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.

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