Hemiarthroplasty rather than total shoulder for glenohumeral arthritis: results with a pyrocarbon humeral head.

There is a surge of interest in the use of humeral hemiarthroplasty - rather than conventional total shoulder -  in the management of patients with glenohumeral arthritis. Many such procedures have been performed using a cobalt-chrome humeral head in the ream and run. Now there is growing use of Pyrocabon humeral heads with the idea that glenoid wear/humeral medialization could be lessened because of the special lubricating properties of their articular surface. 

Last month's post The Ream and Run - how much of an issue is glenoid wear? pyrocarbon vs. chrome cobalt? summarized some of the relevant data. 

This week a new study was published: Five-Year Radiographic and Clinical Outcomes of Pyrocarbon Hemiarthroplasty for Glenohumeral Arthritis and Osteonecrosis, which evaluated the progression of humeral head medialization in patients having pyrocarbon hemiarthroplasty. This was a methodologically strong study; it was a prospective FDA, IDE investigation. Standardized protocols were used from the start with predefined outcome measures. The inclusion rate was high: 45 of 54 potentially eligible patients. Rigorous imaging standards were imposed from the start and consistent across all time points. The radiographic analysis was blinded and used standardized software. The correlation analysis was formalized. Kaplan-Meier curves were carried out with 7 year survival rates. Radiographic measurements and patient reported outcomes were documented at three time points. 

Included patients had a mean age of 52 years and a mean follow-up of 73 months. In addition to the pyrocarbon humeral hemiarthroplasty, 60% had a glenoidplasty, 27% had glenoid drilling only, 9% had no glenoid treatment. 

Significant improvements were observed across all outcome measures. Patient satisfaction was 98%. The 7-year revision-free survival rate was 95.7%. Two patients were revised for infection. Posterior subluxation in decentered shoulders decreased from 27% preoperatively to 20% postoperatively. The mean medialization of the humeral head averaged 2.9  mm at the 2-year follow-up (1.5 mm/yr) and after that increased at a lower rate ( 0.3 mm/year) to an average of 4.0 mm at the time of the final follow-up of 6 years for an overall medialization of 0.66 mm/year. 

Interestingly, Pearson correlation analysis found no relationship between medialization and clinical outcomes. Patients with significant glenoid wear achieved the same results as those with minimal wear. Younger age was the only significant predictor of severe medialization (p=0.030), however this increased radiographic wear in younger patients did not correlate with worse clinical outcomes. In fact, none of the measured variables - including medialization, age, sex, glenoid morphology, and treatment type - correlated with clinical outcomes.

The wear in this pyrocarbon study can be compared to that in another 2025 study that used a chrome cobalt humeral head with reaming of the glenoid (the traditional ream and run): Characterizing glenoid wear after hemiarthroplasty with concentric glenoid reaming: a study of 113 arthroplasties at a mean of 6.7 years of follow-up. Both studies had similar age (59 yrs RnR and 52 yrs Pyro) and sex (92% RnR and 78% Pyro) profiles. 

The method of measuring medialization in the Pyro study

was similar to that used in Characterizing Glenoid Wear after Hemiarthroplasty with Concentric Glenoid Reaming: A Study of 113 Arthroplasties at a Mean of 6.7 Years

As seen in the figure below, the wear rates for the traditional ream and run do not appear inferior to those for Pyrocarbon. The traditional ream and run study demonstrated a plateau in wear beyond 6 years based on 11 time points. The trajectory of pyrocarbon wear is less certain in that it is based on 3 time points.

Both studies showed high satisfaction and improvement in clinical outcomes. The RnR study was retrospective with 113 of 408 patients included, 12 had open revision. The Pyro study was prospective with 45 of 54 patients included, 2 had open revision; the difference in revision rate was not statistically significant. Neither study found a relationship between glenoid wear and patient-reported outcomes. Formal correlation analysis (pyrocarbon) and group comparisons (ream-and-run) both showed that patients achieved excellent results (>97% satisfaction, significant functional improvement) regardless of wear amount. None of factors studied were associated with clinical outcome.

Clinical Implications: Humeral hemiarthroplasty - either traditional ream and run or pyrocarbon hemiarthroplasty - are important surgical considerations for young patients with glenohumeral arthritis, especially if they wish to avoid the risks and limitations associated with the polyethylene glenoid component used in total shoulder arthroplasty. Both procedures were associated with over 97% rate of satisfaction. While younger age was associated with increased wear, none of the factors considered in these studies - including glenoid wear - were associated with the clinical outcome.

While it seems that a randomized clinical trial may be useful in comparing these two procedures, there would be some challenges in such a study as pointed out in Is pyrocarbon better than a ream and run? - a randomized controlled trial

Different heads

Pileated woodpecker

White headed woodpecker

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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).

Glenoid erosion in humeral hemiarthroplasty - how to minimize the risk

 Glenoid erosion is a recognized cause of inferior clinical results in humeral hemiarthroplasty.

While there is much current interest in the use of a pyrocarbon joint surface to reduce glenoid erosion, as the x-ray above demonstrates, glenoid erosion can take place with pyrocarbon as well as with metal humeral heads.

Here we present some approaches to reducing the risk of glenoid erosion that apply no matter what type of joint surface is used.

The gleonoid.

In the great majority of arthritic shoulders, there is loss of the congruency between the humeral and glenoid articular surfaces. Thus, rather than having the load distributed evenly across the joint (below left), the load is concentrated on a reduced area at the back of the joint. The resulting pressure (load/area) causes progressive posterior bone loss and decentering.

If a hemiarthroplasty is performed without addressing this force maldistribution, the posterior bone erosion will continue.

On the other hand, if conservative glenoid reaming is used to create a single concavity, even load distribution can be achieved. 

Experience suggests that a 2 mm diametral mismatch between the humeral head and the reamed glenoid is optimal.

If glenoid erosion is to be minimized, the maximum amount of the best quality bone (arrows) needs to be preserved.

by conservative reaming

This can be accomplished by accepting, rather than correcting, glenoid retroversion.

The diagrams below show the preservation of quality bone with accepting the glenoid retroversion (left) in comparison to the greater amount of bone removed with correcting glenoid retroversion (right)

In reaming the glenoid, sharp reamers and irrigation can help minimize the risk of thermal injury to the glenoid bone (see Thermal effects of glenoid reaming during shoulder arthroplasty in vivo).

While some surgeons advocate drilling holes in the reamed glenoid surface

it is apparent that this can weaken the glenoid surface making it more prone to erosion. Perhaps this "docking" is more appropriate when making a pie.

Finally, when possible it is desirable to preserve the glenoid labrum recognizing its load bearing and stabilization functions.

Overstuffing: Soft tissues

As pointed out in How to Overstuff an Anatomic Arthroplasty and Overstuffing is not a radiographic diagnosis, overstuffing is a condition in which the size and position of the shoulder arthroplasty implants result in excess tightening of the soft tissues encapsulating the joint. Thus, a shoulder with a chronically tight capsule and rotator cuff may be overstuffed by normally sized implant.

As pointed out in Practical Evaluation and Management of the Shoulder, overstuffing can not only restrict the range of glenohumeral motion

but it can also increase the force necessary to move the joint,
   

which increases pressure on the glenoid joint surface when vigorous stretching is carried out.

Thus for that reason, soft tissue releases are important for reducing the pressure on the glenoid and the risk of glenoid erosion. 

180 degree releases if there is excessive posterior translation

360 releases if the shoulder is tight all around

The adequacy of the releases can be verified while the trial components are in place, verifying that the shoulder can be easily flexed to at least 150 degrees

and that the shoulder meets the 40, 50, 60 rules (40 degrees of external rotation with the subscapularis approximated, 50% posterior translation, and 60 degrees of internal rotation with the arm abducted).

Overstuffing: Implant size and positioning.

While much attention is being paid to pyrocarbon as an alternative bearing surface, glenoid erosion can be seen with humeral heads of any type of material.

Common implant related causes of overstuffing.

(1) Inadequate head cut, leaving a too long neck.

(2) Too large humeral component

(3) Head too medial

(4) Head too high

When the head is high, it acts like a cam (click here), excessively tightening the inferior capsule when the arm is elevated because the center of rotation is malpositioned. This tightening results in increased pressure on the glenoid surface when the arm is raised.

(5)  Head high and medial

From the above it is noted that humeral head malposition can occur with pyrocarbon and with metal heads; humeral head malposition can occur with stemless, short stem and standard length stems.

To avoid overstuffing related to the humeral component, careful attention needs to be paid to the neck cut, head size and component position.

Conclusion

The risk of glenoid erosion can be reduced by preserving and protecting the best bone in the glenoid, balancing the soft tissues to optimize glenoid laxity, along with careful selection and positioning of the humeral component.

Avoiding glenoid erosion appears to depend more on surgical technique than on technology.

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

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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). 

Osteoarthritis: Hemiarthroplasty vs Total Shoulder. A pitfall of propensity score matched analysis

Randomization enables unbiased estimation of treatment effects; randomization attempts to assure that treatment-groups are balanced with respect to the important covariates. Unfortunately for us shoulder surgeons, surgical treatments are rarely assigned randomly.

Propensity matching is an attempt to use observational data to compare two treatment groups by accounting for the covariates that are associated with the outcome. 

The possibility of bias arises because a difference in the outcome between treatment groups may be caused by factors that predict which treatment the patient receives rather than the effectiveness of each treatment. For example if an observational study matching patients for age and sex alone retrospectively compared the recurrence rates after Bankart repair and after the Latarjet procedure, it would be at risk for an incorrect conclusion because it did not match for the size of the glenoid defect which may have affected the choice of treatment.

With that background let's look at Shoulder Hemiarthroplasty Is Associated With Higher 30-Day Complication Rates Compared With Total Shoulder Arthroplasty for Glenohumeral Osteoarthritis: A Propensity Score Matched Analysis. So, everyone with OA should get a TSA rather than an HA, right? 

However, the title itself gives pause: why should a smaller operation (hemiarthroplasty) have a higher short term postoperative complication rate than a more involved procedure (total shoulder arthroplasty)? Sounds like a fundamental attribution error.

Let's take a deeper dive. The authors searched the American College of Surgeons National Surgical Quality Improvement Program database for records of patients who underwent either TSA or HA for glenohumeral osteoarthritis of the glenohumeral joint. 

Patients in each group underwent a 1:1 propensity match for age, sex, BMI, ASA classification, diabetes mellitus, hypertension requiring medication, congestive heart failure, chronic obstructive pulmonary disease, inpatient/outpatient status, smoking status, and bleeding disorders.  2188 received TSA and 2188 received HA. The question is, "among these supposedly similar patients, what determined whether they wound up getting HA or TSA? We'll get back to that question shortly.

The HA patients had a higher rate of any adverse event (7.18% vs 4.8%), death (0.69% vs 0.1%), sepsis (0.46% vs 0.1%), postoperative transfusion (4.62% vs 2.2%), postoperative intubation (0.5% vs 0.1%), and extended length of stay (23.77% vs 13.1%). 

Comment: While these differences are striking, it is apparent that putting in a plastic glenoid does not reduce the risk of death, sepsis, transfusion, intubation or extended length of stay.

As stated above, the possibility of bias arises because a difference in the outcome between treatment groups may be caused by factors that predict which treatment the patient receives rather than the effectiveness of each treatment. HA patients had a statistically significantly higher mortality probability (0.004±0.010 vs 0.002±0.003 and morbidity probability (0.027±0.015 vs 0.021±0.011) at baseline compared with the TSA cohort, even after propensity score matching.  Surgeons may prefer to perform HA for high-risk patients and those with more complex pathology. Less experienced surgeons may elect to perform HA because of its simplicity. Surgeons may be more likely to perform HA on patients that have worse social determinants of health (Economic Stability, Education Access and Quality, Health Care Access and Quality, Neighborhood and Built Environment, and Social and Community Context), which are known to be associated with inferior outcomes.

Thus, while the authors state 

"HA was found to increase the odds of developing these complications when baseline demographics were controlled",

 perhaps a more accurate statement would be 

"Patients for whom the surgeons chose HA were found have increased odds of developing these complications when the selected baseline demographics were controlled."

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: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
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Follow on facebook: https://www.facebook.com/frederick.matsen
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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).

Pyrocarbon shoulder hemiarthroplasty - what do we think we know?

Cobalt chrome is a widely used and well-established material for humeral head replacement, known for its strength, durability, and resistance to corrosion. Chrome cobalt implants have a long clinical history and have demonstrated good outcomes. The example below shows a two year followup of a ream and run procedure (see this link) performed with a chrome cobalt humeral head and a titanium alloy stem. The 35 year old patient has experienced full recovery of his shoulder comfort and function. Note the uniform soft tissue layer between the humeral head and the glenoid bone (blue arrows), the absence of glenoid wear, as well as the absence of osteolysis and stress shielding around the stem fixed with impaction autografting (red arrows).




However glenoid wear can occur after hemiarthroplasty. In an effort to reduce wear, interest has been expressed in a pyrocarbon articular surface as an alternative to chrome cobalt.

Pyrocarbon is a form of carbon that is manufactured through a high-temperature pyrolysis process in which the organic material is heated in the absence of oxygen. This material is known for its strength, smoothness, hardness, and resistance to wear and corrosion. Depending on the loading environment, pyrocarbon is reported to have a lower coefficient of friction (0.01 to 0.1) than chrome cobalt (0.1 to 0.4). The reduced friction may be due to:

(1) pyrocarbon's minimal surface roughness resulting from its highly ordered crystalline structure; chrome cobalt has a relatively rougher surface compared to pyrocarbon.

(2) Pyrocarbon exhibits better boundary lubrication properties in comparison to chrome cobalt. Boundary lubrication refers to the mechanism in which the surfaces are self-lubricated by a very thin film - ranging from a few molecular layers to a few micrometers - consisting of molecules adhering to the surface that minimize friction. Chrome cobalt does not possess the same inherent self-lubricating properties as pyrocarbon, but rather relies more on fluid-film lubrication rather than boundary lubrication.

The smoothness and boundary lubrication properties of pyrocarbon may provide advantages in reducing glenoid wear and the inflammation that can result from wear particles. (see In vitro comparison of wear characteristics of PyroCarbon and metal on bone: Shoulder hemiarthroplasty)

Below is a two year radiographic followup of a pyrocarbon head on a short stem as reported in Pyrolytic carbon humeral head in hemi-shoulder arthroplasty:preliminary results at 2-year follow-up

Here are some receond reports of the use of pyrocarbon humeral heads:

Pyrolytic carbon humeral head in hemi-shoulder arthroplasty: preliminary results at 2-year follow-up 2018. 

At the 2-year follow-up, 50 glenoids (86%) showed no progression of erosion compared with their preoperative status whereas erosion was noted in 8 glenoids (14%).

Fracture of pyrocarbon humeral head resurfacing implant: a case report 2020. 

"Our observation put into question the use of pyrocarbon as a humeral head resurfacing implant. The material seems to be too fragile to be used as a resurfacing implant and cannot achieve fixation of the implant to bone."


Promising results after hemi-shoulder arthroplasty using pyrolytic carbon heads in young and middle-aged patients 2021.
Of 16 patients having an average 2 year followup, the survival rate was high (94.1%). One periprosthetic fracture occurred as the only complication during follow-up. Radiographs showed glenoid erosion in one case and subacromial space reduction in two cases.

Pyrocarbon Arthroplasty Implants in the Upper Extremity: A Systematic Review of Outcomes and Pooled Analysis of Complications 2021. 

Shoulder arthroplasty with pyrocarbon complication rate 13%.

Short-term outcomes and survival of pyrocarbon hemiarthroplasty in the young arthritic shoulder 2022. 

At a mean followup of 33 months, the rate of survival of the HA-PYC prosthesis among 64 shoulders was 92%. Revision was performed in 5 patients: 1 conversion to TSA and 4 conversions to reverse shoulder arthroplasty. The severity of preoperative and postoperative glenoid wear had no influence on the functional results. Nonanatomic reconstruction of the proximal humerus (center of rotation of the prosthesis > 3 mm from the anatomic center) occurred in 29% (18 of 62 patients) and was associated with significantly lower functional and subjective results, more complications (subscapularis insufficiency and/or symptomatic glenoid erosion), and a higher risk of revision. The additional 1.5-mm thickness of the metal disc under the pyrocarbon head was found to be the main reason for overstuffing of the prosthetic head.

Mid-term outcomes of pyrolytic carbon humeral resurfacing hemiarthroplasty compared with metal humeral resurfacing and metal stemmed hemiarthroplasty for osteoarthritis in young patients: analysis from the Australian Orthopaedic Association National Joint Replacement Registry 2022.
The authors analyzed 393 primary shoulder procedures, of which 163 were pyrocarbon hemi-resurfacing (unstemmed) procedures,





163 were metal hemi-resurfacing procedures, and 67 were metal stemmed hemiarthroplasties. The cumulative percentage of revision at 6 years was 8.9% for pyrocarbon hemi-resurfacing, 17.1% for metal hemi-resurfacing, and 17.5% for metal stemmed hemiarthroplasty. Pain, prosthesis fracture, and infection were the key reasons for revision of the pyrocarbon resurfacing hemiarthroplasty.

Short to Early-Mid Term Clinical Outcomes and Survival of Pyrocarbon Shoulder Implants: A Systematic Review and Meta-Analysis 2023. 

Two year survivorship of 92%.

Short-term outcomes following 159 stemmed pyrolytic carbon shoulder hemiarthroplasties and how they compare with conventional hemiarthroplasties and total shoulder arthroplasties in patients younger than 60 years with osteoarthritis: results from the New Zealand National Joint Registry 2023. 

Among patients aged <60 years with shoulder osteoarthritis, 48 underwent pyrocarbon hemiarthroplasty compared with 150 who underwent conventional hemiarthroplasty. There was no significant difference in revision rates or clinical outcomes between the groups.

Survivorship of shoulder arthroplasty for young patients with osteoarthritis: An Analysis of the Australian Orthopaedic Association National Joint Replacement Registry 2023
For stemmed hemiarthroplasty with a metal head, the cumulative revision rates at 2 years and 5 years were 7.4% and 16.7%. Glenoid erosion was the most common cause for revision.
For stemmed hemiarthroplasty with a pyrocarbon head, the cumulative revision rates at 2 years and 5 years were 3.5% and 8.9%. Instability was the most common cause for revision.

Pyrocarbon hemiprostheses show little glenoid erosion and good clinical function at 5.5 years of follow up 2023.
31 shoulders underwent PyC hemiarthroplasty; 11 also had concentric glenoid reaming. The mean follow-up was 5.5 years. AP x-rays were analyzed: A line parallel to the superior and inferior glenoid rim was translated to the most medial point of the glenoid surface. A further parallel line was placed on the spinoglenoid notch and the distance between the two lines was measured.




Measurements were scaled using the known diameter of the implanted humeral head component. 
The mean medial glenoid erosion was 1.4 mm over 5.5 years. In the first year there was 0.8 mm of erosion, significantly more than the average erosion per year of 0.3 mm. Mean erosion per year of patients with glenoid reaming was 0.4 mm, without reaming 0.2 mm. Prosthesis survival rate was 100%. There was a weak correlation between erosion and pain improvement and no correlation between erosion and delta Constant score.

Pyrocarbon hemiarthroplasty of the shoulder: a systematic review and meta-analysis of clinical results 2023.
12 studies (536 patients with pyrocarbon hemiarthroplasties) were reviewed with a minimum 2-year follow-up. Radiographically, 22.8% of patients had evidence of glenoid erosion, 10.4% had changes in implant positioning, and 9.9% had tuberosity thinning. In addition, 1.5% of patients had radiographic subacromial space reduction. There was an 8.6% complication rate, with the most common cause being glenoid erosion. There was an overall 7.7% revision rate, with 63% of revisions undergoing conversion to reverse or total shoulder arthroplasty.

Comment: Pyrocabon humeral heads are more expensive than chrome cobalt heads due to the unique properties and specialized manufacturing processes. Chrome cobalt heads have a long and well-established track record with low revision rates. Comparing the clinical value of pyrocarbon to chrome-cobalt will require randomized trials that control for surgeon expertise, patient characteristics and shoulder characteristics as well as knowledge of the costs of the two systems. The reason randomization is essential lies in the fact that without it, 

(1) better surgeons, high volume surgeons, or surgeons with conflicts of interest might exert a selection bias on which patients received pyrocarbon

(2) healthier, better informed or socio-economically advantaged patients may be more likely to receive pyrocarbon.

These and other important variables are essentially impossible to control for without randomization.

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: https://twitter.com/shoulderarth
Follow on facebook: click on this link
Follow on facebook: https://www.facebook.com/frederick.matsen
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).