Stemless humeral components for anatomic arthroplasty?

Short stemmed humeral components (above left) allow for loading of the humeral medullary canal. They can be used with eccentric humeral heads. Short stems are more difficult to position centrally in the canal than impaction grafted standard length stems.

Stemless humeral components (above right) allow the positioning of the humeral joint surface independent of an intramedullary stem. They load the humeral epiphysis. They do not allow for the use of eccentric (offset) humeral heads.

Let's review some articles that have tried to compare the results of stemless and short stemmed humeral components in anatomic total shoulder arthroplasty. 

2013 Stemless shoulder prosthesis versus conventional anatomic shoulder prosthesis in patients with osteoarthritis found no difference in outcome or complication rate. Blood loss and operative time were less with the stemless implant.

2014 Radiographic assessment of prosthetic humeral head size after anatomic shoulder arthroplasty found more frequent deviation from the anatomic center of rotation for stemless implants than for stemmed implants.

2019 Radiographic restoration of native anatomy: a comparison between stemmed and stemless shoulder arthroplasty found that radiographic restoration of anatomy was similar for stemmed and stemless shoulder arthroplasty implants.

2020 Prospective, Blinded, Randomized Controlled Trial of Stemless Versus Stemmed Humeral Components in Anatomic Total Shoulder Arthroplasty: Results at Short-Term Follow-up reported identical two-year outcomes scores, complication rates, and loosening rates for stemmed and stemless anatomic total shoulders

2021 Radiographic evaluation of humeral head reconstruction with stemmed and stemless spherical implants compared with stemless elliptical head implants found that spherical stemless humeral heads were superior to spherical stemmed components in recreating anatomic head height and minimizing overhang, but less effective in recreating anatomic center of rotation.

2022 A Comparison of Operative Time and Intraoperative Blood Volume Loss Between Stemless and Short-stem Anatomic Total Shoulder Arthroplasty: A Single Institution's Experience reported that stemless aTSA was associated with a decreased surgical time and less intraoperative blood loss when compared with short stemmed aTSA.  Patients receiving stemless implants had a shorter hospital lengths of stay and lower discharge pain scores.

2022 Surgical time and outcomes of stemmed versus stemless total shoulder arthroplasty The average operative time was 24 minutes less in the stemless cohort compared with the stemmed cohort. There was no difference found in visual analog scale, American Shoulder and Elbow Surgeons, and Single Assessment Numerical Evaluation scores between the cohorts at the 2-year follow-up.

2022 Short-term survival and patient-reported outcome of total stemless shoulder arthroplasty for osteoarthritis are similar to that of stemmed total shoulder arthroplasty: a study from the Danish Shoulder Arthroplasty Registry reported that the 5-year cumulative implant survival rates were 0.96 for stemless TSA and 0.97 for stemmed TSA. While the stemless TSA had a statistically significantly better patient-reported outcomes compared with stemmed TSA, the difference was not deemed to be clinically relevant. 

2022 Outcomes Between Stemmed and Stemless Total Shoulder Arthroplasty: A Systematic Review and Meta-analysis of Randomized Controlled Trials found no differences in  functional or clinical outcomes between stemmed and stemless TSAs. No differences were observed between stemmed and stemless designs in the rate of humeral fracture or risk of revision.

2023 Stemless components lead to improved radiographic restoration of humeral head anatomy compared with short-stemmed components in total shoulder arthroplasty found that mean center of rotation (COR) shift for short stems was 2.7 mm (±1.4 mm) compared with 2.1 mm (±0.9 mm) for stemless implants. The clinical significance of this 0.6 mm difference is unclear. Stemless prostheses were less likely to have significant COR outliers compared with short-stem implants.

2023 Medium-term results of stemless, short, and conventional stem humeral components in anatomic total shoulder arthroplasty: a New Zealand Joint Registry study found no significant difference in revision rate per 100 component-years between stemless (.99) and short-stemmed implants (.54). 

2023 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 reported that revision rates for stemmed TSA and stemless TSA did not differ significantly. There was an increased rate of revision for humeral head sizes <44 mm. Surgeon inexperience with anatomic shoulder arthroplasty and non-cross linked polyethylene glenoids were risk factors for stemmed TSA revision. Revision for instability/dislocation was more common for stemless TSA (below right) while loosening was more common for stemmed components (below left).

2024 Radiographic comparison of eccentric stemmed vs. concentric stemless prosthetic humeral head positioning after anatomic total shoulder arthroplasty found that stemless and stemmed aTSA implants have similar rates of satisfactory postoperative humeral head center of rotation.  COR deviation was most commonly in the superomedial direction for both humeral component designs. 

2024 Stemless anatomic total shoulder arthroplasty is associated with less early postoperative pain found that stemless aTSA provided earlier improvement in postoperative shoulder pain compared to matched patients undergoing short-stemmed aTSA. The majority of these differences were no longer evident at 26 weeks postoperatively. 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.

Comment:

These studies do not show a difference in patient outcomes between anatomic total shoulders performed with stemless or short stemmed humeral components. They do indicate that - with either system - accurate positioning of the prosthetic humeral head is important. Finally, they do suggest that total shoulders performed with a stemless component take less time and incur less blood loss.

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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link).
The total shoulder arthroplasty (see this link).
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link).
Shoulder rehabilitation exercises (see this link).