Place of the stemless shoulder implant in 2023

Working with the TESS Group, we first envisioned stemless shoulder implants exactly 20 years ago, at the initiative of Biomet France.

The designers used version 1 of the TESS Implant, which had a modular and convertible design, for a total of 105 procedures throughout 2003, then assessed the results the following year (Fig. 1). In 2005, version 2 of the definitive TESS system was launched (Fig. 2). Thanks to satisfactory clinical outcomes at 5 years, [1] Huguet D, Declercq G, Rio B, Teissier J, Zipoli B. Results of a new stemless shoulder prosthesis: Radiologic proof of maintained fixation and stability after a minimum of three years follow-up. J Shoulder Elbow Surg 2010; 19, 847-852 most companies gradually began including a stemless design in their implant range.

Having established the ‘stemless’ concept, we then went on to develop fourth generation shoulder implants which remain a French invention.

20 years ago, the stemless concept was born

The cup arthroplasty, first suggested by Steve Copeland in 1986, [2] Levy O, Copeland SA. Cementless surface replacement arthroplasty of the shoulder. 5- to 10-year results with the Copeland mark-2 prosthesis. J Bone Joint Surg Br. 2001;83:213-21. was appealing due to the bone sparing and good outcomes for a humeral hemiarthroplasty. However, preserving the head made it extremely difficult to access the glenoid cavity and it was impossible to ensure correct implantation of the glenoid component for a total arthroplasty. The stemless concept is based on an implant impacted into the superior end of humerus after resecting the head. It comprises a large six-branched anchor designed for epiphysometaphyseal fixation. Developmental anatomic analysis of the humeral head reveals that the epiphysis is formed of three ossification centres (humeral head, greater tuberosity and lesser tuberosity) which fuse at age 7 to create a common epiphyseal mass; the funnel joining this mass to the diaphysis at the surgical neck forms the metaphysis (Fig. 3).

This method of epiphysometaphyseal fixation then evolved into four main types, depending on the company:

• Central post with impacted wings or arcs
• Screwed central post
• Impacted box
• Box + central post.

Whether coated with sandblasted titanium, porous titanium or calcium hydroxyapatite, the fixation systems for these implants are designed to obtain a good primary press-fit, bearing in mind that bone density is optimum in the first centimetre beneath the head cut and densest in the outer ring (1cm) rather than in the middle. [3] Reeves JM, Athwal GS, Johnson JA. An assessment of proximal humerus density with reference to stemless implants. J Shoulder Elbow Surg. 2018; 27:641-649. doi: 10.1016/j.jse.2017.09.019. (Fig 7).

The imprints left in the epiphysis by these various stemless designs show the bone sparing compared to designs with stems, even short ones (Fig. 8).

Stemless implants available in 2023

After presenting the outcomes of the TESS implant, we witnessed a first wave of stemless designs comprising the Eclipse Arthrex in 2006, the Affinis Short Mathys in 2008, the Simpliciti Tornier in 2010, and the Sidus Zimmer in 2012. They were all available in an anatomical version only (Fig. 4).

This was followed by a second wave of stemless implants that could be converted for use in both anatomical and reverse procedures: the Easytech from FX Solutions in 2012, the Nano Biomet in 2013, and the SMR S from Lima in 2014 (Fig. 5).

Finally, the third and most recent waves of stemless designs, exclusively anatomical, comprised the Global Icon DePuy in 2017, the Equinoxe Short from Exactech in 2018, the Isa Stemless from Move-Up in 2019, and the CS Edge from DJO in 2020 (Fig. 6).

In 2008, Offer LEVY proposed a stemless reverse implant dubbed Versio which, in fact, was not truly stemless because it had a tiny stem that went into the medullary canal. Keen to jump on the stemless bandwagon it had, inadvertently, invented the short stem shoulder replacement (Fig. 9).

Currently the global stemless implant market is represented by the following main companies:

• Zimmer-Biomet (Tess, Nano, Sidus) 32%
• Lima (SMR S) 27%
• Mathys (Affinis S) 26%
• Arthrex (Eclipse) 22%
• FX Solution (Easy-Tech) 20%
• Move-Up (Isa) 9%
• Tornier/Stryker 8%

Globally, sales figures are easily dominated by anatomical designs, with Lima selling 44% stemless TSAa (anatomical) vs. 9% stemless TSAr (reverse). Looking just at France, the birthplace of stemless, these figures from Lima are different yet again: 84% stemless TSAa vs. 43% stemless TSAr. Osteonecrosis of the humeral head is a good indication for a stemless implant because resurfacing the humeral head is a simple and minimally-invasive procedure. Likewise, a resurfacing hemiarthroplasty may be indicated for primary concentric osteoarthritis of the shoulder in patients under 50 if the glenoid is in good condition (Fig. 10).

Malunion of the proximal humerus, if recent enough to have not affected the glenoid cartilage, is again a good indication: a stemless humeral implant makes it possible to restore the humeral head without any of the constraints caused by offsets or tuberosity transfer (Fig. 11).[4] Ballas R, Teissier P, Teissier J. Stemless shoulder prosthesis for treatment of proximal humeral malunion does not require tuberosity osteotomy. Int Orthop. 2016; 40:1473-9. doi: 10.1007/s00264-016-3138-y.

What is the ideal indication for a stemless anatomical total replacement?

Concentric osteoarthritis in a young subject is the perfect indication for stemless TSAa because there will be good-quality bone stock and a future revision will be made easier by the use of a stemless design. Longer survival can also be achieved by using a hybrid glenoid component to avoid the need for cement (Fig. 12).

Post-instability osteoarthritis, which usually occurs in relatively young subjects with good quality bone, is a good indication for a minimally-invasive anatomical TSA. A universal metaglene component should be recommended so that it can be converted to a reverse implant, should the instability recur or should there be loosening of subscapularis weakened by a previous bone block (Fig. 13).

What is the ideal indication for a stemless reverse tsa?

Osteoarthritis with rotator cuff tear in a young subject is a good indication for a reverse replacement because the absence of a stem makes the procedure less invasive (Fig. 14). Complex malunion can also be treated with a stemless reverse TSA, since the procedure removes the need for any diaphyseal or tuberosity transfer thus avoiding any corrective osteotomy which is rarely beneficial (Fig. 15).

One of the benefits of stemless is the ability to freely modify the neck-shaft angle, which we initially recommended at 150° but now advise 135° or 140° to avoid notching, improve rotational range and achieve a better shoulder-humerus arch to ensure a good balance between humeral lateralisation and lowering (Fig. 16).

What are the other indications?

Minimally-invasive conversion of TSAa to TSAr in case of cuff failure following stemless anatomical arthroplasty: if a conversion to reverse is required, it can sometimes be possible to keep the stemless implant, especially if either or both of the humeral and glenoid components are universal. If the humeral component is not convertible, its mandatory removal does not preclude the use of another stemless implant, provided the epiphyseal bone has not been overly weakened (Fig. 17).

De-escalation during revision of a poorly-positioned humeral stem in a young subject is another option offering elegant simplicity. The cement sheath can even be left in place provided there is no sepsis (Fig. 18).

What are the advantages of stemless implants?

There are four main advantages:

• Bone sparing.
• Simple procedure, without the constraints of offsets and any dysmorphia or epiphyseal malunion.
• No stem-related issues such as incorrect positioning, fractures, stress shielding (Fig. 19).
• Easier future revisions with no accessory procedures or humerotomy, with conditions comparable to those of a primary implant (Fig. 20).

The secondary advantages include shorter operating time (11 minutes), less bleeding (1g) and a reduced risk of infection.[5] Sakek F…Obert L, Loisel F. Assessment of intraoperative bleeding in reverse shoulder arthroplasty With or Without a stem. RCOT Elsevier vol108 Mai 2022

In case of a subsequent fracture, standard osteosynthesis can be used, not hampered by the presence of a stem (Fig. 21).

Mediocre bone quality caused by long-term steroid therapy, osteoporosis and polyarthritis are contraindications to the use of a stemless design due to the risk of loosening or stress fractures (Fig. 22). Age is not in itself a limiting factor, provided there is sufficient quality bone stock.[6] Keith M Baumgarten. L’arthroplastie totale de l’épaule sans tige est-elle indiquée chez les patients agés ? JSES 2023. 32(2) 260-268

Insufficient epiphysometaphyseal bone stock is a limitation for stemless. The bone walls surrounding the humeral implant must be solid and encompassing. When preparing the glenoid cavity, the posterior spacer used to push back the humeral head can sometimes damage the anterior wall of the humeral epiphysis, creating the need for a stem.

Mechanical overload in heavy manual workers or large arms, especially in certain women, dictate caution with stemless implants (Fig. 23).

Some young surgeons may find it tricky to fit a stemless implant and encounter two common risks: varus positioning or over-stuffing due to an insufficient cut motivated by a desire for bone sparing. The use of a guide stem can help with restoring an anatomical humeral head.[7] Rayan M Cox. Restauration radiologique de la tête humérale après prothèse totale d’épaule - La tige fait elle la différence ? JSES 2021 ; 30 ; 51-56

Finally, stemless implants have no place in trauma settings where diaphyseal fixation with a stem is essential to restore a humeral head above the fracture.

Discussion

With anatomical implants, the most long-standing models (TESS and Eclipse) have equivalent long-term outcomes to stemmed designs. [8], Collin Ph, Matsukawa T, Boileau P, Brunner U, Walch G. Is a stem useful in anatomic total shoulder arthroplasty ? International Orthopedics (SICOT) Jan 2017 DOI 10.1007/00264-016-3371-4[9] Magosch Petra, Lichtenberg Sven, Habermayer Peter : Suivi du remplacement de la tête humérale sans tige dans la prothèse anatomique d’épaule : étude prospective JSES 2021, 7, 343-355

A recent meta-analysis of 962 patients reported comparable functional outcomes and complication rates for stemmed and stemless implants. [10] Liu Y Eva et al. Prothèse totale d’épaule anatomique : Revue systématique et méta-analyse 962 patients. JSES 2020 sept 29. 9. 1928-1937

Overall, whatever the fixation method used - flanged post, screwed post, box etc. - and whatever the coating type (HAP, sandblasted Ti, porous Ti), stemless anatomical implants are completely reliable.

As for reverse procedures which are limited by much greater mechanical constraints, few companies offer stemless reverse models.

Inlay designs such as the TESS and Lima SMR S give satisfactory mid and long-term outcomes. [11], Adjibade D, Clark Y, Wiater J M et al. Prothèse totale d’épaule inversée sans tige : une revue systématique. JSES may 2022- 5 – 1083-1095[12] Kostretzis L, Papadopoulos P, Stemless reverse shoulder arthroplasty : a systematic review of contemporary literature, Musculoskeletal surgery 2021 apr 17 Istituto Rizzoli Onlay models give varying results: the Nano Revers from Zimmer-Biomet, introduced in 2013, was recalled in 2017 due to tilt and loosening [13] Galhoum S Mohamed et al. Anatomic and reverse stemless shoulder arthroplasty : fonctional and radiological evaluation JSEA 2022 vol 6. 1-10 The Easytech reverse onlay from FX Solutions, launched in 2012, also initially had problems with tilt and poor osseointegration, which appear to have been resolved by changing the cut from 135° to 145° and a symmetric PE (Fig. 24).

There will soon be only two companies offering reverse stemless models because Zimmer-Biomet will shortly be halting production of its TESS for commercial reasons: The Lima SMR S, an inlay model made convertible thanks to a handy peripheral socket, and the Easytech from FX, an onlay design that can be converted using a central socket. There are strict criteria for the reliability of these two stemless reverse models, which require good bone stock and skilled implantation by an experienced surgeon.

Conclusion

Based on a recent meta-analysis by Joost Willems (2021) of stemless implants covering 1944 patients: [14] Willems I P Joost et al. Results of stemless shoulder arthroplasty. A systematic review and meta-analysis. EFORT Open Rev. 2021 Jan 4;6(1):35-49. doi: 10.1302/2058-5241.6.200067. eCollection 2021 Jan.

Twenty years since it was first introduced, the so-called fourth-generation stemless shoulder implant has found its place in the treatment arsenal for shoulder arthroplasty.

Stems are usually unnecessary for anatomical procedures.

For a reverse replacement, stemless is only feasible if there is good bone stock and a skilled surgeon, preferably using an inlay model.