Stemless total shoulder - is there spin in the abstracts?

Recently I've posted on 

Spin in abstracts on the subacromial balloon

Spin in abstracts on the augmented glenoid

Spin in abstracts on superior capsular reconstruction

Now we have the opportunity to consider spin in abstracts on the stemless total shoulder arthroplasty 

The stated goal of Evaluation of Spin in the Abstracts of Systematic Reviews and Meta-Analyses of Stemless Total Shoulder Arthroplasty was to identify and detail incidence of spin in the abstracts of systematic reviews and meta-analyses of stemless component total shoulde arthroplasty (TSA). The secondary goal was to investigate general study characteristics and describe patterns in relation to spin.

The authors point out that surgeons tend to read only the abstracts of publications, thus assessing spin in abstracts is important.

The details of their analysis is similar to that presented in Spin in abstracts on the augmented glenoid.

Basically the types of spin are:

Authors hide or do not present any conflict of interest 

Selective reporting of or overemphasis on efficacy outcomes or analysis favoring the beneficial effect of the experimental intervention 

Selective reporting of or overemphasis on harm outcomes or analysis favoring the safety of the experimental intervention 

Failure to specify the direction of the effect when it favors the control intervention 

Failure to report a wide confidence interval of estimates 

The conclusion claims the beneficial effect of the experimental treatment despite a high risk of bias in primary studiesThe conclusion claims the beneficial effect of the experimental treatment despite reporting bias. 

The conclusion formulates recommendations for clinical practice not supported by the findings 

The conclusion claims safety based on non-statistically significant results with a wide confidence interval 

The conclusion focuses selectively on statistically significant efficacy outcome 

The conclusion claims equivalence or comparable effectiveness for non-statistically significant results with a wide confidence interval 

The conclusion extrapolates the review findings to a different intervention (e.g., claiming efficacy of one specific intervention although the review covered a class of several interventions) 

Conclusion extrapolates the review's findings from a surrogate marker or a specific outcome to the global improvement of the disease 

Conclusion extrapolates the review's findings to a different population or setting 

The authors analyzed 12 articles. At  least 1 form of spin was observed in 10/12 (83.3%) studies. The most common type of spin was

“The conclusion claims the beneficial effect of the experimental treatment despite a high risk of bias in primary studies”, which was found in 7/12 (58.3%) studies. 

The three other common types of spin identified were

"The conclusion claims safety based on non-statistically significant results with a wide confidence interval"

"Authors hide or do not present any conflict of interest" 

"The conclusion formulates recommendations for clinical practice not supported by the findings"

According to  AMSTAR 2, 11/12 (91.7%) of studies had confidence ratings of “low” or “critically low” due to one or more critical flaws.

The authors concluded that "spin is prevalent in abstracts of systematic reviews and meta-analyses covering stemless TSA. Reporting more favorable outcomes is the most common type and physicians should be aware of this when making clinical decisions based on research". Authors tended to neglect the evaluation of primary study bias in their methodology; instead the discussion focused mainly on advantages of the stemless design.

Risk of overestimating the clinical importance of the stemless component TSA due to spin is especially relevant when contextualized within current literature on the topic. Romeo et al and Wiater et al recently performed two large, multicenter, prospective, blinded randomized controlled trials evaluating short-term clinical and radiographic outcomes of stemless implants against their traditional stemmed counterparts. Both studies found a lack of significant difference between stemmed and stemless component clinical outcomes, complications, and reoperation rates within a 2-year follow-up period. Additionally, the authors were careful to describe stemless implant performance as “noninferior,” “safe,” “effective,” or “promising.”Their findings are in contrast to the beneficial effect spinning that was most pervasive across the systematic reviews analyzed in the current study and suggest a pattern of overly optimistic conclusion-drawing despite RCTs that do not yet paint such a positive picture of the stemless technology.

Conclusion:

This study does not provide new evidence of the case for or against the use of a stemless humeral component. It does suggest that authors should attempt to avoid spinning their abstractions by making sure that the conclusions regarding safety and clinically (not only statistically) significant benefit are supported by robust evidence and that conflicts of interest and other sources of bias are made explicit.

Spin is not always bad, here are male and female redtail hawks spinning in courtship.

Red tailed hawks courting

Union Bay Natural Area

March 2021

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link

Follow on twitter/X: https://x.com/RickMatsen
Follow on facebook: https://www.facebook.com/shoulder.arthritis
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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).

Stemless anatomic humeral arthroplasty – plain x-ray planning and surgical technique

Stemless humeral components have the advantage of enabling the placement of the humeral articular surface in the desired location independent of the position of a stem in the medullary canal.  

As a result, they have become my usual choice for anatomic total shoulder and for the ream and run arthroplasty.  

The technique I use is continuing to evolve with experience and from collaboration with my partners, our fellows, our residents, and my colleagues around the world. Below are some elements of my technique as of today. I hope to continue learning.

While this presentation reflects my current use of implants from a particular company, I have no financial or other conflicts of interest with this or any company.

Planning is done using PACS images of a preoperative plain X-ray of the proximal humerus taken with the arm in 30 degrees of external rotation in relation to the x-ray beam. A circle (white) is drawn to fit the proximal humeral anatomy. In this case the diameter of this circle is 46 mm (radius 23 mm), which is the approximate diameter of curvature of the humeral head component. The approximate thickness of the head component is calculated as .75 * the radius, which in this case is .75*23 or 17 mm. The humeral head cut (blue line) is drawn at a 45 degree angle with the axis of the humeral shaft and 17 mm from the edge of the circle (yellow line segment).

See alsoPre-operative planning for anatomic shoulder arthroplasty and ream and run hemiarthroplasty – what can be accomplished using plain x-rays?

Of course these dimensions are only preoperative estimates and may need to be modified according to intraoperative findings of mobility and stability after the surgical approach, osteophyte resection and soft tissue releases.

The shoulder is approached through the deltopectoral interval and with a subscapularis peel, preserving the long head of the biceps (unless it is unstable or frayed).

Excellent exposure is essential. The anterior and inferior osteophytes are vigorously resected. 

The "Hinge point" is the superior margin of the humeral articular surface, identified just inside the long head tendon of the biceps (which is preserved) and the supraspinatus. This can be exposed with a 'baby' Hohmann retractor.

The inferior capsular reflection is revealed after the osteophytes have been removed. The plane of the cut is shown as the yellow line connecting the hinge point and the inferior capsular reflection; it is oriented at an angle of 135 degrees with the humeral shaft.  .

The surgeon must stand tall so that she or he has the "Birds Eye View" of the posterior rotator cuff to assure that the saw passes just anterior to the infraspinatus insertion

Here are examples of what to avoid:

(1)  underresected humeral necks resulting in overstuffing of the joint (see how to overstuff an anatomic arthroplasty). 

and 

(2) poorly oriented head cuts

Here is the completed cut.

The trial head size is estimated to match the anteroposterior dimensions of the neck cut. The trial head is positioned so that a few millimeters of the neck is exposed superiorly.

With the stemless, as with all humeral components, it is important that upper lateral aspect of the head does not extend superiorly to the berm 

After the glenoid preparation for either a prosthetic component or a ream and run, the trial head is fit to and positioned on the neck cut and used as a guide for insertion of the guide pin

This pin is used to guide the humeral preparation

and for insertion of the trial blaze

The trial head is secured to the trial blaze

so that the mobility and the stability of the head on the glenoid can be examined. With the trial in place I check for the following

(1) the mobilized subscapularis should reach the lesser tuberosity with the arm in at least 40 degrees of external rotation

(2) the range of motion should include 150 degrees of flexion and 60 degrees of internal rotation with the arm in 90 degrees of abduction

(3) the humeral head should be translatable posteriorly by 50 percent of the width of the glenoid and return to the centered position when the translating force is removed

(4) when the arm is held in 90 degrees of flexion, the humeral head should translate no more than 50 percent of the width of the glenoid

One of the biggest challenges is make sure that the reconstruction does not tighten the shoulder by over lateralizing the proximal humerus in relation to the scapula; this is important for both the anatomic total shoulder

and for the ream and run. 

If the shoulder is tight preoperatively, it is important to perform a complete capsular release around the humerus and glenoid 

as well as a 360 degree release of the subscapularis.

 

Avoiding overtightening also requires the surgeon to be mindful of the effect of humeral head geometry on the volume of the head component, recognizing that the choices of head diameter of curvature and head thickness are limited by the inventory in each company's system. 

The perimeter of the trial head is examined for exposed bone, which is removed with a pinecone bur

I’m always prepared to convert to a short humeral stem for one of several indications:

(1) The bone of the proximal humerus is too soft to securely fix the nucleus. Rather than relying on the "thumb test" or on a preoperative CT to estimate the local bone density, it seems more practical to insert the blaze trial

to see if it fits securely in the bone.

If not, I convert to a short stem positioned to place the head in the previously defined anatomic position. 

(2) The fins of the nucleus are too long for the humerus.  

This is most likely to be an issue in small individuals with soft bone (which leads to consideration of a larger sized nucleus with longer fins). The risk of “too long fins) can be estimated by holding the trial blaze up to the humeral neck (the “eye-ball test”)

If this is a concern, I convert to a short stem positioned to place the head in the previously defined anatomic position.

(3) Intraoperative testing reveals that an anatomically positioned humeral head cannot be stabilized on the glenoid without overstuffing the joint. In this situation I convert to a short stem to support the use of an anteriorly eccentric humeral component 

An important element of avoiding stiffness is having a repair of the subscapularis peel that is sufficiently robust that gentle mobilization of the shoulder can be instituted soon after surgery with minimal risk of subscapularis failure. I use 6 sutures of Fiberwire passed through solid bone at the lesser tuberosity.

An additional one or two Fiberwires are placed in the rotator interval capsule to reinforce the subscapularis repair. As shown below, these sutures are passed over the long head tendon of the biceps, which is preserved in almost all cases.

At the conclusion of the case I verify that the shoulder has stability and a full range of assisted flexion, documented with a “parting shot” photograph that is included in the operative note. 

This is what I’m doing at the start of 2025. I would welcome comments and suggestions on alternative approaches.

Once again thanks to our residents Jon Yamaguchi  and Kevin Khoo for their help with the figures shown here,

Keeping it simple

Willow Flycatcher

Union Bay Natural Area, Seattle

June 2025

 You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link

Follow on twitter/X: https://x.com/RickMatsen
Follow on facebook: https://www.facebook.com/shoulder.arthritis
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).

Stemless or stemmed total shoulder arthroplasty?

 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. See Seven ways to Overstuff and Anatomic Arthroplasty.

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.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link

Follow on twitter/X: https://x.com/RickMatsen

Follow on facebook: https://www.facebook.com/shoulder.arthritis

Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).