Stemless versus stemmed modular implants for anatomic TSA


Jaicharan Iyengar, MD
Alpine Orthopaedic Medical Group, Inc.

There is a general trend in shoulder arthroplasty in recent years away from traditional diaphyseal-filling humeral stem implants towards short-stem metaphyseal stems, and now, stemless humeral components. The reasons for this typically include a desire for bone conservation for potential future revision procedures, mitigating metaphyseal stress shielding and secondary bone loss, and minimizing bone removal during the index procedure. (Zhou et al, JSES 2022)

Having said that, a thorough understanding of these newer humeral options is important to apply the correct implant rationale to the individual needs of the patient. The Equinoxe shoulder system was one of the early modular platform designs to offer easy convertibility between anatomic and reverse humeral components without necessitating stem removal. This convertibility feature has been preserved in the newer Equinoxe short stem components and confers a significant advantage in facilitating revision procedures with respect to operative time, blood loss and intra-operative complications (Crosby et al, JBJC 2017)

On the other hand, the use of humeral stemless components offers flexibility to restore humeral anatomic parameters and manage proximal humeral deformity, when present (Pinto et al, JSES 2019). It also offers the most bone sparing strategy and has been shown to potentially save operative time during index TSA procedures (Anastasio et al, Seminars 2021). The downside of the stemless design is losing the modularity to convert the humeral component to a reverse tray without removing the cage segment. Also, the concentric design of the stemless head does not allow for the eccentric head placement offered by the Equinoxe replicator plate. A common question that arises is whether these trade-offs are worth it from the perspective of technical ease of revision.

My personal trend has been towards the use of humeral stemless components in most anatomic TSA cases. I have found that in physiologically younger patients with intact rotator cuff function, the stemless design offers an excellent restoration of humeral anatomy, ease of implantation and removes the geometric constraints of using a stem in cases of proximal humeral deformity. (Sears et al, JSES 2023, Zhou et al, JSES 2022). In the few cases of needing to revise stemless humeral implants, the ease of removal due to streamlined removal instrumentation and ample remaining bone stock have allowed for retaining press-fit stability during most revision cases (Lazarus et al, JAAOS 2018).

Additionally, in cases of long-standing implantation of a well-fixed humeral stem in anatomic TSA with secondary rotator cuff failure, I have often found it necessary to revise the humeral resection level rather than rely on the existing stem position. This is due to progressive soft tissue contracture and proximal migration of the humeral component, which requires both soft tissue releases and bony revision to decrease overall deltoid tension. In these cases, the advantage of a convertible stem is sometimes not realized at the time of revision.

In my current practice, I reserve the use of stemmed convertible humeral components in anatomic TSA to patients over age 70, or cases with some concern for rotator cuff integrity that could result in the need for early revision to a reverse shoulder arthroplasty within 3-5 years. In addition, the expectation in this elderly population is that the metaphyseal bone quality necessary for stemless implantation may be compromised. While these principles are true on a population level, this also represent an opportunity for using machine-learning predictive algorithms such as Predict+ to help to quantify the risks of early revision to aid in the decision-making process in an individual patient (Kumar et al, JSES 2021).

As with all surgical decision making, there are many valid perspectives on this, and ultimately it is up to the arthroplasty surgeon to be thoughtful about these choices and make the call on behalf of the patient. Fortunately, whether you decide on a traditional stem, short stem or stemless humeral component, you will find that the Equinoxe system has an option for every surgeon.