An active man in his mid 50s presented with pain and stiffness in his left shoulder and these x-rays. The axillary "truth" view showed the humeral head centered on an A2 glenoid.

Without preoperative CT or 3D planning, he underwent an anatomic total shoulder arthroplasty with a stemless humeral component (diameter of curvature 50, thickness 18 mm). A standard glenoid component was inserted without attempting to change glenoid version. The shoulder was stable on the "shake and bake" test.

He regained excellent comfort and function. 6 months later he presented with pain and stiffness in the right shoulder and the x-rays below. The axillary "truth" view showed the humeral head posteriorly decentered on a retroverted B2 glenoid.

Without preoperative CT or 3D planning, he underwent an anatomic total shoulder arthroplasty. A standard glenoid component was inserted without attempting to "correct" glenoid version. While many shoulders with this amount of posterior decentering are stable with standard humeral head components, on trialing a stemless humeral component (diameter of curvature 50, thickness 18 mm and then a diameter of curvature 50, thickness 20 mm ) this shoulder was posteriorly unstable on the "shake and bake" test. The arthroplasty was quickly and easily converted to a short stemmed implant using an anteriorly eccentric humeral head with a diameter of curvature 50, thickness 18 mm.

This provided excellent posterior stability without excessively tightening the shoulder.

For anatomic total shoulder arthroplasty, our default option is the stemless humeral implant because of the efficiency of the procedure and the ability to position the humeral head without being concerned about the stem. Our two indications for a stemmed implant are (1) the need for an eccentric humeral head component and (2) soft bone in the proximal humerus. Neither of these can be reliably determined prior to surgery.

In performing an anatomic total shoulder, the proximal humerus is lateralized from its preoperative position by the addition of the thickness of a prosthetic glenoid component. Thus, especially in shoulders that are tight preoperatively, a humeral implant with less than "anatomic" height may be needed to avoid over tightening the joint (see this link). Surgeons should be aware of the available head geometries of the implant system they are using.

That's our approach. Let's take a look at what the 2023 and 2024 literature has to say about stemless anatomic arthroplasty.

Stemless anatomic total shoulder arthroplasty is associated with less early postoperative pain "there were no differences in pain, patient-reported outcomes, range of motion or strength measures between stemless and short-stem aTSA at 2 years postoperatively."

Radiographic comparison of eccentric stemmed vs. concentric stemless prosthetic humeral head positioning after anatomic total shoulder arthroplasty "Stemless and stemmed aTSA implants have similar rates of reproducing satisfactory postoperative humeral head center of rotation (COR) with both producing COR deviation most commonly in the superomedial direction. Deviation in humeral head height above the greater tuberosity (HHH) contributes to overstuffing in both stemmed and stemless implants, COR deviation contributes to overstuffing in stemmed implants, while radius of curvature (RoC) is not associated with overstuffing."

Stemmed VS stemless total shoulder arthroplasty: a systematic review and meta-analysis "stemmed and stemless TSA provided good clinical results, with similar benefits in terms of clinical outcomes and complications."

A stemless anatomic shoulder arthroplasty design provides increased cortical medial calcar bone loading in variable bone densities compared to a short stem implant "A cortical rim-supported stemless implant maintained proximally improved dynamic bone loading compared to a press-fit short stem implant. Biomechanical time-zero implant micromotion in lower bone densities was comparable between short stem and stemless implants at rehabilitation load levels (220 N, 520 N), but there was higher cyclic stability and reduced variability for stemmed implantation at peak loads (820 N)."

Comparable low revision rates of stemmed and stemless total anatomic shoulder arthroplasties after exclusion of metal-backed glenoid components: a collaboration between the Australian and Danish national shoulder arthroplasty registries "Based on data from 2 national shoulder arthroplasty registries, we found no significant difference in risk of revision between stemmed and stemless total shoulder arthroplasties after adjusting for the type of glenoid component. We advocate that metal-backed glenoid components should be used with caution and not on a routine basis." see also High revision rate of metal-backed glenoid component and impact on the overall revision rate of stemless total shoulder arthroplasty: a cohort study from the Danish Shoulder Arthroplasty Registry. and Complications and revisions in metal-backed anatomic total shoulder arthroplasty: a comparative study of revision rates between stemless and stemmed humeral components

Stemless anatomic and reverse shoulder arthroplasty in patients under 55 years of age with primary glenohumeral osteoarthritis: an analysis of the Australian Orthopedic Association National Joint Replacement Registry at 5 years "In the predominantly male patient population below the age of 55, stemless aTSA had a lower short-term revision risk than stemmed aTSA."

Comparing optimum prosthesis combinations of total stemmed, stemless and reverse shoulder arthroplasty revision rates for men and women with glenohumeral osteoarthritis "In a subanalysis of procedures in males since 2017 with additional adjustments,stemless (slTSA) shoulder arthroplasty with cemented polyethylene glenoids had a lower revision rate than stemmed (stTSA) shoulder arthroplasty with modified central peg polyethylene glenoids" The same authors came to a slightly different set of conclusions in A comparison of revision rates for stemmed and stemless primary anatomic shoulder arthroplasty with all-polyethylene glenoid components: analysis from the Australian Orthopaedic Association National Joint Replacement Registry "Revision rates of stTSA and slTSA did not significantly differ and were associated with humeral head size but not patient characteristics. Surgeon inexperience of anatomic shoulder arthroplasty and non-XLPE glenoids were risk factors for stTSA revision but not slTSA. Revision for instability/dislocation was more common for slTSA."

Medium-term results of stemless, short, and conventional stem humeral components in anatomic total shoulder arthroplasty: a New Zealand Joint Registry study "The medium-term survival of stemless implants for anatomic total shoulder arthroplasty appears comparable to short-stem and conventional stemmed implants."

Stemless components lead to improved radiographic restoration of humeral head anatomy compared with short-stemmed components in total shoulder arthroplasty "Stemless prostheses placed during TSA achieved improved restoration of humeral head COR and were less likely to have significant COR outliers compared with short-stem implants."

Short-term radiographic analysis of a stemless humeral component for anatomic total shoulder arthroplasty "This study demonstrates a low rate of stress shielding for a stemless design humeral implant at short-term follow-up without any revision surgery due to humeral component complications."

Preoperative metaphyseal cancellous bone density is associated with intraoperative conversion to stemmed total shoulder arthroplasty "Metaphyseal cancellous bone density can be calculated on preoperative CT scans and is associated with intraoperative conversion to a stemmed humeral component in anatomic shoulder arthroplasty. A threshold of 20 HU can be used to predict which patients are more likely to require stemmed components."

Is stemless total shoulder arthroplasty indicated in elderly patients? "Age >/=70 years does not appear to be a contraindication to stemless anatomic total shoulder arthroplasty. Postoperative improvements in outcome scores were similar between patients aged <70 yr and those aged >/=70 years. There was no difference between the groups regarding the patients who required intraoperative deviation from the preoperatively planned stemless prosthesis to a stemmed prosthesis."

Comment: As with all of orthopedics, experience is the great teacher for stemless arthroplasty. Be ready.