Panel discusses impact of the Grammont’s reverse shoulder design 30 years later
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It has been 30 years since Paul M. Grammont, MD, and Emmanuel Baulot, MD, first published in the English-speaking literature on Grammont’s reverse total shoulder design. Grammont did not invent the reverse, but his design, which was unveiled in 1985, had two unique features. His design featured a large metal hemisphere with a medialized center of rotation and a polyethylene cup inclined at 155°.
Grammont believed distalizing the humerus would lead to increased deltoid tension, medializing the center of rotation would recruit more deltoid fibers for abduction and changing the inclination of the humeral component would improve stability. While the details regarding how and why his design works are still debated to this day, the clinical success was far beyond anything achieved to that date with such a challenging patient population of arthritis with rotator cuff deficiency. Grammont published his results in the French-speaking literature in 1987, and his publication in 1993 in Orthopedics ushered in a revolution in shoulder arthroplasty.
In 2003, the FDA approved the Delta prosthesis (formerly DePuy, now DePuy Synthes). The range of pathologies that can be addressed has dramatically expanded and the number of patients treated with the improved quality of life afforded by shoulder arthroplasty has been exponential.
We reflect on the impact of the man, the design and the publication with shoulder surgeons who have seen these tectonic shifts occur.
Grant E. Garrigues, MD
Moderator
Grant E. Garrigues, MD: In Grammont’s landmark 1993 Orthopedics paper, Grammont stated that “prostheses that reconstruct only the joint surface are outdated.” He was describing the fact that most shoulders that need a replacement have concerns about soft tissue and bony stability that may compromise the results of an anatomic implant, but his comments published 30 years ago were prescient. In many parts of the world, reverse shoulder arthroplasty accounts for 60% to 95% of primary arthroplasty implant choice – even in patients with intact rotator cuff and sufficient bone for anatomic total shoulder arthroplasty. As we sit here in 2024, was Grammont right? Is the anatomic TSA “outdated” or are we, as shoulder surgeons, just getting lazy?
Mark A. Frankle, MD: Indications for RSA have indeed grown in 2023. One of the benefits of reverse articulation is that it allows treatment of a diverse and complex set of pathological problems. For example, osteoarthritis can have a variety of bony deformities associated with that diagnosis. There can be glenoid bone loss, which may be asymmetric or central bone loss. Additionally, there can be a varying degree of cystic disease and synovitis, which may impact the outcome of an anatomic total shoulder. However, with the addition of newer anatomic glenoid components, including augmented glenoid components, improved glenoid fixation and humeral components that can restore the anatomic shape of the humerus allow for addressing more cases of osteoarthritis with the aforementioned pathology. This now provides so many choices that shoulder surgeons can select which option works best in their practice.
William N. Levine, MD: Nothing in life is as simple as all or none. Reverse total shoulder replacement is non-anatomic, so it comes with several asterisks.
- Asterisk 1 – introduction of a novel problem that did not exist with anatomic TSA – acromial/scapula spine stress fractures;
- Asterisk 2 – scapular notching and the long-term impact;
- Asterisk 3 – decreased range of motion compared to anatomic TSA (especially in internal rotation); and
- Asterisk 4 – concerns about polyethylene wear/debris due increased stresses in younger patients.
Pascal Boileau, MD: Anatomic prostheses are still needed today for young and active patients. Hemiarthroplasty with PyroCarbon head is a promising novel option that I have used in France for 10 years with good results.
John W. Sperling, MD, MBA: I think there is still an important role for anatomic shoulder arthroplasty in 2024. There have been a number of key advancements including stemless implants with improved bone preservation, humeral heads that allow the surgeon to dial the humeral head the exact amount and direction relative to the humeral head cut to optimize soft tissue tension, as well as improved glenoid fixation with hybrid glenoid components.
Garrigues: Grammont noted key features of his reverse design. First, he described the often-recited deltoid lever arm and the importance of the medialized center of rotation to improving this rotational moment. However, we often forget he also described the “fixed center of rotation” and that “the deltoid action is ... centripetal and is both an action of autostability and of direct constraint.” In 2024, can we really say how important the medialized center of rotation (COR) is compared with the semi-constrained design and deltoid wrap for stability and motion? What is the ideal COR offset now?
Frankle: One of the clear benefits of the RSA geometry is that it is able to oppose the deforming force of the deltoid and, in doing so, provides increased stability as Grammont described with the centripetal action, which allows the rotator cuff muscles, capsule and ligament constraints to avoid having to neutralize the vertical sheer force of the deltoid. It is likely that the asymmetric wear patterns that we observe on the glenohumeral humeral joint are related to a muscular imbalance of the deltoid overpowering the rotator cuff muscles. It has been such a strong tool for us to treat patients with these types of deformities. Clearly, in situations where the rotator cuff is present, the geometry of the prosthetic should allow the replication of the humeral head’s anatomic position relative to the glenoid. This idealizes the tension of the rotator cuff and deltoid allowing these muscles to function optimally along the respective Blix curve. To accomplish this, a lateralized glenoid component and a humeral component with a 135° neck-shaft angle placed at the anatomic neck plane is required.
Levine: It is Newton’s Third Law of Action and Reaction. Remember that every reverse design predating Grammont looked like a total hip prosthesis put into the humerus. The center of rotation was so far lateralized and they all failed, so Grammont reacted by going all the way in the other direction – horizontalizing the humerus and medializing the center of rotation to the glenoid face. This was a necessary first step because he needed to demonstrate clinical success in the face of catastrophic failure, and he did. With time, however, the world recognized there is a compromise between the two extremes and that is the exciting place we now find ourselves.
Boileau: By using the Bony Increased Offset (BIO)-RSA since 2006, we have abandoned the medialized COR for a long time. However, we believe that fixed center of rotation and humeral distalization and deltoid tension are important parameters to allow the deltoid muscle to overcome the weak or absent cuff muscles. By contrast, we do not think that humeral lateralization is mandatory.
Sperling: Research has shown a number of problems associated with medialization including an increased risk of instability and scapular notching. Therefore, there has been a strong trend toward glenoid lateralization. Additionally, there has been increasing evidence of the benefits of achieving this lateralization through metal rather than bone grafting. Zuckerman and colleagues recently published the results of 520 shoulders comparing augmented baseplates to bone grafting. Augmented baseplates had superior outcomes in all measures (Simple Shoulder Test, ASES score, UCLA Score and SPADI). Moreover, augments had 50% less OR time, threefold less notching and most importantly, eight fold less adverse events requiring revision.
Garrigues: Grammont prophetically noted, “A sound upper insertion of the deltoid depends particularly on the preoperative soundness of the acromion, often too thin, or even fractured.” In many series, acromial stress fractures are the number-one complication and are certainly a challenging clinical scenario. Will we solve this problem as shoulder surgeons and, if so, how?
Frankle: The impact of a preoperative fracture of the acromion is a good example of the different pathologies that are present in cases primarily of rotator cuff arthropathy. In addition to bone loss on the glenoid, there also can be bone loss on the acromion. We recently reviewed our experience and found that almost 20% of patients with cuff tear arthropathy will have a preoperative acromial fracture. These patients subjectively do worse compared to patients without these preoperative fractures, but still are improved compared to their preoperative status. The occurrence of postoperative fractures continues to be a challenge and, once again, is primarily seen in patients with rotator cuff deficiency. A better understanding of the natural history of the cuff-deficient shoulder may allow us to intervene prior to the advancement of acromial wear.
Levine: I believe this to be one of our biggest challenges in the next decade. If we use scapular notching as a case study, there is definitely hope. Think about this. When the reverse was released to North America in 2004, we knew next to nothing about the technology, and we had not heard even a whisper of scapular notching being an issue. Once our French colleagues reported on the long-term issues of scapular notching, techniques and designs started to evolve to bring the humerus more lateral – ie, further away from the inferomedial glenoid/scapular neck – and notching has gone the way of the velociraptor (almost). Likewise, the collective brain trust of shoulder surgeons and engineers will work toward identifying the root cause, treatment and prevention of this devastating complication.
Boileau: In our experience, acromial stress fractures occur in case of over-tension of the deltoid and/or over-lateralization of the humerus with anterosuperior impingement. Big data with artificial intelligence will bring some answers to avoid this complication.
Sperling: We have good evidence from the Mayo Clinic that the rates of acromial and scapular fractures are overall low and nearly equivalent with onlay and inlay designs. In a study of more than 3,400 primary reverse arthroplasties, the rate of acromial and scapular fractures was 1.6% with onlay and 1.8% with inlay. As noted previously, lateralization on the glenoid side has been shown to have inherent benefits. On the humeral side, newer technology, such as the use of offset trays, can allow the surgeon to fine tune and adjust the soft tissue tension and thereby minimize the risk of over-tensioning the shoulder (Figure).
Garrigues: For those of us who grew up in the reverse era, please take us back to 30 years ago. What was it like to be a shoulder surgeon without this powerful tool? How have things changed most?
Frankle: This is hard to remember because I have been using a reverse shoulder implant since 1997. However, when I review my utilization of RSA, it is clear that I am comfortable in selecting its utilization for multiple conditions such as acute fractures, asymmetric wear in osteoarthritis, revision surgery, posttraumatic arthritis and failed previous instability surgery, to name just a few.
Levine: We were forced to try “heroic” surgery like coracoacromial arch reconstruction or simply placing a hemiarthroplasty and managing a generation of unhappy patients. Glenohumeral fusion became a necessary procedure to have in your armamentarium due to the inability to dynamically stabilize the joint.
Boileau: Thirty years ago, we had only hemiarthroplasty for the treatment of cuff tear arthropathy. The RSA has been a revolution for surgeons and, more importantly, for patients.
Sperling: The reverse has dramatically improved the predictability we have to treat patients with nonrepairable rotator cuff tears in the setting of shoulder arthritis and failed arthroplasties. Moreover, it has helped us treat highly comminuted fractures in a more predictable manner compared to hemiarthroplasty. In the end, it is the predictability of treatment that has been the biggest impact of the reverse.
Garrigues: Few interventions have been as impactful as the Grammont reverse. What is “the next big thing”? What clinical problem in shoulder surgery is ripe for a new breakthrough?
Frankle: I believe the next big thing will be patient-specific modeling of the muscles that will allow us to predict how to optimize functional outcomes, as well as how we can ideally balance the joint to reduce prosthetic wear. Ideally, this type of analysis may even allow us to identify patients early in their disease process by identifying muscular imbalance and potentially altering the natural history of degenerative disease.
Levine: Failure rates of rotator cuff repair are too high, and patients are suffering due to our inability to reliably get the cuff to heal. Current strategies, devices, and biologic augments are not moving the needle fast enough or significantly enough, and there is tremendous opportunity still to impact significant change in the future.
Boileau: If I would know it, I would not tell it to you (I am kidding.). The next big thing is not the hardware, but the software development. Preoperative planning, mixed reality, robotic surgery and AI will allow us to improve our decision-making process and our results.
Sperling: The next big thing in shoulder arthroplasty will likely be the continued evolution of technology to improve the consistency that we have in placing the components in the correct position. This will be essential to help decrease the number of outlier cases and hopefully decrease the number of revision cases.
References:
Boileau P. Clin Orthop Relat Res. 2011; doi:10.1007/s11999-011-1959-y.
Colasanti CA, et al. J Shoulder Elbow Surg. 2023; doi:10.1016/j.jse.2022.10.015.
Grammont PM, et al. Orthopedics. 1993;doi:10.3928/0147-7447-199301-11.
Grammont, PM, et al. [In French] Etude et réalisationd’une nouvelle prothèsed’épaule. Rhumatologie. 1987;39:17-22.
Holliday C, et al. JSES Rev Rep Tech. 2022;doi:10.1016/j.xrrt.2022.10.006..
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