When bone preservation is put to the test: what performance evidence suggests about the AETOS◊ Shoulder Meta Stem

Key takeaways

• Shoulder arthroplasty is rising (reported 6–15% annual growth), increasing the importance of revision-friendly, bone-preserving fixation.¹
• Cementless press-fit stems can alter load distribution and in the context of stress shielding when distal fixation dominates.^2,3*
• AETOS Meta Stem is designed for proximal metaphyseal engagement with minimal distal canal fill to reduce distal stress transfer.^2–4*
• In modelling across healthy and osteoporotic bone, AETOS Meta Stem showed greater proximal strain-energy distribution and higher rotational stiffness vs a metaphyseal referencing competitive stem.^4*‡
• Varus-loading simulations showed substantially lower load transfer with AETOS Meta Stem —consistent with a proximal-load philosophy vs a metaphyseal referencing competitive stem.^4*‡
  

So what do these performance data mean when you’re choosing a humeral stem strategy?

If you’re prioritizing bone preservation and future revision options, the question isn’t only whether a stem “fits” today—it’s where it loads bone over time. AETOS Meta Stem’s metaphyseal-first engagement is intended to keep load proximal and limit distal stress transfer, while supporting rotational stability (including in porotic bone).^2–4

In practical terms, shifting load away from the metaphysis can contribute to stress shielding and proximal bone loss over time—changes that may compromise fixation patterns and reduce bone stock available for future revision.^2,3,6

What’s the challenge with cementless humeral fixation?

Cementless stems are often selected for bone-preserving intent and ease of revision. But “press-fit” is not one-size-fits-all: where the stem contacts the canal can shift the load path distally. That distal-dominant transfer is one of the mechanical patterns discussed in relation to stress shielding and proximal bone loss—exactly what surgeons want to avoid in younger patients and in those likely to need revision.^2,3,6

This is why design features that intentionally bias fixation toward the metaphysis—while limiting diaphyseal engagement—are clinically relevant, and why modelling/FEA can be informative for comparing load transfer.^3,4

Evidence in Focus: performance testing at a glance

The Evidence in Focus summary reports virtual implantation, 3D canal filling analyses, and finite element analysis (FEA) comparing AETOS Meta Stem with a metaphyseal referencing competitive stem. Endpoints included canal filling ratios (overall and distal), cancellous strain-energy volume (a proxy for how much metaphyseal bone participates in load), rotational stiffness, and varus-loading behavior in healthy and osteoporotic bone models.^2–4

1. Loading bone where it matters: proximal engagement with minimal distal canal fill

Across endpoints, the pattern is distal restraint. In the testing matrix, AETOS Meta Stem (size 2) reported a lower filling ratio (24%) versus the comparator (35%). The model also reported ~32% of the implant residing in the epiphysis with approximately 0% extending into the diaphysis—an implantation pattern intended to reduce distal stress transfer.^2,4

To put the distal-fill finding in context, the Evidence in Focus summary also reports additional modelling endpoints (strain-energy distribution, torsional stiffness, and varus-loading behavior) that help describe how a metaphyseal-first construct may translate into proximal loading and stability.^2,4

Lower diaphyseal fill is commonly pursued to reduce the conditions associated with stress shielding. In this summary, AETOS Meta Stem is also reported to maintain a canal filling ratio <0.7*, a threshold described as being at risk of stress shielding.⁶

2. Performance across bone qualities (including osteoporotic models)

Osteoporosis increases implant-related complication risk after shoulder arthroplasty, raising the bar for cementless fixation.^7,8 In osteoporotic models, AETOS Meta Stem maintained proximal load and rotational stability, aided by fin geometry and an angular stem design.⁴
A practical signal: <8% of total force transferred distally with AETOS Meta Stem versus >30% with the comparator in reported scenarios. Strain-energy volumes were also higher for AETOS Meta Stem in metaphyseal cancellous bone (healthy: 3,178 vs 1,924 mm³; porotic: 5,450 vs 4,715 mm³).⁴

3. Rotational stability without “buying” fixation distally

Rotational stability is central to reliable metaphyseal fixation. In these simulations, AETOS Meta Stem showed higher rotational stiffness (10 vs 7 Nm/deg) while keeping distal load low under varus angulation (3% vs 21%).⁴
FEA also reported stability gains linked to fin geometry (e.g., anterior–posterior fins increasing stability by 29% vs comparator; sagittal fins increasing torsional stiffness by 45% vs AETOS Meta Stem analysed without fins), supporting stability without relying on distal canal contact.⁴

A question worth asking in every case

When you seat a cementless stem, immediate tactile feedback matters—but the longer-term story is the load path. If the goal is to preserve proximal bone stock and keep revision options open, performance evidence showing proximal load transfer, low distal fill, and rotational stability achieved without relying on distal canal fixation can help inform stem choice.^2–4

About the AETOS Meta Stem 

AETOS Meta Stem is designed for proximal metaphyseal engagement, with features such as a tapered inlay design, plasma-spray porous titanium coating, and cruciate/sagittal fin geometry intended to prioritize metaphyseal loading and enhance rotational stability while minimizing diaphyseal engagement.^3,4

Find out more about the AETOS Shoulder System:

This information is for educational and informational purposes only and may not be appropriate for all jurisdictions. This information does not constitute and is not intended to be medical advice. Smith+Nephew does not provide medical advice. It is the treating health care provider’s responsibility to determine the best course of treatment for their patient based upon their professional medical judgment. For detailed information, including indications for use, contraindications, effects, precautions and warnings, please consult the product’s Instructions for Use (IFU) prior to use.