable that drives it. [9,10]. 

In 48 ream-and-run and 78 total shoulder arthroplasties using a smooth, standard-length impaction-grafted stem, two-year radiographs showed adaptive changes that were generally minor and not associated with component shift or subsidence. Inserted this way, a smooth standard-length stem offers secure, bone-preserving fixation providing results can serve as a basis for comparison for other component designs and fixation methods. [5]. 

In a consecutive single-surgeon series of 458 anatomic total shoulder arthroplasties using this construct (mean follow-up 9.2 years; 114 shoulders beyond ten years), Simple Shoulder Test scores improved from 3.3 to 9.2 and were sustained — never declining by more than the MCID — past ten years. The overall revision rate was 2.6% (12 of 458). None of the revisions were performed for a humeral-component cause: there was no humeral component loosening, no periprosthetic fracture, and no stem-related failure.[11] 

 A low filling ratio protects the humerus from stress shielding

 

Two year followup

Six year followup

Impaction grafting with a low filling ratio avoids incomplete seating of the humeral stem (humerus captivus)

Impaction grafting a standard stem in revising a failed short stem

Impaction grafting a thin long stem  in humeral deformity

Impaction grafting after fracture fixation

Impaction grafting a thin standard stem enables easy, safe removal followed by new implant insertion should revision be necessary.

Thus "revisability" does not require "convertibility"

Returning to the observation stated at the beginning of this post: humeral component evolution is attributed to (a) mitigation of complications, (b) matching competitor features, and (c) responding to market forces. 

Impaction grafting of a thin, smooth stem is an approach for addressing  periprosthetic fracture, stress shielding from high canal-filling ratios, and early loosening. It is not driven by market forces. Impaction grafting can be used with any standard length stem (anatomic or reverse) combined with freely available autograft from the patient’s own humeral head that would otherwise be discarded.

Should we be thinking straight?

Beauty in Simplicity

Tundra Swan

Union Bay Natural Area

Disclosure. The author has no financial relationship with any manufacturer of the orthopaedic devices discussed in this post.

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References of interest

1. The ASES Podcast (American Shoulder and Elbow Surgeons), Episode 155: standard, short, and stemless humeral components and convertible designs. Available at: https://www.youtube.com/watch?v=q_s_g8oQgPg

2. Razfar N, Reeves JM, Langohr GDG, Willing R, Athwal GS, Johnson JA. Comparison of proximal humeral bone stresses between stemless, short stem, and standard stem length: a finite element analysis. J Shoulder Elbow Surg. 2016;25(7):1076–1083. doi:10.1016/j.jse.2015.11.011. PMID 26810016.

3. Reeves JM, Langohr GDG, Athwal GS, Johnson JA. The effect of stemless humeral component fixation feature design on bone stress and strain response: a finite element analysis. J Shoulder Elbow Surg. 2018;27(12):2232–2241. doi:10.1016/j.jse.2018.06.002. PMID 30104100.

4. Synnott S, Langohr GDG, Reeves JM, Johnson JA, Athwal GS. The effect of humeral implant thickness and canal fill on interface contact and bone stresses in the proximal humerus. JSES Int. 2021;5(5):881–888. doi:10.1016/j.jseint.2021.05.006.

5. Aibinder WR, Uddin F, Bicknell RT, Krupp R, Scheibel M, Athwal GS. Stress shielding following stemless anatomic total shoulder arthroplasty. Shoulder Elbow. 2023. doi:10.1177/17585732211058804. PMID 36895609.

6. Raiss P, Edwards TB, Deutsch A, Shah A, Bruckner T, Loew M, Boileau P, Walch G. Radiographic changes around humeral components in shoulder arthroplasty. J Bone Joint Surg Am. 2014;96(7):e54. doi:10.2106/JBJS.M.00378. PMID 24695931.

7. 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;27(6):1139–1147. doi:10.1016/j.jse.2017.12.020. PMID 29422391.

8. Sheth MM, Kahsai EA, Yang J, Whitson AJ, Matsen FA III, Hsu JE. What is the clinical importance of radiographic changes around the humeral component in anatomic shoulder arthroplasty? A minimum 4-year follow-up study. J Shoulder Elbow Surg.2025;34(8):1877–1885. doi:10.1016/j.jse.2024.11.024. PMID 39800107.

9. Denard PJ, Hsu JE, Whitson A, Neradilek MB, Matsen FA III. Radiographic outcomes of impaction-grafted standard-length humeral components in total shoulder and ream-and-run arthroplasty: is stress shielding an issue? J Shoulder Elbow Surg.2019;28(11):2181–2190. doi:10.1016/j.jse.2019.03.016. PMID 31272887.

10. Kim SC, Park JH, Bukhary H, Yoo JC. Humeral stem with low filling ratio reduces stress shielding in primary reverse shoulder arthroplasty. Int Orthop. 2022;46(6):1341–1349. doi:10.1007/s00264-022-05383-4.

11. Lee M, Chebli C, Mounce D, Bertelsen A, Richardson M, Matsen FA III. Intramedullary reaming for press-fit fixation of a humeral component removes cortical bone asymmetrically. J Shoulder Elbow Surg. 2008;17(1):150–155. doi:10.1016/j.jse.2007.03.032. PMID 18029200.

12. Boorman RS, Hacker SA, Lippitt SB, Matsen FA III. A conservative broaching and impaction grafting technique for humeral component placement and fixation in shoulder arthroplasty: the Procrustean method. Tech Shoulder Elbow Surg.2001;2(3):166–175. doi:10.1097/00132589-200109000-00004.

13. Hacker SA, Boorman RS, Lippitt SB, Matsen FA III. Impaction grafting improves the fit of uncemented humeral arthroplasty. J Shoulder Elbow Surg. 2003;12(5):431–435. doi:10.1016/s1058-2746(03)00053-3. PMID 14564262.

14. Lucas RM, Hsu JE, Gee AO, Neradilek MB, Matsen FA III. Impaction autografting: bone-preserving, secure fixation of a standard humeral component. J Shoulder Elbow Surg. 2016;25(11):1787–1794. doi:10.1016/j.jse.2016.03.008. PMID 27262410.

15. Lee et al. Stress shielding effects of short stem alignment and bone density in reverse shoulder arthroplasty. J Orthop Res. 2026. doi:10.1002/jor.70140.

16. Vasiliadis AV, Giovanoulis V, Lepidas N, Bampis I, Servien E, Lustig S, Gunst S. Stress shielding in stemmed reverse shoulder arthroplasty: an updated review. SICOT J. 2024;10:37. doi:10.1051/sicotj/2024029.

17. Ritter D, Raiss P, Denard PJ, Werner BC, Müller PE, Woiczinski M, Wijdicks CA, Bachmaier S. Volumetric humeral canal fill ratio effects primary stability and cortical bone loading in short and standard stem reverse shoulder arthroplasty: a biomechanical and computational study. J Imaging. 2024;10(12):334. doi:10.3390/jimaging10120334.

18. Kramer M, Olach M, Zdravkovic V, Manser M, Raiss P, Jost B, Spross C. The effects of length and width of the stem on proximal humerus stress shielding in uncemented primary reverse total shoulder arthroplasty. Arch Orthop Trauma Surg. 2024. doi:10.1007/s00402-023-05129-w.

19. John PB, Nageswaran S. Mechanobiological evaluation of solid and multiple porous humeral stem architectures in reverse shoulder arthroplasty based on design and materials: a finite element study. Front Bioeng Biotechnol. 2026;13:1675726. doi:10.3389/fbioe.2025.1675726.

20. Takayama K, Ito H. Association between the canal filling ratio and bone resorption in trabecular metal stems in reverse total shoulder arthroplasty: a radiographic analysis using tomosynthesis. JSES Int. 2024;8(5):1077–1086. doi:10.1016/j.jseint.2024.05.010.