Showing posts with label implant design. Show all posts

Tuesday, June 14, 2022

Reverse total shoulder - does prosthesis design matter?

37 years after its introduction by Paul Grammont, much time and money has been spent in innovating different designs for reverse total shoulder arthroplasty.

Some of the many are shown here (figure with permission from Orthopaedic Network News).

These designs differ in substantial ways, some of which are listed below.

Glenoid

Offset

Eccentric

Hooded

Diameter of curvature

Inferior overhang

Inferior tilt

Version

Lateralization

Bone augmentation (BIO RSA)

Metal Augments

Screws

Number

Compression

Locking

Parallel vs diverging

Central post

Trabecular metal

Polyethylene

Type

Thickness

Eccentric

Standard/retentive

Humerus

Neck shaft angle

Inlay/onlay

Offset

Stemless, short stem, standard stem

Straight / curved stem

Ingrowth/ cement/impaction grafting/ pressfit

Retroversion

Lateralization

Distalization

However at this point, the clinical advantages of one design over the others have not been demonstrated.

The authors of a recent article Inlay versus Onlay Humeral Design for Reverse Shoulder Arthroplasty: A Systematic Review and Meta-Analysis sought to determine if there were differences in clinical outcomes and complication rates between these designs using a systematic review of 12 studies comparing clinical results of both humeral designs. A total of 1447 patients were included with a minimum follow-up of 12 months. When comparing inlay versus onlay groups, the American Shoulder and Elbow Surgeons score was slightly higher in the inlay group (mean difference 2.53 points), but this difference was not clinically significant. Postoperative motion was not clinically different.

Comment: This review with short minimum followup did not control for the many other factors that influence the clinical outcome of reverse total shoulder, such as age, sex, diagnosis, pathoanatomy, and implant position.

A recent publication (see this link) found that the best results with reverse total shoulder were in patients with osteoarthritis and an intact rotator cuff - a diagnosis that is well treated by the less expensive anatomic total shoulder arthroplasty.

Thus, better clinical research is required to determine the appropriate use of reverse total shoulder and the relative value of different prostheses. Meanwhile, new innovative designs continue to appear in the marketplace each year without clear clinical evidence of their advantages.

For now, an attractive strategy is to gain working familiarity and experience with one reverse total shoulder implant that has an established track record along with the recognized technical steps that lead to the best outcome for the patient.

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

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).

Sunday, November 21, 2021

Reverse total shoulder arthroplasty - does the design matter?

A lot of time and money has been spent on developing and marketing different designs of reverse total shoulder implant systems. A few of the more commonly sold systems are shown below (figures from Orthopaedic Network News). From these illustrations one can see wide variability in baseplate fixation, glenosphere design, polyethylene configuration, neck shaft angle, inlay/onlay, humeral stem design, and humeral component fixation.

Because of the common, widespread, and increasing use of reverse total shoulder, companies are competing to demonstrate the superiority of their product.

The question is, "are there data to support the use of a given system?". A recent article

What is the best design for reverse total shoulder arthroplasty in 2022? attempted to address this question.

This comprehensive article deserves a careful read by all shoulder arthroplasty surgeons. The authors' bottom line is "To this date, no implant design and no specific design modification have proven to be better than another in clinical in vivo studies."

With respect to the glenoid component, the authors suggest that all systems on the market provide equally

strong primary fixation. They indicate that the best glenoid system should have a solution for severe glenoid bone loss or for bony lateralization with a longer fixation system, making it possible to have a strong purchase of at least 10mm in native glenoid bone. In addition, some amount of glenoid lateralization (6–8mm) seems necessary to improve active axial rotation, to decrease scapular notching, and to improve impingement free range of motion.

With respect to the humeral cup, a decrease in neck-shaft angle to a more anatomic 135 degrees may provide better passive range of motion without any adverse effects in terms of stability. There have been concerns recently regarding excessive tension with the use of onlay systems and a trend to more medialized inlay designs.

With respect to humeral stems, these authors suggest that the optimal design should be a compromise between strong humeral fixation without excessively filling the humeral canal to prevent bone remodeling but sufficiently filling the canal to prevent misalignment

Again, no implant design and no specific design modification have proven to be better than another in clinical studies.

With respect to the outcomes of reverse total shoulder arthroplasty, it may be that "the surgeon is the method". It is the surgeon that applies her or his experience and skill to assess the patient and the shoulder preoperatively, carries out the procedure, and manages the recovery. These factors may be more important to the clinical outcome and longevity than the implant design.

We should be asking, "What is the best way to spend our time and money to improve the outcomes of reverse total shoulder arthroplasty for our patients?"

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)

Shoulder arthritis - x-ray appearance (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.

Sunday, July 17, 2016

Reverse total shoulder - the effect of implant design on external rotation range of motion

The Effect of Humeral Inclination on Range of Motion in Reverse Total Shoulder Arthroplasty: A Systematic Review.

These authors conducted a systematic review of studies evaluating reverse total shoulders (RTSA) that reported the type of prosthesis as well as active postoperative ROM at a minimum of 12 months after surgery. Preoperative range of motion, postoperative range of motion and the difference in range of motion was compared between RTSA humeral components with cup inclination 135° and 155°.

Sixty-five studies with 3302 patients (3434 shoulders; 1211 in the 135° group and 2223 in the 155° group) were included.

Patients in the 135° group had significantly greater improvement in external rotation (P < .001) and significantly more overall external rotation compared to the 155° group. No significant difference were found between the 135° and 155° groups in range of motion improvements in forward elevation or abduction.

Comment: As the authors point out, the 135° neck shaft angle humeral prosthesis is usually used with a laterally offset glenosphere

whereas the 155° humeral prosthesis is usually used with a medialized glenosphere

So the effects of the humeral neck shaft angle may not be separable from the effects of the glenosphere design.

While the authors do not suggest why the 135° neck shaft angle humeral prosthesis is associated with more rotation, it is possible that the steeper angle and the lateral glenosphere offset reduce the risk of humeral abutment against the glenoid in external rotation as suggested by this axillary view.

Our approach to reverse total shoulder arthroplasty is shown in this link. Our goal, whenever possible, is a cementless impaction grafted humeral stem with a 135 degree angle and a laterally offset glenopshere securely fixed with screws in the high quality bone at the base of the subscapularis fossa with minimal inferior placement to avoid excess tension on the acromion and the brachial plexus. This combination may allow for a greater range of external rotation.