Stemless humeral arthroplasty depends on fixation of the humeral component to the proximal humeral metaphysis. The article referenced below maps the typical bone density of this region from the article Spatial mapping of humeral head bone density
The TESS had a relatively short clinical lifespan - it was discontinued after several years due to concerns about loosening and suboptimal outcomes. The device struggled with achieving reliable fixation, particularly in patients with poor bone quality.
In spite of this initial failure, many shoulder arthroplasty surgeons are currently successfully using newer stemless humeral components because of their ability to position the articular surface where the surgeon desires, rather than having it positioned as dictated by a humeral stem.
For many patients the cancellous bone of the humeral metaphysis is sufficient for secure fixation of the implant. Thus, as long as the head cut is made properly and the bone is of good quality, things usually work out well.
The challenge is that in older patients or patients with diminished quality of the cancellous bone in the humeral metaphysis, the fixation may not be adequate.
Some surgeons advocate preoperative CT imaging to examine local bone density. However, because the quality of fixation depends not only on bone quality but also on the design of the fixation device - the nucleus - that links the humeral head component to the humeral bone it seem more practical to insert the trial nucleus to assess fixation quality; if it's insufficient the surgeon can switch to a stemmed component.
Below I've endeavored to present five stemless shoulder arthroplasty systems arranged in chronological order of U.S. FDA clearance, examining their design philosophy, and mechanical advantages for osteoporotic bone quality.
N.B. Please note that I have no conflict of interest with any of the companies selling these implants. Note also that I used Claude.ai to help in the analysis and preparation of this post. As such there may be errors and I'd welcome any evidence-based corrections/comments. Finally, this analysis does not present clinical outcome, radiographic followup data, or complexity of revision among these options - such a comparison would require a very large number of patients and careful control of bone density and surgical technique.
1. Simpliciti (Wright Medical/Stryker)
FDA CLEARANCE: March 10, 2015
Design Geometry
Three central fins (~10mm length) arranged in a star pattern with central contact through a nucleus. While the nucleus provides broad cancellous contact with minimal risk cortical perforation, the central fin placement relies on cancellous bone which is weaker in patients with diminished bone desitity.
[Churchill RS et al. J Bone Joint Surg Am. 2016;98(7):552-560 (prospective two-year multicenter FDA IDE study, n=149). Churchill RS. J Shoulder Elbow Surg. 2014;23(9):1409-1414 (stemless shoulder arthroplasty current status review). First stemless system cleared in the United States, with clinical use in France beginning in 2010.]
2. Comprehensive Nano (Zimmer Biomet)
FDA CLEARANCE: April 2019
Design Geometry
Single central peg (15-20mm length, 8-10mm diameter) with tapered profile plus modular metaphyseal shells. Load concentrated in cancellous bone without peripheral bone engagement.
[Razmjou H et al. J Shoulder Elbow Surg. 2012;21(10):1-9 (early TESS/stemless design study). IDE study began with first U.S. implant in October 2013 at University of Virginia. Built on clinical heritage of Biomet T.E.S.S. stemless shoulder available in Europe since 2004. Comprehensive Nano IDE clinical trial data on file, Zimmer Biomet.]
3. Eclipse (Arthrex)
FDA CLEARANCE: August 1, 2019 (510(k) K183194)
Fenestrated central screw (6.5mm diameter, 35mm length) penetrates into cancellous bone. A collar-bearing baseplate is compressed against cancellous bone and the cortical rim. The degree of compression depends on the purchase achieved by the screw in the central cancellous bone which can be weak.
Clinical Evidence
[Habermeyer P et al. J Shoulder Elbow Surg. 2015;24(9):1463-1472 (midterm results). Habermeyer P et al. JSES Open Access. 2019;3(4):234 (9-13 year results). Gallacher S et al. J Shoulder Elbow Surg. 2018;27(12):2191-2197 (independent 2-year study). Uschok S et al. J Shoulder Elbow Surg. 2017;26(2):225-232 (Eclipse vs Univers II RCT). Over 20,000 successful implantations in Europe and Canada prior to U.S. FDA clearance. Longest clinical track record of any stemless system (2005-present)].
4. CS EDGE (DJO/Enovis)
FDA CLEARANCE/LAUNCH: September 30, 2020
Design Geometry
Three peripheral serrated fins arranged in tripod configuration (~15mm length, 2-3mm thickness) plus a short central peg. Fins engage peripheral bone (greater tuberosity, calcar region). Insertion needs to avoid fin perforation of cortex.
Clinical Evidence
Product launch announcement September 30, 2020 (DJO/Enovis). No published peer-reviewed clinical studies available to date.
5. OsseoFit (Zimmer Biomet)
FDA CLEARANCE: December 13, 2024
Asymmetric 3-4 peripheral fins with variable lengths (12-18mm) scaled to engage the asymmetrical peripheral bone in humeal head. Posterior-inferior fin longest, medial fin engages calcar, superior fins engage greater tuberosity. Requires precise surgical technique for correct rotational alignment
Clinical Evidence
FDA clearance announcement December 13, 2024 (Zimmer Biomet). No published peer-reviewed clinical studies available to date.
Fundamental Principle: Humeral head bone architecture exhibits a shell-and-core structure with peripheral bone density significantly exceeding central metaphyseal bone quality, especially in elderly patients and those with osteoporosis. Peripheral fixation designs theoretically exploit the strongest available bone, while central fixation systems depend on the bone that may be compromised in typical arthroplasty candidates.
It's all about fixation
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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).