This paper reports the outcomes at a minimum of two years after implantation of the Simpliciti total shoulder arthroplasty system (Wright Medical, formerly Tornier) as part of a U.S. Food and Drug Administration (FDA) Investigational Device Exemption trial. The purpose of this multicenter industry-sponsored study was to demonstrate safety and outcome equivalence of the Simpliciti canal-sparing humeral implant when compared with preexisting data on a standard stemmed implant. The prospectively collected data from this study were likely utilized in an application for FDA approval for use of this particular implant in the U.S. Consequently, this study has had an impact beyond its scientific merit, as it formed the basis for the first canal-sparing (stemless) implant system approved for use in the U.S. in March 2015. Globally, this is not new technology, as stemless implants have been available in Europe since 2004 and in Canada since 2007.

In my opinion, the introduction of canal-sparing implants has been an advance in shoulder arthroplasty. These implants are theoretically associated with decreased surgical times, less blood loss, bone preservation, and a lower risk of intraoperative and potentially postoperative periprosthetic fractures. Additionally, canal-sparing implants are well suited for posttraumatic joint reconstruction when sclerotic bone and associated canal deformities would make insertion of a stemmed implant more difficult. A major advantage of canal-sparing implants is the ease of explantation during revision. In many cases, after removal of a canal-sparing implant, revision surgery can be performed using standard-length primary implants.

Canal-sparing devices also have disadvantages. They may be inappropriate for patients with poor bone quality, metaphyseal cysts, osteopenia, osteoporosis, or other types of metabolic bone disease. Unfortunately, there is no objective preoperative or intraoperative measure of metaphyseal bone quality to assist in determining if a patient is a candidate for a canal-sparing humeral implant. Presently, the intraoperative indicators of suitable bone quality are subjective, and include the “thumb test” described in the article. Additional studies are needed to determine an objective metric for acceptable bone quality.

The authors of this study provided good prospective evidence that the Simpliciti canal-sparing system is safe and effective in the short term. However, the future results are unknown, as they are with all new devices. Canal-sparing implants must be subjected to ongoing long-term assessment for bone remodeling/stress shielding, survivorship, and modes of failure.

The strengths of this paper include its prospective design, the FDA-approved protocol, and its multicenter enrollment. However, this paper must also be judged on its limitations, the most evident being that it was industry-sponsored without blinded or independent evaluators. Nonetheless, the authors should be commended for their prospective study, as should the FDA for approving canal-sparing implants for general use, so that American patients may benefit from this newer technology.