Avoiding baseplate screw failure in reverse total shoulder arthroplasty - innovation without increased cost or complexity

In followup to our post Reverse baseplate failure - fracture of the central screw, the senior author of Avoiding Glenoid Baseplate Fixation Failure by Altering Surgical Technique for Varying Bone Densities offered that "one technical issue leading to incomplete seating is very dense subchondral bone which can provide false sense of the implant being fully seated; another pitiful is if there is some cartilage left on the glenoid which also can lead to incomplete seating booth of these have happened with screw breakage at the interface of the baseplate screw junction"

His conclusions can be summarized as follows:

(1) baseplate failure is an import complication of reverse total shoulder arthroplasty

(2) time zero (immediate post op) stability of the baseplate is important because (a) the patient will load the baseplate before any bone ingrowth has had time to occur and (b) micro motion of the baseplate will inhibit bone ingrowth so that the screws may be all that is holding the baseplate to the glenoid bone leading to the risk of fatigue fracture

(3) failure to remove cartilage and interposed tissue between baseplate and bone may prevent adequate seating of the baseplate

(4) as is the case with all screw fixation in bone, bone quality has a strong effect on the quality of fixation: (a) low bone density may result in lack of a solid "bite" (screw stripping); (b) high bone density may result in incomplete seating

(5) from plain radiographs, the surgeon can preoperatively get an idea of the glenoid bone density: poor (below left), sclerotic (below right).

(6) for bone suspected of having poor bone quality, the author uses some straightforward innovations that do not add time, technology or expense: 

    (a) for soft bone the glenoid is reamed over a 2.5 mm drill (without using a tap) followed by insertion of the baseplate in the untapped bone 

    (b) for denser than average bone,  a 3.0-mm drill is used for the pilot hole, and then the tap is passed (inserted and removed) a total of 3 times, followed by insertion of the baseplate in the tapped bone 

    (c) the standard technique is used for average density bone: a 2.5-mm drill is inserted in the central hole to a depth of 30 mm, followed by use of the 6.5-mm tap, reaming of the glenoid, and finally, insertion of the monoblock baseplate

In in vitro testing using a low-density block model, the standard technique gave a compressive force of 112 N compared with 300 N for the soft bone technique.

In the high-density bone model, the standard technique resulted in failure to seat the baseplate, or screw breakage. Performing the dense bone technique, the baseplate was seated without failure, with an average compressive force of 450 N. 

Comment: Time zero (initial) fixation is important for minimizing the risk of baseplate failure. This requires adequate bone preparation for maximal baseplate-bone contact, full seating of the baseplate and placement of the peripheral screws in good quality bone.

The inspection of preoperative plain radiographs and the use of the techniques suggested here can reduce the risk of inadequate compression on one hand and incomplete seating on the other. 

It is noted that with this implant system, the only screw providing substantial compression is the central one - the others are locking screws. 

Finally, in cases where the central screw is stripped, we have found that "match stick" strips of cortical bone can be progressively added to the central hole until good compression is achieved.

Comments welcome at shoulderarthritis@uw.edu

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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). 

  

Innovation, balloons and irreparable cuff tears

I hope you enjoy the Hidden Brain as much as I do. 

A recent post Do less. points out that the human drive to invent new things has led to pathbreaking achievements in medicine, science and society. But our desire for innovation can keep us from seeing one of the most powerful paths to progress: subtraction. Sometimes the best way forward involves removing, streamlining and simplifying things.

One of the examples given is that while training wheels on a kid's bike seem like a good innovation, it enabled the child to ride without learning to balance.

It turns out that a better way to teach a kid to ride is to subtract the pedals and training wheels and - voila - the balance bike.

I'm also a big fan of the ASES podcast. A recent program,  Balloon vs. Tuberoplasty, reviewed options for managing irreparable rotator cuff tears, including superior capsular reconstruction, subacromial balloons, partial repairs, tendon transfers, and "biologic" tuberoplasty. The panel concluded that while there were "non-inferiority" studies and case reports, no surgical procedure was the clear favorite. As an example, a recent case series, Arthroscopic Subacromial Balloon Spacer for Massive Rotator Cuff Tears Demonstrates Improved Shoulder Functionality and High Revision-Free Survival Rates at Minimum 5-Year Follow-up, combined debridement with the placement of a subacromial balloon in 61 patients. 10 were lost to follow-up over 3 years. Of the remaining 51, 9 were lost at the latest follow-up.  17% required revisions within two years. Constant-Murley total scores increased significantly (27 to 69). 10% were highly satisfied, 48% were satisfied, and 43% were dissatisfied.

The podcast concluded with Justin Griffin saying, "There may be a future where we figure out a way to retrain the deltoid in the setting of a massive cuff tear that does not require any procedures." - an example of innovation by subtraction.

Many shoulders with chronic irreparable cuff tears (including my own) are comfortable and functional.  For patients with chronic irreparable cuff tears and problematic weakness, there is the opportunity to use a simple exercise to retrain the deltoid, which is the primary source of shoulder power no matter what other treatments are considered.

Patients with irreparable cuff tears can have painful subacromial crepitus, which can be identified by placing the examiner's finger just anterior to the acromion while the shoulder is moved in rotation and elevation. As mentioned in the ASES podcast, many surgical procedures have been advocated for such a patient, yet there are very few studies that compare these methods with each other. 

The authors of Comparison of Multiple Surgical Treatments for Massive Irreparable Rotator Cuff Tears in Patients Younger Than 70 Years of Age network meta-analysis to analyze comparative studies of surgical treatment options for massive irreparable cuff tears - without glenohumeral arthritis or pseudoparalysis -  in patients <70 years of age. The treatments included debridement; arthroscopic bridging graft; arthroscopic partial repair; superior capsular reconstruction; long head of biceps augmented superior capsular reconstruction; InSpace balloon placement; tendon transfer; and reverse shoulder arthroplasty.

A total of 23 studies met the inclusion criteria, with 1178 patients included in the analysis. The mean weighted age was 62.8 years; 48.2% were men, mean follow-up was 28.9 months. There were no significant differences between groups in regard to sex or age. 

The treatments were ranked using the the P-score - an estimate of the likelihood that the investigated treatment is the ideal method for an optimal result for each of the different outcome measures, where 0 is least effective and 1 is most effective.

Unfortunately most studies did not evaluate treatment with simple debridement in comparison to more complex procedures. However for studies that did, debridement had the highest P-score, as shown below.



Forrest plot for Constant Score:

Forrest plot for range of active forward flexion:

This network meta-analysis found that simple debridement was the most effective procedure in significantly improving Constant score and active flexion for individuals with massive irreparable cuff tears when it was compared to other more complex surgical modalities. 

Comment: Debridement is a component of most procedures performed for irreparable cuff tears. Debridement alone subtracts away the other possible surgical elements (balloons, grafts, partial repair). It has the important advantages of not requiring any post-surgical down time and of not burning bridges for other procedures should it not yield the desired result. Furthermore it is the least costly in comparison to grafts, balloons, and partial repairs and avoids the possible complications of these procedures. 

We refer to our approach to debridement as the "smooth and move procedure" emphasizing the goals of smoothing the articulation between the coracoacromial arch and the proximal humerus and initiating passive and active motion following the procedure. We have found this procedure to be effective not only as a primary procedure for patients with irreparable cuff tears, but also as a revision procedure for patients with failed prior attempts at surgical reconstruction.

Elements of this technique include (1) preserving the integrity of the deltoid and coracoacromial arch, (2) preserving the long head of the biceps unless it is frayed or dislocated, (3) removing hypertrophic bursal tissue, (4) trimming the rough edges of the reaming cuff, (5) resecting the prominent portions of the greater tuberosity, (6) manipulating the shoulder to eliminate any capsular tightness, and (7) starting motion exercises immediately after surgery.

The surgical technique and the outcomes of two patients having the smooth and move after failed cuff reconstruction attempts is shown in this link.

Two publications present the outcomes for this procedure:

Significant improvement in patient self-assessed comfort and function at six weeks after the smooth and move procedure for shoulders with irreparable rotator cuff tears and retained active elevation

Treatment of irreparable cuff tears with smoothing of the humeroscapular motion interface without acromioplasty

Comment to shoulderarthritis@uw.edu

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). 

Rotator cuff repair - 15 year clinical outcomes - can they be improved upon?

Long-term followup of shoulder procedures is of great interest to patients and surgeons. Rotator cuff repair (RCR) is perhaps the commonest of shoulder surgeries, therefore extended followup is also of great interest to the payers of health care. Yet getting reliable and relevant data is difficult because of patients lost to followup and evolution of surgical techniques.

The authors of  Minimum 15-year follow-up for clinical outcomes of arthroscopic rotator cuff repair point out that while studies have shown considerable symptomatic relief in the short term following surgery, a relatively high rate of recurrent defects has led surgeons to question the long-term durability of this operation. 

193 patients had all-arthroscopic rotator cuff repair by one of 12 surgeons between 2003 and 2005 and thus were potentially eligible for 15 year followup. Rotator cuff integrity was classified according to the method described by Harryman et al (Repairs of the rotator cuff. Correlation of functional results with integrity of the cuff). In this classification scheme, type 0 indicates intact; type 1A, partial tear of the supraspinatus; type 1B, full-thickness tear of the supraspinatus; type 2, full-thickness tear involving the supraspinatus and infraspinatus; and type 3, full thickness tear involving the supraspinatus, infraspinatus, and subscapularis. 

They collected patient-reported outcomes preoperatively and at 1, 2, 5, and 15 years postoperatively.  60 patients (31% of the initial cohort) had a mean follow-up period of 16.5 years. For these patients, the mean ASES score improved from 60 preoperatively to 93 at 15 years. 

There were no factors significantly associated with the final ASES score. Specifically neither the tear size or the integrity of the repair at 5 years correlated with the final ASES score.

Comment: While a 31% fifteen year followup rate is impressive, the lack of data on the missing 69% leaves us without a full understanding of the long term effectiveness of RCR. The lack of correlation of the available outcomes with the integrity of the repair leaves us without information regarding the importance of a durable repair. 

Substantial resources are being poured into innovations for improving the healing rates and clinical outcomes of cuff repair, such as different repair methods (double row, transosseous equivalent, etc), grafts, stem cells, platelet rich plasma, and growth factors. This study shows that accessing the longterm value of these efforts to the patient will be difficult.  

Furthermore, the ASES score for the patients in this study with 15+ years of followup averaged 93. According to Establishing minimal clinically important difference for the UCLA and ASES scores after rotator cuff repair The mean MCID value for the ASES score was 15.2 points. Thus, since the maximum ASES score is 100, it is not mathematically possible for any innovation to make a clinically significant improvement in the outcome of rotator cuff repair.

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).

High complication and revision rates for an "innovation" in upper extremity arthroplasty - does the FDA protect us?

Total elbow arthroplasty is used to manage elbow arthritis and fractures. In contrast to the normal elbow joint - where stability is provided by collateral ligaments and compression of the humeral trochlea into the concavity of the proximal ulna - total elbow designs commonly provide stability using a hinge connecting stemmed humeral and ulnar components, a configuration that is often needed because the normal ligamentous stability has been compromised by arthritis or fracture. An example is the Coonrad/Morrey Total Elbow.

One of the issues with using a hinge for stability is that substantial torque is applied to the prosthesis challenging the cement fixation of the stems.  Achieving durably secure fixation is difficult, as a result component loosening is not uncommon.  Yet another issue is the susceptibility of the polyethylene bushings to wear with subsequent instability and the risk of osteolysis. Periprosthetic fractures can result from the combination of an unyielding hinge and weakened bone. Another is the problem of abutment of the coronoid process against the distal humeral implant as shown below. 

In Experience with the Coonrad-Morrey total elbow arthroplasty: 78 consecutive total elbow arthroplasties reviewed with an average 5 years of follow-up the authors reported that at an average of 5 years of follow-up (2 to 11 years), radiolucencies were observed in 17 cases around the humeral component and in 14 cases around the ulnar component. Bushing wear was observed in 14 cases. There were 27 complications, and 9 of them went to a revision procedure. The survival rate was 97.7% at 5 years and 91.0% at 10 years if one considers revision for aseptic loosening as an endpoint.

In an attempt to improve these outcomes, the Nexel Total Elbow (see this link) was introduced with an "innovative 3rd bearing in the humeral yoke for increased compressive contact area" and "a robust Co-Cr linkage system to enhance linkage durability"

The manufacturer reported a predicted revision rate per 100 observed component years (OCY) of 4.2 for this implant (see this link).

However, at the March, 2022 meeting of the American Academy of Orthopaedic surgeons, a paper by Jacob Triplet, Mark Morrey, Shawn O'Driscoll, Joaquin Sanchez-Sotelo, and Chad Songy entitled Unexpected High Early Failure Rate of the Nexel Total Elbow Arthroplasty reported a 50% reoperation rate. The abstract is reproduced here.

"INTRODUCTION: Aseptic loosening, polyethylene wear and other forms of mechanical failure have limited the use of total elbow arthroplasty (TEA) in physically demanding patients. Newer implant designs have been introduced to improve mechanical performance; however, there is limited information about their clinical outcomes. The purpose of this study was to report the results obtained after implantation of a newer TEA design, the Nexel (Zimmer-Biomet, Warsaw, IN) TEA. METHODS: Over a 3-year period, two surgeons implanted a total of 35 consecutive Nexel primary TEAs. Average patient age was 65 (range, 29-95) years. Indications for TEA included failed open reduction and internal fixation or posttraumatic arthritis (17 elbows), acute distal humerus fracture (9 elbows), and inflammatory arthritis (9 elbows). Elbows were evaluated for pain, motion, the Mayo Elbow Performance Score (MEPS), complications, and reoperations
RESULTS: Of the thirty-five elbows, 12 (34%) underwent revision surgery with removal of either part or all Nexel components, with an average time to revision surgery of 2.2 years. Eleven of the 12 revision surgeries were performed at our Institution. All these eleven elbows were found to have gross loosening of one or both components at the time of revision surgery (9 loose humeral and 6 loose ulnar components). Forty-five percent had evidence of metallic debris within the bushing. Six of the 12 elbows revised were also noted to present with a periprosthetic fracture (5 humeral and 2 ulnar periprosthetic fractures). Of the remaining elbows, 2 were lost to follow-up, 18 had at least 2-year clinical follow-up, and 14 had 2-year minimum radiographic follow up. For patients with surviving implants, the mean follow-up time was 1.7 years. Radiographic evaluation of existing components revealed humeral component loosening in two elbows and periprosthetic fractures in four elbows (2 medial epicondyle, 1 olecranon, 1 humeral shaft). Overall, 17/35 (50%) elbows underwent reoperation and 20/35 (60%) elbows sustained at least one postoperative complication.
DISCUSSION AND CONCLUSION:
Primary TEA with implantation of this particular implant was associated with an unacceptably high rate of early implant loosening, periprosthetic fracture and reoperation. We hypothesize that this early unexpected mechanical failure could be explained by both the utilization of a titanium on polyethylene bearing surface as well as a more posterior center of rotation causing premature anterior impingement with flexion, which in turn leads to failure of the bonding interface, secondary titanium particle shedding, polyethylene wear and osteolysis."

Interestingly, an article published a year earlier, Short-term outcomes of the Nexel total elbow arthroplasty reported a two-year complication rate of 56% and a 22% revision rate. Aseptic humeral loosening was the main indication for revision. 

Comment:  From these two studies the short term outcomes for the innovative Nexel implant appear inferior to the long term outcomes of the Coonrad-Morrey implant.  One might ask, "does the FDA protect patients from devices with higher failure rates?". In that light, it is illuminating to review the FDA clearance for this innovation (see this link).

510 (k) Summary of Safety and Effectiveness - Zimmer Nexel Total Elbow

Comparison to Predicate Device: The Zimmer Nexel Total Elbow is substantially equivalent to the predicate device in terms of form and function. The Zimmer Nexel Total Elbow and the predicate device share similar intended uses and indications for use.

Comparison to the Predicate: The proposed device (Zimmer Nexel Total Elbow) and the predicate device (Coonrad/Morrey Total Elbow) have the same intended use and similar indications for use. The proposed device humneral and ulnar components are very similar in terms of materials used and design/dimensions to the predicate device humneral and ulnar components. The primary differences between the proposed and predicate devices are that the proposed device bearing components-are made of Vitamin E highly cross-linked polyethylene (the predicate device bearing components are made of ultra-high molecular-weight polyethylene), and the proposed device has bearings that articulate on both the outer and inner diameters of the ulnar eye (the predicate device has bearings that articulate on the inner diameter of the ulnar eye). Additionally, the proposed device uses screws and a I-part axle pin to fix the bearings in place, while the predicate device uses a 2-part (snap-fit) axle pin.

Performance Data:Non-Clinical Performance Testing Conducted:

• -  Stem Fatigue Testing

• -  Wear Testing

• -  Durability Testing

• -  Modular Connection Fatigue testing

  Non-Clinical Performance Testing Conclusions:

  Non-clinical testing demonstrated that the New Zimmer Total Elbow meets performance requirements as defined by Design Control activities and is substantially equivalent to the predicate device in terms of safety and efficacy.

  *In this case, clinical data and conclusions were not needed to demonstrate substantial equivalence.

One might ask "if  the device is "substantially equivalent" to the Coonrad-Morrey, why does the failure rate appear to be substantially higher?"

For more information about what the FDA does and does not do to protect patients and surgeons, see this link. 

The  US Food and Drug Administration maintains the Manufacturer and User Facility Device Experience (MAUDE). The MAUDE database is a publicly funded and publicly available means by which surgeons can identify adverse events for the prostheses they use before such information becomes available through journal publication or recall notification. This database has been the source for a recent article Timely recognition of total elbow and radial head arthroplasty adverse events: an analysis of reports to the US Food and Drug Administration which found that among 179 total elbow adverse event reports, the most common modes of failure were implant dissociation (23%), loosening (22%), and infection (16%). Three implant recalls were implemented 2, 5, and 9 years after the first adverse event report in the MAUDE database. Thus the MAUDE database provides alerts on prostheses that may be subsequently recalled 

The MAUDE data on over 100 adverse events associated with the Nexel implant are shown in this link, examples are shown on the list below.

Clicking on each these reports opens a report such as the below - some revealing as yet unpublished modes of failure.

This whole story gives us a lot to think about - most importantly how we do we consider the safety, value, and effectiveness of "innovations" over and against our standard accepted approaches for our patients.

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).

Innovation in shoulder arthroplasty - how should we spend our time and money?

 Novel robotic technology for the rapid intraoperative manufacture of patient specific instrumentation allowing for improved glenoid component accuracy in shoulder arthroplasty – A cadaveric study

These nine authors funded by De Soutter Medical point out that many different approaches are used for glenoid component placement in total shoulder arthroplasty and that "many types of guidance technology have been described to date often suffering from high costs, complex theatre integration, time inefficiency, and problems with day-to-day usability." To address these issues they propose an innovation consisting of an "intraoperative robotics platform, capable of rapid,  real-time manufacture of low-cost patient-specific guides whilst overcoming many of the issues with existing approaches."

The platform consisted of a tableside robot, a 3D optical scanner, a three-axis sterile robotic drill and a two-axis receptacle into which the disposable consumables were inserted. The consumable comprised of a region of rapidly setting moldable material and a clip allowing it to be reversibly attached to the robot. 

The sterile disposable was used to create a mold of the joint surface. Once set, the mold was inserted into the robot and an optical scan of the surface was undertaken followed by automatic surface registration with the CT data and surgical plan. 

The results suggest "achieved accuracy levels may be equivalent to those seen in other existing guidance technologies".

Comment: This appears to be a highly expensive and labor intensive innovation that "may be equivalent" to existing technologies. In order to offset the incremental cost and labor, the proponents of this innovation will need to demonstrate a substantial increase in clinical outcomes realized by patients having shoulder arthroplasty using this method in comparison to established cost-effective approaches such as that shown in this link, a technique that does not routinely require CT scans, 3D planning, or robots.

Follow on twitter: https://twitter.com/shoulderarth

Follow on facebook: https://www.facebook.com/frederick.matsen

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

How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).

This is a non-commercial site, the purpose of which is education, consistent with "Fair Use" as defined in Title 17 of the U.S. Code.          

Note that author has no financial relationships with any orthopaedic companies.

Does the innovation of pyrocarbon humeral head prostheses add value for young patients with arthritis?

Mid-term outcomes of pyrocarbon humeral resurfacing hemiarthroplasty compared to metal humeral resurfacing and metal stemmed hemiarthroplasty for osteoarthritis in young patients: Analysis from the Australian Orthopaedic Association National Joint Replacement Registry

These authors point out that humeral resurfacing hemiarthropaslty and stemmed hemiarthroplasty using metallic heads avoid the complications of loosening or wear of the glenoid component seen in total shoulder arthroplasty. but that survivorship has been limited by glenoid erosion when the metal resurfaced head articulates with the native glenoid.

Pyrocarbon articular surfaces have shown to have reduction in wear rates in in vitro testing. Thus pyrocarbon has been proposed as an alternative bearing surface for shoulder arthroplasty.

This study aimed to compare the survivorship of shoulder hemi resurfacing utilizing pyrolytic carbon (n=163) to metal hemi resurfacing (n=163) and metal stemmed hemiarthroplasty (n=67) using data from the Australian Orthopaedic Association National Joint Replacement for patients aged <55 years undergoing  primary shoulder replacement for osteoarthritis. It is of interest that >40% of hemiarthroplasties in this series were performed using pyrocarbon.

The authors report the results as follows, "For the diagnosis of osteoarthritis, the cumulative percent revision (CPR) at 6 years was 8.9% (95% confidence interval CI, 3.9, 19.4) for pyrocarbon hemi resurfacing compared to 17.1% (95% CI 11.9, 24.2) for metal hemi resurfacing, and 17.5% (95% CI 10.1, 29.4) for metal hemi stemmed. 

Overall,  pyrocarbon hemi resurfacing had a lower CPR rate compared to other metal hemi resurfacing (HR=0.41 (95% CI 1.08, 5.52), p=0.032). 

There was no difference in CPR rate when pyrocarbon hemi resurfacing was compared to metal stemmed hemiarthroplasty (p=0.067).

In male patients, pyrocarbon hemi resurfacing had a lower CPR compared to metal stemmed hemiarthroplasty (HR=0.32 (95% CI 0.11, 0.93), p=0.037). 

There was no difference in the rate of revision for males when pyrocarbon hemi resurfacing was compared to metal hemi resurfacing (p=0.097). 

Insufficient data was available for a subanalysis in female patients."

It is noted that pyrocarbon implants have a type of complication not seen with metal implants: prosthesis breakage accounted for >50% of the revisions in the pyrocarbon group. 

 Comment: While registry data can provide an overview of revision rates with different implants, a major shortcoming is the lack of data on the patient, shoulder and surgeon characteristics of cases receiving each type of implant, for example:

(1) were the patients of comparable health and socioeconomic status, or was pyrocarbon used in "preferred patients"?

(2) were the glenoid types comparable, or was pyrocarbon used in shoulders with less severe pathoanatomy?

(3) were the surgeons comparable or was pyrocarbon used by more experienced surgeons? Since revision was the primary outcome variable, is there evidence that the pyrocarbon surgeons had the same threshold for revision as the metal surgeons?

(4) how did the preoperative and postoperative patient self-assessed shoulder comfort and function compare among the groups, specifically were the clinical outcomes/patient benefit clinically significantly better for pyrocarbon (using an intention to treat analysis)?

(5) since value is benefit/cost, how does the cost compare among the three different implants (see this link)?

As explained in a recent post, Considering new technologies for our practice - understanding bias, it is possible for selection bias, transfer bias, assessor bias, and failure to assess clinical significance to paint an exaggerated view of a new innovation. see below.

Follow on twitter: https://twitter.com/shoulderarth

Follow on facebook: https://www.facebook.com/frederick.matsen

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

How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).