Conversion of an anatomic to a reverse total shoulder, when is a 'platform' prosthesis of benefit? Reprise

Due to the great interest in this subject, we're repeating this post with some additional thoughts.

An anatomic arthroplasty can fail for many reasons, including malposition, instability, delayed cuff failure and pseudo paralysis. In these situations consideration can be given to conversion of the anatomic prosthesis to a reverse total shoulder as shown here. As demonstrated in that post out preferred method for managing a failed anatomic arthroplasty is to completely remove the existing implant, obtain cultures, and then implant the reverse prosthesis. This approach allows full access to the glenoid and optimal positioning of the humeral component of the reverse. Removal of the anatomic implant is almost always possible and is particularly straightforward if it was inserted using impaction grafting.

In certain cases, such as that shown here, a well fixed stem can be retained and the proximal end converted to a reverse total shoulder with insertion of a glenosphere. Here's another post regarding conversion with retention of the anatomic stem.

Recently, there has been the advent of 'platform' prostheses, in which a humeral stem is fixed in the humeral canal that can be attached to either an anatomic or a reverse proximal humeral prosthesis. For examples, see here, here, here, and here.

It is important to recognize that in a reverse, (1) the glenosphere is placed inferiorly on the glenoid face, (2) the proximal humeral part of the reverse is bigger than that of an anatomic humeral arthroplasty and (3) the soft tissue tensioning considerations of a reverse are different from those of an anatomic arthroplasty. Therefore, the proximal-distal positioning of the humeral component needs to be fine tuned to achieve the ideal reverse arthroplasty. While some systems provide various adaptors to adjust the height, inclination and version of the proximal humeral prosthesis, the flexibility in positioning is limited by the use of the 'platform' fixed in the humeral canal.

Fortunately, we now have a clearer understanding of the indications for a reverse total shoulder, so that the needs for convertible prostheses is diminishing. For example, it is becoming evident that proximal humeral fractures in elderly individuals are often best managed by a primary reverse total shoulder - the idea of 'trying' an anatomic arthroplasty that is convertible to a reverse later is not so appealing. Similarly, individuals with arthritis, cuff deficiency, and instability are also best managed by a primary reverse.

See related post here.

One of the aspects lacking in articles about platform and other types of new shoulder prostheses is the incremental cost of the implant. This information is necessary to determine the value (benefit/cost) of the device. The question becomes, for 100 anatomic arthroplasties, how many successful conversions to reverses would be necessary to justify the incremental cost of (1) the implant and (2) the learning curve?

In our practice, revision of an anatomic to a reverse prosthesis is required almost exclusively in cases where the index procedure is done elsewhere. Often there are problems with stem fixation or positioning that require stem removal, even if 'in theory' the platform stem is convertible to a reverse.

One of the advantages of fixation of a humeral stem with impaction grafting is that - should conversion to a reverse prosthesis be required - the stem can be easily removed and the reverse stem inserted at the desired height and version.

Finally, infection with Propionibacterium is now recognized as a not unusual complication of shoulder arthroplasty. A well fixed stem for a platform prosthesis makes prosthesis exchange complicated
===
Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book

Click here to see the new Rotator Cuff Book

To see the topics covered in this Blog, click here

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Conversion of anatomic arthroplasty to reverse total shoulder: what is the place for modular stems?

Conversion of Stemmed Hemi- or Total to Reverse Total Shoulder Arthroplasty: Advantages of a Modular Stem Design

These authors point out that revision of a well-fixed humeral stem has the potential risk of loss of humeral bone stock, nerve injury, periprosthetic fracture, and malunion or nonunion of a humeral osteotomy with later humeral component loosening.

They conducted a retrospective study of 48 hemiarthroplasties and eight total shoulder arthroplasties that were converted to a reverse total shoulder arthroplasty system. 19 of the stems were modular and 37 were non-modular. The incremental cost of a modular stem design over a standard implant are not stated.

The commonest reasons for conversion to a reverse shoulder arthroplasty was rotator cuff lesion with instability/loss of function (29), aseptic stem loosening (8), stem malposition with functional deficit (8), failure of glenoid component (6), and glenoid erosion (5). 

In 13 cases (all with modular stems) the surgeon elected to retain the humeral stem and in 43 (6 with modular stems and 37 without modular seems) the surgeon elected to change the stem because of stem loosening in 10 cases, stem malposition in 8, and difficulty in conversion of a non modular stem to a reverse in 25. In 12 cases a longitudinal humeral osteotomy was required for stem removal.

Blood loss, surgical time, the rate of complications (principally fractures) and revision rate were greater in the cases where the surgeon chose to perform a full stem exchange. 

Comment: It is of interest that most of the anatomic hemiarthroplasties and total shoulder arthroplasties in this series that were revised to reverse total shoulders were for diagnoses (proximal humeral fractures, post traumatic arthritis and cuff tear arthropathy) that today may well be treated with primary reverse total shoulders rather than an anatomic arthroplasty with a modular stem.

While the authors conclude that "..modularity of a shoulder arthroplasty system has proven and substantial advantages if conversion to reverse total shoulder arthroplasty becomes necessary and might be considered as prerequisite for stemmed shoulder arthroplasty systems", it is unclear for which patients they recommend the modular stem.  It would be important to know whether the number of cases of primary arthroplasty with modular stems that need revision and which can be successfully revised without stem removal offsets the incremental cost of the general use of modular stem designs.

See related posts here and here.

===
Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book

Click here to see the new Rotator Cuff Book

To see the topics covered in this Blog, click here

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Conversion of a failed hemiarthroplasty for fracture to a reverse total shoulder

An elderly patient had a hemiarthroplasty for fracture one year ago.  She presented to our clinic with pain and instability. On exam she had anterior superior escape and pseudoparalysis. She desired revision to a reverse total shoulder.

The long humeral stem was well fixed with a large cement mantle. Removal of this stem from her thin bone would require a humeral osteotomy as shown here which would have complicated the stabilization of the humeral component of a reverse humeral component.

Thus, our plan was to try to preserve the stem and convert it to a reverse. Antibiotics were held for cultures, although there was no obvious evidence of gross infection. The humeral head was removed and the modular collar was removed. The humeral stem was well fixed.

There was significant scar tissue present in the wound limiting access to the glenoid. The soft tissue around the proximal humerus was released circumferentially and released from the inferior glenoid to gain excursion of the humerus distally. This exposure was difficult because of the fixed prominence of the humeral prosthesis.

The native glenoid was covered in fibrous tissue, which was debrided and reamed to a stable base.

One the exposure was sufficient, the glenoid component was inserted followed by the proximal humeral component of the reverse. We were fortunate that the shoulder could be stably reduced.

The patient is placed on the yellow protocol until culture results are final. Exercises will be started after six weeks of sling immobilization.

Comment: As we pointed out two blog posts ago, this case points out that the need for difficult conversion can often be avoided by performing a primary reverse for major displaced fractures of the proximal humerus in older individuals if the tuberosities cannot be stably reconstructed - obviously the case here. A second point is that conversion without humeral component removal is desirable, but difficult and the success of the conversion depends on being fortunate enough to have soft tissue balance without flexibility in the placement of the humeral and glenoid components of the reverse.

Finally, revision surgery of this type requires the surgeon to become familiar with arthroplasty systems foreign to his/her practice. There were many nuances of this prosthesis that we had to learn 'on the fly'.

Prepared by Robert Lucas, M.D.

===
Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book

Click here to see the new Rotator Cuff Book

To see the topics covered in this Blog, click here

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

Failed ingrowth hemiarthroplasty - revision to reverse

A lady in her late 70s presented with a painful shoulder after a prior hemiarthroplasty performed elsewhere. She could not perform any of the twelve functions of the Simple Shoulder Test. Her shoulder was very stiff and painful on movement.

Her radiographs showed a superiorly placed bone ingrowth humeral component that was eroding into her upper glenoid and acromion.

At surgery the supraspinatus tendon was absent and the remainder of the cuff thin. After a challenging prosthesis removal, we revised her to a reverse total shoulder.

Today, 7 weeks after surgery she reported that her shoulder was very comfortable, that she could once more do her own hair and that she was headed out on a cruise.

===
Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book

Click here to see the new Rotator Cuff Book

To see the topics covered in this Blog, click here

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

See from which cities our patients come.

See the countries from which our readers come on this post.

Conversion of an anatomic hemiarthroplasty to a reverse total shoulder

Some arthroplasty systems provide for the conversion of an anatomic humeral component to a reverse total shoulder. This conversion is easy with in vitro models, but, as we found out this week, in vivo it is challenging. Here is the x-ray of a patient who had had a prosthesis for fracture performed elsewhere. After this procedure she had no active elevation and consulted with us about the possibility of a reverse total shoulder. We had the options of removing the cemented stem and performing our usual reverse total shoulder prosthesis or of trying to preserve the stem and do a conversion. We elected the latter after extensive consultation with the patient.

 Our preoperative templating shows the challenge: while putting the reverse humeral tray and cup on the humeral prosthesis seems easy, the templating view shows that it is necessary to move the humerus distally to allow for insertion of the glenoid component...

to achieve reduction.

 The surgery was very difficult because of the challenge of exposing the glenoid and the problems of getting the glenosphere for this system properly seated on the base plate (required meticulous resection of the bone around the base plate - especially inferiorly - and very fiddly positioning of the glenosphere and challenge of assuring that the glenosphere is fully seated). Reduction was challenging, but stable. There we three special issues we encountered. First, as shown below, it is important that there is no bone extending beyond the medial extent of the base plate, otherwise it will block full seating of the glenosphere. It is difficult to see all the way around the baseplate, yet attention to this detail is essential.

Secondly, the base plate is not circular. Thus the glenosphere must be rotated exactly right for seating. This is not an issue with systems with a circular base plate. 

Finally, the glenosphere is not held in place by a Morse taper, only by a single screw. The fatigue properties of this glenosphere fixation in vivo are not known.

Bottom line, it is important to know your reverse system. They are all different.

Here's our post op film.

Happily, all nerves worked at the end of the case. Stay tuned.

---

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty,  and rotator cuff surgery.

See from which cities our patients come.

See the countries from which our readers come on this post.